Which telescope to buy? This may help.

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SunsetTwilight
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Which telescope to buy? This may help.

Post by SunsetTwilight »

Hi everyone,
I saw this post and thought it might be helpful to others 😊
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michael feist
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Re: Which telescope to buy? This may help.

Post by michael feist »

Spotting scopes etc; It would seem that most of the Celestron range are currently 'out of stock' and there does still does seem to be a general shortage of the usual 'scopes' presumably due to distributional problems from China [?], there is a number of other ranges / makes that I have never come across before. I particularly noticed the 'Gosky' or 'GoSky' [?] range of spotting scopes listed on the Internet, as possibly a good medium range [cost wise] alternative. Has anyone here tried any of these? regards maf
brian livesey
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Re: Which telescope to buy? This may help.

Post by brian livesey »

Gosky sounds Russian like Gorky. It’s a company in America.
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michael feist
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Re: Which telescope to buy? This may help.

Post by michael feist »

Thank you for that. They seem available from Amazon. regards mike
michael feist
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Re: Which telescope to buy? This may help.

Post by michael feist »

Noticed that Amazon still had a few Celestron Ultima 65mm zoom spotting scopes [18x minimum magnification.] with 45 degree eyepiece. About 11 years ago I did have one of these which was good at the lower magnifications, so sent for one, 'Next day delivery' and used it this morning. It fills the gap that currently existed between my 80mm Hawke zoom spotter [an excellent scope, but sometimes a bit chunky] and 8x42 monocular. [amended from duplicated entry on 11th April] regards maf.
JohnM
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Re: Which telescope to buy? This may help.

Post by JohnM »

It is not clear if the Schmidt - Cassegrain telescope (SCT) in the illustration is on a wedge but you need one for astro imaging otherwise you get field rotation with RA-Dec mounts.

The other problem with SCTs is that they have long focal lengths and thus small fields of view so are Ok for small objects like planets but not much use for anything larger than perhaps 1/4 degree. They also suffer from the focus changing due to mirror flop as the altitude changes.
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brian livesey
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Re: Which telescope to buy? This may help.

Post by brian livesey »

A focal reducer can be used with an SCT John. Apparently, this type of ‘scope needs a longer cool down time than for a Newtonian.
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JohnM
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Re: Which telescope to buy? This may help.

Post by JohnM »

I agree Brian but it only reduces the focal length to 63% of the native focal length. So an 200mm f10 sct with a focal length of 2m becomes 1.3 m with a f6.3 focal length reducer.

For larger SCTs which are still f10 the field of view is even smaller.

Some SCTs allow a camera to be put in place of the secondary and typically become something like a f2.2 with a wide field of view. However there have been reports that aligning the camera is quite a challenge. The camera also needs to be as small as possible as it sits in the light path but with a large chip. Also the camera power & data cables give you diffraction spikes that may or may not be desirable depending on your views.

John
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