HELP! MY PRECIOUS MIRROR IS IN DANGER!

[Ganymede12]

So, a few nights ago I went out for what was the first time in ages. I was even able to capture a moderately decent image of Jupiter. But when I headed back inside, I saw something on the mirror of my precious Skyliner 200P Dob...

It looks like something has fallen on to the mirror, but I don't know what it is. I've tried holding the OTA at an angle in the hopes that gravity would sort it out but no such luck. It looks like I will, reluctantly, have to remove the mirror. This is something I have never done before and am not exactly keen on doing. So, If I was to remove the mirror, how would I do this? How easily will I be able to refit it? Also, is it worth buying a screen cleaning kit to blow whatever the black spot is and some dust off of the mirror?

[Chris]

Hi, just undo the screws on the side of the tube at the very bottom. This will allow you to remove the primary mirror cell containing the mirror.

No need to disturb the mirror other than to blow the object off with an hurricane blower. 

[kev100]

Or try this:  http://stargazerslounge.com/topic/238868-air-in-a-can-to-get-crud-off-of-primary/?hl=+straws

[Chris]

Even if you left it there it wouldn't effect the views, but I would remove it because it would bug me else

[RLWP]

Could you rig up a vacuum cleaner and some clear plastic tube to remove it?

Richard

[xtreemchaos]

hi mate removing the mirror is easy just make sure to make a mark with a bit of tape on the tube so you put it back right and make sure you have no distractions,it looks like a peice of leaf thats dropped down there.dont worry too much im sure it will blow off .

[quaoar]

Here grab a cup of tea and watch this video https://www.youtube.com/watch?v=9Y8xFnXFVGQ      It's no biggie, I get Rubbish on my mirrors all the time I've got a spider web draped over the one I'm using right now.

[spaceboy]

It probably won't make any noticeable difference to the views but it is good to get in to the habit of removing such things before they become fused to the mirror and cause you no end of irritation. Phillips screw driver and a rocket blower...... job done!

[Peter Drew]

It's not as big as your secondary mirror!   

[Gazabone]

Removed the primary on my 250P a while back. Me and DIY are completely alien to each other but even I found it easy. Just needed to re collimate the scope when I finished but with a laser collimator that was less than 5 mins work.

The advantage of a dob is they are beautifully simple, lovely pieces of kit.

[John]

It's not going to affect the views as Peter says. If you lay the scope tube on it's side and gently slap the mirror end of it the object (dead fly ?) may well just fall off the surface of the mirror anyway.

"Don't Panic" to quote the The Hitchhikers Guide

[ghostdance]

Here grab a cup of tea and watch this video https://www.youtube.com/watch?v=9Y8xFnXFVGQ      It's no biggie, I get Rubbish on my mirrors all the time I've got a spider web draped over the one I'm using right now.

On balance I think I prefer this:

Although I've not (yet) washed my mirrors, the thought of wiping it with my fingers and not using distilled water as in the first video is just a bit worrying! Or am I being unnecessarily paranoid?

BTW (sorry for hijack, but I've always wondered)  - does the centre spot usually survive washing? Or can it 'float' off, necessitating applying a new one? 

[Chris]

I've used the method in the above vid once so far and it worked really well. I wouldn't do it at all though unless the mirror was very dirty.

[Ganymede12]

Thanks for the responses! When I get the time, I'll give it a bash (not literally of course). What is a hurricane blower?

[Cath]

DO NOT do ANYTHING to/with what you're panicking about 'ganymede12'

Allow things to settle beforehand, allow time beforehand

[niallk]

I stuck my hand in front of my 15" on Jupiter- just to see... - amazing how tolerant the image at the ep was . Grossly defocussed it was also amazing to see the thermals swirling off my hand...

[quaoar]

You can avoid touching the mirror by using a couple of squirt bottles and distilled water.

The squirting action combined with  liquid detergent removes 99% of stuck on gunk.

Squirt off detergent solution with distilled water squirter. Then rinse with neat distilled water to reduce the number of droplets on the face of the mirror to a minimum.

Wick off the big drops with pointy paper towel.

[Skyline]

Get the Brillo Pad out  

[ollypenrice]

I think any water will do for the fast rinse and no touching is the best touching. The final rinse should be in pure water, not surprisingly. My mirror is way too big for the sink so I use the shower at tepid temperature. The centre dot does survive (ten years and counting).

Olly

[Dom1961]

Quick question, where does everybody get their distilled water?

[russ.will]

I had a spare mirror, so I thought I'd try the finger method with lots of soap after a really good soak and then rinse under a tap. the soap forms a film so your fingers cannot touch the mirror surface, but you can feel where really stuborn spots are so as to massage the soap in further. I used Halfords de-ionized battery top up water for the final rinse and made sure I blew all drips off with a hurricane blower. The result was an absolutely pristine mirror without even so much as the tiniest blemish or scratch, even under a magnifier.

It gave a view no better than the dew streaked, crud infested one.

People get too obsessive over cleaning methods and the need to clean them in the first place.

Russell

[mikeobrien]

You can get it from tesco!

[RLWP]

You can buy it or nick it from Woolworths, but I doubt...

B&Q also sell distilled water, and our condenser clothes dryer makes the stuff - we throw it away

Richard

[Skyline]

I tend to use Osmosis water from a marine aquarium shop.

[Ouroboros]

I've used deionised water for years with no obviously adverse effect on the mirror. I find deionised easier to get hold of than distilled, which I have never found an outlet for - not that I've looked very hard. Purists don't like deionised on the grounds that it may contain organics. However it's dissolved carbonates that leave streaks on a mirror rinsed in tap water. These are absent from deionised water. Moreover organics are ever present in the air, to which our mirrors are constantly exposed, so the tiny residue of organics possibly left by rinsing with deionised water are probably insignificant. They won't affect optical quality anyway.