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Marks on mirror


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Hello all

When I first got my scope a few months ago (Skymax 127 MAK) I noticed there were a few small marks on the front mirror. It's not dust but kinda looks like glue. They were very very small and didn't affect viewing at all plus the dealer said it was no problem.

Now these marks, while still small, are getting a little bigger. My initial impression was that these were outside marks but I think it's perhaps some sort of lining peeling away from inside. Again it doesn't seem to be hampering vision at all and they are still quite small but noticeable when you take the cap off.

What do you guys think / suggest?

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The corrector front plate is coated to reduce reflections, but I doubt if it is peeling off. It's not like it's a skin that has been added. The coating is deposited onto the glass in a vaccuum chamber, as with the aluminium coating on the main mirror.

At least, that's how I believe it is applied.

How long have you had the telescope?. If it is still under warranty, you must at least report what you have noticed to the dealer from whom you bought it. Do not attempt to do anything yourself.

Keep an eye on it, and if it starts to spread wider afield, then contact them again and tell them you wish to have it rectified. One way or another. Above all, let them know now, and keep a record of the correspondence.

Ron.

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I bet the dealer would not be so relaxed about it if it was his / her personal instrument !.

As Ron says, I would try and get sorted under warrenty if you can - particularly if it apprears to be on the inside of the corrector plate and spreading. It's probably not affecting the image quality but new optics should be unmarked - why should you have to put up with anything less ?.

If not sorted it will affect the re-sale value of the scope as well, and again, why should you take that hit ?.

Get on to the dealer and keep a record of your dialogue with them. A decent dealer would replace the unit with no quible at all.

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My thoughts exactly.

I told the dealer immediately when I first got the scope and he said that all scopes can handle marks on them up to 5 square mm. I still wasn't too happy with this as like you I think if you pay good money you should get your product in perfect condition.

I've just spoken to him again and he wants me to email him a photo of it. I'll send you guys a photo shortly too.

I'm sure he will replace it, he's a decent enough guy, I'm just curious as to what the marks actually are and how come they are getting bigger.

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I've heard of older optics occasionally suffering from fungus which spreads if not dealt with of course. An alternative option would be a fault with the application of the coating on the inside surface of the corrector plate - a lack of adhesion perhaps.

Scopes can cope with all sorts of marks / debris on the optics and still perform OK but that's not the point - you paid for a new scope (presumably) so you are entitled to one in new condition. Unless these marks were declared by the seller prior to the sale then I can't see they have grounds not to rectify the issue.

So don't get fobbed off with the "well it won't affect the performance" argument.

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You might like to inform the dealer that as you are a member of a very large Astronomy Forum. (You don't have to name it.) you did seek advice from the general membership, who have expressed a big interest in the outcome of your scope problem.

Ron.

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Wow thanks guys!

Could minus temperatures cause this? Like -5 for example...?

Anyhow here are some photos of it. It actually looks not so bad as in the photos - they seem to have picked up every minute grain of dust! I am careful with it..honest!

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It's kept in an indoor balcony which is double glazed albeit a little cooler than the rest of the house, between 17 - 21 degrees. Yes, everything is always capped and I have a light sheet which I throw over it all. In terms of it's position its pointed straight ahead but set to my altitude of 49 degrees so it is kinda up a bit, is that bad?

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I was thinking in terms of a recent case, whereby a member had a problem with the grease from his Meade LX Baffle had dripped out onto the corrector plate. It was assumed the tube had been left in an inverted position for some length of time, and in a warmish environment. That is more than likely not the case with your scope though. It had a happy ending though, the plate was carefully removed and successfully cleaned.

Ron.

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Some of those marks look like patches where the coating has flaked off. It's difficult to be sure as Ron says but if that was the conditon of the scope when it arrived from the dealer then I'd not be happy personally. I bought one of those new a couple of years back (mine was on the SupaTrak mount) and the optics were immaculate when it arrived.

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They look like dew marks, and he may come back with that. However, if you have only had the scope a short time you are in your rights to ask for a replacement or refund. Go back to the dealer and demand that if required. If you still find problems make a report to OVL (optical Vision Ltd) direct thats the UK importer.

Rob

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Hmmm...if theyr'e dew marks it means that I've been sent a used scope as they were there when I first received it.

To be honest, I was wondering about dew though. I know dews a pain but I didn't realise it could damage the scope so quickly. I do use a dew shield and haven't actually spotted dew on the front before.

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The dew won't damage the scope, you may get some dew spots after a night out, it's unavoidable. The dealer maybe alluding to this as dew on the corrector is not his problem and it takes a badly caked corrector to have an adverse effect on performance. But if the marks were there when the scope was delivered, i would have that scope changed asap!! No question about it.

I'm really not sure those are dew spots though. Either way, i would get the scope swapped out.

As for dew shields, they quite often fail to work as a successful prevention of dew on the corrector. Quite often you'll need active dew prevention in the form of heated dew straps to keep the dew at bay. Think of the dew shield as more of a light scatter shield.

Russ

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Having a closer look at the photos, i'm convinced those are nothing to do with dew. Look more like flakes of paint on the inside of the corrector plate. As the others have said, it's hard to tell.

Russ

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The corrector front plate is coated to reduce reflections, but I doubt if it is peeling off. It's not like it's a skin that has been added. The coating is deposited onto the glass in a vaccuum chamber, as with the aluminium coating on the main mirror.

At least, that's how I believe it is applied.

Yes, that is how they are applied -- but it is possible for them to peal off. Usually if there was some contamination left on the glass before the coating. However, the pictures here don't really look like pealing coatings.

Have the marks really grown, or are there now just more of them?? It's hard to tell from the photos what they are. They do look like solid flecks on something, rather than marks on the coatings...???

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Yeah they're definitely getting bigger. I remember there were about 4 or 5 of them when I first received them but they were much smaller, little tiny flecks. I remember reading on here that some other MAK user had a little light bllue paint or glue on the white rim - I had that too.

About all the other smaller obviously dust - I don't know what to do generally. This thing seems to attract dust like it was born to do so! I always keep it covered when not using it, store it well etc I know I shouldn't touch it really so I haven't but as nbrus points out it is pretty bad!...so any advice on the normal day to day gathering of dust would be appreciated!

Anyhow spoke to the dealer again and I'm posting it back.

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That defo looks like the optical coating peeling off... If they dont clean the sample properly or for whatever reason tiny drops/bits grease or dust get on it before the deposition the film wont stick properly... You wont see it to begin with but as its handled they'll start to show and grow as the film flakes off... You dont even need to handle it, just the changing temp coupled with the different expansion coeffs of the substrate and film can cause them to separate at alarming speed once they have started to go!

Tell him you want it changed! NOW!!!!

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Sorry Mike I meant the corrector plate. I dare not try to get to the secondary mirror!

I used my new finderscope the other night (it came in very good condition) but now it has two tiny flecks on it as well! I must be doing something wrong!

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