Moon filters

[meddyliol]

I have seen loads of moon filters for sale in various colours. Is there such a thing as 'the best colour'? What is a good make?

Thanks

Brian

[Stu]

Not everyone uses them but if you want one I would either go for a neutral density filter which basically reduces the brightness whilst keeping the colours natural, or a Baader Neodymium filter.

You can get a variable ND filter which allows you to adjust the brightness by rotating two polarising elements, quite handy

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[tarotrocola]

I have a variable filter, so you can adjust the brightness for each phase of the moon. But I've seen people using sunglasses...

[ronin]

Moon filters are generally something like a 30% ND filter not coloured.

Often get sold in a set of a moon filter and 3 or 4 coloured filters.

The variable ones seem best simply as you can vary the attenuation, they cost suitably more for this privilage also. :grin:

[meddyliol]

I was wondering what an ND filter was for, thanks for that. I will have a look for a variable one as well. How would I screw a pair of sunnies to the lens? 

Thanks for your inputs, great help

[Stu]

This might be stating the obvious but with the variable ones you can fit one to the front of your diagonal and the other to the bottom of your eyepiece. In this way just turning the eyepiece varies the brightness so it's very convenient.

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[rwilkey]

Hi Brian, coloured filters are rubbish for the Moon, venders on Ebay always put 'Moon' as it gets them more hits, but they are not really Moon filters.  The best Moon filters are the Neutral Density (ND) ones, and come in various light transmissions, the one I use the most often is the ND96 0.9, which gives 13% light transmission, the other popular one is the ND96 0.6 which gives 25% light transmission, these are often annotated as ND13 or ND25.  The good thing about these is they give no colour caste and give a completely natural view of the Moon.  I prefer using fixed density filters as opposed to the variable ones as there is no faffing around at the eyepiece to get the density right, but Stu's method above works well too.

[Peter Drew]

You would wear the sunglasses to view the Moon. Don't try this with the Sun under ANY circumstances. 

[Moonshane]

for Newts I prefer the baader neodymium filter. it's great on Mars and Jupiter too. In fracs I tend to prefer no filter.

[John]

I don't find I need to filter the Moon, even with my 12" scope.

[Digger1895]

Hi Brian, coloured filters are rubbish for the Moon, venders on Ebay always put 'Moon' as it gets them more hits

Yep, I've looked through a green moon filter and it did nothing to the image except turn it green.

I personally don't bother with one as I don't find the view too bright.

[meddyliol]

Thank you for your answers. I think I will put an ND one on myAmazon wish list    

[RichM63]

In the meantime, leave the end cap on the OTA and remove the 2" bung, it will reduce Lunar Glare, and best of all it is FREE!

[Moonshane]

Free but cost you resolution!

[John]

In the meantime, leave the end cap on the OTA and remove the 2" bung, it will reduce Lunar Glare, and best of all it is FREE!

It will reduce the brightness of the Moon but it turns the scope into a 2" aperture one so no "free lunch"

[bingevader]

I like my moon unfiltered.

I'm sure there's a gag in there to do with beer or women or something, but it escapes me for the minute.

[RichM63]

It will reduce the brightness of the Moon but it turns the scope into a 2" aperture one so no "free lunch"

I did say Lunar Glare.

However; I always understood that the 'aperture' of a Newtonian telescope was equal to the diameter of the Primary Mirror and not the size of the hole allowing light to enter. Otherwise why don't we have huge cone shaped OTA's with a 36" opening going down onto a cheapish 12" mirror? (there is probably a simple and good reason why not, but I can't think of it).

[Charic]

I did say Lunar Glare.

However; I always understood that the 'aperture' of a Newtonian telescope was equal to the diameter of the Primary Mirror and not the size of the hole allowing light to enter. Otherwise why don't we have huge cone shaped OTA's with a 36" opening going down onto a cheapish 12" mirror? (there is probably a simple and good reason why not, but I can't think of it).

.........aperture is the size of the hole  through which light travels. If you have a 12" telescope  and just open the 2" cap, you end up with a 2" aperture telescope. 

Starlight is collimated, ie  travels in straight lines, negating the cone OTA theory.  Not all of the light would hit the primary mirror, hitting  the cone first and getting wasted?

[John]

As Charic says, the 2" hole in the dust cover of the scope stops the scope down to a 2" aperture but the focal length remains the same so around a 2" f/24 in the case of the 8" F/6 dobsonian.

Stopping down can be useful in some circumstances as long as it's accepted that the resolution and light grasp of the scope will be that of the stopped down aperture rather than the full primary mirror or objective lens.

[AndyWB]

This one comes up quite frequently, and I usually seem to end up suggesting "Increase your magnification". It dims your image, which is normally a bad thing, but for the Moon can be useful.

[Moonshane]

I am not suggesting you buy one for this but I have found that my Lunt Herschel Wedge without the ND3.0 filter works superbly on the moon, especially with my 120mm f5 achro - really dims down the surface and reduces a lot of the CA too.

[bomberbaz]

I have a Neutral density filter, a variable polarizing filter and coloured filters. I think I need to give the ND filter a little more time on the moon but I do use and find a the variable to be the best in getting more detail out when the moon is getting fuller. That said I love the yellow and the bonus is mine came in a set of 5 (ironically including a supposed moon filter   ). Its not an expensive filter by any means but it really lifts details out on the mountains and valleys etc. 

http://www.wexphotographic.com/buy-tal-filter-set/p10724 I bought these and find them perfectly acceptable for visual. I think the photo chaps might not think the same but at under 50 quid for 5, what do you want. 

[Steve55]

What would be , or is always down to personel taste the ideal filter to use i have the  nd 0.6 but it did not seem to make too much of a difference to me, it was only a half moon though. Is this just me being new and needing to become accustomed to using a scope or is it not really enough for a 6"  mirror

[meddyliol]

In the meantime, leave the end cap on the OTA and remove the 2" bung, it will reduce Lunar Glare, and best of all it is FREE!

Is that what the bung is for? I really had no idea, in fact, I never thought of it before.  

[John]

Is that what the bung is for? I really had no idea, in fact, I never thought of it before.  

Yes, you too can have a 2" aperture scope