American Association of Variable Star Observers (AAVSO)
Tue, 07/28/2020 - 20:49

I'm looking for a step up from the "squeeze bulb" to blow dust off of my optics.  The products I have found so far are compressed aerosols.  Does anyone have experience with these?  Are there any residues?  There does not appear to be dry nitrogen or dry air available in a consumer pakage.  Of course, a high-pressure CO2 spray would be best, but I doubt I will fnd that in a spray can!


American Association of Variable Star Observers (AAVSO)

Hi Tom

I'll limit my suggestions here to dust.

Bulbs work, but they suck up dust when they inflate. Then you just blow all that dust on your optics. You always get a dozen more specs of dust ON the lens when trying to blow off the very last spec OFF the lens. Everybody has a bulb with a brush on it. I hid all ours so the grad students couldn't find them.  I have a battery powered keyboard vacuum but the brush is a bit stiff. I might experiment with that on cheap optics. But it will need a thorough cleaning before being used for optics. And, of course, one has to understand where the exhaust is blowing.

Aerosols or cans of air are great for the heat sink on your microprocessor, but they all seem to leave residue on optics. In fact, you can see the liquid propellant  spraying with the air.  

Then there are clean rooms. It is not that expensive or difficult to set up a mini-clean-room on a desk. Maybe $300 or so.

A wash with 99.9% IPA works, and 91% IPA might even take the 9% water with it when it evaporates.

Nitrogen from liquid nitrogen is the best nitrogen. The water has frozen out. Otherwise, bottled nitrogen at 2200 psi is commonly available. Again the 99% stuff is dryer. But then you should have a micron filter after the gas regulator. People that use this type of setup will keep the good clean regulator, airline, and spray nozzel together once they have it clear of dust. The nice thing about N2 gas over CO2 or other gasses  is that if the bottle leaks out in the garage, it likely won't suffocate you. Air is 78% N2.

Practically, for every day dust, I use a soft brush at home, or just ignore it. I like flats.

Much of dust accumulation can be avoided. Turns out that gravity makes dust fall straight down. So parking your scope horizontally will greatly reduce the dust load. An elastic bowl cover over the open optic has been shown to reduce blown dust accumulation.


American Association of Variable Star Observers (AAVSO)
Cleaning optics redux

If the optics' surface is not oily, etc, then squeeze bulbs remove most dust big enough to see with a flashlight. I've used a brand called Hurricane ever since my photo darkroom days. If you're in a very dry environment, only make 2-4 strategic squeezes, or you'll simply build up static electricity and not get anywhere. A powerful flashlight or floodlight to examine progress is your best friend here. I've tried to clean optics in the dark, but I've been simply appalled by the results.

Never use canned air etc around optics. Sorry to say--it's just filthy.

Regarding brushes: the very very soft, very fine-bristle painters' brushes work extremely well. I use a thin fan-style with ca. 1.5 cm bristles. You can get them at artist supply stores or even, I think, at Michael's. It's the only thing I ever allow to touch my filter surfaces, other than the original packaging. A light brushing and a single puff of the Hurricane is almost always good enough. Then get your system closed as fast as possible.

In the end, I don't worry about dust the way I did in the darkroom. I worry most about the surfaces closest to the sensor, and then trust flats to compensate for the rest.

Beyond dust, fingerprints are always difficult. I wear blue nitrile gloves whenever there's a risk of touching anything directly, for example when changing filters in my filter wheel. In an emergency I use a Nikon lens pen. But prevention is best.

My optics cleaning items including gloves and magnifier stay in a separate sealed box when not immediately in use. I'm a fan of Container Store men's shoe boxes for this; eyepiece cases work well, too.

Good luck.