mm length on satellite cameras
Jan 2, 2018 05:54:16 #
Hi ughh users,
I was wondering out of curiosity, what length in mm do satellite cameras in space use (for example photos you would see on google maps). Also, if anybody else knows the answer to this, what mm lens do military drones have equipped (ex. US military predator drones).
I looked on quora for an answer but it isn’t photography oriented. Thanks everyone!
I was wondering out of curiosity, what length in mm do satellite cameras in space use (for example photos you would see on google maps). Also, if anybody else knows the answer to this, what mm lens do military drones have equipped (ex. US military predator drones).
I looked on quora for an answer but it isn’t photography oriented. Thanks everyone!
Jan 2, 2018 06:00:16 #
Jan 2, 2018 06:11:43 #
LarryFitz wrote:
Hubble focal length is 56 m.
That's a figure you don't hear very often.
Jan 2, 2018 06:22:35 #
LarryFitz wrote:
Hubble focal length is 56 m.
Wonder if you could hand-hold that baby......
Jan 2, 2018 06:23:53 #
I'm a geospatial scientist and a technical advisor for some space imaging programs. Focal lengths are typically less than a few meters. What really drives things are the density of CCD's (charged couple devices) on the sensor and the aperture. For example, the aperture on Digital Globe's Worldview 4 is an amazing 1.1 meters. The lens (telescope) is definitely some fine glass, but it's all about packing in sensors and the speed of acquisition and data transmission.
Jan 2, 2018 06:39:19 #
For reference, the aerial imaging camera I have has a max focal length of 210mm. That gets me 5cm pixels flying at 6,000' art a speed of about 300mph.
Jan 2, 2018 06:43:13 #
I believe you are referring to the focal length of the lens in mm; having said that, not knowing the format or the size of the sensor (in some cases the film plate) of the camera, the length in mm is almost of very little use. An 80 mm lens on a medium format camera, i.e. Hasselblad, will be considered a normal lens while on a DX or FX camera it would be accepted as a medium telephoto or portrait lens. The combination of these two numbers would provide a more significant value, better known as the field-of-view (FOV). How many square miles does a Google camera cover during a normal sweep?...
Jan 2, 2018 06:50:41 #
Jan 2, 2018 07:01:58 #
sb wrote:
Wonder if you could hand-hold that baby......
Not holding at all. The hubble stays hold itself.
Jan 3, 2018 08:01:42 #
I do believe the OP is referring to the earthbound-facing cameras - Hubble points the other way of course.
That said, no doubt the "effective foal length" (or really, angle of view) of the Keyhole satellites are still kept somewhat secretive. Years back the declassified documents about them indicated they could resolve down to 4" from an altitude of 200+ miles, as I recall. And that's what the declassified documents stated! Nowadays, with active image correction technology to correct for atmospheric distortions it's no doubt better than that.
That said, no doubt the "effective foal length" (or really, angle of view) of the Keyhole satellites are still kept somewhat secretive. Years back the declassified documents about them indicated they could resolve down to 4" from an altitude of 200+ miles, as I recall. And that's what the declassified documents stated! Nowadays, with active image correction technology to correct for atmospheric distortions it's no doubt better than that.
Jan 3, 2018 08:26:42 #
While there are a lot of satellite cameras looking down at us, I suspect that what you will see on Google maps or Google earth are predominantly aerial photos, not satellite photos. Aerial photography is done on a regular basis by a lot of organizations for all sorts of purposes. Utilities do it to keep track of what's going on around their power lines, pipelines, etc. States do it to track development for planning purposes, collect environmental information for planning and emergency purposes, probably even for traffic monitoring. The USDA does it to track crops and environmental effects. Aerial photographs can be taken for specific purposes at any time desired, while satellite cameras are limited by their orbital parameters.
Jan 3, 2018 10:26:50 #
LarryFitz wrote:
Hubble focal length is 56 m.
Does it have a Hoya or B+W multi-coated polarizer on it?
Jan 3, 2018 11:42:09 #
Jan 3, 2018 11:49:53 #
Jan 3, 2018 19:24:53 #
carl hervol
Loc: jacksonville florida
Most of the time it a 200mm but they do have 600mm all Nikon camera 5ds and Nikon lens of f the shelf equipment with no mods even out side on space walks 
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