Dust/smudge on my telescope -.- clean it?

[123Star]

Hello again! My second post. 

I' ve saw some dust on my mirror and bought some propane air can to just blow it away. But I think some stuff from the can has blown out and hit the mirror. Its like a  fat/dust screen (or really fine dust). I didnt really notice it in daylight when I checked mirror but yesterday I was trying out my telescope outside and I checked the mirror in the dark with some light and then I noticed. I dont really know how much it effect the view couse in daylight the mirrior looks fine, unless I tilt the telescope to an angel where the fat/smugde reflects. Do I need to clean my mirrior? If so is it easy to clean? And I bet ill need to coliminate it after. 

And a pic of my stuff, it looks bad and homwmade but Ive made some "protos" of what I had available, untill I order the right material. I'm new to all this. 

Edited February 26, 2023 by 123Star
Correcting

[123Star]

I like to have things clean fyi

 

Edited February 26, 2023 by 123Star

[Peter Drew]

It's common advice not to use compressed air cans to blow dust off a mirror.  As you have found, the propellant can also exit the can and leave a deposit on the surface.    I doubt that it will cause a problem and in view of your declared inexperience it might be best to leave it rather than invite further problems.      🙂

[123Star]

Hnmm. Maybe best to leave it for now then. I thought it would be an easy job. My solution was to buy some acetone and just spray it on and then rinse with distilled water and dry with a hairdryer, outside. But I need to get the mirror out etc so yea maybe best to wait. Thanks! if no one has an easy fix? 

[Carbon Brush]

Determining 'easy' depends on your skill and experience, as well as the right tools and materials.

I'm not sure I fully agree with @Peter Drew this time - a rare event that warrants an explanation.😁
A compressed air canister should contain only dry air and a propellant that readily evaporates.
Given that the 'air' has left room temperature residues on the mirror, the manufacturer may not have good quality control.
Who knows what nasty stuff was lurking the can? If it is a non reactive grease no problem, but something else?
Yes mirror coatings are physically tough and non reactive. But proving this with (for example) bird droppings and fungus does not end well.

The quantity of non-shiny stuff on your mirror does not warrant cleaning. It is the nature of the material that would worry me.

If you do clean, there are several methods and different takes on choice of solvents and soaps.
But there is one common factor - patience.

David.

 

 

[ollypenrice]

It really is a beginner's mistake to obsess over the cleanliness of optical surfaces, especially when observing them with a light.  

Olly

[123Star]

Thanks for help! 😊

I so just to check, I tried the can air on my cleaned wall mirror and it left a little residue  a "dew" like spot that evaporated, but some tiny stains was left. I dont really know that much but I bet I would notice if the mirror needed cleaning by looking at the moon, and it would look bad (Spots etc) and stars would be "smokey"? 

Anyway thanks for the inputs and help. I guess I suffer of clean mirror obsession. 

 

[Ricochet]

13 hours ago, 123Star said:

I dont really know that much but I bet I would notice if the mirror needed cleaning by looking at the moon, and it would look bad (Spots etc) and stars would be "smokey"? 

No. You won't see any difference. The curve on the mirror means that any part of the image comes from all parts of the mirror, not just one point like on your flat wall mirror. 

[123Star]

Ok thanks! 

One last question😊

Like @Carbon Brush said, could this propan/butan eventually destroy the mirror coating if left over time?

 

[Carbon Brush]

Propane or butane evaporate at room temperature, leaving nothing behind.
There is something else that left a residue in the 'air' spray.
Are you sure it wasn't 'hair' spray🤣

Seriously, if you don't know what the residue is, it might be harmful to a mirror. It might also be quite inert.
Is there anything on the can ingredients list to help?

If it was my scope, I would clean the mirror.
Whether you do this depends on your skill/risk thinking.

If you add your location to your screen information, you might get an offer of help from a friendly local.

HTH, David.

[123Star]

No "only" propane/butane aerosol on label  It also reads condense from can could harm delicate electronics 😅

After some research, I feel like I could clean it and put it togheter again. I just dont have a tool for collimating, I need that anyway, when I get one. Ill consider cleaning it.

Thanks for the tips I will try to add that. 

 

[LukeSkywatcher]

That dew shield is too long 

[Carbon Brush]

Well Norway is much too far away for me to offer to help with cleaning and re-assembly.

Then again. superb scenery, chance to see aurorae.......🤣

 

[Sunshine]

On 26/02/2023 at 05:39, 123Star said:

Hello again! My second post. 

I' ve saw some dust on my mirror and bought some propane air can to just blow it away. But I think some stuff from the can has blown out and hit the mirror. Its like a  fat/dust screen (or really fine dust). I didnt really notice it in daylight when I checked mirror but yesterday I was trying out my telescope outside and I checked the mirror in the dark with some light and then I noticed. I dont really know how much it effect the view couse in daylight the mirrior looks fine, unless I tilt the telescope to an angel where the fat/smugde reflects. Do I need to clean my mirrior? If so is it easy to clean? And I bet ill need to coliminate it after. 

And a pic of my stuff, it looks bad and homwmade but Ive made some "protos" of what I had available, untill I order the right material. I'm new to all this. 

Now that is what I call a dew shield!

[Orange Smartie]

If the first rule of reflector ownership is don't obsess about your mirror, the second is only shine a torch down someone else's 'scope!

[ollypenrice]

To reassure yourself, look down the front of your telescope. Oh no! there is an almighty blot, right in the middle of the light path. Your secondary mirror! Does this obstruction ruin the view?

Olly

[123Star]

@ollypenrice Its not actually ruining the view when looking down the tube (like blocking light, its like dew), I see my face clear even with the smudge on mirror. I looked at the moon last night again and didnt really notice any difference from before. But I have learned how to treat s mirrior etc now, the "hard" way. 

[ollypenrice]

1 hour ago, 123Star said:

@ollypenrice Its not actually ruining the view when looking down the tube (like blocking light, its like dew), I see my face clear even with the smudge on mirror. I looked at the moon last night again and didnt really notice any difference from before. But I have learned how to treat s mirrior etc now, the "hard" way. 

No, my point was that the secondary is a pretty big 'defect' in the scope's light path and yet it is not, in reality, a defect at all.

Olly

[powerlord]

But let's face it.. Taken to extremes.. If the mirror was totally covered with chocolate sauce.. You'd see nothing. So the anal bit of me gets annoyed when people say 'it will not affect the image". Yes it will. What you are really saying is that the degredation will be minimal. However we all go to tremendous extreme lengths to eek out every little bit of info from those photons.. With our cooled cameras, sub mm spacers, etc.. So frankly it's never something I like to hear. Nor, the aversion to cleaning mirrors which is pretty easy.

Yes, unless you JUST cleaned it properly, it will have dust on it, made very visible with a torch. You need to learn what that level of dust looks like to ignore it. But as it builds up, there will come a time that it's worth cleaning.

For me, that's when I can look at it in daylight in the morning after a session and it looks dirtier than I'd like my car windscreen to be. And the longer you leave it, the more 'baked on' it gets. We talk about dust, but it's also probably evaporated water when it dewed over for example, leaving whatever was in that other than h2o. And rain drops can be particularly particular (sic).

 

[ollypenrice]

2 hours ago, powerlord said:

But let's face it.. Taken to extremes.. If the mirror was totally covered with chocolate sauce.. You'd see nothing. So the anal bit of me gets annoyed when people say 'it will not affect the image". Yes it will. What you are really saying is that the degredation will be minimal. However we all go to tremendous extreme lengths to eek out every little bit of info from those photons.. With our cooled cameras, sub mm spacers, etc.. So frankly it's never something I like to hear. Nor, the aversion to cleaning mirrors which is pretty easy.

Yes, unless you JUST cleaned it properly, it will have dust on it, made very visible with a torch. You need to learn what that level of dust looks like to ignore it. But as it builds up, there will come a time that it's worth cleaning.

For me, that's when I can look at it in daylight in the morning after a session and it looks dirtier than I'd like my car windscreen to be. And the longer you leave it, the more 'baked on' it gets. We talk about dust, but it's also probably evaporated water when it dewed over for example, leaving whatever was in that other than h2o. And rain drops can be particularly particular (sic).

 

There is a risk associated with manipulating optics which is as non-zero as you rightly say applies to contaminants on optics. This is a matter of cost-benefit analysis and risk assessment. We know that the effects of a small degree of contamination on a mirror cannot be discerned by any observer at the eyepiece in a double blind test. If it cannot be so discerned, what is the rational benefit of taking the risk of manipulating the optics? I can see none. You run the risk of damaging the optics for no perceptible gain in performance and, in this case, no perceptible gain means, quite literally, no gain since perception is what we are interested in.

Olly

[powerlord]

None olly. But you've made a bunch of assumptions there. How is 'small degree of contamination' measured. When it it more than this amount? Is there a lower amount for imaging?

It wasn't having a go at you, I agree.

All I was saying is, it's not an absolute. And frankly, if the op wants to have a go at cleaning, reassembly, re calibration, etc then I think as you just have done - sometimes explaining the pros and cons is a good approach that just a blanket leave it alone.

I was certainly petrified of touching the things from reading stuff on here for a while, but when I eventually did it - taking My newts apart, cleaning the mirrors, collimation, etc I realised for me anyway, it was easy peasy. I learned a lot from doing it. I did screw up on the first one though - dropped the secondary on the primary doing lots of damage. Hence above about giving op pros and cons. But now I've done it a few times it's no biggy. Mirrors aren't coated in unicorn tears - I clean perfectly easily with caloclean just like any other optics. But I don't do it every week. Maybe twice a year.

 

[stafford_stargazer]

This was mine yesterday morning, then an hour later.. now that's dust.😭