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John

Moon Filters for Visual Observation ?

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This topic comes up a lot on the forum.

Personally I don't find that I need to use one even with my largest aperture scope (12 inch dobsonian). I'm happy for my eye to adjust as required and don't try and observe faint deep sky objects after observing the moon, not that the conditions are good for faint objects when the moon is in the sky anyway. Neither do I stop down the aperture of my scopes other than occasionally my dob but thats to get a cleaner image of binary stars. Generally I observe the lunar surface at quite high magnifications and that I find reduces the brightness of the lunar surface in the eyepiece.

I do have a moon filter but I only use it at outreach sessions if folks feel they want one.

But thats just my approach after my years in the hobby and I'm aware that there are quite a range of viewpoints and preferences on this so I'd be interested in hearing what your preferences and experiences are :smiley:

 

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For some reason I find anything much more than a quarter moon too bright to the point where it will cause me discomfort and make my eye water, so I have to use a filter.  I have always had good night vision so perhaps I am bit like Riddick for those that know their Sci-Fi. 😁

 

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As I have said often when this comes up for discussion when I started I was told this was a "must have", used it once or twice and it's stayed unused and unloved in my eyepiece case since.

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If I do...  

5addf27ccac70_variablemoonfilter.jpg.e490ce031fc7badb2a139b6d8384c995.jpg 

...I just use a variable polarising filter - note: this type is only available in 1.25".

Edited by Philip R
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I find that in anything other than high powers, when the moon is fairly dim, viewing the moon makes eye placement tricky. I wonder if it is trying to line up a smallish exit pupil with a small pupil opening - when the pupil closes down due to the brightness.

So I recently bought a 2" variable polarising filter too on a bit of a whim when I was buying some other kit. The idea was to fit it to the objective end of the diagonal so I could still change eyepieces without any fuss. The filter itself works very well, exactly as expected. But.... to be honest it only been used once and then languished in the eyepiece case. 

Perhaps I'll give it another go if the clouds clear - the moon is certainly bright enough tonight!

Gordon

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I recently got a Moon filter, the thinking being that on the one night it's clear enough to have a go, Luna will invariably be just about full and a filter might just make it a bit more fun. As I reported on my first session in months, I couldn't resist trying out the filter, even though it wasn't strictly necessary to my mind. I quite liked it! To my eyes, it truly made good on the "neutral density" promise, tempering the brightness while maintaining colour. For the record, this was with an 8" f/6 newt; I'll be certain to try it with my 85mm f/7 frac as well (perhaps a 'weaker' filter might be in order there).

So yes, having tried one, I can honestly say I can see the value of a Moon filter - certainly of the neutral density variety - and will continue to use it with the 8" newt.

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@John you've started an interesting discussion. Just shows how we are all individuals and each have our own preferences. There's no right and wrong as is the case in many things just what suits the individual. This is true in many areas of life in general as well as in our hobby.

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10 minutes ago, Astro Imp said:

.... There's no right and wrong as is the case in many things just what suits the individual. This is true in many areas of life in general as well as in our hobby.

Very true Alan. While I don't use lunar filters myself I'm more open minded than I used to be about their userfulness now. It's good to get a range of viewpoints on them - thanks folks ! :smiley:

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I never even consider it usually but some recent images on the forum using good quality red filters for the images and compared with other colours made me regret selling a baader 610nm filter I bought for the purpose of lunar observing a while back.

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I prefer to increase the power rather than use filters.

Edited by Saganite
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I normally Lunar observe without filters, but I do sometimes find it indeed hurts my eyes.
At that point I will either take a tea break or on an odd occasion add a Neutral Density filter.
So I sit on the fence a bit on this one.

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I think it important to understand that every ones eyes are different. John, I know you have not seen the value of these filters in the past, but I genuinely think that eye sensitivity varies to a sufficient degree that some find it too bright observing without a filter. My right (non observing) eye shows much brighter images than my left eye, so I can really see how this happens.

I often use a Neodymium filter just to cut back the brightness a little and I find it works very well.

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3 hours ago, Stu said:

I think it important to understand that every ones eyes are different. John, I know you have not seen the value of these filters in the past, but I genuinely think that eye sensitivity varies to a sufficient degree that some find it too bright observing without a filter. My right (non observing) eye shows much brighter images than my left eye, so I can really see how this happens.

I often use a Neodymium filter just to cut back the brightness a little and I find it works very well.

Thats interesting Stu. I think this is much more to do with individual preferences and tolerances. There isn't a right or wrong approach.

 

 

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Yes Stu, I have the same disparity with my eyes too, things are brighter through my right eye than my left.

When I was out looking at the Alpine Valley the other night I was using quite high power and it didn't seem too bright with my left viewing eye.

However,  as soon as I looked away from the eyepiece I found I couldn't see anything through my left eye for quite a few minutes . I don't have a moon filter but I may well get one now.

Edited by Geoff Barnes
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This conclusion sounds like premium eyepieces, no wrong or right, we all like differing things and all see things in a differing way, it’s what makes life so much fun, diversity.

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8 hours ago, John said:

Thats interesting Stu. I think this is much more to do with individual preferences and tolerances. There isn't a right or wrong approach.

 

 

I understand John. I suppose what I was trying to say was that when experienced members such as yourself strongly say that they do not use or see the value in these filters (as you have done in the past), it may put people off trying them out. I'm sure there is a benefit for those whose eyes are more sensitive to bright light; younger members for sure will likely have more sensitive eyes and may find a use for them. One thing is for sure, it is a better option than reducing the aperture and resolution of the scope.

I think it is more to do with brightness tolerances than anything else, so as you say, no right or wrong approach.

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I used to use a Baader 0,9 ND-Filter to view the Moon. I still have the filter and it is more comfortable (brightness) to view the Moon through it. However, I stopped using it when one night looking at the craterlets in the crater Plato, I found that I could see more of them and the views were sharper without it. I suppose this comes down to the quality of the filter? Or is putting any filter in the light path likely to detract from the view?

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I have ND filters and a Baader Neo but I prefer the unfiltered views. Brightness diminishes as our pupil shrinks up and can make it seem like the other eye is "brighter". After reading Avani's thread on the use of filters in lunar imaging and the effect that the red filters have regarding seeing, I'm going to try one for sure.

The beamsplitter in binoviewers halve the light making the image dimmer per mm of exit pupil, which can be useful for some.

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11 hours ago, Stu said:

I understand John. I suppose what I was trying to say was that when experienced members such as yourself strongly say that they do not use or see the value in these filters (as you have done in the past), it may put people off trying them out. I'm sure there is a benefit for those whose eyes are more sensitive to bright light; younger members for sure will likely have more sensitive eyes and may find a use for them. One thing is for sure, it is a better option than reducing the aperture and resolution of the scope.

I think it is more to do with brightness tolerances than anything else, so as you say, no right or wrong approach.

I don't want to deter people from trying them. They don't cost a lot so it's relatively easy to pick one up and see what it does for you. The reason that I started this thread was to invite a range of viewpoints and I'm pleased that it has done that. My preferences are just one data point on the subject :smiley:

 

 

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On 17/01/2019 at 21:40, iPeace said:

I'll be certain to try it with my 85mm f/7 frac as well (perhaps a 'weaker' filter might be in order there). 

Just got back in from a late session observing the Moon with the TV-85. Views were hazy, but I did appreciate the tempered brightness that the filter delivers. Although I didn't have the sensation of the filter excessively dimming the view, I'm still interested in trying a 'weaker' variant of the filter with this scope and indeed with my even smaller scopes.

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I tend not to struggle with the brightness of the Moon, but do think coloured filters can be useful. A blue filter tends to boost contrast, and can make detail a bit easier to see (especially the contrast between basaltic Mare material and the rest of the surface). I find it especially good for when the Moon is at or near full (when observing without a filter can be pretty dull) as Mare features, ejecta etc get a bit of a boost. I also quite like the orange filter, especially if observing during daylight or early twighlight - it makes the rest of the sky much darker and gets rid of the scattered blue light that robs the image of contrast.

But most of the time I don't use them either. Just now and again.

Billy.

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Very few filters impress me, including moon filters. It seems that although coloured filters may enhance certain features on a planetary surface, they generally detract from the pure view. Likewise, moon filters are just another piece of glass in the light path that are probably not as optically perfect as the scope or eyepiece. In other words its an optional weakest link! I believe there's a real advantage to using a variable polarizing filter for Solar, eg in conjunction with a Herschel Wedge but haven't found it useful with the moon, however, I tend to use small to medium size scopes, so others may have a completely different experience. 

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I usually prefer to view the Moon without filters, enjoying the brilliance at low power or depending on magnification to dim things sufficiently at high power. There’s also the feeling that some filters introduce cheap glass into the system and might degrade the image.  I’ve tried quite a few over the years and have found the Baader Moon filter (not the neodymium) to be the best. It doesn’t, to my eye, result in obvious loss of detail or definition and it does improve comfort for extended observing.

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I had a Moon filter. Never found the need to use it. It now lives in Texas.

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I've had moon filters for a few years. Initially I preferred not to use them as I saw more detail without them but over time I have used them more often only to make it less tiring to observe. However once the magnification is high enough and the image is dim enough the filters come off.

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