Celestron Astromaster.

[Sheffield Col]

Just picked up a Celestron Astromaster 114 very cheap, but It needs a repair.  The Aluminium bit where the screws go through to pinch on the Dovetail was broken. Well I got it rewelded and it's ok now but the scope looks like it's been is a filthy shed for some time it was full of spiders and web's and the primary mirror and secondary mirror was covered in dust and fly Sh*t. Well I have got the mirrors out to clean them but cant seem to get hold of any Distilled Water to rinse them with, can I use De-ionised water instead ? Thank You. 

[AstroMuni]

Yes, you should be able to use de-ionised water. Its purified water - just uses a different process to distillation.

[NGC 1502]

Not everyone will agree to this, but it’s worked for me over many years without a problem.

Use tepid water and regular washing up liquid- more than just a few drops. Buy good quality cotton makeup cleaning pads from Boots or similar.  Gently wipe underwater, use each pad just once.  Rinse with distilled/de-ionised water. Examine. Not clean?  Try again, gently, then rinse.  Stand mirror on edge, dry with a hairdryer on a not very warm setting. If necessary use a corner of good quality kitchen towel for larger drops of water, dab, don’t wipe.

If it’s better but not perfect, quit while you’re ahead. Doesn’t have to be pristine to work very well indeed. A few drying streaks are no problem.

As I said, never had a problem, neither has a clubmate who’s made mirrors for others and has an optical workshop, definitely knows his stuff.

If anyone disagrees, all fine, I don’t bite😊

Ed.

 

Edited July 25, 2023 by NGC 1502
Added info

[bosun21]

With your mirror being badly soiled I would definitely use the finger method on the mirror while it’s submerged in the soapy water. That way you will be able to feel any large pieces of debris attached to the mirror surface. Once happy that you have dealt with any pieces stuck to the mirror then change to the cotton balls. You can’t feel these with the cotton balls and it’s very easy to drag them across the mirror scratching the coatings.

[AstroMuni]

Heres a helpful post from FLO https://www.firstlightoptics.com/blog/cleaning-a-newtonian-mirror.html

[Sheffield Col]

Many thanks for all the reply's, they are very helpful.  

[Sheffield Col]

A bit more on the Astromaster 114, I have had the focuser out to clean it but have run into a snag, it seems there is a lens in the focus tube that act's as a Barlow I took it out because it was filthy same as the rest of the scope, but cannot remember which way up it is suppose to go. So I am just hoping someone can tell me, also I got to thinking "Is it really necessary to have this "Barlow" in the focus tube.   

 

[Cornelius Varley]

45 minutes ago, Sheffield Col said:

So I am just hoping someone can tell me, also I got to thinking "Is it really necessary to have this "Barlow" in the focus tube.   

 

The "barlow" lens is part of the optical system. The Astromaster 114 has a optical system known as a Jones-Bird reflector. The corrector lens adjusts the focal length and also corrects spherical aberrations.

[Peter Drew]

If the corrector lens is plano-concave I would expect the plano side to face the diagonal.       😀