Clean, recoat or leave alone

[assouptro]

Big Blue has been our for 2 nights in a row now!

I really need to catch up on some ? 

up till sunrise both nights, it has been great fun! 

Anyway.

i would appreciate some opinions on my secondary mirror.

to my eye, I think it may benefit from some TLC but I am not sure.

I'll include some photos of it, I have tried to capture a reflection showing the worst of it 

Does it need cleaning? 

Should i send it off for a recoat? 

Or leave well alone and drop being fussy?

Cheers 

Bryan 

[ronin]

My view is clean it and see if that makes any improvement, equally I will clean anything optical.

It does actually look as if you could have to have it recoated, I guess those little patches are where the protective coating has failed and that the aluminium beneath is corroding, same for the edges where oxygen will have gained access via the edge which has been less proteced also.

I think it will need a recoat to be honest, but that means that a careful clean of it can in effect do no harm and maybe some marks will not be Al2O3 (where are the options for suffix etc now?) and they will be removed leaving a better idea of the true state.

Edited April 23, 2017 by ronin

[Peter Drew]

+1 for Ronin's post. 

[assouptro]

 

8 minutes ago, ronin said:

My view is clean it and see if that makes any improvement, equally I will clean anything optical.

It does actually look as if you could have to have it recoated, I guess those little patches are where the protective coating has failed and that the aluminium beneath is corroding, same for the edges where oxygen will have gained access via the edge which has been less proteced also.

I think it will need a recoat to be honest, but that means that a careful clean of it can in effect do no harm and maybe some marks will not be Al2O3 (where are the options for suffix etc now?) and they will be removed leaving a better idea of the true state.

Thanks for that Ronin

would you clean it in situ? Or remove and submerge in water? 

[alacant]

Size:

Edited April 23, 2017 by alacant

[alacant]

13 minutes ago, ronin said:

options for suffix

Al2O3

HTH

[assouptro]

20 minutes ago, alacant said:

Size:

I'll measure it.

[assouptro]

It's 35mm

[alacant]

They're economical items. Just get a new one? HTH.

[Peter Drew]

35mm secondary on a 22" Newtonian ???, has the end fallen off your tape rule? 

[assouptro]

 

32 minutes ago, Peter Drew said:

35mm secondary on a 22" Newtonian ???, has the end fallen off your tape rule? 

350mm! ?

[assouptro]

Ok 

so i washed it

 carefully

rinsed it with de-ionised water then dried it with a hairdryer 

I am of the opinion that it probably would benefit from a recoat, it reflects directly well but from an angle looks as "dirty as before, this must be oxidation? 

Photos included 

[Alien 13]

Ouch that looks bad, it might be worth holding it up to a bright light to see if more gets through than is reflected. If you do see a lot of light through it I might worry that the surface is compromised too if not then a re coat would fix it.

Alan