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01-10-2013, 02:57 PM   #16
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QuoteOriginally posted by alphanerd Quote
The included picture was taken at 800mm on a full-frame camera (D600), though it may have been cropped. That's more like 500-550mm on a crop camera. Pentax does make a FA 600mm f4 lens. Availability is something of an issue.

FA* 600/4 ED [IF]
It was cropped to 7500mm in FF-equivalent.

Last edited by ElJamoquio; 01-10-2013 at 03:03 PM.
01-10-2013, 03:13 PM   #17

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QuoteOriginally posted by ElJamoquio Quote
Anybody have any leads on a 7500mm lens? It'd be nice if it was F/4 or faster.


That works out to requiring a front objective with a clear aperture of a tad over 6 feet.
Better include a 5 ton flatbed truck in the purchase price as well.
01-10-2013, 03:44 PM   #18
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I was hoping to use a trailer, and borrow your truck.
01-10-2013, 03:47 PM   #19
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QuoteOriginally posted by GabrielFFontes Quote
SDM or screwdrive?
I have a couple here dusting in my closet.
I would think you'd need some type of kickstarter on it.

I'll offer you $500 for the one with SDM.

01-10-2013, 08:56 PM   #20
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Pentax makes some pretty nice telescopes. They're manual focus of coarse.

Pentax Eyepieces and Telescopes

01-10-2013, 09:21 PM   #21
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QuoteOriginally posted by TopherTheME Quote
Pentax makes some pretty nice telescopes. They're manual focus of coarse.
I wouldn't think it would meet the F4 requirement.
01-10-2013, 09:47 PM   #22
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I have a Pentax 100 SDUF II which is F4 but it's the eyepiece that changes the focal length and not necessarily the scope. I think mine is 400mm without the eyepiece.
01-10-2013, 09:50 PM   #23
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45 years ago I had a terrestrial telescope made in Japan- maybe 750 mm
On a hill it was pretty good. 2miles /4 km or so .
I recall the air currents were a worry.
The worst part was the wooden tripod with wing nuts, it was just hopeless

01-11-2013, 07:26 AM   #24
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QuoteOriginally posted by Bob from Aus Quote
I think you can purchase some 5 tonne telescopes that is up to the job. Not very portable.
Those tend to be on the slow side, though. MFD also not ideal for a general walk-around lens!

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