Astrophotography Image Processing and Analysis Software

PixInsight and Photoshop are the thee main applications I use for image processing. PixInsight to stack images and for the bulk of processing and Photoshop for final touch up. Almost all images on this sight were created with PixInsight.


Automatically detects stars and then registers (aligns) and stacks images (combines exposures by mathematical processing such as averaging). I do not use any of the post stacking features. I save files with adjustments embedded but not applied. For Stacking Mode, I generally use Kappa-Sigma clipping with Kappa=1.5 and Iterations=5. I do all image processing in a dedicated Astrophotography specific software package or Photoshop. Deepskystacker's registering operation is generally good. It's stacking operation is probably the best among free software packages.

PixInsight (Commercial)

Probably the most advanced application for astronomical image post-processing. PixInsight provides all the functions needed for post-processing with many adjustable parameters. It has a steep learning curve but worth the effort. For example for noise reduction there are multiple algorithms to chose from. It is also a development platform where users can add modules. Documentation is light but there are many resources available on the web.

Photoshop (Commercial)

The industry standard. Many astrophotographers do all their post processing in Photoshop. For most images I do initial processing in StarTools and then some final touch up with Photoshop.

StarTools (Commercial)

Astronomical image post-processing. A less expensive and less feature rich alternative to PixInsight. Provides image stretching, sharpening, noise reduction and many other useful image processing and manipulation features. A little difficult to use at first and documentation is lacking but with practice I have found I can produce better final images than from Photoshop alone and with less effort.

Registar (Commercial)

Aligns (Registers) and scales digital astronomical images with a more general approach than DeepSkyStacker. Useful for creating images from data acquired from multiple telescopes of different focal lengths and pixel resolutions and for creating mosaics from multiple images. Expensive for what it offers, most of its features are available in PixInsight and PixInsight seems to do a better job.

Aladin Sky Atlas

Interactive sky atlas that can be run as a desktop application. Aladin shows a small section of sky often with stars to 20th mag and galaxies a few magnitudes beyond that. Useful for analyzing field objects within an image or identifying detail within a larger object. Aladin also supports loading user images. If the images are "Plate Solved" (mapping sky coordinates to the image, in this case to enable automated sky catalog matching), the image can be loaded into Aladin and Aladin can then overlay objects in the field of view from various object databases such as SIMBAD and NED. The result sets from object database can be filtered and annotated directly on the image. For some reason Aladin does an image rotation along the vertical axis when it displays an image from a file.

Online Plate-Solving. Upload an image to this server and the sever will locate the RA and Dec images coordinates. returns a FITS image file with celestial coordinates embedded in the file. The file can be loaded into Aladin which will overlay objects within the field of view. Uploading an image to this site is essentially making the image public domain.

FITS Liberator

Used to convert and process FITS images to the more general TIFF image format which can be loaded by Photoshop and as the first step in creating color images from a range of telescopes including the Hubble Space Telescope and NASA’s Spitzer Space Telescope.


Planetarium software. Useful for planning observing sessions, determining object altitude for a given date, time and location, determining moon altitude/illumination and estimating how an object will look in a given field of view. I tend to use for locating dynamic conditions - object altitudes and lunar position for a given location and time, locating planets, planet moons, asteroids and comets.


Online sky atlas. Stars to about 18th mag. Useful for identifying galaxies to about 18th mag, locating planets, asteroids and comets. Seems to be offline often.


Image processing and file conversion. Can convert files back and forth between FITS and TIFF with many other useful image processing features.

IRAF (Image Reduction and Analysis Facility)

IRAF is a collection of software functions for analyzing astronomical data. IRAF is generally used by professional astronomers and is often sited in academic papers. It is difficult to setup and use but IRAF has some functions that may be of interest to amateurs. A primary use of IRAF is Photometry. It can producing surface and contour plots. I used IRAF to create this surface plot. IRAF is free but requires Linux.

Professional Image Data Repositories

These repositories provide public access to FITS data acquired from space telescopes and large ground based observatories.

  1. DR12 Science Archive Server (SDSS-III) - High resolution in IR, Red and Green filters

  2. ESO Archive - Good data source across a range of telescopes but difficult to use

  3. Palomar Observatory Sky Survey (POSS) - Medium resolution in Red and Blue filters

  4. Keck Observatory Archive (KOA)

  5. SMOKA - Subaru Mitaka Okayama Kiso Archive, various instruments, registration required

  6. MAST - Mikulski Archive for Space Telescopes (Hubble, GALEX, SWIFT)

  7. Spitzer Infrared Nearby Galaxies Survey - Galaxy image data