Meade f/6.3 Focal Reducer gives some very unexpected results

For images of members equipment (no way to describe it without double entendres!)

Re: Meade f/6.3 Focal Reducer gives some very unexpected res

Postby Silversmith » Fri Mar 30, 2018 9:08 pm

This is a very useful site, with formula and a quick calculator for working out the resulting f ratio and combined focal length when a reducer is added into the optical train for either a refractor or a SCT. Scroll down for the reducer formulae. .

The thing I found hardest was to determine the Focal length of the reducer ... I've many different numbers published for the same reducer ! Best to measure it yourself.

The formulae can be used to either work out what f number you are getting with the air gap you have (often its not possible to get the 'ideal') but the reducer will still work with a wide variation of gaps, but deliver different f Numbers. The design aim of both the Celestron and Meade (and Antares which I have) is to deliver a f6.3 result.... but the reducer WILL work and deliver other f numbers with different gaps.
Or you can vary the gap in the calculator until you get the desired f number.. thus finding out the gap you need,

My Antares has a focal length of 220 mm, but the 'ideal' 95mm gap is not achievable with my setup .. so I use 105 mm which give me f 6.0 which is fine.

I get some vignetting, but appropriate flats eliminate it (along with the shadow of my Off Axis guider.. which is what stops me achieving a 95mm gap!)

Hi, you are viewing as a guest, You can only see this first post in this topic. if you sign up you get access to other goodies you can't even see as a guest, including video tutorials on imaging and processing, scope modifications and even member discounts on gear!

So, give us a try, what have you got to lose! Oh, and if you stay, when you reach 50 posts you get access to MORE goodies! What are you waiting for!

User avatar
Posts: 135
Joined: Wed May 08, 2013 11:33 am
Location: Burray, Orkney

Re: Meade f/6.3 Focal Reducer gives some very unexpected res

Postby jjb2011 » Sat Mar 31, 2018 1:32 pm

Black Dwarf
Posts: 1280
Joined: Tue Jun 21, 2011 10:21 pm
Location: Ledbury, Herefordshire



Who is online

Users browsing this forum: No registered users and 1 guest