[chiph]

> The Atro Tracker also has declination limits of +90° and -47° and a lower altitude limit of -6°. The latitude is limited to the range between -2° and +90°; the system automatically switches hemispheres so both the North and South latitudes are usable.

Why would the system need to have a much greater range of declination (celestial sphere) than latitude (Earth spheroid)? Because the Astro Tracker and Angle Computer could flip over to the Southern hemisphere (was this automatic or was there a switch?) having that much declination range seems unnecessary. Perhaps to allow for pitch of the aircraft in flight?

BTW, being able to operate in both the Northern & Southern hemispheres was an important capability for the B-52. Previous bombers (B-36 mostly) had the range but not the reliability or in-flight refueling for global reach.

Sadly, I didn't get the chance to look at the B-52 at the Museum of Flight when I was there. If you ever meet Charles Simonyi, please thank him for his support of the museum.

[kens]

If you're flying in low latitudes, nearly half the stars that you want to use are going to have negative declination, so negative declinations are important. As for the hemisphere switching, this happened automatically.

[chiph]

Once in the Southern Hemisphere, they'll need to pick a new set of stars. So their declination would still be expressed negatively?

Or is it that they considered the need to navigate below the lower fourth of Argentina a distant possibility?

[kens]

It's totally normal to be in the northern hemisphere and looking at stars below the celestial equator. For instance, Sirius is the brightest star in the night sky and is in the southern half of the celestial sphere. So if you wanted to navigate with Sirius, the system had to support negative declination. (They define negative declination as in the opposite N/S hemisphere from the aircraft.)

[themadturk]

The B-52 is one of my favorite aircraft, and the one at the Museum of Flight is an absolute beast -- I never thought it was small, but it's still bigger than I expected.