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Old 05-12-2007, 12:36 AM
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Merlin66 (Ken)
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The tale of a PST

I thought with all the clouds around here, broken occasionally by glints of sunshine, that I could add to my "enjoyment" by buying a Cornado PST. It seemed to fit well with the other spectroscope stuff I'm still learning to do.
Looking at the current prices I thought a good secondhand one would be the way to go....... that's where the story starts.
Being based in the UK and having just found the Customs guys over here can hit you HARD for import duty ( think in terms of 40% of the declared value!!!) I decided to find one locally. After a bit of haggling I found one at a reasonable price and looked forward to its receipt. About a week later ( never mind the "guaranteed delivery tomorrow") it arrived. Beautiful case, beautiful scope, clean and complete with the 12mm eyepiece. Believe it or not there was actually a clear patch of sky and the sun was shining through.... no instruction manual but pretty self evident as to what to do; line it up adjust the focus knob...not much so far.. Ah the filter needs to be "tuned" also ( to get the Ha defined) quick turn of the knurlled section on the beautiful gold anodised tube.... still not much... infact the edge of the image of the Sun looks a bit fuzzy and there's a trace of a double (?) image. Another go round of the knobs, change eyepieces to a "known" TV Plossl... still no improvement, certainly no promenaces or any other surface detail. I know the Sun is pretty quiet at the moment but there should be something, somewhere... The clouds came over and put me out of my misery.
As I lifted the scope of the tripod I looked at the front element; it's a 40mm achromat ( I believe) suitably coated to act as an "Energy Rejection Filter", I've heard its a bit like having a broad band Ha filter to minimise the heat getting into the sensitive monochromator filter mechanism at the eyepiece end of the tube. The golden colour masked a dirty brown ring which almost cover half the aperture. The exterior looked clean and crisp so the marking must be on the inside.... Damn. Well I've stripped a few lenses in my time maybe I'll have to take the front element out and clean the back.
About now something rang in the back of my mind, something I'd come across during the Google search on PST's " rusting ERF" Was this "rust"? ( It's not really rust, but certainly looks like it! It's actually the coating of the ERF lens breaking down.) Couldn't find any pictures on the Cloudy night forum, which lists the various serial numbers of the affected scopes ( apparently there was a "batch" of ERF's which had a defective coating; Cornado/ Meade have now acknowledged the problem, BUT repairs are limited to the original buyer with his receipt).
Sounded like the one I had was suffering from "rust".... OK, what about a replacement ERF, they must be available, let's check it out. Whoooops, bad decision. ALL the local distributers must have heard me coming and the prices varied from $250 to $600 Aus equivalent!!!
No real option but to go back to the seller and tell him the news and try and get the money refunded.... Disbelief, distrust, disturbed " never heard of this 'rust' thing", " It was OK when I shipped it"; "You must have damaged it while setting it up" As Billy Connally would say " It was the big yin that did it" Anything/ anyone other than me...
It took a lot of talking, various photos ( see attached...now you too can recognise a 'rusty' PST) and a couple of extracts from the Cloudy Night listing to convince him of the problem. Another week later I had my money back ( thank you!) and he was shaking his head ( he had bought it third hand and obviously has no 'original' receipts to help)
What to do now? I still liked the idea of a PST just had to find one which was OK. Back to the Buy and Sell lists....
Found one, good price, sent photo of the rust and asked for confirmation of a 'rust free' ERF; by email the seller claimed "there was no rust on the ERF"...
I couldn't help myself and guaranteed to buy IF he sent a photo of the ERF to ensure it was OK ( By now I was an expert, and know all the suspect serial numbers etc etc!).... deal fell through when he finally acknowledged that "well, maybe, just a little, there is SOME marking on the back of the gold ERF"

Two strikes down...time to give up?? No, not me the maschocist....
Here we go again; "yes its still for sale", " no, there's no 'rust' I bought it new myself late last year and only used it on a Sunday before going to Church"
OK I heard myself saying, send a photo and I'll send the money....
SILENCE.... another email, SILENCE Oh Oh Finally I got an email saying he had "carefully studied the ERF, and well, maybe there was faint markings at the edge" BUT as he still had the original receipts he was going to get it repaired - he thanked me for pointing out the problem - life goes on.

After a few weeks I gave up trying to find a 'rust' free PST ( Is this boring you yet?)
Well late last week, guess what, the guy came back to me saying he had had the PST repaired and had new recepits and documentation " Looks great with its new BLUE coating" better still the price was reduced "due to the hassles".

Just picked it up this morning.... looks 100% beautiful case, beautiful gold anodised tube, clean and complete with the 12mm eyepiece... isn't this where I started!!!
So after almost three months of "experience" I think I'm going to be happy; just need a bit of clear sky....
to be continued.........
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  #2  
Old 05-12-2007, 05:44 AM
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iceman (Mike)
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Wow, what a story. Definitely a cautionary tale! I was thinking about trying to pick up a cheap 2nd hand PST but was also worry about this coating problem I'd heard about.

Thanks for the story! What is the next installment?
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Old 05-12-2007, 01:03 PM
casstony
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That sure is one nasty looking objective lens. I sent mine to Coronado as soon as I heard they might be getting taken over by Meade, but my objective was only starting to go bad - nothing like your picture. Great service from Coronado, 3 week turn around from Australia. If Meade are only covering the original purchaser it will be difficult to sell unmodified scopes.
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Old 05-12-2007, 03:23 PM
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that looks plain nasty ken .. is this a problem with all of the scopes ?
and will the repaired scope do the same thing .
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Old 05-12-2007, 04:17 PM
casstony
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The original design had the ERF built into the objective lens while the updated design moves the ERF to the eyepiece end of the scope. The original objectives were opaque and aqua coloured, while the later objectives are transparent with a blue tint. While the original design concept was better, I'm not aware of any failures of the newer objectives. My impression is that many (if not most) of the original objectives developed problems.
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Old 05-12-2007, 04:37 PM
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citivolus (Ric)
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Very interesting. That objective sure looks nasty!

Do they provide any kind of lifetime estimate for the PST?
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Old 05-12-2007, 06:57 PM
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Merlin66 (Ken)
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ERF filters -PST

Casstony,
The new "upgraded" ERF is a blue colour whereas the original was a gold colour. It looks like ALL the gold ones may eventually suffer the same fate so I think their life could be limited. The complete front ERF element was replaced on the one I got but all the other rear elements were unchanged. There no "other" improvements on the monochromatic filters or the small blocking filter at the eyepiece.

According to Maurice Gavin who has tested both versions the blue coating gives a much brighter image and his exposures had to be significantly reduced.
I do see the the current ads mention "improved filters" but don't know what this means; I'd assumed it was marketing hype to overcome the customer concerns with the original.
Still piddling down at the moment, typical!!
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Old 05-12-2007, 07:51 PM
casstony
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Merlin,
back in mid 2006 I asked Rikki from Coronado if I could send in the objective without the rest of the scope. I was told the entire scope had to be sent as they would make changes at the eyepiece end when they replaced the opaque objective with the transparent one. My original objective was aqua colored - maybe they look gold colored after a lot of degradation?
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Old 05-12-2007, 08:10 PM
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Merlin66 (Ken)
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Pst

My understanding was that a change of ERF only affected the coatings and light transmission; I'm aware that the objective may have a slightly diffferent focal length and this needs to be compensated by "minor adjustment" of the monochromater, not replacement. Could be wrong. The main body with the serial tag doesn't look like its been touched? I'd be interested in any additional info if it's available.
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Old 05-12-2007, 10:01 PM
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seeker372011 (Narayan)
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Quote:
Originally Posted by Merlin66 View Post
Casstony,
. It looks like ALL the gold ones may eventually suffer the same fate so I think their life could be limited. !
oh man that is not what I wanted to hear..I ve alrready sent mine back once for the repair
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Old 05-12-2007, 11:10 PM
casstony
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I had a look on cloudynights and found this thread that explains the re-design: http://www.cloudynights.com/ubbthrea.../o/all/fpart/1

Apparently the front filter is an ITF(induced transmission filter) not an ERF. Here's part of the thread:

"The "breakdown" or rust colored appearance that has been seen on front objectives of some PSTs is a result of degradation of the ITF coating. Our ITF's are being supplied by an outside source. Upon arrival at Coronado they were cemented and assembled into the PST objective. Unfortunately, when improperly handled, meaning too much time before cementing whether at the vendor, Coronado or both degradation began. This degradation could not be seen during the assembly process or in our field testing prior to shipment. The coating started to visibly degrade a few months after assembly. Because this problem does not affect safety (only performance) and does not affect all PSTs, Coronado is repairing the affected units rather than issuing a general recall.

Our current procedure is to use another style of the ITF and locate it further down in the optical tube. These units will look different as the front objective will be clear, but neither safety nor performance are adversely affected by this change."
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Old 06-12-2007, 06:50 PM
rumples riot
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Yep the blue objectives are the better ones, a lot of the gold objectives have been affected by rust issues. The new design reduces the stress on the objective and gives a much sharper image.

The purchase of a second hand solar scope requires quite a lot of experience and help from the seller. When I sold my PST (blue objective) and SM40 filter I made sure that the buyer was one hundred percent happy with the way I had treated the unit, that the unit was defect free and it was working as it should.

If you are intending to buy one, it is recommended that you do all the appropriate research before buying. If you know of someone who owns a solar scope of any description get them to go with you and look at the scope. Solar scopes are fragile and very dangerous if damaged and more so in the hands of someone who is unfamiliar with how they work. The rust issue just makes it defective (not dangerous) but just highlights how carefully one should be inspected.

Glad it worked out for you, but this should serve as a warning for those buying solar scopes.
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Old 06-12-2007, 07:12 PM
CoombellKid
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Actually from what the distributer have been telling me, the repair to the
so called blue objective you have a slight loss in contrast. Part of the reason
I haven't sent mine in for repair. Although lately I have been thinking about
it as I hear Meade is on shaky ground.

regards,CS
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