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™

PixInsight – Load Default Project/Process Icons

So whilst Dave was processing our M45 QHY268C data, he mentioned how it is frustrating that he has to reload his process icons for his workflow every single time.

After finishing the communications/process diagram for IMT I decided to have a quick look if it was possible. Watching PixInsight startup I noticed access to a few files – banner and startup.scp. For me these were located in the C:\Program Files\PixInsight\etc\startup directory.

Looking through the documentation it seemed possible to add statements to the file which was possible once I had modified it as Administrator.

Method 1 – Load Process Icons

This will load just the process icons into the current workspace on startup. Add the line below to the bottom of C:\Program Files\PixInsight\etc\startup\startup.scp :

open "C:\Users\gingergeek\Pixinsight\Pixinsight DSW Process Icons V10.1.6.xpsm"

Save the file and restart pixinsight.

Method 2 – Load An Empty Project With Process Icons

Another method (preferred) is to create a new project (Empty-process-icons.pxiproject), load in the process icons. Save the project and then change the properties to make it read-only so you can’t accidentally overwrite it later on.

Add the line below to the bottom of C:\Program Files\PixInsight\etc\startup\startup.scp :

open "C:\Users\gingergeek\Pixinsight\Empty-process-icons.pxiproject"

Save the file and restart pixinsight.

I also modified the banner file (in the same directory as startup.scp) so it would show the IMT3b designation. I generator the ASCII art from one of the many online sites, if I can remember which one I will link it here.

\x1b[1;38;2;255;000;000mβ–ˆβ–ˆβ•—β–ˆβ–ˆβ–ˆβ•— β–ˆβ–ˆβ–ˆβ•—β–ˆβ–ˆβ–ˆβ–ˆβ–ˆβ–ˆβ–ˆβ–ˆβ•—β–ˆβ–ˆβ–ˆβ–ˆβ–ˆβ–ˆβ•— β–ˆβ–ˆβ•—\x1b[39;21m
\x1b[1;38;2;230;000;000mβ–ˆβ–ˆβ•‘β–ˆβ–ˆβ–ˆβ–ˆβ•— β–ˆβ–ˆβ–ˆβ–ˆβ•‘β•šβ•β•β–ˆβ–ˆβ•”β•β•β•β•šβ•β•β•β•β–ˆβ–ˆβ•—β–ˆβ–ˆβ•‘\x1b[39;21m
\x1b[1;38;2;204;000;102mβ–ˆβ–ˆβ•‘β–ˆβ–ˆβ•”β–ˆβ–ˆβ–ˆβ–ˆβ•”β–ˆβ–ˆβ•‘ β–ˆβ–ˆβ•‘ β–ˆβ–ˆβ–ˆβ–ˆβ–ˆβ•”β•β–ˆβ–ˆβ–ˆβ–ˆβ–ˆβ–ˆβ•—\x1b[39;21m
\x1b[1;38;2;179;000;153mβ–ˆβ–ˆβ•‘β–ˆβ–ˆβ•‘β•šβ–ˆβ–ˆβ•”β•β–ˆβ–ˆβ•‘ β–ˆβ–ˆβ•‘ β•šβ•β•β•β–ˆβ–ˆβ•—β–ˆβ–ˆβ•”β•β•β–ˆβ–ˆβ•—\x1b[39;21m
\x1b[1;38;2;153;000;204mβ–ˆβ–ˆβ•‘β–ˆβ–ˆβ•‘ β•šβ•β• β–ˆβ–ˆβ•‘ β–ˆβ–ˆβ•‘ β–ˆβ–ˆβ–ˆβ–ˆβ–ˆβ–ˆβ•”β•β–ˆβ–ˆβ–ˆβ–ˆβ–ˆβ–ˆβ•”β•\x1b[39;21m
\x1b[1;38;2;128;000;255mβ•šβ•β•β•šβ•β• β•šβ•β• β•šβ•β• β•šβ•β•β•β•β•β• β•šβ•β•β•β•β•β•\x1b[39;21m
Our new PixInsight default project with process icons


The downside to both these methods is that if PixInsight is upgraded/reinstalled then you will lose the settings – not a disaster to be honest as they are easy to put back into place.

Processed Image (M45)

So visiting Dave one evening as we have not met for a while whilst I was updating software Dave processed the QHY268C data we took of M45.

M45 – PixInsight Processed Image

So I’m disappointed that although the image is a good first start I forgot to change the change setting on the gain which in SGPro is in the event settings and not in the top level sequence display πŸ™

Dave ran the image through the annotate function of PixInsight. The galaxy PGC13696 near the bottom of the image is actually 232 million light years away.

M45 – PixInsight Annotated Image

Viewing Report 10/11th December 2021

Unusually it was a clear Friday evening. I did plan to be ready to go as soon at the pole star was visible but my imaging PC insisted on updates and the local hard disk was running at 10MB/s (replacement SSD on the way).

By the time I was ready, mount setup, polar aligned and balanced it was already late. I decided not to use the latest SGPro or NINA beta but just use the existing SGPro version. I was delayed starting as I was having issues with SGPro hanging when it couldn’t talk to the SQM (ASCOM Conditions Observing Hub) on a previous COM port, I need to report this back to the devs as a bug.

At this point Peg-Leg Dave joined me on a video call and we discussed imaging M45 in different modes on the QHY268C OSC. So we moved the scope to Alp Ari and proceeded to plate solve in SGPro, sync’d the scope Cartes Du Ciel and calibrated OpenPHD2.

Using the SGPro framing and mosaic wizard to decide on the framing for the target sequence I wanted as much of the reflection nebula as possible rather than being dead center.

M45 – SGPro Framing Wizard (FSQ85/QHY268C)

I’ve used the multi-star guiding in OpenPHD2 since it was first released in an earlier beta and I know Dave is looking forward to using it when he moves from using an OAG on his 12-inch RC to a 90mm guide scope to make it easier to get more guide stars or even one star.

Multi-Star Guiding in OpenPHD2

Whilst trying some mode/exposure tests the guiding started acting up in RA, so parking the mount and disengaging the clutches I redid the balance of the scope. It was only marginally off but it was enough to cause issues for the CEM60 …. it is not forgiving !

We decided to increase the Gain/Offset to 15/75 and use the Extended Full-Well mode (#2) of the QHY268C, testing the star brightness levels of various exposure times we opted for 180 seconds as that was under the maximum brightness level.

As I currently have no IP camera outside I like to see the mount position using GSPoint3D as I like to view where it is especially during meridian flips. NINA has this built-in now in the recent version 2.0 betas. As SGPro lacks this functionality I can use the view via this is standalone version that connects to the ASCOM mount.

Mount/Telescope virtual view
M45 – Pre Meridian Flip

SGPro paused the guiding just prior to the meridian flip. Following the automated flip, the guider and the imaging sequence automatically restarted after a plate solve and auto centering were performed.

Inverted shot of M45 (180s) – Post Meridian Flip

It gradually got cloudier just after midnight and the quality of the subs declined so I decided to stop acquiring data even though we really wanted over 4 hours of exposure.

I proceeded to take calibration frames. Using a target ADU of ~23,000 the SGPro flat wizard on the Pegasus FlatMaster (100%) gave an exposure time of 9.68s for the Optolong L-Pro filter, 25 flat-frames were taken followed by 25 dark-flat frames of the same exposure time and finally 25 dark frames of 180 seconds.

It was at this point that I realised that the FITs header showed a gain level of 0 and not 15, the offset was correct but I can’t be sure if the EFW mode was used as it’s not in the FITs headers. Only when using the native driver in NINA can you set the mode within the sequence, in SGPro the mode is set in the external ASCOM driver when the camera is not active in SGPro even though though it’s in the ASCOM API as the Camera.ReadoutModes property.

Also for some reason the default setting in the QHY driver is to NOT disable the overscan area which means I have black borders on my images which will make processing the data in Pixinsight a challenge !

I actually got to bed after 3am even though I had planned to stay up until the dawn. Next morning I noticed that my counter-weight had slipped and rotated on the bar. This may have also caused some of the issues with the guiding so I need to set-up earlier and check things more thoroughly in future to avoid these mistakes.

So although it’s not the data we planned it will be worth processing over a wine. The evening was a really a useful experiment and hopefully lessons will be learned …. if I remember the next time.

Viewing Report 24th August 2021 – IMT3b

21:22 – 03:50

Another clear night whilst I am on holiday and after a long day of building the new warm room for my astronomy hobby. I finally got the camera imaging some more 600s Ha frames of the Sharpless 132 emission nebula in Cepheus (11 subs). The challenge was SGPro misbehaving and not plate solving. I used Gingergeek to look at it but he could not work out the problem either. So I used TSX to slew and solve instead before heading back into SGPro to start capturing data. I ran a set of Ha Flats before I moved to the next object at Rotator Angle 256.020, focus position 18500.

I then moved to SH2 183 another emission nebula in Cepheus. I let this running for the rest of the night whilst I went to bed at 00:47 during which time it took 19 images until more cloud lost the guide star which I need to fix so it restarts automatically.

I also worked out that plate solving was an SGPro bug as restarting SGPro allowed the plate solving to start working again, so useful for next time.

Observing conditions check. This morning I reviewed the environmental data and the conditions were fairly poor so I will redo the data. The Moon was just past full. The ASC video shows wispy cloud all night. The sky temperature was bumping around -13-14 degrees all night where -18 degrees is considered clear.

Jupiter/Saturn Conjunction Christmas Eve – 24th December 2020

The most funny thing about moving to a new house is assuming you have understood your horizons correctly, well at least I found it funny when I got it wrong. After several attempts to catch the conjunction, traveling out to a nearby field with low horizons, Christmas Eve was no difference. I had set off, this time with the Esprit 120 and QHY168C and on arriving at the location realising that the weather was too cloudy to grab the conjunction.

So off I went back home. I decided to wonder up the garden to see if the weather had cleared when I returned, to find that not only was there a gap on the clouds, but also I could see Jupiter !!! This meant only one thing, that my South West horizon was not +15 degrees but actually +4 degrees! Wow that is good and lucky.

View South West , observatory is going to be in front of the foreground trees

I ran back to the car and started hauling the travel scope to the building site of IMT3b which is currently a vegetable patch, this is around 200 feet away from the car part way down the garden. It took 5 trips to move all the equipment, good for my Apple watch exercise rings, not so good for the setting of the conjunction of Jupiter and Saturn. By the time I setup and slewed the telescope round the pair were setting behind the ancient forest in the distance but I managed to snap a single image! Perfect.

Jupiter and Galilean Moons with Saturn below – 120 Esprit and QHY168C

Exoplanet HAT-P-32b (14/9/2020) – IMT3

So the evening started well, I had logged into IMT3, got the dome ready, TheSkyX/SGPro software was up and running, CMOS camera was cooled and I was already syncing on a bright star even though it was still twilight.

Dave and I had chatted the previous night and had settled on HAT-P-32b in the constellation of Andromeda. The reason was due to the target position in the sky, the time of rising and setting was before the rise of the sun so we could get a full ingress and egress and no meridian flip was required.

Then the gremlins started to play havoc with our efforts and I was having major issue with guiding to the point that I was going to give up as the issues were eating into the desired 1 hour egress monitoring time period. Dave joined the session to help resolve the issue and we managed to start imaging about 10 minutes before the start of the transit.

Dave had to go to bed due to work commitments but I was determined to get the full set of observation and run it through the HOPS analysis software. It was an uneventful night interspaced with music, movies and hot cups of tea.

Once I had transferred the data over the internet to my server, performed the analysis and sent the result to Dave it was 5:30am so I crawled into bed around 6am.

Detrended Model from HOPS software

Exoplanet WASP-74b (30-31/7/2020) – IMT3

Started around 21:15, Guiding by 22:02, Capture started 22:22, Finished at 03:31.

Dave and I are part of the amateur exoplanet monitoring effort for the ESA Ariel mission. We decided that we would allocate some time to try and provide observing data towards the project whenever we could.

Part of this requires some forward planning such as looking at the upcoming transit visible and their associated time. This is due to the altitude of the object, the ingress and the egress times of the projected transit.

Prior to this we had discussed in advance which object to target for the chosen evening. All the hard work of choosing objects is done by the Exospies project website as they list the candidates they need data for via a schedule. So it’s a simple task for use to go through the list and work out what fits best for us.

Unfortunately whilst opening the dome to cool down I decided to review the schedule but I was hit with a server 500 error from the website. In a panic that I might miss the start of the event I scoured the internet for alternate exoplanet transit time websites and found the excellent Exoplanet Transit Database of the Czech Astronomical Society.

WASP-74b Exoplanet Transit Times

Later on I found as well which will be useful in the future, especially for looking at past events.

WASP-74b – Target star is in the centre

I had issues with focus drift all night due to the temperature fluctuations but at a recent Zoom session it was discussed that images can be out of focus with no detrimental effect on the measurements :

SGPro Image History

I was unable to auto focus successfully maybe due to the low altitude and seeing. I also discovered that temperature compensation was enabled so we probably need to remeasure the temperature compensation coefficients so the focus deltas are better between the par focal filters.

The object was at a relative low altitude, the outside temperature was warm and although the skies appeared clear our AAG CloudWatcher sensors via the Grafana dashboard told a different story. For us a truly clear sky is anything equal or lower than -18℃.

Sky Temperature – it was clear but it wasn’t !
Sky Temperature – T’was warm !

After performing a meridian flip, resumed the guiding I started to feel tired so I set my alarm for 3am and went to bed. Unfortunately there appeared to be a guiding issue at some point shortly I went to bed.

Guiding issues shortly after meridian flip

This was investigated using the phdLogViewer and shown to be a loss of guide star and didn’t recover for around 18 minutes.

The guiding issue also caused the image to shift so the target and reference stars moved. We need this in frame in order to run the frames through the provided HOPs data analysis program which hopefully won’t have a problem in reading them. That’s an exercise for this weekend and hopefully we will have enough data to yield a decent light curve that we can submit.

Viewing Report 25th July 2020 – IMT3

21:47 – 00:23


GingerGeek and I were out imaging tonight. The sky unexpectedly cleared and we thought given the impending move of IMT3 to another site that we would try to gather some more data on M57, specifically LRGB and some additional Ha on the 12″.

We ran Autofocus on Luminance which gave 60,671 at 20.64℃ and HFR 6.5. We then started to image and after a few frames the temperature started to drop. In the main this is because we opened the dome last minute rather than a minimum of 2 hours before we used it so the dome was warm and now cooling down the optical train shifts.

M57 quick frame and focus

We refocused to 62,712 on luminance at 19.10 with an of HFR 5.15. We then ran the image acquisition and below is a screenshot of the guiding, which looked like it was going to cause an issue but it was ok. If it had then it would have been the local fog rather than anything on the mount. At midnight we performed a Meridian flip nice and early which afforded us to leave the observatory running and go to bed. Notice the graph below, the yellow line drops as we performed the meridian flip, this is due to the dome now shielding against next doors light !!!!!!!

Guiding ok, notice the drop in the graph

The neighbours light continue to be a pain as can be seen here, I really cannot wait to move the observatory to it’s new dark site.


Finally managed to capture LRGB and Ha, below the RGB and Ha frames can be seen in PI. Note the central star is not visible in the Ha frame,

RGB and Ha raw frames

Finally I stacked 1 of each colour without calibration to see what it would look like.

RGB quick single stack no calibration

So we left the observatory imaging, I had a quick peek outside around 12:30am and there was water running off the dome and the outside windows of the orangery! The Observatory ran until the dome shut at 3:58am (it woke me up) when the light levels started to rise.

Viewing Report 22nd July 2020 – IMT3

21:28 – 23:24

I opened the dome at 8:30pm and then went off to do some more work. A few calls later and it was time to come back and see if I could grab comet C/2020 F3 NEOWISE which had now moved further West and further in altitude over the past week, meaning it should be visible from the dome. Below is Arcturus as I performed a quick sync.


Below you can see Arcturus on The Sky X with the dome slit showing and the obstructions from the horizon also present.


Comet NEOWISE can be seen just above next doors tree.


A quick peek with the camera and I could just make out the comet.

Quick peek of the comet but clouds

Clearly more clouds rolled in which is typical

More clouds!

Looking at the cameras in the dome I could see the cloud bank of cloud (picture top right)

Cloud bank approaching

Fortunately the comet could be seen at the back of the cloud bank.

45 second exposure of Comet C/2020 F3 NEOWISE

So I set about quickly taking some images before the comet disappeared behind the tree.

90 second exposure of Comet C/2020 F3 NEOWISE

The other useful thing tonight was using the monitoring GingerGeek put together. Below are a selection of shots from the website.

IMT3 Conditions

The chart below shows the light cloud cover and the sky temperature is representative of the sky clarity and relates to cloud coverage too. The scale is inverted to -18℃ is a cloudless beautifully clear night sky, which tonight was not!

IMT Conditions Summary – Fisherprice style πŸ™‚

At least there was no rain πŸ™‚

IMT3 Rain Radar

This image below shows the cloud bank just North West of Reading that was a problem.

IMT3 Cloud Cover

This next chart is from the data produced by the AAG CloudWatcher weather station. Note the sky temperature is nowhere near the -18℃ to be clear.

IMT3 AAG Cloudwatcher weather station

And finally the all sky cam just as I packed up showing the clouds clearing

IMT3 All Sky Camera

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 31st May 2020 – IMT3

18:01 – 01:09

Opened dome early to cool down at 6pm.

The first thing to do were Flats for Ha first for the previous night but also for use tonight. I completed this at 22:15

At 22:31 I performed focus run on Luminance which came in at position 59841 with HFR 4.77.

I started an image run as soon as the Pelican Nebula (IC5067) was above the neighbours house. I have set a run of 10 x 600s and 20 x 300s Ha subs guided with the new PHD2 settings to prove the 12″ now works from 1 night to another. Then we can try the Esprit on the next clear night. The guiding at first looked okay.

Good initial guiding

The resulting image looked very good too

300s Ha guided Pelican
300s Ha guided zoomed no trailing
600s Ha Pelican guided
600s guided zoomed no trailing

After about 5 frames I suddenly ran into a problem the guiding looked like this

There were large movements in the Dec and the RA would not return to centre. Soon enough SGPro stopped imaging and tried to settle the guider and then further complained about not being able to settle. So I temporarily changed the Hysterisis from 10 to 15 to see if this would get the star back. It did, well just.

The RA axis returns to the centre after quite some time. Is this possibly seeing related or is there something mechanical amiss with the setup?

I did notice the problem one more and then went off to bed left it running 01:09 leaving the possible bump in the worm to resolve itself.

bump in the worm?

Addendum – So got up this morning and the scope had continued its travel across the heavens. I looked at SGPro and it finished the sequence without any problem. I then looked at PHD2 and expanded the time to include the maximum span possible as it had been trying to guide after loosing the star (I have check boxed Enable Star Mass Detection in the hope this fixes it) and I noticed a problem, which is the recurring South then North oscillation which I now need to investigate as that is the cause of loosing an image due to the star moving. It looks for all the world to be on the worm gear. I will set about measuring the PEC tonight and see if I can see it. It may of course be from when I adjusted the work due to another problem I had and it may not be quite right. I will also ask on the forum.

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 29th May 2020 – IMT3

21:05 -2:56am

Currently cooling dome since 8pm.

Dome open to cool down

Logged in at 22:43 to slew to Pelican IC 5067

Esprit 120 FHR was 1.99 for Lum and 2.54 on the Ha

Focused on Deneb , 30 seconds exposure produced HFR 2.23

Deneb – 30 seconds in Ha
Solve and Sync

Solve and sync completed on Deneb in Ha

The focus point for Ha was 6217

Now for a quick frame and focus, 30 seconds exposure

30 seconds Ha on Pelican as Frame and Focus test

That looked good, next up was to see if we can image for 5 minutes unguided and see what the resulting image looked like

300s Ha Pelican

Again the resulting image looked very good and no star trails

Clear skies with -18℃ measured by the Infrared sensor on the AAG Cloud-Watcher.

AAG Infrared sensor read -18c so zero clouds

I then tried a 10min image but got clear trailing.

Star trailing at 10 minute exposure

So I set the guiding up with PHD2, went out to the dome and created a dark library as this was not done. I then set about training the guider and then set it running, initially with a 4 second exposure. The resulting guide graph looked a bit bumpy. The ASC looked very clear this evening which was the first time in a while. You could see stars to the left hand edge of the image which is normally obscured by cloud.

ASC Clear skies

We decided to run the guiding assistant in PHD2 and see if there were any changes that needed to be made. It came up with some suggestions including redoing the calibration and changing the calibration step size from 1600 to allow more steps in the calibration, in this case I changed to 1200 to try and go from 3 steps per axis to 8, however I got to 6 steps and this seemed good enough. When I then reran the guiding assistant I no long got the error about calibration. I did have a few suggestions as seen below which I applied.

Guiding Assistant recommendations

So the changes made still have not allowed 10mins images, they are still trailed. So that I do not waste any further time this evening I captured 5 minute images instead of 10 minutes and I will relook at the guiding next week when the Moon get brigheter.

At 1:38 we gave up on guiding and switched to 12″, Autofocus on Lum, 63384 HFR 5.4. Took some 5 minute and a single 10 minute frame guided, scope trailing ?

There were three scopes on the Pelican Nebula (IC5070/IC5067) tonight as GingerGeek was imaging with the Tak FSQ85 from his back garden.

3 Different image scales from tonight

Finished to go to bed at 2:56 am, GingerGeek finished the session by taking flats, warming up the CCD and bringing the scope indoors just after 3am.

Rough stack of Ha (5nm) 10×600 seconds, -15℃ From the FSQ85
ASC and Summer Triangle

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

Viewing Report 15th May 2020 – IMT3

21:58 – 02:02

Just setting up for an imaging run and to test imaging without temp compensation to see if the 12″ keeps focus without it. I started by myself then was joining by GingerGeek and then Bob.

Performed a SGPro autofocus run on Mag 7 star produced focus position of 71,828 @ 4.6 HFR at 14.47℃.

1st autofocus run
Resulting M98 image from 1st autofocus run

The resulting image was good with good star shapes. Although I suspected at this point the seeing was not excellent.

I let the sequence run for a bit imaging M98 through LRGB and then decided the HFR was gradually getting larger so I performed a 2nd Autofocus run which came in at position 72,215 HFR 5.7 at 13.97℃.

Again I let the sequence continue for at least 4 images and the performed another Autofocus run, note all the time this was on M98 and not slewing away to another star. This came in at focus position 72,697 @HFR 5.7 at 13.82℃.

I continued this routine again and performed another Autofocus run on M98 focus position 73,441 HFR 5.4 at 12.98℃.

I then decided, due to struggling to get a good HFR on focus runs to see if the autofocus was introducing an issue so I changed the autofocus setting from 9 data points to 11 data points to try and get fuller deeper curve. The resulting curve was better and more complete on both sides of the U shape. I then imaged further and then attempted an autofocus with the settings change for the step size from 2500 to 1500 and data points from 11 to 15. This was because I felt we always have a flatfish bottom to the autofocus which at this focal length of 2.5m shows the quality of the seeing with a narrower flat bottom being better seeing. The new autofocus came in at position 73,534 HFR 5.1 at 12.66℃. Meanwhile we kept noticing satellites going across the ASC which I now believe are potentially StarLink so very annoying.

ASC with Satellite

The new autofocus settings seem to work better. Anything less than 1500 step size would be less than the seeing, as proved tonight so I may find that 2000 is ideal, a test for another night. Also noted that Red filter was showing the worst HFR changes due to seeing and humidity was around 75%, again worthy of note to see how good the seeing is. The guiding was all over the place tonight, again another indicator of poor seeing. So all these things are not poor setup or poor software but poor seeing!

This I believe was the ISS going over captured in the ASC.


I was really pleased GingerGeek and I had spent time a week or so ago when the Moon was around working out the location of the Field of View (FoV) indicator on TSX, it makes it much easier to find a guide star, although tonight M98 had a couple strategically placed which was great.

FoV for Off Axis Guider and the OS main camera

By 2pm the cloud had started to appear, first at South Winston with Steve’s setup, then at Mil Dave’s at Tadley and finally here some 15 minutes later. The guide star was lost by PHD and SGPro in a well ordered fashion did what it is really good at and stopped imaging.

SGPro can’t continue imaging due to guide star loss πŸ™‚
PHD2 and guide star loss due to cloud

Here is where I got up to so LRGB on M98 for the night with 15 x Luminance and 12 x Red, Green and Blue was the original first image for each was there wrong exposure time, so RGB at 2mins and Luminance at 5mins. Very happy for an evening testing and gathering data at the same time.

Here is a set of image statistics charts for each filter for the HFR changing over the evening whilst I refocused. Next time I will focus once and not refocus and see what happens with the temperature drop.

Final look at the AAG weather station as the cloud sensor which is Infrared makes the dome unsafe and shuts it.

AAG Weather Station now Cloudy

Here is the final view from the ASC

ASC and cloud

and of course to finish the evening off another satellite!

Viewing Report – 9th May 2020 – IMT3 – Dark frames, filter

22:05 Frame and focus on 9.26 and 7.64 magnitude stars used before moving to M61 to capture some Lum frames for calibration of flats to solve the doughnut embossing.

22:18 Slewed to M61, performed Solve ‘n’ sync, slew here for centring the object, ran four Luminance subs of 300 seconds each (Bin1x1) at Gain 139 and Offset 21. This was completed by 22:38.

22:45 Chief TOSA then warmed up the CMOS camera, set the filter wheel to the empty slot position, powered off and disconnected the camera and filter wheel. This was so the ASI1600MM and filter wheel could be detached and a blanking filter installed into the empty filter wheel slot position without having to open up the filter wheel. The idea is that we move to the blank filter position when taking Dark subs to prevent light leakage on the Officina Stellare 12-inch.

22:55 Everything was back online and the SGPro profiles were modified to reflect the new blank filter location.

23:13 Unfortunately a dust mote was introduced onto the CMOS sensor window so we sent Chief TOSA back out to the dome to do the job properly this time πŸ™‚ This meant parking the mount, warming up the camera, powering off the camera, remove it, clean the sensor and reattach the camera.

23:24 All reassembled and powered back on, slewed to NGC 4147 (Globular cluster) ready for a a 60 second Lum filter test which showed that a decent cleaning job had been done ….. about time too !

23:40 As it was getting hazy/cloudy it was decided to collect some calibration frames, in this case 25×10 minute dark subs at Gain 39 Offset 21 using the new blank filter.

23:50 We logged off from the remote session and left the dark frame sequence running until it was due to finish in the early morning.

AAG CloudWatcher Installation

We recently decided to replace our existing weather station with one that had better ASCOM integration. I had previously looked at the AAG CloudWatcher but at the time felt it offered more than we need but that turned out to not be the correct choice.

We ordered the AAG with an internal humidity sensor, the optional anemometer, mounting kit and 10 meter communications cable. Due to the ongoing human malware situation it took two weeks for it to arrive from Spain and was delivered to the IMT3 chief TOSA.

Once the new PSU arrived the Chief TOSA then set about removing the existing weather station and installing the AAG cloudwatcher.

All Sky Camera, AAG CloudWatcher, Unihedron SQM and another rain sensor

This also meant connecting the safety relay circuit wires to the Pulsar Dome, installing the AAG software, downloading the ASCOM boltwood driver and configuring SGPro. Within SGPro we have set the safety status set to be “OK to image” where the required conditions are more stringent than the conditions for the dome to open. The reason being that we want the dome to open as the light begins fade and allow the scopes to cool down but not be okay to image until it is dark.

On the first night of operation we ran into a problem. Unlike the other sensor readings and graphs we would see the temperature and cloud readings have an expected shape but the sky brightness sensors kept going up and down at a regular interval then gave the graph a saw-tooth shape.

Unfortunately this resulted in the safety status going on and off until we overrode it. We sent a quick email to Lunatico reporting the symptoms and asking for advice. It didn’t take long for Jaime to reply informing us that another customer reported the same issue and asked for a few days to investigate.

Good to his word we received an email from Jaime explaining the issue and asking if we could perform a firmware upgrade. Now due to the current lockdown restrictions this meant that I had to co-ordinate over the phone with the resident Chief TOSA to physically disconnect and reconnect the power whilst I remotely set the firmware update. The initial issues encountered were due to PEBCAK (Problem Exists Between Chair And Keyboard) as I had not read the documentation correctly !

New Firmware 5.73 loaded

That evening we watched and the Sky Brightness line graph was now as expected and not looking like a cog shaped wheel. Well done for the quick response and fix, Chief TOSA was a happy dome dwarf again and that’s what counts !

At the moment we are trying to get the cloud sensor to be more accurate to what we visually observe, this is an ongoing effort. We decided to record the AAG Sky Brightness sensor readings at various times and compare with our SQM readings :

EventSQMAAG Brightness Value
Civil Darkness13.08949
Chief TOSA setting OK to open 13.892100
Nautical Darkness18.9228588
Astronomical Darkness19.0328588

Using the above values it looks like we could reduce our chosen threshold level of 2100 to 1000 in order to allow the dome to open and the scopes to cool down. The Sky Brightness does not appear to change beyond Nautical Darkness. We are now investigating the correct value for the early morning from the AAG logs. This is so we know what the Sky Brightness value should be at which to stop imaging and close the dome in the early morning when unattended.

We still have at lot to configure and read up about using the AAG CloudWatcher but at the moment our initial experience is a positive one. Obviously we will be chatting to Lunatico about our level settings and make some suggestions regarding the software.