Filter threads on eyepieces

[Rob Atkins]

Me again   with another puzzle.

For my telescope, I've bought two new eyepieces : Meade superplossl 32mm and Meade 8-24mm zoom, both very good so far.   I've also bought three filters - Lumicon UHC filter, Celestron Moon Filter and Antares 82A light blue filter.  Here's the puzzle : I would have thought that the filters would all  screw easily and precisely into the eyepieces, but while the Antares filter is indeed precise, the Celestron filter is a bit hit-and-miss (probably because it appears to be made of cheap plastic), while the Lumicon barely threads at all, and it feels very precarious using it on my reflector telescope, in case it dis-lodges.  Is there an explanation why they should be so different - different gauge threads ? 

[mitchelln]

The thread is very fine and I think sometimes when they coat the metal ones they get material in the threads. It doesn't take much to interfere with the fit. Try gently screwing and unscrewing them a few times.

[Langy]

I would have thought just quality of build.

The plastic would be so different to a precise metal thread as it is cheaper to start with.

I've only bought a couple of cheap filters so far from eBay but they are both metal units and will in fact screw in to each other nicely if I need to use them together.

You may find that they get better when screwed on / off the EP a few times as the plastic may need bedding in as they are such a fine thread.

[rwilkey]

The Celestron Moon filter with the plastic frame is not very good in my view, better to get something a bit better quality with a metal frame, say an ND96-0.9. I am surprised at the Lumicon, though I agree that the thread is a little fine, but it should work out ok if you are careful, I find the Lumicon are the best filters for me.  Bear in mind that the thread/gauge on the eyepieces themselves may also vary, I don't think Meade are all that good.

[LukeSkywatcher]

Filters can be tricky to screw onto eyepieces. As has been said, its usually a case of the threads on filters (or even the eyepieces) having a thin layer of paint or whatever on them. Aligning the threads can be tricky also.