[JA]

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