Moon filters

[mrdusty]

Which would be better, a 13% or 18% transparency moon filter?

It is for an Orion Funscope 100mm or Meade Etx-60At

Thanks

[John]

I don't find the need for a moon filter even with my 12" dobsonian so I'll say neither.

 

[alan potts]

I am like John and do not find a need for any filters even on a fairly large 18 inch scope, though I did once put my Raybans on when using low power.

[Ben the Ignorant]

Same, no Moon filter, not even for a 12".

[rockystar]

I on the other hand do prefer to use a filter; I just find it a bit uncomfortable observing the moon without one. 

I use variable polarising filter, that way you don't need to choose, you can have both, and many more values as well

If you want a fixed value one though, I'd say the lower value one; you only want to take the glare away. 

But, as you have seen above, check that you actually need one first. And don't buy a really cheep one that will make the moon look green.

[nightfisher]

I am a keen Moon gazer, when work and weather permit and never use a filter, im sure i have an ND some where but not seen it in my kit for a good while, if you find the moon to bright go to a slightly higher mag ep, this has darkens the moon

[ronin]

Have stared happily at the moon through an unfiltered 6" and you get a residual image on the eye for some 30 seconds afterwards but that can be fun - just don't walk around until it clears as you will walk into things.

Both scopes are small enough not to really require one, although they may make it a bit easier for prolongued observing of the moon. 13% and 18% are not a great difference apart. If I had to go for one I think I would opt for the 13%. Although that is likely my preference for getting light through the scope to my eye.

I suspect that half of people would pick one and half the other.

Not sure now about the specification is 13% a filter that blocks 13% so passes 87%, or one that passes 13% so blocks 87%.

Usually they are specified by the amount that they block but 13% transparency I suppose reads transparent to 13% and so blocks 87%. If so then I would say they are too dark.

[Stu]

Everyone's eyes are different, some much more sensitive to light than others so it is difficult to recommend a filter for someone else. As our eyes age and lenses become less transparent I think we get less likely to need a filter on the moon!

Certainly try observing the moon yourself and see how you find it before buying anything. A variable filter makes sense to me so you can fine tune the brightness.

[Dave In Vermont]

I love filters, hence I'm a filter-nut!

For the Moon, I can take them or leave them though. But when I do use one, I wouldn't touch the 13% or 18% or.....Etc. I use the 2-piece Polarizing-Filters like these:

https://www.telescope.com/Orion/Accessories/Telescope-Eyepiece-Filters/Orion-Variable-Polarizing-Eyepiece-Moon-Filters/rc/2160/pc/-1/c/3/sc/48/e/14.uts

And these can also be used on other targets as well - such asVenus to help seeing the phase of it. And any other entities that are in need of dimming-down. Like double-stars with a wide-range of magnitudes between the primary star and it's companion - such as Sirius and it's 'Pup.'

Enjoy -

Dave

[Stu]

26 minutes ago, ronin said:

Not sure now about the specification is 13% a filter that blocks 13% so passes 87%, or one that passes 13% so blocks 87%.

Usually they are specified by the amount that they block but 13% transparency I suppose reads transparent to 13% and so blocks 87%. If so then I would say they are too dark.

@ronin if you do not know then it is always worth checking before giving advice, or not offering it.

There is a useful page on Wikipedia about these filters, the ND0.9 13% filter allows 13% of the light through. The variable filter on FLOs site offers between 1% and 40% of the light to pass through.

https://en.m.wikipedia.org/wiki/Neutral-density_filter

[Sky-J]

After a couple of nights observation of the full moon recently with my small frac, my eyes almost hurt, it seemed to ages for the ghosting to clear .

So I’ve just ordered a variable polarising filter. Glad to hear some of you think they’re good to use!

Clear skies all, Jeremy 

[rwilkey]

I prefer to use the 13% ND filter (it's not too dark at all, Ronin), I find it just right and would advise the OP (MrDusty) to get this one, though I agree with others that a variable polariser is a good option.  From my point of view I prefer not to faff about with this and like to know I am getting just the right amount of filtration, which I believe the ND13 offers me. 

[Ricochet]

I prefer a variable polariser on the moon, not so much to "protect" my eyes but to tweak the brightness to maximise the contrast. However, this is with a 2" polarising filter in my 2"-1.25" adaptor and a 1.25" filter on the eyepiece, so that rotating the eyepiece in the focuser allows the brightness to be easily adjusted. With a 1.25" Newtonian focuser you can only do this if viewing the moon through a barlowed eyepiece where one part of the filter can be screwed to the eyepiece and the other to the barlow. Fixing both parts to the eyepiece will require adjusting the brightness with the filter out of the focuser.

A Neodymium and/or yellow (or even red if lunar viewing isn't the last thing on your agenda) wrattan filter can also help improve lunar contrast at the expense of altering the colour.

[Astro Imp]

When I first started I was advised a moon filter was required for lunar observing, tried it once and it's sat in my kit case unused and unloved ever since.

I know everyone is different just my take.

 

[Stu]

22 minutes ago, Ricochet said:

With a 1.25" Newtonian focuser you can only do this if viewing the moon through a barlowed eyepiece where one part of the filter can be screwed to the eyepiece and the other to the barlow. Fixing both parts to the eyepiece will require adjusting the brightness with the filter out of the focuser.

That is very true. One possible option, which relies on having enough back focus is to put a short 1.25" extension in which you screw one half of the polariser to, that way you can still add the second part to the eyepiece and rotate it to get maximum brightness.

[Nojus]

I've bought Moon filter,but using of it hadn't made different for me,except the color (blue filter),so any additional glass make image worse,I decided to not use it..

[John]

I only use filters where they make a really big difference, in positive terms, to the views. So it's narrow band and line filters for nebulae and a Herschel wedge for white light solar.

I do actually have a lunar filter but I keep that for outreach sessions when someone requests it. It's a difficult concept to explain that telescopes don't make the moons surface any brighter than it is with the naked eye 

 

[Nojus]

Just now, John said:

 It's a difficult concept to explain that telescopes don't make the moons surface any brighter than it is with the naked eye 

 

Totally agree with you..

[Geoff Lister]

I find it easier to observe the faint fuzzies first and leave the Moon to the end of a session. My eyes adapt faster going from dark to light, than they do going from light to dark.

Geoff

[John]

If the moon is in the sky I don't tend to chase the really faint stuff. They look so much better on a moonless night

For planetary observing a bit of moon gazing first actually helps. Very keen planetary observers have been known to stare at an illuminated section of a white surface prior to observing.

[Piero]

I do not use filters on the Moon either, as many other members said above. 

For me the reason is that I'm excited to observe the Moon when it is waxing or waning rather than when it is full. During those phases, you can catch plenty of details particularly along the terminator, and I do not find the Moon so bright to require a filter to dim the brightness. Also, you can control the image brightness by reducing the exit pupil, said in another way, by increasing the magnification. Therefore, I would observe the Moon with what you already have before investing in a filter.

I find a full Moon a poetic target when it is low above the horizon coming up from the trees, and is observed through a refractor at low power. In this case, 1) the thicker layer of atmosphere nicely works as a filter (..and adds some tint too!), 2) the refractor projects the image correctly (up is up, down is down), and 3) a low power eyepiece gives a large fov, showing more surrounding Nature. I had some wonderful views of full Moons at low power when this target was illuminating the branches and leaves of trees between us, birds on trees and flying all around, and soft horizontal clouds partially shrouding the Moon with the delicacy that a warm scarf has on our neck in the winter. 

[Dave In Vermont]

If using a 90° Diagonal on a scope, you can screw one polariser-filter into the end of the diagonal - on the end pointing up the OTA - and the other polariser into your eyepiece-du-jour. Then rotate the eyepiece to the dimming you wish. Works great!

Dave

[LukeSkywatcher]

Ive never found the need to use a Moon filter on any of my scopes.

[mrdusty]

I'd like to thank all of you for your input. I believe that I'll take the advice of doing a bunch of observing before deciding if a filter is really needed in my case.

Thanks again and clear skies to everyone,

MrDusty

Richard Hayden

[Ben the Ignorant]

On ‎11‎/‎11‎/‎2017 at 05:33, alan potts said:

I am like John and do not find a need for any filters even on a fairly large 18 inch scope, though I did once put my Raybans on when using low power.