what size filters? do i need a wheel

[sooot]

so ive decided to get a Atik 383L+ mono, I know what filters im getting but do I get 1.25 or 2.....mounted or unmounted what the difference apart from the price, is a wheel really needed or is it just for ease of changing the filter

[JamesF]

This thread may be helpful:

http://stargazerslounge.com/topic/105860-1st-with-383l-ngc-6888-in-ha/

It does sound like you're very marginal with 1.25" filters.

Personally I'd say you really want a filter wheel otherwise you'll have a pig of a time getting the framing sorted after changing filters.

James

[sooot]

ok well might just dip into the wallet and get 2" filters. was looking at the Brightstar 2inch Manual Filter Wheel, might be a dumb question but do you use mounted or unmounted filters or do these things do both, ive looked around but cant find the answer

[Uranium235]

Im using 1.25" with my 383, but its pretty close. Two of the far corners are pretty dark in the flats, but using proper calibration sorts it out.

Trouble is, you need to find a way of butting the camera right up to the wheel without using the supplied male/male t-adapter. The best way I found, was to make my own continuous male thread adapter by hacksawing an old t-extension with a long-ish thread (a vice was needed to hold it steady). Though these continuous male threads can be brought from TS.

The above of course, is all avoided with 2" filters, but your wallet will be a lot lighter!

[RAC]

This is another option and is what I use with my 383L. I use 1.25in filters. They are fine at f5 but not so much at f4 but on the other hand when used with a canon lens there is no problem at f2.8. It's also nice and light and small.

http://www.teleskop-express.de/shop/product_info.php/info/p2165_Filter-Quick-Changer-incl--1x-1-25--filter-drawer---low-profile.html

[ollypenrice]

Baader do an intermediate filter size for this chip. I can't remember what it is but it's a good compromise. 2 inch filters are darned expensive and can cost more than the camera.

The Atik EFW2 will fit flush to the camera, or mine certainly does, adding no length. You choose the right carousel for your filter size/type where manufacturers offer alternatives, as Atik do.

Olly

[JamesF]

Baader do an intermediate filter size for this chip. I can't remember what it is but it's a good compromise.

They appear to do a 36mm LRGB filter set, but without the cell. No idea where you'd get the cells from, but then using uncommon filter sizes probably comes with a load of other problems to solve, too.

James

[Gina]

You can get filter wheel carousels that take 36mm unmounted filters. eg. Atik do a 7 hole one for their EFW2 wheels. I don't know of any problems with them. They will cover APS-C size sensors as well as the 383.

[davew]

1.25" are right on the cusp of usability with the 8300 chip. Some say they are fine and calibrate out and some say they don't !

Different manufacturers use different sizes. Moravian and QSI, who both get their filters very close to the chip use 31mm unmounted. SBIG who don't get their filters in so close use 36mm unmounted. Maybe there is a clue there ? Moravian and QSI can use 1.25" filters, and I know some do with the QSI, but they aren't really recommended as far as I know.

Atik make 1.25" and 36mm unmounted so the choice is certainly available. The machining required to be able to use both 1.25" and 31mm in the same wheel is fairly simple and I don't know why Atik don't do it. If anyone wants to test their Atik wheel it's quite simple. Take a flat with the Lum 1.25" filter in place and then a flat with no filter. That's the difference you'll see with the two filter sizes because the wheel hole on it's own equals the 31mm size.

1.25" and 31mm filters cost the same. 36mm filters a bit more. 2" filters cover most eventualities but cost more again.

The best answer would come from someone who uses the same scope as you and could show you a flat straight from the camera.

Dave.