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Refurbished CR-6

Started by 1953, 04/21/2007 06:03AM
Posted 04/21/2007 06:03AM Opening Post
Here's a "refurbished" CR-6. I got this scope as part of a deal that went bad. It took me almost a month to get it after payment (for which I was billed twice, but that's another story.). What attracted me to this particular instrument was the owners claim that it had been "hand selected by Markus for a Chormacor O1", which I happened to have.

When I finally did get it, the scope was in terrible shape. First the tube has some sort of sticky material all over the dew shield and lens cell and the tube was badly scratched up. More importantly, the lens looked like it had been thru Katrina. There were water marks on ALL surfaces, including the interior surfaces. And they were not spots...there was puddling & pooling.

Well, I've been around the block in this hobby and have disassembled and cleaned many an objective up to my 8" Brandt. It's not that difficult for an achromat but this was something else. I honestly felt the lens was toast. How could the coatings have possibly survived and the glass not be etched!

Well, when I took the lens out of its cell. I was pleasantly surprised to see that the opticians had marked the lens for proper alignment of the elements. Inspection of the lens surfaces showed residue and deposited material. Ugh. I then completely immersed each element into a cleaning solution of warm distilled water and a few drops of detergent. Using cotton swabs I gently swabbed each surface. The deposits came quickly off. Next they were rinsed in a distilled water and denatured alcohol solution then rinsed again with a 90% denatured alcohol solution and air dried. Except for some smudges, they looked really very good. I next cleaned them up with cotton swabs and the moisture from my breath.

Careful examination under bright light and various viewing angles showed there was some minor sleeking of the coatings but they were intact. There were also some minor cleaning swirl marks that I left alone as experience has shown they don't matter at all and disappear when viewed at anything but high angles to the surface.

I carefully reassembled the lens and lowered the cell over it. I took the opportunity to shim the lens against the cell with paper as it seemed a bit too loose. Finally I fitted the "O" ring and screwed in the retainer while gently tapping the cell to center the elements.

Done! And it looked very good, still some sleeks but that's ok.

I cleaned up the sticky tube with acetone, but I've yet to refinish it.

I've reassembled it but have not done a collimation yet.

Performance wise, it's very good. Indeed it is slightly under-corrected with a smooth figure and no obvious zones. False color...oh my yes. It is after all a "fast" achromat. But it was really very sharp.

Inserting the Chromacor really brought the assembly to a fine state. Without any tweaking of the set up, false color was reduced considerably. Yes it was still there but subjectively about 1/4th the amount and similar to my old AP 130 F6. However, the image was noticeably sharper and fully the equal (except for color) of the TEC 6 in the picture's background.

But more tweaking is necessary. The image shows the classic signs of a slightly mis-adjusted Chromacor, like off axis color and unequal color around bright objects (red on one side and blue on the other side of Jupiter for example.)

But that just means things will get better!

Hope I have not bored you guys but this has been an interesting experience.

Jeff



Attached Image:

1953's attachment for post 36766

"Don't sweat the petty things and don't pet the sweaty things" 8O
Posted 04/21/2007 06:04AM #1
Here's another image.

Jeff

Attached Image:

1953's attachment for post 113425

"Don't sweat the petty things and don't pet the sweaty things" 8O
Posted 04/22/2007 12:41AM #2
Jeff,
Thankyou for sharing and taking care of the old girl-Telecope. I have one of these babies, it not an APO but it has it's place in the hobbie. And anybody who would mistreat one of these, should be horse whiped... >sad
Treat her with kindness grin .

bll

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