My dirty mirrors. How often should I clean them?

[Geoff]

Hi all,
My 10 inch DOB mirror looks pretty good in the day time, but at night when I shine a white torch down the tube it is fairly grotty.
I bought the scope about 5 weeks ago and the mirror looked good.
The viewing still looks good, and if I clean it now it will only get grotty again.
I don't want to clean it very often, and I take the usual precautions when using and storing ie, inside the house, horizontal with cap off untill dry, then cap on until next time.
There has been lots of dew over the last few weeks, and I have fitted a fan yesterday. Dew heaters on the finders and eyepieces were done a week ago and work well.
Cheers
Geoff

[Astroman (Andrew Wall)]

You should only need to clean the primary about once a year if not longer.

You should never shine a torch onto a primary surface it just makes you want to clean them, it shows up every little speck and makes it a whole lot worse than what it really is. It will take a fair amount of dust and grime on the surface to warrant the need of a cleaning, I know of one guy who had never washed his mirror in over 8 years, and it still looked fine. That is also dependant on what atmospheric conditions are around too...smoke etc...

Another South Aussie too hey, WELCOME!!!!

[janoskiss (Steve H)]

Don't bother cleaning it. If you did, it would look the same, if not straight away, very soon after having cleaned it. Newt mirrors always look dirty in a flashlight test. Just keep the ends of the tube covered when in storage. Large showercap works on the mirror end.

[ving (David)]

probably just a bit of dust onthe mirror i am guessing (correct me if i am wrong). I cleaned mine well after the 1 year mark after buying it, maybe closer to 2!
just clean it as it needs it basically but wait for a bit of buildup. under normal conditions 1 year...

[Roger Davis]

Never shine a white light torch down any reflecting telescope!
That is not the way to look for dirt (believe it or not!).
See my answer on the Corrector Plate cleaning in this forum.
Wash it at your own peril! Leave it for another couple of years.

[wavelandscott (Scott)]

As noted...don't check your optics with a torch/flashlight...

Many people have strong opinions on washing/cleaning mirrors...who is right? Don't know and don't really care...

While you should not ever be "afraid" of cleaning, collimating, fidlding with your scope I am of the school of thought that if it ain't broke don't fix it...

A gridiron football quote often wrongly attributed to legendary Ohio St. coach Woody Hayes (actual quote is from General Robert Neyland of the University of Tennesse) I think applies here..."When you throw the ball (refering to a pass in gridiron) 3 things can happen...and 2 of them are bad"...for those of you not "into" gridiron football a pass can be caught by the proper receiver, dropped by the proper receiver or intercepted by the opposing team...hence 2 of 3 are bad)

I tend to think that some people over clean mirrors...yes, I am basically a lazy and slothful person and I am sure that the mirror will just get dirty again anyway so I don't bother...in the mean while, while I have it out cleaning there are many opportunities for me to "mess it up"...scratch, drop, spot etc.

Yes, I am sure there will come a time when cleaning is in order and at that time I will proudly/gladly wash it...but I suspect that it will be a while...

Cheers...

[astro_nutt]

Hi Geoff!!..the amount of dust to settle on a primary mirror over 12 months wouldn't come close to covering the centre ring on the mirror!...so it shouldn't affect image quality!!..so..relax and enjoy viewing for a couple of years before thinking of cleaning!!
Cheers!!

[Geoff]

Thanks guy's for that.
It was what I was hoping to hear.
I won't look down the tube again. unless I can't see anything.
The sky was pretty good last night for this area. (Reynella 25 K Sth of Adelaide) Now the clouds are here.
Probably no viewing for a week or so.
Cheers
Geoff

[Astroman (Andrew Wall)]

damn clouds, who got some new equipment?