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Old 31-07-2020, 10:30 AM
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mental4astro (Alexander)

mental4astro is offline
Join Date: Jun 2008
Location: sydney, australia
Posts: 4,881
Colour filters can be very useful for the Moon and planets. One problem I find with many "filter kits" is the colours usually found with these are both too intense/deep, made to appeal to people's eyes as pretty colours, and not the best colour selections for "general" applications.

I won't go through a run down on what colour is best for here or there. There are plenty of resources already detailing this, including the pic below. Instead I will give a few tips on how to get the most out of them. What all filters do though is only help with showing specific features, and are not intended to enhance the overall image. All filters are for specialised applications.

Planetary details are subtle, and more often than not require less intense colour to bring out the details. Also, deeper colours are better suited to larger apertures as the amount of light they cut out is significant and smaller apertures are just not able to deliver a usable image brightness with these.

There is also the difficulty that most planetary details when using colour filters will not just jump out screaming "here I am!". More often how these details appear will only be as gentle enhancements that depend more on a patient, more trained eye to pick and identify them.

Aperture, optical quality, seeing conditions, eyepiece selection, are also important as the planets are already very small, planetary features are even smaller, so it is not just a simple thing as bunging in a filter and "BANG! there it is"... Sometimes some features will suck your eyeballs out in just catching a glimpse of them!

Often it is not just one filter colour that is necessary but different intensities of the same colour or different colours that by interchanging the filters helps with identifying features.

I've come to find that observing the planets is more of a niche than I thought of when I started. I also thought that one only needed just two, three or four filters, which for most people this is enough, but as I spend more and more time with the planets I'm using a larger number of filters, and several just to pull just ONE feature.

I have also noticed that Jupiter is much more dynamic than I first thought. Features not only come and go, but also vary in colour saturation, hue and contrast over the years. Jupiter has been especially colourful this year I'm finding, but it could be my observing skills have improved.

I have also noticed that over the last 20 years the choice of colour filters has also been reducing. Some colours are difficult to find and others have just about disappeared. The image below shows a huge number of filter colours and their applications, many of these colours very difficult to find now. I have 12 of these, and some not found in most astro stores. I am looking for a few others too.

When it comes to the Moon, if I'm viewing the whole of the Moon then its brilliance can be painful, so I use either one polarizing filter or couple two together that allows me to vary the amount of light that is being transmitted from around 50% down to close to 1%. I prefer this as I could be using an 80mm refractor or a 9" Maksutov or a 17.5" dob, and they all deliver different levels of image brilliance. But most times I am using high magnification, so glare is not a problem. But with high magnification I find the 82A fantastic to bring out low contrast features, such subtle shade variations in the Seas and to help make ejecta rays stand out more, of which there are a surprising number of small craters with bright ejecta collars which are difficult if not impossible to identify without the help of the 82A filter. These days I am observing and sketching the Moon both neat without a filter and with an 82A, and frequently alternating during the session.

Some colour filters can be used to help bring out cometary details. One thing that helps most with comets is aperture. If features like the tail (or tails as there can be multiple dust and ion tails) are faint, aperture is your best friend as a filter alone may not be enough for our eyes to pick up the transmitted light. Strong colours will not help, they need to be subtle saturations of colour. Yellows will help with the dust tail, soft greens the ion tail. Even an OIII filter can help with the ion tail.

Comets are difficult customers too, often not living up the the predicted hype, but sometimes they do throw up surprises. Bright ones are also rare. Filters for these are best not bought expressly for them, but best allowed for in the filters you chose for other things.

There was a specialised comet filter offered by Omega Optical, but I haven't seen it being offered recently though. Their Hb + Oiii hybrid filter would be a good option though.

It is also a very good all-in-one filter if you don't want to spend money on having separate Oiii and UHC fliters. I have this filter and it is the one I use most - I also do have dedicated Oiii and UHC filters, and use them when I want to really get funky with relevant DSO's.

If you want to see more you just need to give yourself time. You are battling not just your eyes but also prevailing seeing conditions. You will need to wait for those fleeting moments of absolute clarity more often than not, and these need patience as it may take a few of these moments to really get your eye in. The amount of planetary detail that can be seen really is staggering, and every bit as much as photos show. But there are many factors that need to all line up first PLUS patience from you. And it may also take a few nights of observing to finally get one of those nights when what you see just leaves you truly astounded.

The polar ice caps of Mars are easy to see, but high altitude clouds not so much.
The GRS of Jupiter is a soft salmon pink that needs a little concentration so spot today, but the festoons and other turbulence features need time at the eyepiece.
The A and B rings of Saturn are easy too, but shading variations in these and the C ring need time.

Patience, grasshopper.

OH, one last thing! Seeing details on the planets is also a very individual thing! Don't forget everyones's eyes are different, different sensitivity, different colour perception, different eye health, different acuity, different ages, different experience. Our eyes are not all the same like bottles of Evian water. When I was 42 years old I was showing Saturn at an outreach event, telling people that there were three of its moons visible with the scope I was using. A 14 year old boy comes up to the eyepiece and says "I can see four, no, five moons"... And there were!

Attached Thumbnails
Click for full-size image (05453_Premium_20-Piece_Filter_Set_inside.jpg)
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Click for full-size image (Jupiter, May 5 2018 (3) LR.JPG)
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Click for full-size image (C-2020 F8 SWAN LR.JPG)
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Click for full-size image (Archimedes et al (2) LR - Copy.jpg)
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Click for full-size image (Saturn, June 12, 2013.jpg)
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Last edited by mental4astro; 10-08-2020 at 05:28 AM.
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