Massive $33,500 2450mm f/8 NASA lens surfaces on eBay

Not sure why it has to weigh so much. I have a 12" f/10 SC telescope that's 3048mm and it barely weighs in at 40lbs for the OTA.

Does it say 'NASA' anywhere in your doc's?....;))

Also, in outer space, weight is not a factor....;))
(at launch it would be however)

OTOH, such a weight does match one of my pet-peeves perfectly:

The best anti-theft deterrant is....weight.
(this argument starts at heavy rucksacks, if only because the thieve can never run as fast away, with it, as you can follow him, without....:))

I realize by your smilie icons you are half joking but nothing you said makes any sense.
1. Not sure why saying NASA on any of this lens documents would have anything to do with the weight.
2. This lens was not used in space. It was used for ground based tracking of launches.
3. Not really an issue on a secure government installation like KSC.
Oh.... ;-)

Are you sure about that LF resolution?
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Quote:
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70.) 1 x High End reconnaissance lens 4/457mm for 4x5" ( 350 lppmm ) covers 8x10 with high resolution ( 100 lppmm )
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(from the seller's second, previous auction (seems few folks here dug up that extra info, in the text down there, no comments on my earlier triple-posting in that regard....;)))

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And there is a 'hybrid' kind of optics that doesn't follow the rules either: slit-exposing panorama lenses, like the Noblar 50mm/f2.8.
(require less circle of coverage, cq only for the height of 120/220, 56mm (plus a few mm for the shift versions))

JPEG and PDF are open and ubiquitous enough that I suspect our descendants a century from now will still be able to read them if the data can be salvaged from the physical media somehow (a big if, I know). I wouldn't be so optimistic about any other image format, though, and good luck with that Lightroom archive of yours.

57mmx57mm? I thought it was 70mm film roughly 4x the area of 35mm film? Or am I incorrectly assuming again that you can infer ANYTHING about the actual sensitivity area of a piece of film by it's name. 0.50x crop gives it 1225mm FF.

A large image circle is an advantage, not a disadvantage. If you put a full frame sensor behind this lens, it will give you viewing angle as a 2540mm lens (which it is). If you use a 4/3 sensor, the viewing angle will be the same as a 5080mm lens on full frame.

70 mm is the width of the film, with (as in Hasselblad) perforations on both sides, leading to 57x57 or 56x56 mm.

cstogian, These scopes all focus at infinity. telescope photography is about diffraction. Aperture and focal length are less relevant than the physical aperture assuming the scope is built bright enough to avoid diffraction. 2540mm f8 is not diffraction limited. 5080mm FF-EQ f8 is diffraction central. However, if you focused down the light 2540mm f2 for a 4/3 sensor is not.

2450mm f8 for 645 sized MF (closest I could find) is diffraction limited at a resoultion past 140 mp or so

2450 f8 for m43 sized sensor is diffraction limited at a resolution past 12mp or so.

This lens is good enough to require a larger format than 4/3rds to be utilized effectively even when the subject (say a distant star) doesn't fill the frame.

Thanks for your informative posts, I admit telescopes are not my specialty.
If you are shooting something that cannot be magnified, like a star, then I get the point you made earlier, it's all about light gathering. If you are shooting a planet, the moon or some terrestrial target, however, magnification might be important, wouldn't that be the case?
You are right about diffraction being a limiting factor as well. However, I might be wrong but I don't understand diffraction to be a hard limit, you can still get sharp images from much smaller sensors with slow lenses.

you can get sharp images from smaller sensors with slower lenses... within the limits of diffraction. Diffraction results from the physical aperture size (format independent. Best explained by "equivalent aperture" of your lens for whatever format) ONLY. You would think focal length is involved but it cancels out with essentially the crop. Diffraction also involves resolution. m43 sensors are 1/4 the size of FF but the pixels are fairly large since the sensor is 16mp. This helps with diffraction as well.

You've heard people discuss increased focusing requirements on higher resolution sensors. This has a lot to do with diffraction. There is less wiggle room as you approach the diffraction limit.

In FF terms (or equivalent aperture which is fstop*crop) diffraction occurs roughly at
F16 - 11.8 MP
F11 - 25.1 MP
F8 - 47.5 MP
f5.6 - 97 MP
f4 - 190 MP

That's the resolution the physical aperture permits. m43 has a 2x crop so it's 16mp sensor is good no smaller than around f7

But also as you said diffraction is not a hard limit. It's effects will start to appear at that level and effectively limit resolution. This means detail from one pixel starts to spill into it's neighbors. From a print perspective you don't need the last shred of resolution so shooting at higher apertures, while it may compromise some of the smallest detail, does not change things beyond acting like a ND filter.

m43 cameras shot F8 in front of a 16mp sensor will show diffraction at the finest of detail levels but only to a very small extent. If Panasonic/Olympus ever release say a 24mp sensor though, f8 shots will be much more difficult to focus at the pixel detail level. Printed with lower resolution this shouldn't change anything but viewed at the pixel level diffraction would be visible.

This is why cell phones need fast fstops. They are high enough resolution and small enough sensor wise to push diffraction. Getting a 20mp image from a tiny sensor still requires around f12 eqiv.

Diffraction is a hard limit when you exceed the point where there is no benefit to smaller pixels. Beyond this point, adding more pixels to the same size sensor has zero noticeable effect on the output resolution. This occurs at roughly 4x the "diffraction limit" resolution. Beyond that point, diffraction stops being gradual and there simply isn't any more detail to pull. For example a 16mp 1/3" cell phone sensor with an ~f4 lens is so far into diffraction that increasing the resolution at that size further would give zero added detail. More pixels will simply provide completely indistinguishable (redundant) data to their neighbors. The diffraction limit would commonly be 4mp for a 1/3" f4.0 lens but at 4x that resolution diffraction is a hard limit.

Hard limit for m43 f8 is at about 48mp. You can see olympus struggling with this on their ~64mp high res mode. Glass is not 100% perfect but even if it was the aperture will not magically increase by shifting the sensor. There is a limit.

Interesting points, although I do not understand it completely. I would love to see an article on diffraction, with many illustrations and tests. On my old Olympus E3 (10 megapixels) with an apo Sigma 150 macro f/11 is OK, but f/13 clearly is worse thanks to diffraction. F/16 gives more depth of field but in fact is worthless.

I think this is a pretty great article on diffraction:
http://www.cambridgeincolour.com/tutorials/diffraction-photography.htm
You can play around with their calculator at the end too. Set it to "advanced" and enter a resolution yourself. Makes things simpler rather than all the film complications we no longer need to get into.

OMG!!