What is minimum FOV for Polar Alignment

Using SharpCap's Polar Alignment feature
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jpops50
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What is minimum FOV for Polar Alignment

Post by jpops50 » Mon Aug 28, 2017 12:25 am

I am using a Celestron 8HD with a 2032mm focal length and a Celestron Skyris 236c camera. I believe my FOV dimensions are 0.153 x 0.096 degrees. This is much smaller than stated in the requirements to use the Polar Alignment in SharpCap. Will this possibly work or is their anything additional I can do. I have not tried to use the SharpCap polar alignment yet and since I am in Houston Texas (Hurricane Conditions) I will not be seeing the night sky for several nights to come but I would like to know what I can do to improve my chances or if it is even possible to use the polar alignment in SharpCap.

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Re: What is minimum FOV for Polar Alignment

Post by admin » Mon Aug 28, 2017 9:23 am

Hi,

I'm afraid this FOV is much too small for polar alignment to work - the database of stars that SharpCap uses only goes down to about Mag 13 or so and there are just not enough stars of Mag 13 or brighter in your FOV for the polar aligning to work - you typically would need about 10 stars per FOV and I'd expect you'd be lucky to find 1 or 2 at that size :(

Some people have had success with focal reducers, but even a 0.3x focal reducer would still put you below the minimum recommended FOV and distortion might be a problem too, so I doubt that would work.

The best bet would be to use a 200mm finder/guider scope which should work well with your camera's sensor size I think. You can get 'no-brand' versions fairly cheaply (basically equivalent to the Orion version - http://www.telescope.com/Telescopes/Gui ... /99607.uts) or somewhat better ones (sharper stars) like the Altair model (https://www.altairastro.com/starwave-50 ... nator.html) - Not sure if you will find the Altair in the USA, but most likely someone will sell an almost equivalent model with a different brand on it :)

cheers,

Robin

jpops50
Posts: 2
Joined: Sun Aug 27, 2017 11:51 pm

Re: What is minimum FOV for Polar Alignment

Post by jpops50 » Tue Aug 29, 2017 9:46 pm

Robin,

Thank you for the response. You confirmed my suspicion. I will look into your suggestion of getting a finder/guide scope that will work.

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