varifocals

[wookie1965]

I have just got new glasses and was advised to get varifocals 2 years ago and now this time so i went and got them this time has anybody got any advice about using these with my scope and generally as im finding it rather strange thank you.Oh and a very Merry Christmas to you all.

[Astro Imp]

I have used varifocals for quite some time and for general use have had no problems. However when using my Tetrad I find when looking towards the zenith I need to take them off as I cannot look through both eyes at once without seeing two images.

When viewing at the eyepiece I used to leave them on but recently I started using Celestron X-Cel  LX EPs and find I now prefer to observe without my glasses with the twist up eye guard right up to exclude as much stray light as I can.

[Bizibilder]

I always take my varifocals off to use the eyepiece - it can be quite tricky getting the right part of the varifocal lens in the right place!

[SnakeyJ]

Glasses, the curse of my middle age!   Fortunately I only suffer from increasing long sightedness, so do not need or use the glasses when at the scope or finder, though they are useful with the Telrad.   However, I definitely need them to focus on the laptop screen when imaging and trying to achieve focus with the cameras.     This leads to much removing and replacing over a night in the obs and I will frequently misplace them or, worse smear them whilst fumbling to grab them!     I must get a neck strap!     My latest prescription pair are bifocals, though still struggling with these after using varifocals for several years.     I was thinking of sending off online for a couple of pairs of cheap varifocals for the new presecription, then I can leave a pair in the obs permanently and it won't be too much of a drama if I drop or tread on them

[Charic]

I  don't wear my glasses using the telescope, however Santa delivered my Telrad, and the reticule is not clear without the glasses?

[majapala]

I have also been afflicted by the longsightedness which often befalls gentlemen of my erm, age. The offing and onning required in between looking through an eyepiece, checking a camera, looking at map etc. etc., whilst wearing gloves, and a hat, which keeps getting pinched by the hinges of my glasses, is a right royal pain in the backside. Has anyone tried a monocle (worn in the non-eyepiece eye? It really does seem to offer many practical improvments! I'm concerned that if I move in this direction, however, then I might as well start wearing a dickie bow, cravat, and a house coat. My optician has already told me my affliction is 'due to my age'. The first time she said it, I thought she was being polite, (age related presbyopia I think she said) although now I'm convinced otherwise, on account of that thing she did with her eyelids when she said it.

[wookie1965]

This is the problem i had wasn't too bad i could manage taking the glasses off viewing through eyepieces but needed my readers for maps and charts now with these varifocals having trouble just looking at computer screen, i suppose i have just got to get used to eye position i will have to see how i go when i get a clear night thank you all.

[JamesF]

And I thought it was bad enough just having to wear reading glasses for close-up work

James

[bambuko]

I've been wearing varifocals for 12 years now and found very quickly that you get what you pay for

Cheaper ones from the usual cheap high street chain were next to useless...

I also found that varifocals don't work very well with computer - ended up with pain in the neck (literally) from trying to see the screen through bottom half of the glasses, so now have dedicated computer glasses.

Also separate reading glasses

The only thing I like varifocals for is driving and flying, where you have to see both distance and close up (instruments and charts).

At night, when observing I use dedicated distance glasses (not varifocals, which I've found restricted my FOV too much) and separate reading glasses.

[tteedd]

Varifocals

Long before taking up astronomy I gave up using varifocals in favour of bi-focals. The reason for this is that I do woodwork and I find it difficult to plane or saw straight with the distortion introduced by the varifocals.

If a manufacturer made an EP with anything like the distortion introduced by varifocals it would get slated.

The main reason for using varifocals is to not look old by wearing bi-focals. You pay a lot in both money and introduced distortion for the vanity.

If you have low astigmatism (1.00cyl) or less I would recommend using no glasses for viewing through a telescope. At the minimum you just introduce more glass, more reflections and probably lower quality optics (especially if you pay a lot for your EP's). In addition it is more difficult to put your head in the correct place.  

 Use the focussing on the telescope.

If you must wear glasses (for high astigmatism [1.50cyl or greater) or because you share a scope which must be in focus for all, then get a pair of good distance glasses with anti reflection coating.

If you must wear varifocals for vanity or simply because you have got used to them, you will find it easier for both looking at the computer and for astronomy if they are 'soft'. 'Soft' and 'hard' in this instance refers to the change in prescription across the lens. Hard varifocals have a rapidly changing prescription which allows large areas for distance and close up but this comes at the cost of high distortion in the areas of change between distance and close.

Most prescriptions come on forms and the word 'Cyl' is pre printed on the form but just in case your prescription is written or typed, your prescription will look like this:

R +/-x.xx  -y.yy  X zz     L+/-x.xx -y.yy X zz

y.yy is the cyl.

When you have your eyes examined you are entitled to a copy of your prescription, from your optometrist, by law.

Long Sight.

If you have a small to medium amount of longsightedness you can usually live with it until your mid 40's. The reason for this is that the lens in your eye can flex to change the focus and overcome the longsightedness. As you get older the lens gets thicker and stiffer and you can no longer focus. Longsighted and even sighted people eventually need glasses for reading. Shortsighted people will have always needed glasses for distance.

Monovision

Is a technique employed with contact lenses where the contact lens in one eye is used for close work and the lens in the other for distance work. It takes a little getting used to but it works well if you can. The point is that if you take the lens out of the right eye on an old pair of glasses you will find that you can use the right eye for the scope and the left eye for looking at charts. Do this however at your own risk and don't blame me if you trip over the door step.

And just to round off - Nightsight.

Many astronomers do not realise that the eyes adjust to light levels individually. This means that if you must use white light to read, or go inside to the loo, you can put a patch over your right eye to maintain your night sight. Use a tight black one and close the eye as well if you can. When you get back outside you will find that you are virtually blind in the left eye but still have your night sight in the right.

Merry Christmas and happy stargazing.

Ted

[baggywrinkle]

I wear varifocals and I generally take them of when viewing.

[cantab]

Varifocals

If you have low astigmatism (1.00cyl) or less I would recommend using no glasses for viewing through a telescope. At the minimum you just introduce more glass, more reflections and probably lower quality optics (especially if you pay a lot for your EP's). In addition it is more difficult to put your head in the correct place.  

 Use the focussing on the telescope.

If you must wear glasses (for high astigmatism [1.50cyl or greater) or because you share a scope which must be in focus for all, then get a pair of good distance glasses with anti reflection coating.

Thanks for this. I have a slight astigmatic correction (-0.75 for the right eye) in my prescription, as well as shortsightedness (-0.5). Earlier tonight I tried comparing the view with and without glasses. At low magnification (12x in the Heritage 76, so a 6 mm exit pupil) I did notice star images were better with the glasses on. Upping the magnification (to 30x, a 2.5 mm exit pupil), I no longer noticed any real difference, and the tighter eye relief (stock SW 10 mm EP) was a bit annoying with the glasses.

I think I'll stick with no glasses for the scope. It does mean faffing around when I want to use the finder or view the sky naked-eye, since I really do need glasses for that.

[wookie1965]

I am lucky that the optician has said to give them a couple of weeks if i cannot get used to them i can go back and they will give me two pair one for all time watching television and going on computer and a pair of reading glasses for no extra cost. They

Varifocals

Long before taking up astronomy I gave up using varifocals in favour of bi-focals. The reason for this is that I do woodwork and I find it difficult to plane or saw straight with the distortion introduced by the varifocals.

If a manufacturer made an EP with anything like the distortion introduced by varifocals it would get slated.

The main reason for using varifocals is to not look old by wearing bi-focals. You pay a lot in both money and introduced distortion for the vanity.

If you have low astigmatism (1.00cyl) or less I would recommend using no glasses for viewing through a telescope. At the minimum you just introduce more glass, more reflections and probably lower quality optics (especially if you pay a lot for your EP's). In addition it is more difficult to put your head in the correct place.  

 Use the focussing on the telescope.

If you must wear glasses (for high astigmatism [1.50cyl or greater) or because you share a scope which must be in focus for all, then get a pair of good distance glasses with anti reflection coating.

If you must wear varifocals for vanity or simply because you have got used to them, you will find it easier for both looking at the computer and for astronomy if they are 'soft'. 'Soft' and 'hard' in this instance refers to the change in prescription across the lens. Hard varifocals have a rapidly changing prescription which allows large areas for distance and close up but this comes at the cost of high distortion in the areas of change between distance and close.

Most prescriptions come on forms and the word 'Cyl' is pre printed on the form but just in case your prescription is written or typed, your prescription will look like this:

R +/-x.xx  -y.yy  X zz     L+/-x.xx -y.yy X zz

y.yy is the cyl.

When you have your eyes examined you are entitled to a copy of your prescription, from your optometrist, by law.

Long Sight.

If you have a small to medium amount of longsightedness you can usually live with it until your mid 40's. The reason for this is that the lens in your eye can flex to change the focus and overcome the longsightedness. As you get older the lens gets thicker and stiffer and you can no longer focus. Longsighted and even sighted people eventually need glasses for reading. Shortsighted people will have always needed glasses for distance.

Monovision

Is a technique employed with contact lenses where the contact lens in one eye is used for close work and the lens in the other for distance work. It takes a little getting used to but it works well if you can. The point is that if you take the lens out of the right eye on an old pair of glasses you will find that you can use the right eye for the scope and the left eye for looking at charts. Do this however at your own risk and don't blame me if you trip over the door step.

And just to round off - Nightsight.

Many astronomers do not realise that the eyes adjust to light levels individually. This means that if you must use white light to read, or go inside to the loo, you can put a patch over your right eye to maintain your night sight. Use a tight black one and close the eye as well if you can. When you get back outside you will find that you are virtually blind in the left eye but still have your night sight in the right.

Merry Christmas and happy stargazing.

Ted

Right is +2.25 cylinder -0.25

Left   is +3      cylinder -0.00

reading addition 1.75  :  1.75

so how bad are my eyes from this my glasses are whatever this means BTS gold 1.5 15mm FREE SR.

Im also lucky as they said if i cannot get used to them bring them back and they will make two pair up one for all the time and one for reading at no extra cost.

[Scott]

I wear v/focals and have done so for a while (10+ yrs). tried bi-focals but found the line between fl to be a right pita. Having said that, my job (cornice/cove fitter) requires me to "get things straight" which is nigh on impossible with vari-focal but a chaulk line sorts that . 

I found wearing v/focals quite odd at first but after a day or two I basically forgot I was wearing them.

I also remove glasses at the eye piece.

[ronl]

Varifocals don't work at the eyepiece, if you need to wear glasses

the single lens are the only glasses that will be of any use, I always 

take mine off while observing.

[RobH]

I got an expensive pair of varifocals about 18 months ago, and tried my best to get used to them but they, for me, we're a total waste of money......they make me feel awful....dizzy and headachy. This is due to the distortion they introduce, and the fact that you have to look directly at whatever it is you're looking at, rather than moving your eyes. As has already been mentioned, for computer use they can be tough to use, and for image processing, they are awful as the distortion they cause off axis makes your stars look distorted.

[wookie1965]

I got an expensive pair of varifocals about 18 months ago, and tried my best to get used to them but they, for me, we're a total waste of money......they make me feel awful....dizzy and headachy. This is due to the distortion they introduce, and the fact that you have to look directly at whatever it is you're looking at, rather than moving your eyes. As has already been mentioned, for computer use they can be tough to use, and for image processing, they are awful as the distortion they cause off axis makes your stars look distorted.

Ive only had these a day and can sympathise with you  about the dizziness and headaches i will give them until after Christmas and if it has not settled down i will have to ask for two pair again.

[sharkmelley]

I got varifocals this time last year.  For the first few days I could only wear them for an hour or two before feeling sick or dizzy.  Now I really love them and wouldn't be without them!  At the telescope eyepiece (or using binoculars), look straight through the centre of the glasses (not the top) and adjust the focus accordingly.

Mark

[JamesF]

And just to round off - Nightsight.

Many astronomers do not realise that the eyes adjust to light levels individually. This means that if you must use white light to read, or go inside to the loo, you can put a patch over your right eye to maintain your night sight. Use a tight black one and close the eye as well if you can. When you get back outside you will find that you are virtually blind in the left eye but still have your night sight in the right.

Ted

Very useful piece all round.  I'd just like to add that if you do this, the first few times it's quite disorientating for the first few seconds as one eye is telling you it's completely blind and the other can see very well.

James

[Paul M]

I've been in Varifocals since my early 20's and won't be without them. I found them quite natural to use. I just had to be careful using steps and ladders. The ground had a habit of looking closer than it really is sometimes and more than once I've stepped down from the second step rather than the first. It jars the back somewhat. 

I started with Bi-Focals but at that age people assumed I had cracks in my lenses and thought it necessary to tell me!

I always take them off at the eyepiece and when using bins. There is actually only a narrow zone of functional lense in a varifocal lense due to how it is ground. I find there are too many distortions in widefield views that are much worse than my mild astigmatism when looking at stars.

I need them to see the stars when just looking at the open sky. The optical qualities of varifocal lenses means that off axis stars aren't well focused and far off axis they are blurred worse than when not wearing glasses at all!

It isn't a huge problem but I'm considering getting a pair of single vision "distance" specs just for stargazing

[bambuko]

There is one problem with varifocals that can be quite embarrassing - before I could look discreetly at something without making it too obvious... with varifocals, because of the way they work you have to point your whole head at what you are trying to see (no discreet sideways glances ), but I guess it doesn't matter for astronomical use.

[M4lcs67]

I have varifocals also. In fact I have only worn glasses of any form for a year. I have to take them off when looking down the eyepiece, but have to then put them back on to look at the controller of my scope. I find it very frustrating, but I cannot see a way of making things easier.

[JamesF]

I find it very frustrating, but I cannot see

Hah!  I see what you did there

James

[Naemeth]

Leave them off . You should only be wearing glasses at the eyepiece if you have astigmatism - I have mild astigmatism in both eyes but it doesn't bother me at the eyepiece as these current glasses don't allow me to get very close (20mm eye relief still has me pressing my glasses up to my face, so I just take them off).

[Astro Imp]

As I mentioned in post #2 I have had varifocals for some time (about 12/15 years) and don'e have a problem. Reading through this thread and seeing that many posters report distortion and odd feelings I can only think that I have been lucky or others have been supplied with inferior glasses. The thing that does present a problem is when doing some DIY tasks and looking up in restricted spaces as it is difficult to look through the bottom part of the lens.