I searched the forum on some info regarding collimating and mirror cleaning but couldnt find anything. My mirror needs cleaning and collimating, ive seen some youtube vids of people cleaning their mirror with dish washing liquid and their hands however does this not scratch the mirror? Could someone please point me in the right direction.
He is touching the surface of the mirror with his hands, does this not scratch the surface?
No there is some trepidation involved in this no doubt (I had some myself the first time) but I have cleaned both my 10" and 12" mirror surfaces in the past using warm water and a biodegradable dish liquid with cotton balls / my hands followed by a good rinse. My mirror comes up very clean and, most importantly, undamaged. I rinse the mirror with distilled water to finish and touch dry the spots with a very soft cloth. They're not as fragile as some would have you believe. No probs at all.
I just looked at the collimation site from Alan(above). If it is correct I have spent hour after hour after hour trying to achieve the perfect concentric collimation with my f4.5 12" DOB only to discover that some 'offset' is quite normal in fast Newtonians. If this is correct I will sleep a lot more easily tonight!
Thank you Alan
I just looked at the collimation site from Alan(above). If it is correct I have spent hour after hour after hour trying to achieve the perfect concentric collimation with my f4.5 12" DOB only to discover that some 'offset' is quite normal in fast Newtonians. If this is correct I will sleep a lot more easily tonight!
Thank you Alan
Stew
I didn't find out immediately either, but luckily just after a couple of days. Being a perfectionist, I was starting to lose my sleep too. It was a relief to find out!
About cleaning, I use the same liquid I use to clean camera lenses and it works well. I still have the one they sent me with my camera, but you can buy it at OfficeWorks for little money I think.
For making the mirror cleaning liquid at home, use the pump spray and mix equal parts of water,preferably distilled, and methylated spirits, and spray on the targeted mirror.
If you must use a detergent the safest is a good quality "NON WAX car wash detergent. Car wash detergents are Caustic soda & Acid free, after all who wants a rusty car!!
Last time I cleaned my 14.5" mirror I read everything I could find about the process. One thing I read was NOT to use cotton balls, but to use surgical cotton that comes rolled up in layered paper, because apparently cotton balls may have extra particles in them from the manufacturing process.
That done, I still got some very fine scratch marks on the mirror.
I wish I'd taken the advice of a guy at my club who said he just cleaned the mirror by taking it out and aiming a hose at it, and turning on the tap - then rinsed with distilled water.
My advice, only wash the mirror when it is really, really dirty.
Regards,
Renato
Are you sure those are scratches, not scuffs or smears?
I almost always rub my mirror when cleaning it (after the initial rinse and soak of course), to get rid of stubborn stuff. I rub with isopropanol and kitchen paper or my fingers, and have never caused the slightest scratch or swirl. That is not surprising either, since the coating of the mirror is silicon dioxide (essentially quartz). That stuff is hard and doesn't scratch easily.
All this talk about cleaning and collimating made me pull apart my Dob for some TLC, incl. mirror wash. It is like new again I also fixed a flaw inherent in Bob's Knobs (on the secondary) that has bugged me for ages, and rounded the tips of the screws...
If you must use a detergent the safest is a good quality "NON WAX car wash detergent. Car wash detergents are Caustic soda & Acid free, after all who wants a rusty car!!
Sorry to be pedantic, but caustic soda is not aggressive to steel, it actually protects steel from corrosion.
(It will chew up just about everything else, though, including paint, aluminium - including aluminised mirror coatings - fats and grease, etc, so yes, many good reasons to avoid caustic soda, but rust ain't one of them.)
Sorry to be pedantic, but caustic soda is not aggressive to steel, it actually protects steel from corrosion.
(It will chew up just about everything else, though, including paint, aluminium - including aluminised mirror coatings - fats and grease, etc, so yes, many good reasons to avoid caustic soda, but rust ain't one of them.)
Who's talking about steel, I'm concerned about the sensitive mirror coating..Re-read Posts 1 & 8 then 12. You have jumped the gun here!
Whilst we are on the subject of collimation, could i have some opinions as to whether mine is in good shape?
Its a 10" F4.7, and the picture was taken with my phone up against an old film holder with a hole in the centre.
The focuser was all the way out, as per the instructions on one of the above links, but i cant see any mirror clips until i move the focuser inwards. They look Ok when i do, but i wondered whether i need to move my secondary mirror to see the clips when the focuser is all the way out.
Any advice you could give would be appreciated
Cheers
Who's talking about steel, I'm concerned about the sensitive mirror coating.
The post that I responded to:
"who wants a rusty car"
Caustic soda actually PROTECTS exposed steel from rust, so it won't make your car rust, but it is EXTREMELY aggressive to aluminium, and it might damage the paintwork and plastics - and it could well be damaging to at least SOME (but by no means all) optical coatings and mirrors.
Yes, I would definitely avoid using caustic soda products in cleaning any sensitive equipment.
Stew
I also fixed a flaw inherent in Bob's Knobs (on the secondary) that has bugged me for ages, and rounded the tips of the screws...
