Coma Corrector Cleaning

[AstroGeorge84]

So I just purchased a coma corrector second hand for my skywatcher 250pds. 
just checked it and the lens is pretty grubby… what would be the best way to clean this? Or is better getting it sent to a professional?

thanks in advance

George 

[ONIKKINEN]

First blow all the dust and particulates off with a hand bulb so that you dont run this in later and scratch the lens. You could also use a lens brush at this point to lightly try and remove bigger particulates that the air blower did not remove. (lens cleaning kits can have everything you need)  Then clean with some kind of lens cleaning fluid or diluted isopropyl alcohol with some kind of sealed and very clean cloth. Could be cotton swabs/pads or lens cleaning cloths sold in camera stores, just make sure it has no grit that could scratch the lens.

Apply only a small amount of the fluid. If you use too much the fluid can get past the lens and get inside the CC, which will be impossible to remove and leave some residues. If in doubt, use less pressure and less fluid and never rub with force. You can always repeat the cleaning but cant clean away a scratch. Finally wipe with a clean microfiber cloth.

In short: Dont scratch it and dont douse the lens in fluid

[AstroGeorge84]

Thanks for the reply, that all sounds good and easy enough to do. Will get a dedicated lens cleaning kit. 

[Louis D]

3 hours ago, ONIKKINEN said:

Apply only a small amount of the fluid.

To the cleaning cloth.  This was seemingly left out.  Never put cleaning fluid directly on a lens, ever, at least while they're still in their lens cell.

Windex or other ammonia/detergent based glass cleaners work very well in my experience to get stuck-on grime off.  Just don't scrub.  Unseen micro-grit can scratch the lens coatings.  Instead, leave a damp cleaning cloth on the lens for a bit of time if needed to loosen grime, then lightly wipe again.

You can finish up with dedicated lens cleaning solutions.

If the lenses are still grubby, you could get a lens wrench/spanner and remove the retaining ring holding it in the lens cell.  Next, put a small dowel or similar up into the cell to support the lenses.  Finally, lift off the lens cell and clasp the lenses.  Set the lenses down carefully on a folded towel and note their orientation.  You could even mark the edges with a dark permanent marker showing alignment and which way is up along with the stacking order.  Now you can put a folded towel in a plastic tub in the kitchen sink and fill it with soapy dish detergent water.  Let the lenses soak for a bit and then repeat the cleaning steps, except using running water and your soapy finger tips to immediately flush away any unseen grit that works loose.  I've salvaged some pretty grimy lenses this way.

Again, finish with lens cleaning solution if you see any remaining streaks or water spots when viewing reflections from a bright light at an angle to the lens.

[AstroGeorge84]

That’s fantastic Louis thankyou so much.