#1  
Old 10-09-2014, 08:28 PM
pluto's Avatar
pluto (Hugh)
Astro Noob

pluto is offline
 
Join Date: Dec 2011
Location: Sydney
Posts: 1,982
OIII 8.5nm vs 3nm under full moon

Just got my Astrodon 3nm OIII filter today so I'm giving it a go tonight.
Just to see the difference under matching conditions I left the old 8.5nm OIII filter in the wheel and did a couple of images to compare.
I did a 30 minute exposure with each.

The first image shows both images with the same histogram stretch applied to both. The 3nm is on the right.

The second image shows both images with an auto screen stretch applied to both. Again the 3nm is on the right.

Interesting?


P.S. I know that 3nm image is out of focus, I've fixed that now
Attached Thumbnails
Click for full-size image (OIII_comp1.jpg)
193.5 KB350 views
Click for full-size image (OIII_comp2.jpg)
195.1 KB358 views
Reply With Quote
  #2  
Old 11-09-2014, 07:43 AM
SamD's Avatar
SamD (Sam)
Registered User

SamD is offline
 
Join Date: Jan 2014
Location: Brisbane SW
Posts: 71
Yes Hugh, you ought to see a decent SNR improvement going from 8.5 to 3nm.

Annoyingly though, you lose the 495.9nm OIII line on the 3nm filter, but this is normally only about a third the strength of the main OIII line intensity.
Attached Thumbnails
Click for full-size image (EmissionLinesRelativeIntensities.jpg)
94.6 KB97 views
Reply With Quote
  #3  
Old 11-09-2014, 03:35 PM
pluto's Avatar
pluto (Hugh)
Astro Noob

pluto is offline
 
Join Date: Dec 2011
Location: Sydney
Posts: 1,982
Yeah I'd read that before I went for the 3nm. I think it's a good trade off given the ridiculous light pollution where I do a lot of my NB imaging.

I've decided to go with 5nm Ha though instead of the 3nm so I can keep the NII light.
Reply With Quote
  #4  
Old 26-09-2014, 06:32 AM
antimorris (Anna)
Registered User

antimorris is offline
 
Join Date: Sep 2014
Location: Raleigh, NC, USA
Posts: 9
I am considering splurging to go from the 12nm to the 3nm despite the loss of the 495.9nm for this very reason. The difference, I imaging, would be even more pronounced with the larger spread of the 12nm that I have. It is nice to see the comparison, thanks for posting it!
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 08:07 PM.

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