8 replies to this topic

[Jon Rista]

I've been looking for a resource on cleaning the primary mirror of an 8" GSO type RC. I thought there was a thread in here on that topic a while back, maybe almost a year ago now, but I am having trouble finding it. Anyway, ever since I got this scope, there has been something on the mirror. I decided to follow Henry's "Reset" collimation method to see if I can fix a softness in my stars, and in doing that I figured I'd finally clean the mirror, as whatever is on it seems to diffuse fair amount of light. Whatever it is, it's stuck on pretty good as I've tried to blow it off, and even very lightly swiped it with a clean new microfiber cloth and nothing budges. I don't know if it is sap or something else, whatever it is, it is pretty evenly distributed across the mirror. The goop will stick to other particulates as well, as there are some fibers on there that also won't just blow off:

 

 

 

 

I am curious what I should be using to remove this stuff. Thanks!

[Arthur Dent]

Hi Jon

 

Regarding cleaning the primary mirror - don't unless you absolutely have to.  Looking at the pictures and the fact that you say that the paticles/fluff seems to be stuck on, you could try folowing the advice here http://www.arksky.org/asoclean.htm

 

Whatever you do, make sure that you do it with the lightest of touches - no rubbing - and always work radially.

 

Good luck and keep us posted!

 

Hope this helps,

 

Art

[rainycityastro]

Jon, the coating used by the AT8RC is extremely sturdy.

Use this technique without hesitation. https://www.youtube....h?v=JMH0WQETxKw.

Here is how it looked afterwards. Unfortunately I didnt photograph it before. It was worse than yours.

 

My mirror went from extremely grungy to looking brand spanking new in about 5 minutes. Zero sleeks, scratches etc and I am very particular.

[Jon Rista]

Thanks, guys. I am hoping for a less caustic approach. I did find the video that I believe was linked in the original thread I was looking for:

 

https://www.youtube....h?v=8rZP7mTEutE

 

I've started with this, and it seems to have helped a bit so far. I thought I had some isopropyl alcohol, and it turns out I do not, so I'm heading to the store. Still, just a bit of warm water and soap helped clean off a lot of the white particulate, and now it's just little droplets of sticky residue that I'm hoping the alcohol will clean up. I'll keep you posted. If that does not work, I may have to resort to more extreme measures. 

[Jon Rista]

All clean:

 

 

 

[rflinn68]

I'm a little late to the party, but the thread you're looking for was probably from Anis. I have a post here at LPO that includes a link to his thread.

[Jon Rista]

That was indeed the thread, thanks Richard. 

 

I did a quick collimation with a cheshire and the hall of mirrors technique. Things look pretty good at the moment, at least mechanically. Hoping they look a as good tonight once some stars come out. Looks like after tonight it's going to be cloudy for the foreseeable future, again. :\ Haven't done any astrophotography since the first week of January. Those Moravian 16200 cameras cannot come out fast enough...I REALLY need to get a CCD and some narrow band filters so I can image while the moon is up. (Although it's going to cost me a fortune for filters...they have a 7-pos FW, takes 50mm filters, to get a full set of LRGB and Ha 5nm, OIII 3nm, SII 3nm will cost me $3665, which is almost as much as the camera and FW itself. O_o). 

[Hawkdl2]

Jon,  perfect timing. I was just about to research this to clean my AT6RC.  Was it the IPA that removed the sticky spots and did they come off easily?

[Jon Rista]

I have been inspecting the mirror. I used the cotton ball approach, I basically just sloshed them around over the mirror, then pored down the level of the soapy water and redid that with the alcohol solution. The mirror is dry, and I was reassembling, and I noticed two very fine scratches in one area on the mirror. They are invisible except for one specific angle of light, and they look extremely fine...but I never noticed them before. I wonder if the crap on the mirror was abrasive? Meh. Anyway...guess that's the risk you take by cleaning... I doubt it will affect performance, I mean the entire mirror is used to resolve every star, but still. Freakin crappy. 

 

Anyway, the stuff did not come off as easily as I was hoping. Because I was afraid of scratching the darn thing ( ), I decided just to slosh the water around and let the cotton balls do their thing. It took a while. First the layer of fine whitish particulate came off, then dust and other particulate that was apparently stuck in the sticky layer started freeing. It took a couple passes with the alcohol solution to finally get all the sticky crap off. I rinsed with the alcohol solution, then distilled water, drained the mirror assembly (I decided I did NOT want to actually pop the mirror off the rear cell, as I figured I'd probably just end up getting finger prints on it while trying to put it back in.) I then dabbed up the few spots of water that were remaining with some Kimwipe tissues, lapped up water in the cell, in the threads, etc. Then just let it dry.