Newbie very puzzled about how SharpCap Polar Alignment would work with Celestron CPWI

Using SharpCap's Polar Alignment feature
go4launch
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Re: Newbie very puzzled about how SharpCap Polar Alignment would work with Celestron CPWI

#11

Post by go4launch »

Hello StarManFlorida - I am using the NexStar hand controller. Please let me know if you have any other questions about the process.
StarManFlorida
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Re: Newbie very puzzled about how SharpCap Polar Alignment would work with Celestron CPWI

#12

Post by StarManFlorida »

Go4Launch - I have a question regarding your fine CPWI/Wedge/Sharpcap explanation. At #8 of your explanation, you want the mount altitude to be equal to my latitude. When I do this, my telescope mounted on the NexStar Evolution mounting contacts the base. Am I interpreting your instruction incorrectly ?
go4launch
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Re: Newbie very puzzled about how SharpCap Polar Alignment would work with Celestron CPWI

#13

Post by go4launch »

Hi StarmanFlorida - What you are describing is one of the down sides of the Celestron arm mount design. Depending on the size of the accessories attached to the rear cell, you may or may not be able to point the telescope to the north celestial pole when on a wedge, or point to zenith when used in az/el mode. This was frequently a struggle for me since I was using a somewhat large DSLR for imaging, and depending on the exact RA/Dec setting on the mount, the DSLR would sometimes hit the mount when pointed near the celestial north pole. I would frequently use a 90 degree diagonal on the rear cell, then the DSLR mounted on the diagonal to try to avoid contact with the mount base. That helped a lot. You should also be able to shift the telescope dovetail forward in the mount to get it further away from mount base.

I also often just used a 100-400mm lens connected to the DSLR for imaging, which was smaller than my Celestron 8SE SCT, and didn't have issues with contacting the mount.

These difficulties are some of the reasons I eventually decided to upgrade the mount to a EQ6R. It eventually become too frustrating dealing with the quirks of the Celestron arm design. Before moving on to the EQ6R, I was able to take some very amateur-ish pictures of deep space and our solar system. A few examples are attached taken from my Bortle 7 area. Photos have improved significantly since upgrading the camera from a Canon EOS 40D to a RisingCam IMX571, and the mount from the Celestron arm/wedge to an EQ6R.
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StarManFlorida
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Re: Newbie very puzzled about how SharpCap Polar Alignment would work with Celestron CPWI

#14

Post by StarManFlorida »

Thank you for your information. The problem was not a camera, but the Celestron focuser.
john_robertson1953
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Joined: Sat Oct 01, 2022 6:02 pm

Re: Newbie very puzzled about how SharpCap Polar Alignment would work with Celestron CPWI

#15

Post by john_robertson1953 »

Regarding issue of camera, hitting the mount: I have a Celestron 8 inch alt/az HD SCT with a wedge, and using the X.7 reducer. i’d like to continue to use sharpcap’s, polar alignment routine, as I do with my hyperstar, but the train is too long with the X.7 reducer, hitting the mount before 90 degrees. I could use a 2 inch diagonal right off the OTA, but id have to attach the reducer backwards to the diagonal. Is this gonna be a problem? If not, what adapter would I need to attach to the other end of the reducer to attach the rest of the camera train, and still meet the back focus requirements? Thanks very much with any help that can be provided.
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Re: Newbie very puzzled about how SharpCap Polar Alignment would work with Celestron CPWI

#16

Post by admin »

Hi,

if by 90 degrees you are referring to the rotation around the RA axis, then just rotate as far as you can - that should be fine. Best accuracy comes at 90 degree rotation, but anything from 30 degrees up should work, and from about 45 to 60 should be very nearly as good as 90.

cheers,

Robin
john_robertson1953
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Re: Newbie very puzzled about how SharpCap Polar Alignment would work with Celestron CPWI

#17

Post by john_robertson1953 »

Hi Robin,
By 90 degrees, I’m referring to the initial rough polar alignment, the OTA should be parallel to the arms, pointing at Polaris, within 5 degrees. With X.7 reducer, camera & required back focus, the camera end will hit the mount prior to reaching the 90 degrees. Are you saying something less than 90 degrees is ok at this initial juncture? Thank you for your response.
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Re: Newbie very puzzled about how SharpCap Polar Alignment would work with Celestron CPWI

#18

Post by admin »

Hi,

Ah, sorry, misunderstanding - I was thinking you referred to the rotation of 90 degrees about the RA axis that you do between the first and second stages of polar alignment.

You do need to get within 5 degrees of the pole for the alignment to work, so you have to be at Dec=+90 (or very close, or -90 for southern hemisphere...). There isn't a way around that I'm afraid.

cheers,

Robin
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