216 replies to this topic

[Toddeo]

Try looking through the corrector plate, at the primary mirror.  Does the mirror appear to be brighter/clearer when looking through the cleaned (Zeiss) portion of the corrector or when looking through the still-coated portion of the corrector?

 

If it's brighter through the cleaned (Zeiss) portion of the corrector, then the remaining "coating" (regardless of what it is) is causing more harm than good and performance will be enhanced by cleaning the rest of the corrector plate using the Zeiss product.

 

The colors (brownish and grayish) of the film layers on your corrector plate don't look like those from any low-reflective coatings that I've ever encountered on astronomical telescopes (blueish - purplish - greenish).

 

You mentioned that the cleaned (Zeiss) part of the corrector was more reflective than the still coated part.  That, to me, would be another indication that it wasn't a low-reflection coating that was removed.  Such optical coatings tend to be just as highly reflective as uncoated glass, but only at selective wavelengths (colors).

 

My current "best-guess" is that the coating that was removed was residue from some type of fine smoke or chemical(s) that the scope had been exposed to -- perhaps on two different occasions.

 

What does the reflection of a white light bulb look like (intensity and color) from the cleaned (Zeiss) vs. still coated portions of the corrector plate?

What He says!!!!!!!!!

[andycknight]

To give an example, this is a photo of coating damage on a second hand eyepiece (Tak 12mm Kellner) I purchased...

 

 

The reflected image is off a white ceiling, so it's easy to see the 'blue' colour of the single layer coating, that was removed (probably due to poor/excessive cleaning over the years).

 

Also I remember when just getting into Telescopes... I was given a 60mm front lens element from a camera shop I often purchased stuff from. Unfortunately the lens was filthy and so the shopkeeper cleaned it for me using some acetone and a lens cloth.

 

To our surprise the front coating came clean off in one wipe. You could literally pick up the coating off the cloth as a thin film, that broke into pieces very easily. Never seen that happen before or since. However the lens was very dirty, so maybe be some oil/chemical had reacted with the coating upsetting the bond between them?

 

Regards

 

Andy.

[punk35]

Andy, how does that ep perform in that condition? 

 

To the OP,   If it was mine, I’d just finish cleaning it and use it. At least it won’t drive you nuts to see that discolored splotch anymore. 

 

As Sketcher suggested, my first thought was smoke film. 

[genericnj]

Try looking through the corrector plate, at the primary mirror.  Does the mirror appear to be brighter/clearer when looking through the cleaned (Zeiss) portion of the corrector or when looking through the still-coated portion of the corrector?

 

If it's brighter through the cleaned (Zeiss) portion of the corrector, then the remaining "coating" (regardless of what it is) is causing more harm than good and performance will be enhanced by cleaning the rest of the corrector plate using the Zeiss product.

 

The colors (brownish and grayish) of the film layers on your corrector plate don't look like those from any low-reflective coatings that I've ever encountered on astronomical telescopes (blueish - purplish - greenish).

 

You mentioned that the cleaned (Zeiss) part of the corrector was more reflective than the still coated part.  That, to me, would be another indication that it wasn't a low-reflection coating that was removed.  Such optical coatings tend to be just as highly reflective as uncoated glass, but only at selective wavelengths (colors).

 

My current "best-guess" is that the coating that was removed was residue from some type of fine smoke or chemical(s) that the scope had been exposed to -- perhaps on two different occasions.

 

What does the reflection of a white light bulb look like (intensity and color) from the cleaned (Zeiss) vs. still coated portions of the corrector plate?

These are great pointers thank you! When looking through the corrector plate at the mirror I honestly cannot tell any difference in brightness between the coated and uncoated sides. Reflection of white light bulb through both again appears about the same, except the cleaned part has a bit more whitish haze (very slight difference) and is less warm in terms of color temperature. This coating reminds me of B+W MRC filters for camera lenses -- some of these do not have a tint to them, they just seem to have slightly less reflective grey coating.

 

I hesitate to think it would be residue since it is 100% uniform throughout the still coated portion, also it is impossible to remove with isopropyl alc and soap solution, only the zeiss cleaner seems to affect it -- even when putting quite a bit of pressure with the alcohol solution it has no effect at all..

 

 

 

To give an example, this is a photo of coating damage on a second hand eyepiece (Tak 12mm Kellner) I purchased...

 

 

The reflected image is off a white ceiling, so it's easy to see the 'blue' colour of the single layer coating, that was removed (probably due to poor/excessive cleaning over the years).

 

Also I remember when just getting into Telescopes... I was given a 60mm front lens element from a camera shop I often purchased stuff from. Unfortunately the lens was filthy and so the shopkeeper cleaned it for me using some acetone and a lens cloth.

 

To our surprise the front coating came clean off in one wipe. You could literally pick up the coating off the cloth as a thin film, that broke into pieces very easily. Never seen that happen before or since. However the lens was very dirty, so maybe be some oil/chemical had reacted with the coating upsetting the bond between them?

 

Regards

 

Andy.

The 'blotchy look' you have on the image you posted is actually very similar, except the coating on my corrector plate is more of a muted off white color instead of a prominent blue.

[andycknight]

punk35, on 22 Mar 2019 - 8:29 PM, said:

Andy, how does that ep perform in that condition? 

As far as sharpness is concerned, it makes no difference.

 

However this eyepiece does suffer from noticeable ghosting. I know Kellners are known for this, but I have several that seem to be highly immune to it. In the case of this example some of the coating remains. With a bit of care its just possible to observe a star through the coating. The ghost is then way off to the other side of the FOV, but it did seem dimmer to my eyes.

 

So I ended up getting an Or 12.5mm to replace it.

 

To the OP... In your case I doubt the corrector will cause any noticeable ghost images, if just the outer coating is damaged / not present. (Many of the older SCT's had no coating at all on the corrector plate!) Worst case I think is that the image will loose 4% brightness. (probably nearer 3% since the original coating is never 100% transmission!)

 

[snip...] The 'blotchy look' you have on the image you posted is actually very similar, except the coating on my corrector plate is more of a muted off white color instead of a prominent blue.

 

A muted off white colour, does not seem right for an optical anti-reflection coating. To me that seems like some kind of residue or something. I've seen pink / red / magenta / green / blue and even dark brown coatings... but never "off white". Anybody else seen this colour??

 

Regards

 

Andy.

[genericnj]

Here is another photo from a different angle and showing a larger portion of the zeiss side... 

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[Toddeo]

Clean it! From your picture, the cleaned area gives a brighter image of the inside tube.

[dscarpa]

 I mixed up my cleaning solutions once and used the one for  eyeglasses on the C9.25. I ended up with a film on the corrector that the correct cleaner in this case Lumicon removed. The non Zeiss side looks like age and or smoke related film to me, that brown color is off. I'd clean the whole thing with Zeiss. David

[andycknight]

Hard to tell from the photo, but a small area between 3 and 4 o'clock looks to be the correct blue colour.

 

Regards

 

Andy

[Cpk133]

Try to get a pic with a white light reflection like Andy.  I've used the Zeiss cleaner with no ill effect.  It does a really good job dissolving and removing stubborn dew spots.  Alcohol n dish soap won't touch the stuff that Zeiss dissolves.  If that scope has a good figure, you're going to be happy regardless.

[Boom]

Before you risk destroying the rest of your corrector, do you still have the original microfiber cloth?

Does it look like the coating transfered onto the cloth? It would look like you wiped some ink off something.

I don't believe the theory about the uniform dirt/smoke coating. Your corrector retaining ring and secondary mirror housing would be covered in that film as well.

If you wipe the secondary housing and retaining ring with the same microfiber cloth and lens solution, and don't get the same transfer on the cloth, then you definitely did remove the multi coating. This is a Multi Coated Optics Group scope correct?

Edited by Boom, 22 March 2019 - 05:38 PM.

[genericnj]

Hard to tell from the photo, but a small area between 3 and 4 o'clock looks to be the correct blue colour.

 

Regards

 

Andy

The area between 3 and 4 oclock is the 2nd layer -- when i rub it with the Zeiss it will eventually go to the white at 1 oclock. The coppery layer at 6 PM and left comes off easiest, just one wipe with Zeiss, despite being absolutely impossible to remove with alcohol and soap mix... 

 

 

Try to get a pic with a white light reflection like Andy.  I've used the Zeiss cleaner with no ill effect.  It does a really good job dissolving and removing stubborn dew spots.  Alcohol n dish soap won't touch the stuff that Zeiss dissolves.  If that scope has a good figure, you're going to be happy regardless.

Going to do that now.. 

 

 

 

Before you risk destroying the rest of your corrector, do you still have the original microfiber cloth?

Does it look like the coating transfered onto the cloth? It would look like you wiped some ink off something.

I don't believe the theory about the uniform dirt/smoke coating. Your corrector retaining ring and secondary mirror housing would be covered in that film as well.

If you wipe the secondary housing and retaining ring with the same microfiber cloth and lens solution, and don't get the same transfer on the cloth, then you definitely did remove the multi coating. This is a Multi Coated Optics Group scope correct?

I do have the original cloth I used and i honestly do not see much of anything on it... 

 

I also can't imagine smoke/dirt being so uniform, and the scope was in a case most, if not all, of its life. The primary mirror looks absolutely spotless as is the secondary.

 

I tried wiping the secondary retaining ring with the zeiss cleaner but no residue either.

 

Yes this is the multi coated optics group scope -- has a metal tag saying that at the back.

[rmollise]

I recently purchased a never used MTS-SC8 -- old school 8in SCT with pedestal stand and lx motor drive. It was in all original packaging with manuals and everything included. I paid a good penny for it, but was excited to get an old model in immaculate new condition... There was some dust on the front corrector plate which I wanted to clean just to have the telescope in absolutely new condition and I used Zeiss lens cleaner - which states on the bottle safe for all lens coatings.... Well with one spray of the stuff, as I wiped with the microfiber cloth, it completely removed the lens coating.... now I have half a corrector plate with coating, half partially or completely uncoated. It seemed like there was 2 layers of coating because some parts have still some coating, and some have none ... this is from one spray of the bottle... 

 

I understand I cannot replace the front corrector plate without replacing the mirror as they are matched -- are there any other options to have it recoated? it absolutely kills me that I had a mint telescope that I paid a lot of money for and trying to be diligent I used what I thought was the best lens cleaner and ended up ruining it....

 

Attaching pic. Any advice very welcome

 

Anything strong enough to remove the coating on a corrector would also remove your fingers.

 

Best bet? Check at your local club for someone experienced in cleaning optics, lens type optics. Failing that, get some advice at your local camera store.

[Mirzam]

Looks like brown gunk to me.

 

JimC

[Toddeo]

I looked at the corrector on my 30+ year old Meade sct8 and it almost looks clear to my eyes. I might have to position it" just right"- to maybe see any sign of coatings(I haven't tried that yet), but on a mount/tripod I don't notice any tint of coating. Maybe back in the day- the coatings were very subtle? Whatever the case, the scope gives up great views. The condition of the coatings on the mirror will affect the views much more than the corrector coatings. If your mirror looks great- I would think the scope will be good too.

[dustyc]

Those coatings are pretty tough. 

Maybe buy other bottle of the fluid and try it? See if there is a difference. There is the cosmetic issue to deal with but if the coating looks splotchy then finish the job with the original cleaner and just use the scope. Could be worse, you could have tried cleaning the primary and really had a problem. Early C8 scopes had no coating all if I remember correctly.

[genericnj]

Took a couple pics with a proper camera instead of the phone, note how uniform the coating is -- this is the good side -- i tested one inch spot in first pic and you can see the difference where i wiped with the Zeiss...

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[genericnj]

Here is second pic of the un-zeiss-ed side

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[genericnj]

And here is the photo with light reflecting near the lost coating.

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[gnowellsct]

If the corrector plate is not cleaned properly the coating will not bond to the glass. Also, the cheaper "soft" coatings do not stand up to any type of cleaning. I have seen similar effects in some of their eyepieces.

That's the thing.  You never know with Meade.  I mean, Celestron screws up, but usually it's something mechanical.  GN

[gnowellsct]

those coatings don't look normal at all

[punk35]

How a about a shot further back showing the whole corrector, to give us an overall view? 

[gnowellsct]

the brown stuff is not normal.  here is modern 2015 c8

 

 

here is vintage 2002 c14

 

 

The correcvtor should be clear with just maybe reflection from flash or a light in room

Edited by gnowellsct, 22 March 2019 - 06:44 PM.

[gnowellsct]

The so-called "brown" or good side of your corrector looks filthy by comparison unless it is a horrendously bad shot.

 

Here's a Stellarvue LOMO

 

Edited by gnowellsct, 22 March 2019 - 06:47 PM.

[genericnj]

How a about a shot further back showing the whole corrector, to give us an overall view? 

Certainly! here it is 

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