Observing Filters

[Mr Q]

In my 50+ years of visual observing, I never used any filters and that included light pollution filters. For light pollution problems, I just drove to a dark sky site (there is nothing like a dark sky site for a night of productive observing). For those filters used on nebulae, I just observed at a dark sky site and saw most nebulae that "needed a filter" to detect.

So, my question is, are they really that useful/needed when a dark sky site is obtainable? I know, for some observers a dark sky site is out of the question but for most of us, getting to one is worth the trouble. Should beginners spend their money on better EPs instead?

[Ganymede12]

I think that depends really.

I never use colour filters on DSO's but I find an 80A (Dark blue) filter is very good for observing Jupiter.

[DirkSteele]

They can have use in a few specific cases, even from a dark sky site. For example, the Horse Head Nebula has proved impossible to see in my 11", even from a dark sky site (mag 6 skies) without the use of a Hydrogen Beta filter. But as you say, generally, dark sky wins.

[swamp thing]

I've found that nebulae filters work extremely well at dark sites. In fact I seldom observe emission nebulae without them. From dark skies where objects like the veil are easy peasy without a filter make it possitively photographic with one. Through a large scope the veil becomes like a length of burning rope hanging accross the eyepiece. Incredible structure and detail is seen when using filters. Dark skies are ace but combine them with nebulae filters and the views are mind blowing.

The extra amount of tenuous detail that they can draw out is well worth the investment IMO.

From a dark sky site it's far easier to get your eye properly dark adapted, this makes a huge difference when using filters and makes the contrast far more pronounced.

Try borrowing one at a star party you'll find the difference a real eye opener.

[rwilkey]

You cannot beat a dark sky site, but for me filters tease out just that little bit extra of nebulosity that otherwise might be missed, a filter also offers more contrast. I never use colour filters, they have never done anything for me, but nebula filters UHC and OIII I have found very useful.

[michael.h.f.wilkinson]

Same as above really, even at a dark site, I found the contrast in, e.g., the Pelican was way better with UHC than without. Even without urban LP or moonlight, there is a residual sky-glow (essentially a process of phosphorescence, light absorbed during day re-emitted at longer wavelength at night). This is also cut by filters. I also use UHC to distinguish very compact planetaries from stars. Planetaries retain their brightness in a UHC filter, unlike stars.

[John]

I only use narrowband filters. ie: UHC or O-III, to enhance the contrast of some nebulae. They work well under moderately light polluted skies but better still under dark skies.

[Ganymede12]

I just bought an IR Blocking filter for imaging. How well would it work visually?

[michael.h.f.wilkinson]

I just bought an IR Blocking filter for imaging. How well would it work visually?

Not needed, as we cannot see the wavelengths it blocks.

[Ganymede12]

But will it make any difference?

[Mr Q]

So I take it that they do add to visual observing. What about nebulae filters for use with binoculars (UHC or O-III)? If available, do they slip over the objectives like a lens cap? Since I use the bins (10x50s) a lot in moderately light polluted skies, looking at the larger nebulae that's too large for my scope's FOV, would they be worth the purchase?

[John]

But will it make any difference?

Yes - your views will be free from a wavelength of light that your eyes cannot see

And you will have another piece of glass in the optical path.

[michael.h.f.wilkinson]

Yes - your views will be free from a wavelength of light that your eyes cannot see

And you will have another piece of glass in the optical path.

Which would tend to reduce contrast a tiny bit

[Ganymede12]

OK, so I'll keep it to my webcam.

[JamesM]

Filters lIke many things in astronomy including eyepieces, can in my view make a difference, but perhaps not as much as their price might suggest - but what price should you place on the 'extra'? At the end of the day, I suppose its personal choice but observing from a dark sky is certainly the one single decision that can guarantee having the biggest impact on what you can see and if the appropriate filter can allow you to see that bit more - then it's a worthwhile investment.

James