Old 22-07-2017, 11:47 AM
john guy's Avatar
john guy (John)
Registered User

john guy is offline
Join Date: Sep 2007
Location: mcgraths hill australia
Posts: 109
distance formula

can anyone please tell me if a formula is known how to set correct distance between a focal reducer and ccd. set up meade 14'' sct and
meade 6.3 focal reducer with atik 383l ccd
any advise much appreciated
regards J G
Reply With Quote
Old 22-07-2017, 02:13 PM
Atmos's Avatar
Atmos (Colin)
Ultimate Noob

Atmos is offline
Join Date: Aug 2011
Location: Melbourne
Posts: 6,293
Apparently there are two versions of that focal reducer which have two vastly different back focus requirements.


As for calculations.
BF = Back Focus requirement of focal reducer
FIL = Any filter you may have in the optical path
CCD = The back focus consumed by your camera
Spacer = Spacers required

BF+1/3FIL-CCD= Spacer

I was calculating this morning for a Nikon lens with my setup. I'm using Astrodon filters which are 3mm thick so a third of that is 1mm.

46.5(Nikon Lens)+1(filter)-10(M54 Nikon F-Mount)-4(M54 F Thread)-15(Filter Wheel)-10.5(CCD)= 8mm
This means I need an 8mm spacer to get the desired back focus.
Reply With Quote


Thread Tools
Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

All times are GMT +10. The time is now 08:56 AM.

Powered by vBulletin Version 3.8.7 | Copyright ©2000 - 2019, Jelsoft Enterprises Ltd.
OzScopes Authorised Dealer
SkyWatcher Australia
Meade Australia
Celestron Australia
NexDome Observatories
Lunatico Astronomical
Astronomy and Electronics Centre