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Rate of Right Ascension

  1. Jan 28, 2016 #1
    1. The problem statement, all variables and given/known data
    This is an Astrometry problem. I am not sure or how exactly to proceed:


    First off, I am unsure which data points to use. Should I use the values from right ascension or the values from the time index.

    1 hour = 15 degrees
    24 hours = 360 degrees

    Image 01 Right Ascension: 23:03:53.99
    Image 02 Right Ascension: 23:03:49.17

    Image 01 RA - Image 02 RA = 23:03:53.99 -23:03:49.17 = 00:00:04.82

    Image 01 Time Index: 12:16:58 UTC
    Image 02 Time Index: 4:39:04 UTC

    Image 01 Time Index - Image 02 Time Index = 4 hours 56 minutes 2 seconds = 17,762 seconds

    Calculate the rates of motion in Right Ascension (seconds/hour) of the asteroid:

    2. Relevant equations
    Rate = Distance/Time

    3. The attempt at a solution

    With values from Right Ascension

    4.82 sec/ 15 degrees = 0.32133 (3 repeats) sec/deg


    With values from Time Index
    17,762 sec/ 15 degrees = 1184.13 (3 repeats) sec/deg
  2. jcsd
  3. Jan 28, 2016 #2


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    You're supposed to calculate the rates in sec of arc/hour, which is not the same units as sec (of time) / deg.
  4. Jan 28, 2016 #3
    Thank you for the response SteamKing.

    I'm not sure I understand. Can you expand on that? I'm also confused on which value I am supposed to use - the Right Ascension value or the rime index value?
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