#1  
Old 08-02-2014, 07:25 PM
Andy01's Avatar
Andy01 (Andy)
My God it's full of stars

Andy01 is offline
 
Join Date: Mar 2012
Location: Melbourne
Posts: 2,291
True star colours with LP filters

Hi everyone,
Does anyone have a solution for keeping true star colours when using LP filters in the 'burbs?
I use an IDAS filter on my OSC CCD camera and it really messes with the colours. Quite a challenge to process as a result. Thoughts?

Cheers,
Andy
Reply With Quote
  #2  
Old 09-02-2014, 02:52 PM
cometcatcher's Avatar
cometcatcher (Kevin)
<--- Comet Hale-Bopp

cometcatcher is offline
 
Join Date: Jan 2005
Location: Cloudy Mackay
Posts: 6,125
Mmm, the IDAS filters are usually one of the least colour shifted brands.

The Baader Semi-Apo filter is pretty good with minimal shift as should be the Moon and Skyglow filter. The more narrow band the LP filter the more colour shift. Something has to give with big chunks of the spectrum taken out. Usually LP filters are for nebula with the stars and their colour being sacrificed to some extent.
Reply With Quote
  #3  
Old 10-02-2014, 04:00 PM
SimmoW's Avatar
SimmoW (SIMON)
Farting Nebulae

SimmoW is offline
 
Join Date: Jan 2014
Location: Tamleugh, Victoria, Australia
Posts: 1,335
Hey Andy, couldn't you just note what main stars were white and then just do a white balance adjustment against that star in PS later? Or is it harder than it sounds?!
Reply With Quote
  #4  
Old 10-02-2014, 04:27 PM
alistairsam's Avatar
alistairsam
Registered User

alistairsam is offline
 
Join Date: Nov 2009
Location: Box Hill North, Vic
Posts: 1,817
I have an IDAS LPS-P2 and the colours are well balanced and I hardly need to make any adjustments.
I've tried it on a QHY8 OSC, QHY8L OSC and a dslr.
do you have your debayering settings right? what software do you use to process and can you post a raw non-debayered and debayered sub?

Cheers
Alistair
Reply With Quote
  #5  
Old 10-02-2014, 04:47 PM
alistairsam's Avatar
alistairsam
Registered User

alistairsam is offline
 
Join Date: Nov 2009
Location: Box Hill North, Vic
Posts: 1,817
here are two images with a dslr or qhy8, can't remember, but it was an OSC.
60s raw without the IDAS and with the filter.
unprocessed.
Attached Thumbnails
Click for full-size image (eta-noLPfilter.JPG)
116.0 KB43 views
Click for full-size image (eta-LPFilter.JPG)
126.3 KB44 views
Reply With Quote
  #6  
Old 10-02-2014, 05:21 PM
nebulosity.'s Avatar
nebulosity. (Jo)
Registered User

nebulosity. is offline
 
Join Date: Jul 2013
Location: Cecil Plains QLD
Posts: 1,225
Gee that does a great job
Reply With Quote
  #7  
Old 10-02-2014, 07:42 PM
SimmoW's Avatar
SimmoW (SIMON)
Farting Nebulae

SimmoW is offline
 
Join Date: Jan 2014
Location: Tamleugh, Victoria, Australia
Posts: 1,335
Quote:
Originally Posted by nebulosity. View Post
Gee that does a great job
yes that's a great comparison! That'll have to be one of my first accessory purchases.

And strange, doesn't seem to wreck the star colours, not that this is a perfect example.
Reply With Quote
  #8  
Old 11-02-2014, 10:15 AM
alpal's Avatar
alpal
Registered User

alpal is offline
 
Join Date: Jan 2012
Location: Melbourne
Posts: 2,809
Interesting.

I use an Astronomik CLS-CCD 2" filter & seem to get quite good star colours
after balancing the 3 RGB humps in photoshop.
I use it in front of all 5 LRGBHa filters.

see here:
http://www.astronomik.com/en/photogr...cd-filter.html
Reply With Quote
  #9  
Old 11-02-2014, 10:42 AM
cometcatcher's Avatar
cometcatcher (Kevin)
<--- Comet Hale-Bopp

cometcatcher is offline
 
Join Date: Jan 2005
Location: Cloudy Mackay
Posts: 6,125
Could you post an unprocessed example Andrew?
Reply With Quote
  #10  
Old 11-02-2014, 03:20 PM
Andy01's Avatar
Andy01 (Andy)
My God it's full of stars

Andy01 is offline
 
Join Date: Mar 2012
Location: Melbourne
Posts: 2,291
before and after

Hi everyone,
Thanks for your considered replies, sorry to be getting back to you so late

I've attached a before and after post production image of Omega Centauri that I shot a few night ago. 30x5 min RGB from the SBIG 8300c with the IDAS filter in place. (Yes I just missed the focus, d'oh!)

I process with Nebulosity. The first image is basically out of the stack with levels and sharpening applied. The second has been tweaked, massaged leveled and colour balanced as best I can, minimizing the cyan and enhanceing the yellows stars.

It's never going to match the colour result as shooting under dark skies, but I am concerned about the oversaturation of cyan and desaturation of yellow and orange that result from the IDAS - it seems particularly harsh on yellow stars.

Has no-one else encountered this effect?

Cheers

Andy
Attached Thumbnails
Click for full-size image (Omega C IIS copy.jpg)
191.6 KB22 views
Click for full-size image (Omega Centauri_After.jpg)
201.4 KB22 views
Reply With Quote
  #11  
Old 11-02-2014, 03:52 PM
alocky's Avatar
alocky (Andrew lockwood)
PI popular people's front

alocky is offline
 
Join Date: Aug 2010
Location: perth australia
Posts: 1,287
I've noticed exactly the same effect with both DSLR and mono CCD, it's probably because one of the key contributors to light pollution are yellow sodium vapour lamps, and the stars are a continuum source, so it gets hit too.
I've yet to be convinced that anyone can produce nice yellow stars with data from these filters, despite some heroic efforts on this forum.
Cheers,
Andrew
Reply With Quote
  #12  
Old 11-02-2014, 04:42 PM
alpal's Avatar
alpal
Registered User

alpal is offline
 
Join Date: Jan 2012
Location: Melbourne
Posts: 2,809
Using LAB mode in Photoshop I balanced & boosted the colours.
Plenty of yellow came out.

see link for Louie's video:
http://www.youtube.com/watch?v=fE2GS_87Ct8

I don't know Pixinsight but you need to work in the CIELAB colour space.

see pic which is modified from your first pic.
Attached Thumbnails
Click for full-size image (Omega C IIS copy_a.jpg)
171.6 KB20 views
Reply With Quote
  #13  
Old 11-02-2014, 04:49 PM
Andy01's Avatar
Andy01 (Andy)
My God it's full of stars

Andy01 is offline
 
Join Date: Mar 2012
Location: Melbourne
Posts: 2,291
Hey Alpal that's an interesting result.
Hmmm... what was your workflow in PS for that?

cheers

AC
Reply With Quote
  #14  
Old 11-02-2014, 04:50 PM
alpal's Avatar
alpal
Registered User

alpal is offline
 
Join Date: Jan 2012
Location: Melbourne
Posts: 2,809
Quote:
Originally Posted by Andy01 View Post
Hey Alpal that's an interesting result.
Hmmm... what was your workflow in PS for that?

cheers

AC
I just added that info to my post
Reply With Quote
  #15  
Old 11-02-2014, 05:10 PM
alocky's Avatar
alocky (Andrew lockwood)
PI popular people's front

alocky is offline
 
Join Date: Aug 2010
Location: perth australia
Posts: 1,287
That's a significant improvement. I will try that on some of my older data. You can do the same thing in Pixinsight using the curves transformation tool very simply. I've been fixing my reds using this method ever since Alpal demonstrated it on an LMC image.
Thanks for sharing!
Reply With Quote
  #16  
Old 11-02-2014, 05:21 PM
alpal's Avatar
alpal
Registered User

alpal is offline
 
Join Date: Jan 2012
Location: Melbourne
Posts: 2,809
Quote:
Originally Posted by alocky View Post
That's a significant improvement. I will try that on some of my older data. You can do the same thing in Pixinsight using the curves transformation tool very simply. I've been fixing my reds using this method ever since Alpal demonstrated it on an LMC image.
Thanks for sharing!
Thanks.
Yes - there is whole thread about it in this section of the forum:

http://www.iceinspace.com.au/forum/s...d.php?t=116632
Reply With Quote
  #17  
Old 11-02-2014, 05:45 PM
Andy01's Avatar
Andy01 (Andy)
My God it's full of stars

Andy01 is offline
 
Join Date: Mar 2012
Location: Melbourne
Posts: 2,291
Cheers Alpal - gotta love PS - 1000 different ways to do stuff Andy
Reply With Quote
  #18  
Old 11-02-2014, 05:58 PM
alpal's Avatar
alpal
Registered User

alpal is offline
 
Join Date: Jan 2012
Location: Melbourne
Posts: 2,809
Quote:
Originally Posted by Andy01 View Post
Cheers Alpal - gotta love PS - 1000 different ways to do stuff Andy
True -
make sure you thoroughly know all of Louie's videos here:

http://www.youtube.com/channel/UCJ5b...?feature=watch

I consider that everyone of them is essential.
I always work in layers now.

cheers
Allan
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 05:37 PM.

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