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I agree

Confusion around 31mm filters

04 Jul, 2019 02:21
Hi everyone,

I am looking to purchase this filter wheel from ZWO and these filters from Astronomik.

The details for the filter wheel says it accepts the use of 8 x1.25″ mounted or 31mm unmounted filters. I emphasised the unmounted part of that as that is where my confusion is, as the filters details say 31mm round mounted. 

I have tried searching all over the place but cannot find any solid information as to whether or not those filters will fit in that filter wheel. All other filter sets of the same 31mm size that I have seen say unmounted.

Does anybody know if those filters will fit in that filter wheel?

04 Jul, 2019 06:30
Hi AstroPhil,
31mm mounted will not work with you. if you want mounted filters, you're left only with 1.25.

if you really need the 31mm version, you'll have to look for unmounted.
04 Jul, 2019 08:03
I think the ones from the link you posted should work.
Usually 31 mm filters are named as '1.25" filters' when they are mounted in a threaded cell and as '31mm filters' when they have only a protective plastic edge or, in some cases, when they are only glass.
In the description of one of the astronomik filters is written: - The H-alpha 6 nm CCD Filter, size 31 mm (1.25-inch) Mounted in Low Profile Non-Threaded Cell by Astronomik -.
Maybe is that 'Mounted' in the sentence that caused the confusion, because to me they looks exactly the same things other manufacturies put on their 31mm unmounted filters. Also from the picture I would say they looks exactly like the 31mm unmounted Astrodon for example.
Anyway to dispel any doubt the best would be contact Astronomik and ask for measurements.
Edited 04 Jul, 2019 08:07
04 Jul, 2019 23:33
No expert here, but if they are 31mm mounted and don't fit, simply remove the filters from the mount.  I have a ZWO filter wheel that takes 1.25" mounted or 31mm unmounted filters.  To use the unmounted filters, there are screws that hold the unmounted filters in place.
05 Jul, 2019 03:34
Hey everyone, thanks for the replies really appreciate it. There is still confusing/conflicting information so as VuurEnVlam said I'll be contacting Astronomik to be 100% sure before I pull the trigger on them. I'll update once I have the answer  smile

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