About glasses, distortion & anti-reflective coatings

[pipnina]

I just got my new glasses witch a very slightly different prescription. And noticed instantly that the sharpness reduces a lot at the edge of my peripheral vision, chromatic aberration is quite intense near the edges and everything seems to be stretched. I brought this up with the optician and they said "The glasses are definitely made accurate to your prescription (after checking) and they are sitting in front of your eyes as they should. She also mentioned that, because I asked for the lenses to NOT have thinning this time around this could be causing it. I'm not convinced.

Which brings me to Q No.1: Are glasses inherently bad like this? Or are the ones I got just terrible?

Also, when I asked about cleaning glasses with anti-reflective coatings, they said "A lot of cleaning products, especially the wipes, are quite strong and people often scratch their glasses because of them" and offered me a "Coated lens cleaner" and said to use the supplied glasses cleaning cloth for them... Q No.2: Is this stuff safe to use for eyepieces/finderscopes/refractors/binoculars? Or is proper stuff (like baader wonderfluid) the only way to go?

Q No.3: If I ground my own lenses to make a scope, would it be possible to give them anti-reflective coatings? I've read the coating is a film fused to the lens surface and there are several different types. Are coatings too specialised to get your own lenses coated?

 

Thanks!

    ~pipnina

[DaveS]

I've noticed CA towards the edges of my glasses but they are quite strong and made of a high refractive index resin.

Anti-reflective coatings are vacuum deposited, and even the old magnesium fluoride type would be beyond the scope of most amateurs (Except perhaps Gina ). The modern broadband AR coatings are made up of many layers of different materials and are way beyond any amateur, even Gina I would guess .

I'm a bit rough with my glasses, as like as not to give them a squirt of window cleaner and polish off with a microfibre cloth.

[Stub Mandrel]

I have signficant CA at the corners of my glasses (-3.5 dioptre). I can do things like make the different parts of illuminated Tesco and HSBC logos dance around.

When the coatings on your glasses craze, you can get it off with Armour Etch and get another year or two out of them ;-)

[DaveS]

With point source LEDs my glasses can often separate the blue energising LED from the broad fluorescence.

As an aside, I've asked my optician for as pair of distance glasses for astronomy, as my normal ones are varifocal so only have a narrow strip of distance correction.

[bejay1957]

I have varifocals, and have found various CA and distortions at the edges depending on the shape of the frame/lens - and yes acknowledging my eyes change, not least the time my astigmatism rotated 180!  In recent times I've avoided frames with a wide lens area, they seem to create the worse distortion at the outer edges; so now go for a 'rounder', and deeper frame to maximize the tri-zone coverage for driving and computer/office.

Oddly enough my newest glasses (from Apr-2015) have started to give considerable problems, it looks like the coating is clouding (I clean with glasses wipes).

[opticalpath]

Regarding cleaning the lenses of spectacles .... I find that anti-reflective coatings have a useful secondary benefit - they seem to make the lenses somewhat hydrophobic - which means that water tends to run off the surface easily.  I clean my lenses by sloshing them around in some warm soapy water, wiping very gently between finger and thumb under water if necessary, then rinsing off by holding under a gently running tap (lenses vertical).  The trick is to move the specs smoothly from left to right so that a smooth stream of water moves once across each lens surface.  With practice, the final water rinse just runs off cleanly leaving no residue or droplets, so no drying or polishing of the lens surface is required.

Since using this cleaning method, I've found that the lenses stay scratch-free much longer compared to using any kind of cleaning cloth regularly.  Now I wince when the assistants at my local optician give my specs. a good polish with a cloth before handing them over to me!

Adrian

[pipnina]

4 hours ago, bejay1957 said:

I have varifocals, and have found various CA and distortions at the edges depending on the shape of the frame/lens - and yes acknowledging my eyes change, not least the time my astigmatism rotated 180!  In recent times I've avoided frames with a wide lens area, they seem to create the worse distortion at the outer edges; so now go for a 'rounder', and deeper frame to maximize the tri-zone coverage for driving and computer/office.

Oddly enough my newest glasses (from Apr-2015) have started to give considerable problems, it looks like the coating is clouding (I clean with glasses wipes).

I'll have to try that! When I used the "Coated lens cleaner" on my glasses earlier it was like I put a thin layer of Vaseline on them. They now have 10x the glare they started with. It's also strange they have sorta diffraction spike looking effects, too.

[DaveS]

You could also try Baader Optical Wonder Fluid and microfibre cloth from FLO.

[sheeprug]

Interesting reading this - I hardly ever use any liquids on my glasses.    A wipe with the cleaning cloth supplied with the glasses, or better still the Baasder optical wonder cloth is all I find I need most of the time.  

I do, however, insist on using glass lenses.  Apart from actually breaking - rare - they seem much more robust and more scratch resistant.  I've had resin lenses a few times, and sworn not to have them again because of excessive scratching and they don't seem so clear anyway.   Most glass also has a higher refractive index which helps if you're -10 dioptres like me!

CA used to really annoy me - the red and green LEDs on my old hi-fi amplifier never looked in line, and as somebody else noted, you can move the red and blue parts of Tesco signs around. As a result I wore contact lenses for many years.

However, I take them off for observing.

SR

 

[pipnina]

25 minutes ago, DaveS said:

You could also try Baader Optical Wonder Fluid and microfibre cloth from FLO.

It does seem like I'll have to try it... Every other cleaning method I've used on glasses has made them smeary and it sounds like the baader stuff doesn't cause that from what i've heard.

1 minute ago, sheeprug said:

Interesting reading this - I hardly ever use any liquids on my glasses.    A wipe with the cleaning cloth supplied with the glasses, or better still the Baasder optical wonder cloth is all I find I need most of the time.  

I do, however, insist on using glass lenses.  Apart from actually breaking - rare - they seem much more robust and more scratch resistant.  I've had resin lenses a few times, and sworn not to have them again because of excessive scratching and they don't seem so clear anyway.   Most glass also has a higher refractive index which helps if you're -10 dioptres like me!

CA used to really annoy me - the red and green LEDs on my old hi-fi amplifier never looked in line, and as somebody else noted, you can move the red and blue parts of Tesco signs around. As a result I wore contact lenses for many years.

However, I take them off for observing.

SR

 

Well, maybe the CA isn't as bad in mine as my last pair. That really did have some bad CA but this time it's more of a distortion issue, maybe coma? I'm only -3.25 dioptres but it's astigmatism as well as long sightedness.

I tried contacts once. And decided that it's not worth the amount of frustration they cause. Especially since they didn't properly correct my vision when they were in and made a strange blurry circle at my peripheral vision.

[DaveS]

Another point that occurs to me is that if the cloth you're using has had fabric conditioner during the wash then it will leave smears over the glass.

[Oddsocks]

My optician does not supply a cleaning cloth with new glasses unless you specifically demand one!

She says they cause more scratches and problems than their worth since tiny pieces of grit become embedded in the cloth and then forever after cut scratches in the lenses like a skater on an ice rink.

I have followed her advice for the last twenty years and never sufffer from scratches on my resin reactolite lenses, which was to keep a washing up liquid bottle bottle that is basically empty and just contains a residue of detergent, add half a teaspoon of bleach to remove the colour dye and fill the bottle with water, shake well....

To clean the lenses rinse under a running tap to remove grit, squirt a litle of the weak detergent on each lens and rub lenses and frames between thumb and fingers, rinse under the tap and dry by touching the lenses against a dry clean paper tissue but dont rub, just touch the tissue against the lens to wick up any droplets, oh, and remember to put the plug in the sink before rinsing under the tap if your glasses have clip in nose bridge pads, they have a nasty tendancy to flip out and disappear down the plug-hole if unwary?

After this the lenses are always crystal clear with no smearing or flaring...and no scratches....?

[101nut]

I more or less agree with a couple of the posts ... I have varifocals and plastic lenses and they are not scratched. You should never touch lenses with a cloth of any type when they are dirty. A good cloth is for when they have no residual dirt or grit. The same applies to any optics.

I wash them, lens vertical,in a fairly strong stream of water from the tap which takes the grime off. I smear some washing up liquid (usually Teepol) on my finger and thumb - just enough to 'feel' - dampen it and gently clean the lens between finger and thumb. A good rinse followed by a non-aerated stream (turn aerated taps right down) sheets the water off. It's such a good method that you can pick up any microscopic defects in the coatings with residual water droplets ...

AndyG