Digital Images and Image Analysis
Sombrero Galaxy Across the Spectrum
Credit: Todd Boroson/NOAO/AURA/NSF
Just about everyone has seen beautiful astronomical images and wondered if this is what the object “really” looks like. The image on this page shows the “Sombrero galaxy”, or M104. It is composed by combining images taken through different filters, a technique in image analysis that you can explore, using the links to background material and data on this page.
All images in modern astronomy are taken with cameras that are similar to an ordinary digital camera. However, in order to use these images for scientific study, objects are imaged sequentially through different filters. To learn more, download the document ccd_intro_web.pdf. You will also need to download and install the ImageJ software to manipulate the data. You can choose different data images below.
Each of the following zipped files includes multiple FITS files showing the object taken through different filters. Most of the objects on this page have been imaged in B, V and H alpha at the 0.9m WIYN telescope at Kitt Peak. More information on them is easily available through a web search of their identification number. The images are matched so they do not require shifting in most cases. You will have to experiment with the contrast (described in the document you downloaded) to see the nebulosity, or galaxy, or planetary nebula in these images. Hint: in most of the images, the dynamic range is very small. Start with minimum values around zero, maximum value of only a few hundred data numbers.
Star clusters and nebulosity:
- M16: Very bright nebulosity!
- M17: Another bright nebula. There are 4 images which include an R filter
- NGC7023. Faint nebulosity surrounding the bright star. Is there really a cluster here
- Caldwell 27 (NGC 6888): again, is this a star cluster?
- IC 5146: Another young cluster with gas and stars.
M51: the folder labeled “test images” contains B,V,R and H alpha images taken in 2003 The folder labeled M51_SN contains images in 5 filters taken 30 June 2005, the night after a supernova appeared in the galaxy. Examine these and compare with the 2003 data to see if you can identify the supernova.
(For additional images of open
clusters,see the open cluster page):
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