Eyepiece Crosshair Cement

[AL1]

I have an Orion 20mm crosshair eyepiece with what looks like fungus on the underside of the crosshair glass.  Does anyone know how to soften the cement to remove the glass and what cement to use to fix it back on after cleaning?  In the attached photo the cement can be seen as the black lines on the edge of the glass.  Excess cement on the metal body scrapped off easily but did not soft when rubbed with isopropanol.  The cross hair glass is only cemented at two points.   I may just leave it be

 

 

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[Louis D]

I looked at my copy of that eyepiece (the 20mm 70 degree, correct?).  There's a small grub/set screw above the illuminator hole.  I wonder if you could loosen it to drop the entire illuminator donut off of the upper barrel so you could access the top side of the reticle for cleaning.

[AL1]

Yes it is the 20mm 70 degree.  The second picture is looking from the bottom of the eyepiece with the aluminum donut that holds the illuminator removed (like you suggest).  It gives good access to the exposed surface of the cross hair glass but the fungus looks to be on the internal side of the glass.  The top picture is looking through the eyepiece,  can anyone confirm that this is what fungus can looks like?

[Don Pensack]

Yes, that's fungus.

[Louis D]

Yes, but did you try loosening the tiny grub screw with a fine screwdriver to see if it releases the donut so you can access the top of the reticle?  It's right above the big illuminator hole.  I don't want to try it with mine since it's working fine.

[Voyager 3]

7 hours ago, AL1 said:

I have an Orion 20mm crosshair eyepiece with what looks like fungus on the underside of the crosshair glass.  Does anyone know how to soften the cement to remove the glass and what cement to use to fix it back on after cleaning?  In the attached photo the cement can be seen as the black lines on the edge of the glass.  Excess cement on the metal body scrapped off easily but did not soft when rubbed with isopropanol.  The cross hair glass is only cemented at two points.   I may just leave it be

 

 

.

The fungus looks cool though!

[AL1]

9 hours ago, Louis D said:

Yes, but did you try loosening the tiny grub screw with a fine screwdriver to see if it releases the donut so you can access the top of the reticle?  It's right above the big illuminator hole.  I don't want to try it with mine since it's working fine.

 

[Stub Mandrel]

Traditionally it would probably be a drop of shellac, that is easily dissolved with meths or loosened with heat.

UV sensitive adhesive is great for jobs like this, although harder to remove. You can reposition to your heart's content then set it in seconds with a little UV LED torch that comes as part of the glue tube.

I've used it for wire cross-hairs.

[Louis D]

8 hours ago, AL1 said:

 

Well, that's unfortunate. 🤔 Nothing else unscrews?

If you can't clean it off, you could at least bake it in the noon sun to try and kill it with UV light to prevent further spread.

[SiriusB]

I don't want to panic you but if you can't clean it, keep it well away from your other optics!

   Seen a lot of fungus on camera optics, but until relatively recently not on astro optics.???

The fungus initially feeds on the lens coating, if it gets a strong foothold it will eventually etch the glass.

It will spread~ i've had camera lenses,stored in fairly dry conditions 'infected' from one bad one.😬

Making sure optics are dry before packing away is helpful in avoiding the issue. I don't think lens caps help in this respect if there's any damp present when you put them on. EP's never used to come with caps,which was slightly better fungus wise.

You could try different solvents until you find one that works. Nothing much will damage the glass, the coatings (presumably there is one on the reticle) may or may not be effected. There's hard & soft lens coatings~ i found lighter fluid very good for cleaning old camera lenses, it did however fetch the basic  magnesium flouride coating off a skywatcher O.G.nicely. Tread carefully!

Canada Balsaam was traditionally used to cement lenses together, relatively straightforward to soften. However I suspect it's not much used now, probably some sort of  optical epoxy??

If you do get it seperated cold cream is one thing recommended for removing the fungus, will be a slow job however.

Good luck.

[AL1]

 I got the cross hairs off by gentling heating the eyepiece which softened the cement sufficiently .   I bought the eyepiece as a bundle with an AVX SCT8 about a year ago and it had the fungus since then, I just did not realize what it was.   Thankfully it has not spread to anything else.  I always leave my cases open for a day after every session to dry so maybe that helped.  Also the optics on the eyepiece in question look to be fine.  It is just the flat glass with the crosshair that has the fungus on the internal surface.  The glass flat looks to me like uncoated glass, maybe that prevented the fungus growth from accelerating.