What is the best way to clean a filter that has a few spots on it?

[g__day]

In changing over cameras last night I noticed that a IDAS light suppression filter has some gunk on it. Most I used a puffer to blow off - but some grime still appears during long duration shots. What is the best way to clean a filter?

Many thanks, Matt

[glend]

I use Bintel UHC cleaning fluid for all multicoated glass cleaning: filters, objectves, even stubborn mirror spots that may not be distilled water soluble (like gum tree sap droplets).I use pure acetone to clean camera sensors.

[TR]

Matt,

This is where you would use your flats in your processing work flow. Perfect for this sort of thing.

Terry

[g__day]

Flat haven't zapped this yet, in fact in using Deep Sky Stacker (for years now) something very weird is going on with with my processing.

I created the BIAS, flat whites, flat darks and darks several days ago and made masters, but when I stack good light frames everything becomes really faded. The histogram is all the way to the left and on say the Triffid - only the stars can be seen, even the nebulae is lost!

Will try again and see if its the flats or the darks (or something else) that is removing all the nebulae detail!

PS

It's definitely the darks that loose all the detail! I stacked four shots of M20 - 480 secs, 600 secs, 900 secs and 1200 secs - all fine. Added BIAS - all fine. Added Flat White - better still. Added Flat dark - improved. Added single 480 Sec master dark - all went to hell - light curves shifted to the far left and blue got ultra wide. Tried again and used just a singe 480 sec dark CR2 (raw) file - still very wonky and violet shifted.

[g__day]

Success on the processing side - turns out with a cool box cooled Canon DSLR stacking dark frames using median kappa algorithm is a bad idea - whereas median looks great!

So back to the cleaning question (and apologies for the distraction). I have Bintel cleaning fluid but no instructions.

Do you put it on straight or dilute it with distilled water?

Do you rub spots gently or not (and if so with what surface)?

Do you wipe it clean with a dry cloth of some sort or a very low set hair dryer - to best prevent streaking?

More information on the cleaning processes itself would be greatly appreciated!

[glend]

Use a little dab of fluid on a 'clean' microfibre cloth ( the lense cleaning ones),