PA with smaller FOV?

Using SharpCap's Polar Alignment feature
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RazvanUnderStars
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Joined: Sat Aug 25, 2018 11:11 pm

PA with smaller FOV?

Post by RazvanUnderStars » Tue Aug 06, 2019 5:34 am

I currently use an 8" SCT with a 0.63x reducer and an ZWO ASI294 MC Pro camera (no other camera). FOV is 0.86 deg x 0.58 deg, smaller than the required FOV listed as between 1 and 2.5 deg on each side as per https://www.sharpcap.co.uk/sharpcap/fea ... -alignment. It still works very well.

I'm considering changing the OTA to an EdgeHD 11" with the 0.7x reducer which gives an FOV of 0.56 deg x 0.38 deg. Smaller than the above. I'm concerned it will really prevent me from doing a PA with SharpCap.

Has anyone managed to do PA with a similar FOV? Also, the fact that it already worked with a smaller FOV than formally required, has the PA routine improved since that requirement was written and therefore can work with a smaller FOV?

Thanks!

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Re: PA with smaller FOV?

Post by admin » Wed Aug 07, 2019 3:27 pm

Hi,

The polar alignment routines have been improved since the initial recommendations to have at least one degree in each direction. There is now a very good chance of it working properly with .5° field of view in each direction. However, as the field of view shrinks there is an increasing chance of ending up with the camera pointing at an area where there are insufficient bright stars in the polar alignment database for the plate solving routine to work. As the field of view decreases this problem – which will show up as a failure to plate solve – becomes more and more likely.

Cheers, Robin

RazvanUnderStars
Posts: 11
Joined: Sat Aug 25, 2018 11:11 pm

Re: PA with smaller FOV?

Post by RazvanUnderStars » Thu Aug 08, 2019 12:37 am

Thank you. I also heard from another observer that it works very well with just about 0.5 deg.

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