Go Back   IceInSpace > Equipment > Eyepieces, Barlows and Filters

Reply
 
Thread Tools Rate Thread
  #1  
Old 10-08-2020, 03:19 PM
CarlJoseph (Carl)
Registered User

CarlJoseph is offline
 
Join Date: Dec 2009
Location: Dandenong Ranges
Posts: 265
Filter sizes to suit ASI 183MM Pro

Hi everyone,

Am going to buy a monochrome camera so wanting some filters to go with it. Not sure if I can get away with the 1.25" or if I need something larger like the 36mm?

I'm using a Stellarvue SV105 f/6.2, with an ASI 183MM Pro, so wide field. Sensor diagonal is 15.9mm.

I know I can calibrate out any vignetting but want to avoid as much of it as possible in the optical train.

Keen for any thoughts/advice.

Thanks.
Reply With Quote
  #2  
Old 10-08-2020, 04:16 PM
sunslayr (David)
Registered User

sunslayr is offline
 
Join Date: Nov 2018
Location: Perth
Posts: 209
According to Zwo when using their EFW "The distance between the filter and sensor is around 10mm when you connect it to ASI1600.

So 1.25″ filters won’t have vignetting up to F5 focal ratio scope and 31mm filter won’t have vignetting up to F2 lens". So I imagine you should be safe going for 1.25" filters with the 183mm's smaller sensor even if you pick up a reducer later.

edit: This is the the equation for calculating vignetting

Filter distance from sensor / Filter clear aperture - sensor diagonal (26mm for 1.25, 28mm for 31mm)

10mm/(26-15.9) = F0.9 Vignette ratio

Last edited by sunslayr; 10-08-2020 at 04:28 PM.
Reply With Quote
  #3  
Old 10-08-2020, 07:42 PM
CarlJoseph (Carl)
Registered User

CarlJoseph is offline
 
Join Date: Dec 2009
Location: Dandenong Ranges
Posts: 265
Thanks for that.

What's the relationship between the filter size and f-ratio? I'm also going to be getting a RedCat51 (f/4.9) so want to ensure 1.25" are suitable for that too.

Thanks again
Reply With Quote
  #4  
Old 10-08-2020, 07:52 PM
CarlJoseph (Carl)
Registered User

CarlJoseph is offline
 
Join Date: Dec 2009
Location: Dandenong Ranges
Posts: 265
Nevermind, I found the formula ...

Minimum Filter Size = CCDdiag*(FL-ChipDistance)/FL + (ChipDistance/f)

So in both of my set-ups, around 17.2mm is the smallest filter size. Looks like I can safely go the cheaper size then
Reply With Quote
Reply

Bookmarks

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 01:33 AM.

Powered by vBulletin Version 3.8.7 | Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Advertisement
Testar
Advertisement
Bintel
Advertisement