Elliptical Galaxies

I have this question in one of mu tutorial sheets for Astronomy: HELP!

Given that there are 0.1 Ellipticals per Mpc cubed and my garden
telescope can reach to 14 mags. How largew an area of sky would I need
to survey tp find 100 elliptical galaxies? (assume typical absolute
magnitude for an Elliptical galaxy is -21 mags).

Thanks

"F de C W" wrote in message
om...
I have this question in one of mu tutorial sheets for Astronomy: HELP!

Given that there are 0.1 Ellipticals per Mpc cubed and my garden
telescope can reach to 14 mags. How largew an area of sky would I need
to survey tp find 100 elliptical galaxies? (assume typical absolute
magnitude for an Elliptical galaxy is -21 mags).

What are your thoughts on how to solve it? What have you
tried?

We'll help you if you can first show an honest effort.

"F de C W" wrote in message
om...
I have this question in one of mu tutorial sheets for Astronomy: HELP!

Given that there are 0.1 Ellipticals per Mpc cubed and my garden
telescope can reach to 14 mags. How largew an area of sky would I need
to survey tp find 100 elliptical galaxies? (assume typical absolute
magnitude for an Elliptical galaxy is -21 mags).

http://www.phys.ksu.edu/~wysin/astro/magnitudes.html

Use the "Distance Determination" section at
the bottom of the page to work out the limit
of range, R (and bookmark it, you will need
it again someday).

To see 100 at 0.1 per Mpc^3, you need to view
a volume of _____ Mpc^3. How many steradians
do you need to view to enclose that volume in
a sphere of radius R?

Using those hints, post your answer in reply
and remember to show how you got it ;-)

HTH
George

"Greg Neill" wrote in message
...
"F de C W" wrote in message
om...
I have this question in one of mu tutorial sheets for Astronomy: HELP!

Given that there are 0.1 Ellipticals per Mpc cubed and my garden
telescope can reach to 14 mags. How largew an area of sky would I need
to survey tp find 100 elliptical galaxies? (assume typical absolute
magnitude for an Elliptical galaxy is -21 mags).

What are your thoughts on how to solve it? What have you
tried?

We'll help you if you can first show an honest effort.

Sorry Greg, our posts crossed. Maybe I gave away
too much.

George

"George Dishman" wrote in message
...

"Greg Neill" wrote in message
...
"F de C W" wrote in message
om...
I have this question in one of mu tutorial sheets for Astronomy: HELP!

Given that there are 0.1 Ellipticals per Mpc cubed and my garden
telescope can reach to 14 mags. How largew an area of sky would I need
to survey tp find 100 elliptical galaxies? (assume typical absolute
magnitude for an Elliptical galaxy is -21 mags).

What are your thoughts on how to solve it? What have you
tried?

We'll help you if you can first show an honest effort.

Sorry Greg, our posts crossed. Maybe I gave away
too much.

No problem. You've still left the OP with some thinking to
do. :-)