View Full Version here: : Filter for galaxies under Mercury Vapour Streetlight pollution
02-07-2011, 05:15 PM
I'm looking at the DGM Optics GCE (galaxy contrast enhancement) filter and the Lumicon Deep Sky filter.
They have similar transmission curves though the GCE lets a bit more of the red end of the sprectrum through and thus more light from galaxies, but it should also let some Na light pollution through too.
Does anyone have experience with either or both of these filters near but not under the direct glare of streetlights when observing galaxies?
I've had great success observing nebulae with UHC/OIII filters in a filter wheel with my C11 - the filter wheel makes a big difference and I consider it an essential piece of equipment now.
02-07-2011, 05:44 PM
I haven't been a visual observer for some years, the site below maybe useful for you. I tried many different filters for galaxies without any success but that was 5 or more years ago. Since galaxies are across a wide spectrum it will be interesting to see if any filter can indeed do anything to enhance them. The cure? A dark sky or make the switch to the dark current as I did.
02-07-2011, 06:00 PM
Thanks Peter. I haven't finished reading the posts at that link but this from David Knisely supports what I see in the transmission graphs:
" From in-town, I found that the Deep-sky filter seemed to provide just
a hair more contrast than the GCE on the galaxies which I have been
testing it on so far. This would seem to support the initial conclusion
that the GCE is not as an effective "light pollution" filter as the
I'd only need a modest boost to make galaxies worth looking at - at the moment I don't bother.
02-07-2011, 06:28 PM
Many years ago (gee I sound old) I tried the Sirius Optics (was sold by us but not made by us) Contrast Enhancement (CE) filter that claimed to improve Galaxy contrast, probably similar filter as above. I thought there was a very, very slight improvement but in reality it was probably just better seeing and contrasty skies. The problem with some of these "specialised" filters is that they are not protected by an overcoating or under glass and a finger print can completely bugger them if you try to clean it.
02-07-2011, 07:36 PM
I got my streetlight types mixed up so I've corrected the thread title. Here's a link to a guy who has streetlights as a hobby :)
The Orion Skyglow gets good reports too and is much cheaper so I may try that for myself.
10-07-2011, 07:45 PM
I don't observe DSO's under light polluted skies, consequently I don't use any "broadband filters". I do own the Sirius Optics Contrast Enhancement filter that Peter mentioned. I haven't used it in at least 8 years.
However, I can pass on some worthwhile information. My friend and US astronomy author Phil Harrington did a filter review for Astronomy magazine in 2004 or 2005. Suffice to say Phil rated the Orion Skyglow as "the pick of the crop" on an overall basis over about 6 other broadband filters, including the DGM VHT (the original name) and the Lumicon Deep Sky. The fact that it is reasonably priced is an added bonus.
10-07-2011, 09:45 PM
Thanks John. I'll get hold of one and report my findings.
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