Keeping a Planet Aligned while Imaging
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Re: Keeping a Planet Aligned while Imaging
I tried it again this weekend and it worked very well. Nice Improvement !
Re: Keeping a Planet Aligned while Imaging
A question I’ve been meaning to ask, which is relevant here, is about the function of “Track planet - Centre” in the Camera Format and Area group when a ROI is selected. If I were to use Feature Tracking, w/ Centre of Mass selected, and enable this Track planet centre in the ROI control, would that work together to give me the best of both Worlds? I.e. use Tracking to drive the mount to keep the planet roughly in the centre of the camera FOV and the use the ROI to keep it more accurately centred in the ROI image frame by frame.
This is a new feature that I have not tried yet (and my telescope image train is in pieces as I prepare for a new scope).
Cheers, Chris.
This is a new feature that I have not tried yet (and my telescope image train is in pieces as I prepare for a new scope).
Cheers, Chris.
Celestron EdgeHD 8, reducer 0.7x, Star Sense, CGX-L mount, Focuser, CPWI; Starlight Xpress AO, OAG and Filter Wheel; ZWO 294MC/294MM Pro and 174MM mini; SharpCap Pro, PHD2, Televue Powermate 2x, Baader Neodymium, Astronomik CLS-CCD, ZWO UV/IR, Duo filters
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Re: Keeping a Planet Aligned while Imaging
Hi Chris,
I don't think that using those two features together will work out ...
If you set the feature tracking dead zone to be small and the adjustments to be fairly fast/agressive then you might manage to keep the planet cetered with feature tracking and the ROI movements would never kick in
If you have more relaxed feature tracking settings then the movement will build up enough for the ROI adjustment to happen, and that will then convince feature tracking that it's job is done, which then allows more physical drift to build up.
It might just be possible to make the two work if I changed the feature tracking so that it looked at the (Planet center + ROI offset) position rather than just the planet center position. In theory that would allow it to monitor the physical drift on the sensor rather than the drift in the ROI. However, there is a problem - most cameras update the ROI a few frames after the request to change it is sent for high speed imaging - SharpCap doesn't know how many frames later that update will occur and normally it doesn't really matter. If you start taking this approach, it does matter, since in the period between sending an ROI change request to the camera and the frames actually showing the effect, the value of (Planet center + ROI offset) will be incorrect.
Not sure if that last issue would be enough to throw the feature tracking into a wobble or not...
cheers,
Robin
I don't think that using those two features together will work out ...
If you set the feature tracking dead zone to be small and the adjustments to be fairly fast/agressive then you might manage to keep the planet cetered with feature tracking and the ROI movements would never kick in
If you have more relaxed feature tracking settings then the movement will build up enough for the ROI adjustment to happen, and that will then convince feature tracking that it's job is done, which then allows more physical drift to build up.
It might just be possible to make the two work if I changed the feature tracking so that it looked at the (Planet center + ROI offset) position rather than just the planet center position. In theory that would allow it to monitor the physical drift on the sensor rather than the drift in the ROI. However, there is a problem - most cameras update the ROI a few frames after the request to change it is sent for high speed imaging - SharpCap doesn't know how many frames later that update will occur and normally it doesn't really matter. If you start taking this approach, it does matter, since in the period between sending an ROI change request to the camera and the frames actually showing the effect, the value of (Planet center + ROI offset) will be incorrect.
Not sure if that last issue would be enough to throw the feature tracking into a wobble or not...
cheers,
Robin
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Re: Keeping a Planet Aligned while Imaging
Excellent clarification. I think I will look into PHD2 guiding when on a planetary target. Seems like the simplest solution...admin wrote: ↑Mon Feb 03, 2025 10:21 am Hi Chris,
I don't think that using those two features together will work out ...
If you set the feature tracking dead zone to be small and the adjustments to be fairly fast/agressive then you might manage to keep the planet cetered with feature tracking and the ROI movements would never kick in
If you have more relaxed feature tracking settings then the movement will build up enough for the ROI adjustment to happen, and that will then convince feature tracking that it's job is done, which then allows more physical drift to build up.
It might just be possible to make the two work if I changed the feature tracking so that it looked at the (Planet center + ROI offset) position rather than just the planet center position. In theory that would allow it to monitor the physical drift on the sensor rather than the drift in the ROI. However, there is a problem - most cameras update the ROI a few frames after the request to change it is sent for high speed imaging - SharpCap doesn't know how many frames later that update will occur and normally it doesn't really matter. If you start taking this approach, it does matter, since in the period between sending an ROI change request to the camera and the frames actually showing the effect, the value of (Planet center + ROI offset) will be incorrect.
Not sure if that last issue would be enough to throw the feature tracking into a wobble or not...
cheers,
Robin
Re: Keeping a Planet Aligned while Imaging
Thanks Robin.
I too was wondering about “absolute” centre (i.e. like your relative centre plus offset). It sounds more complicated with driver uncertainties.
Are you able to poll the camera for its current offset, to monitor where it actually is set?
Cheers, Chris.
I too was wondering about “absolute” centre (i.e. like your relative centre plus offset). It sounds more complicated with driver uncertainties.
Are you able to poll the camera for its current offset, to monitor where it actually is set?
Cheers, Chris.
Celestron EdgeHD 8, reducer 0.7x, Star Sense, CGX-L mount, Focuser, CPWI; Starlight Xpress AO, OAG and Filter Wheel; ZWO 294MC/294MM Pro and 174MM mini; SharpCap Pro, PHD2, Televue Powermate 2x, Baader Neodymium, Astronomik CLS-CCD, ZWO UV/IR, Duo filters
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Re: Keeping a Planet Aligned while Imaging
Hi Chris,
not really - the software on the PC will report the desired offset once the new position has been requested, regardless of whether the camera has actually updated to that position yet, and certainly not taking account of any frames that have already been captured at the old position but are still making their way throught the USB transfer to the computer.
It may be that the best approach would be to do something like ignore all position information from frames for 1s after the ROI position changes - that hopefully would mean that any frames for which the position was uncertain would be ignored anyway, so not impact the feature tracking. It might work...
cheers,
Robin
not really - the software on the PC will report the desired offset once the new position has been requested, regardless of whether the camera has actually updated to that position yet, and certainly not taking account of any frames that have already been captured at the old position but are still making their way throught the USB transfer to the computer.
It may be that the best approach would be to do something like ignore all position information from frames for 1s after the ROI position changes - that hopefully would mean that any frames for which the position was uncertain would be ignored anyway, so not impact the feature tracking. It might work...
cheers,
Robin
Re: Keeping a Planet Aligned while Imaging
Hi Robin,
I realise that with Planetary Stacking there is a third “centring” option. If I use Feature Tracking of COG of planet, and then enable centring in the Planetary Stacking, that should achieve both tracking and centring in the stacked frame.
Does that make sense now?
Cheers, Chris.
P.S. sorry for hijacking the thread …
I realise that with Planetary Stacking there is a third “centring” option. If I use Feature Tracking of COG of planet, and then enable centring in the Planetary Stacking, that should achieve both tracking and centring in the stacked frame.
Does that make sense now?
Cheers, Chris.
P.S. sorry for hijacking the thread …
Celestron EdgeHD 8, reducer 0.7x, Star Sense, CGX-L mount, Focuser, CPWI; Starlight Xpress AO, OAG and Filter Wheel; ZWO 294MC/294MM Pro and 174MM mini; SharpCap Pro, PHD2, Televue Powermate 2x, Baader Neodymium, Astronomik CLS-CCD, ZWO UV/IR, Duo filters
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Re: Keeping a Planet Aligned while Imaging
Hi Chris,
I don't think so sadly - once again with this configuration, the COG calculation will reflect the COG within the current ROI. Feature tracking will not take any notice of the ROI having changed, so when the ROI moves to bring the planet back to near the center of it, feature tracking will take no action to try to correct the physical drift that is happening.
sorry,
Robin
I don't think so sadly - once again with this configuration, the COG calculation will reflect the COG within the current ROI. Feature tracking will not take any notice of the ROI having changed, so when the ROI moves to bring the planet back to near the center of it, feature tracking will take no action to try to correct the physical drift that is happening.
sorry,
Robin
Re: Keeping a Planet Aligned while Imaging
Hi Robin,
Sorry, I used the wrong terminology. I meant using Feature Tracking of the mount to keep the planet centred, and then centring in the planetary stacking. So no changes of the camera ROI.
Cheers, Chris.
Sorry, I used the wrong terminology. I meant using Feature Tracking of the mount to keep the planet centred, and then centring in the planetary stacking. So no changes of the camera ROI.
Cheers, Chris.
Celestron EdgeHD 8, reducer 0.7x, Star Sense, CGX-L mount, Focuser, CPWI; Starlight Xpress AO, OAG and Filter Wheel; ZWO 294MC/294MM Pro and 174MM mini; SharpCap Pro, PHD2, Televue Powermate 2x, Baader Neodymium, Astronomik CLS-CCD, ZWO UV/IR, Duo filters
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Re: Keeping a Planet Aligned while Imaging
Hi Chris,
yes, that should work, because the feature tracking looks at the frame straight off the camera, before the planet centering has a chance to adjust the image.
cheers,
Robin
yes, that should work, because the feature tracking looks at the frame straight off the camera, before the planet centering has a chance to adjust the image.
cheers,
Robin