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"Baade's Window", named after the astronomer who selected this area of the sky for his study of variable stars, is the one of the most densely packed star fields that we can see when we look toward the centre of own galaxy, the Milky Way.  It is a clearing in the dust clouds of our Galaxy, enabling us to view stars in the Galactic bulge.  Baade's window lies four degrees south of the Galactic centre, so our line of sight passes within 1800 light-years of the Milky Way's centre.

The image above shows a multitude of stars in an area of the sky only about 40 mins arc wide. The 6th magnitude star HR 6692 is the blue star just above the centre of the image.  Some parts of the image appear to show fewer stars.  This is caused by wisps of dark interstellar dust stretching across the foreground and obscuring background stars from view.

Image info

Telescope:  Celestron 9.25" Schimdt-Cassegrain at f/6.3

Focus:  Prime focus

Filter:  Celestron LPR filter

Mount:  Vixen GPD with Skysensor2000

Camera:  Modified Canon EOS 300D, at ISO800

Guiding:  700mm refractor guidescope, SAC7 camera, autoguided with Guidedog software

Exposure:  Total 55 mins (28 x 118s)

Date:  10th July 2005

Processing:  RAW file conversion, Offset and Dark subtraction, flat fielding, registering and stacking done in IRIS. Colour enhancement using the 'asinh' function in IRIS.  IRIS pre-processing almost all automated with AutoIt scripts.  Curve stretching in Photoshop CS, background subtraction in PixInsight.


I have added PixInsight to the set of tools I use for image processing.  In particular, DBE (Dynamic Background Extraction) is a powerful means of removing unwanted vignetting and gradients.

This is also the first image whose acquisition was managed by GADFly, an AutoIt script I wrote to automatically nudge the position of the guidestar every few exposures.


Copyright 2003 to 2014, by TG Tan.  All rights reserved.  Copyright exists in all original material available on this website.  This material is for your personal individual, nonprofit use only.  Redistribution and/or public reproduction of this material is strictly prohibited without prior express written permission from the author.