Quote:
Originally Posted by mangrovedutch
Sorry to jump in. I too have thought about an O3 filter or a UHC filter. Which is your recommendation? I don't suffer too much in the way of light polution. I've read up on both and they seem similar in a lot of ways (UHC offers Hydrogen Alpha). Initially I would use it for visual purposes, but want to use it for photography as well. Any advice recommended is muchly appreciated.
Dutch
|
Hi Dutch,
From information I've gathered, the type of filters mentioned in this thread are really only good in large aperature scopes. The reason is that they do block a significant amount of light in order to let in the important and much desired tuned wavelengths such as OIII etc...These wavelengths are but a fraction of the overall spectrum of light entering the scope unfiltered. Therefore, the views do look somewhat dimmer but have more contrast and specific OIII, H-beta, H-Alpha and SII wavelengths are more pronounced using filters that enhance such wavelengths.
There are versions of these filters that are made for photographic and visual use. The photographic versions are not really suited for visual use.
You should take this into account when making a purchase.
Photographic versions have a narrower bandpass that are tuned to to allow more precise spectral bandpass/wavelengths through, this allows even less light from other wavelengths through and so, a long type exposure CCD imaging is required to develop a decent outcome/view. The image/recorded view results of such filters are more defined than wider bandpass visual counterparts, and look more defined and more contrasty
In the end you really need to do some research on different manufacturers' filter products by looking at there product data sheets. The reason being is that not all are the same. Some say they have broad bandpass filtering characteristic and some say the same but, bandpass is narrower/wider than others in their class/design. This could make a significant difference according to your application.
If you are asking is there a good priced, general purpose type nebula/OIII with H-beta enhancement for visual use etc..., then I would go with either:
GSO Broadband, Nebula filter with light pollution and skyglow filtering
or
GSO OIII filter - narrow band, ultra high contrast (UHC), has emission and planetary nebulae peaks; OIII and H-beta enhancement
or
GSO UHC filter - narrowest passband of GSO filters, for best results when viewing ring nebulae and most planetary nebulae, 500nm centred
The last two are recommended really for photographic use because they are narrowband filters.
These GSO filters are very cost-effective but, unfortunately only come in 1.25" at Andrew's here in Australia. I think GSO only make these in 1.25" from what I can gather on their website. I have heard they do a great job though and, are very decent quality.
If you want to go 2" with another well known range of brand names, then PM me and I'll send you a link. This supplier has the best prices I've found on filters. Postage is very cost-effective too. They are in the USA. I don't want to post it here in case it violates the forums rules you understand.
If anyone is interested, I have a thread on a project I'm working on. Using LCD screens as a Digital Optical Filter for a scope. Primarily designed as a colour filtering system to replace screw-on colour scope filters, in Theory virtually any wavelength/bandpass as small as 0.00002086nm can be blocked or filtered for visual and photographic use. You may want to check it out. It's in the ATM/DIY section.
Hope that all helped a little
