# Rate of Right Ascension

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1. Jan 28, 2016

### Haseo Antares

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

Data:

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

Question:
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

OR

With values from Time Index
17,762 sec/ 15 degrees = 1184.13 (3 repeats) sec/deg

2. Jan 28, 2016

### SteamKing

Staff Emeritus
You're supposed to calculate the rates in sec of arc/hour, which is not the same units as sec (of time) / deg.

3. Jan 28, 2016

### Haseo Antares

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?