Plate Solving Problem in APT

[Somerled7]

Last night I came across a problem with APT trying to plate solve to the Lobster Claw Nebula. I have an HEQ5 connected via the Synscan wifi module and I'm using the ASTAP solver. Usually it works fine, but this time it solved the first image than said it could not move the scope to the new location. Here's the APT log after the solve:-

2023/11/28 23:32:00 (UT 2023/11/28 23:32:00) DBG      RelativeGoTo - SRa:23.256415317, SDec:60.174225994, TRa:23.254444444, TDec:60.174166667, RRa:22.345884323, RDec:55.016101837, NRa:24.164975438, NDec:65.332290823

2023/11/28 23:32:00 (UT 2023/11/28 23:32:00) OpErr    Cannot slew to coordinates.   Exception occurred.

2023/11/28 23:32:00 (UT 2023/11/28 23:32:00) OpErr    PointCraft Error: Can't move the telescope.

So the solver worked OK and showed the scope was off by about 1 unit in RA and 5 in Dec, but then it failed to move.  

I tried changing the target Dec to a random value of  55deg and it plate solved to the location no problem, then re-tried the Claw Nebula location again at dec 60deg and the same failure. For some reason, it seemed like it didn't like those particular co-ordinates! Any ideas?

[wongataa]

What happens if you try a different plate solver?

[Somerled7]

19 hours ago, wongataa said:

What happens if you try a different plate solver?

I didn't try that as I don't have another plate solver set up - something I should do in case of problems. Anyway, tried again last night and it plate solved successfully, so no idea what the problem was.  

[Paul M]

I say it isn't a plate solving issue, more an issue with APT/Ascom failing to drive the mount to the required coordinates.

I've had issues with APT doing odd things ocassionally. Including events like yours.

Shutting down and restarting APT or even a full reboot usually returns normality.

I've got bogged down, over thinking problems in the past. But now just bite the bullet and restart.

It's likely that you won't even be able to replicate this particular problem on your next outing!

 

 

[Somerled7]

On 30/11/2023 at 10:59, Paul M said:

I say it isn't a plate solving issue, more an issue with APT/Ascom failing to drive the mount to the required coordinates.

I've had issues with APT doing odd things ocassionally. Including events like yours.

Shutting down and restarting APT or even a full reboot usually returns normality.

I've got bogged down, over thinking problems in the past. But now just bite the bullet and restart.

It's likely that you won't even be able to replicate this particular problem on your next outing!

 

 

Thanks Paul - yes, I was more successful the following night, so hopefully a one-off. 

[ollypenrice]

Don't forget that plate solving isn't compulsory. You can derive the RA and Dec co-ordinates of your image centre from a planetarium loaded with your specific field of view and then go to a nearby star, re-centre your mount on that star, then simply drive to the co-ordinates manually.

Olly

[Somerled7]

5 hours ago, ollypenrice said:

Don't forget that plate solving isn't compulsory. You can derive the RA and Dec co-ordinates of your image centre from a planetarium loaded with your specific field of view and then go to a nearby star, re-centre your mount on that star, then simply drive to the co-ordinates manually.

Olly

Yes, I could have tried a more 'manual' approach.  However this was only one of several problems on a frustrating night that ended with me giving up! I know what the source of the other problems were, but couldn't figure out the plate solving issue and wondered whether there might be some setting in APT or ASTAP that I had forgotten about.

[ollypenrice]

36 minutes ago, Somerled7 said:

Yes, I could have tried a more 'manual' approach.  However this was only one of several problems on a frustrating night that ended with me giving up! I know what the source of the other problems were, but couldn't figure out the plate solving issue and wondered whether there might be some setting in APT or ASTAP that I had forgotten about.

I'm doubtful about the wonders of computerization. It very easily turns itself from the solution into the problem.

Olly

[tomato]

Some computer based tech has to work on the night, eg image download, electronic filter wheel, but as Olly points out some are nice to have like plate solving and electronic focusing. Personally I wouldn’t lose a precious clear night trying to fix any of the latter, they could wait for a more convenient time.

[John_D]

15 hours ago, ollypenrice said:

I'm doubtful about the wonders of computerization. It very easily turns itself from the solution into the problem.

Olly

This is so true. Having spent my professional life designing electronic/software devices of various types and sizes it's very difficult to get them to work reliably 100% of the time. And it's an order of magnitude more difficult when you try to integrate several of them together.

Looking at some of the YouTuber telescope setups I'm amazed any of them work at all 😁

[Somerled7]

Thanks for all the replies. In the end my night was scuppered not by a computing problem but a mechanical one - my mount was tracking weirdly, and when I opened it up I had a badly deformed belt drive. So I need a new belt and am in discussion with Rowan Engineering about what went wrong. My experience of astro-photography is that everything is a potential problem - it's just a question of which problem manifests itself on any given night!