what is the magnification of a telescope without any eyepiece

Started 7 months ago | Questions thread
Jon555 Veteran Member • Posts: 7,238
That's slightly complicated...

If you just attach a camera then it's the same as a lens, so a 600mm focal length telescope is the same as a 600mm camera lens for what you see. As to resolution that depends on the camera sensor size, MP count and Telescope quality.

With Barlows it depends where you put them. My 2x Barlow becomes 3.5x if I move it about in the chain of stuff between the Telescope and the Camera. So for my colour Moon photo I went:

Scope-Barlow-Diagonal-2" Extension Tube-T2 wide adaptor-T2 to EOS adaptor-Camera

(I needed the diagonal and extension tube to get enough back-focus.)

Which gave about 2200mm equivalent, and the light was spread out so much (f/6.6 Telescope) I needed ISO1600 and stacked the images to get a good result. Placed after the diagonal the Barlow would be about 2x.

For a sanity test the Moon is about 0.516 of a degree across (varies somewhat as its orbit isn't circular). So for example in my image it was about 53.5% of the image width, so giving a horizontal FoV of about 0.96 degrees and so a equivalent focal length (as was an FF camera) of around 2200mm.

Oh and remember you'll need to flip stuff shot in a Telescope to give a right-way-up look (or if you forget people will just assume you're in Australia/similar).

You can just use the focal length/50 for approximate magnification, but as you are unlikely to use the image uncropped it's a bit meaningless.

 Jon555's gear list:Jon555's gear list
Nikon Coolpix 950 Fujifilm FinePix Real 3D W3 Sony RX100 V Canon EOS 5DS R Panasonic GH5 +31 more
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