Jump to content

Banner.jpg.b89429c566825f6ab32bcafbada449c9.jpg

Specs

robindurant

By robindurant
in The Astro Lounge

Recommended Posts

robindurant

robindurant

Posted
Posted

I am one of the unfortunate who have to wear Glasses for reading and for distance and the ones I use are Varifocal. I want to get a pair specially for viewing and do not know whether they should be reading or distance to give me the best results. Any ideas? I can just see enough in the dark without glasses without knocking my Scope over!

Link to comment
Share on other sites
Whippy

Whippy

Posted
Posted

As a permanent glasses wearer because I'm essentially blind without mine, I tend push my glasses onto my forehead when I'm looking into an eyepiece. Drives my wife mad because she has to re-focus everytime she looks after me!

Link to comment
Share on other sites
barkis

barkis

Posted
Posted

Robin, I wear bi-focals all the time, butwhen I am viewing through the scope I always use the distance segment of the lens.

As you are going to be spending money to do a special need pair, I would seek professional advice too.

Ron. :)

Link to comment
Share on other sites
Trevor

Trevor

Posted
Posted

This is quite interesting, in target shooting we use glasses that have a focal length of around one meter, just a tad longer than the sight base depending on the individual, I wonder if glasses with a focal length of the telescope used would work better?

Link to comment
Share on other sites
Robd

Robd

Posted
Posted

Robin, like you I wear Varifocals and like Barkis I use the distance area for viewing. Mainly I think because it is the most comfortable position. I went through a similar debate with myself when trying to decide on the correct diopter setting for the DSLR. Quickly came to the conclusion that distance was correct - tilting the head back to focus on distant objects was just not right.

Therefore camera and scope I use the distance part of the glasses.

It is also worth bearing in mind what else you need to do before going to dedicated glasses.

How is your camera set ( dipoter )

Do you use a pc etc.

Looking at starcharts

Adjusting setting circles

Etc, etc.

You could end up with good specs for viewing but having to revert to the varifocals for all the other bits.

I have this problem when I wear my sun glasses - these are distance only. This is Ok for taking pictures ( no not the night shots :) ) but I cannot check them afterwards since I cannot focus on the back of the camera.

Rob

Link to comment
Share on other sites
Astroman

Astroman

Posted
Posted

I've been in a number of discussions about night-time specs and the consensus is to tell the optician their intended purpose, because the larger opening of the pupil in low light conditions will change the focal characteristics of the glasses. Ask your optician about a wider pupil during observing and he/she should be able to make you nice pair.

Link to comment
Share on other sites
mand

mand

Posted
Posted

Well, I am an optician (optometrist), but an astronomy newbie. This is what I think:

I assume the light rays exiting an eyepiece are parallel, so then distance correction is needed.

A target shooter needs to be able to see the foresight reticule, reasonably clearly, superimposed on the target. Astronomers don't have this requirement, except for the polar scope or finder where you can sometimes adjust the reticule to look sharp when looking into space.

The pupil size at night has no effect on specs performance, but can allow some aberrations of our eyes optics to come into play, and has a bearing in relation to eyepiece exit pupil size.

So get some distance specs made, but then don't expect to see a starmap/ setting circles/goto controller with them.

Hope this makes sense or even helps

Mand

Link to comment
Share on other sites
mand

mand

Posted
Posted

Hi. yes, astigmatism will affect your sight without specs on. It causes two points of focus, so you may notice a ghost image type effect without specs. This is not too much of a problem for low amounts.

If you have a copy of your spec prescription, look at the number in the 'cyl' column : a number of 1.00 or less is not too bad, especially if the 'axis' is 90 or 180.

Robin, the 'older' eye (sorry), often has smaller pupils that take longer to dilate, so give yourself plenty of time to dark adapt.

Glad to have helped, Mand.

Link to comment
Share on other sites

Archived

This topic is now archived and is closed to further replies.

Go to topic listing

  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.