<p>An <a href="http://www2.aao.gov.au/%7ETDFgg/Public/Survey/Overview/img009.GIF" rel="nofollow noreferrer">image from the
aao</a> (<a href="https://web.archive.org/web/20070304232459/http://www2.aao.gov.au/%7ETDFgg/Public/Survey/Overview/img009.GIF" rel="nofollow noreferrer">see wayback</a>) shows the design.</p>
<p>The North Galatic polar band has a depth of 7.5 degrees, and the South Galatictic polar band has 15 degrees, (there were also random sampling around the SGP)</p>
<p><a href="https://i.sstatic.net/9Xs9u.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/9Xs9u.png" alt="enter image description here" /></a></p>
<p>That also gives the volume in the strips, but you should be able to confirm that by calculation.</p>

CC BY-SA 4.0
2021-11-20T08:35:16.397Z
2021-11-21T00:20:06.447Z
2021-11-21T00:20:06.447Z
James K
<p>Say I want to calculate the comoving volume in the 2dFGRS survey:
<a href="https://i.sstatic.net/mjpGr.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/mjpGr.jpg" alt="2dFGRS" /></a></p>
<p>I'm using <span class="math-container">$H_{0} = 70 km s^{-1} Mpc^{-1}$</span> and the default values for the matter and vacuum density parameters in this calculator (<a href="http://www.astro.ucla.edu/%7Ewright/CosmoCalc.html" rel="nofollow noreferrer">Cosmological Calculator</a>) to get a comoving volume within 2.5 z of <span class="math-container">$4.325 Gpc^{3}$</span>.</p>
<p>I know that the full night sky from Earth has angular area of 41,253 square degrees.</p>
<p>What I'm unsure of is how to use this image to calculate the total comoving volume represented by the image, especially if the image doesn't provide the &quot;depth&quot; of these slices. Any ideas?</p>

<cosmology><sky-survey>
Calculating comoving volume of 2dF survey
ObiDonKenobi
# Calculating comoving volume of 2dF survey

(Asked by: username_0 on 2021-11-20)

Say I want to calculate the comoving volume in the 2dFGRS survey:
[![2dFGRS](https://i.sstatic.net/mjpGr.jpg)](https://i.sstatic.net/mjpGr.jpg)

I'm using $H\_{0} = 70 km s^{-1} Mpc^{-1}$ and the default values for the matter and vacuum density parameters in this calculator ([Cosmological Calculator](http://www.astro.ucla.edu/%7Ewright/CosmoCalc.html)) to get a comoving volume within 2.5 z of $4.325 Gpc^{3}$.

I know that the full night sky from Earth has angular area of 41,253 square degrees.

What I'm unsure of is how to use this image to calculate the total comoving volume represented by the image, especially if the image doesn't provide the "depth" of these slices. Any ideas?

**Tags:** cosmology, sky-survey

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## 1 answers

### Answer by username_1 on 2021-11-20. Score: 2 | Accepted answer

An [image from the
aao](http://www2.aao.gov.au/%7ETDFgg/Public/Survey/Overview/img009.GIF) ([see wayback](https://web.archive.org/web/20070304232459/http://www2.aao.gov.au/%7ETDFgg/Public/Survey/Overview/img009.GIF)) shows the design.

The North Galatic polar band has a depth of 7.5 degrees, and the South Galatictic polar band has 15 degrees, (there were also random sampling around the SGP)

[![enter image description here](https://i.sstatic.net/9Xs9u.png)](https://i.sstatic.net/9Xs9u.png)

That also gives the volume in the strips, but you should be able to confirm that by calculation.


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