Telescope Exercise

Recall:

Two sample precession calculations:

Assume that you observed on March 25, 2001. Time that has elapsed since January 1, 2000:

365 days + 31 days + 28 days + 25 days = 449 days = 1.23 yrs

Coordinates for M3, a nice globular cluster:

(2000.0 epoch) RA=13h 42m 11.23 s DEC=+28º 22' 31.6"

RA= 13 + 42/60 + 11.23/3600 = 13.703119hr x 15 deg/hr=205.546785º

DEC = 28 + 22/60 + 31.6/3600 = 28.375444º

RA(Mar 25, 2001)=13hr 42m 11.23sec + 3.40sec = 13 hr 42m 14.63sec

DEC(Mar 25, 2001) = 28º 22' 31.6" - 22.2" = 28º 22' 09.4"

Coordinates for NGC 2438

(2000.0 epoch) RA= 07h 41m 50.4s DEC=-14º 44' 02"

RA= 15 x (7 + 41/60 + 50.4/3600) = 115.46º

DEC = -(14 + 44/60 + 02/3600) = -14.733889

RA(Mar 25, 2001) = 07h 41m 50.4s+3.391s = 07h 41m 53.8s

DEC(Mar 25, 2001) = -14º 44' 02" - 10.6" = -14º 44' 12.6"

The telescope reported different coordinates because its control program also takes into account factors such as the mechanical bending (flexure) of the telescope tube and mount.