ZWO Mini-EFW Question

garyi

Sam,

You have said that the unit will handle 31mm filters (in addition to 1.25"). I am leaning towards the 31mm size to reduce the possibility of vignetting. Two questions:

1. Will one carousel fit either 1.25" or 31mm filters, or is there a need to purchase separate carousels for both sizes?

2. The only option that I can find for 31mm filters is for "31mm rings". Does the 31mm size need to be completely unmounted, or is it OK for them to be mounted in a ring?

Thanks,

Gary

Sam@ZWO

you don't need extra ring for the 31mm filter

1.25" and 31mm are together

EFW.jpg

robertm

Excellent news, I see the EFW is available for purchase and even better there are EOS and AIS adaptors for use with the ASI1600...

I think you mentioned about a bundle with the ASI1600 and EFW, might have been on Cloudy Nights - will that be available soon ?

Best wishes

Robert

oldskyeyes

Hi,

noob question:

1.25" = 1.25 * 25.4mm = 31.75mm

So how can the 31mm filters have less chance of vignetting if they are the same size?

Thanks

garyi

OldSkyEyes,

That's a good question. The nominal dimensions are misleading. I'm no expert, but my understanding is that the true aperture of a 1.25" filter (excluding threads and rim) is 24mm, vs. 28 mm for a 31mm filter.

Gary

oldskyeyes

ok, I know this sounds stupid but what is the size of the 36mm filter?

garyi

I don't know. But you need to be careful to distinguish between "size" and "aperture" of a filter. For me, size is the diameter of the filter. Which is 31mm for a 31mm filter, and 36mm for a 36mm filter. But because of the way that any filter has to seat into a lipped or threaded hole in the filter wheel, the actual usable filter diameter ("aperature") is always going to be a few mm less than the size. So for a 31mm filter, it is about 28mm. My guess would be that a 36mm filter would also have about 3mm less, so 33 mm.