Trying LRGB Colour

Our eyes see a composite image of the world around us. If your vision is “normal” the colours you see every day are composed of four type of information: brightness, plus red, yellow, and blue information, each coming into your brain from difference cells in your retinas.

Colour images taken with large telescopes are assembled from the same four channels. Advanced cameras used in astrophotography are monochrome, or “black and white.” Colour comes into these images through combining multiple exposures, some done with red filters, blue filters, green filters, and some done with no colour filters at all. The result is an “LRGB” or Luminance-Red-Green-Blue image.

I tried this process recently by using (again) the Sierra Stars Observatory’s 61 cm telescope in California, accessed over the internet on the Sierra Stars Observatory Network (see my posting from 21 April 2013 for monochrome results). Combining monochrome images with others taken with red, green, and blue filters, using software called fitswork, and the tuning things a little in Photoshop Elements, I was thrilled to see an attractive image of Messier 51, the Whirlpool Galaxy, materialize! Might be a bit heavy on the blue channel, but the arms of M51a are known for regions of hot, young stars, and its companion, M51b, is redder because of a higher number of older, redder stars.

M51 LRGB

Messier 51, the Whirlpool Galaxy in Ursa Major, imaged using the 61 cm Sierra Stars Observatory in California. A composite colour image prepared by using monochrome images captured on 20 April 2013 and additional exposures for red, green, and blue information on 22 April 2013.

Copyright © 2013 David Allan Galbraith
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Why “Post-Processing” Matters

We’re very used to having great photos delivered by our digital cameras these days. Point and shoot is the order of the day. Astrophotography is a little different, because of the tiny amount of light involved, and the specialized, custom nature of the photographic and telescope equipment.

I thought an example might indicate what I mean. The image below is of Bode’s Galaxy, M81, which is a large, bright galaxy close to us. I set up the Rigel 37 cm telescope in the Sierra Stars Observatory Network (http://www.sierrastars.com) to take five shots of M81, each one being a five-minute exposure. I then used software to combine the images, and to adjust the contrast and brightness of the resulting “stacked” image. These sorts of images are taken with monochrome cameras – or black and white – that are sensitive to all frequencies of visible light.

Here’s what the “tuned up” image of M81 looks like:

m81

A processed image of Bode’s Galaxy, M81, created by stacking five 300 second exposures taken with the 37 cm Rigel Telescope in Arizona. This bright galaxy is relatively close to earth and can be located on a clear night with binoculars or a small telescope in the constellation Ursa Major.

Here’s one of the five original 300 second exposures, displayed more or less as it looked when it was delivered by the telescope and camera. The fine details of the finished image are in there, but in order to see them the brightness and contrast needs to be “stretched” a bit. This process changes the relationship between the light values recorded by the camera and the shade of gray displayed on the image, to show the fainter light of the outer edges of the galaxy.

M81 unpriocessed

An unproccessed frame of M81, one of five taken as a 300 second exposure without filters on the Rigel Telescope in Arizona on the evening of 15 April 2013.

I’m feeling a little more confident about monochrome images now, but I still need to update my computer for doing this sort of “Post-Processing.” My next step will be to take some images of M81 and other objects with these remote telescopes using colour filters. By shooting images with colour filters on monochrome cameras like those on this sort of telesope, you can reconstruct a colour picture in post-processing.

Copyright © 2013 David Allan Galbraith

Peak at the Whirlpool (Galaxy, that is)

For International Astronomy Day (20 April) 2013, I decided to try the 61 cm f/10 Optical Mechanics Nighthawk CC06 Cassegrain telescope at the Sierra Stars Observatory in southern California to photograph M51, the Whirlpool Galaxy. M51 is relatively close to earth as galaxies go, and is a beautiful deep space object. It actually consists of two colliding galaxies.

The Sierra Stars Observatory is one of three observatories in the Sierra Stars Observatory Network, or SSON (http://www.sierrastars.com). I programmed the observations on the afternoon of the 19th of April and was delighted to see that the telescope had been able to make the photographs overnight, ready to download for the 20th.

To make this monochrome image, I took three 300 second exposures of M51 with the 61 cm telescope, and then used free software called FITSWork (http://www.fitswork.de/software/softw_en.php) to merge the three FITS-format images files. FITS files include both the image produced by an astronomical telescope camera and all of the data about the telescope’s position during the exposure. The combination of images reduces noise produced by the camera and effectively turns the result into a 900 second exposure. I then tuned up the resulting image for contrast and brightness by adjusting “levels” with Photoshop Elements 6. I feel I’m getting a little better at image processing, but I still have a lot to learn! It’s fun, though, and the remote observatory option is a way of taking your own images even when the local weather makes any stargazing impossible.

The Whirlpool Galaxy (M51)

The Whirlpool Galaxy (M51) photographed on 20 April 2013 with the 61 cm Sierra Stars Observatory.

M51 is located just south of Alkaid, the eastern-most star in the “handle” of the Big Dipper (formally named Eta Ursae Majoris). It is relatively bright and can be located with binoculars on a dark, clear night.

Because this is actually two interacting galaxies, M51 has a lot of red star-forming areas similar to the giant molecular cloud in Orion in our galaxy. Some are visible in this image as faint “knots” of light along the spiral arms of the galaxy. I’ll try imaging the galaxy with colour filters soon. These separate images can then be combined with the monochrome images I’ve already taken to produce a colour rendering. There’s a nice write-up on M51 on Wikipedia at: http://en.wikipedia.org/wiki/Messier_51.

The Whirlpool Galaxy is quite far north in the sky, and just about doesn’t set from the perspective of southern Ontario. It will certainly be on my list to see and try to photography myself once the weather and my availability make it possible.

Copyright © 2013 David Allan Galbraith

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

Try Something New: Rent an Observatory for a Few Minutes

(Updated 21 April 2013)

Observatories can be very, very expensive undertakings. Some amateur astronomers have large disposable incomes and can buy and set up larger scopes – and even buy land for their own observatories. For others (I think the silent majority) using a large telescope can seem like an impossible dream.

Not any more.

It’s possible now to effectively rent a bit of time on an observatory from a distance, for either photographic purposes or even to undertake original research. Essentially, it`s astronomy time-share.

I’ve been interesting in trying this sort of thing for some time. You can find several services on-line that will let you join up and, from your home computer, direct a large telescope to do what you’d like it to do.

There are several approaches that these services take. Some are very consumer-oriented, such as the SLOOH Space Camera service (http://www.slooh.com/). SLOOH provides a lot of “added value” in astronomy, such as programmed events. Some other services allow users to take control of remote telescopes in real-time. With these services you need to be able to use a high-speed internet link and sophisticated software on your own computer to take control of all aspects of the distant observatory.

I’ve recently joined the Sierra Stars Observatory Network (SSON; http://www.sierrastars.com), which has a unique approach. The SSON consists of three different telescopes in the south-west USA, linked together with a scheduling service. The telescopes belong to educational or academic institutions, and are set up with sophisticated cameras. all that a user needs to do is to decide what to image. It’s not necessary – in fact it’s not possible – to run these telescopes yourself.

Using a very easy web-based form, users of SSON submit jobs to the telescope of their choice. The system operator cues up targets for the completely robotic observatory, and their computer takes care of the rest of it. When the images have been shot you’re sent an email message. You can then download the completed files from an FTP site. Not very hands-on, but very efficient and precise. The on-line scheduling system includes drop-down menus of thousands of celestial objects.

Membership programs like SSON can give you access to major, research-grade telescopes for a very small investment. An introductory membership package for SSON is $50 US, which gives you 83 credits. Subsequent credits are $1 each, unless you buy a lot of time, in which case the rate drops a bit. Charges are applied only for actual use of the telescope cameras – so if you take a five-minute exposure, you get charged only for that time. The rates run from about $1 per minute (actually $50 per hour) for the 37 cm Rigel telescope to $160 per hour for the 81 cm Mt. Lemon Sky Centre instrument.

There are some remote astronomy services that are less expensive per hour, but what convinced me to try SSON is the ease of submitting a request for imaging, and the fact that this is supporting research and educational telescopes.

I submitted two types of jobs to SSON to try it out this week. I sent in instructions to photograph M81, a lovely galaxy in Ursa Major, and also to try a photo of Comet S/2012 S4 (ISON), which might turn out to be a beautiful comet visible to the naked eye later this year. The observatory system ran my requests for exposure overnight between 13 and 14 April 2013. Here are two of the images taken by the Rigel 37 cm telescope, part of the SSON.

m81

My first shot of M81, a bright galaxy in Ursa Major, made by stacking several short images taken with the University of Iowa’s Rigel telescope… from my apartment in Hamilton, Ontario. This is pretty crummy; I still have a lot to learn about processing, and longer shots are coming, too. A start, though. M81 is a beautiful and very bright galaxy. Longer, better-planned exposures and better image processing will give nicer images in the future. This was produced by stacking 9 individual frames exposed without colour filters: 3×30 sec, 3×60 sec and 3×120 sec, for a total of 630 seconds. I am trying a second run of 5×300 seconds (1,500 seconds). I hope this will reveal some of the finer, more distance lanes of stars that extend out from M81. For those who have more experience with this than I, rest assured that the FITS files that come from this system are indeed 16 bit. This was a crude stacking attempt.

I was encouraged by the first shots of M81, but I didn’t set up the observatory to make very long exposures. The longest you can shoot on SSON is a 300 second individual exposure. I’ve re-programmed the 37 cm Rigel telescope for five exposures of 300 seconds each, for a total of 25 minutes of light-gathering. I hope to have these new frames in the next few days and will post updates.

Updated 21 April 2013: Here’s a much better version of the M81 image, prepared on the 21st from the second run of five 300 second exposures and a better job of managing the post-processing:

m81

Bodes Galaxy, M81, imaged using the 37 cm Rigel telescope on SSON by taking five 300 second exposures and combining them.

I did get a good-looking frame from the single request I sent for a photo of Comet C/2012 S1 (ISON), but I’m not 100% sure I know which object is the comet! I am looking into confirming the identity of the objects in the frame below. As of 16 April, I haven’t confirmed the location yet.

Update 21 April: Here’s the actual interpretation of my image from earlier in the week:

isoncr1

(Updated 21 April 2013) BLUE ARROW: The bright star in the middle of this field is not Comet C/2012 S1 (ISON) – but the comet should be somewhere nearby. In fact, it’s just at the tip of the RED ARROW. Photographed on the night of Saturday 13 April 2013 by the 37 cm Rigel telescope in the SSON. A single 300 second exposure with no filters, and with the guidance system set up to automatically find the comet.

Once I have a bit more of a handle on things like exposure times, I’ll also start shooting with colour filters. For now, I`m just trying the cameras without filters – essentially, black & white. I also have a challenge at the computer end of things. I need to upgrade my computer at home to allow running some better image processing software.Nothing can take the place of the thrill of actually seeing a celestial object live through a telescope. However, photography by remote control is also interesting, and accessible. I will be posting more updates on this process as I generate more results.

Copyright © 2013 David Allan Galbraith

April is Astronomy Month

April is astronomy month! Astronomy is the study of everything beyond the earth’s atmosphere (more or less), and it’s a science. It is also a way of understanding and appreciating the beauty and complexity of nature in a way that is both rich with experiences and endlessly fascinating. Many people equate astronomy with telescopes, but it’s not necessary to have a telescope – or even use one – to appreciate the sky and even to photograph its beauty. Here’s a case in point, a photo of the western sky over Lake Huron that captures hundreds of stars too faint to see with the naked eye, and also a famous galaxy and a current comet!

panstarrs20130405

M42 (the Andromeda Galaxy)and Comet C/2011 L4 (PanSTARRS) appear together in the centre of this frame, taken an hour after sunset above Lake Huron on Friday 5 April 2013, from just south of the Pine River, Ontario. A 30 second exposure with a Nikon D7000 camera and Tamron 24-280 mm lens. ISO 800, f/3/5, 24 mm focal length.

For weeks I’ve been hoping to get some photos of Comet C/2011 L4 (PanSTARRS) and I finally got some satisfying shots on the evening of Friday 5 April 2013. I kept track of the clear sky charts for Ontario that day, and, realizing that the comet was getting close to the Andromeda Galaxy (so should be easier to find) and that it was setting soon after sunset in the west, I decided to try shooting from “Ontario’s West Coast” – the shore of Lake Huron. I arrived at about 7 PM at the gracious home of my friends Margaret and Gordon Cale, who gave me a hand on that very cold evening to try seeing what could be seen out over the lake, and we set up a telescope and camera on the shore. I wasn’t ale to get too far with the telescope, but started shooting with the dSLR about a half hour after sunset. I knew approximately where the comet should have been, but I couldn’t see it with my own eyes. I had to rely on time exposures on the camera to pick it out.

It was a cold but beautiful night, and I was able to get several photos of the comet and the Andromeda Galaxy to its left.

A closer view of M42 and Comet PanSTARRS, at 58mm focal length.

A closer view of M42 and Comet PanSTARRS, at 58mm focal length.

My best view so far.

My best view so far of M42 (left smudge) and the comet (right smudge). Many very faint stars show up as short streaks in this 30 second exposure at 65 mm focal length.

To close off this post, here’s another shot taken on Friday 5 April 2013 at Pine River: the magnificent Constellation Orion (with its brightest or second brightest star, depending on circumstances, Betelgeuse, glowing orange at the left) and the brightly overexposed planet Jupiter over the south-western horizon of Lake Huron. Not a bad start for Astronomy Month 2013, but there’s more to come!

Orion and Jupiter.

Orion and Jupiter photographed over the horizon of Lake Huron at about 9:30 PM, 5 April 2013; 30 second exposure, f/3.5, ISO 800 on a Nikon D7000 and Tamron 24-280 mm.

Copyright © David Allan Galbraith 2013

Comet C/2011 L4 (PanSTARRS) – a faint photo at last!

Since early March I’ve been trying to get a look at – or even a photo of – Comet C/2011 L4 (PanStarrs), and I am pleased to note that on the evening of 3 April 2013 I was able to get a faint photo.

The photo below was taken at the Binbrook Conservation Area, south of Hamilton, Ontario, at about 8:20 PM. I was using a Nikon D7000 camera with a Tamron 24-270 zoom lens at 92 mm, with the camera set to ISO 800, exposure 8 seconds, f/5.6. This image is cropped from the centre of the original frame. The comet is the wee blurry bit right in the middle. Toward the top of the frame, 1/3 of the way in from the left, is the Andromeda Galaxy.

Pretty modest, but it’s there. I’ve seen some wonderful recent photos of the comet and galaxy together, too, taken with wide-angle telescopes, but not from our area, where the light of the setting sun is bouncing through several hundred kilometers of atmosphere over central North America!

A faint image of Comet C/2011 L4 (PanSTARRS) photographed with a Nikon D7000 and zoom lens at 92 mm, on the evening of 3 April 2013.

A faint image of Comet C/2011 L4 (PanSTARRS) photographed with a Nikon D7000 and zoom lens at 92 mm, on the evening of 3 April 2013, from just south of Binbrook, Ontario. Really. It’s there. In the middle. Really. Would I lie?

Copyright © 2013 David Allan Galbraith