6 inch refractor

[david booth]

for sale 6 inch 152mm f 11 fruorite apo refractor ota only $3200.00
(http://www.cloudynights.com/classifieds/showproduct.php?product=87267&sort=&cat=9&page=4)

[brian nordstrom]

:shrug: David the link is for an ES 80ED ?? , but where was the lense made ? if you know .
Thanks
Brian.

[johnnyt123]

Hi David.

Who is the maker of this scope?
And as Brian asked, who made the lense and when was it made.
Fluorite glass can deteriorate over time.

Thanks

John

[bert]

It's a Barry Adcock built scope.

I have one the same, and it is superb optically.

[brian nordstrom]

:thumbsup: Thanks Brent , Fluorite is not an easy glass ( crystal ) to grind and figure , I bet its a great performer on the planets .
Hope its still for sale when I get settled down south , I will think seriously about this OTA . David , any chance of a shot of the Objective and focuser arrangements.
Brian.

[david booth]

yes it is a barry adcock built scope and it is perfect on planets only selling to fund other projects i also have a 5 inch of the same

[pgc hunter]

Quick question.... how much do the individual components weigh, e.g Tube assembly, mount etc?

[johnt]

Can you or someone elaborate on the comment about fluorite glass deteriorating over time? How serious would that sort of problem be?

Also, another question, from some other photos I have seen of the same scope type, it seems to be the original mount that originally came with the scope??

But, as the ad stated, only the OTA is being offered, but not the mount, so I guess that also makes the question asked about the weight of the mount irrelevant.

[bratislav]

As far as I know Barry never used Fluorite (CaF2). Scope in question most likely used Ohara FPL glass, from memory his 6" doublets were NSL36/FPL52 combination. BTW, FPL glass is vastly more durable than Fluorite.

[Astromelb]

I have had three of Barry Adcock's hand crafted refractors, including the first fluorite that he made, also using O'Hara's fluorite glass, which was also a 6 inch f11.

His fluorite units all used the fluorite in the rear element, as this was Barry's advice when agreeing the tech spec on all three scopes. He has also made non fluorites as well in the past.

The entire three telescopes were all fully hand crafted, with hand crafted (sand cast) aluminium lens and focuser cells, plus a hand crafted focuser using a hand crafted R&P. The lenses were all uncoated, Barry never coated any of his lenses. Trust this assists.

[david booth]

the tube weight is 9.5 kilos, the lens is FPL/53 .

[brian nordstrom]

:) Thanks David , this OTA will fit nicely on an HEQ5 with a 7 foot pier.,
Thanks , 21 lbs .
Sweet ..
Brian

[UniPol]

What is its Strehl ratio?

[Astromelb]

This unit is an oil spaced doublet with a Crown element in the front and a fluorite element at the rear, as was Barry Adcock's standard practice.
The optics are uncoated, and the glass (both elements) were sourced from O'Hara.

My own personal unit I personally measured out at 1/20 wave P/V, I would expect this unit to be similar upon final assembly.

Barry's 6 inch units were quite capable. This unit (as my own) used a f11 design, and thereby a 1700mm focal length. As such it requires a strong and robust foundation. I used my unit on an ASA DDM 60 Equatorial mount, and thereby squeezed the best out of the optic, as the mount foundations for any long focal length refractor is crucial.

A larger Eq mount with a higher than standard capacity is recommended. Short focal length 6 inch units such as 1200mm can use a smaller mount, sure. But this telescope is a 1700mm focal length, and those that know longer focal length units will know that - as example - Unipol has a 4 inch Unitron with it's f1500mm, and well knows this needs a higher capacity mount than any standard 4 inch f10.

I have had three Barry Adcock refractors and can vouch for their performance and quality, although these days I have only one unit left as I have moved on to OK4 triplets, and also Carl Zeiss triplet refractors, which those that know these systems will well know why I have done this.

For a lower cost solution than the exotica level LZOS refractors the Adcock units are a very capable opportunity.

[johnt]

"Quoted text deleted"

Yes, thank you AstroMelb for the useful info on these refractors, very interesting. There is no doubt that these were obviously designed very well. The question remains, how well has this example survived over time? Does it still perform as it was first built? My opinion is that some clear and confident details by the seller regarding the unit being sold would certainly go a long way in giving more confidence to a potential buyer.

[LewisM]

Now, who's selling WHAT now here? Is it David selling it, or Cris, or both, or seperately in the one thread?????

Turning into a dealer advert almost.

[johnt]

David is Selling it, and Chris was just giving information on it based on his knowledge of the maker. With the lack of information given on this telescope being sold, and lack of information on the web, I think any information, from any source is good to get, ...especially if someone is thinking about spending the money to buy it.