2" filter is just barely too small for 2" diagonal.

[lohrphoto]

Has anyone had this problem before?   I just bought a 2" Celestron OIII filter thinking that 2 inches is 2 inches. Surely if a 2" filter says it's 2", it will fit into the threads of a 2" diagonal?   This doesn't seem to be the case with this filter.  It just barely is too small... just enough so the threads don't catch.   Has anyone experienced filters that are just barely too small?  Is it just becuase it's a Celestron filter and a Meade diagonal?  Is there some sort of adapter to fix this issue?

 

[sbooder]

Do other filters fit the diagonal?

[Dave In Vermont]

Do you have a 2" eyepiece with a threaded barrel? If so - try it there. If it fits - the diagonal is off. If it doesn't fit - the filter's thread/size are off. And these threads are supposed to be standardized - whether Meade or Celestron, 2 inches is 2 inches.

Good Luck,

Dave

[sbooder]

I just realised, this is a thread thread!

[GavStar]

I've had many more problems with threads for 2 inch filters compared with 1.25 inch, particularly on diagonals. My baader 2inch filter fits fine on my eyepieces but struggles more with the 2 inch diagonals, even though I have changed both the filter and the diagonal! Threads do seem to be an issue with 2 inch filters generally I think.

[Merlin66]

They should be a standard M48 filter thread.

[Skipper Billy]

I have just had a very similar issue - see http://stargazerslounge.com/topic/228878-simple-filter-size-question/

It turns out that the filter is spot on but the adapter was actually an M50 thread not M48 !!!

If you have got a vernier gauge or calipers the outside of the male thread of the filter should measure 48mm diameter - the inside of the female thread on your diagonal should measure 47mm - giving 0.5mm interlock all the way round.

Sorry it doesn't fix the issue but at least you will know which part is at fault!!

You could always put a couple of tuns of PTFE tape on the filter threads - at least it would stay in place.

[lohrphoto]

Thanks everyone for your replies - Other 2" filters do infact fit the diagonal, just not this one.  I did find that the filter fits the threads of my T-mount, so at least I can use it for photography, but as for viewing I only have 1.25" eyepieces.  Guess I'll just have to save up and get the same filter in 1.25"