Moondark for October: Shooting Southern Skies with a Digital Rebel
My most enjoyable nights under the sky have been spent without a telescope. Located as far south of the equator as we here are north of it, New Zealand has some of the cleanest air on the planet and is thinly populated. Outside the handful of big cities, the skies are inky black. The Southern Cross, Milky Way and the Magellanic Clouds show brightly overhead. If the weather would cooperate, I’d have an excellent shot at capturing astrophotographic souvenirs of these southern skies.

During the dark of the moon last January, I was booked into accommodations where I expected dark skies and spectacular views. I’d packed my Canon Digital Rebel (aka 300D), cable release and tripod, along with a star chart and red flashlight. The plan was to shoot several exposures in quick succession, limiting exposure length to prevent stars from trailing. While a quick check of the raw images looked promising, the plan was ultimately to align and composite individual frames to attain effectively a longer exposure.

For each part of the sky, about four to six images of 30 s each were taken. I used the 18-55 mm zoom lens supplied with the camera, wide open. The camera was set to ISO 1600 and the highest resolution (3072 x 2048) with JPEG compression. Images were aligned and combined with Christian Buil’s freeware program Iris 4.37 using the coregister function and deep-sky registration menu options. Some images required a bit of trial and error to obtain the best results. Windowing the automatic registration region and down sampling the image both helped considerably.

The images at right are the result. If anything, I wish that I had taken more images to composite, but even then, there are so many stars that identifying southern constellations—what I did visually while not photographing them—is all but impossible. One image, taken as the southern Milky Way rose directly up almost like smoke from a hillside south of my observing spot, is by far my favorite because it best matches my recollection of those nights. I’ll certainly go back—this time with a telescope.

Yahoo! groups are a great source of information on DSLR’s in astrophotography: I’ve found the Canon_DSLR_digital_astro, digital_astro and Iris_software groups especially useful. Of course the same techniques work under our skies, and several members of the Delmarva Star Gazers are exploring the potential of DSLR’s in astrophotography. Thanks especially to Tom Pomponio for advice and suggestions.

This is based on a presentation given at the club's September monthly meeting, and more information on wide-angle astrophotography can be found in last month's issue. Moondark is written by Doug Miller, published at the Moondark web site, and printed in the Delmarva Star Gazers' Star Gazer News. This document was last revised on 25 September 2005. Text and images copyright © 2005 by Douglas C. Miller, All Rights Reserved. This material may not be reproduced in any form without prior permission.
Upside down Orion and Saturn in Gemini on the horizon
The Coal Sack (dark nebula), Southern Cross and bright nebulosity of the Eta Carinae region of the Milky Way
The Large Magellanic Cloud, a companion galaxy of the Milky Way, in the constellation of Dorado
Centaurus, Crux and Carina rise above the landscape of the Coromandel Peninsula