My turn for daft question - twist up eyecup

[RascalUK]

I know the answer to this is going to be glaringly obvious but on an eyepiece such as a TMB Planatary - why can you twist up the eyecup? I presume it may be to do with eye relief. As a glasses wearer where should it be?

[NGC 1502]

Well it's mainly because with eyepieces that have a good long eye relief, if your

eye is too close, you can get shadows intruding into the field of view. It's an optical

effect if your eye is inside the eye relief.

Also, many folk, including myself, find it much easier if the eye socket has somewhere

to rest, rather than hovering around the best position.

If you wear specs, then adjust the eyecup so that you can see all of the field of

view, with the lens of the glasses just touching the rubber eyecup.

The advent of long eyerelief has been wonderful for spectacle wearers (and the

rest of us actually !)

Best regards, Ed.

[Nexus 6]

Hi, would second Ed 's comments, long er is very comfortable for the observer, the twist up eye cups work very well and a lot of manufacturer's are now selling ep's with that sort of design

[RascalUK]

Cheers guys. Now just need the chance to use one!

[ronin]

If you wear glasses then have them down.

If you don't wear glasses then have them up.

That way the eye is at (approximately) the right position in either case.