Glue a doublet lens back together

[mdstuart]

Good afternoon

I bought some Swift 20 x 80 bins online to try to fix up. Challenge one was fungus. So off with the objective...Oh the fungus is between the doublet lens.

After some googling and gentle boiling I have both lenses apart and clean. I did mark the alignment but my cleaning was too good so the marks gone...oh well hey ho..

So can I just rest them back together or do I have to glue them back together again?

I do not want to have to buy posh glue and a UV light ....so can I just use UHU glass glue or is there something else better?. I am mindful that at some future date some poor amateur like me might want to split them again

Thank you in advance.

BEFORE

AFTER

 

 

 

[Peter Drew]

I had the same issue with a WW2 German 80mm binocular and dealt with it in the same way. Rather than "glue" the lenses back together I airspaced them with 3 tabs of aluminium foil, if you place them together without it could scuff the surfaces. They work well again.  

[mdstuart]

That makes sense and it is cheap and easy..and I cannot get it too wrong

Mark

[Alien 13]

I have done similar to Peter with a camera lens, I made up a foil ring to air-space the elements.

Alan

[Doc]

I've done the aluminium foil trick as well with some old Russian bins I had lying around and mine worked as well.

[Peter Drew]

Just make sure that the lens components are the right way round.   

[mdstuart]

Thanks guys I will make some spacers.

Mark

[Ben the Ignorant]

Do not use regular glue! It's much too strong and will distort the lenses, causing astigmatism. Cemented lenses are held together by natural resin (Canada balsam), that's why you could separate them with warm water. If you can't source Canada balsam or if the expense is not justified for just one doublet, use the alu foil trick.

[chiltonstar]

I have done it in the past with canada balsam bought from a microscopy supplier.

When I de-mounted my 102mm achromat last year (air-spaced) I remounted that with Al foil tabs, but that is an air-spaced lens of course, unlike the binocular achromats..

Chris

[mdstuart]

Thanks for all your thoughts... So I actually, for now, put three slithers of scotch tape to air space each objective. They give great views in the daytime. Star test to follow.

Collimation needs a slight horizontal tweek so that is the next job..

I might buy some Canada balsam substitute which I can get for £5 but maybe not as the scotch tape makes the bins unique

Mark

[mdstuart]

Collimation now fine.

Sharp central view.

[Ruud]

Looks good, especially if you consider that the depth of field is shallow.

Kudos!

[mdstuart]

Star test all good with sharp stars. Split Dziban easily in Draco. Well pleased!

Mark

[Peter Drew]

Great result!