Neutal Density, Polarising or Moon filter ?

[gaa_ian]

Ok ...I have seen all of the above recommended for lunar viewing.
I have a typical giveaway "Moon" filter as supplied by Andrews with their scopes.
Which is which & what is the difference/ Is one better than the other :confused:

[ballaratdragons]

Yes they are different Ian. Polarising filters are adjustable, ND filters block stray and excess light and a Moon Filter is usually just darkened glass to cut glare.

See here:http://sciastro.net/portia/advice/filters.htm

[gaa_ian]

Thanks Ken
The polarising filer might be best as it suits differnt phases of the moon.
I am interested to find the best as I did an astronomy night for a School camp the other night and the moon through my 10" Dob left everyone feeling a bit stunned by the brightness, but I'm not keen on the green cast given by the traditional "Moon Filter"
It gives a false impression of what the moon looks like in reality.

[ballaratdragons]

And the Moon filter isn't much good on any other object either! It's just TOO dark.

[h0ughy]

get an orion variable polarising filter! you can adjust it to suit no matter what your looking at

[ballaratdragons]

Sounds good Houghy! but what is it like for DSO's LOL!!

[h0ughy]

I don't know ken,
the serious answer
maybe if the light is travelling in one particular linear plane you might be able to tease out some detail. But I would say that it would dim it for sure. :shrug:

Now I am finished with the serious answer, I would have it in the eyepiece and get a DSO in the eyepiece, then just before I ask you to look, turn it 90 degrees to give you the best view :poke:

[ballaratdragons]

Haha!

I have seen the multiple filter attachments advertised. You would have to be doing a serious night of viewing/photography to use one (or want a scope that is full of gadgets).

[ballaratdragons]

A warning for anyone using filters (especially Moon filters).

Remember to take it out of your EP when you have finished using it.

Don't make my mistake of leaving it in! Makes it very hard to see other objects with a Moon filter left in :doh:


and I do it quite often :ashamed:

[h0ughy]

there might be a few guys on this site that could vouch for that! i have a CPF for my 18-125 sigma lens, and one for the 50-500, and at QLD astrofest i bought an orion VP for 2" eyepieces. it is excellent :cool:

[square_peg114GT]

I'll 2nd that. The Orion VP also makes a great Mars filter for scopes 8" and larger.

[johnno]

You,Me, and I bet quite a few others Ken.
Regards.John

[ausastronomer]

I have a 2" orion Variable Polariser and it works well. Remember however, that any filter that reduces the amount of light reaching your eye also reduces the amount of fine detail reaching your eye.

CS-John B

[Miaplacidus]

I've been trying to track down a local supplier for the 1.25" and 2" Orion Variable Polarisers. Where did you guys get yours?

Cheers,

Brian.

[ausastronomer]

Brian,

Bintel carry the 1.25" version in stock and do a special order on the 2". It took them about a week to get the 2" version in for me.

CS-John B

[Starkler]

Yes and for this reason I dont use any kind of filter for viewing the moon.
I own an Antares brand variable polarising type and just dont use it.
Sure when you first look you get a bit of eye-shock, but the eye adjusts quickly enough.

[square_peg114GT]

That can't be good for your eyes! Your eye was never meant to to view the moon thru a 10" pupil! Owwww!

[Dave47tuc]

I have a Variable Polariser filter and a No 96-0.6 filter
(really just a blockout filter ) :D

I use neither, cuts out to much light for me IMO. ;)

I find using the 80A blue filter and 15 Yellow helps bring out fine detail for my eyes. :rolleyes:

IMO I think the Variable Polariser is a waste of money. :poke:

[h0ughy]

thank goodness that's only your opinion :scared: :doh: i find that it decreased surface brightness, :doh: but increases contrast and you get to choose by how much. :D best thing since sliced bread :cool:

[Dave47tuc]

As I said IMO.

One mans sliced bread is another mans toast. ;)

[Starkler]

My vari polariser certainly doesnt increase contrast. Theres nothing i can see with the filter in place that I cant see without it. In fact it seems to slightly degrade contrast however this may have to do with less light reaching my eye.

[h0ughy]

I'll add that it was my "IMO", that dave47tuc is right and that Mr Starkler you are right too. it is all opinionated really :whistle:
:poke: isn't that what the forums are for, differing opinions and experiences ;)

[Dave47tuc]

:poke: isn't that what the forums are for, differing opinions and experiences ;)[/QUOTE]

For sure :thumbsup:

[gaa_ian]

Looks like I will add this item to the list of "Things to try out" at the next starparty !
In the meantime I will use the "Moon" filter to stop the "pupil shock " :scared2: that people get looking at the unfiltered moon through a 10" scope.

[Starkler]

Quote of the week :lol:

[h0ughy]

have to get mike and the Mods to create a QOTW section.

[janoskiss]

I expect that one would not be able to tell the diff between a polarising filter and an aperture mask that produces the same decrease in light intensity. The advantage of the crossed polarisers is obviously tunability, so you can get it just right. But on a Newtonian, a mask that avoids the secondary mirror and spider vanes may be superior to a filter in terms of contrast.

(BTW. I am not speaking from experience. Just speculation based on the little I know.)

[ausastronomer]

Not necesssarily so, because by reducing the telescopes effective aperture with an off axis aperture mask you also reduce its resolving power.

CS-John B

[janoskiss]

Yes, of course, John! :doh: I didn't even think of that. At high magnifications, a filter would be preferable. Although if the scope really needs a filter at high magnification, it is probably big enough to normally exceed the resolving power that the atmosphere would allow... ??

[Starkler]

Steve at high magnifications, any extended object is also going to be dimmer to the eye, lessening the need for a filter.