Go Back   IceInSpace > Equipment > Eyepieces, Barlows and Filters

Reply
 
Thread Tools Rate Thread
  #1  
Old 08-08-2017, 11:13 AM
JA
.....

JA is offline
 
Join Date: Oct 2016
Location: Melbourne, Australia
Posts: 1,406
Skyglow / Light Pollution Filter Comparison

Hi Folks,

A quick comparison of 2 filters to help mitigate some of the efffects of urban light pollution and skyglow. Both of the filters are didymium type redhancer filters, available in various sizes typically for camera lens use ( I haven't seen these in 2inch /M48x0.75), but I suspect they are similar to some of those used with conventional telescopes. For these images the camera was positioned some 20 m from the street lamps (High Pressure Sodium Lamps) which were mildly, but not obviously illuminating the top of the tree shown. Other general illumination included several (Compact Fl.) at ~10m. Oh .... and then there was the full moon!

Location was Down town Brighton in Melbourne near the corner of Church and New Street - plenty of High Pressure Sodium lamp illumination! Even with this relatively bright location, one can see the beginnings of the Milky Way just starting to come out in the images where filters were used and even a little more so in the autoenhanced 2nd image as well as a much more dense and defined starfield.

Exposure 20s f2.8 & ISO 800. Image cropped from 24mm f2.8 and then arranged on screen for a triple screenshot (1920 x 1200 and then resized- YUK), since I wanted to get a quick indication of the relative darkness of background for the same exposure with the various filters.

1st image - Left to Right = No Filter/Hoya Intensifier(52mm)/ Marumi Redhancer(55mm) Cropped and arranged as Triple Screenshot 1920 x 1200/resized & otherwise unaltered.

2nd image - Left to Right = No Filter/Hoya Intensifier(52mm)/ Marumi Redhancer(55mm) Cropped and arranged as Triple Screenshot 1920 x 1200/resized & Autoenhanced.


I'd like to redo this at a darker location / time with some of the other brand filters I have: Crystal Optics & Tiffen, subject to finding the right step down rings or kludging something together. I did mean to add the exposure histogram, perhaps next time.

Best
JA
Attached Thumbnails
Click for full-size image (Filter Comparison - None - Hoya - Marumi 2.jpg)
109.1 KB111 views
Click for full-size image (Filter Comparison - None - Hoya - Marumi - Enhanced 2.jpg)
157.4 KB86 views

Last edited by JA; 08-08-2017 at 04:25 PM.
Reply With Quote
  #2  
Old 08-08-2017, 05:37 PM
LewisM's Avatar
LewisM
Novichok test rabbit

LewisM is offline
 
Join Date: Aug 2012
Location: Somewhere in the cosmos...
Posts: 9,247
Nice comparo JA. Must do one myself with the various Skyglow/UHC/LP filters I have (2").
Reply With Quote
  #3  
Old 09-08-2017, 08:40 AM
JA
.....

JA is offline
 
Join Date: Oct 2016
Location: Melbourne, Australia
Posts: 1,406
Quote:
Originally Posted by LewisM View Post
Nice comparo JA. Must do one myself with the various Skyglow/UHC/LP filters I have (2").
Thanks Lewis. I would like to also extend the comparison to some of those astro filters too, but not sure - the 2" filters may just vignette on the 52mm filter thread of the lens I used. EDIT: Just checked - maybe not as the front element is 41mm in diamter and provided filter ring is not too thick it should be OK.

Best
JA
Reply With Quote
  #4  
Old 09-08-2019, 01:55 PM
JA
.....

JA is offline
 
Join Date: Oct 2016
Location: Melbourne, Australia
Posts: 1,406
Here is a comparison of the effect of a wideband Light Pollution (red-enhancing/selective elimination of Sodium Lines) filter: A Marumi Redhancer filter versus No Filter on a modified Nikon D800 in backyard suburbia SQM =18.84 (from LP Map), no moon, just High Pressure Sodium Street lighting washing out our skies in the area. Except for resizing, the image is straight out of camera with no colour correction for the redcast from the modified D800. Exposure 8 seconds @f/2 set to ISO800.

There is a significant increase in contrast - see attached image

It would have been good to do the same comparison with an unmodified D800. Maybe next-time. I find the Marumi brand filter a little better than the Hoya equivalent ("Intensifier")I've tried previously.

Best
JA
Attached Thumbnails
Click for full-size image (No Filter V Marumi Redhancer on Nikon D800 Mofdified 1000x624.jpg)
134.9 KB57 views

Last edited by JA; 09-08-2019 at 02:09 PM.
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 11:21 PM.

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