cheap 2 " filters

[iancandler]

I dont know if anyone thought of this before but I often see photographic filters on e bay for a fraction of the cost of astronomical ones. So I did some measuring and took the plunge.

For the princely sum of £6 including carriage I picked up 3 blue 48mm filters (82A,80B,80C) and one light yellow (81B).

They fit 2" eyepieces and accessories perfectly.

Even new they are only around £9.99 each, which brings a set of four out at around the same money as a cheapish set of 37mm filters. Of course the optical quality is superb as you are getting filters from companies such as Hoya who have a good pedigree.

[Ambermile]

... however be aware that you are putting the filters at the other end of the optical train than that for which they are intended - and so any imperfections will be magnified...

Arthur

[The Warthog]

There is an article in this months Night Sky magazine which mentions using filters in just this way, as an alternative to changing filters or using a filter slide. I have heard of this before, especially with OIII filters, which can be moved on and off the ep, producing a blinking effect which can make difficult nebulae more easy to spot.

The article also suggests that you can obtain a swatchbook of plastic filter samples used in theatrical lighting, and hold the one you want between the ep and your eye. The swatchbooks are by Gambook or Rosco. They look like a set of paint samplers, but in clear plastic.

[GazOC]

A similar tip to Warthogs is to put two different planetary filters in the eyepieces of a binoviewer and then blink from one eye to the other to make the features that each filter shows stand out.

[iancandler]

I guess I should clarify.. The 48mm ones fit the eyepiece srew threads perfectly so I use them just the same as a standard filter. Obviously having a 2" diagonal means that I can fit them in the adaptor for it when using 1.25 eyepieces and not have to mess around changing the filter over for each eyepiece.

[Kaptain Klevtsov]

I was reading somewhere that very deep red filters intended for photography are a cheaper way to get a Ha filter. I'll try to find a link when I get a moment, busy busy, busy at the moment and that's just work.

Captain Chaos

[FLO]

Camera shops usually have a drawer full of secondhand filters that they'll sell cheap (all my filters were obtained this way).

[Jamie]

I was reading somewhere that very deep red filters intended for photography are a cheaper way to get a Ha filter. I'll try to find a link when I get a moment, busy busy, busy at the moment and that's just work.

Captain Chaos

Having read your posts since you joined Stargazers CC i know that you are not a

stupid man so forgive me for the stupid question.

When you say about the photographic filters being a possible way to make an HA

filter of sorts, is this for deep sky or solar?

If its solar what do you intend to put at the front of the scope as in a filter?

[GazOC]

H Alpha falls with the "red" wavelengths but surely a red filter would let far too much other light in as well?

It might work OK for deep sky, you'd probably lose your sight looking at the Sun.

[Kaptain Klevtsov]

I was reading somewhere that very deep red filters intended for photography are a cheaper way to get a Ha filter. I'll try to find a link when I get a moment, busy busy, busy at the moment and that's just work.

Captain Chaos

Having read your posts since you joined Stargazers CC i know that you are not a

stupid man so forgive me for the stupid question.

When you say about the photographic filters being a possible way to make an HA

filter of sorts, is this for deep sky or solar?

If its solar what do you intend to put at the front of the scope as in a filter?

Sorry, should have made this clearer.

NOT FOR SOLAR OBSERVING!!

The page I read was discussing the fact that in Japan the astronomical amateur community like to buy locally manufactured gear as often as possible and have used deep red filters to get close to the performance of a wideband Ha filter for Astro. use.

Must get some more hours in the day, but I'm off to work now, and for me it's the middle of the night still (well, feels like it) and I'll also be back late probably. I'll get the link ASAP and stick it on here.

Captain Chaos

[iancandler]

*update*

Well I tried the filters out last night for the first time and have to report back that I had no problems with them optically at all.

They all worked well with no degredation of the image.

I fitted them all direct into the 2" to 1.25" adaptor for my diagonal.

The blues definatly brought out the cloud belts on jupiter and to be honest even the light yellow warming filter brought out more detail.

I have a feeling that the trick here is not to go for too dark a filters, but to stick with the lighter versions.

I shall definatly be buying more when I see them come up cheap on e bay.