Nebula filters: which and how much?

bojan · #1 16-10-2007, 01:20 PM

I am considering the nebula filter, after a losing battle over LP here in Mt Waverley

Could someone recommend something good and affordable? (Baader UHC-S ?)
I believe Steve (Janoskiss) is an expert here

Rodstar (Rod) · #2 16-10-2007, 02:05 PM

Bojan,

I have a 2" UHC filter for sale in the IceTrade section, you may wish to look at.

bojan · #3 16-10-2007, 02:27 PM

Hi Rod, thanks for the offer..
However, I have 1 1/4" eyepieces so this one is too big (it may be useful for photography, though... maybe.. will think about it .....)

MortonH · #4 16-10-2007, 05:51 PM

I think the rule of thumb is that you need a reasonably dark sky for the UHC to be at its best, and that a more general 'light pollution' filter may be better for suburban skies.

I have used the Lumicon Deep Sky filter in the past and it works well on some objects from suburban skies.

Another version is the Astronomik CLS filter (sold by Bintel) or the Orion SkyGlow (not sure if it's sold in Aust).

Morton

astro_nutt · #5 16-10-2007, 07:20 PM

Hi bojan..I use an Astronomik UHC-E (narrowband) for viewing Nebula's through my Saxon 10" from the Suburbs with good results..I'm thinking of getting the CLS (broardband) for star clusters..etc
Cheers!

wavelandscott (Scott) · #6 16-10-2007, 09:16 PM

Interesting topic...

While I am not an expert, I do have some experience on this topic...I have an Astronomics CLS filter, I have owned an Astronomics UHC, and I currently own both a DGM Optics NPB and OIII...

My first bit of advice is to go to Cloudy Nights website and read everything you can written by David Knisely (my apologies if I am getting his name wrong)...he is from Neb. in the US and I have found him to have more helpful insight and good advice than I have been able to find elsewhere.

My own experiences are as follows...

Like many, I live in an area that has more light pollution than I wished and had hoped that a filter would solve the problem for me and let me see nebulae and other Deep Sky Stuff from my backyard...wrong...there is no filter that can replace a dark sky (period).

Okay having helped set/lower expectations a little...

Will a filter work in a light polluted area...yes and no. Yes, depending on the filter and the target it will help...but no, it will not "solve" the problem...did I mention that a dark sky site was better...

Anyway, back to my experiences...

Although this may sound counter intuitive, I've found the most benefit from filters when I have used them in a dark sky situation...that to me is when they really most helped pull out the contrast that makes faint fuzzies easier to see.

CLS filter- does okay for reducing Sodium and Mecury light from certain street lights and I believe that this is what it is optimized for...it does add some contrast on certain nebula but it also reduces the total amount of light that gets through and sometimes I found it hard to "find" things in the night sky...objects get a "tint" that is hard to describe...in a dark sky situation I did not see much advantage the filter was too "broad" to add much contrast. This is a purchase that I am glad I made only as it helped me learn quite a lot...but, I do not think that it is an "important" tool to have in the tool box and most people will likely be disappointed in its performance. It may just be because they expect too much out of this filter...it is not a miracle maker.

Astronomics UHC filter- It was easily better than the CLS in my backyard and much better yet at a dark sky spot.

DGM Optics NPB - I found that it was similar in performance to the Astronomic UHC but I feel it has a slight edge in performance...I had both at the same time and I chose to keep this one and sell the Astronomics UHC. Both are good but in my scope, with my eye, I could see just a bit more of the "faint" stuff with the DGM Optic over the Astronomics UHC particularly at a dark sky site in my backyard I did not notice much difference at all.

DGM Optics - OIII, I've not had a great deal of eyepiece time with this filter yet...what I've seen I like. It is a different beast than the NPB or UHC optimized to let different light bands pass...it seems to me that i might let a shade more red through then other OIII filters...but this may just be me.

So, where does all this rambling go?

Will any filter solve the problem of backyard light pollution...I am sorry, it will not.

The right filter can aide in viewing faint fuzzies...

Filters work better on some scopes...in my opinion, a small scope can quickly loose too much light from a filter that any advantage gained through selectivity of light wavelength is lost...

I've found that filters work best under dark skies...and without too much magnification...

There are some performance differences between the different types of filters and while there is hard science about which wavelengths of light get through which filter (there is a quantitative difference)...the different views from different filters are a bit subjective (qualitative)...I prefer the DGM Optics NPB to the other "Narrow" band filters that I have tried and would heartily recommend it. It is available direct from the US and with the current exchange rate I think it is a bargain! If I was going to get 1 filter and only 1 filter this is the one I would buy.

Read everything you can on the Cloudy Night website but as many people who post on any internet website are not as experienced as they make themselves sound in their posts (present company included) ignore most of their (our/my) opinions...the stuff written by David Knisely however is well worth a read.

While this may sound cheeky, I'd give this advice to most people...if you are considering a CLS filter, use the money that you would have paid for the filter to buy petrol and get out to a dark sky spot...yes, a CLS will offer some benefit from your backyard but I think most people will be disappointed...and besides, even with the filter doing its job, too much light pollution will never let your eyes get fully dark adapted and this by itself will hurt your ability to ever really see the faint stuff.

If you are in Sydney, I'd be happy to get together with you sometime and show you the difference between the filters I still have...like many things astronomical, try before you buy if you can.

Clear (and Dark) Skies...

bojan · #7 17-10-2007, 07:48 AM

Many thanks to all for the comprehensive insights, especially to Wavelandscott. I will certainly read David Knisely's writing about the subject, he really did his homework right :-)
However, as all of you have written above, I was always aware of the fact that the only cure is to go out in the bush, away from city lights...