Are Pentax coatings really this weak?

[markse68]

I’m a bit gutted today after what happened to my Pentax XF12mm yesterday- my first foray into (to me) expensive eyepieces and not very old at all- bought brand new when I still only had my Tal-1 about six months ago.

I went through my eyepieces to give them a clean knowing some would have accidental light finger prints from rummaging around in the dark. Tbh I wasn’t expecting to have to clean the Pentax as the top lens is quite recessed and I don’t use it as often as others. But when I examined it it had collected a fair bit of detritus including what looked like a little bit of sleep dust so I went at it first with canned air then a Nikon wet wipe glasses cleaning cloth (fresh from foil pouch). No pressure was applied other than the springiness of the cloth.

This happened 😳 The little bit of sleep dust had adhered to the lens and when it came away it took a patch if the coating with it!!

Its only small and will likely not affect viewing but I’m a bit depressed about it now- my ocd is kicking in 😞

Apart from my BCO 10mm it’s the newest ep I have and all the others are probably decades old and without this kind of issue. One of the perils of purchasing new things I guess- they can only ever get damaged.

Anyway a cautionary tale of woe and just wondering if Pentax coatings have a reputation for being weak?

What’s that saying- keep your glass clean so you don’t have to clean it!

Edited September 1, 2019 by markse68

[Ruud]

Just some ideas. I'll assume that everything outside the green circles is just lint and dust.

Coatings being hard generally means they are scratch resistant. Instead of scratches you have what looks like two tiny impact craters in the bottom circle. It's hard to make out what's going on with the bigger area in the top circle, but my guess is that it too might be caused by a shock to the surface.

The reflective properties of the inside of the damaged areas look very similar to that of nearby areas, which probably means the coatings are still on the glass. The white edges look like fracture zones, probably from damage to the glass as well as the coating on top of it.

Coatings are thin layers on top of the glass. An impact on the coating is as much an impact on the underlying glass. For coatings to protect against shocks of impacts they'd have to be thick and soft. But to have the optical qualities that the coatings need they have to be very thin, and if they were soft they'd quickly accumulate scratches.

Coatings mostly need to be hard and chemically resistant.  For the rest they are as brittle as the glass underneath. 

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It could well be that you have no damage at all, and that the white discolorations are left overs from the edges of removed contaminations. Maybe you should try cleaning the eye lens again, this time with acetone. (Not nail polish remover - that contains oils as well. I had white spots on a dielectric mirror that disappeared with acetone after Baader's optical wonder and other alcohol based stuff had failed on them.)

 

 

 

Edited September 1, 2019 by Ruud

[markse68]

Thanks Ruud, I tried the lens cleaner (isopropanol), breath , acetone and it’s not going anywhere so I do think it’s damage to the coating- like it just lifted off the glass. It’s very difficult to photograph but that’s what it looks like through a loupe and here I tried to capture it through a 40x inspection microscope but again difficult with phone. It’s not impact damage- the ep has been I thought well cared for and the lens is well recessed. I always keep them capped and in the carry case I made for them and I always leave the caps lifted off and the case lid open a crack overnight after dewy evenings use so they can air. Whatever it was that caused it it only affected this ep. Maybe it was some strange lifeform that took up residence in that cavernous eye socket and feasted on the coating but why only that one? I was using it at the lunar eclipse at a public event and quite a few people looked through it- maybe one of them had something on their lashes that did it 🤔 🤷‍♂️

Edited September 1, 2019 by markse68

[jetstream]

1 hour ago, markse68 said:

What’s that saying- keep your glass clean so you don’t have to clean it!

Sorry to hear this about your eyepiece.

There seems to be a culture of "not cleaning" optics on SGL... I clean my optics regularly and one of the issues with not cleaning them is organic matter and fogging or dew. Mirror coatings are more sensitive in general than eyepiece coatings but over time tree pollen, organic dust etc mixed with water (dew, fogging) will eat coatings.

Not sure if this is your case, but its a possibility.

Edited September 1, 2019 by jetstream

[markse68]

Yes that’s a good point- maybe if I’d cleaned it sooner, whatever it was that caused this wouldn’t have had time to cause it!

[Ruud]

Pretty clear pictures. No fractures there.

Like Gerry I always remove biological materials such as pollen and fingerprints. When enzymes, acids and oils are involved you never know what may happen. Also, a clean surface may give fungi less to grab on to. (I wonder, could dust be the vector for optivore fungi or is it just free floating spores in the air?)

Fortunately you only have a few tiny blemishes. I happen to have a 7-45x stereo microscope myself so I'll inspect my eyepieces for defects as well. They may have similar imperfections in spite of my regular cleaning. I'll try both light from above and below. 

Did you use light from below or above? I originally assumed you'd used a macro lens and light from above.

[markse68]

9 minutes ago, Ruud said:

Did you use light from below or above? I originally assumed you'd used a macro lens and light from above.

Hi Ruud, light from above, adjusting angle to get contrast. First post pic was just a 10x loupe held to back of phone.

PS the coatings on the Nikon scope eps are completely knackered- but it’s still a very useful tool 😉😂

Edited September 1, 2019 by markse68

[markse68]

1 hour ago, jetstream said:

There seems to be a culture of "not cleaning" optics on SGL.

The worst I read was on a blog- can’t remember whose but they said words to the effect of you should never clean your eyepieces and if you do you may as well chuck them in the bin and buy new ones as they’ll never be the same again. Little bit extreme 😂

[John]

I clean my eyepiece lenses reasonably often using the Baader Wonder Fluid and their micro fibre cloth AFTER blowing off all loose debris with a manual hurricane blower.

I've never seen damage like that to coatings before to be honest. I've owned and cleaned dozens of eyepieces including the Pentax XFs and XW's. The coatings on the Pentax eyepieces have always seemed immaculately applied and robust, at least for the cleaning method that I use. If there is a company who know about coating optical lenses, it's Pentax from my experience with their photographic products as well as their astronomical ones.

If I had to guess I'd say that the marks photographed do look like small impact marks but I'd have to see the eyepiece itself to be sure.

 

[jetstream]

32 minutes ago, markse68 said:

The worst I read was on a blog- can’t remember whose but they said words to the effect of you should never clean your eyepieces and if you do you may as well chuck them in the bin and buy new ones as they’ll never be the same again. Little bit extreme 😂

My dob maker worked in the coatings industry years ago and the info he passed on was valuable to me. My 15" has a very small spot of coating deterioration, all my fault. It started to condense in the mornings in my garage and with dust/pollen/bug stuff on it etc. I was warned... Now I have a new, better storage place with a small light bulb to help and less humidity in there.

Its not only fungus that eats coating its the reaction of organics with water on the optics too. The good new is your eyepiece should work fine as does my 15"