<p>You can use <a href="http://nova.astrometry.net/" rel="nofollow noreferrer">astrometry.net</a> to get the exact WCS of your image.</p>

<p>From the website:</p>

<blockquote>
  <p>If you have astronomical imaging of the sky with celestial coordinates you do not know—or do not trust—then Astrometry.net is for you</p>
</blockquote>

<p>There is a web application where you can just upload your image and it returns accurate calibrations. </p>

CC BY-SA 4.0
2019-11-26T07:57:17.913Z
2019-11-26T07:57:17.913Z
usernumber
<p>Recently I have got a bunch of raw fits images (2048x2048 pixels) of the same sky region without WCS to process in iraf. However, those images are not well-aligned. There would be around 4~5 pixels' deviation for a specific star, thus giving me choppy batch photometry analysis result. Are there any ways to add WCS coordinate using several reference stars or create a user-defined coordinate system so that the same star would have uniform coordinates?</p>

CC BY-SA 4.0
2019-11-23T02:48:16.987Z
Suggest you check out astrometry.net, an automatic blind astrometry solver
astrosnapper
<observational-astronomy><ds9><fits-header>
Align multiple fits images without WCS for future aperture photometry analysis
march_happy
# Align multiple fits images without WCS for future aperture photometry analysis

(Asked by: username_0 on 2019-11-23)

Recently I have got a bunch of raw fits images (2048x2048 pixels) of the same sky region without WCS to process in iraf. However, those images are not well-aligned. There would be around 4~5 pixels' deviation for a specific star, thus giving me choppy batch photometry analysis result. Are there any ways to add WCS coordinate using several reference stars or create a user-defined coordinate system so that the same star would have uniform coordinates?

**Tags:** observational-astronomy, ds9, fits-header
> **Comments:**
> **username_1**: Suggest you check out astrometry.net, an automatic blind astrometry solver  

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## 1 answers

### Answer by username_2 on 2019-11-26. Score: 2 | Accepted answer

You can use [astrometry.net](http://nova.astrometry.net/) to get the exact WCS of your image.

From the website:

> If you have astronomical imaging of the sky with celestial coordinates you do not know—or do not trust—then Astrometry.net is for you

There is a web application where you can just upload your image and it returns accurate calibrations.


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