Glasses or no glasses?
Published on Nov 27, 2006 at 4:42 pm.
2 Comments.
Filed under amateur astronomy, observing.
I am getting new glasses soon. I need a new prescription, and besides I got the anti-reflective coating on my old pair pretty scratched up (no coatings on the new pair!). But, this raises a question that people always ask at public star parties. Should they take off their glasses to look through the telescope?
Well, that really depends upon the individual. Perhaps I contributed to my glasses being scratched by bumping them into the eyepieces. But, otherwise, I’d have to be taking them off and putting them back on continually during the labs that I teach, and that would be hard on the frames. And, besides, I tend to be a bit lazy. If I were sitting at one telescope a lot, then it might be different. But, I am often moving from one to another, and my vision is so poor when uncorrected that I simply cannot see without my glasses on. That means taking them on and off a lot, which is a bother and subjects the frames to potential damage, not to mention the increased possibility of dropping them.
The range of focus on the telescope should be enough to bring things into focus without glasses for almost anybody who normally wears glasses, no matter how bad their vision. But, then whoever walks up to the telescope after you will be unable to see anything!  All too often, at star parties there will be a line of people looking into a telescope, going “oohh” and “ah”, and then when I look in the eyepiece to see if what they are supposed to be looking at is still in there I find that someone has refocussed and nobody had been seeing anything but a big blur for several minutes! That would only be worse if I did it, too!
But, there are a couple of cases where the “glasses on” or “glasses off” decision is a bit easier. One is if you have severe astigmatism. That means that your eye focusses better one way than another.  The telescope does not correct for astigmatism, so you are probably better off leaving your glasses on.
Conversely, if you have bifocals, then it is better to take them off because wearing them at the eyepiece means that part of the view will be in focus and part will not. You can either focus for the distance part or for the reading part, but not both at once!
So, there you have it. There is no clear cut answer as to whether you should take glasses off or not to look through the telescope. If you are a casual observer at a star party, then it doesn’t really matter. It would be a matter of personal preference.
-Astroprof
Zavatar on November 28, 2006 at 6:59 pm: 1
Have you considered using contacts? I also wear glasses and I tend to take them off when I’m at the scope, but when I’m using my contacts, it’s much easier. I can just observe trough the telescope and switch right away to my notepad without having to fumble around for my glasses
Astroprof on November 28, 2006 at 9:45 pm: 2
I’ve thought about contacts, but I am used to glasses. I tried contacts many years ago, and I didn’t do well. Things are different today, of course. Maybe one day I’ll think about trying them again.