SW 0.9 Coma Corrector and 2" Filter - will it fit?

[adyj1]

I've just got an ASI533MC which came with a 2" UV cut filter.  I can screw it in to the end of my Altair Astro 1x Field Flattener (for my small frac), but there doesn't seem to be enough thread clearance at the end of my SW 0.9 coma corrector that I use on my 150PDS...

In the pic you can see the 'inner ring' on the SWCC which has a notch in it to help tighten/loosen and is undoubtably there to hold the CC lenses in... This is thread right size for the filter, but there's no thread showing.

In contrast, in this pic of the SWCC on the FLO web site, you can see that there are a number of threads showing - and I assume the 2" filter would screw in nicely (as advertised)...

 

So $60,000 question (well, actually it is a £149 question +P&P); can I screw in the inner ring on my CC so that it exposes enough thread for the filter without completely trashing my CC ???

Advice appreciated, and if there's someone out there who has actually done this, then that would be great...

My CC is now way, way, way out of warranty (which, thinking about it, may actually be the problem - maybe in the olden days they was never enough thread for a filter?)

Thanks

Ady

[Stu Wilson]

It fitted on mine ok. But as I've now sold it I can't check it's the same as yours. Pretty sure it was tho.

 

Stu

[alacant]

Hi

Assuming the existing ring bears up against the glass, don't tighten any more. If the glass rattles the turn clockwise until the lens is held loosely but without lateral movement. If not...

Remove the existing cc retainer then screw in the filter carefully a bit at a time into the now exposed thread.

Check to see if it holds the front element by bearing -gently- up against it or, if it goes fully home, rattles when you shake it. If the latter swap the fat ring in the cc for the thin ring in the filter.

HTH

Edited May 24, 2021 by alacant

[adyj1]

1 hour ago, alacant said:

Hi

Assuming the existing ring bears up against the glass, don't tighten any more. If the glass rattles the turn clockwise until the lens is held loosely but without lateral movement. If not...

Remove the existing cc retainer then screw in the filter carefully a bit at a time into the now exposed thread.

Check to see if it holds the front element by bearing -gently- up against it or, if it goes fully home, rattles when you shake it. If the latter swap the fat ring in the cc for the thin ring in the filter.

HTH

Sounds like good advice, and replacing the retaining ring with the filter might be an option... 

I had another thought - Is it OK to put the filter at the end of the CC, or should it be closer to the sensor? 

Edited May 24, 2021 by adyj1

[alacant]

It's easier to attach the filter to the telescope side of the cc. If your camera allows, you maybe able to incorporate it at the camera side.

Best to post a shot of the cc, the setup at the focuser and tell us which camera you are using that we nail it.