Go Back   IceInSpace > Equipment > Astrophotography and Imaging Equipment and Discussions

Reply
 
Thread Tools Rate Thread
  #1  
Old 15-08-2018, 07:51 PM
Bart's Avatar
Bart
Don't have a cow, Man!

Bart is offline
 
Join Date: Apr 2013
Location: Adelaide, South Australia
Posts: 1,088
Why halos on bright stars with green and OIII only?

As per the title, I seem to be getting halos around bright stars with the Baader 36mm unmounted green filter and the 12nm QHY OIII filter in the 36 unmounted. None of the others show it. Also, I never seemed to get any halos with the QHY LRGB filters that I just replaced.

I have heard and read on the Baader site to turn the filters against the arrows that are on the edge to combat halos and was wondering if anyone has had any experience with this?
Reply With Quote
  #2  
Old 15-08-2018, 08:23 PM
Atmos's Avatar
Atmos (Colin)
Ultimate Noob

Atmos is offline
 
Join Date: Aug 2011
Location: Melbourne
Posts: 6,980
Not sure if it would be the same for this but I have read that some filters and directional and that it can cause issues if they're placed in the wrong direction.
Reply With Quote
  #3  
Old 15-08-2018, 08:56 PM
Joshua Bunn's Avatar
Joshua Bunn (Joshua)
Registered User

Joshua Bunn is offline
 
Join Date: Oct 2011
Location: Albany, Western Australia
Posts: 1,459
I get green Halos in my RGB captures, they are off putting. I'm currently using Custom Scientific 52mm unmounted filters, so I'm going to watch this thread. Ive also heard the direction they are facing has an effect... but it made no difference to my filters.
Reply With Quote
  #4  
Old 16-08-2018, 05:19 AM
Slawomir's Avatar
Slawomir (Suavi)
Registered User

Slawomir is offline
 
Join Date: Sep 2014
Location: North Queensland
Posts: 3,240
What telescope are you using Bart?

The reason I'm asking is because OIII signal is usually significantly weaker so it often gets stretched more than Ha consequently making halos more visible. A telescope which has noticeable chromatic aberration (achromat, ED doublet) will produce halos around bright stars due to the out of band signal slowly leaking though the filter, even with the best narrowband filters.

Last edited by Slawomir; 16-08-2018 at 06:28 AM.
Reply With Quote
  #5  
Old 16-08-2018, 06:33 AM
Bart's Avatar
Bart
Don't have a cow, Man!

Bart is offline
 
Join Date: Apr 2013
Location: Adelaide, South Australia
Posts: 1,088
I'm using a WO FLT132. I can post some pics tonight if it helps. It is not from false colour, it definitely looks like a reflection issue and is slightly bigger than the star itself.

Last edited by Bart; 16-08-2018 at 07:43 AM.
Reply With Quote
  #6  
Old 16-08-2018, 05:02 PM
Slawomir's Avatar
Slawomir (Suavi)
Registered User

Slawomir is offline
 
Join Date: Sep 2014
Location: North Queensland
Posts: 3,240
Images would certainly help in identifying the cause.

Towards the end of this short review there is a comparison of halos around a bright star from a 12nm OIII and 3nm OIII.
Reply With Quote
  #7  
Old 16-08-2018, 07:36 PM
ericwbenson (Eric)
Registered User

ericwbenson is offline
 
Join Date: Sep 2009
Location: Adelaide, Australia
Posts: 209
Hi Bart,
The filter direction has no effect whatsoever on haloes. I have demonstrated the math on Cloudynights a few times. The intensity of the haloes is linked to the quality of the AR (antireflection) and passband coatings on either side of your filter, and/or the presence of other uncoated/badly coated surfaces in the optical train (e.g. Panasonic 16Mpix CMOS sensor). Unfortunately there is nothing you can do about it except exchange the filter (sorry for the bad news), but maybe it is acceptable?



The direction can impact light leakage from around the edge depending on which side the filter the aperture stop is resting, but that shows up in flats and as bright streaks from stars slightly out of the FOV, different problem from what you are reporting.


Regards,

EB
Reply With Quote
  #8  
Old 17-08-2018, 07:51 PM
Bart's Avatar
Bart
Don't have a cow, Man!

Bart is offline
 
Join Date: Apr 2013
Location: Adelaide, South Australia
Posts: 1,088
Thanks for all your replies and very interesting post, Eric.

From my image cropping, I can see that the halos are on more images than I thought so it is likely that it is a camera of flattener issue perhaps.
Attached Thumbnails
Click for full-size image (Master_B_Crop.jpg)
99.0 KB41 views
Click for full-size image (Master_G_Crop.jpg)
91.5 KB49 views
Click for full-size image (Master_R_crop.jpg)
58.6 KB55 views
Click for full-size image (Master_L_Crop.jpg)
63.0 KB44 views
Click for full-size image (Master_Ha_Crop.jpg)
75.2 KB43 views
Click for full-size image (Master_OIII_Crop.jpg)
97.6 KB47 views
Click for full-size image (Master_SII_Crop.jpg)
164.4 KB44 views
Reply With Quote
  #9  
Old 17-08-2018, 08:07 PM
Slawomir's Avatar
Slawomir (Suavi)
Registered User

Slawomir is offline
 
Join Date: Sep 2014
Location: North Queensland
Posts: 3,240
The second last image with the largest halo looks a bit like there could be some fogging up happening somewhere in the optical path.

Most of the images though show stars that I would normally expect.
Reply With Quote
  #10  
Old 19-08-2018, 08:20 AM
Bart's Avatar
Bart
Don't have a cow, Man!

Bart is offline
 
Join Date: Apr 2013
Location: Adelaide, South Australia
Posts: 1,088
OK, so I'm glad you think it is normal. Maybe I'll do a few more images and then see what happens.
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 03:40 AM.

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