<p>Several different units are possible. If you double click on the box a dialogue window will open where you can adjust the size/location. In the drop-down menus on the right hand site, you can choose which unit and coordinate system you want.   </p>

<p><a href="https://i.sstatic.net/ct5dP.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/ct5dP.png" alt="enter image description here"></a></p>

CC BY-SA 4.0
2019-06-18T13:02:22.453Z
2019-06-18T13:02:22.453Z
samcarter_is_at_topanswers.xyz
<p>Usually pixel coordinates.
What I would do is to let DS9 make a region file, as your documentation site says it supports them.</p>

<p>To do so:</p>

<ul>
<li>Open file in ds9</li>
<li>From region->shape select the kind of region you want.</li>
<li>Click on edit->region</li>
<li>Draw the shapes you want (just click on the img)</li>
<li>Click region->save. In the coordinates box choose physical pixel coordinates.</li>
</ul>

<p>Probably that should work... Good luck!</p>

CC BY-SA 4.0
2019-06-18T12:47:38.377Z
2019-06-18T12:47:38.377Z
Ewoud
<p>I am a complete beginner in astronomy. While learning DS9, I came up with the following question.</p>

<p>Say I want to exclude a boxed region from an image FITS. The corresponding parameters according to <a href="http://cxc.harvard.edu/ciao/ahelp/dmregions.html" rel="nofollow noreferrer">Chandra</a> is</p>

<ul>
<li>Box = (xcenter,ycenter,width,height)</li>
<li>Box = (xcenter,ycenter,width,height,angle)</li>
</ul>

<p>Although the name is self-explanatory yet I am confused about their respective units. What unit is used to label these parameters?  </p>

<ds9>
Excluding a rectangular region from an image in FITS
Mass
# Excluding a rectangular region from an image in FITS

(Asked by: username_0 on 2019-06-18)

I am a complete beginner in astronomy. While learning DS9, I came up with the following question.

Say I want to exclude a boxed region from an image FITS. The corresponding parameters according to [Chandra](http://cxc.harvard.edu/ciao/ahelp/dmregions.html) is

* Box = (xcenter,ycenter,width,height)
* Box = (xcenter,ycenter,width,height,angle)

Although the name is self-explanatory yet I am confused about their respective units. What unit is used to label these parameters?

**Tags:** ds9


---

## 2 answers

### Answer by username_2 on 2019-06-18. Score: 5 | Accepted answer

Usually pixel coordinates.
What I would do is to let DS9 make a region file, as your documentation site says it supports them.

To do so:

* Open file in ds9
* From region->shape select the kind of region you want.
* Click on edit->region
* Draw the shapes you want (just click on the img)
* Click region->save. In the coordinates box choose physical pixel coordinates.

Probably that should work... Good luck!


---

### Answer by username_1 on 2019-06-18. Score: 3

Several different units are possible. If you double click on the box a dialogue window will open where you can adjust the size/location. In the drop-down menus on the right hand site, you can choose which unit and coordinate system you want.

[![enter image description here](https://i.sstatic.net/ct5dP.png)](https://i.sstatic.net/ct5dP.png)


---

