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Old 08-01-2011, 07:39 PM
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Russian (Stephen)
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can light scratches be removed from a primary mirror by polishing ?

Can anyone tell me , what they think of this?

I purchased a Guan Sheng GS-530 8" OTA from Andrews ############## before xmass , when I inspected the telescope after unpacking it , i found two light scape marks on the primary mirror + it was very dirty or oily and the screws holding the finderscope base had been over tighted and had deformed the tube a little , i emailed pics of the mirror and base, than called them by phone later , they got me to send the scope back so they could have a look at it over the weekend.
I called them on the Monday and they said they had repaired / polished the mirror and was sending the scope back.

When i got it back and looked at the mirror it was better but i can still see the marks and it looks like they didnt even remove the mirror from the carrier to do the job and there are swirl marks like a badly cleaned mirror.

I have sent them an email saying i am not happy with what they have done and to send me a new mirror assy , they are still closed for xmass but will be reopening on Monday .

I am new to astronomy, but i have had 3 scopes , the first one was a dick smith special , than a SKYWATCHER 150 , now the Gaun Sheng.

Are the trying to rip me off ?
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Old 08-01-2011, 08:14 PM
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GeoffW1 (Geoff)
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Hi,

A primary mirror in a common reflector cannot be polished as such, only carefully cleaned, and that as little as possible. There should not be swirl marks from a competent cleaning.

If we define polishing as removal of small amounts of material, all that happens before the mirror is finally coated with reflective material, in a very thin and vulnerable layer.

So once the reflective coating is so damaged (not just dirty), as to degrade performance, the only practical option is re-coating, as far as the mirror is concerned.

In fact a few light scratches will not make a huge amount of difference to the scope's performance, but I think that is not the point.

In theory if you buy a new scope, you are entitled to receive all parts of it in as new condition, both visually and optically. In your position I would not listen to any arguments that a visually flawed mirror will still give good results optically.

Strictly legally I think that you are entitled to return the whole scope to them at their expense (although that last bit might get difficult) and require a replacement scope or a refund. I believe that it is at your option as to whether it gets repaired in some way, and personally I would refuse that option. Also I would not disassemble the OTA and mirror cell whilst it is under warranty, even if they ask you to.

Now the confusion begins. I don't know what conditions and limitations they place on shipping damage, or if such can be made to stick (if they say that).

If they will not respond in a favourable way to several polite requests (keep a record of everything, when and where), you might need to contact the NSW Dept of Fair Trading.

BTW, if the vendor is who I believe you mean , they have a reasonably good reputation to protect, and I'd be surprised if they did not try to clear up any trouble.

Cheers

Last edited by GeoffW1; 08-01-2011 at 08:24 PM.
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Old 08-01-2011, 09:01 PM
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Russian (Stephen)
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Thanks for the info , I think the mirror was damaged before the the scope was assembled in the factory or when it was assembled.

steve
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Old 08-01-2011, 09:06 PM
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multiweb (Marc)
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Andrews com are alright. I'd take it back and get it exchanged. Don't fiddle with it or try to fix it.
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Old 08-01-2011, 09:46 PM
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jjjnettie (Jeanette)
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I'm sure they'll look after you.
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Old 09-01-2011, 02:54 AM
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asimov (John)
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Yep, no mucking about. If you're not happy (and I wouldn't be) send it back & tell them you want a replacement. Lee is a firm, but fair man.
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Old 09-01-2011, 12:48 PM
gb_astro
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Polishing a mirror to get ride of scratches is a completely irresponsible remedy
and would certainly make the mirror worse than it was.
If it has been polished you have a stronger case now for replacement than you had before.
I guess the question is what exactly they did to the mirror?

gb.

Last edited by gb_astro; 09-01-2011 at 01:26 PM.
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Old 09-01-2011, 02:19 PM
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Russian (Stephen)
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Hi Guys , here is a pic of the mirror after they polished it. !!!!!!!!!!!!!!!!!!
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  #9  
Old 09-01-2011, 02:27 PM
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astroron (Ron)
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Send the whole thing back and ask for another one or a refund,that is just not good enough from Andrews who are normally very good service
Cheers
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  #10  
Old 09-01-2011, 10:22 PM
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Hi Stephen,

Sorry to hear about your debacle....blooody frustrating to say the least. I would definitely ask for a replacement/exchange or refund. Lee is a reasonable man and generally provides good service so hopefully things will get sorted for ya.

The photo want load for me, but what I can see, it definitely doesn't look right. In terms of being polished, seem odd. The only way it should be cleaned is using distilled/deminalised water and a few drops of detergement. If they've polished it, it would mean they've had to rub on it....sounds scary.

norm
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Old 10-01-2011, 05:57 AM
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asimov (John)
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There's no way Lee & his crew would 'polish' a mirror that has an aluminized surface. Some one's using the wrong terminology here I think.
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  #12  
Old 10-01-2011, 06:50 AM
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I am not sure a light scratch would affect performance too much but as mentioned that is not the point when you buy new. You should not have to compromise.

I think generally it is a good thing for the overall market of Chinese made goods if the pressure is applied to make them meet Australaian consumer expectations. They tend to get away with putting a lot of inferior goods out to the consumer's detriment.

I have a Chinese made backup generator and it is quite unreliable. It "seemed" a deal at $1995 for a 3.3 inverter type generator. Far better to buy the Honda for $3400 and it would be trouble free for years.

Those who sell Chinese goods need to be able to put pressure back on their suppliers to meet our standards or make the supplier take the loss rather than the retailer taking the loss.

Greg.
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  #13  
Old 10-01-2011, 07:44 PM
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Russian (Stephen)
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Hi all ,
to answer what john said about them not polishing the mirror, I can't say for sure who i was talking to but he said that they had "Polished" the mirror , which I thought was odd as every thing i have read, is you only clean a mirror as the last resort .

I asked about the optical coating on the mirror but i can't remember for sure what he said .

Steve
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  #14  
Old 10-01-2011, 08:06 PM
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Peter Ward
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One or even a few small sleeks on a mirror coating are hardly fatal to a reflective optic, they have no effect on performance and can be ignored.

I am surprised you were not advised of that. ( I have seen the occasional small sleek on new $45K scope mirrors...the optics are still effectively perfect and the sleeks go away after the next re-coat..)

Trying to polish out coating sleeks is just plain dumb. Aluminium is just too soft for that.

That mirror now needs re-coating or replacement IMHO.
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