The M87 Chain and the Pixinsight Zone System

One of the greatest euphemisms in the world has to be the phrase `learning experience'. How often do we sugar-coat our mistakes by calling them `learning experiences'? I'm sure I've done it many times. This image provides an example, but in this case there's a bit more to it than that...

A portion of the Virgo galaxy cluster, with the giant elliptical galaxy M87 at top left, and part of `Markarian's Chain' of galaxies at right. Click the image for a larger version, or click here for full size.

Data Acquisition: Making the best of a bad situation

A few weeks ago, I was doing some backyard imaging, and the Virgo galaxy cluster seemed like the logical choice. Having shot a luminance image of the Leo Triplet not long before, I decided to do another one-night stand, with just luminance, but this time I wanted to shoot `Downtown Virgo'. (The origins of that term and its enthusiastic usage seem to go back to Jay Freeman and Jamie Dillon, two highly-accomplished Bay Area visual observers.) Specifically, I wanted to shoot the portion of the Virgo cluster called Markarian's Chain. It's a standard target, since it comprises a pretty, arc-ing chain of galaxies that stretch from M84 and M86 towards M88. Almost everyone works on an image of Markarian's Chain at some point. By planning it out in SkySafari Pro 3 on my iPad, I could see that if I rotated my camera just right, I could frame most of the chain pretty nicely on my ST-8300 sensor, using my ED80 f/7.5 refractor.

One thought nagged at me, though... What about conventions? As in sign conventions and angle conventions? Sky Safari Pro 3 has a really nice slider tool for rotating the position angle of one's field-of-view overlay, relative to the sky. This allowed me to plan my framing really easily. And when I'm imaging, I can download a frame from the camera, and use MaximDL to plate-solve it, which gives me the image's position angle on the sky. This is really handy, but.... what if these two pieces of software use different conventions for specifying the position angle? Hmm. I could wind up with a frame that's rotated 90 degrees from what I expect.

So, it wasn't a great shock when that's exactly what happened. Here's the framing I had planned on my iPad:

Here's how things actually worked out, since the two pieces of software treated the position angle differently:

Hrm. Rargh. What to do? I could have rotated my camera 90 degrees, but that would mean refocusing and probably re-doing the GOTO alignment. Given the couple of hours available for shooting Downtown Virgo before it went behind some trees, I didn't want to do that. So, I panned around in SSP 3 and looked for an alternative framing. Here's what I wound up with:

That seemed like the best compromise, since it caught part of Markarian's Chain, and included the giant elliptical galaxy M87, the real `heart' of the Virgo cluster. I shot a couple of hours of luminance (in 5-minute subexposures), and called it a night.

Processing: Pixinsight meets the Astro Zone System

A few weeks later, I had a little time to sit down with the data, and after using the very handy new preprocessing script in Pixinsight, I saw the following preliminary result (this is a closeup of two of the galaxies in the Chain):

Autostretched image of two galaxies in Markarian's Chain.

It's probably worth explaining what I mean by an `autostretched' image (also sometimes called an AutoSTF'ed image amongst Pixinsight enthusiasts). PI has a tool called `Screen Transfer Function' (STF), which stretches the brightness values of the image's pixels, solely for the purpose of displaying the image on the screen. It doesn't change the original pixel values in the image file, but it basically creates a temporary copy of the image to display on the screen, with the brightnesses changed so as to make the dim parts of the image more visible. The STF tool has a `Auto' button, which creates an image that nicely shows `what you got'. (I used one of these AutoSTF'ed images in my annotated Leo Triplet posting.) Such an image, though, usually doesn't make for a very pretty picture, since it shows just how noisy the dim background areas and dim parts of your target look. That graininess is a combination of instrumental noise and the eponymous photon shot noise (the latter coming from both the target objects and from the sky.)

At this point, my big goal was to do some noise reduction, and try to make the noisy, grainy-looking parts of the image look a little better. In this I was aided by Jordi Gallego's new presentation on noise reduction in PI. There's a lot of good information in this document, but I was particularly intrigued Jordi's slides 51 through 53, particularly #53. In this slide, he shows that one can make masks for applying different noise reduction settings to different parts of the image, such as:

• The dark background sky, which has the lowest signal-to-noise ratio (SNR), and is thus the `grainiest'-looking part of the image.
• The dim parts of the deep-sky object(s), which have fairly low SNRs, and thus mostly need smoothing and noise reduction.
• The bright parts of the deep-sky object(s), which have high SNRs, and thus can tolerate some sharpening, such as through deconvolution.

Aha! This is basically the same concept as Ron Wodaski's Astro Zone System. I borrowed a copy of this book from a fellow Bay Area observer a couple of years ago, and found it to be very interesting. Sadly, the book has been out of print for some time, but I was one of the lucky folks at the 2011 Advanced Imaging Conference who managed to get one of the copies Ron gave away. (Thanks, Ron!)

After a little fiddling around, I realized that PI's Range Selection tool works best on images that have already been stretched into a nonlinear state, so I made a copy of the image, applied its AutoSTF settings to Histogram Transformation, and applied that to the copy. I then used Range Selection on this stretched copy.

First, I made a mask that covered up the stars and galaxies, leaving only the dark background sky to work on:

After a little fiddling around, I stumbled on some settings in Multiscale Median Transform that smoothed the background reasonably well:

I was pleased with this result! It's not perfectly smooth, but I'm calling this a win, so far. Then, I made a mask for the `mid-SNR' zone, which included the fainter outer parts of the galaxies:

And then, by pulling back on my MMT noise reduction settings, I was able to smooth those areas somewhat. Next I made a mask to isolate the cores of the galaxies, for sharpening via Deconvolution:

After mid-SNR-range smoothing and high-SNR-range deconvolution, I had this image:

The brightness levels you see here are `Auto-STF' levels, and even with the noise reduction, they're not really good for posting on the web. So, since the image was still at a linear stage (i.e. not really brightness-stretched yet), it was time for a Histogram Transformation, some star shrinking, and a horizontal flip to match the correct appearance of this area on the sky:

Room for Improvement:

I think this was a good proof-of-concept project, for the Range Selection / `Pixinsight Zone System' approach. My masks could use some work, though. When I examine the image closely, I can see that some of the dim parts of the galaxies got left out of the masking process. Also, the various processing steps left an artificial ring around M87. There really are such things as ring galaxies, but M87 isn't one of them. I'm very interested in refining my touch with Range Selection, and to trying out the new Adaptive Stretch tool! A week or so after shooting these data, I managed to shoot Markarian's Chain with proper framing, and so we'll see how things go with this new data set.

Annotation Script - What did I capture in my image?

Here's another version of the Leo Triplet (luminance) image. This one has been overlaid with the results of Andres Pozo's plate-solving and annotation scripts. Thanks to Andres's hard work, I can take my image and `see what I captured':

The Leo Triplet, annotated. Click on the image for a larger version, or click here for full size.

Andres started a thread in the Pixinsight Forum back in March (see the link listed in the previous paragraph), and he's posted a number of updates to his scripts since the thread started. His scripts do two very useful things:

1) One script `plate-solves' the image. This basically means figuring what part of the sky has been captured in the image, and assigning a set of on-sky coordinates to each pixel in the image. (This is nicely described in Chapter 9 of Berry and Burnell.) By attaching metadata to the image (as part of something called the `FITS header'), the plate-solving script allows the annotation script to look at the image, and figure out the exact location (on the sky) of each pixel in the image.

2) The next script looks up objects in a set of online catalogues, and overlays symbols and coordinate lines on the image.

The whole thing is very slick, and after only one false start, I got Andres's scripts to work. The Annotation script overlaid the locations of objects from these three catalogues:

The Messier catalogue: This is a list of nebulous-looking objects in the sky, compiled by the 18th-century comet hunter Charles Messier. It's a list of roughly 100 bright deep-sky objects visible from mid-northern latitudes. The two big, bright galaxies in my image are Messier objects 65 and 66.

The NGC and IC catalogues: These catalogues were first compiled by J.L.E. Dreyer in the 19th century, and they list thousands of objects beyond the Messier catalogue. The great 18th-19th-century astronomer William Herschel found about 2500 of the objects that provided the initial `nucleus' of the NGC. Amazingly, Steve Gottlieb (a Bay Area observer) and others have been double-checking the NGC/IC catalogues visually!

The Principal Galaxy Catalogue: This list of about 70,000 galaxies was published by a group of French astronomers in the 1980s. Many of the faint `field galaxies' that an imager is likely to capture will turn out to have PGC designations.

Looking at my Leo Triplet image, it seems like I got pretty much all of the overlaid PGC galaxies. In other images that I've shot recently, about which more anon, the boundary between `what I got' and `what I couldn't get' occurs in the PGC galaxies. This isn't really surprising, since a large catalogue like the PGC includes objects that span a large range of apparent brightnesses. If I had more time, it would be interesting to compile lists of the PGC galaxies that I did and didn't get, so as to characterize the depth of my image. How deep can a 3-inch f/7.5 refractor with an amateur CCD camera go in a night or two? Andres's script offers a way of estimating this.

I'm pleasantly surprised at how much I enjoy looking at the image with the annotation overlays. They give me a sense of what's in this part of the sky, and somehow they add depth and richness to the image. Naturally, the `pretty picture' version of an image probably shouldn't have annotations like this on it, but it's nice to be able to make an annotated version easily. The two versions complement each other, I think.

The Silver Coin galaxy

Just a quick image posting today... I don't have as much time as I'd like to write about this object.

I was going through some files the other day, and I realized I had this image of NGC 253, the `Silver Coin' galaxy, sitting on my hard drive. Might as well add it to Photon Shot Noise!

At the moment, I don't have a lot of information about the details of how I acquired it and processed it. I definitely used my Orion ED80 refractor, and I was using a camera with the Kodak 8300 monochrome chip, shooting through a Luminance filter. I think the subexposures were 15 minutes long. I was using my Orion Sirius mount (which has since been retired for solar-observing duty at school), and I was pleasantly surprised that my polar alignment and autoguiding were good enough for 15-minute subs. I seem to recall acquiring the data on one or more cold nights at a Bay Area hilltop observing site, sometime in the last year or two.

As with the acquisition, the details of processing are a bit hazy at the moment. I'm fairly sure I processed this in Pixinsight, and I recall being pleased at how much detail I was able to bring out. This is due to the reasonably good SNR, which came from taking lots of relatively long subexposures over one or two nights. I either used Deconvolution for sharpening, or perhaps an ATWT-based sharpening and noise-reduction workflow.

If I recall correctly, one of the nice things about NGC 253 is its relatively sharp `edge'. It doesn't have much of an extended, low-surface-brightness halo around it, at least not in my subexposures. As a result, I wasn't tormented by the desire to bring out lots of surrounding faint stuff. Such faint stuff around a galaxy is often hard to make look decent, since it requires either a mountain of exposure time, or a miraculous touch with the noise-reduction routines. I seem to recall that NGC 253 pretty much ends where you see it ending here, and so I didn't have any significant `halo struggles'.

Ring(s) of Fire

I just got back from a great trip to see the 2012 annular eclipse. It was everything I'd hoped for! Nearly all of us in the northern California part of the path got lucky, and we saw the eclipse through mostly-clear skies. I've been interested in eclipses since 1984 (the partial version of which I saw during high school), and this was my first `central' eclipse. I'm still waiting to see a total eclipse - that'll be 2017, with a little luck - but this was a great `dry run' for that experience, I hope.

It might seem surprising that an aspiring astro-imager would only shoot a few iPhone images of the eclipse, but I decided to keep things simple and make this primarily a visual-observing experience. I knew a lot of other people would acquire great images and image sequences, so I decided to just observe the Sun through a safely filtered telescope, and to soak in the weirdness of the light all around me.

One of the highlights of the eclipse were the crescent- and ring-shaped images of the Sun that were cast onto the house where I observed the eclipse. These were produced by very small gaps between the leaves in nearby trees, which acted like hundreds of pinhole-projection setups. As the first partial phase got  underway, we noticed a few crescents:

As the Moon moved farther across the face of the Sun, the crescents became more obvious, and we started to notice the large ones cast by trees in a neighboring yard:

Even though annularity only lasted about 4 minutes, it was worth walking around the yard to see and photograph the rings shown in the first image. Having read Norm Sperling's piece about his `8-second law' for total eclipses, I knew it would be worth doing more than just staring at the annulus through the telescope. Also, I was happy to share the view through the telescope with some family, friends, and neighbors. Moving around, looking at the tree-projected images, looking through the telescope, and savoring the weird and wonderfully dim eclipse light, made the period of annularity really fun and memorable.

The thing I was most interested in, before the eclipse, was what the illumination around me would look like. I knew it wouldn't get nearly as dark as during a total eclipse, and from what I've read, that's not really quite a `nighttime' experience. It sounds like a total eclipse produces its own unique brand of day-meets-night. The light cast by the `ring of fire' Sun was wonderfully strange. The simplest way to describe it would be `much dimmer than usual', but that hardly says anything. I keep finding myself wanting to say things like `odd', `strange', and `weird', but in a good way. Perhaps the most noticeable thing was the lack of heat from the Sun. Prior to first contact, it was a pretty hot day, around 90F (about 32C). I was glad the backyard observing site had large shady areas in which to set up my telescope, before putting it in the sunlight. During the first part of the first partial phase, it was hot! But during the deep-crescent and annular stages, I'd describe it like this: `A warm-looking cool light'. The light didn't have a `cool color' like blue, but it *felt* cool, compared the hot late afternoon we'd been experiencing a short time before.

If there's one imaging project I wish I'd undertaken, it would have been to try and photograph the light on the scene around me. I wish I could have used a DSLR on a tripod, running through a variety of exposure settings, with a grey card and a color card in the scene, to try and reproduce the appearance of the `eclipse light'. If I do imaging during a future eclipse, like 2017, I think that's what I'd like to do. I'll rely on others to image the Sun itself.

All in all, the 2012 annular eclipse was everything I could have hoped for. We sweated the weather all weekend, but it worked out just fine. A ridge of high pressure allowed me to image some galaxies and M5 on the Friday night (more on that anon), and to observe the sky visually on the Saturday night. On eclipse day, we got lucky! There was a bit of high cirrus during annularity, but it didn't materially affect the views or the experience. And during the last part of the second partial phase, thick high clouds rolled in for good and all - what luck! I plan to be as flexible and mobile as possible in 2017, but this time around, everything was great. I was glad to hear that so many other astro-friends had great experiences, too. Here's to the shadow of the Moon!

The (Leo) Luminance Triplet

For such a dry winter, California didn't have a lot of imaging-quality skies in early 2012. We had some late-season rain and mountain snow, which was good for our hydro balance, but not so good for the spring galaxy season. I finally got out in mid-May, and spent a couple of nights shooting M65, M66, and NGC 3628, otherwise known as the Leo Triplet. Here's the result, sized for a 15" MacBook Pro screen:

This is what's known as a `luminance' image, which means it was shot with a black-and-white (or `monochrome') CCD camera, through a clear (or `luminance') filter. In order to make a color image, I'll need to shoot it through 2 or 3 color filters. If all goes well, I hope to shoot it through Red, Green, and Blue filters before the spring season slips away. The subexposures for this image were each 5 minutes long, and I shot about 50 of them over two nights, for a total exposure time of about 4 hours. As always, the imaging scope was an Orion ED80 f/7.5 semi-apo refractor.

This was also the inaugural imaging run for my new (to me) Losmandy G-11 mount. I got a great deal on it from a fellow Bay Area imager, and I spent the April dark-moon period learning some of the ins and outs. I feel like I can polar align, acquire targets with the Gemini 1 (Level 4) goto system, and I can get pretty good autoguiding. During the nights when I shot these luminance frames, the RMS error on my guider corrections was running about 1/2 pixel in both RA and Dec.

I processed this image in Pixinsight, making use of the new Batch Preprocessing script. Very handy! Many thanks to the folks who wrote that script. Also many thanks to Mike Schuster for writing the PSF Estimation script, which auto-picked hundreds of stars and gave me the parameters of the point-spread function, which I used for Richardson-Lucy deconvolution. (Deconvolution is a sharpening routine that I used to bring out some of the details in the galaxies.) The hardest part of the whole processing workflow was the noise reduction, which I did with Multiscale Median Transform. Once I had the noise somewhat beaten down, I could get a halfway-decent stretched image from the Histogram Transformation. I did a bit of HDR Median Transform, but not nearly as much as I might use on, say, a large bright nebula.

I hope to be able to get out and shoot some RGB color data if I'm lucky; it would be nice to add color to these galaxies!

From the realm of the galaxies to the microcosm: A thin-section gigapan

I've been looking forward to posting this image (and linking to the corresponding GigaPan) for a long time.

(Click here for the zoomable GigaPan mosaic at gigapan.org)

The image in today's post is a 156-panel mosaic of something called a thin section; it's a `geology thing', in contrast to the `astronomy things' that I've been imaging so far. Basically, it's a piece of rock (from Vermont, in this case) that's been ground so thin, light will shine through it. When viewed with the right kind of microscope, thin sections commonly show bright colors, along with variations in light-vs-dark from grain to grain. The area shown in this image is about 12mm by 18mm. This thin section is one of a set that have been at De Anza College for many years. Students in our introductory geology course look at these thin sections when they're learning to identify the different rock textures. I don't know when these thin sections were made, but I'd guess they date from the 1960s or 1970s

I've written a more detailed explanation in the `About This GigaPan' notes - if you're interested, you can scroll down below the panorama, and my notes are below the camera and image information.

Acquiring the image data:

Instead of a telescope, I had to use a microscope. I used a `trinocular petrographic microscope' that I got from The Microscope Store a few years back, when I was just dying to have my own petrographic microscope. The scope is `trinocular' because not only does it have a binocular viewer for viewing the magnified image with one's eyes, but it has a third port for attaching a camera.

For photographing thin sections, I used a Canon 20D DSLR camera. This is the same one I used when I started digital astro-imaging, several years back. To attach it to the microscope, I kludged an Orion 1.25" eyepiece-projection adapter, which happily fit right over the non-telescope-sized microscope eyepiece quite nicely! The image focuses on the camera sensor, and since it's a DSLR, I can check focus and framing right through the camera viewfinder.

The basic idea behind acquiring data for an image of this type is to shoot lots of adjacent frames, with some overlap. In that sense, it's like a large astronomical mosaic. However, since each frame only takes a fraction of a second to shoot, I can take hundreds of frames. The big difference between deep-sky imaging and microscopic imaging is that I have a nice bright light source (i.e. an incandescent bulb built into the scope). It's much easier to achieve a high signal-to-noise ratio that way!

The thin section is a small glass slide, and I moved the slide between frames. This was accomplished by means of a small slide positioner, which holds the slide and moves in two directions when I turn some small knobs. The positioner has a vernier scale on each axis, so I can make a precise 1.5-mm movement between adjacent frames in a given row, and then move 1mm between rows. This gives the GigaPan Stitch software enough overlap to work with.

Preliminary data processing:

I used Adobe Photoshop CS4 to batch-process the raw 16-bit CR2 files that came off of the camera. I used CS4's Camera Raw module to take out some slight chromatic aberration, and after converting the images to 8-bit JPEG format, I did a bit of sharpening and color saturation. The GigaPan stitching process seems to have desaturated the image a bit. Perhaps I should pre-saturate each image a bit more.

Assembling the mosaic:

This couldn't have been easier! I just turned GigaPan Stitch loose on the image files, and it made a mosaic, which is about 30,000 pixels wide! Simplicity itself. I ran the stitcher on a Mac Pro computer, which made short work of the operation. I had heard that GigaPans can take all night to run, but the Mac Pro banged this sucker out in under 15 minutes. Somewhere, Steve Jobs is smiling.


An Unsung Hero:

Somewhere in China is the real hero of this little technological story. The microscope I used is a Chinese-made import, and it's a mixed bag of build quality. Some things on the scope are perfectly serviceable, and other things could stand to be better. Centration of the objective lenses (something like collimating a telescope) is hard to do, and the objectives don't stay centered for very long. I took the whole objective turret apart, and saw that certain detents in a metal part appeared to have been cut into the metal rather haphazardly. The binocular viewer leaves something to be desired, too - it has some annoying internal reflections, and gives a partially-cross-polarized view even when the `analyzer' (one of the polarizing filters) is out of the optical path. However, this microscope really shines in one important area - the flatness and sharpness of the image field. Man, that thing is flat! By that I mean that there are almost no visible aberrations from the center of the field to the edge, at least in the low-power objective. And there are very few diffraction artifacts visible on high-contrast edge features, which is more than I can say for a more-expensive Japanese-made microscope at school, even when it's adjusted for Kohler illumination. (Sorry for this microscope geekery, interested readers may want to look at the Nikon or Olympus microscopy websites.)

Who knows if I'm correct in my speculations, but I can't help imagining an optical designer in China somewhere, making those objectives as perfect as possible, out of love for the craft of optical design. Somehow or another, they made those things so as to deliver a really remarkable level of performance (at least as judged by my eye), despite the relatively low price point. Whether by luck or by design, the image quality of those objectives largely makes up for the deficiencies in other parts of the microscope.

A Dream of Automation:

As I described in the `About This GigaPan' notes, I have this dream of motorizing the stage-positioner controls, so as to be able to automate the acquisition of the image data. I'd love to be busily grading papers, or surfing the web, or processing images, while the microscope and a computer are robotically churning out the data for another enormo-mosaic. It's quite a bit like my dream of having a robo-focus unit for my telescope, so that I could acquire image data automatically while doing visual observing. One can dream!

The Orion nebula: Reworking some year-old data

If you've not yet had the opportunity to look at M42, the great Orion nebula, through a telescope, you owe it to yourself to try and find an opportunity to do so. Even though today's entry is part of an `imaging blog', M42 is the kind of object that's beautiful any way you look at it. As long as you've got a clear sky, and are (hopefully) away from city lights, you can see this nearby star-forming complex in some way, regardless of the gear you've got.

I just now spent a moony evening reworking some unbinned R, G, and B data that I shot about a year ago. Every winter, it's the same old routine: Try to get some decent data on M42. Something always gets in the way, though. In early 2011, it was bad weather and camera issues... a story for another time. I managed to shoot some unbinned L, R, G, and B data, but not a heck of a lot. To the best of my memory, the data for this image don't amount to much more than several hours total. Since it's now February, and I'm not 100% sure if I'll get in a decent M42 dataset in 2012, I thought I'd fool around with this old stuff from last year. See if I could make something semi-presentable.

After an evening spent in front of the computer, I happened to go outside, and as I was walking back in, I looked up, and there he was: Orion, the hunter. The constellation was just passing across the meridian, with the bright gibbous moon due north of it. Even with lights in my eyes, and under a city sky, I could make out the bright stars that delineate the pattern: Betelgeuse, Rigel, Bellatrix, Saiph, Alnitak, Alnilam, Mintaka. And there was the sword of Orion, with the middle `star' being M42. This object is so bright that it (or at least the stars in and around it) can be seen under almost any sky, it seems.

Unlike most deep-sky objects, M42 is worth looking at with virtually any optical instrument. The belt and sword of Orion are great in binoculars. Small telescopes show the nebulosity. Large telescopes under dark skies provide one of the few `imaging-like' experiences in visual observing. A greenish color can even be seen in the brightest part of the nebula, in a big scope. The details just go on for days and days.

As an imaging project, M42 presents an almost limitless field of challenges and rewards. With modest equipment and short exposures, one can still get something. Advanced imagers have gotten some incredible results.

Processing in Pixinsight:

This image certainly isn't incredible, but I'm glad that I was able to squeeze a bit of detail out of such data as I had. I spent a fair amount of time on this in Pixinsight, and eventually I gave up on trying to combine the luminance data with the color data. Both my RGB image and my Luminance image were the result of high-dynamic range combinations, for which I'd shot long- and short-exposure frames. Matching the histogram from the L image to the histogram from the RGB image seemed to be taking forever, with little end in sight. I bailed and just went for the RGB.

Getting a good color balance was really tricky, and I just couldn't get it quite right. The stars in the linear image had all sorts of blue and cyan issues, and by the time I got them to look semi-normal, the blue color in the nebula was pretty well gone. I could have (and should have) worked that problem harder, but since this was a `let's see what we can get out of this stuff without too much struggle' project, I didn't sweat it that hard.

I did a bit of Richardson-Lucy deconvolution while the image was still linear, but nothing drastic. I would have liked to have gotten a better sharpening result, but I found that I kept getting bright `wormy' artifacts if I wasn't careful. I think that a really good deconvolution would be pretty substantial project, even with the help of Dynamic PSF.

After histogram stretching, I had to spend a fair amount of time finding the right parameters for an application of HDR Multiscale Transform, to knock down the over-brightness of the area around the Trapezium. Once I got that area tamed, it was rather washed out, as usual. Some additional luminance masking and an extra saturation boost in that area helped a bit, although it left some purple haze around the Trapezium stars.

There's plenty of room for improvement in this image, but I'm glad that I can at least post some sort of M42 image. I hardly feel like `an imager' without one. With a little luck, maybe I can finally get a decent set of data later this month and in March. It would be nice to really go deep on this thing, and under good seeing. We'll see how it goes!

As per usual, there's an amazing image of the object from the Hubble Space Telescope.