A cautionary tale...

[pwalsh61]

Yesterday I was taking a look at my new WO Megrez 72 DDG and familiarizing myself with it. I bought it from Ian King Imaging (excellent service by the way) with the 2" carbon fibre dilectric diagonal and though I'd try out one of my 1.25" eyepieces. Unfortunately, the one I tried happened to be a 6mm (one of a set I bought from Scopes 'n Skies a couple of years ago) which has a top narrower than the steel "nose". To my horror it slipped straight through the 1.25"/2" adapter and hit the prism, leaving a slight mark. Fortunately, the mark doesn't appear to be in the field of vision of my 1.25" EPs, though I don't know if that'd be the case with a 2" EP, and as the diagonal won't be used when I've got a DSLR attached it won't affect any images.

To prevent me from making the same mistake again I've wrapped a few turns of insulating tape around the EP body to prevent it from slipping through. So, a word of caution to anyone with 1.25" EPs and a 2" diagonal with 1.25"/2" adapter, either:

a) Take the adapter off the diagonal, fit the EP to it, then returned it to the diagonal.

or

Do as I've done and wrap insulating tape around the EP body to make sure it won't slip through.

[pete_l]

Well, that's one of your christmas presents sorted. Sounds like you could use a set of parfocalising rings!

Revelation Parfocal Ring for 1.25 inch Eyepieces

[John]

Sorry to hear about that and thanks for the warning. To be honest it's very unsual for the black part of the eyepiece barrel to be narrower than the bottom part, without at least some form of moulded ring to stop just what you have experienced. As pete_l says a par focalisation ring will prevent it happening again with that particular eyepiece.

[pwalsh61]

Thanks for the suggestion. I must admit I'd not heard of parfocal rings before today! Looks like a set might come in handy - especially when I use a webcam.

[Moonshane]

I have a similar problem with my 6-3 Nagler zoom which hits filters screwed into the 1.25-2" adapter. I used a couple of glassless filter rings to sort that out. might get a Baader fine tuning ring eventually.

[pvaz]

Thanks for the suggestion. I must admit I'd not heard of parfocal rings before today! Looks like a set might come in handy - especially when I use a webcam.

A word of caution on the parfocalizing ring:

The one I got presses the barrel with 2 screws which leave very noticeable marks. I'm using mine on the Ethos 10mm and if I ever want to sell it on it might drop the price a bit.

Anyway to me thats not much of a problem. As long as the optics are mint I don't mind the barrel marks at all. Besides I didn't have enough out focus for the Ethos so I do need the ring to make it easy to use, avoiding extension tube hassles.