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Equipment Discussions >> Cats & Casses

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RobertJ
journeyman


Reged: 10/06/07

Focal reducer for small Mak new
      #5757916 - 03/26/13 10:41 AM

Hi,
I'm looking for a small scope that will be used for astronomy at night (mostly Moon & Planets, a little DSLR AP) & birding during the day.
(origional thread)

I was thinking that a 90-127mm Mak would be great for the astronomy part and, with a 6.3 focal reducer, give me a wide enough FOV during the day.

I have a focal reducer that suited my old 8'' Celestron. will this fit smaller Maks too?

Thanks,
Robert


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bykhed
scholastic sledgehammer
*****

Reged: 10/22/07

Loc: Westminster, CO
Re: Focal reducer for small Mak new [Re: RobertJ]
      #5757948 - 03/26/13 11:01 AM

It will likely work, but you may have significant vignetting of the view due to the small diameter of the baffle tube on the Mak. I prefer using a Mak for planetary/Lunar observing and a small ED refractor for wide-field. So if I'm to a rural location with dark skies I'll take the refractor, but for urban observing I'll use the Mak.

-Matt


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RobertJ
journeyman


Reged: 10/06/07

Re: Focal reducer for small Mak [Re: bykhed]
      #5757980 - 03/26/13 11:17 AM

Two scopes are not an option at the moment.

Is there anywhere I can see a simulation of the vignetting?
Especially for day-time viewing?


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bykhed
scholastic sledgehammer
*****

Reged: 10/22/07

Loc: Westminster, CO
Re: Focal reducer for small Mak new [Re: RobertJ]
      #5760697 - 03/27/13 04:06 PM

I have owned a variety of Maks, and can assure you that the clear aperture of small Maks is tiny. I don't have a simulation but the vignetting will occur when the eyepiece field stop exceeds the diameter of the baffle tube. Hence the FOV will be limited regardless of whether you use a FR or not. I think you would have good results with 5" of aperture or more. A C5 would be a better choice than a Mak if you want a wider FOV.

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Mike7Mak
Pooh-Bah
*****

Reged: 12/07/11

Loc: New York
Re: Focal reducer for small Mak new [Re: bykhed]
      #5760944 - 03/27/13 06:04 PM

Most .63 reducers were designed with field correction that maks don't need and are mounted in SCT-thread housings which I'm pretty sure won't thread on the small maks visual back (different thread).

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