Does any astrocapture software measure and store the offset between primary and guidescope?

[Avocette]

For planetary capture, I use a Maksutov with Barlow at 3600mm (f26) and a mini-guide scope and camera fitted in a fixed finderscope mount, for initial polar alignment. Subsequently I remove the guidescope and replace it with an optical finderscope (pre-aligned) so that after a mount GoTo I can visually steer the mount to locate the desired object in the primary FOV.
I would much prefer to be able to use the guidescope for GoTo platesolving except this would require it to be physically aligned to the main telescope. Does any software perform a one-time platesolve with the primary scope (at f26 of course requiring pointing at a suitable area of the sky with sufficient stars and at an appropriate exposure), then platesolve with the guidescope and calculate and store the positional offset between the two, then use this offset each time a guidescope platesolve Is needed to correct a GoTo?

[vlaiv]

3 hours ago, Avocette said:

then platesolve with the guidescope and calculate and store the positional offset between the two, then use this offset each time a guidescope platesolve Is needed to correct a GoTo?

I'm not aware that there is such option, but it would not be too hard to align the two scopes to same point so you would not need to worry about offset.

You don't need plate solving to do that - just use your optical finder to point the main scope to a bright star, and center it in FOV of your Maksutov. Then remove optical finder and put back the guide scope and then adjust its pointing so that the same bright star is in the center of it's FOV.

 

[AstroKeith]

Current AP plate-solvers expect to be using the actual imaging camera, and hence no offset handling.

However this is a feature that visual observers will need. I'm using a 'digital finder' with plate-solver on my 18" Dobsonian and needed to manage an offset as I didnt want the complication and expense of an adjustment mechanism.

I built my own system using astrometry.net running on a Pi4B. Part of the suite of modules is a built in method to return the RA & Dec of any pixel offset from the centre. So I wrote a simple offset calibration routine to discover that pixel by pointing the main scope at a bright star and using astrometry.net to find that star and save the offset pixel count.

[Avocette]

3 hours ago, vlaiv said:

……. it would not be too hard to align the two scopes to same point so you would not need to worry about offset.

 

Hi @vlaiv

That’s really the point - in a small grab and go system with a mini guidescope and camera like the ZWO one, it’s very convenient to use the finderscope mount without any physical alignment adjustments - this works very well for polar alignment and guiding purposes. When, for instance, I use my 275mm focal length f4.5 refractor, the offset between the primary imaging camera and the guide camera images has not been an issue in practice. However it’s just with my Maks at 1500, 1800 or 3600mm focal length that the primary image FOV is very small and the alignment offset of several FOVs becomes an inconvenience. With my larger mount and 150mm Mak, I do often use a 50mm Evoguide in adjustable alignment rings, and then as you suggest, with optical alignment the offset can be made of little consequence.
My query was about any software on the market that already takes the physical offset into account. 

Edited May 13, 2023 by Avocette

[Avocette]

58 minutes ago, AstroKeith said:

Current AP plate-solvers expect to be using the actual imaging camera, and hence no offset handling.

However this is a feature that visual observers will need. I'm using a 'digital finder' with plate-solver on my 18" Dobsonian and needed to manage an offset as I didnt want the complication and expense of an adjustment mechanism.

I built my own system using astrometry.net running on a Pi4B. Part of the suite of modules is a built in method to return the RA & Dec of any pixel offset from the centre. So I wrote a simple offset calibration routine to discover that pixel by pointing the main scope at a bright star and using astrometry.net to find that star and save the offset pixel count.

Hi @AstroKeith

Your ingenuity is very impressive!
My present astrocapture software, KStars, already allows me to plate solve with any connected camera, primary or guide. So in principle I could platesolve both images and note down the offset manually, and then compensate for this offset using the manual mount control when I search for another target. At f26 and with an FOV of around 11 arc minutes square, it can be tricky to platesolve, especially in the near presence outside of the FOV of a brilliant planet like Venus. I often can get the primary image to platesolve provided I point the scope to an area of the sky with sufficient stars and no glare from a nearby planet (or worse the Moon).  Hence why a stored fixed offset would be a nice feature, and as you note, with visual observing, a real bonus.