Identifying Photographic Objects
Astro-imaging has revolutionised amateur astronomy over the last couple of decades. It’s now commonplace to see images which are equal or better than images taken by larger professional telescopes pre-digital photography.
With low noise CMOS and CCD cameras, amateurs are picking out fainter objects than are found in most sky atlases, making identification difficult.
It’s nice to independently confirm details of the target; and it’s enriching to identify any unexpected objects in the image.
These are some of the tools I use:
I submit all images to nova.astrometry.net (1). Within minutes I obtain a copy of my image, annotated with the identities of stars and certain deep sky objects. Useful stats are supplied, including the field of view and image orientation.
Sky Safari Pro (2) is an app for tablets and phones, surpassed by none, identifying over 100 million stars, 3 million galaxies down to 18th magnitude and every comet and asteroid ever discovered. It can do much more; but it’s the reliable object data base and display which are invaluable, at home and out in the field.
The Simbad online data base (3) is a library of deep sky objects maintained by Strasbourg Astronomical Data Centre. It’s updated by professional astronomers and is useful for teasing out more information about specific objects.
Another online tool which has come in handy has been Google Sky (4). It’s great for identifying sky coordinates of unknown objects.
Example 1: I recently posted a 2½ hour exposure of galaxy M83 on my website. It showed a pair of tiny smudges appearing next to M83. (see red marks on image). “What do I think they are?” enquired one subscriber, an experienced amateur astronomer. (Thanks, Marty).
Using the above tools, I established the names of the mystery objects, both galaxies: ESO 444-85 and [R84] A1-342. I was astonished to learn that these 16th and 17th magnitude galaxies on my image are a boggling 665 million light-years away, (redshift 0.012 – receding at 4.6% light speed).
As an amateur, I never expected to capture galaxies that are two thirds of a billion light years away. The light was emitted when the first fossils that might represent animals were forming on Earth!
Example 2: I wanted to identify a fairly bright star close to globular cluster C105. I went to Google Sky for the coordinates and found the star – no longer bright but very faint. A variable star!
I was able to identify it as RZ Muscae, a star which pulses between 13th and 16th magnitudes every 47 weeks.
Astronomy is exciting but can be even more rewarding when you research and document what you capture!