Go Back   IceInSpace > Equipment > ATM and DIY Projects

Thread Tools Rate Thread
Old 11-12-2018, 09:03 PM
Stonius's Avatar
Stonius (Markus)
Registered User

Stonius is offline
Join Date: Mar 2015
Location: Melbourne
Posts: 971
How hard is it to grind a mirror to exact Focal Length?

Any instrument makers out there?

I wonder how hard it is to grind a mirror to an exact focal length?

I'm curious because I have an RC scope where the primary-secondary spacing is critical (to the mm).

If I platesolve an image to derive the focal length, do I adjust the mirror spacing to put it in line with the specs? Or do I assume that there is some variability in mirror production and this is normal as long as images are good? Or that the platesolver is approximate, not exact?


Reply With Quote
Old 11-12-2018, 09:08 PM
Lognic04's Avatar
Lognic04 (Logan)
Registered User

Lognic04 is offline
Join Date: Mar 2016
Location: Melbourne, VIC
Posts: 880
For a dob, mirror makers let the FL vary widely. But if one wanted to grind a mirror to a specific spec it wouldn't be hard to get it +/- 5mm with a spherometer and flash polishing.
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 10:45 PM.

Powered by vBulletin Version 3.8.7 | Copyright ©2000 - 2020, Jelsoft Enterprises Ltd.
Lunatico Astronomical
Astronomy and Electronics Centre