Polar Alignment at long focal length - 2500mm

Using SharpCap's Polar Alignment feature
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dhess62
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Polar Alignment at long focal length - 2500mm

#1

Post by dhess62 »

Does Sharpcap do well with polar alignment on a long focal length scope like 2500mm?
It seems like plate solving is an issue with other software at this focal length.

I have a 10" Meade SCT and using the ASI294MC Pro camera so my field of view is only 0.43° x 0.29°

Thanks in advance.
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admin
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Re: Polar Alignment at long focal length - 2500mm

#2

Post by admin »

Hi,

sadly your field of view is too small for the polar alignment to work reliably (or even at all). The FOV needs to be 0.5 degrees in each direction minimum.

A 0.5x reducer might give you enough FOV, although there could be issues if it introduces significant distortion to the view, and anyway it might struggle to illuminate the whole sensor area. I don't think a 0.66x reducer would be enough reduction.

To be honest, the most reliable way to get it working would be to add a 200mm focal length guide scope to your setup with a guide camera. It's also a cheaper option than trying to upgrade to a camera with a big enough sensor to give 0.5x0.5 degrees at 2500mm (tempting though a bigger camera might be!)

cheers,

Robin
dhess62
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Joined: Wed Jul 28, 2021 8:33 pm

Re: Polar Alignment at long focal length - 2500mm

#3

Post by dhess62 »

Since I use an OAG and don't want to add anything else on the main scope, is something like the iOptron iPolar or QHY Polemaster my next best option?
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Re: Polar Alignment at long focal length - 2500mm

#4

Post by admin »

Hi,

both of those should work (and, as a bonus, both can be used with the SharpCap alignment routine, which I'm told is easier to use than the iPolar/polemaster ones).

cheers,

Robin
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