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AP 6" f12 Super Planetary Lens Issue

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#1 stephenws

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Posted 26 January 2020 - 09:38 AM

I recently acquired a 1986/87 Astro-Physics 6" f12 Super Planetary which has seen several years of neglect. The tube and focuser are undamaged and servicable, but the lens has suffered a bit. The front surface of the lens has a "haze" which does not clean off. I'm afraid the coating has deteriorated over the years. Fortunately there are no significant scratches. The back of the lens had some condensation spotting which cleaned off easily.

 

I made some initial inquiries concerning the lens with George, from Astro-Physics, and apparently Roland is sometimes willing to polish and refigure a lens back to new condition, although at a significant cost - approximately $1500.

 

At this point I only have $500 invested in the scope and I'm wondering if it's worthwhile to get the lens reworked by AP? The lens haze is only visible at certain angles to the light. Will this really affect what I see through the scope, or is it just a cosmetic issue? Will it affect resolution and/or contrast of planetary details?

 

Any thoughts?

 

I've attached a photo which somewhat shows the haze.

 

 

 

 

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#2 Terra Nova

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Posted 26 January 2020 - 09:48 AM

For your initial $500 investment, it is definitely worth sending it off to Roland at AP and having it cleaned up etc.


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#3 George N

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Posted 26 January 2020 - 10:07 AM

We have the same scope at Kopernik Observatory (https://www.kopernik.org/).

 

While it never had 'haze' issues like shown in this photo - the lens surface was far from pristine. Our big problem - the cork spacer fell out and down the tube! Roland said to not use it until he had repaired it. He advised sending just the lens, not the entire telescope. He disassembled, cleaned, re-oiled, adjusted the lenses in the cell -- it all happened pretty quickly. I don't know the cost.

 

Personally - it this was my scope - I'd have Roland repair it. You will love the result - and your telescope will have a much higher re-sale value.


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#4 ccwemyss

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Posted 26 January 2020 - 10:07 AM

My 6" f9 from the same period had the same issue. I don't think it is neglect. Mine was stored indoors and only went out on the best nights because the 706 mount and pedestal were such a hassle to use. It was never cleaned (never needed it) before George instructed me to do so as a condition for sending it in. They said it was a result of dewing, but I only had the scope dew up maybe two or three times. I've seen several since then from the same period with the same problem, but have plenty of other scopes that are far older and have had far worse treatment that haven't had coating damage. I think they just had a coater doing bad work around then. 

 

That was a few years ago, and it was only $500 to have the coating polished off. But they said it would be another $1000 to also have it recoated, although it wouldn't significantly affect the views. So I sent it in, and it came back clear. It's back to giving stunning views.

 

These pre-Starfire triplets may not be as flawless for color and flatness as later ones that were responding to the needs of imagers, but for visual use they are still among the best optics ever produced for the amateur market. My f9 is incredible, and an f12 would be closer to the performance of the later designs, other than in f-ratio. Consider that the 6" APM triplets are $13,000 when available, and by comparison, $2000 is a steal.

 

Chip W. 


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#5 pbealo

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Posted 26 January 2020 - 10:11 AM

I second Terra's motion.


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#6 TG

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Posted 26 January 2020 - 12:47 PM

A-P will probably offer to polish off the coating a with a refigure and not offer to recoat as that involves heating the elements made of irreplaceable glass. An unpolished front surface will lose 4% light, no big deal since there are only 2 and the second one's coatings are presumably intact.
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#7 stephenws

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Posted 26 January 2020 - 01:27 PM

Thanks for the input.

 

I'll be contacting George at AP tomorrow to see if Roland can work my lens into his schedule.



#8 Jeff B

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Posted 26 January 2020 - 01:48 PM

Absolutely send it back to AP for the refurb.  The price is most definitely worth it.

 

Shoot, if you don't want to do that, send me a PM and I'll take it off of your hands.

 

Now, from my own personal experiences with AP over the decades, when Roland gets the lens, he will set it up and have a look at the overall figure.  He will proceed to do the repolish, but, please understand, that is actually a re-figuring of the lens.  And Roland does this to a higher standard than he did in the 80's as he now uses the interferometer.  And yes, ignore the urge for a new coating, as it indeed would only give maybe 2-3% more light over the old MgFl coatings...and as the glass is chemically very inert, you won't have to worry about the stoopid coatings anymore.

 

Finally, when Roland reassemble the lens, he will use the interferometer to give it the best performance as well as using the latest spacing oil.  

 

So, the lens you get back will be better than 1980's brand new and last well beyond your life span.

 

Other than that, sell it to me.  grin.gif

 

Jeff


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#9 starman876

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Posted 28 January 2020 - 01:09 PM

Get it fixed.  Wonderful scope.  For the money you end up spending you will have a wonderful performer and still be cheaper than any 6" APO that comes out of China.  


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#10 photiost

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Posted 29 January 2020 - 09:18 AM

Great find !!

 

This is an amazing instrument and @ $2000 it is worth every penny.

 

waytogo.gif


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#11 SteveGR

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Posted 29 January 2020 - 12:19 PM

Get it fixed.  Wonderful scope.  For the money you end up spending you will have a wonderful performer and still be cheaper than any 6" APO that comes out of China.  

Not to mention that you won't find many 6" F12 scopes coming out of China. smile.gif 

 

It will also probably come back performing better than it ever did when new.  Sigh.  Why can't I ever run across stuff like this?  Too busy dropping toast butter side down, I guess.


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#12 starman876

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Posted 29 January 2020 - 04:01 PM

Not to mention that you won't find many 6" F12 scopes coming out of China. smile.gif

 

It will also probably come back performing better than it ever did when new.  Sigh.  Why can't I ever run across stuff like this?  Too busy dropping toast butter side down, I guess.

Butter the toast after you drop it.



#13 SteveGR

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Posted 29 January 2020 - 04:22 PM

Butter the toast after you drop it.

I'm no physicist but I think that would violate causality.  The toast must be buttered before it can unluckily be dropped.  There might be some wacky quantum stuff going on in the background though.


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#14 macdonjh

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Posted 29 January 2020 - 04:42 PM

I'm no physicist but I think that would violate causality.  The toast must be buttered before it can unluckily be dropped.  There might be some wacky quantum stuff going on in the background though.

Wouldn't quantum entanglement dictate the toast landing on both sides, whether or not either side is buttered?  Of course, the piece of toast which lands buttered side up is always on the other side of the universe.



#15 Toddeo

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Posted 29 January 2020 - 04:51 PM

Whenever I drop toast- it lands on it's edge!wink.gif



#16 clamchip

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Posted 29 January 2020 - 06:59 PM

I don't know but I'm sure glad when my 14.5 inch mirror came loose from 

my scope it didn't land butter side down!

 

Robert


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#17 starman876

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Posted 30 January 2020 - 08:49 AM

One time a 6" lens fell on my head when it came down from the shelf.   The lens was fine.  Not so good for my pride. 



#18 starman876

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Posted 30 January 2020 - 08:54 AM

Thanks for the input.

 

I'll be contacting George at AP tomorrow to see if Roland can work my lens into his schedule.

Any luck with AP?   Roland will retire one of these days. 



#19 Jeff B

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Posted 02 February 2020 - 10:29 AM

Any luck with AP?   Roland will retire one of these days. 

Yeah, what have you decided Stephen?

 

Did you get an RA number from George?

 

Jeff



#20 Richard Whalen

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Posted 03 February 2020 - 03:33 PM

If you do get it recoated the coatings will be much better than the orginal coatings were when new. I would go with whatever Roland recommends.



#21 SteveGR

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Posted 03 February 2020 - 03:50 PM

This is kind of a tangent, but do we know what type of glass Roland was using at the time?  I know some of the types he used aren't available anymore, and would this have been after the "NASA glass"?



#22 ccwemyss

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Posted 03 February 2020 - 08:08 PM

I think the NASA glass went into a pre-Starfire 6" f8 design. I don't believe it was in the f9 or longer (as I recall from my conversations with Roland around then, the point of it was that it enabled a faster system).

 

Chip W. 



#23 Jeff B

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Posted 03 February 2020 - 10:31 PM

Chip:

 

Roland used the "NASA" glass in many of the pre-Starfire  5" & 6" scopes including the 6" F12 design of the OP but it is difficult to know exactly which ones.  As far as I know, if he signed the edge of he lens, it had the NASA stuff, but that does not preclude it being in other scopes too.  For example, the early 5" F6's I got from him all had the NASA glass but were unsigned as was the one-off 7" F15 I had, but did indeed have the good stuff (I often wonder where that lens ended up)  

 

I don't think Roland kept consistent records in that regards, but you never know until you call them up.  

 

The NASA glasses were special melts that NASA had requested, never used, and went to surplus where years later Roland somehow found some.  He bought an entire batch (he even told me there was another batch around but could not locate it.).  What's special about the glass is that the partials are slightly better than the stock short flint but, more importantly, very well documented and very pure with no internal strain over a very large area/volume. 

 

That's my experience and understanding.  Now even if it's not "NASA" glass, Roland would polish it to get the best performance he can.  I have a one off 6" F10 he redid for me about 7 or 8 years ago and it's an excellent performer, though with a tad of "CA".  No coatings either and I would never know it.  

 

Jeff

 

 

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#24 ccwemyss

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Posted 04 February 2020 - 08:26 AM

Thanks for clarifying. I was going on my memory of conversations from over 30 years ago. You're right that there wasn't a lot of documentation back then. They were focused on just getting the orders filled. Although I will give them credit that when I asked for the RA on my objective to have the coating polished off, they wanted to know if they still had the correct address for me from when I originally bought it. 

 

Mine is signed, but I don't think it has the NASA glass. However, in the time I spent waiting for it (nearly a year), I repeatedly told him that he should be signing his lenses because they would eventually have the kind of reputation that the Clarks did.

 

Is there an independent way to tell whether a lens has the NASA glass?

 

Chip W. 



#25 Terra Nova

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Posted 04 February 2020 - 03:12 PM

Brian G. (Mustgobigger) had an AP 6” F12 Planet Killer. He sold it to Tom T. (Turk), who later sold it to someone else. I’m not certain if it had NASA glass or not? You will find it discussed here in this forum in the 2012-2015 period. 

 

Here’s one, I’m not sure if it is the same one:

 

https://astromart.co...tary-nasa-glass

 

Note that at the bottom it states:

A little known fact about the early 6" f/12 Super Planetary scopes is that they also used the "NASA" glass. The later models (I presume the NASA flint glass ran out) used K-7 crown and KzFSN-4 flint glass.”

 

Edit! The following post (linked below) corroborates the NASA glass pedigree of the scope I mentioned above.

 

https://www.cloudyni...history-serial/

 

See post No. 2 where Brian (Mustgobigger) states:

 

Up to 80 was the NASA glass run #1. Ihave 72 and it was sent out for coatings in october
of 1989. This i got direct from AP by phone a few months back
.”

 

And another AP 6” F12 with NASA glass is discussed here:

 

https://www.cloudyni...t-happy-ending/
 

 

 


Edited by Terra Nova, 04 February 2020 - 03:21 PM.



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