Detecting pressure waves from the Tonga Eruption (2022/01/15)

On January 15th 2022 at 15:10 AEDT (04:10 GMT) theΒ Hunga Tonga Hunga Ha’apai underwater volcano near Tonga erupted. Hunga Tonga-Hunga Ha’apai is 1.8 kilometres tall and 20 kilometres wide, but most of it is underwater, with the top 100 metres visible above sea level. The pressure wave generated by the explosion blasted through the atmosphere atΒ more than 1000 kilometres per hour.

Dave mentioned to me that the people had registered a pressure increase on their monitoring devices due to the pressure wave and checking the internet the Met Office has issued a nice graph on Twitter.

On the observatory Grafana dashboard I could indeed see two pressure waves at the correct time. We only record the pressure every 60 seconds because for astronomy that’s all we need so we do not have the resolution of others but the height of the two events are in the correct range compared to the graph above.

Double pressure wave

The first pressure wave arrived (19:13-19:24) we was 2hPa increase as we have lost some resolution due to sampling period and the Met Office is ~2.5 hPa. We could change the sampling to be lower (15 or 30 secs) as storage is not an issue and then we would have caught a nice defined peak. The second pressure wave (2022/1/16 01:55-2:14) and we measured ~1hPa drop and again was lower than the Met Office due to our sampling period.

Our auxiliary pressure monitoring install was down during this period as the box appeared to have been restarted/rebooted and the ASCOM Alpaca instance was not running which was unfortunate πŸ™

Viewing Report 1st June 2021 – IMT3b

20:37 – 03:15

Setting up

I will start by completing the TPoint run tonight before moving on to calibrate the guider and make sure I can get and image. So by 10:30pm it was just on the border of being dark enough to take and plate solve the first image and continue the TPoint session.

So by 11:30pm I had finished the 212 TPoint model.

212 TPoints

The next thing was to do a Supermodel on the data. This reduced the error pointing from 500 & 23.7 arcsecs to 100 & 19.


Now connected camera to SGP and running autofocus on a mag 6 star, new focus position for Luminance is 18,312 at 00:13

New focus position

I then setup OpenPHD2 to guide and here I hit a problem. The guider did not move the mount. I have not got a guider cable attached as I do not want to do Pulse Guiding. Instead I always do Direct Guiding. So I looked at the settings in PHD2 and the mount was not set. So I went and searched my blog and I need to select the ASCOM Telescope Driver for TheySky. However it is not in the dropdown list.

ASCOM Telescope Driver for TheSky

Finally after a lot of head scratching I remember GingerGeek removed ASCOM and upgraded when I moved house. He had inadvertently removed the said driver and forgot to reinstall. I went to the ASCOM webpage, found the driver which took me to the Bisque website and downloaded. I then installed, restarted TheSkyX using PHD2 after I had restarted PHD2, I selected the said driver in the Mount dropdown and connected. This then moves the mount when I calibrate and subsequently guide. Fortunately I found all these answers on my blog posts from last year when I had setup the guiding originally.

Finally guiding

Now all of this is working it is rapidly approaching the time when the sky brightens, so it is already after 1am. I slewed to M14 using TSX, performed a Closed Loop Slew with the camera connected to TSX initially. Once I confirmed the object was in the centre of the FoV, I then disconnected the camera from TSX and reconnected to SGP.


Guiding started, all started to work well. A couple of snags, focus position was wrong in the filter setup so I need to change. Tries to autofocus on start of sequence so I need to change that. I then decided to grab 1, 2 and 5 min subs of LRGB to determine the best exposure. However half way through and some localised cloud rolled in and stopped the session.


The good thing its the closed loop slew is working well in TSX.

So with the local cloud still causing issues to the South, I slewed North East to another Messier target on my list, M29. Once again I setup 1,2 and 5 min exposures across LRGB to see which would be best. All the imaging tonight for Globular Clusters and Open Clusters was done at Gain 10 Offset 10.

M29 test 2mins Red

I manage to get frames and then I was afflicted by the same cloud. So instead I packed up and called it a night.

Viewing Report 31st May 2021 – IMT3b

19:25 – 03:28

Bob came over again tonight which is great company. He setup his Skywatcher AZ-GTI portable mount with his Tak FS60 on it so we could do visual throughout the night on a goto mount along with my star hoping through the 100mm binos.

Skywatcher AZ-GTI

I started the evening whilst light, measuring for the replacement T2 (M42) adapter for the camera train. Given the 0.083 microns per movement of the FLI Atlas focuser I need to reduce the image train length by 3mm. So the new adapter needs to be 31mm, current M42 adapter is 35mm. Meanwhile my AstroCat Fluffy decided to get some more sleep before dark.

Fluffy taking a hard earned nap

Next up was writing the Lat Long on the dome so I can give it to anyone that visits. With that done I started testing the rotation of the dome to make sure the dome no longer slips since I put the anti-slip tape around the edge. After spending some 15mins rotating the dome it seemed ok, it would be fully tested later when I redo the Tpoint model. This is due to the 2.1 arc minutes of error in my azimuth polar alignment that needs adjusting by 4.2 tics.

I adjusted the mount as above and ran a 20 point model. This told me the error int he azimuth was less than 1 arc min and that there was no need to adjust the mount any further, however it had low confidence. So now I will run a full 212 Tpoint model to see what it reports.

212 TPoint Model map

On starting the run I hit another problem, the mount hung and beeped. This was due to a balance problem on the tube which is weird as I thought it was fine. However maybe I had not rebalanced since adding the rotator properly. I removed a little weight at the front of the OTA and shifted it backward. I then tried again but again it hung and beeped. It transpired to be the same loose cale I had before, the focuser cable which had come loose. I applied some more white electrical tape to hold it in until I get round to changing the 2.1mm adapter.

At 23:40 I started a new TPoint run and am now 7 stars in and all is well. That did not last for long, around 47 Tpoints and I kept getting blank images. It seems the dome had lost its position. The Home sensor does not seem to be registering. I slewed the dome manually to Home at 123 degrees and synced that back into the dome controller. Starting the TPoint again resumed stars being seen.

Meanwhile Bob was moving from object to object without the AZ-GTI mount. M5, M57, M10, M12 along the way. We easily split Albeiro although Bob was slightly worried about my eyesight as I initially struggled. We saw the head of Scorpius pop up above the tree line but we didn’t get M4 from the IMT Plateau and Antares only just made it above the tree line. So I decided to relocate my bins to another spot in the garden by the Sun Plateau so we got M4 through them. M17 was seen through he 100mm binos also, looking remarkably like a Swan! Finally as it got light just after 3am we nabbed Saturn, Jupiter and the Moon.

We could see the star HD 200329 and Titan along with Saturn

By the end of the night I was at 187 TPoints so not enough for me to be confident the whole sky was mapped, nor enough to fix the model and have Protrack running. I will continue the mapping when dark tomorrow night.

Viewing Report 30th May 2021 – IMT3b

19:30 – 03:19

GingerGeek came for a visit with his kit for a night observing.

Ioptron CEM60, FSQ85, QHY OAG, SX Lodestar, QHY268C CMOS, Pegasus UPBv1

So whilst he sets up I have been testing the rotation of the dome as it still jams. After some testing I now believe the only fix is to find some grip tape that will add as friction to the inside of the dome between the dome itself and the thruster wheel. I have found some anti-slip tape on Screwfix which is 50mm wide and 18M long for Β£10, which will do the trick.

New Anti-Slip tape

Just watched the ISS go over, first time for GingerGeek. Videoed it using the iPhone 8 and it came out great. Also have the lovely noise of an owl in the background.

ISS passes overhead

Started Tpoint at 11pm. Used 30 second exposures and image scale of 0.33 arc/pix. I am performing a 212 point Tpoint model.

Tpointing near a globular cluster

Well TPoint model complete, of course I forgot to initially do around 25 TPoints, adjust the polar alignment which is our in Azimuth by 2.1 arcmins and then rerun.

TPoint results

Meanwhile before we finished I ran one of GingerGeeks M13 images through PI as a single frame from his new camera.

M13 from GingerGeek (60 seconds, Mode0, Gain 0, Offset 30)

Started to pack up at 3:19am

Viewing Report 29th May 2021 – IMT3b

20:30 – 01:30

What a glorious day

Another long pause between observations, after what seems like 3-4 weeks if not 1-2 months of storms, gales force winds and rain. However, tonight Bob came over and now that I have the new rotator installed with the new adapters I could use the 12″.

Ready for darkness

We setup under clear, warm and light skies. For the first time we put a couple of chairs and table down by the IMT3b. Bob helped setup the 6″ dob and the 100mm binos. We opened the dome and awaited darkness.

100mm Binos

I wanted to make sure that the rotator worked well, that the Field of View, FoV, worked within TSX and that I setup a small amount of Points on the scope. We also decided to see if we could visually see the Intellsat satellites and that I could track on them with the 12″.

Whilst waiting for darkness, Bob found what looked like a planet rising in the East, however it turned out to be Vega. We noticed in the corner of the IMT area by the IMT shed that you could see not only Polaris, now the Sycamore had been removed, but also low in the East and thus Vega at +11Β° altitude.

Bob then spotted Polaris first! Amazing! I normally find stars first, especially Polaris. However given Bob was in my garden and unfamiliar with the his bearings it was astounding he found Polaris so quickly. Well done keen eyed Bob πŸ™‚

Soon darkness fell and we pointed the binos and scopes towards Intelsat. It became apparent quickly that we were not going to be able to eyeball it due to not having a good enough understanding of the surrounding star field. Meanwhile on the 12″ we slewed and quickly found the satellites. We then use the rotator to move the FoV so that we could fit 4 satellites on the chip which was pretty cool.

Intelsat and Thor satellites

We then star hopped to M5 with the bins, then with the 6″ and finally with the 12″. The view through he 100mm binos was of course fantastic, fair superior to the 6″ dob. The image through the 12″ showed a dense star field.

I then set about collecting a half dozen Tpoints just to make sure that objects we in the FoV, however the first slew proved the polar alignment was good enough to do this. I produced a small TPoint model and stuck to that for now. I will need to go out later this week and perform a much longer automated TPoint. For that I need to fix the dome this is currently jamming.

We then sorted the rotator out, making sure the angle and FoV represented in TSX was correct. After changing the x and y values for the FoV indicator it worked perfectly.

About midnight we saw the best fireball ever cross in towards South East just below Arcturus. It was very orange and stunning.

After then slewing the 12″ to M81 to make sure the rotator reflected what we actually wanted to see, Bob and I called it a night. The Moon was due to rise shortly.

A good night for us and welcome after the rain and a harsh Covid-19 lockdown.

FSQ85 Flattener & QHY286C CMOS

I’ve taken the plunge and dipped my toe into the CMOS world. Since I didn’t have any OSC experience I chatted with DSW (has a QHY186c) and decided on the QHY286C. This I purchased from Bern at ModernAstronomy who has always provided excellent service.

The issue with APS-C sensors when coupled with the Takahashi FSQ85 is that the edges start to show signs of star elongation, I already see this on my Atik460. This can be corrected with the FSQ-85 flattener (ordered from FirstLightOptics) which has the effect of slightly increasing the focal length but also reduces the back focus from the native 197.5mm to 56mm.

Effective Focal Length455mm (f/5.4)
Image Circle Diameter44mm
Metal Back Focus56mm
FSQ-85 EDX with Flattener 1.01x

This means that I can’t use my existing Atik OAG->Atik EFW2 and Atik460 because it’s total distance is 59mm (22mm+24mm+13mm) so it’s out by 2mm even once you include the filter effect on the back focus. Note – This is also true for my Starlight Xpress configuration.

I do not understand why Atik could not have got to within the 55-56mm range by shaving off a mm here and there πŸ™ I may need to replace all Atik gear when I convert to mono CMOS or replace the OAG with a guide scope.

So onto the QHY268C, the OSC CMOS unfortunately has a CAA tilt adapter instead of a direct thread connection. This wastes 11mm of precious back focus giving a total distance of 23.5mm whereas the recently released QHY286M CMOS has a 12.5mm back focus !!!!

Also the QHY268C does not have an IR/UV cut filter in place so you need to buy an additional filter and holder and add that to the cost and factor in the adapter and distance needed …. I’m starting to regret this purchase more and more !

Source –

Back to the Takahashi Flattener (TKA37852), the back focus is 56.2mm but we add on the filter thickness as it changes the light path (2mm/3=0.66mm) so ~57mm (56.9mm), the imaging train is as follows :

Distance (mm)Accumulated Distance (mm)Connector
OU03122M54(M) -> M54(M)
QHY 02077046M54(F)
QHY Spacers14.420.4screw
QHY OAG-M1030.4screw
QHY 0200552.532.9screw
inc filter0.633.5
QHY CAA adapter639.5screw
QHY268C CMOS17.557screw
FSQ85 Flattener to QHY268C imaging train

The combined weight is 1365g so I may need to adjust the balance of the scope a little as it heavier than my Atik460/EFW2/OAG setup at 1080g.

Completed – Imaging train ready for first light

I may have to adjust the spacers a little but I won’t know until I have received a 2-inch Optolong L-Pro light pollution filter which is currently on back order from FLO.

Transmission chart for Optolong L-Pro


The recently released mono version of the QHY268 looks like it has a proper screw face plate with a more acceptable back focus of 12.5mm. This is more reasonable and would allow me to couple a filter wheel and OAG as well not requiring a IR/UV cut filter.

Like SyedT on StarGazersLounge I could go back to using a guide scope and ditch the OAG and then the imaging train could incorporate a rotator :

ComponentDistance (mm)
QHY268M CMOS12.5
M54 (M) to M54 (M) adapter2
Pegasus Falcon Rotator18
M54 extension ring5
M54 (M) to M54 (M)2
FSQ85 Flattener/QHY268M Imaging Train – Credit SyedT

I was thinking of a rotator for the remote Esprit120 which has a generous back focus of 76mm so I should have no problems there but that will be another adventure for the future !

Lakeside Focuser broken (23rd Jan)

So whilst Dave was in his garden using the binoculars and failing down holes in the process I was setting up to relearn how to take images ….. it’s been that long and the weather hasn’t helped.

So all was going well except that the Moon was bright and right near the winter nebulas. Even how bright the moon was I decided to use the time and practice using the Monkey Head Nebula as my target.

The tripod was levelled and the iOptron CEM60 polar aligned, the scope was balanced, the Atik460 CCD was cooled (-25℃), OpenPHD calibrated, the plate solver completed and the successfully sync’d and . The first step was to autofocus on a decent bright set of stars before the imaging run.

That was when the night was over ! SGPro set about running it’s autofocus but strange things were happening. SGPro was reporting that the LakeSide Astro focuser position was changing but the star HFR profile was not changing and the V curve remained flat. Since the focuser position was “changing” I did not think to go out into the garden with a red torch for an hour.

Upon inspection it was fairly obvious why it wasn’t working and inside the issue was proved to be a disconnected wire on the motor port.

Hmm …. I wonder what the issue could be !

I thought it would be prudent to double check which of the two spare connectors the wire came from and indeed it is the top one.

Source – Stargazers Lounge

Removing the heat shrink outer and you can see that there is barely any wire left since the majority of it was left in the solder when it broke off. This will require a wire extension and the old solder with the remains of the wire removed first before new solder being reapplied.

View of full cup connector with solder and empty cup connector

So since I’m really bad at soldering and I was worried about having to replace the whole unit (Β£90) I asked a friend who is fairly handy at this to perform the fix for me.

Optec Flip-Flat Service – Vendor Review

So during the ongoing Human Malware situation we have been concentrating on imaging asteroids, comets and more recently performing exoplanet measurements on the 12inch RC than long exposure deep sky astrophotography.

Astronomy is one those hobbies that is for most part is sole activity for the dark early hours of the morning and these days is usually done remotely. It was therefore disappointing that when one of the team went to use the Sky-Watcher Esprit 120ED for a night of astrophotography and found that he was unable to open the Optec Alnitak Flip-Flat. As the lockdown and travel restrictions progressed due to the initial wave of the human malware situation the issue was soon forgotten as we continued our focus to performing exoplanet observations on the 12inch RC for the ESA Ariel Mission.

Now that IMT3 has been decommissioned ready for it to be reborn as IMT3b at it’s new rural darker sky site I decided to take the opportunity to retrieve the FlipFlat and diagnose the issue at home on my desk.

Using the Alnitak controller software, I could hear the motor running but it never seemed to complete the close or open. All it continued to display was the TIMEDOUT message as shown below.

Timing out !

I sent an email off to the vendor I purchased it from but after a month I got no reply. In the hope I would not be left with an expensive paperweight I reached out to Optec. After quite a few weeks of getting no reply I was pleasantly surprised to receive a message from Jeff Dickerman (President) of Optec. Jeff apologised for not responding earlier and offered to help resolving the issue. The error message seemed to be a known issue and it was generally an easy resolution which required taking the box apart. Jeff sent me instructions on how to take the unit apart and fix the problem.

You’ll see the motor is attached to an internal wall with a modified shoulder screw and stack of Belleville washers.  These spring washers are used to allow the arm to slip when someone grabs the lamp and physically tries to force the cover closed.  Unfortunately they can also allow the arm to slip during an open or close operation which leads to that dreaded “TIMED OUT” message.  Optec have redesigned the stack a bit to eliminate this issue going forward. 

To correct, you might be able to adjust the washer stack by removing the lock nut and sliding off the washer stack to the pivot arm.  Check carefully to see if the shoulder screw protrudes beyond the pivot arm.  If so, rather than installing the cork washer next, install a 5/16” ID washer first to cover the exposed shoulder.  Next add the cork washer and stack of Belleville washers.  Finally screw the lock nut back in place and tighten while holding the shoulder screw near the motor (this is important to avoid breaking the internal motor gears).

Step 1 – Pry open clamshell
Step 2 – Shows what to secure
Step 3 – Tools needed
Step 4 –
Step 5 – Check shoulder visibility
Step 5a – Shoulder
Step 6 – Washer Stack

In the end I decided to courier the unit back to Optec for repair as I did not want to render my unit completely useless in case I made a mistake.

I’m extremely grateful to Jeff, Tina and the team at Optec for all there help, patience and understanding. I’m a very happy customer and the flip-flat will be rejoining the Esprit120 when the IMT relocation is complete at it’s new rural location. I can then do a Homer Simpson and annoy Dave with “Flap goes open, flap goes shut, flap goes open ……”

Exoplanet HD189733b (18-19/8/2020) – IMT3

Session period 21:00 – 23:57, transit start ~21:16 and end ~00:05

Started with Lum autofocus at 21:17 but on changing to the Red filter the HFR rose to 8.5 so refocused on Red at 21:20, position 60789, HFR 3.97 at 21℃. The change in HFR was more likely the warm sky and seeing conditions.

Restarted imaging at 21:39 at new Gain 10 and Offset 10 with a 15 second exposure to get the exposure down well below the 65k max to around 35k. The target star is a magnitude +7.69 so the initial Gain 139 Offset 21 and even Gain 75 Offset 12 were too high even at 10 seconds exposure.

We started with no delay in between the exposures until the start of the transit, then decided due to the large amount of data (35GB) being collected we should put a delay in which we did of 60 seconds. In hindsight we should be placed a smaller delay period in 15-30 seconds to allow us to gather more data points for the transit period. We have emailed the ESA team to start a conversation on planning exposure/delay settings for transits.

We then finished was forced to finish before the projected transit was completed when the clouds rolled in, and took Dark, Bias and Flats frame at Gain 10, Offset 10 ready for the analysis software.

After reviewing the data and the monitoring graphs it is obvious that the less than desirable Sky Temperature showed it was not truly clear. Below is the effect of high haze and cloud passing across the sky during our observation session. It should be noted that we have not had sky with a reading <= -18℃ since mid July.

Not a truly clear sky during the transit

How much impact this has on the observation and measurements we will discuss with the Exoplanet team.

Darkness Testing 20th June 2020 – IMT3

20:00 – 23:48

Tonight GingerGeek came over for a bit of social distancing friendly astronomy along with a bottle of Malbec wine. The idea was to calibrate the AAG, specifically when it goes from Very Bright to Light to Dark and at those points what the SQM value is along with the Sun’s position below the horizon. The AAG needs to get to 2100 which is dark, light is 5 and very light is 0.

The first time we noticed the values starting to change on the AAG brightness when it moved from its continuous reading throughout the day was at 21:47 when the Sun was -3.45 degrees below the horizon and the SQM was 10.15.

Within seconds the AAG read 9 and was already on Light vs Very Light and the Sun was now -3.54 degrees below the horizon and the SQM read 10.28.

It took almost half an hour for the AAG to get to dark. At 22:16 the AAG finally reached 2100, the SQM was at 13.97 and Sun was at -6.52 degrees below the horizon.

GingerGeek had also developed a new server for IMT3 to visualise some of the data from the observatory. The Grafana dashboard charts below show the data along with the Sun altitude.

New IMT3 Grafana dashboard

Looking at the last 24 hours shows the effect of the light nights on the SQM. The raised values after 4am went the value should be reducing or zero is the effect of a cat or bird covering the sensor. Also worthy of note is the sky temperature which shows the effect of cloud as the SkyTemperature increases. A truly clear sky would yield a value of -18℃ or better.

Shows the entire night

We also took darks on the ASC and applied them since we had never bothered to do it before. The shot below shows the before and after effect of applying the dark/bad pixel map. The whole image looks a lot cleaner and darker, although there seems to be some negative representation going on with dark pixels.

Before and after applying darks

The setting that needed to be changed in the ASC software took GingerGeek a while to find.

ASC Setting to apply darks

During the daytime the ASC looked awful but remote the darkframe reference file and just applying the badpixel map seem to be better. Tonight’s set of images will show if this is better or not.

The only other odd thing that happened tonight was the dome closed without the safety setting it off. Not sure why yet ……

Viewing Report 13th June 2020 – IMT3

23:31 – 04:02

So I opened the dome late this evening as it was not due to be clear. However an opening in the cloud meant I could test guiding again on the 12″, especially whilst it was light in the late Spring weeks.

The first job was as always to focus which brought me to a reading of 61944 at 19.83℃.

Focus run

Another small job was to sort the guider FoV out. I went ahead and used M92 to align the guider.

Aligning guider FoV using M92

The final FoV settings are here for completness.

FoV for guider

Set AS1600 to Gain and Offset 10 due to cluster being very bright and I needed to set a standard of 60 seconds minimum exposure. Gain 139 and Offset 21 gas saturated unless I selected 15 seconds, Gain 75 and Offset 12 saturated at 30 seconds so hence 10 and 10 which came in about 58k ADU.

I then performed a slew to a nearby star so I could centre the scope, there platsolve completed successfully and I updated TSX and the FoV for the 12″ with the new angle.


The first image of 60 seconds came down and was out of focus, I then realised changing the profile SGPro forgot the autofocus setting, so I had to stop the run, delete the images and set the original focus point then rerun.

M92 out of focus
M92 in focus

Next I ran a few images but then to my horror I had the same guiding issue, where the star moves being dragged up and down in a periodic way. I slewed elsewhere and tried again and the problem did not occur. I was near M92 and just East of the Meridian and quite high up. Not sure why that is a problem.

Near the Meridian

I could not resolve, I waited a while then performed a meridian flip and low and behold the problem went away, again not sure why. I still have this terrible noise coming from the RA motor/gear area. I decided to bite the bullet and take off various caps on the scope listening and looking inside. I decided it was not after all, the through the mount cabling but coming from the RA gear itself, so I looked for the MEII guide for removing the worm block and then followed the instructions to take off the RA cover.

RA gearing and belt noise

This gave me instant feedback on what the issue was, the belts driving the axis were making a noise. On looking through forums on I found a few people with similar issues and needing to grease the belts, they were told Lubriplate was a good grease. This is an American grease so I will find a similar here and then apply, I will ask Bob first for his suggestion.

So the night wore on and the LRGB frames of M92 I thought I would take whilst testing guiding progressed. At one point the imaging stopped due to cloud. I just caught the dome before it closed to change the safety sensor due to cloud. When it cleared it never really cleared, with the sky temperature reading about -14℃.

Not very clear

Nearing the end of the imaging session, I had caught about 15 frames of each of the filters.

Good guiding and imaging

The guider was behaving mostly with he odd funny jolt. By 3:30 am the sky was lightening very quickly.

3:30am and bright

By this time I had stopped guiding and imaging. I closed the dome, slewed the scope to the flat panel and proceeded to take a set of LRGB flats for Gain 10 Offset 0 and also Gain 139 and Offset 21 as request from the previous nights imaging.

Viewing Report 12th June 2020 – IMT3

22:09 – 02:02


It was unexpectedly clear this evening so I opened the dome late, so no cooling down.

Focus 60,279 Lum filter at 19.93℃

Autofocus run

Slewed to Arp 286 as I had seen on Flickr and wanted to see what it looked like in 12″. I noted I needed a new set of Darks for the Lodestar off axis guider after we had changed the driver recently, so I set about taking those with PHD2.

autoguider darks

The problem I then saw was no guide star in the FoV! I really need a rotator!!!!!

So I will image without the guider. The first image jumped as I realised the auto-guider was still on and trying to track nothing sending the mount this way and that. So I disabled and set about running 3 x LRGB for 300 seconds a piece

The first image was Luminance and looked ok, although bright due to high level cloud and no astronomical darkness this time of year. I also noted the mark on the filter caused by the LensPen! I won’t use that again. However I do expect that to come out with the flat so not too bothered. Also I could go clean it I just don’t want more dust on the filter so will leave until I have a reason to take the camera off again.

Arp 285 Luminance 300 seconds

For reference here is the luminance flat.

Luminance Flat showing Lenspen mark

Next up was Red filter for 300 seconds

Arp 286 Red 300 seconds

Then Green filter

Arp 286 Green 300 seconds

Then finally Blue filter.

Arp 286 Blue 300 seconds

So I left it to run for 3 x 300 seconds each filter. Meanwhile Mil Dave came online and opened his dome and we decided to go for a joint target to see how they compare. Given Arp 286 was below Dave’s hedge I mentioned the Coddington Nebula IC2574 which is actually a galaxy, being the object in my latest image from the travel rig with the Esprit120 and the comet passing. It has some interesting star clusters in it. We agreed on luminance and 300 seconds. Here is Dave’s result ….

Coddington Nebula by Mil Dave

Meanwhile the humidity kept rising

IMT3 environment gauges

At just gone midnight I finished the short run on Arp 286 and slewed to Coddington to catch up with Mil Dave. First I did a quick refocus as the temperature had dropped about 2℃ since I started.

refocus but note the point at 62,056

The refocus put me near but not near enough so I changed to 62,056 for a better HFR which worked. Then I went on to do Coddington and here is my result.

Coddington behind the tree from 12″

I had problems with unguided exposure, then had a problem finding a guide star, then the object was behind a tree!

So next I slewed to Mil Dave’s choice of object, here is Mil Dave’s image

Arp 214

I managed to find a guide star straight away and grabbed this

Arp 214

Notice my screen stretch is different hence the bright background. It is just a quick screen grab off the NUC. My turn to pick now, so went for several objects but all behind offending hedges at Mil Dave’s house. So I sent Dave off to choose one. He came back shortly with Arp 278. So off we set. Here is mine.

Arp 278

and of course Mil Daves….but no, he forgot to save it πŸ™

So my object next, I selected one nearby to save the rather long dome rotation I just did, and the resulting loud noise when it jammed! I need to look at that. Meanwhile Mil Dave trundled his round manually. So I choose NGC 7331, also known as C30 and Herschel H53-1, so also on my list for the Herschel 400. This is what I got.

NGC 7331 12″

Meanwhile the cloud from the South East started to creep in and my daughter, who just came in even at this hour of 1:36 said it was foggy outside.

ASC Cloud coming

Dave’s grabbed the NGC 7331 below.

NGC 7331 Mil Dave

I was about to suggest a Sharpless object when the clouds rolled in enough for me to shut the dome. It was reading -4.8℃ sky temperature and the limit was less than 30 for overcast, so I manual overrode.

ASC Clouds

Just before it shut this is the image I got of SH2-126 which is impossible to see since it probably needs the Ha filter rather than luminance.

SH2-126 300s 12″ Luminance

Well a good night all round, given we thought it was going to be cloudy it was nice to come out and play with Mil Dave and go hunting faint fuzzies, so a goodnight from me and a goodnight from him ?

Viewing Report 2nd June 2020 – IMT3

20:28 – 00:30

After a day of checking the mount and spending some 3 hours resetting the RA and DEC cam stop and spring plungers I have come out to see if I have resolved the image or made it worse. I can still hear the squeaking of the cables in the Through the mount position as the worm turns so I do need to remove 1 or 2 of them to free it up. However I no longer hear the knocking, tapping and grinding of the Dec axis. I am also going to capture some PEC data for Tom on the Software Bisque forum to look at. GingerGeek with his usual smoking jacket turned up to assist from a distance.

Whilst trying to find a star we came across a galaxy, NGC 5646 H126-1, which looked very interesting for the 12″, so we will come back and image that at a later date. We are in a rush for the clouds as it is to cloud over by 11:30pm. What we need to do is disable PEC, disable TPoint and Protrack and the guider relays then point at a star and guide without applying any corrections as per page 147 of the MEII manual for 15 minutes.

I went out to the dome and set with the help of GingerGeek the camera on the back of the 12″ to as close to 0 degrees as possible, in our case 0.81 degrees after plate solving.

We slewed to a start neat declination 0 and close to the Meridian on the East side of the mount called Tycho 326:747 and at 22:37 started to look at the auto-guider settings. The star was at DEC +01Β° 34′ 10.909″ and RA 14h 45m 20.1920. The auto-guider log in question for tonight was “Autoguider.018.log”. The star looked good in the main ZWO ASI1600mm camera which we would use to guide and collect the data. We did notice as per the image below over 15 minutes the star drifting East, so the polar alignment is out. More importantly we got the 15 minutes of data in the log as the clouds started to roll in, as can be seen in the star brightness below.

Autoguiding in TSX

The resulting log file was read into the Sky’s PEC and the raw data shown below one we clicked ‘Fit’ on the data which scales it to this chart. The peak to peak was 0.7 arcsecs. We applied this to the mount –

Raw PEC data from log
Fitted and applied PEC data

Next whilst GingerGeek went off to get his beauty sleep…..he really needs it πŸ™‚ I set about slewing to a bright star in the vicinity and calibrating the guider, since I had rotated the camera. The calibration was successful even though the RA looked slights odd as a fit. The different in the RA and Dec rate was potentially due to position on the sky and the error in the RA plotting data. I will go back and do another calibration next time it is clear.

Calibration in PHD2

I then slewed to M92, could not find a guide star very suitable so moved around a bit and then started to guide and see what the graph looked like. What surprised me was the the amplitude of the guiding was only 0.36 arcsecs which is really low and no guiding issues as I saw before. It looks like the adjustments to the spring plungers and cam stops may have been the cause and fix.

Guiding graph at +74 deg altitude and near M92

I performed a quick focus run whilst pausing the guiding and got 61836 and HFR 4.4 which is vert good for this scope.

Auto focus

Meanwhile the clouds from the North had started to drift in which was going to stop play πŸ™

All Sky Camera

I managed to get a single frame and focus on M92 of 20s before the clouds stopped the guiding. So I shut up the dome, sent the logs to Software Bisque, or the chap on the forum who was kind enough to help and went off to bed.

M92 20s sub

Viewing Report 1st June 2020 – IMT3

20:25 – 00:15

Dome once again open to cool down

Solved FoV for Lodestar guider on 12″

Now guiding on star to West side of mount around 0 degrees Dec and near the Meridian to see if problem reoccurs, graph looks ok but there is a slight regular pattern of error.

Slewed to M92 which is a glob currently at Alt +74, Dec 43 and on the East side of the mount where I had issues last night. I plate solved the image.

The auto focus run looked good

Found guide star by moving M92 slightly off centre. Now guiding. All looked good for a short while. So each section of PHD2 graph is 25 points, so when you have 100 points selected there are 4 sections of the graph. This mean each section/column represents own my case 250 seconds as I expose for 10 seconds, so just over 4 minutes per section. So the errors I saw last night were about 12mins apart. This cannot be the work gear as it has a cycle of 2min 29sec. This is from the latest Paramount manual for the MEII.

  • Tracking at the sidereal rate, one revolution of the worm takes 149.6 seconds (2 minutes 29 seconds).
  • The right ascension gear has 576 teeth.
  • The declination gear has 475 teeth.

The error I am seeing is about 4mins. I cannot continue imaging as every few frames are trailed.

Viewing Report 30th May 2020 – IMT3

5pm – 3:19am

I opened the dome at 5pm. I wanted to try tonight to sort guiding via PHD2 again on the 12″ this evening and then on Esprit120 if enough time allowed.

I changed the PHD2 Profile for 12″ from 6 calibration steps to 12. Performed calibration. Started test guiding in West at +47 Alt. Tried 300 seconds exposure x2 all good

I Slewed back to the East and to Pelican Nebula. Set the Reverse Dec Output After Meridian Flip tick box again ! It then re-calibrated for this side of the mount.

I have also changed the assume Dec orthogonal to the RA axis.

I reran the calibration a number of times until there was no longer an error at the end of the calibration. There was also trailing of stars. Some of the problem seems to have been an incorrect calibration, we need the RA and DEC rates to be very close indeed. Some of ours this evening were 1.5 arcsec difference. The good calibration we finally settled on was 0.5 arcsec difference. The other change was I went out and tightened up the grub screw holding the Lodestar guider on the prism tube that goes into the OAG body, this was loose and I could move the back end of the guider around. This was due to changing the OAG position recently and clearly not tightening the grub screw in enough.

Good calibration
Good guiding after good calibration

I then refocused on Lum and then switched to Ha. This is the image after 300s with a much better HFR of 5.21

Pelican 300s in focus with no trailed stars
Close up of stars from 300s image

When I had a bump in the seeing (assumed) the PHD2 graph looked like this

PHD2 graph bump in seeing

the resulting image of 300s I was in the middle of looked like this :

Image effected by seeing and bump in PHD2 graph

and zoomed in you can see the problem.

Trailed stars due to that seeing bump

Watching Chris Woodhouse’s excellent YouTube video on PHD2 guiding he has also set the min star size to stop it picking up a hot pixel, something we have seen this evening. He has also disabled Star Mass Detection, which stops PHD restarting if it if it thinks another star has been picked even though it may not have, both of these under the brain and guiding tab.

Settings before the change
Minimum star HFD and Star Mass Detection changes

It’s now 2:51am, the sky is brightening but the seeing has settled, the mount is behaving and I am taking 600s Ha images of the Pelican Nebula without any trailing of stars. The odd spike sees a jump up to 3 arcsecs occasionally.

600s Pelican in Ha with good guiding
Close up view of stars at 600s

The guiding graph below shows a really good small RMS below 1 which is key.

PHD good guiding below 1 RMS

So by 3:19am the sky is really getting bright and showing on the SQM as 18.6 and dropping fast. I have stopped guiding and imaging and will now head to bed. The final focus position for Ha was 59925 so I can grab flats tomorrow! I will then take a look at the Esprit120 tomorrow night.

Viewing Report 28th May 2020 – Travel Setup – Combe Gibbet

19:30 – 03:48

Combe Gibbet

Another visit to Combe Gibbet tonight with another astronomer, GingerGeek. After forcing him to leave the comfort and safety of his own home, where his girlfriend gives him tea, coffee and beer and with the luxury of mains electricity, he joined me at the very dark, very blustery sight near 1,000 ft up in the North Downs of Berkshire, formally Hampshire, they moved the line!

We left at 7:30pm and after the 50min trip arrived at the long road up to and past the Gibbet, which is really not much of a road at all.

Not a road, looking down the bottom part of the track

We drove carefully to the top, both parked our cars and set about setting up for the evening. GingerGeek had his Tak FSQ85 on his CEM 60 iOptron mount whilst I setup my usual array of large 4″ binoculars and at first the Mak 180 on the Paramount MyT. Later I would swap to the Esprit 120ED. To celebrate the outing, little geek had brought some beer πŸ™‚

Beer O’Clock!

The Sun soon started to set, the day trippers hung around to watch the sunset and then were gone. I started looking at the Moon through the Altair Astro binoculars which is just a wonderful sight. A Camera cannot capture the experience of seeing the Moon with its Earthshine and in full as the FoV is 1 degree in the binoculars was a wonderful framing.

Moon through binos taken afocal with iPhone 6sPlus

Next up was Venus before it sets, it is amazing just how bright it still is given its phase. I found in the binoculars eventually as it was hidden behind that cloud band in the distance. I then tried to get it in the Mak180, when a few new things happened. Firstly I could not slew to it as I had yet to polar align, so I had to place the scope in the right place. At the focal length of the Mak180, some 2.7m it is difficult to find something faint behind cloud just by pointing. I eventually gave up. I then noticed my laptop power had diminished by nearly 30% over about 20-25 minutes, this was due to Firecapture just hogging the USB bus capturing 100’s fps. So I was going to start the night short on juice! So I turned Firecapture off whilst I went to find Mercury in the binoculars.

Venus through 4″ binos taken afocal with iPhone 6sPlus

Mercury was a challenge, so much so I could not find it, I put that down to that not well placed cloud band. Meanwhile I pointed the Mak180 at the Moon to have a look, but by the time I had finished I the laptop was done to 53% !!!! Not so good.

So it was time to chat to GingerGeek (GG) before I put the Esprit 120 on the mount. GG was having lots of problems setting up. Firstly he had swapped the rings on the mount for the Tak that day and was struggling to balance the scope. It was so bad the scope kept dropping nose first then camera first and then either way depending on its orientation. Eventually, after much cursing, actually a lot of cursing, GG settled for the imbalance and continued to setup, unfortunately not before he knocked his beer over in his boot of the car ? fortunately I did not laugh too much ??

I went back to my setup, placed the Esprit on the mount and then set about getting focus with Ezcap, the software that comes with the ZWO camera. I do find the software very straight forwards and does what it says on the tin as it were. I then slewed to one of the open clusters I wanted to image and realised it resided in the North and that the twilight was still very much apparent so not suitable for imaging. Instead I settled for M51 high up as to the West was the Moon.

M51 300s Image uncalibrated

It is a lovely image at 5 minutes, I could see instantly at least 4 other galaxies and the colour of the main Messier galaxy was very pleasing. I look forward to processing the resulting subs. I set the timer for 1 hour (12x300secs) and went back off for veggie soup, cheese rolls, brownies and coffee that GG had kindly brought along.

crop of uncalibrated 300s M51

GG at this point was having issues focusing for his 5 minutes shot of the Pelican in Ha, he had made some other changes to the software before heading up the hill too which was confounding him. After some more time he finally had focus and started to image. However whilst a few of the images were okay, the resulting imbalance and gusts of wind made it difficult to keep pin sharp images. It should also be notes at this point that GG and I were running from the same car battery, although GG was only running the camera from it, the mount was running from his Lithium battery.

Stunning Pelican Nebula – 300s Ha uncalibrated

At just before 1am the inverter connected to the spare car battery turned off due to loading and power. Everything stopped for both of us ??? however GGs mount kept running due to the Lithium battery. I closed down my setup and allowed GG to reset his camera and reconnect, he then went on to start imaging, however the resulting image had moved significantly and GG decided to give up. So we spend the next 40 minutes packing up. Whilst this was going on we looked at Saturn and Jupiter through the binoculars which was a wonderful sight. Now for the 50 minute drive home to unload the car just before dawn, although by 2am it was clearly getting lighter.

Guiding graph on Esprit 120 Paramount MyT last night, all over the place with wind

The SQM for the site last night was 20.91 although the Moon was very bright. The site is also very dusty, and my laptop was covered in the morning. Another incident was that I inadvertently unscrewed the cover from the guider as I transferred from one scope to another and the glass cover fell out, I now have dust and dirt on the sensor to clean. It is not a great design by ZWO for the ASI290MC as it really needs a locking grub screw to top that happening or a reverse thread.

Herbig-Haro object at the end of the long feature can just be seen.

GGs image has set us on a little project to image the HH 555 bipolar jet at the end of the major turn of gas in the Pelican Nebula. We will attempt over the next few nights to get an image from both the Esprit 120 ED Pro from the IMT3 dome in Ha and also from the OS 12″ to see what it looks like compared to the Tak FSQ85. Another good social distancing astronomy session ? goodnight.

Dwarf Stands Guard At Dusk

Image Processing Notes for CMOS Using Flat Darks

I thought I ought to document this so that I remember this is now the new normal for making a flat master for my CMOS camera, the ZWO ASI1600MM. The problem I found again after not processing images for some time, was that the normal way of processing without Flat Darks produces a master flat with embossed, so raised doughnuts across the image.

Batchpreprocessing – > Darks tab -> Optimization Threshold -> move from 3 to 10 – > this removes the dark entirely and also removes the amp glow but introduces loads of noise so clearly not right at all. So I contacted my friend Dave Boddington who is a bit of an expert on this topic and he gave me some good advice that has of course worked.

So first let’s detail what I am calibrating. On the 20th April 2020 I took a set go Ha frames of M84, these were 300s exposure and with a Gain of 193 and I believe an Offset of 21, however we had some changes over the previous week so driver the Offset is no longer stored in the FITS header. It was when we were using the ZWO native driver. The temperature of the cooler was set to -26℃. I have 8 of these frames.

M94 300s light

I also have a set of 10 darks at the same settings. However when using the Statistics tool Dave noticed the Mean of the image was 800 and the Mean of the Ha frame was 353. This is in a 16 bit notation. The camera however is a 12 bit camera and this means the Mean for the dark is 50 and the Mean for the Ha is 22, so a difference of 28 in 12 bit and 447 in 16 bit. I will come back to this later.

Mean of Ha 300s light
Mean of Dark 300s

First I created a Master Dark for the Ha frames using the normal ImageIntegration settings. I did not calibrate darks with Bias as you do not need bias with a CMOS cooled camera. Next I created a Master Flat Dark for the Flat frames using the same ImageIntegration settings.

Single 300s Dark with hot pixels and amp glow

Then I found the Ha images did not need to have the flats applied so I skipped that step for the narrowband images. Next I Calibrated the Ha lights with ImageCalibration and because of that discrepancy above which looks like it was induced by having the Offset for the darks set to 12 and the Offset for the lights set to 21 I added 600 as suggested by Dave Boddington to the Output Pedestal in the Output files section of ImageCalibration. I made sure Evaluate Noise was ticked and that both Calibrate and Optimise were unticked in the Master Dark section. Master Bias was unticked and so was Master Flat for the narrow band images as mentioned.

Calibrating Ha lights with Master Dark

This created a clean set of calibrated Ha lights that did not require flats to be applied.

Calibrated 300s Ha light with Master Dark

Next I had some issues in Star Aligning the frames. The error I received was ‘Unable to find an initial set of putative star pair matches’, due to the frames being very sparsely filled with stars and the background being quite light compared to the stars. A quick look on the PI forum showed increasing the Noise Reduction in the Star Detection section from 0 to 4 sorted the issue, with all but 1 frame being aligned. I was then down to 7 x 300s Ha lights. The final frame was very light due to cloud.

7 x 300s Ha Calibrated with Darks, Aligned and stacked

I then integrated these 7 frames together. I had a challenge with trying to get the hot pixels in a few areas to disappear using Cosmetic Correction and pixel rejection during stacking so I will remove these after by hand before combining into the larger set

hot pixels not removed

So in essence what I have learnt is that I need to have really clean filters and camera glass. That all the doughnuts are on the those surfaces and not anywhere else. That the flats must be between 22k and 26k for the CMOS cameras, although this has some tolerance either way. That I need to set the camera to the right Gain, Offset and Temp as the lights and that I need the right flats for the right lights!

Calibration of AAG Weather Station – IMT3

Today has been wet, windy and cloudy, which for once is a blessing! Why I hear you ask? Well simply put, to calibrate the hell out of the AAG one needs inclement weather and today has provided that in spades πŸ™‚

So after monitoring the AAG all day here are the final settings. I have changed the limits for the wind only today, but I have extended the time period for the graph from 10mins to 1 hour. The wind has recorded over 1.1 m/s which may not seem a lot but at times has blown garden furniture around and the bins.

New Limit setting for AAG
Very windy today πŸ™‚

AllSkyEye – Pro

So for a short period of time we had settled on using AllSkyEye. Recently we noticed that the author had issued a Kerogram and stretched horizon generate of the latest image but only available in a new Pro Edition.

The Pro edition was only Β£20 for a 3 user license, the author gives this purchase as a donation to the charity of his choice – good man ! So now we have AllSkyEye Pro in use at the IMT2 and IMT3 domes.

Latest Image with custom text overlays
Latest Image Horizon Projection

A Keogram is an image composed of slices taken from images in a sequential time order.The slices (which are always taken from the same location and with the same shape) are stitched together to form an image displaying a timeline of the selected part of the image as shown below.


We still have the dark map to take to remove the hot pixels from the image but at the moment it gives us a nice view remotely before we decide to open the dome – that’s if the AAG Cloudwatcher limits agree and it thinks it’s safe to do so of course !

Bob noticed we had our local security guard aka Fluffy watching over his night’s imaging and turning to watch an ISS pass.

Fluffy stands guard at the weather station as the ISS passes over