8
$\begingroup$

The Curious Droid YouTube video How did NASA get those great film shots of Apollo and the Shuttle? found here and linked-to in this comment contains the following passage starting at 05:26:

This piece of footage here of the shuttle Discovery at T+40 seconds is shot from a medium distance camera about 3.8 kilometers from the launch pad using a 150 inch lens with a 4,000 mm focal length as the shuttle is accelerating through 20,000 feet. As discovery goes through a 145,000 feet at 123 seconds into flight, the boosters separate, which is captured here by another 150 inch, 4,000 mm focal length lens on a KTM. The weight of the lens alone on these was about 115 kilograms, and the tracking to keep the discovery in the frame was done by a human, and not an automated system. After three minutes the job of filming the ascent was transferred to the largest telescope on the site, the permanently mounted 24-inch aperture Recording Optical Tracking Instrument, or ROTI. With a focal length of up to 12,700 mm, ROTI had enough magnification to follow the launch for up to five minutes after liftoff. ROTI used both radar assisted tracking and a joystick for manual adjustment, which had such a fine sensitivity but it could register the heartbeat of the user if held too firmly.

High quality, imaging, achromatic lenses are never 150 inches (~3800 mm) in diameter. The Yerkes Observatory's 40 inch (1,000 mm) refractor is the largest diameter refracting telescope ever built, and that was about f/18.

Even if it were a reflecting 3.8 meter diameter primary, f/1.05 would be an impressive looking instrument.

Question: What are this optical system's actual specs, such as diameter of primary lens or mirror, focal length, and number of reflecting and/or refracting elements? It sounds amazing!


enter image description here

$\endgroup$
  • 4
    $\begingroup$ 4000 mm is just over 150", so the 150" refers to focal length, not diameter. $\endgroup$ – Hobbes May 5 '18 at 7:29
  • 1
    $\begingroup$ @OrganicMarble For want of a "c", the lens was organic. Thanks! $\endgroup$ – uhoh May 5 '18 at 15:15
  • 1
    $\begingroup$ now all you need is an h... $\endgroup$ – Hobbes May 5 '18 at 15:34
  • 1
    $\begingroup$ @Hobbes (blush) I'll get there eventually. At least I spelled Yerkes right. $\endgroup$ – uhoh May 5 '18 at 15:47
  • 1
    $\begingroup$ The Yerkes refractor was not the largest diameter ever build, the Great Paris Exhibition Telescope of 1900 had a lens of 1.25 m (49 inch) diameter. $\endgroup$ – Uwe May 7 '18 at 16:55
18
$\begingroup$

The lens is a Brashear (now L3) SR 150 lens.

SR-150

Focal length 150" - 3810 mm
Aperture 15.4" - 391 mm

This is a Cassegrain-type lens. The lenses are installed on an L3 Kineto Tracking Mount.

A really good overview of all the photography going on during a Shuttle launch is Ascent, an hour-long video that shows samples from each type of camera. Many of these cameras are high-speed, so you get fantastic slow-motion shots of the Shuttle taking off. The narration has a lot of detail on the cameras used, and all the stuff going on in the first minute after launch.

This PDF has a map of the camera sites around the pad.

short range cameras

medium range cameras

$\endgroup$
  • $\begingroup$ Super-informative and well-sourced answer, thank you! $\endgroup$ – uhoh May 5 '18 at 8:59
  • $\begingroup$ "Ascent" is indeed a remarkable film. $\endgroup$ – Organic Marble May 5 '18 at 11:28
  • $\begingroup$ The Cassegrain telescope is not a refracting telescope, it is a reflecting telescope. It may be build without any lenses, only with curved mirrors. $\endgroup$ – Uwe May 6 '18 at 20:02
  • $\begingroup$ you're right, but the term "lens" is used here as "the optical assembly in front of the film transport" as is common in photography. The manufacturer also calls it a lens. $\endgroup$ – Hobbes May 6 '18 at 20:18
  • $\begingroup$ So it is, in astronomer terms, a 15-inch f/10, approximately. $\endgroup$ – hobbs May 7 '18 at 5:58

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.