Autoguider Troubleshooting 12″ OS

8th April 2023

After a successful morning of Luke helping me rewire the 12″ due to the removal of all computers apart from the Mac Mini, I looked at why the guider kept disconnecting last night and then not calibrating. It transpired to be the length of the USB run. I was hoping through 3 hubs and many meters of cable. On replacing the cable with a shorter one and plugging it into a single hub, the connection error went away. The only thing left to do was test auto guiding at night.

So roll on evening and I went out early to catch the first starts. Luke and I had replaced the All Sky Camera during the day so we wanted to see what that looked like, It is fair to say the ZWO ASI178MC is an amazing upgrade to the rubbish little ZWO ASI120MC I had been using.

New ASC with wider lens

So after much messing about with trying a camera other than the SX Lodestar, trying several pieces of software including PHD2 that I could not get working, I settled on TSX for guiding and managed to get it calibrated. On swapping the side of the mount and recalibrating I had a similar problem, however I think the brightness of the guidestar, along with the exposure time and the order I was doing things in had caused the issue.

Below are the settings used for the working system, note the calibration distance is 30 arcsecs which is fine if you calibrate on a star rather than a hot pixel.

Relay Settings including Direct Guide! 30 arc seconds for calibration distance

Successful calibration East side of mount

Successful calibration West side of mount

Guide Target Method


X2 Plugin and remove hot pixels

Autoguide tab – long exposure and subframe selected

more settings

Final settings


So you must select a bright enough star.

You must put a subframe round it.

You must them expose on that subframe.

You must then calibrate that subframe.

Exoplanet TOI-1789b (15/4/2022)

19:35 – 00:40

Tonight is a synchronous group observing campaign with Exoclock. We are going after an exoplanet around star Tycho 1962:0303 / HD 82139. I note that HD 82139 does not come up in TSX but the Tycho star in the right format does. I tried to install the 6GB USNO B database but it fails with an error that the files are not all in the directory. I will try to sort this out later.

Start of transit was 22:28 BST Mid transit 23:37 BST , End of Transit is 00:47 BST, 1 hour after transit is 01:47 BST

I had an initial problem after starting the imaging run, the focuser went back to 14000 again which meant I was out of focus. I only noticed later and then restarted, fortunately before the start of the transit.

Reviewing the files the following evening I noted the dome closed around 00:40 so 7 mins before the end of Transit. I have no idea why the dome closed…….

Transit submitted

Exoplanet HAT-P-66b (25/2/2022) – IMT3 + Visual with 22″ Dob!

21:24 – 03:00

So for the first time in a while the observatory is back up and running and it’s Friday and it’s clear! So Bob came over and we set about imaging an exoplanet and getting the 22″ Obsession dob out of the warmroom where it had been sitting since November, and moving it down to the observing plateau by the IMT3b observatory.

A few nights back, during the week I had managed to get the 12″ in the dome balanced with my original 2004, 5″ Skywatcher 130 reflector as a guide scope and the Skywatcher Esprit 120 ED on the other side. The 5″ now guides, however the QHY camera on the 120 is not currently connecting so I need to investigate. Also the MEII hand controller is sending erroneous signals to the mount so I needed to disconnect as it kept saying ‘joysticking’ and moving the mount. Unfortunately the 5″ was pointing at the dowel so I used off-axis guiding instead.

Blue 5″ scope pointing at the dome

I selected an exoplanet on the Exoclock website, and set about imaging. Unfortunately due to my profile on exoclock being set to UTC +1 and me not noticing I started 45 mins into the transit! I will now use this as a test run and process the data and submit.

Exoplanet schedule

So first up was moving the 22″ down to the plateau so it could cool down. I had planned on taking it back up to the Warmroom, however it is so heavy I have decided to keep it in the workshop. I will make sure I connect the electric up for the workshop this weekend thus allowing for the new dehumidifier to be switched on and operational.

22″ UC Obsession telescope

Whilst the 22″ cooled down, we went back indoors and setup the 12″ in the observatory to image the transit. The focus point was 25,000 and I made sure I selected the Red filter. I slewed and aligned on the exoplanets host star and then settled on a 5min exposure due to the low brightness. I started imaging at 9:24pm, the transit start was 8:45pm 🙁

HAT-P-66 b

Whilst imaging continued we went outside and set about setting up the 22″. Things I learnt from this first public outing were;

  1. Remember to put the shroud on
  2. Remember to pub the secondary shield on
  3. Remember to collimate the secondary first
  4. Remember to fit the Telrad dew heater
  5. Remember to find a 40mm eyepiece
  6. Remember to download and print the Parracor chart
  7. Remember to set the Parracor to the correct setting
  8. Remember to buy a 12v battery powered hair dryer
  9. Remember to buy a secondary dew heater

We collimated the scope and then went on to look at M42 which with the 24mm Panoptic looked great. We then slewed to M45 the Pleiades but of course the open cluster is too wide for the for I was using. Then we tried find M81 and M82 but I found this difficult due to the lack of bright stars in the area. So instead we went to the Trio in Leo.

M65 and M66 looked fairly bright and you could make out the dark dust lane in M65. NGC 3628 was visible with direct vision, however with adverted vision it was much easier. It appeared very long and thin.

We had to use s hairdryer on the secondary a lot. The Telrad also dewed up as did the eyepiece. The primary mirror was fine, although with direct headtorch light looked like it was dewed, but upon inspection this was not the case.

At midnight it was time to pack up before I had to do a meridian flip. Bob helped my dismantle the 22″ dob and then place inside the workshop. I could not move it into the room without dismantling which was a shame. It is far too tall.

Once done, Bob headed off home for a well deserved rest and to warm up due to it being 0℃. I headed indoors and performed the meridian flip at 0:23am.

I then left the observatory running until 2:30am whilst I wrote this blog, had a glass of wine and ate an easter egg 🙂 I also went back out to the workshop to tidy up the telescope eyepieces etc that I had not put away.

At 3pm I went on to take luminance for M85 that I needed to complement the RGB data I had processed. I let this running and went to bed.

M85 Lum 300s

I took flats and dark flats in the morning, although I had to increase the exposure to get the required level for the flats. This is strange as they should be the same. I am now concerned the camera my be playing up and causing an issue. I will investigate.

Viewing Report 1st October 2021 – IMT3


Kelt 16b

Focus 20,329, taken with Luminance filter rather than red

GAIN 75 OFFSET 12 -25℃

Rotator Angle 29.420

Dome stopped at 582 images so need to see how many good ones I got

Clarity got worse from 1:18am until 3:52am when it clouded over, imaging is no good just before 1:15am so mid transit

Observ. Priority: LOW
Total obs. (Recent): 35 (5)
O-C minutes: 0.6±0.21
Alt: 65°
Azi: 228° (SW)
1h Before
Alt: 57°
Azi: 249° (W)
Alt: 45°
Azi: 266° (W)
Alt: 34°
Azi: 280° (W)
Alt: 25°
Azi: 291° (W)
Max counts increase during observationR:0% V:0%
Moon illumination: 22.5%, Moon distance: 126.5°
Observing times [ UTC+1.0 ] and target position
Kelt 16b FoV

1st Exoclock Conference & IMT3b

25/09 AM – Exoclock Video Conference Day 1

So I had planned to sit in on the Exoclock Annual meeting all day for both days but in the end I could only attend for the pre-lunch meetings as I had promised Dave that I would assist at the IMT3b observatory. So I will catch up on the afternoon talks when they are made available online.

The talks were varied and included experts from the Ariel Mission, Twinkle Mission, JPL, Telescope Live, BAA , members of the Exoclock project followed by workshops of which again I really wanted to be present to participate in the CMOS workshop but I couldn’t.

1st Exoclock Annual Meeting Agenda

25/09 PM – IMT3b Warm Room & Donkey Work

We shutdown the dome computers, network and whilst Bob started on the warm room electrics Dave and I proceeded to 1 ton of scalpings from the front of the house into wheelbarrows and then push them up the garden to be stored ready for the warm room patio construction. It was a very humid day and we were both sweating heavily by the end of it.

The dome computers were repowered and outstanding software updates applied (BIOS, Windows updates, windows software and RPi4 OS & software) before the Autumn imaging sessions begin in earnest.

The day was rounded off by relaxing with a glass of red wine and dinner with Bob, Dave and the family. As the evening turned out to be cloudy there would be no imaging so it was an early night ready for the hard graft on the following afternoon.

26/09 AM – Exoclock Video Conference Day 2

Another set of fine talks and I especially thought it was a nice touch that an artist Lea who won the new Exoclock Logo Competition was awarded some imaging time on Telescope Live.

Lea took a bit a time explaining her background and how she formulated the design for the new logo.

New logo courtesy of Lea Changeat

It was even better that not being an astronomer she was persuaded to undertake some Exoplanet observations and report on her experience.

26/09 PM – IMT3b Warm Room Windows

The 7ft double glazed windows were put by Dave, Luke and Tim and myself. It was nerve racking as we manhandled the two panes from near the side of the main house up steps and along the garden with the Tim and Luke taking the awkward window corners whilst Dave and I used floor tile clamps on the glass.

The warm room aka “Wooden GreenHouse”

Bob came over to complete the electrics for the warm room and I left when Dave started stretching on tiptoes to put in the red & white light fittings. I figured I could complete the remaining software updates remotely.

The AAG software was updated to 9.1.4 from the old 8.1.0 version, we still need to investigate the wind sensor reading with Jamie from AAG.

AAG 8.1.0 sensor limits
AAG 9.1.4 sensor limits and new sensors

So we now access to the Humidity sensor settings and the appropriate alert levels. Previously I had to rely on both ASCOM local conditions and internal dome humidity via ASCOM (BlueAstro StickStation) but I wonder if we want to trigger an unsafe state by including the humidity thresholds.

Exoplanet HAT-P-1b (17/9/2020) – IMT3

20:24 – 22:43

Imaging with GingerGeek for another exoplanet. This one starts its pre-transit at 23:55 and should just about be on the point at the meridian where we can perform a meridian flip and then image all night.

We like to make sure we have the right star field so actually having a photo from the exoclock website helps. Tonights candidate is the dimmer star to the left of this pair.

The star is a magnitude 10 star in Lacerta. Unfortunately despite the forecast it has just clouded over, here is what we would have been imaging.

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 HAT-P-6b (5/9/2020) – IMT3

Session period 19:00 – 01:18, transit start ~23:06 and end ~02:37

Before I move house, we are going to try and grab another exoplanet or two or possibly three…..we’ll see. Tonight whilst it is currently clear and due to cloud over by 1am, we will go for HAT-P-6b that is on alert from Exoclock.

Exoclock Exoplanet on Alert tonight

The transit end time is after it is due to cloud over but we may be able to get the start of the transit and some useful data to possibly half way through. So I have opened the dome, started to cool the 12″ down and slewed to a magnitude 4.29 star in the vicinity of Andromeda called HIP 116631 also known as 17 Iota Andromedae in the Flamsteed catalogue so that I can slew and centre on the object when it gets dark.

HIP 116631

I’ve now manually centred the star due to the brightness of the sky still and synced in The Sky X

Manually centred
HIP 116631 in relation to HAT-P-6b

I’m now waiting for a bit more darkness to perform the first focus run.

At 20:31 I performed a focus run on the mag 4.29 star with the red filter and got position 63007 @ HFR 5.2 and temperature at the focuser of 17.28℃.

Focus run on red filter

I have performed another solve and sync as I had left the scope running for a while without guiding and the star had moved slightly.

Solve and Sync on target

I have now taken a quick 20 second exposure of the target to confirm it was the right star as per the star chart from the Exoclock website and it was.

20s exposure of HAT-P-6b

I have started guiding on a nearby star with PHD2.


HAT-P-6b rising from the East as can be seen in TSX.

HAT-P-6b rising in the East

So here is a 2 minute exposure of the target. I tried 60 second but given I am running Gain 10 Offset 10 the maximum pixel count for the centre of the star was 1,648 out of 65k. So a 2 minute exposure produces 9,488 which is still low but I will continue on the low side for now. 1 hour before the transit is in about 45 minutes so I will wait then start gathering data.

2 minute exposure of HAT-P-6b

So we’ve started and set to run for 5.5 hours, this means a a meridian flip in 4 hours time so I will need to stay up until 2am, perform the flip then head back to bed.

First image down

The clouds have started to roll in, however so far we have been lucky and our star and planet are just outside the bank of cloud …… but for how long?


So it finally clouded over around 1am although the data for the past 20 minutes is suspect, so I hope we at least have the first half of the transit.

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.

Exoplanet WASP-80b (8/8/2020) – IMT3

22:00 – 01:44 (GingerGeek came over and Bob was remote)

So the original plan was to perform another exoplanet observation and improve/learn from our previous experiences. However the weather did not look like it was going to be accommodating so we decided to change plans.

At first we planned to take a shot of Pluto and then go back to it later on in the month to see how far it had moved but it was low and below the the IMT3 visible horizon.

Next up was to continue imaging Messier objects for Dave’s Messier Marathon collection. We settled on M14 and had created and started an imaging sequence but again the clouds rolled in putting a stop once more to some constructive imaging.

So we then decided to track an asteroid for as long as we could before the clouds stopped us. Once Dave had loaded the asteroid database into TheSkyX we then choose one close by to the previously planned Exoplanet. The asteroid 85275 1994 LY (magnitude 14.01) was in the constellation of Ophiuchus.

We turned off PHD autoguiding and mount control in the SGPro control panel as we were going to be using mount tracking on the asteroid instead of sidereal.

Autofocus using Luminance filter – 60,389 position, HFR 5.0, Temp 24.94℃. We started at 22:46 and took a series of 30 second images until the cloud cover stopped us. Dave then used the Pixinsight blink script to stitch the resulting FITS->PNG images into a movie, then looped the short AVI, added titles and music in iMovie (best viewed full screen and in HD).

Exoplanet WASP-93b (1-2/8/2020) – IMT3

Session time 21:00 (1/8) – 03:41 (2/8)

@ 19:00 Opened dome in order to cool the dome and scope down.

@ 21:00 GingerGeek arrives, wine is poured and we took 5 x darks, flats and bias for both the last run and tonight. The flats (red) were 3 seconds exposure to get 2/3 well depth required for this.

@ 21:44 Slewed to WASP-93b before we set about focusing on a nearby magnitude 5 star using the Red filter. Starting focus position was 58841@19.42℃.

@ 22:06 After failing to focus using the Red filter we resorted to using the Luminance filter to auto focus and achieved a excellent fit (focus position 61630, HFR 4.95 @20.83℃).

When we swapped back to the Red filter, SGPro then moved the filter offset to focuser position 60630. We slewed back to WASP-93b (GSC:3261:1703) and found a guide star just off centre of the star field with the exoplanet target.

Started to take exposures to find the brightest value of the centre pixel of the star and make sure it was 2/3 full well depth and thus 33,000 ADU (even though it is a 12-bit camera SGPro is set to 16-bit for ease of use. Eventually this was achieved at around 200 second exposure.

@ 22:51 Started imaging, 18.21℃ was measured at the focuser.

Frame and focus of starfield
Target star for Exoplanet measurements
Local conditions
200s exposure of starfield
Another plane!
Target location in Cassiopeia
Details of WASP-93b transit for tonight
Some cloud early on in the night

Mars imaging finished at 03:41

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.

Analysis Report for first partial Exoplanet Data – IMT3 Observatory

I managed to get only 45 minutes worth of data the other night to test if I could both acquire data and then process it. It took some time to get the downloaded HOPS software from the ExoClock mission working on my Mac, but with the help of Angelos from the project. So I opened the 46 images, I did not capture darks or flats and of course no bias due to it being a CMOS camera. I added information about the observatory and then ran the reduction and alignment code.

Completion of details and opening of 46 images

So the initial chart looked promising, I had taken the first set of frames almost on time for the transit even though you are supposed to start 1 hour before. This was because it took me so long to setup. So the data looks like it shows a decrease in brightness over the 45mins, however I have asked Angelos for his opinion and await a response.

Output from clicking Run Reduction

I then selected the target star, KELT-18 with the red circle below, along with 5 comparison stars. I may have selected stars incorrectly here as they are probably suppose to be not variable.

Alignment and comparison star window

The resulting table appeared with the size of the box for each star and its position.

Resulting target and comparison stars

I then ran the photometry code and the following chart was created which to me showed I had done something wrong given the scatter.

Graph output with actual photometric values and PSF in red

I then for fun ran the fitting code from this screen.

Information for Fitting

The fitting showed and increase in brightness which was clearly incorrect. So I have learned a few things with this, first is to read up on using the software for analysis, second is to gain more data and calibration frames.

Resulting output clearly showing problems with data

Viewing Report 29th December 2019 – IMT3 Observatory

Viewing time period – 17:43 – 17:48


Slightly hazy right now but I have opened the dome up and turned the cooling fans on the 12″. Slewed to Atik, a mag 2.8 star in Perseus and aligned the scope.

Atik mag 2.8 star in Perseus for alignment

So the star was almost in the centre when I slewed the scope to it, a slight tweak and now synced on it centrally. The Hitec Astro weather station reports slight haze

Hitec Astro Weather Station showing haze

Gingergeek installed a new Intel Windows small form factor computer recently in replacement for the RPi so we could run the AllSkEye software and see if the loss of one of the colour channels was software or hardware. Here is tonights image, which still needs colour calibrating during the day.

AllSkEye camera software

Viewing Report 25th December 2019 – IMT3 Observatory

Viewing time period – 19:10 – 20:32


As always on Christmas Day, or at least it seems so, the sky was clear for a period of time before the clouds rolled in. The day was dry and cold, sunny and bright, the first time in over a month of rain. Now was the time to take a look at a star and see if I could calibrate my setup for imaging an exoplanet transit.

All Sky Camera

I used the website to find objects for my location and then entered the RA and DEC into The Sky X (TSX) and slewed to it. The star and its associated planet tonight was KELT-18 and the planet KELT-18b. This was very low to the North when I slewed and I struggled doing a slew and sync with the scope in TSX due to not enough stars found.

Exoplanet Target List from

So instead I placed the RA and DEC into SGPro and asked that to perform a slew and solve, which incidentally worked an absolute treat. The star was centred in the middle of the FoV and the star pattern matched that from the Exoclock website which they give you.

Kelt-18b details including interactive star map

I then setup SGPro to take as many images as I could, each being 1min long as I could not find a guide star. At 1min I did not get any trailing and I should have said, all of this through the 12″. I set the cooler to -28℃ which consumed about 26% power so nicely cold. I choose the red filter as described to lower the amount of noise in the image and allow calibration with other astronomers images.

Resulting image

I had to change the user profile to the Comet profile as I did not wan the guider trying to settle, so restarted the run and was off. I managed to go for around an hour and thus grabbed 46 images. I am not sure if I can use the HOPS software from Exoclock to plot these but will try. I did not bother with calibration frames and if needed I can grab some later.

SGPro sequence running

Either way, a good hours viewing in-between the outgoing festive cheer from one side of my family and the incoming festive cheer tomorrow from the other.

Merry Christmas and Clear Skies