8) Comet c/2001 Q4 and comet c/2002 T7 are getting brighter. Thus I think this info is veri usefull for all those comet watchers out there.Here’s a formula that could help u pinpoint the two comets on any date any time in the night sky. The ephemeris is a list of positions for comet anytime, usually 0h UT on different dates. Find two times (T1 and T2) that bracket the time u and positions (P1/P2).
Thus u has T1/P1 and T2/P2, where T1 is the first time, P1 is the first position, and T2 is second time, P2 second position. The time u wish to observe T, and the position is define, as P. T must be in UT.
1) Add 24h toT2 for everyday it is a head of T1, do the same for T.
2) Apply the below formula twice, R.A. values P1 and P2, using DEC values for P1 and P2. The first result P will be the R.A. at time T and the second will be DEC.
P = (P2 – P1) / (T2 –T1) X (T – T1) + P1
T1= 0h UT on Oct 10 with R.A. = 10h23m, DEC= 11d 15m
T2= 0h UT on Oct 12 with R.A. = 10h12m, DEC= 10d23m
The time u wish to observe is 9UT on Oct11
We need to convert positions into decimal hours and decimal degrees:
First set of values:
P1 (R.A.) = 10 + 23/60= 10.38333h
P1 (DEC) = 11 + 15/60= 11.25d
Second set of Values:
P2 (R.A.) = 10 + 12/60= 10.2h
P2 (DEC) = 10 + 23/60= 10.38333d
Now sub in the values to get R.A. at time T
P (R.A) = 10.2573h
P (DEC) = 10.6542d
Convert positions back from decimals:
R.A. = 10 + 0.2573 X 60 = 10h15m
DEC= 10 + 0.6542 X 60 = 10d39m
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