How To Clean Astrodon Filters

Affiliation

American Association of Variable Star Observers (AAVSO)

Sat, 10/12/2013 - 16:39

I accept AR coated photometric filters and noticed that my V filter is cloudy. Does anyone have any advice on how to make clean filters?

Barbara

cleaning filters

Hi Barbara,

What you describe sounds similar what happens to the colored glass Five filters, where the main Schott glass (BG39) is hygroscopic. If moisture reaches that drinking glass, it can react and cloud, ordinarily from surface crystallization. The clouding is a common problem in humid climates, just is less mutual with those filters that are AR coated. The Five filter is a sandwich of two glasses (BG39 and GG495), so one surface is kept away from air; the AR blanket mostly keeps the other surface away from air. The other common effect are crystals growing inbetween the 2 spectacles; that problem cannot exist solved as usually the glasses are cemented together. If the clouding is on the outside surface of the BG39, you can commonly shine the crystallization off. However, polishing will likely remove the AR blanket.

Since y'all are AR coated, y'all might outset with an alcohol wash to come across if information technology is but junk that can be removed hands. That requires alcohol (or lens cleaning solution) and a cotton swab, with gentle cleaning motions to prevent scratching. If you want to proceed and smoothen, the best method I've found is to use cerium oxide (I have Style more than I need, and can transport you some), and a clean cotton swab, and gently clean the surface until the brume disappears. Washing, followed with an alcohol wash and so as to dry out without streaking, usually completes the procedure.

You can often solve the problem this way. The new interference filters aren't hygroscopic if you do have to replace the filter.

Affiliation

American Clan of Variable Star Observers (AAVSO)

Photometry: Cleaning photometric filters

Barbara,

Unsurprisingly, I fought this aforementioned problem for several years, and you lot're closer to the ocean so information technology is probably even worse in that location. I had some success using the cerium oxide polish approach Arne mentioned merely eventually even determined cleaning had no consequence. After going through three Five filters (getting about 2 years out of each one) I replaced my Schuler filters with Astrodon Photometric filters a year ago and then far they remain clean. These filters don't include the BG-39 glass which react with h2o that Arne mentioned so in that location shouldn't exist an consequence even here in Florida. An added bonus is that the Photometric series has a higher manual, especially the B filter.

Shawn

Affiliation

American Clan of Variable Star Observers (AAVSO)

Thanks Arne and Shawn.

Thank you Arne and Shawn. Someone emailed me privately yesterday and recommended scarlet rouge for polishing from Willmann-Bell so I ordered that. He had the aforementioned problem with his Schuler v filter. On Arne's advice I just took the filter out and tried to clean it with 91% isopropyl alcohol. It didn't brand a deviation so I will wait for the shine. Can I have instructions on how to polish information technology? All of the other filters expect fine it is just the V filter.

Thanks,

Barb

Affiliation

American Clan of Variable Star Observers (AAVSO)

Filter polishing

Hi, Barb

You might want to take Arne upward on his offer of the cerium oxide. Reddish rouge is a slower polish than the cerium oxide. I would suggest starting your polishing with the cerium oxide diluted in mineral oil. Polish against a thick piece of apartment plate drinking glass. Do not press difficult and wear latex gloves. Make clean the filter off every and then ofttimes with isopropyl alcohol and view your progress. When the filter looks skillful optically, switch to the ruddy rouge and do a final polish to remove the micro scratches and amend the transmission of the filter. Shop the filters in a desiccant when they will non exist used for a long period of time. Please let us know this works for you.

Donn Starkey

Affiliation

American Association of Variable Star Observers (AAVSO)

Filter Polishing

Thanks for the instructions Donn. Why smooth confronting a thick piece of plate drinking glass?

Barbara

Affiliation

American Clan of Variable Star Observers (AAVSO)

Cleaning filters

Barbara

If the filters are polished on a piece of thin glass that is flexing, information technology will plough the edge of the filter enough that information technology will cause the filter to act like a lens. This will crusade vignetting on the corners of your prototype. A piece of garden diverseness, double force window glass will work fine if it is used on a rigid surface. I mention using a thick piece of drinking glass because I use a 1/2" thick sheet of drinking glass in my lab for jobs like this. Again, utilize a very gentle pressure on the filter when polishing as increased pressure will also turn the edge slightly; similar to the edge turning problem when grinding a primary mirror.

Donn Starkey

Amalgamation

American Association of Variable Star Observers (AAVSO)

cleaning filters

How-do-you-do Barbara,

I used optical rouge with good results on my hazy Schuler V filter. Eventually, I replaced the B, 5, and Clear with Astro Don interference filters. The Schuler R and I filters are still in the wheel and look good (merely are rarely used).

Question for Arne: I have a five position filter wheel. If I decided to replace R and I would you suggest Sloan filters; if and then, which ones?

Phil

filter suggestions

Hullo Phill,

If you wait at the responses, Sloan g' is roughly equivalent to the combination of Johnson B and Johnson V. Therefore, you can await at information technology in the reverse manner: Johnson B and V give boosted spectral information in comparison to yard', so by keeping B&V in your bicycle, you non merely get color information, but you match with the decades of existing photometry. On the other paw, r' and i' are pretty similar to Cousins Rc and Ic.

If y'all have a v-position wheel and desire to go along a slot for Clear, and then I recommend staying with Johnson B,5 and Cousins Rc,Ic. If you don't listen giving up Clear, then I recommend Johnson B,5 and Sloan g',r',i' - basically the same filters used by APASS.

Arne

Affiliation

American Association of Variable Star Observers (AAVSO)

cleaning filter with rouge

This method worked well for me.

Moisten the tip of your finger (I used distilled water), then selection upward the smallest corporeality of rouge possible by just touching the moist finger to a modest amount of rouge . Smooth the hazy side gently with your fingertip. Remove the rouge with a cotton brawl or Q-tip. I used medical cotton balls.

The extreme periphery of the filter near the cell didn't get completely clear because of the raised border of the cell. A Q-tip might exercise a better task there, but I was worried about possibly dislodging some dirt hiding in the glass-cell junction that might cause a scratch.

Phil

Affiliation

American Association of Variable Star Observers (AAVSO)

Arne,

Tin I have you up on

Arne,

Can I accept you lot upwardly on your offering of a piffling cerium oxide?

cerium oxide

Hi Barbara,

I'll send you a small quantity.

Arne

Affiliation

American Clan of Variable Star Observers (AAVSO)

Cleaning photometric filters

Hello Dr. Barbara!

The Schuller B filter was notorious from getting the "crystalline fog." Later switching to the AstroDon's interference B & V I dont see this problem anymore. Arne is nice for sending y'all some cerium oxide rouge...he probably expects you to make another great "U Sco-like" recovery!

James

Los Angeles, Ca

Amalgamation

American Association of Variable Star Observers (AAVSO)

Cleaning photometric filters

James: I think if this doesn't piece of work I will order the Astrodon filter. That is nice of Arne to send me the Cerium oxide. Tin't look to become my camera and filters back on the telescope. I accept had beautiful skies the past week in central Florida.

Phil: Cheers for the instructions.

Arne: Thanks for the Cerium oxide. I guess yous can get my address from the AAVSO membership database. I would be happy to pay you for the Cerium oxide and shipping or I tin merely add an extra donation when I renew my AAVSO dues!

Barbara

cerium oxide

Hi Barbara,

Don't carp paying us for the cerium oxide - include an actress donation on the next get-around. Cerium oxide usually comes in pound weight increments, and y'all demand about 1/100 ounce for the purpose. That is why I have so much here in the lab. I consider the polishing as a stop-gap measure out. It will extend the life of your filter, sometimes for years, only if your environs is such that the brume occurred in one case, information technology will re-appear.

Arne

Amalgamation

Madrid Astronomical Association M1 (Spain) (AAM)

Astrodon filter

Barbara, I hope polishing would exist fine for your filter. Anyhow, if anytime yous society an astrodon yous will practise a bang-up purchase, it's worth the cost.

My old Schüler filters are still intact, I cross my fingers . Dry weather at my location helps a lot.