Guiding / Feature Tracking with StarpCap - questions and problems

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Thomas_TK
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Joined: Sat Jun 29, 2024 2:14 pm

Guiding / Feature Tracking with StarpCap - questions and problems

#1

Post by Thomas_TK »

Hi,
I started using the feature tracking in SharpCap and experienced some "effects". Due to my setup I don't want so speak about problems.

Setup #1: Mount: Bresser EXOS2, Telescope: 80/600 with a Daystar Quark H-alpha filter, Camera: Altair PGCam3 176M and PlayerOne Saturn-M
Effect: SharpCap cannot calibrate the mount and gives angle errors. When I look to the graphicy windows, I see that the tracking trial is somehow irregular or a bit chaotic. I minimised the free play in the mount, but it don't help much.
I think, this is because of the 4,2x optics in the Quark module. I didn't find a possibility to give some parameters about the telescope or the mount.

Setup #2: a 240mm guiding scope with solar filter and the Altair GPCam3 178M on the same mount for the guiding, piggyback on the main telescope. Sharpcap is able to calibrate and start the feature tracking. But it started with a up-and-down movement. When I pressed one of the mount-steering arrows, this movement stopped for a while. One time it started to run out of the view, but this stoped when I resterted the tracking. I think, it just lost the points.

This movement is very small in the guiding scope, but in the main telescope this was about 50+ pixel, sometimes more. On the other hand there is a big difference in the resulting focal length: 240mm vs. ca. 2500mm.

Is there a possibility to configure the focal length or the link between guding pulse, movement, reaction time etc.?
The piggyback-solution would be ok, if it wouldn't start to oscillate.

Thanks,

Thomas
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Re: Guiding / Feature Tracking with StarpCap - questions and problems

#2

Post by admin »

Hi Thomas,

firstly, if you are not already on the very latest SharpCap 4.1 then it's worth updating, as I have been fixing and improving things in feature tracking recently. In particular there is a new 'Phase offset' tracking mode which should be more reliable than the 'Image Features' mode. There is also now the option to use continuous movement for calibration, which helps a lot with some mounts.

If you are getting a 'V' shape in the scatter graph from the first two calibration stages and then a failure with a message about angles then the most likely cause is that the mount is pausing tracking while it is being asked to move in declination - that means that the image will appear to move due to both the requested declination move and the sidereal motion that is not being tracked temporarily. Increasing the calibration movement speed can often help here, along with switching to continuous rather than stepped calibration movements. You may find that you need to also adjust the minimum 'required movement' for calibration too.

If you are seeing oscillation (over-correction) then you can turn down the 'Correction Scaling' setting in the guiding settings - set it to 50% and SharpCap will make a correction of 1/2 the calculated value, then make further corrections the next time round as required.

The current system uses a calibration approach rather than entering focal length, since there are other factors that go into the relationship between image movement and mount movement, including the rotation of the camera, pixel size and whether there is an odd number of mirrors in the imaging train. Trying to ask someone to accurately enter all of those is probably unrealistic, so a calibration approach is easier.

cheers,

Robin
Thomas_TK
Posts: 3
Joined: Sat Jun 29, 2024 2:14 pm

Re: Guiding / Feature Tracking with StarpCap - questions and problems

#3

Post by Thomas_TK »

Hi Robin,

I see, there's a new version. I will install immediately, of course.

I tried already some of what you mentined. I will test the rest, but I think it may take while.

Thanks,

Thomas
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