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Did I damage my primary mirror??

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#1 staticclover

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Posted 25 April 2014 - 02:01 PM

Ok, so I just bought my first scope about a month and a half ago, a used Zhumell Z10 It is great shape and looks well taken care of. It had a good bit of dust on the primary mirror and a couple smudges on the secondary so after watching several youtube videos and reading many articles and post on here I decided to pull em out and clean em. I used tap water and a tiny bit of dishwashing liquid to let it soak for about 15 min, rinsed with tap water and wiped very softly with my fingers and then cotton balls changing balls after ever swipe from the center to the outside edge. I did a final rinse with a gallon of distilled water and leaned it up against the wall to dry. Now for the issue. When I inspected it after drying, the mirror appears to have a goldish or copper colored dust on it, but there is not actually any dust on the mirror. You really can't see it when you look at it straight on, but when you look at it from an angle with the mirror out or shine down the tube you can see it. I have used the scope once since the cleaning and the views look good, but I don't really have anything to compare to. BTW, I did everything the same way with the secondary and it looks perfect. If this issue doesn't ring any bells to anyone, I will take some pictures and post them.

#2 The Planetman

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Posted 25 April 2014 - 02:08 PM

No, you didn't damage them. The coatings are fairly durable.
Question though....
Did you collimate it after reassembly?

#3 sixela

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Posted 25 April 2014 - 02:24 PM

We'd like to have pictures, yes.
Usually, it's just some residue picked up by the distilled water before it finally dried (which is why I tend to use a hair dryer to minimise the time it takes for the water to evaporate.

But it could also have been something starting to degrade the coatings (where do you store your scope? Not in a garage with a car that happens to have a running engine just next to it, I hope, nor very close to a sea with lots of salt ions in the air...)

#4 staticclover

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Posted 25 April 2014 - 02:25 PM

Hey The Planetman, Dawson Springs isn't too far away from me.
I did collimate, with an Autosystems laser. I'm still figuring all the collimating stuff out and I think I'm in the "ballpark". Not that I really know how to star test, but it looks good going by the pictures and videos of star test I have seen. I'm getting a collimating cap and have a Tublug on the way. The laser is just slightly out of collimation and I'm working on a jig to fix that. So to sum all this up, I think my collimation is probably passable but certainly not perfect.

#5 staticclover

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Posted 25 April 2014 - 02:44 PM

If I can figure out how to post pictures, I just took some and will get them on here.
I just pulled it back out to take a closer look at it. It looks similar to when you focus in on a quartz counter top except really small of course, it appears to have tiny gold flake in it. Now I need to clarify a bit, under a normal overhead light fixture looking at it with the mirror in your hands, it looks perfect. No water spots, scratches or anything. when I use my high powered LED light and look at it closely that is when I can see a gold cast in the mirror. I can also see it looking down the tube with a low powered red light at night. I am probably overreacting about this, at least I hope so.

#6 staticclover

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Posted 25 April 2014 - 02:50 PM

Oh, I forgot to answer some of your questions. I kept it in the house for a while, but everything was sweating really bad when I brought it in at the end of the night. The previous owner said he kept it in the house and the outside of the scope seems to confirm this. Now I am keeping it in a storage building, It's dry, no vehicles or chemicals in there and I don't live close to the ocean. The humidity can get high here, but I've only had it for 1 1/2 months now.

#7 Billytk

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Posted 25 April 2014 - 03:39 PM

Your mirror is fine, it's the coatings they put on the mirror. Keep your scope in an unheated garage if possible. Get a shower cap to cover the mirror end and cover the scope with something. this will reduce cool down times. when you bring the scope in for the night, keep the tube horizontal so that any dew that may form will run off the mirror.

#8 Peter Natscher

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Posted 25 April 2014 - 08:29 PM

I've had this same result with tanish coloring remaining on my mirror when I used acetone and generic cotton pads for a final rinse. Don't use pharmacy store cotton. It can leave a colored residue with certain liquids. Use certified optical paper or wipes. Re-clean the mirror and the coloring will disappear.

Ok, so I just bought my first scope about a month and a half ago, a used Zhumell Z10 It is great shape and looks well taken care of. It had a good bit of dust on the primary mirror and a couple smudges on the secondary so after watching several youtube videos and reading many articles and post on here I decided to pull em out and clean em. I used tap water and a tiny bit of dishwashing liquid to let it soak for about 15 min, rinsed with tap water and wiped very softly with my fingers and then cotton balls changing balls after ever swipe from the center to the outside edge. I did a final rinse with a gallon of distilled water and leaned it up against the wall to dry. Now for the issue. When I inspected it after drying, the mirror appears to have a goldish or copper colored dust on it, but there is not actually any dust on the mirror. You really can't see it when you look at it straight on, but when you look at it from an angle with the mirror out or shine down the tube you can see it. I have used the scope once since the cleaning and the views look good, but I don't really have anything to compare to. BTW, I did everything the same way with the secondary and it looks perfect. If this issue doesn't ring any bells to anyone, I will take some pictures and post them.



#9 okieav8r

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Posted 25 April 2014 - 09:14 PM

I've had this same result with tanish coloring remaining on my mirror when I used acetone and generic cotton pads for a final rinse. Don't use pharmacy store cotton. It can leave a colored residue with certain liquids. Use certified optical paper or wipes. Re-lean the mirror and the coloring will disappear.



If you're using cotton, make sure it is medical grade cotton--which is pure, sterile cotton, and nothing more. It isn't capable of discoloring a mirror. It's never caused any cleaning issues for me.

#10 Bill Weir

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Posted 25 April 2014 - 10:51 PM

Don't even use abrasives like cotton at all. Wet soapy fingers are good enough.

Bill

#11 TCW

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Posted 25 April 2014 - 11:29 PM

Don't know about the dust issue but the following may help a bit.

If you carefully rinse the mirror at an angle almost all the water will run off. Next keep the mirror at an angle and use compressed air from a can and gently blow the remaining water drops off. Don't use much or you will freeze the water drops to the mirror as the air coming from the can can be very cold due to expansion.

#12 John Fitzgerald

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Posted 26 April 2014 - 09:13 AM

Don't look at the mirror in the dark with a flashlight. A newly cleaned mirror will look horrible.

#13 Binojunky

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Posted 26 April 2014 - 09:42 AM

Don't even use abrasives like cotton at all. Wet soapy fingers are good enough.

Bill


Hope you keep your nails nice and short? :grin:DA

#14 staticclover

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Posted 26 April 2014 - 10:00 AM

Post deleted by staticclover

#15 staticclover

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Posted 26 April 2014 - 10:05 AM


I posted some photos of the primary on Google+, give this a try:Mirror pictures

#16 Starman1

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Posted 26 April 2014 - 01:36 PM

I posted some photos of the primary on Google+, give this a try:Mirror pictures

OK, the mirror in the pictures is, hopefully, filthy.
The bluish tint is the result, probably, of a MgFl2 overcoating (not a bad thing).
A goldish color could be indicative of tarnish in the aluminum coating, or it could be indicative of extra dielectric coating layers added to the mirror. If the color is only visible at an angle, but disappears when you look straight on, it's probably not tarnish. As aluminum tarnishes, it tends to appear grayer or hazier, anyway.
But, IF the mirror in the pictures has been freshly washed, then the mirror probably needs recoating. A freshly-coated mirror, if you look at a very bright light through the back of the mirror, will have a small handful of pinholes in the coating. I hold it up to the sun to see this, but a bright studio light will work.
As the coating ages, the number of pinholes increases. When the coating is really old and on its last legs, it looks like the mirror has measles, kind of like the pictures.
I'm hoping your pix were pre-cleaning.

#17 DocFinance

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Posted 26 April 2014 - 01:46 PM

Never seen that kind of thing before. Yowza.

#18 staticclover

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Posted 26 April 2014 - 02:43 PM

This was a post cleaning picture. When I look at it in the sun or under bright overhead lights, it looks absolutely perfect. When I look down the tube at it at night with a red light, it appears to have some fine "dust" on it, but looks much better than before the cleaning. The light I was using to take the picture is a high powered 3 LED hunting light I use to do work around the farm after dark. This thing puts out a really strong white light. When you have it on in the rain, the reflection from the rain drops look like Christmas lights and animal's eyes can be seen from a loooong way off. So this light really shows the flaws in anything. I'm not sure if every primary would look this way under this type of light or if it's just mine. If I ever get the chance, I will try it on another mirror. Does the secondary mirror have the same coatings as the primary? The secondary mirror has none of the look that the primary does and I did the same cleaning process on it. The scope is only about a year old and the previous owner said he has never cleaned it and kept it in the house and it looked well taken care of when I picked it up. I don't believe this was a bad deal or anything, he sold this to get astrophotography set-up. If the mirror was already like this before I cleaned it, you wouldn't have been able to tell with the dust on it. It wasn't super dirty, but I just couldn't leave it alone.

#19 azure1961p

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Posted 26 April 2014 - 02:54 PM

You know what - get it recoated.

A ten inch mirror is not expensive to get recoated and you'll like your options the folks out there have to offer on different degrees of reflectivity.

Another thing - and I know Ill draw scorn for this but I'm careful about it and have NEVER introduced a sleek ever. After the typical soapy water thing, I rinse with tap water, then alchohol I leave it on its side to dry .

Ahhh that very pale blue haze at that low angle when studying the mirror. And, a residue spot here and there.

I've resigned to the notion these will NEVER come off chemically ever.

But, I didn't give up...

I open up a fresh box of Kleenex - take several in a loose bundle - MAKING ABSOLUTELY SURE MY FINGERS DON'T TOUCH the part that will contact the mirrors surface.

I give a dry rub a couple times and the haze is gone as are the water spots. And I mean virgin clean.

I give the tissues a fair shake before the dry buff.

There you go. Try it. If its still there - send that baby out and for probably $150 you'll have dandy new coatings better than it ever had and that includes the secondary.

Pete

#20 sickfish

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Posted 26 April 2014 - 02:57 PM

I have had my dob for 4 years and have not cleaned the mirror once based on what i have read here. I always thought a little dust is fine and just blowing it off and it should be ok. How old is this scope? Is this just age of the mirror?

#21 sixela

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Posted 26 April 2014 - 03:11 PM

I posted some photos of the primary on Google+,


Doesn't look like a healthy coating, if you ask me.

You'll be fine just now, but the GSOs I've seen with a similar appearance tended to evolve badly in time (one of them, though, had been damaged by being stored in a garage and being attacked by aggressive car fumes).

If it's under warranty, I'd talk to the vendor to see what he thinks. Of course, he could argue that it's currently benign, but if it evolves badly just out of warranty...

On the other hand, I'd star test the scope and if the scope star tested to be finer than I expect for that class of scopes, I wouldn't use the warranty (you could get a mirror with a worse figure!)

#22 azure1961p

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Posted 26 April 2014 - 03:59 PM

I have had my dob for 4 years and have not cleaned the mirror once based on what i have read here. I always thought a little dust is fine and just blowing it off and it should be ok. How old is this scope? Is this just age of the mirror?


If your forte' is deepsky you might want to rethink that. And if you enjoy seeking faint moons around planets, again you may want to adopt a more frequent method. Nobody would operate a refractor or cassegrain with the amount of dust a Newtonian can develop in four years on their objective.

Having said that - a sct corrector or refractor objective will stay far cleaner for far longer than a reflector simply because the amount if free space between the dust cover and glass simply doesn't hold anywhere near the dust the inside of a reflectors tube can.

Pete

#23 Starman1

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Posted 26 April 2014 - 04:06 PM

You know what - get it recoated.

A ten inch mirror is not expensive to get recoated and you'll like your options the folks out there have to offer on different degrees of reflectivity.

Another thing - and I know Ill draw scorn for this but I'm careful about it and have NEVER introduced a sleek ever. After the typical soapy water thing, I rinse with tap water, then alchohol I leave it on its side to dry .

Ahhh that very pale blue haze at that low angle when studying the mirror. And, a residue spot here and there.

I've resigned to the notion these will NEVER come off chemically ever.

But, I didn't give up...

I open up a fresh box of Kleenex - take several in a loose bundle - MAKING ABSOLUTELY SURE MY FINGERS DON'T TOUCH the part that will contact the mirrors surface.

I give a dry rub a couple times and the haze is gone as are the water spots. And I mean virgin clean.

I give the tissues a fair shake before the dry buff.

There you go. Try it. If its still there - send that baby out and for probably $150 you'll have dandy new coatings better than it ever had and that includes the secondary.

Pete

I agree about the recoating. The first coating may have been applied to a mirror not completely free of debris.

As for not cleaning:
--the mirror surface is not easily scratched when cleaned wet.
--reflectivity can drop >20% in one year (!) on an uncleaned mirror due to dust, pollen, organic materials, and haze. Cleaning the mirror restores the reflectivity, so you're sacrificing a lot of image brightness by not cleaning.
--you should never, ever, rub the dry surface of anything on a dry mirror surface. THAT is guaranteed to leave fine scratches.
--at the least, you should perform a distilled water rinse of the mirror fairly often (2-3X/yr) to get rid of loose dust, pollen, etc. You don't have to rub or anything, just rinse and let dry. Some of the dust that settles on the mirror is alkaline, and, when mixed with dew or simply moist air, can start eating the coating right off the mirror. Rinsing it off will help preserve the coating.

#24 sickfish

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Posted 26 April 2014 - 04:29 PM

So even if I dont see alot of dust should I still rinse the mirror ?

#25 Starman1

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Posted 26 April 2014 - 04:54 PM

So even if I don't see a lot of dust should I still rinse the mirror ?

I suppose a lot depends on the storage and use.
A telescope used nightly will require more maintenance than one used once a month.
And a mirror stored vertically will collect a lot less dust than one stored horizontally.
So if there is minuscule dust, perhaps a simple air bulb will blow it off.
But a lot of dust is exceedingly fine, and it is this dust that is more likely to damage the mirror in the presence of moisture.
A mirror used near the ocean will require far more frequent cleaning than one used a hundred miles inland.
Rationality says one should tailor the cleaning to the usage, storage, and conditions of use and storage.
Rinsing is so easy, though, I can't imagine it being a problem to err on the side of caution and rinse more rather than less.






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