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ASTAP platesolving in SharpCap unreliable?

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#1 jrschmidt2

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Posted 05 March 2021 - 10:32 AM

I'm having issues getting reliable plate solving with ASTAP in SharpCap.  My FOV is roughly 0.5 x 0.4 degrees (C8 reduced to f/3 with a Meade f/3.3 reducer).  I get very reliable but slowish platesolving with All Sky Plate solver in sharpcap, finding hundreds of objects (depending on the chosen sigma value).  However I am greedy and wanted to get the faster results that the ASTAP folks boast about.

 

I tried switching and I DO find ASTAP to be vastly faster -- when it works!  However I only have roughly 50% success on (non-blind) plate solves (e.g. Solve and Sync) vs. essentially 100% success with All Sky (which uses astronomy.net) in SharpCap.  Looking at the logs, it looks like ASTAP is not finding nearly as many stars vs. All Sky, which may be part of the issue.  Also, somewhat concerningly, I have seen a few "false positive" solves where I get solutions that I KNOW are incorrect in ASTAP (e.g. reports FOV off by 2x). I am using the H18 star database.

 

Any other folks encountering this issue?  Suggestions?



#2 SanjeevJoshi

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Posted 05 March 2021 - 11:19 AM

I have had mixed luck with both ASTAP and Astrotortilla based on a combination of FoV / camera resolution and seeing conditions.  Under certain conditions, one or the other works.  Never both, never neither :) 

 

Two suggestions -- if you are working with less than ideal conditions and smaller FoVs / cameras like your 224, keep exposure low, gain on higher side, and install both ASTAP and AT.   One of them will likely work under tougher conditions.

 

If you are getting false positives (I never have),  you should look at your basic construct -- FoV / resolution and seeing conditions.  Its not a happy combination.   There are times (when I have not perfectly balanced my system) when the initial slew is several degrees away from target but plate solving always puts it in dead center.



#3 jrschmidt2

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Posted 05 March 2021 - 11:58 AM

The "false positives" have always been on blind solves, where it tries numerous combinations (including guessing FOV).  That said, All Sky blind solves have never yielded a false positive to my knowledge.


Edited by jrschmidt2, 05 March 2021 - 12:00 PM.


#4 alphatripleplus

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Posted 05 March 2021 - 01:53 PM

You might want to contact the developer of the software han.k; he also has a long running topic on ASTAP here.



#5 jrschmidt2

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Posted 05 March 2021 - 04:30 PM

Wow, thanks for the link to that thread!  I learned two things immediately:

 

1) There is a BUG in the (few months old) version of ASTAP I am running that can cause the command-line version (used by SharpCap) to fail in some regions of the sky.

2) It also appears that lots of folks with smaller sensors may have similar issues, which get better with FOV > 3/4 degree or so.

 

I am really excited to try again with the most recent version and see if things get better.  I'm also going be smarter and save a few FITS files of regions of sky where ASTAP fails (but All Sky works) for more detailed study.



#6 kel123

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Posted 05 March 2021 - 05:01 PM

Platesolving in Sharpcap is generally unreliable and slow, I believe it ia a work in progress.

#7 GaryShaw

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Posted 05 March 2021 - 05:33 PM

I guess different folks get different performance on plate solving. I’ve found nearly perfect performance with plate solving. I’ve pretty much stopped using my digital finder since I started using plate solving. If you’re careful to set it up with your gear’s resolution exactly as the SC and Astrotortilla folks advise, it should always work unless atmospheric conditions complicate the process. 
 

I recently found I couldn’t get PS to work and got frustrated until I looked outside and realized it was snowing. Without my digital finder running, I hadn’t even noticed the change in weather. As is often/usually the case, it was user error on my part. 
 

It’s a huge observing asset so don’t give up on it. 
Gary


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#8 alphatripleplus

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Posted 05 March 2021 - 05:38 PM

 

1) There is a BUG in the (few months old) version of ASTAP I am running that can cause the command-line version (used by SharpCap) to fail in some regions of the sky.

2) It also appears that lots of folks with smaller sensors may have similar issues, which get better with FOV > 3/4 degree or so.

 

 

Yeah, I haven't tried the latest versions of ASTAP using the H17 and H18 databases, but if there are issues that topic I linked to seems to be one of the most active ones on ASTAP on CN.

 

I've been lucky that ASTAP works well for me both as a standalone, and when called via CCDCiel  or SharpCap.



#9 Clouzot

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Posted 05 March 2021 - 05:57 PM

To solve a bit more successfully with such a small FoV:

 

- update ASTAP

- Install the H18 database and select it in ASTAP.

- If needed, set the FoV to "Auto" or set it to .4 (which is the height of the field you get with your camera and reducer). This is not necessarily needed with recent versions of SC and ASTAP.

- don't hesitate to push the gain or the exposure up. For platesolving and centering objects, I always use a specific camera preset that has high gain, 1 to 2s exposures, the matching darks (and the mini histogram's grey level already pushed to the left, but this doesn't affect the platesolving, rather the display). I sometimes have to up the exposure to 4s or more.

 

It should allow for a more easy platesolving experience in normal conditions (ie. no haze, light pollution at reasonable levels...).

 

I do all my alignments with the SC + ASTAP combo and it almost never fails, even with small FoVs (C9 at f/10 and a 183MC, for instance, has a 0.3x0.2" field).


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#10 han.k

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Posted 06 March 2021 - 04:10 AM

I I have seen a few "false positive" solves where I get solutions that I KNOW are incorrect in ASTAP (e.g. reports FOV off by 2x). I am using the H18 star database.

 

Any other folks encountering this issue?  Suggestions?

 

Wrong solve results are extremely rare. If you start ASTAP directly you can set some parameters. Two are important. Start ASTAP, load and image and go to the the stack menu (ctrl+A), tab alignment.  Check if tolerance is at 0.007 and "ignore stars less" is at 1.5". Also downsampling is best kept at 0 equals auto. Then save the settings in the viewer under file or just hit the solve button once.

 

Image dimensions should be at least 1260 x 960 pixels or higher.

 

FOV (image height) should be within 5% correct but an offset of 30% could still result in a solve but less reliable.

 

It would be interesting to investigate why less stars are found. With your FOV and an  exposure of a few seconds there should be hundred or more stars visible. You could share an image(s) for further investigation.

 

Han


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#11 barbarosa

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Posted 06 March 2021 - 04:38 AM

Platesolving in Sharpcap is generally unreliable and slow, I believe it ia a work in progress.

There are now many users of SharpCap/ASTAP who report good results with a variety of cameras and scopes. I found ASTAP to be faster than the other two plate solving programs I tried. it does on sometimes, but not often, seem to fail or take longer than expected to find a solution. Slewing a  short distance or increasing exposure or gain, usually does it.

 

If you are not getting reliable and fast plate solves perhaps some other factor is at work. I know for example that it is possible to make an error in setup or download the wrong file, at least it was for me.

 

ASTAP and SharpCap Pro 3 and 4 (beta) work so well with both a refractor and a RASA8 that I no longer bother to star align my mount. A good PA and a plate solve are all you need.


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#12 kel123

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Posted 06 March 2021 - 07:08 AM

There are now many users of SharpCap/ASTAP who report good results with a variety of cameras and scopes. I found ASTAP to be faster than the other two plate solving programs I tried. it does on sometimes, but not often, seem to fail or take longer than expected to find a solution. Slewing a short distance or increasing exposure or gain, usually does it.

If you are not getting reliable and fast plate solves perhaps some other factor is at work. I know for example that it is possible to make an error in setup or download the wrong file, at least it was for me.

ASTAP and SharpCap Pro 3 and 4 (beta) work so well with both a refractor and a RASA8 that I no longer bother to star align my mount. A good PA and a plate solve are all you need.


Does Sharpcap slew your mount and center the target after solving? That's one other feature that doesn't work for me.
According to the settings, there is an option for it to do this but I don't understand how it is in a position to do this when it is not directly connected to the planetarium. Even APT Goto ++ needs you to enter the target into pointcraft for it to solve and center target.
Sharpcap has no internal planetarium or am I missing something?

#13 kel123

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Posted 06 March 2021 - 07:27 AM

In clarification of the above, my thinking is that as the mount slews, of course sharpcap gets it position fro EQmod. As far as it communicates with EQmod, it can also sync. But how is sharpcap expected to know the intended target?

#14 alphatripleplus

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Posted 06 March 2021 - 07:46 AM

Yes, SharpCap does slew your mount and center the target after you have executed a platesolve - In the telescope control panel, there is a bulls eye button that, when clicked, tells SharpCap to 1) call the plate solver, 2) solve the currrent image, 3) sync the mount to the co-ordinates of the  current image, and 4) send the appropriate slew command to move to the correct co-ordinates of the target, which SharpCap gets from the planetarium program. 

 

For all of this to work, SharpCap needs to be connected via ASCOM with a planetarium program, the mount, and a plate solver.  (In  SharpCap's  settings, you can make it automatically connect via ASCOM at start-up).

 

Edit: To answer your second question, SharpCap "knows" the intended target from the planetarium program.( I haven't tried using it with a hand controller instead.)



#15 EmeraldHills

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Posted 06 March 2021 - 07:52 AM

There are now many users of SharpCap/ASTAP who report good results with a variety of cameras and scopes. I found ASTAP to be faster than the other two plate solving programs I tried. it does on sometimes, but not often, seem to fail or take longer than expected to find a solution. Slewing a  short distance or increasing exposure or gain, usually does it.

 

If you are not getting reliable and fast plate solves perhaps some other factor is at work. I know for example that it is possible to make an error in setup or download the wrong file, at least it was for me.

 

ASTAP and SharpCap Pro 3 and 4 (beta) work so well with both a refractor and a RASA8 that I no longer bother to star align my mount. A good PA and a plate solve are all you need.

+1 for this same practice, Barabosa. Three cheers for SharpCap/ASTAP,


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#16 GaryShaw

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Posted 06 March 2021 - 09:21 AM

 

Edit: To answer your second question, SharpCap "knows" the intended target from the planetarium program.( I haven't tried using it with a hand controller instead.)

I don’t always have CdC or any planetarium app running when I do a plate solve and it still works. I wonder if SC is using the coordinate data in my mount in lieu of a planetarium program. I’ll try to check this next clear night. Either way, SC and plate solving are miracles in my experience.
Gary



#17 kel123

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Posted 06 March 2021 - 09:42 AM

Yes, SharpCap does slew your mount and center the target after you have executed a platesolve - In the telescope control panel, there is a bulls eye button that, when clicked, tells SharpCap to 1) call the plate solver, 2) solve the currrent image, 3) sync the mount to the co-ordinates of the current image, and 4) send the appropriate slew command to move to the correct co-ordinates of the target, which SharpCap gets from the planetarium program.

For all of this to work, SharpCap needs to be oonnected via ASCOM with a planetarium program, the mount, and a plate solver. (In SharpCap's settings, you can make it automatically connect via ASCOM at start-up).

Edit: To answer your second question, SharpCap "knows" the intended target from the planetarium program.( I haven't tried using it with a hand controller instead.)


Thanks for the clarification.

What I couldn't understand is that I haven't seen any settings so far where you can select a planetarium program in Sharpcap. Other capture programs will let you do this and even ask for the port. I use CDC for instance, and I manually select CDC as the planetarium software and enter the port in APT for them to communicate , though both APT and CDC are each also connected to ASCOM EQmod.
After I platesolve in sharpcap, it syncs but it doesn't move the mount? I assume Sharpcap doesn't know the target since it doesn't communicate directly with CDC. I also feel that the option of sync and center wouldn't be there for nothing. Perhaps the goto command should be done directly with EQMod, instead of CDC. Perhaps Sharpcap is designed specially to work this way But for some reason, it doesn't work for me.

I just like the simplicity of capturing with sharpcap. Hence, I always come back to it for simple tasks.

#18 GaryShaw

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Posted 06 March 2021 - 10:53 AM

I believe that SC ‘knows’ what settings you’re using in the planetarium and from your ‘Goto’s’. When I connect the scope to CdC, and do a goto,  SC knows the target and does the plate solve and position correction based on the image it takes after you call for the plate solve. If I use my mounts hand control, SC also knows where I want to go and also will do the plate solve and location correction. What I haven’t tried yet is whether, when using Sky Safari 6 for my goto (my mount works with SS6), SC will plate solve after that. I suspect it will since, either way, SC seems to have the intended coordinates for the goto so it can plate solve and then correct for any slew error. 
Gary



#19 alphatripleplus

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Posted 06 March 2021 - 12:01 PM

What I couldn't understand is that I haven't seen any settings so far where you can select a planetarium program in Sharpcap. Other capture programs will let you do this and even ask for the port. I use CDC for instance, and I manually select CDC as the planetarium software and enter the port in APT for them to communicate , though both APT and CDC are each also connected to ASCOM EQmod.
After I platesolve in sharpcap, it syncs but it doesn't move the mount? I assume Sharpcap doesn't know the target since it doesn't communicate directly with CDC. I also feel that the option of sync and center wouldn't be there for nothing. Perhaps the goto command should be done directly with EQMod, instead of CDC. Perhaps Sharpcap is designed specially to work this way But for some reason, it doesn't work for me.

 

You need to configure the settings in SharpCap - At the top left under "File" choose "SharpCap Settings".  Click on the "Plate Solving" Tab and under "Actions" choose the first option - "Sync Mount and Recenter Target". 

 

If you do that then, under the Scope Controls menu on the right-hand side of the screen,  when you hit the bulls-eye, SharpCap should do a Sync and recentre. 


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#20 alphatripleplus

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Posted 06 March 2021 - 12:04 PM

I don’t always have CdC or any planetarium app running when I do a plate solve and it still works. I wonder if SC is using the coordinate data in my mount in lieu of a planetarium program. I’ll try to check this next clear night. Either way, SC and plate solving are miracles in my experience.
Gary

Yeah, SharpCap gets the mount data via ASCOM regardless of whether you have a planetarium program attached - as long as you either have SharpCap set up to automatically connect to your mount at start-up, or connect it manually. I (and probably most people) have SharpCap settings configured to automatically connect to the mount at start up of SharpCap.



#21 Ptarmigan

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Posted 06 March 2021 - 12:48 PM

To solve a bit more successfully with such a small FoV:

 

- update ASTAP

- Install the H18 database and select it in ASTAP.

- If needed, set the FoV to "Auto" or set it to .4 (which is the height of the field you get with your camera and reducer). This is not necessarily needed with recent versions of SC and ASTAP.

- don't hesitate to push the gain or the exposure up. For platesolving and centering objects, I always use a specific camera preset that has high gain, 1 to 2s exposures, the matching darks (and the mini histogram's grey level already pushed to the left, but this doesn't affect the platesolving, rather the display). I sometimes have to up the exposure to 4s or more.

 

It should allow for a more easy platesolving experience in normal conditions (ie. no haze, light pollution at reasonable levels...).

 

I do all my alignments with the SC + ASTAP combo and it almost never fails, even with small FoVs (C9 at f/10 and a 183MC, for instance, has a 0.3x0.2" field).

I updated to H18 and I have had objects nearly centered compared to magnitude 17.


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#22 roelb

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Posted 06 March 2021 - 09:01 PM

I use CPWI to do Starsense alignment.

Stellarium (connected to CPWI) to search for objects and GoTo. (CTRL 1).

SharpCap connected to CPWI.

Platesolving with "Sync mount & re-center target".

BUT IN STELLARIUM I MUST DO A SYNCING COMMAND (CTRL 3) WHICH WILL SYNC the MOUNT TO STELLARIUM.



#23 Rickster

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Posted 07 March 2021 - 01:07 PM

You guys that can get ASTAP to solve with small FOVs are killing me.  I followed the suggestions above and still could not get ASTAP to solve reliably with my ASI183MM and 2000mm focal length 16in scope (FOV 0.38 x 0.25 degrees).  It works great with my smaller scopes, but not the 16in scope.  After trying everything that I could think of, I switched to All Sky Plate Solver (via Sharpcap) and it solved easily. 



#24 DSO_Viewer

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Posted 07 March 2021 - 01:14 PM

You guys that can get ASTAP to solve with small FOVs are killing me.  I followed the suggestions above and still could not get ASTAP to solve reliably with my ASI183MM and 2000mm focal length 16in scope (FOV 0.38 x 0.25 degrees).  It works great with my smaller scopes, but not the 16in scope.  After trying everything that I could think of, I switched to All Sky Plate Solver (via Sharpcap) and it solved easily. 

I have great results using Sharpcap with the new H18 & ASTAP with my 183MC and C11 at f/6.3. I use 4 sec exposures and the plate solve is completed in 10 to 15 seconds.

 

Steve


Edited by DSO_Viewer, 07 March 2021 - 01:15 PM.


#25 Rickster

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Posted 07 March 2021 - 01:21 PM

Steve,

Are you binning the 183?




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