Filter sizes???

[ollypenrice]

Does anyone understand filter sizes? I'm blowed if I do. I use an Atik EFW2 with carousel for '2 inch mounted filters' (Atik's description) and I use bog standard Baader 2 inch mounted filters and 2 inches should be 50.8mm if I'm not mistaken.

I would like to switch just the Ha to an Astrodon 3Nm but then the fun begins. Astrodon don't make anything they call '2 inch mounted' but make 50mm filters with a 52mm filter holder.

The threaded holes in my carousel for '2 inch Mounted Filters' looks like about 48mm so I don't suppose a 52mm filter holder will fit it, though maybe the thread isn't 52mm?

How on earth did the industry get itself into this mess? Good job I'm already hairless.

Olly

[Gina]

Weird! Yes, AFAIK 2" filters have a 48mm thread.

[Merlin66]

I think the terminology comes from the eyepiece size...a 1.25" filter has a 28.5mm thread, a 2" has, as Gina said, a 48mm thread.....

[ollypenrice]

Thanks both. It seems that I simply can't put an Astrodon 50mm in my carousel. How annoying.

Olly

[Gina]

I find it hard to believe that either Astrodon don't do large filters to fit the popular Atik EFW2 or that Atik don't do a carousel to match the large Astrodon filters.

[Gina]

Atik do a carousel that takes unmounted 50mm filters - http://www.firstlightoptics.com/atik-accessories/atik-filter-carousel-for-efw-2.html So I guess you could take the 50mm Astrodon filters out of their mounts.

[ollypenrice]

Yes, you can buy the AD's unmounted but I only want their NB filters. It isn't just cost, it's the fact that I've struggled with colour using thier RGB set. I've worked on three images now, through those filters, and I don't really click with them. This is a minority opinion, I must stress, since many of the best imagers in the world swear by them.

So you can't mix ADs and Baaders in the sme carousel. Groan.

Olly

[davew]

If the clear aperture of each hole is 48mm, you could have three small threaded holes made around the filter hole. Then get three special screws and washers to hold the 50mm unmounted filter.

Some filter wheels come this way so you can use either. IE. http://ccd.mii.cz/image?id=1025

Or email Don and ask for a 2" mounted ?

Dave.

[ollypenrice]

If the clear aperture of each hole is 48mm, you could have three small threaded holes made around the filter hole. Then get three special screws and washers to hold the 50mm unmounted filter.

Some filter wheels come this way so you can use either. IE. http://ccd.mii.cz/image?id=1025

Or email Don and ask for a 2" mounted ?

Dave.

Yes, this is true. Good idea. It's certainy tempting to try, but the downside might be getting it wrong and breaking a billion dollar Astrodon...

Olly

[Gina]

I'm using a mix of Baader LRGB and AD NB in my EFW2 and although I don't have a mounting problem I do have a problem with the Baader filters being 2mm thick and the ADs being 3mm thick so the focussing is very different. I'm toying with the idea of buying AD LRGB filters so that they match parfocal-wise. That's when I manage to accumulate any funds though.

[ollypenrice]

I'm using a mix of Baader LRGB and AD NB in my EFW2 and although I don't have a mounting problem I do have a problem with the Baader filters being 2mm thick and the ADs being 3mm thick so the focussing is very different. I'm toying with the idea of buying AD LRGB filters so that they match parfocal-wise. That's when I manage to accumulate any funds though.

I think this is possible in the smaller size. As I said earlier, I struggled with the AD RGB. I found the teal blue colour hard to work with and couldn't get the green to behave as I'm used to with regard to adjusting the blue-magenta balance. Maybe just a question of practice.

Olly