(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

Given that there are 10^{-2}Ellipticals per Mpc^{3}and my garden telescope can reach to 14 mag. How large an area of sky would I need to survey to find 100 Elliptical galaxies ? (assume the typical absolute magnitude for an Elliptical galaxy is -21 mag).

2. Relevant equations

d=10^{0.2(m-M-25)}

n=N/V

3. The attempt at a solution

by substituting m=14 and M=-21 into the first equation I found d=100Mpc,

which indicates the volume of sky I could possibly observed is 4/3⋅π⋅d^{3}= 4188790 Mpc^{3},

using the second equation n=N/V , where n=number density, I have 10^{-2}= 100/V,

thus V=10000Mpc^{3}, which is the volume I need to observed to find 100 galaxies.

with these values, how can I find how large the area of sky I need to survey?

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# Observing galaxies: area of sky would I need to survey

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