Red filters for double stars - quality worth it?

[Moonshane]

Hi all

I have read a few times recently that red filters allow the reduction of atmospheric effects when observing planets, moon and doubles. I am particularly interested in the latter as seeing often affects the ability to split double stars and I'd like to improve this if possible.

There are three red filters (light red, red and deep red) and I presume that the deeper the red, the better the reduction in poor seeing? But I further assume that the darker the filter, the larger the aperture required to see the fainter targets?

I was therefore thinking of the middle ground and getting a #25 Red filter. I normally buy decent quality filters and in 2" if possible and wondered if there's any benefit to buying one of the two apparent options Lumicon and Baader which are both about £35 for the 2" filter. I can get a cheapie Antares 1.25" for £6 from SNS. Is it worth getting the better quality filter in this case? (ignoring the convenience of the 2" filters for a moment).

cheers

Shane

[Stargazer_00]

With no experience to advise you I'd go purely on taking a punt. As you want it for doubles just get the 1.25" for now. I can't imagine much engineering goes into making a wratten, so cheap would work fine.

[Moonshane]

cheers. you are probably right but I keep getting that nagging doubt about, well spend £6-10 or £35 and know you have the best possible optical option.....

[Stargazer_00]

It's just the engineering involve though. As far as I know the colour filters are all very simple in their contstruction. If you were going for a specific narrow band pass filter or something I'd obviously side with you on getting the best you can afford. Not colour filters though in my opinion, this is the sort of thing you get the same whatever you spend.

and at £6, it's no big loss. You may have use for it one day as a spacer or something.

[michael.h.f.wilkinson]

I simply used the R-band interference filter in my LRGB set (Astrolumina). The deeper the red, the better in terms of reduction of seeing effects. There is a downside: the longer the wavelength, the lower the resolution, and the narrower the band, the less light is transmitted. Any narrow single-band, filter will reduce the effect of atmospheric refraction for objects at low altitude.

[chiltonstar]

Mine is a cheapo light red, which seems to work.

Chris

[Moonshane]

I think a main difference is that cheaper filters are stained optical glass but the more expensive ones are better figured optically and have various coatings applied including anti-reflective multi-coatings. I'd expect these to provide more clean images although maybe I am just being suckered.

[Moonshane]

maybe I should just try one of my other filters first. I have a Castell Oiii and UHC, a Skywatcher Hb and a Baader Solar Continuum.

[Stargazer_00]

I was looking at michael's post and wondering if my baader solar contiunum would work for this too absolutely no harm in trying is there!

[michael.h.f.wilkinson]

I think a main difference is that cheaper filters are stained optical glass but the more expensive ones are better figured optically and have various coatings applied including anti-reflective multi-coatings. I'd expect these to provide more clean images although maybe I am just being suckered.

Stained filters do not have a sharp cut-off that interference filters have, so other frequencies also get through, and the transmission of classical filters is lower. I found both UHC (Sirius A became a double star with one reddish and one blue-green component) and O-III (single blue-green, but seeing horrible) did not help nearly as much as plain red.

[Moonshane]

cheers Michael

I think that makes my mind up. I am going to grab a Baader one (or the Lumicon) when funds allow.

[Stargazer_00]

link the cheap one, ill pick one up for a punt and see if i can split better with it.

[Damo636]

Off topic Shane but did you ever get to try out the H-Beta on the Horsehead?

[Moonshane]

link the cheap one, ill pick one up for a punt and see if i can split better with it.

hi mate

this is the one I saw

http://www.scopesnskies.com/prod/no25-colour-filter.html

[Moonshane]

Off topic Shane but did you ever get to try out the H-Beta on the Horsehead?

hi mate

unfortunately conditions have been against me since I got it. I will try on the California Nebula though when this comes about or if I get a chance at the HH I'll do so but running out of time now. maybe this weekend, we'll see.

[Stargazer_00]

Orion is way past its best now

I'll give that filter a punt. It says it might boost contrast on planets too. At that price you can't really care either way