View Single Post
  #5  
Old 04-02-2018, 10:17 PM
Wavytone
Registered User

Wavytone is offline
 
Join Date: Jul 2008
Location: Killara, Sydney
Posts: 4,147
Well, after 45 years of observing - and I’m also one with specs...

1. The last of your comments is half right, half wrong. It’s certainly true that the less you handle eyepieces - especially unnecessary handling - the longer they will last you. But it’s also not true that the coatings are easily damaged - quite the contrary. Modern coating technology using zinc cryolite and SiO2 produce films harder than crown glass. These are coatings that are typically pale yellow through green. I wear coated spectacles that are cleaned every day and after 2-3 years (my normal replacement cycle) the coatings are intact after 300-400 cleaning cycles usually with hot water and detergent followed by wiping dry with a tissue or clean cotton (t-shirts work well).

The coatings that ARE easily damaged were the old MgF ones - they appear deep purple and are commonly used on some SCT corrector plates. These must be treated with great care as they’re soft (easily scratched) and lengthy exposure to moisture (dew) ultimately leads to the coating coming off in patches. Well-intended but excessive cleaning will do same. MgF is rarely used on eyepieces these days.

2. The next issue is dismantling eyepieces. In short, don’t because they’ll never be as good again afterwards.

3. Cleaning:

- use a blower or soft brush to remove any loose dust.

- use a solvent that will shift grease - rubbing alcohol or acetone, even Windex is good.

- use the solvent sparingly - ie do not flood the lens because you don’t want it to flow inside where you can’t get it out. If that happens the eyepiece will fog internally at night.

- by all means use a Q-tip, cotton buds to clean grease off. A well-washed linen hanky is arguably the best to mop up and dry the lens afterwards, so are Kleenex tissues or the small pads women use to remove eye makeup.

Another way to clean small lenses is to apply some neat dishwashing detergent then pour boiling water over to wash off.

Lastly you can use turps or kerosene to shift gunk but it’s smelly and you’ll have to clean with detergent and water afterwards.
Reply With Quote