Messier 27 – the Dumbbell Nebula

Space is full of interesting objects. We often think of stars and galaxies, but there are other kinds of distant objects that have been discovered over the past 250 years. In 1764 the French astronomer Charles Messier found a whole new class of objects. He was hunting for comets, and had started to create a list of things in the sky that might look a little like a comet, but which didn’t move. The list, now known as the Messier Objects, was originally intended to help him and others find comets by confirming which things viewed though telescopes weren’t actually comets.

Nearly 250 years ago, he turned his telescope to the sky and found something he catalogued as the 27th object in his list. For some time the telescopes available showed objects like M27 as looking a bit like the distant, outer planets in our own solar system, and they picked up the general name “Planetary Nebulae.” Just what they were wasn’t explained for another century, when William Huggins was able to look at the light from one of these fuzzy, roundish objects. Through spectroscopy he realized that he wasn’t looking at light being reflected from an object like a planet, or light from a hot luminous object like a star, but light being generated by excited gasses.

Planetary nebulae are now known to be the spectacular remnants of a star that is throwing off vast quantities of gas late in its life. Some of them appear to be shedding multiple shells of gas. In the case of Messier 27, also called the Dumbbell Nebula, researchers have estimated that the bright gas we can see with telescopes likely was emitted from a star in the centre of the object about 10,000 years ago.

In early May 2013 I decided to try using the University of Iowa’s Rigel telescope at the Winer Observatory, southeast of Tucson, Arizona (http://www.winer.org/) to image M27. This telescope can be used by anyone over the Internet on the Sierra Stars Observatory Network (http://www.sierrastars.com), and I’ve been experimenting with it for the past few weeks.

To take an image of Messier 27 I first programmed the telescope to take a single shot of the nebula for 150 seconds, to get a feeling for exposures, which the telescope captured early on the morning of 7 May 2013. M27 is quite a bright object, and many people have fun finding it with a small telescope. It has a magnitude of 7.5, meaning that it’s just below the limit of objects you can expect to see on a dark sky with your eyes, but it’s well within the expected range of objects to see with a modest amateur telescope or binoculars.  It’s in the Vulpecula constellation (“the little fox”) just south of Cygnus, the swan. The 150 second exposure wasn’t overexposed for the nebula, and in fact looked a bit faint, so I decided to take a series of 300 second images. I set the telescope to take two 300 second exposures with no filter, and two more 300 second exposures with each of the red, green, and blue filters on the system. The images were captured early on the morning of Thursday 9 May 2013. Here’s the result, after combining the “black and white” frames first (“Luminance”) and then preparing the colour information (“RGB”), using free software called Fitswork4:

M27 imaged with Rigel

Messier 27, the Dumbbell Nebular, imaged with the 37 cm Rigel telescope owned by the University of Iowa, located in Arizona (the “Iowa Robotic Telescope Facility” or IRTF). The image was prepared from a series of monochrome pictures taken through colour filters (the “LRGB” process). combined with Fitswork4 and adjusted a bit with Adobe Photoshop Elements.

The Dumbbell Nebula sits about 1,360 light years away from earth, and is about one light-year across. It’s also notable because of the star that remains at its centre: it’s the largest-known white dwarf star.

This first try at M27 is encouraging, but I wasn’t able to get good registration, or alignment, of the red, green, and blue frames. As a result the colours I was able to produce in the combined image are a bit off. If I can improve the registration process the image should be a bit better. I need to do some more work on my “workflow” to process image files once I have them.

For more information on M27, check out Wikipedia: http://en.wikipedia.org/wiki/Messier_27

Copyright © 2013 David Allan Galbraith
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Finding Comet C/2012 S1 (ISON)

As I noted on a post a couple of days ago, I’ve recently joined the Sierra Stars Observatory Network to try some deep space imaging with research-grade telescopes. I thought I’d see if I could use a 37 cm telescope on the SSON to photograph a comet that’s on its way into the inner solar system, called Comet C/2012 S1 (ISON). This comet is predicted to be visible to the naked eye in November of 2013. It’s possible it will be a very spectacular sight.

Right now it’s much more humble from earth’s position. Various web sites are listing quantitative observations already of the brightness of this comet, describing it as between magnitudes 15 and 16 – in other words, it’s really, really faint.

Anyway, the SSON system makes use of an extensive database of the locations of deep sky objects to allow users to photograph them robotically. I sent in requests for two exposures of the comet of 300 seconds each (without any filters) on the University of Iowa’s Rigel telescope in southern Arizona, two days apart. It took a while to pin down the location of the comet in each of the two resulting images. I had to use software that allowed me to determine the position of objects on each image, but there it was! In this image I’ve pasted the 16 April 2013 image onto the background of the 14 April image, so that both are visible in one frame. I’ve added the little cross-hairs to indicate which wee blob is actually the comet. The added text is from the “FITS” files that are sent down by the telescope’s computer. The first line is the date and local time at the start of each 300 second exposure. The second line is the Right Ascension of the comet at that time (the coordinate corresponding to longitude in equatorial coordinates, expressed in hours, minutes, and seconds); the third is the Declination of the comet (the coordinate corresponding to latitude, or degrees, minutes, and seconds above the celestial equator).

Comet C/2012 S1 (ISON) photographed on 14 and 16 April 2013 with the University of Iowa's Rigel Telescope.

Comet C/2012 S1 (ISON) photographed on 14 April 2013 (lower) and 16 April 2013 (upper) with the University of Iowa’s 37 cm Rigel Telescope. The photos were set up over the Sierra Stars Observatory Network (SSON). Taken as separate images and made into a mosaic with Photoshop Elements. The inset image in the lower right is the 14 April image without any reduction in scale if the whole image is displayed at 800 pixels across.

I was pretty excited to actually find the comet in these two frames! The moon was a bit of a problem on the 16th. It was not too far from the location of the comet in the sky that night, and as a result there’s some background glow on the later of the two frames (mostly cropped out of this composite image).

It will be interesting to observe the comet again in coming days and weeks, to see how much it’s growing in size and brightness as it comes into the inner solar system. In the inset on the image above you can just about make out that there’s already a tail visible. Images taken with larger telescopes are already showing a distinct tail.

The images that you can take for yourself with the telescopes on the Sierra Stars Observatory Network (http://www.sierrastars.com) are carefully calibrated; if you wanted to use them for research purposes it would certainly be possible. For now I’m content to just see what I can do in terms of finding interesting objects and learning more about processing and improving the resulting images.

Copyright © 2013 David Allan Galbraith