Feature Tracking Tool

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cairomike
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Feature Tracking Tool

#1

Post by cairomike »

Hi Robin

I do a lot of Solar imaging with a Coronado PST + Altair 178M3 camera on a Sky-Watcher NEQ6 Pro mount, using SharpCap for time-lapse capture.

Today I discovered your Feature Tracking experimental tool (I don't know why I haven't seen it before!), it works very well taking out all my tracking errors and keeping the Sun nicely central.

I'm currently testing it under far from ideal conditions with a lot of cloud, sometimes covering the Sun for many minutes. During those periods the 'C of M' goes all over the place pushing the scope quite a way off, so would it be possible to implement some sort of image quality estimate and stop issuing slew commands when the quality reduces below a threshold? Alternatively, and probably easier to implement; how about a 'C of M' position check and stop issuing slews if the 'C of M' moves too far?

Another question; does the calibration take account of the side of the pier the scope is on? Yesterday I calibrated with the scope pointing West, this morning (05/07/22) I set up with the scope pointing East and the tracking appeared to push the scope in the wrong direction and had to recalibrate.

I have to say your current implementation does work very well and so far SharpCap has always brought the mount back and centralised the image once the clouds have gone.


Best regards
Mike Cuffe
cairomike
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Re: Feature Tracking Tool

#2

Post by cairomike »

Hi Robin

Having had several days of clear skies I've been able to use the Feature Tracking tool for many hours and I have to say it has made a profound improvement to my Solar imaging, so thank you.

I saw in another post that you have declined the idea of implementing PHD2 like auto-guiding, due to the complexities of the various mounts, and as a retired software engineer I can understand that, I was never comfortable implementing a driver for hardware I didn’t have in front of me. However, as far as I can see the current implementation of Feature Tracking, as far as it goes for solar imaging connected to a NEQ6 Pro, requires very little to make it complete.

I use it with the following settings:
Movement: Use Mount, Movement Speed: Guiding Rate
Tracking: Use Center of Mass

There are two issues.

The first and most important is the calibration, it doesn’t take into account a pier side swap when the Sun passes the meridian. I calibrate first thing in the morning with Sun in the East then it has to be recalibrated just after midday. This can be an issue as calibrating the mount movement when it’s pointed close to the meridian results in failures. I have overcome this by allowing the mount to travel well past the meridian before doing a swap, at which time a calibration is successful.

The second is that when cloud cover blocks the Sun the tool keeps issuing slew commands based on a degraded Center of Mass estimate, which can push the mount way off, so some form of quality check would be good. I can live with this but it would complete things.

I hope you can find the time to look into these issues as the tool is so useful.

In the mean time could you tell me where you save the calibration data, I was thinking I could keep two calibration files then just swap them and reload as required.

Sorry this is a bit long, all the best
Mike Cuffe
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Re: Feature Tracking Tool

#3

Post by admin »

Hi Mike,

glad to hear that you had success with the feature tracking - as I have mentioned before it is an odd feature because it can be so hard to get it working sometimes (usually related to mount backlash issues), but when it does work it is rather handy :)

The meridian flip is going to give a rotation through 180 degrees, so it sounds as if all I would need to do is invert the movements in both directions when the 'side of pier' property of the mount changes. I will have to think it through properly to make sure that's right though.

For the lost center of mass - presumably the problem is that the contrast between the solar disc and the background drops considerably (or vanishes entirely) when the cloud comes across, leading to a center-of-mass calculation that is basically rubbish. I guess I could look for a sufficient degree of contrast in the image - along the lines of

* at least 20% must be below 25% brightness
* at least 1% must be above 50% brightness

that might do the trick...

cheers,

Robin
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Re: Feature Tracking Tool

#4

Post by admin »

Oh yes, the saved calibration is in the registry, so a bit harder to tinker with. If you really want to have a go, you will find it at

Code: Select all

HKEY_CURRENT_USER\SOFTWARE\AstroSharp Limited\SharpCap\4.0\misc\FeatureTracking.SavedCalibration
cheers,

Robin
cairomike
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Re: Feature Tracking Tool

#5

Post by cairomike »

Hi Robin

Thanks for your reply.

I'm sure you're right about the pier swap, just reverse the sense of the values should correct it. The lost C of M is just as you say, as clouds come over the C of M moves quite a lot because the sun is partially obscured so your ideas would probably go a long way to correcting it.

I notice you set the tracking rates to 'custom' values, something I noticed today is that the custom values (RA: 15.11807, Dec: -0.007) appear to work better than the EQMOD 'Solar' preset. If I turn off feature tracking but keep monitoring the drift on both axies seems to be less than with the EQMOD preset Solar values. I'm not sure what that tells me about my set up though.

Regards
Mike
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Re: Feature Tracking Tool

#6

Post by cairomike »

Hi Robin

I'm pretty sure you only need to reverse the direction of RA, do you agree?

Mike
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Re: Feature Tracking Tool

#7

Post by cairomike »

I've just confirmed it with my mount, only RA needs to be reversed.

Mike
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Re: Feature Tracking Tool

#8

Post by admin »

Hi Mike,

cool, thanks for that info :)

cheers,

Robin
cairomike
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Re: Feature Tracking Tool

#9

Post by cairomike »

Hi Robin

I don't know if you'd be intested, back in July I captured a short video of the SharpCap screen while Feature tracking was enabled, it nicely demonstrates both recentering and the effect of clouds rolling in.

I can't attach it because of its size, so if you'd like to see it let me know how to get it to you, WeTransfer.com maybe?

Regards
Mike
cairomike
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Re: Feature Tracking Tool

#10

Post by cairomike »

Hi Robin

Today I calibrated with the Sun in the East (ASCOM Trace: SideOfPier=1). I've just done a pier swap (ASCOM Trace: SideOfPier=0), then edited the values in the registry by changing the sign of the first two numbers after the '=' and the tracking adjustments work perfectly.

Regards
Mike
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