Corrector/Reducer for classical Cassegrain telescope - Forums

Topic starter

Jun 15, 2023

Hi everyone,

I got a very good mirror set for a classical cassegrain relatively cheap. I wanted to tackle this as my next project and build the telescope around it myself.
Now the question is, if anyone knows if there is a corrector or reducer specifically for classic Cassegrain telescopes? Unfortunately I can't find anything.
I have read before that a corrector for Newtonian telescopes should also work. Is this the case?

Since I primarily do astrophotography, I wonder if it is worth building the telescope if I don't have a corrector afterwards and the stars and the image are not good.

Clear skies,
Konrad

andrea tasselli

Frequent contributor

Jun 15, 2023

What focal ratio is it going to be? That's the key question, specifically I'd like to know wthat are the focal ratios of the primary and secondary to give an idea of what field aberration you'll likely to be facing. And the size of the image plane you're planning to image with.

Konrad Krebs

Topic starter

Jun 15, 2023

Thanks for the reply,

the primary mirror has a focal ration of f4, the focal ration of the complete system will be f12. It has a diameter of 200mm, so focal length of 2400mm.
My goal is to use a APS-C sized sensor, so I guess image plane at least something like 28mm?

andrea tasselli

Frequent contributor

Jun 15, 2023

Konrad Krebs:
Thanks for the reply,

the primary mirror has a focal ration of f4, the focal ration of the complete system will be f12. It has a diameter of 200mm, so focal length of 2400mm.
My goal is to use a APS-C sized sensor, so I guess image plane at least something like 28mm?

So the secondary magnification should be 3 as well as the FR. This gives a nearly diffraction limited field at r=14mm. Unfortunately it has a rather strong field curvature therefore you'd need a field flattener to take advantage of that. To get more details I'd need much more info on the optical layout that you gave me. I'd tend to use a field flattener designed for RCs.

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