After I got my imaging telescope (AstroTech AT6-RC), I started targeting deep-sky targets. It took a while to get the whole process dialed in properly. Things like proper load balancing, polar alignment, calibration, getting all the cables hooked up, calibrating the guider, setting the focus (quite a complicated task when you cannot see your target through the viewfinder or LiveView), finding your target, framing, determining each frame parameter (e.g. required exposure length, ISO), and then hoping no clouds come in and ruin it all. Then there’s the additional task of making sure you have a library of dark and flat frames built up for processing. And processing itself is quite lengthy. The initial calibration and stacking of the frames is a pretty automated process but can take anywhere from 2-6 hours, depending on the amount of data. Then comes the actual processing, which requires painstaking attention to each part of the final image. But when you realize that the final product is of an object thousands or millions of light-years away in space, it’s all worth it.
Nebulae are some of the brighter and therefore easier objects to photograph. For one of the my first targets, I settled on Elephant’s Trunk Nebula (IC 1396A), which rose in the eastern sky after dark in the summer. It is a concentration of interstellar gas and dust about 2,400 light-years away. It is the site of star formation containing several very young stars (only a few million years old). Wind from the two stars at the tip of the Trunk have emptied out a cavity in the nebula.
This was quite a tricky target because I couldn’t actually see it in my test images (1-min exposures). I just tried to make sure the bright stars there were at the tip of the Trunk were in the frame and got on with it. Shot a total of 2.5 hours of exposure (30 frames @ 5 min each). After stacking all the frames, it seemed like I’d failed to capture anything. But after playing around in Photoshop I noticed that there were some faint details hiding in the shadows. A long process of careful processing slowly brought out the details. Although it wasn’t the cleanest image, I was nevertheless very happy with capturing it.
Buoyed by the relative success in shooting Elephant’s Trunk Nebula, I turned my attention to a long-time favourite of mine, the Eagle Nebula (Messier 16). The 1995 Hubble image of the “Pillars of Creation” in the Eagle Nebula just took my breath away, and with my imaging setup I had the equipment to try to capture it myself. The nebula is an active star-forming region 6,500 light-years away and is 5.5 million years old. The nebula is lit up by the star cluster that was born from the gas and dust. The Pillars contain stellar nurseries of dense evaporating gaseous globules, with the longest pillar being 57 trillion miles long.
The Eagle Nebula was visible with the naked eye from our house in Colorado. The cluster of bright stars surrounded by a hazy “cloud” stood out in the night sky. With a pair of binoculars or a basic telescope, the shape was easily evident. Unfortunately, given the latitude, it keeps relatively low in the southern sky over Colorado, and the southern part of the sky from our house had the worst light pollution (interstate highway + strip malls). So I had to keep my exposure time low – 5 frames @ 1-min + 11 frames @ 5-min = 1 hr total). But given how bright it is, I was still able to get a decent final picture, complete with the Pillars of Creation.