Colour filters

[chmatthew]

Hi All,
I hpoe everyone have a good holiday break.
A question for everyone and anyone: I have a set of colour filters which I have hardly used. This is partially because I have read a lot of conflicting literature on them. For example, on text may say a particular coloured filter is good for observing X, while another will say that a differnt colur is better for observing X, and yet another will say that the first colour is better for observing Y.

So my question is: do any of you use colour filters and, if so, which coulors and what do you use them for?

I look forward to hearing from you soon.
Chris

[ab1963]

It's good to listen to advice but never take it as gospel ,Why don't you pick a target and try different colour filters and see which ones give you the best view through your eyes , That's the same as most things in this hobby it's what suits your viewing needs not others but that's just my 2 bobs worth.

Hope that helps

[astro744]

See http://alpo-astronomy.org/mars/articles/FILTERS1.HTM

Colour filters are useful in enhancing contrast of surface and cloud features of planets. Different colours will bring out different features so all colours are useful. E.g. A light blue filter gives the Great Red Spot on Jupiter are darker appearance making it easier to see. A red filter will give blue festoons are darker appearance.

Some filters are quite dense and require larger apertures to maintain brightness at the higher powers but most with the exception of possibly #47 work well with 6-8" aperture. Sometimes the contrast enhancement of detail is subtle and sometimes dramatic, it just depends on the colour of the feature and the colour of the filter being used.

[chmatthew]

Thanks for that. Very helpful.

One more question: I was reading something the other day and it said that using a ‘nebula filter’ would be advisable for looking at the Rosette Nebula.

What exactly is a ‘nebula filter’? Is it a specific colour etc or, as suggested, should I just try differnt ones to see which one brings out the best details?
Chris

[astro744]

See https://farpointastro.com/product-category/filters/nebula-specialty-filters/

Lumicon was taken over by Farpoint but I refer you to them because I am familiar with their products and they were one of the first if not the first to market these many years ago.

Nebula filters are contrast enhancing filters available in different bandwidths. Broad, narrow and line filters are available.

The Lumicon Deep Sky filter is a broadband filter that gives a mild boost to contrast. The UHC is a narrow band filter that gives a significant boost to contrast and contains both the O-III and H-Beta lines. The O-III and H-Beta are line filters centred on specific parts of the spectrum.

Many nebula emit in O-III, especially planetary nebula so the O-III filter is ideal for these whilst some objects are stronger in H-Beta so the H-Beta filter is better for these objects. The UHC is my recommendation as a first filter followed by an O-III and then H-Beta.

There are a few brands like Lumicon, Astronomik and Thousand Oaks that I have used and recommend and many others that I have not tried.

As for the Rosette nebula it is a very large object so you need a 2" low power eyepiece with a 2" filter and reasonably short focal length telescope to see it.

See also http://www.prairieastronomyclub.org/useful-filters-for-viewing-deep-sky-objects/

[chmatthew]

Thanks. Yet again, very helpful.
Chris

[gaseous]

I think a decent nebula/OIII filter is a "must-have" (or at least a "highly-recommended-to-have") piece of equipment which would get a lot of use. Personally I find the colour filters, while perhaps highlighting certain planetary aspects, are a little hit and miss, and the exceeding unnatural coloration tends to detract from the overall viewing experience (for me at least). Each to their own though!

[Joves]

I agree with Patrick, the colour filters are a little hit and miss. Personally, unless one is really focussed on enhancing subtle features on planets (in an unnatural view from a colour perspective, which impedes the effect, in my opinion) then I’ve always felt the colour filters weren’t really for me.

I have too many filters to use, left alone justify. If i were to recommend one to start with as a general purpose filter aimed at enhancing sky and nebula contrast, it would have to be the UHC (irrespective of brand, but you really can’t go past Astronomik). If your scope has a reasonable aperture and you observe under reasonably dark skies, then an OIII filter will compliment that well. If I could only have one though, it would definitely be the UHC filter. It has a less pronounced effect when compared to the OIII, which works on more nebula in typical urban conditions under typical urban skies. The OIII can tend to block the view if the conditions and scope aren’t quite right. the Hb filter is really only effective on a select number of targets, the most popular being the Horsehead Nebula. This is an object that won’t be seen by simply applying a HB filter. Dark, transparent skies and a reasonably large aperture are the only things that will give you half a fighting chance for this particular object... the HB filter will then hopefully increase your chances of seeing it, but will add nothing if all other conditions aren’t right.

Note, I have never seen the Horsehead, irrespective of effort and owning several filters, including the HB! :rolleyes:

[bigjoe]

The filters I have found that really enhance Jupiters belts and festoons and GRS, are a light green, or even a light blue ...esp in an achromat and scopes with large central obstructions.

More so, in larger apertures, as Jupiter is so bright that detail is hard to see, unless a higher magnification than usual is used.

Fringe Killers are also very good in an Achromat...And I've also used my Astronomik CLS, to telling effect on Jupiter and Mars.

Excellent guide to filters by Brian Ventrudo here
https://agenaastro.com/choosing-a-color-planetary-filter.html


https://agenaastro.com/guide-to-light-pollution-filters.html

bigjoe.

[Startrek]

I used a blue #80A filter to observe Jupiter at 4.00am on the 5th, 6th and 7th January and it made all the difference in the colour , contrast and details of the planet.

Jupiter ( and Mars ) was at 25 - 30 deg with average seeing conditions and the filter worked a treat for me

Magnification was at 208x

In my limited experience it’s hit and miss with filters you just have to try them.Some work well and some don’t improve the view at all.

[bigjoe]

Too true Martin ..I've used red coloured filters on Mars ..and found it made the details harder to see in apertures under 5 inch..orange much better for that task IMHO.

bigjoe.

[ausastronomer]

Hi Chris,

I gave a presentation at the Ice In Space Astro Camp (IISAC) at Lostock about 6 years ago on "Visual Astronomy and the Use of Filters".

I have attached a link to my Power Point Presentation and you might find some helpful information in there. (http://www.iceinspace.com.au/63-680-0-0-1-0.html)

You can just download the PDF file linked on that page.

Technology and Brands have moved a little bit over the past 6 years but the basics haven't and won't ever change. At the end is a summary on a whole list of the Wratten number colour filters and what targets / features you might find them useful on. Obviously they work slightly differently for different people, but it's a good starting point for you.

Cheers,
John B

[eiddy]

Thanks John,

I just went through your PPT presentation and found it very useful for myself as a relative newcomer to the hobby. I am sure others will do so likewise.