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Moon filter?


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Hey guys,

I've been observing the Moon and Jupiter recently and both are quite uncomfortable to view due to their brightness thus surface detail is limited so, I've come to the conclusion that a Moon filter is needed.

My questions are, and you can laugh at them if they're highly stupid (and they probably are) are they universal to all scopes or do I need to buy one specific to my Skywatcher? Where on the scope are they attached? On the eyepiece or on the end of the scope? Are they going to improve my viewing and, people who already have them, are they worth getting?

Muchas gracias.

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Moon filters are pretty universal. You can use any on any scope/EP. They come in 2 sizes (1.25" and 2"). Once you know what format your scope is then you buy the same size filters. I think your scope is 1.25" format.

They screw onto the end of the EP and then you insert that into the focuser. Yes they do improve things and are worth getting. You might also want to buy a light pollution filter.

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Yes they are worth getting. Not a lot of outlay but comfortable viewing and, increased detail shading is always a good thing! :p

My EP's (eyepiece's) are 1.25 and the moon filter (and all the other coloured ones I own) screw into the base of the EP. (it has it's own thread). I then place the EP into the scope. Check to see if your EP's have this thread and that they are the same size, I have a couple that do not!! :)

Hope this helps.

Brendan

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I don't know if the 130 has the dual end cap like my 200, but your big end cap may have a smaller removable one, remove the small cap, but the big cap back on but have the hole in the gap between the spider vanes, is, ie no vanes crossing the hole, this will probably suffice until you get your moon filter and it only cuts down brightness, not magnification.

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I use a moon filter and it certainly enhances the view by providing more contrast, but it can still be a bit hard on the eye depending upon the phase of the moon, the Variable Polarising Moon Filter as posted by Nick looks like it might lead me to another purchase.

Neil

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Of all my filters, the one I always end up using to cut down glare is my variable polarizing filter as you can adjust it to your various needs. It works well on Venus as well.

I took several pictures of Jupiter tonight with my small Fuji f50 and by far the best picture was with the variable polarizing filter fitted. See below:

DSCF0241ed.jpg

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I think an important point to make here (and I always say this) is that the only stupid question is the one you never ask! We were all beginners once and all asked similar questions. There is nothing mor that we delight in on SGL than helping out beginners and imparting our wisdom (either good or bad!)

The advice given here is, as usual, excellent. For planets like Jupiter, you might want to consider a few coloured filters as well. I like yellow for Jupiter and Saturn as, for me, it helps to bring out the surface banding. Red is good for Mars. There is a topic in the primer section that gives details of what each filter is best for.

There is no doubt though that a moon filter will be a wise investment!

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I would also recommend a variable polarizing filter. I bought a basic moon filter with the scope and never really got on with it and actually preferred just popping off the small cap in the dust cover like TopHouse says.

Rik

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it only cuts down brightness, not magnification.

But it does reduce resolution (aperture dependent) and therefore limits the maximum useful magnification.

A deep red filter (Wratten #29) is excellent for the Moon - helps preserve dark adaptation much better than the usual green or neutral density. The Moon is essentially colourless so you're not sacrificing much by using a deeply coloured filter on it.

Jupiter works better with a mid green filter - aim slightly on the bluish side if anything. Neutral density is OK but a green or bluish gree shows up the details in the bands much better.

I do not rate variable polarising filters, they scatter too much light for my taste, reducing contrast and making details harder to see. OK on the Moon, close to the terminator, where the contrast is pretty extreme, but not good at all on planets.

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Jupiter works better with a mid green filter - aim slightly on the bluish side if anything. Neutral density is OK but a green or bluish gree shows up the details in the bands much better.

To paraphrase the Spin Doctors it is certainly a case of 'Different strokes, for different folks, all the way to shinbone alley...'

I've never had much success with green on Jupiter, but interesting that you have. Perhaps another look later in the month might yield different results?

I do think that sometime you just have to try a range and see what suits you best.

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Tophouse makes a great suggestion that you might try first. Leave the main end cap on and just remove the small cap. It cut's down the brightness and the moon is much more comfortable to view. If it still gives you problems then by all means look for a filter :p

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Thanks for all your suggestions and tips guys, they've all been useful.

I guess essentially what I'm after is something that is going to cut down the brightness on Jupiter and Venus and allow me to see some detail. I'd love to see the Great Red Spot but just can't get anywhere near it because of the brightness, the best I can get is a band in the Southern Hemisphere (so Northern in reflector speak).

I'll try the technique Tophouse suggests and go from there.

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  • 1 month later...

Just following this thread and I see on one Antares advert it says that the kewl way of managing the polarizing filter is to put one element into the nose of the diagonal and the other on the EP and adjustment of transmission is done by rotating the EP.

Has anyone done this and does it work?

Clear Skies

Mike

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Just following this thread and I see on one Antares advert it says that the kewl way of managing the polarizing filter is to put one element into the nose of the diagonal and the other on the EP and adjustment of transmission is done by rotating the EP.

Has anyone done this and does it work?

Clear Skies

Mike

That should work, yes. I haven't done it myself but I see no reason why it wouldn't. Two pieces of glass that polarise light when rotated with respect to each other will allow anything from near 100% to near 0% through based on a quarter turn.

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  • 4 years later...
  • 10 months later...

I recommend getting a moon filter with a metal ring. I have a cheap Celestron with a plastic ring which works fine as a filter, but is a pain fitting onto the eyepiece.

As said, coloured filters can be useful. Generally lighter filters work best for small telescopes, bigger apertures allow a wider range. These's a useful pdf guide from the Sangamon Astronomical Society here:

sas-sky.org/wp-content/.../SAS-The-Use-of-Astronomical-Filters1.pdf

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Moon filter does cut down the brightness, but it's set to the amount that it cuts down.  This is where the polarising filter takes over.  More cost, but more options.

There's also nothing stopping you from making a piece of card to go over the end if your telescope and cutting a small hole in the front.  The smaller the hole, the less light is captured by the scope and the dimmer the image.  If you want a brighter image, just cut a bigger hole ;-)   That's basically how camera's "stop down" their aperture.

And no, it wasn't a stupid question, it was asked.  Also the other questions were also worthy...

Which end of the scope does the filter go?

A moon filter connects to the eyepiece (EP), eyepieces come in three sizes .925", 1.25" and 2".  From my expierience, most eyepieces tend to be 1.25".  Easiest thing to do is measure the diameter of the eyepiece, if it's close to one of the figures I mentioned, that's your size ;-)

Why is this not a stupid question?  That's easy, Solar Filters for the sun come in several varieties.  There are some dangerous ones that fit on the eyepiece.  These get very hot and stressed, if they break, you get the magnified sun in your eye leading to blindness.  Seriously, that's how dangerous they are.

There are Safe solar filters that attach to the front end of the scope.  They block the light from entering the scope in the first place meaning that most of the energy is reflected away before any magnification takes place.  They don't get hot and are not under any real stress.

As has been said many times, the only stupid question is the one that hasn't been asked :)

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