Refractor primary lens damage.

[hawksquawks]

Hello all a couple of days ago my secondhand telescope arrived paid £125 for it posted it's a skywatcher D=120mm F=1000mm It came with an EQ 3-2 mount also. it did not have it's due shield or cap and was left in the loft for some time as stated by the seller, so i expected some degree of dirt or damage.  I tried cleaning it and i feel I have made it even worse than it was. I was cleaning with a 50/50 mixture of distilled water and isopropyl alcohol with one drop of dish soap. anyway while cleaning I accidentally split the solution over the optics and it's now between the lenses and the lens has fogged up really bad, there are also spots of different color tones in the coatings also. suggestions ? Ideally i don't want to split the lenses as I am very OTT about getting dust between them. I am considering getting them professionally repaired and re coated if this is possible?  PICs below      

Edited April 18, 2020 by hawksquawks

[NGC 1502]

Sorry to hear of your mishap.

I think what I’d do is to let the scope thoroughly dry out in a dust free dry place out of direct sun.   Leave the scope uncapped at both ends.  In a couple of days take a look, remembering that when viewed with a bright light most optical surfaces look less than pristine and still work fine.

After that, if you’re still not happy with how the lens looks, I’d try another careful clean.  I’d avoid removing the optical elements from the lens cell, it’s much more complicated than it sounds to successfully reassemble correctly.  However it’s usually quite simple to unscrew the whole lens cell from the tube as a complete unit. This would allow cleaning of the innermost lens surface.   You could put a piece of tape on the cell and an adjacent piece on the tube so you can refit in exactly the same position.   Go carefully when refitting because the threads are fine and it’s easy to cross thread, but if you’re careful you should be ok.

I’d consider getting something like ‘Baader Wonder Fluid’ a top quality cleaner for lenses.

Hope you sort it to your satisfaction, Ed.

Edit - just checked - Baader wonder fluid is available from FLO for £11.

 

Edited April 18, 2020 by NGC 1502
Extra info

[Star101]

Sorry to hear of your dilemma.

As NGC 1502 says, Its OK to separate the scope to get inside but don't take the lens apart. I tried this with one of my eyepieces...I mean, how difficult can it be!! Needless to say, the eyepiece was ruined. It was only three elements, It just never went back as snug as before. And I do know how to take stuff apart an refit...Just somethings should be left to the experts with the proper tools and environment.

Good luck with trying NGC 1502 suggestion. Let us know the outcome!

 

 

[DaveL59]

I'd be inclined to remove the lens cell as suggested, then place it in a plastic box securely on its side perhaps, with dry uncooked rice or lots of silica gel and seal it for a few days. That should draw the moisture out and hopefully not leave any streaks. Obviously protect the lens elements so they don't get scratched tho. Then go back over the inner and outer with lens cleaner and hopefully you're sorted. Variations in the coating are unlikely to affect the view so I'd not worry about that, they can discolour in patches depending on what's been in contact with them too.

Good luck with recovering it, shouldn't be too hard so long as the surfaces aren't scratched  

[NGC 1502]

4 hours ago, DaveL59 said:

I'd be inclined to remove the lens cell as suggested, then place it in a plastic box securely on its side perhaps, with dry uncooked rice or lots of silica gel and seal it for a few days. That should draw the moisture out and hopefully not leave any streaks. Obviously protect the lens elements so they don't get scratched tho. Then go back over the inner and outer with lens cleaner and hopefully you're sorted. Variations in the coating are unlikely to affect the view so I'd not worry about that, they can discolour in patches depending on what's been in contact with them too.

Good luck with recovering it, shouldn't be too hard so long as the surfaces aren't scratched  

Great suggestion 👍

[Carbon Brush]

Sorry to hear of your lens issues. Cleaning accessible faces and drying, as recommended by earlier posts is probably going to be all you need to do.

If you do end up having to split the lens, it is not necessarily a show stopper.
I don't know the details of the lens cell in this scope. But looking at the new price, I think it will be a simple construction.
I have dismantled simple cells on a couple of old refractors. One for dust left by a previous dismantler, the other to get some fungus.
In both cases I took basic precautions and there was a good outcome.

Good luck and let us know how you get on.

David.

 

[hawksquawks]

Thanks for the advice I will remove the cell could I dry it out with a hair dryer or heater fan? it's not going to be sunny for awhile And i would like to get this sorted before the next clear night.  

[hawksquawks]

Sorry for double posting some further images showing a better extent of the problem so aside from being misted up badly between cells, the water has now cleared from the cell but has left marks inside around the edge of the optics worst affected area shown in the red box, what impact with these marks have on image quality? I am trying to gauge whether or not to split the cells at this point, if it does not affect the image it won't be worth the risk.  unless when the misting goes it revels any more nasty surprises  😐

 

EDIT update I have propped the lens in front on a fan blowing cool air into the back of the lens, appears to be clearing Ill leave it until I wake up ill update at that time. 

 

Edited April 19, 2020 by hawksquawks

[hawksquawks]

Final update, so after leaving it with the fan blowing air over night it's cleared up very well, there are still streaks around the edge of the lens left by the water ingress that cannot be removed without splitting the lens, I am going to assume these marks will not affect image quality ? beyond that i feel crisis averted.  

[banjaxed]

That looks like you have done a good job 👍 

[hawksquawks]

It's tuned out better than I expected still unsure about the edges tho, that said thanks for all the input and suggestions everyone. 

[Louis D]

You can always create an aperture mask to mask off the edge to see if there is any change in the view.