# Homework Help: Archived Calculating the optimal day to observe an object given the RA and dec

1. Aug 20, 2014

### pondzo

1. The problem statement, all variables and given/known data

OmegaCen is a Globular Cluster which lies at coordinates: R.A. = 13h26m45.89s,
Dec = −47°28′36.7′′ (J2000.0) estimate the optimal day on which to observe
this object.

2. Relevant equations

3. The attempt at a solution

We are to interpret optimal as 12 am midnight directly overhead

since this is 12 hrs after noon you subtract 12hrs RA = 1hr26m45.89sec
which is ≈ 1.446 hrs RA and this is due to the monthly RA shift
2 hrs of RA shift per month so, 30/1.446 ≈ 20.75 days
so 20.75 days after the vernal equinox, which is april the 10.75 th
im not quite sure how to interpret the 10.75, do i say its on the 10th of april or the 11th ? and the observation is meant to be at 12 am midnight so would you say its on the 11th april? (at the very beginning). Thank you!

2. Feb 4, 2016

### Staff: Mentor

The vernal equinox probably won't happen exactly at midnight, but that depends on the time zone... April 11th should be fine.