Help - Fungus on objective

[Martin D]

I've dug up an old Skywatcher 120 mm refractor and it's in good nick...except it has some fungus in the lens doublet!  I've exposed it to UV to kill it but anyone have any ideas about safely removing it...or should I just bin it?

Thanks!

[Carbon Brush]

Fungus has to be quite bad to warrant the bin. Post a photo? Is the fungus outside, inside the tube, or between the doublet lens elements?

A bottle of Baader Wonder Fluid and a good lens cloth (available from FLO and other good astro retailers) are your cleaning tools.

The process is not difficult and with a better feel for the extent of the problem, the exact scope model and which surfaces need attention, members will be able to help you.

By the way. Welcome to the best astronomy forum in the world!.

David.

 

 

[fozzybear]

http://darkerview.com/wordpress/?p=18369

Have a look at above site maybe of some use in solving your problem in a brief note to rid the rogue bug by the way you have to clean all the scope as the spores are not just on the optic cell. Clean all 50/50 mix of hydrogen peroxide (H2O2) and ammonia (NH3). 10ml should do it.

Andy

Edited November 10, 2019 by fozzybear

[Ben the Ignorant]

1 hour ago, Martin D said:

it has some fungus in the lens doublet!  I've exposed it to UV to kill it but anyone have any ideas about safely removing it...or should I just bin it?

I've done that job with success so this might help:

But by all means, NEVER dump a telescope, give it to someone who is willing to try to salvage it.

Welcome, by the way, and happy cleaning chore! 😁

[david_taurus83]

1 hour ago, Ben the Ignorant said:

I've done that job with success so this might help:

But by all means, NEVER dump a telescope, give it to someone who is willing to try to salvage it.

Welcome, by the way, and happy cleaning chore! 😁

^^^What a great thread! 👍

[Martin D]

Many thanks for the advice...I'll crack on with it.

[Alan64]

Be certain to note the order of the doublet...

The crown lens is convex on both sides.  The side with the steeper curve faces the concave surface of the flint.

[wookie1965]

Brilliant I was thinking of cleaning my Meade this is exactly what I needed.

When I first got it the crown was the wrong way round I did not know this but Peter Drew did as soon as he looked through it, I knew there was something wrong obviously just not what.

Well there is quite a bit of dust and finger marks on the lens I was going to clean them but never had the confidence now with this explanation it's a job I can tackle.

[Alan64]

With longer-focus doublets, it can be difficult to tell which convex side is steeper.  All one has to do is to install the crown, take it out to test, then flip the crown and test again.  The correct side will make itself known, even that of an f/15, I've found.  However, the correct side of an f/8.3 should be a good bit easier to identify, and to where there would be no need to flip the crown; an f6 or f/5 being most easily determined.

[Physopto]

They may be cemented together, be careful.