Jump to content


Photo

Nexstar 4SE and focal reducer ?

  • Please log in to reply
5 replies to this topic

#1 ItsMeTony

ItsMeTony

    Lift Off

  • *****
  • Posts: 5
  • Joined: 21 Feb 2008
  • Loc: Maryland

Posted 12 February 2013 - 03:06 PM

Is there a way to widen the field of view on a Mak like this similar to using a focal reducer does for SCT's? :question:

Thanks,
Tony

#2 Tel

Tel

    Cosmos

  • *****
  • Posts: 9103
  • Joined: 31 Mar 2006
  • Loc: Wallingford England

Posted 12 February 2013 - 03:58 PM

Hi Tony,

A very warm welcome to CN and to this forum in particular. :bow::bow:

If you go to page two of this forum's threads, you'll see one by TRE-BOR entitled "Focal Reducer for Celestron 4SE" which refers to the same question.

Take a look. It should provide the answer you seek.

Best regards,
Tel

#3 ItsMeTony

ItsMeTony

    Lift Off

  • *****
  • Posts: 5
  • Joined: 21 Feb 2008
  • Loc: Maryland

Posted 12 February 2013 - 05:02 PM

Thanks so much Tel.

Clear Skies to you
Tony

#4 Tel

Tel

    Cosmos

  • *****
  • Posts: 9103
  • Joined: 31 Mar 2006
  • Loc: Wallingford England

Posted 14 February 2013 - 04:49 AM

Hi Tony,

Please take note that having recommended you to take a look at "TREBOR'S" same subject thread; "Focal Reducer for Nexstar 4SE", it seems that according to "Barbarosa" (David), the originally advised use of a Meade adapter, doesn't fit. However, if you take another look at this thread, you'll see that further advice is given.

Just to add though, that if you fail to find anything to fit directly to your 4SE, (and I'm sure you will): as an alternative, you might consider something like the X 0.5 Antares focal reducer which screws directly onto your 1.25" EPs or a 1.25" camera adapter ?

For example:

http://www.scopesnsk...ducer/0.5x.html

Note that this firm's supply of these reducers is temporarily out of stock but other outlets will have them.

Also note that these are low priced because they are not combined "field flatteners"; a feature however which is probably less relevant when using slow focal ratio 'scopes such as yours. In theory these units should reduce your focal ratio to ca. f/6.5 but in my experience with admittedly a Nexstar 8i OTA and a f/5.9 refractor, I think the figure is nearer to only 35%. There are of course other EP/camera adapter "screw on" reducers available.

Hoping this helps,

Best regards,
Tel

#5 barbarosa

barbarosa

    Viking 1

  • -----
  • Posts: 863
  • Joined: 11 Apr 2010
  • Loc: "lamorinda", CA

Posted 14 February 2013 - 12:42 PM

Tel/Tony-

The .5x reducer will work. The exact amount of reduction varies with the spacing from the focal plane. The product info for the Antares reducer explains this.

I've found that with the EPs (and with the video cameras) that I have, that putting the reducer on the end of the c-mount adaptor or the EP provides less than a .5 reduction. Adding a small spacer (a filter for example) between the reducer and the c-mount adapter/EP increases the reduction by a useful amount.

#6 Tel

Tel

    Cosmos

  • *****
  • Posts: 9103
  • Joined: 31 Mar 2006
  • Loc: Wallingford England

Posted 14 February 2013 - 01:31 PM

Hi David,

Many thanks for the comment. That seems to support my experience of a less than 50% reduction. I have never tried using a spacer though to redress the loss.

Best regards,
Tel






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics