auto-guider – IMT3b Observatory

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℃

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.

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.

For reference here is the luminance flat.

Next up was Red filter for 300 seconds

Then Green filter

Then finally Blue filter.

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 ….

Meanwhile the humidity kept rising

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.

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.

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

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

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.

and of course Mil Daves….but no, he forgot to save it 🙁

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.

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.

Dave’s grabbed the NGC 7331 below.

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.

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.

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 +01° 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.

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 –

Next whilst GingerGeek went off to get his beauty sleep…..he really needs it 🙂 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.

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.

Meanwhile the clouds from the North had started to drift in which was going to stop play 🙁

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.

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 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.

The resulting image looked very good too

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.

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 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℃.

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.

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 🙂

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.

Here is the final view from the ASC

and of course to finish the evening off another satellite!

Viewing Report 2nd May 2020 – IMT3

22:00 – 23:59

This evening GingerGeek and I simply set out to align the off axis guider of the OS on TSX. We did this buy focusing on the Moon and adjusting the off axis guider for he crater we were seeing. The resulting image is not very good which give rise to a though that the OAG should move it’s position in the imaging train to give better star renditions, the issue is I think it is as far back as it can go due to the filter wheel.