I have searched, I really have, and cannot find any description of the new feature "Offset the mount position to recenter target". And when to use it versus "Sych mount and re-center target". Could someone please explain?
Also, in general when new features are added to Sharpcap when are they added to the Sharpcap manual?
Thanks!
New Offset mount & recenter feature
Forum rules
If you have a problem or question, please check the FAQ to see if it already has an answer : https://www.sharpcap.co.uk/sharpcap-faqs
If you have a problem or question, please check the FAQ to see if it already has an answer : https://www.sharpcap.co.uk/sharpcap-faqs
-
admin
- Site Admin
- Posts: 13330
- Joined: Sat Feb 11, 2017 3:52 pm
- Location: Vale of the White Horse, UK
- Contact:
Re: New Offset mount & recenter feature
Hi,
the updated version of the manual typically gets written later – after the features are complete and the new version is fully released. I do try to put up some introductory documentation for each major new feature, but the one you are interested in didn't make the cut for that to happen.
The old behaviour in SharpCap 3.2 was to send a synchronisation command to the mount for the position that came out of the plates solving calculations and then to send a go to command the mount to go back to the original target location, which should send to your target in the image. This works nicely if you are using a simple pointing model for your Ascom mount, but if you have set up a more complicated pointing model where you have deliberately synchronised the mount at various points across the sky to let the Ascom driver know about the pointing behaviour of the mount as it moves around then it can cause issues.
The new alternative works in a slightly different way – calculate the location in the sky that you are pointing at using the plate solving program, then work out how far off you are from your target (the offset), then issue a new go to command to the mount that takes account of the offset – the coordinates sent to the mount will not be the coordinates of your target, but they should put target in the middle of the field-of-view.
The advantage of the new approach is that it doesn't send a synchronisation command to the mount. The disadvantage is that unlike the old approach, running it a second time will not improve the results – instead it will send you off to somewhere else in the sky that is definitely the wrong position.
Hope this helps, Robin
the updated version of the manual typically gets written later – after the features are complete and the new version is fully released. I do try to put up some introductory documentation for each major new feature, but the one you are interested in didn't make the cut for that to happen.
The old behaviour in SharpCap 3.2 was to send a synchronisation command to the mount for the position that came out of the plates solving calculations and then to send a go to command the mount to go back to the original target location, which should send to your target in the image. This works nicely if you are using a simple pointing model for your Ascom mount, but if you have set up a more complicated pointing model where you have deliberately synchronised the mount at various points across the sky to let the Ascom driver know about the pointing behaviour of the mount as it moves around then it can cause issues.
The new alternative works in a slightly different way – calculate the location in the sky that you are pointing at using the plate solving program, then work out how far off you are from your target (the offset), then issue a new go to command to the mount that takes account of the offset – the coordinates sent to the mount will not be the coordinates of your target, but they should put target in the middle of the field-of-view.
The advantage of the new approach is that it doesn't send a synchronisation command to the mount. The disadvantage is that unlike the old approach, running it a second time will not improve the results – instead it will send you off to somewhere else in the sky that is definitely the wrong position.
Hope this helps, Robin
Re: New Offset mount & recenter feature
Thanks Robin. That really helps explain it. I think in the last sentence you meant to say "disadvantage", but I get it.
Thanks for the quick reply.
Randy
Thanks for the quick reply.
Randy
-
admin
- Site Admin
- Posts: 13330
- Joined: Sat Feb 11, 2017 3:52 pm
- Location: Vale of the White Horse, UK
- Contact:
Re: New Offset mount & recenter feature
Hi Randy,
you're quite right – that should have been disadvantaged. I've edited it
One other point to note is that the offset approach will not work very well near the poles, as the calculations do not take account of the effects of spherical geometry. I would imagine that as long as the size of the offset is considerably less than the distance from the pole then you will be okay (for instance 1° offset, 5° from the pole). However if the size of the offset is compatible to all great distance from the pole, the results will probably be significantly out.
Cheers, Robin
you're quite right – that should have been disadvantaged. I've edited it
One other point to note is that the offset approach will not work very well near the poles, as the calculations do not take account of the effects of spherical geometry. I would imagine that as long as the size of the offset is considerably less than the distance from the pole then you will be okay (for instance 1° offset, 5° from the pole). However if the size of the offset is compatible to all great distance from the pole, the results will probably be significantly out.
Cheers, Robin