Jump to content


Photo

Focal reducer for small Mak

  • Please log in to reply
4 replies to this topic

#1 RobertJ

RobertJ

    Lift Off

  • -----
  • Posts: 6
  • Joined: 06 Oct 2007

Posted 26 March 2013 - 09:41 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

#2 bykhed

bykhed

    Viking 1

  • *****
  • Posts: 792
  • Joined: 22 Oct 2007
  • Loc: Westminster, CO

Posted 26 March 2013 - 10:01 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

#3 RobertJ

RobertJ

    Lift Off

  • -----
  • Posts: 6
  • Joined: 06 Oct 2007

Posted 26 March 2013 - 10:17 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?

#4 bykhed

bykhed

    Viking 1

  • *****
  • Posts: 792
  • Joined: 22 Oct 2007
  • Loc: Westminster, CO

Posted 27 March 2013 - 03:06 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.

#5 Mike7Mak

Mike7Mak

    Apollo

  • *****
  • Posts: 1277
  • Joined: 07 Dec 2011
  • Loc: New York

Posted 27 March 2013 - 05:04 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).






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics