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Old 04-10-2019, 01:22 PM
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LewisM
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Honest discussion on scratches

Let's talk frank about the effect - or lack there of - of scratches to a mirrored optic.

If you read my and Stuart's original for sale ad on the R200SS Turd, you'll know the primary and secondary had been cleaned incorrectly - there are very small, almost unnoticeable scratches to both. Otherwise, the aluminisation is perfect (except the secondary which has mold etching spots - only a couple).

On refractorss, I can see how scratches will affect the light, espeially for immaging (spikes etc), but will you get ANY effect whatsoever on a mirrored telescope? Sure, you'll get a small amount of scatter (minute I'd imagine), but since the light is not being refracted through a lens, will it have any noticeable effect even imaging?

If it was heavily scratched, sure, i'd play ball, but small scratches you cannot even see unless you take out the mirrors?

I've decided to keep it and use it. If it doesn't work for me imaging, it becomes the family and school outreach scope.
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Old 04-10-2019, 02:00 PM
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Rainmaker (Matt)
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Minor scratches will only induce minor scatter. For most people it will not matter and will likely pass unnoticed at the eyepiece. I think the original issue with this scope was not the minor scratches per se, rather that the seller's description did not match the scopes condition.

I think you will enjoy the scope as a fine visual scope, especially since the excessively thick spider vanes have been machined to better specs. I had one of these several years ago and it gave superb visuals of M42 from a very dark Jindabyne....

Let me know when you're ready to collimate.
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Old 04-10-2019, 02:35 PM
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Unfortunately, yes, the seller's desription was terribly inaccurate. No ifs or buts, this is a $500 telescope. The PH corrector is worth more (now coming to me too). Heck, I paid Steve less for your former prime example than Stuart paid for this hum-dinger.

I'll do some refinishing (I'll paint it turd-brown just for Stuart...nah, just kidding) then you can teach me the fine art of precise collimation. f/4 is definitely not my comfort zone
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Old 04-10-2019, 03:24 PM
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Rainmaker (Matt)
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Did Strawb supply the original cap, manual etc...?
The manual should have some collimating instructions in it...
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Old 04-10-2019, 03:29 PM
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Quote:
Originally Posted by Rainmaker View Post
Did Strawb supply the original cap, manual etc...?
The manual should have some collimating instructions in it...
Nothing. Bare scope and rings, but with the PH corrector and the added dew heater pads. Apparently, the PH corrector is covered in dust and crud as it was left in the scope (I should get that sooner or later). Seems this scope was already second hand as sold, making me potentially the fourth "possessor".

I spent the better part of 2 hours today removing the Liquid Nails slopped on the primary cell with lacquer thinner...cheap high...weeeeeee..... I should do a step by step resto post on this one.

Anyway, back to optical effect of scratches on mirrors...
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Old 04-10-2019, 03:31 PM
garymck (Gary)
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If it was anything other than a Vixen, it would be worthwhile re aluminising it. Unfortunately the mirror would have to go back to Japan for that. Vixen does not figure the glass, the figure is created by the way they apply the aluminium coating.......

Gary
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Old 04-10-2019, 03:32 PM
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Rainmaker (Matt)
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Quote:
Originally Posted by garymck View Post
If it was anything other than a Vixen, it would be worthwhile re aluminising it. Unfortunately the mirror would have to go back to Japan for that. Vixen does not figure the glass, the figure is created by the way they apply the aluminium coating.......

Gary
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Old 04-10-2019, 03:39 PM
glend (Glen)
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Stick a GSO mirror in it, if your going to keep it. Bintel sell them. Of course it's pretty cheap to just buy a GSO 200mm imaging newt from Andrews, if you really want that apeture.
Honestly, a scope with that list of problems probably is best given away to a youngster to play with, or put out in the Council cleanup/recycle. Trying to resurrect it is just going to be frustrating and involve more money.
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Old 04-10-2019, 03:40 PM
beren
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Quote:
I think the original issue with this scope was not the minor scratches per se, rather that the seller's description did not match the scopes condition
In correspondence with the seller, he believes both mine and Lewis assessment
is inaccurate and the scope is not as bad as we think it is . He also claims to have hardly used it which he seems to imply no responsibility for its condition
when he sold it. I believe the price Lewis paid for the scope is worth it and although in rough cosmetic condition it should still pull nice images both visually and for imaging use. I was very near buying a new r200ss but unfortunately was messenged through the pms on this scope and was lead to believe it was in good condition. This lead to a significant ( for me ) cash outlay, it will be sometime before I can ( if I ever do ) a new one ......anyway please be careful and try to get as much information as you can before buying used equipment
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Old 04-10-2019, 03:50 PM
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Quote:
Originally Posted by glend View Post
Stick a GSO mirror in it, if your going to keep it. Bintel sell them. Of course it's pretty cheap to just buy a GSO 200mm imaging newt from Andrews, if you really want that apeture.
Honestly, a scope with that list of problems probably is best given away to a youngster to play with, or put out in the Council cleanup/recycle. Trying to resurrect it is just going to be frustrating and involve more money.
Why? The figure is still perfect, and I seriously doubt that a few small scratches - small as in you need to get CLOSE to the mirror to see them - is going to affect it at all.

The rest of the scope is a dog's breakfast that I am determined to fix up. I just reblackened the rear housing of the mirror, and it already looks a fair bit better.

Long road ahead, but should be OK in the end.

If all else fails, I will put it up as a freebie for someone who can PROVE it will be for institutional use, not personal rubbing-hands glee...
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Old 05-10-2019, 07:03 PM
rrussell1962
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Quote:
Originally Posted by garymck View Post
If it was anything other than a Vixen, it would be worthwhile re aluminising it. Unfortunately the mirror would have to go back to Japan for that. Vixen does not figure the glass, the figure is created by the way they apply the aluminium coating.......

Gary

A very interesting comment. I know this is true of the VC200L but I had no idea it applied to the Vixen Newtonians.

As for the scratches - I find it is best not to look at the mirror. The more you look at them, the worse they look. Fortunately the image quality stays much the same.
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Old 09-10-2019, 05:36 PM
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Lewis,

small scratches will not be any real issue, some minor scatter but fairly insignificant. It depends on what the scratches look like and how deep they are are in the coating and mirror surface. My RC12 with dialectic coatings was subject to spider faeces 5 years ago. The faeces left a 50 cent piece sized area with small spots with mirror coating eaten away. I have not noticed any significant degradation in performance of the mirror. So small scratches will be the same. I wouldn't bother with getting it re-coated. Do you have a shot of the scratches?
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Old 09-10-2019, 07:11 PM
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Paul,

SO hard to photograph!

They are radial - whoever cleaned it incorrectly was wiping the mirror in a circular fashion. Light enough to make me think at first they were spider silk, but even finer.

I agree completely - I really don't think there will be any noticeable degradation whatsoever, visually or photographically.

I hav begun the restoration in earnest - the focuser was the trickiest thus far - 2 hrs work - since there were numerous issues, most notably being the teflon pad of the drawtube being almost out of it's slot. How that happened, who knows, but considering the amount of DIY bodgery on this, it is unsurprising really.

I have now completely disassembled the primary cell housing and done a lot of work there too. I ordered the replacement Vixen decals, so hopefully I can get the OTA done soon.
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