As promised, last weekend was the first of two excellent dark sky weekends this month. The weather turned out to be perfect for this one as well.

Jane and I went to our old favorite spot off I-10, Chuckwalla Bench, on BLM land south of Joshua Tree in the Colorado [...]]]> Chuckwalla Bench, Colorado Desert, California, 29 October 2011

As promised, last weekend was the first of two excellent dark sky weekends this month. The weather turned out to be perfect for this one as well.

Jane and I went to our old favorite spot off I-10, Chuckwalla Bench, on BLM land south of Joshua Tree in the Colorado Desert. We were joined by Dave Hasenauer and his dob.

Bad news about Red Cloud Rd., the dirt road we take to our favorite spot. The road is sadly in need of some maintenance. Portions of the road are very treacherous with deep ruts and deep sand. We didn’t encounter any problems this trip, but it will be a worry.

We had crystal clear skies all night, with temperatures around 85°F at sunset, dipping close to 50°F in the wee hours.

The evening twilight featured Venus in its new evening apparition setting in the west, Mercury just below, with Jupiter one day after opposition rising in the east.

Early in the evening while spotting satellites, we managed to catch a bright fireball meteor (7:22 p.m.) probably around magnitude -10. I saw a double terminal burst from the fireball, which traced from Cassiopeia through Triangulum. It left a persistent train that was visible for several minutes in binoculars and Dave’s telescope.

Jane even indulged in a little afocal astrophotography capturing some splendid crescent moon shots on her point-and-shoot camera.

I had a couple of “firsts” in my astrophotography accomplishments, doing my first successful drift alignment when my polar alignment was slightly off, and finally successfully capturing useful “flats” for image calibration in the morning twilight.

I also had a brainstorm about how to process the color data from bright targets without data being clipped in the bright areas. With that in mind, first let me revisit my M31-M32-M110 the Great Galaxy in Andromeda from last week, this time in full color.

M31 from 22 Oct. 2011, 4x15 minute exposures

(For all the images, click the image for the full-resolution version.)

And I promised to revisit the Pegasus 1 galaxy cluster, this time giving it an hour of exposure, which it fully deserved. Here’s the full field first.

Pegasus 1 Galaxy Cluster, click for full-resolution.

The one-hour exposure time cuts down the noise nicely, and calibrating it with a good flat field removes the vignetting. Check out this detail from the center of the cluster at full resolution:

Pegasus 1 galaxy cluster detail

Jane was observing this delightful face-on S-shaped spiral galaxy, NGC7479. It was such a small target that I didn’t think my short-focus 4-inch would do it much justice. It turned out to be a delightful crop with lots of detail.

Detail of NGC7479, click for the full field, 15-minute exposure

Another surprisingly good image came from NGC55, a fabulous extended galaxy, so far south in the sky that it’s rare to be seen by northern-hemisphere astronomers. Complicating matters is a light dome from Inland Empire cities that encroaches on our southern horizon. Nevertheless, my 15-minute exposure was worth passing on. The full-resolution shot is very nice with lots of detail.

NGC55, one 15-minute exposure, through a bit of "foreground" light pollution.

Jane also suggested one of her favorite difficult winter visual targets, NGC2359, known as “Thor’s Helmet.” I collected an hour’s worth of photons. Here’s the detail from the center of the field, click for the whole thing.

NGC2359 "Thor's Helmet," 4x15 minute exposures, detail from the center of the field.

I’ve long been fascinated with distant galaxy clusters, and they’re very difficult visual targets. Some find them to be uninteresting photography targets. I opted to try 30 minutes on Abell 426, a massive distant galaxy cluster in Perseus. Here is some detail from the center, but the full field is full of easter eggs.

Detail from the Abell 426 Galaxy Cluster in Perseus. Click for the full field.

My last target of the evening was to be an indulgent treat, the M81-M82 galaxy pair in Ursa Major. My mount battery finally quit just at the end of the second exposure, and morning twilight was about to arrive. A fabulous end to the evening.

M81 the spiral (a.k.a. "Bode's Nebula"), and M82 a peculiar active galaxy, in Ursa Major

This month is blessed with two very good dark sky observing weekends, and we opted to take the first one at a spot we’ve been thinking about for a [...]]]> Observing report, October 22, 2011

Full photo album with site pictures here.

It's very easy to miss this sign from National Trails Highway, the delightful old U.S. Highway 66.

This month is blessed with two very good dark sky observing weekends, and we opted to take the first one at a spot we’ve been thinking about for a couple of years now.

Amboy Crater National Natural Landmark is a volcano crater in California south of I-40, near the town of Amboy, CA. We first visited the site in the spring of 2010. The hike to the crater was fabulous, and the wildflowers were stunning.

Our regular site at Chuckwalla Bench is also a Bureau of Land Management (BLM) site, but unlike Chuckwalla Bench, Amboy Crater features a paved road, pit toilets, parking spots, and picnic tables. Here’s a Google Maps link to the landmark and its facilities.

The downside is that the drive is about 25 miles longer than the trip to Chuckwalla Bench. It makes for about three-and-a-half hours driving each way.

Astronomically, Amboy Crater is one of the darkest locations in the state, with frequently clear skies and sometimes overly hot conditions.

Mojo set up for astrophotography with Amboy Crater in the background.

This past Saturday evening had a nearly perfect forecast. We arrived on a hot dry afternoon, and enjoyed shirt-sleeve or light jacket conditions all evening with a crystal clear sky. We were joined by one other astrophotographer (Robin), and two seasoned visual observers (Cliff and Steve).

My astrophotography is extremely casual. Living in the midst of Los Angeles county, I have no desire, nor is there much reason to, have a permanent observatory of any kind. We’ve both become adept at hauling our portable observatory to locations that offer good dark skies.

Actually we have quite an advantage over astronomers in the eastern half of the U.S. The California deserts offer excellent astronomy, and are within a few hours drive of home.

My telescope is an Astro-Physics Traveler, 105mm aperture (about 4 inches) with a short f/6 focal length. The mount is an Astro-Physics Mach-One GTO “go to” mount, and my camera is an SBIG ST-4000XCM, the perfect camera for my style of casual astrophotography. It’s a “one-shot color” camera, meaning I can shoot and process color images in a relatively short time, with extra processing to extract the data from the Bayer matrix. It wouldn’t be the best sensor for doing astrometrics or narrow-band imaging with specialty filters, but it’s great for playing around and taking pretty pictures (or trying to!).

I had shot M31, the Great Galaxy in Andromeda, before, probably with my Canon 20D DSLR, but I wanted to take advantage of my wide field and gather an hour or so of data and see what I could get.

I enjoyed watching twilight fade and set up with a very good polar alignment. By now I’ve managed to learn the quirks of Software Bisque’s CCDSoft, and was able to calibrate the autoguiding with great success.

After returning home, I discovered that my first 15-minute exposure was not useable! The brighter stars in the image were fogged, probably by condensation on the CCD sensor glass. I have this mental image of bringing a telescope full of relatively moist L.A. basin air out to the desert, cooling the chip down to -5° C, and having every drop of moisture in that air condense on the chip.

After the first exposure, the combination of the imager fan and the dessicant plug mounted next to the chip managed to pull out all that moisture and leave me with a dry and clear chip. The dry desert air kept me clear for the rest of the evening.

Here is a luminance-only (monochrome) rendition of my M31 the Great Galaxy in Andromeda

The Great Galaxy in Andromeda, M31, with M32 and M110 nearby. 3x15 minute exposures, luminance only. (Click for full 2048x2048 resolution).)

Now after going to all the trouble of having a one-shot color camera, why am I presenting a monochrome rendition of M31?

I have a processing problem with the color version that I haven’t resolved yet. This galaxy has an enormous dynamic range, and this monochrome image is compressed down from a 16-bit master luminance image.

I’m only able to process the color information with 8-bit dynamic range. And my processing skill isn’t yet strong enough to preserve the color data when compressing it down to computer range. Here is the color version of this image. Note that the galaxy core is completely clipped to white in the color data, and I’m left with an ugly yellow ring around the core.

It’s an interesting problem, and I’m sure that I can find a way to do some “high dynamic range” (HDR) techniques to recover that color data near the core.

At that point, Jane called me over to see an interesting emission nebula she was observing visually in her 17.5-inch dob. The nebulosity was just detectable visually, and I really wanted an image to compare. Fun object, full of Milky Way stars, the nebula, and even some dark nebulosity in the upper right.

NGC7380 emission nebula and cluster, 3x15 minute exposures

Jane hunted down comet C/2010 G2 (Hill), a magnitude 10 interloper. It was a very difficult visual observation, but she nailed it, and I saw it as well.

10th magnitude comet C/2010 G2 (Hill)

Meanwhile Jane was also tracking down interesting galaxy groups, and had fun searching the fairly distant Pegasus 1 galaxy cluster in her 17.5-inch. I couldn’t resist imaging this as well.

My own misfires only left me with one usable 15-minute exposure of this fascinating galaxy group. Even with just one 15-minute exposure and lots of noise, it’s fun to see how many galaxies you can find in the full-resolution image. The two brightest members are magnitude 12.

Here we go from a relatively nearby solar system object, comet Hill, to a 200-million light-year distant galaxy cluster!

The Pegasus 1 galaxy cluster, one 15-minute exposure. Click for the full-resolution version, and see how many galaxies you can find in the somewhat noisy image.

Now I was just playing around. As it turns out, the Pelican Nebula was well placed, and The Sky 6 told me it would just fit in my field of view. This emission nebula is most famous for being “that thing next to the North America Nebula.”

The Pelican Nebula, one 15-minute exposure

One of my favorite visual targets is the enormous nearby open cluster M35 in Gemini in the winter Milky Way. Part of its appeal as a visual target is seeing the ten-times more distant open cluster NGC2158 which is about the same actual size as M35. The image didn’t disappoint.

Open cluster M35 in Gemini with distant sister cluster NGC2158. 2x15-minute exposures.

Finally, even though it’s almost cliché, I had to see what I could do with M42 the great Orion Nebula. It actually turned out to be a delightfully pleasing image. Sure the trapezium area is blown out to white, and maybe I can work out a way to recover that, but it sure is a fun picture. B^)

M42 the great Orion Nebula, 2x15-minute exposures

Jane and I were by ourselves for the dark sky weekend of November 14, 2009. We set up at our usual spot at Chuckwalla Bench. Unlike the past two months, this night featured a cold air mass that [...]]]>

Photo from Feb. 2009 of the Astro-Physics Traveler getting ready for a night of imaging at Chuckwalla Bench

Jane and I were by ourselves for the dark sky weekend of November 14, 2009. We set up at our usual spot at Chuckwalla Bench. Unlike the past two months, this night featured a cold air mass that required bundling up well. It also implied that the seeing from our desert location might not be perfect.

Jane brought her 12.5-inch Litebox dobsonian, and I opted for the 4-inch Traveler refractor (seen in my heading photo).

The night turned out to be beautiful. The seeing was good, and we were able to enjoy a few early Leonid and Taurid meteors as well. My goal was to try getting more exposure minutes on some classic targets, and try to get some piggyback constellation photos as well.

M33 and Triangulum region

Triangulum, Aries, and Andromeda, piggyback naked-eye resolution

The famous Pinwheel Galaxy, M33, was a difficult object for me when I started out in astronomy with a classic 8-inch Celestron SCT. The face-on spiral is enormous in the sky, covering almost as much area as the nearby Great Andromeda Galaxy. But its surface brightness is low, so with a little magnification it’s possible to look right through the galaxy without seeing it. I later learned that it sometimes shows up better in binoculars than a telescope.

If you click on the naked-eye resolution photo nearby, you can find M33 as a faint smudge just to the left of center. M31 the Andromeda Galaxy bright core is in the upper left.

The three bright stars of Triangulum are in the lower third, just left of center. The bright stars of Aries are also in the lower third, to the right of center. (Might be fun to use Flickr’s photo tagging feature to highlight the features.

M33 the Pinwheel Galaxy

Again “click to embiggen” as Phil Plait would say. This image is a stack of four 15-minute exposures with the AP Traveler and the SBIG ST-4000XCM one-shot color CCD camera. I love seeing the famous red star-birth regions sprinkled through the arms of this nearby galaxy.

In terms of technique, I used a Bahtinov focusing mask for the first time. It saved a lot of time in finding and maintaining focus. Autoguiding worked perfectly. It felt really good to have confidence to take long sub-exposures and stack them in Photoshop. This was my first true one-hour image, and the first I’m proud to have seen at full resolution.

Auriga and IC 405

Piggyback view of Auriga, naked-eye resolution

Auriga was one of the first constellations I identified and recognized on my own as a new astronomer, so I’m always delighted to see it again.

In the piggyback shot, the bright Auriga stars form a squashed pentagon slightly left of center. The right-most star doubles as part of Taurus. North is to the left, and the brightest star there is Capella. In the full-resolution image you can see the Milky Way open clusters M36, M37, M38, and I think that’s M35 in Gemini in the lower right.

Jane was enjoying touring through targets in this part of the sky, and spent some time attempting to see visually the difficult target IC 405, the Flaming Star Nebula. (Her companion post on the subject is coming soon.) I was intrigued as well, and took 30-minutes of exposure time on IC 405. It’s not visible in the piggyback view, but is found in Auriga near the upper center of the picture.

IC 405 the Flaming Star Nebula

I wasn’t familiar with this target, and the 30-minutes of data here shows only the brightest areas of this faint nebula. Longer exposures and a Hydrogen-alpha filter will show the nebulosity extending out to the left and curling up like a huge comma. This was a really fun target, and I’m looking forward to Jane’s discussion of it.

Orion, the Flame and the Horseshoe

Orion, piggyback naked-eye resolution

Finally I wanted to see if my little 4-inch refractor could possibly do justice to one of the most popular astrophotography targets. Here in my naked-eye resolution piggyback photo is the Orion constellation, with its famous bright star-birth nebula near the dead center of the photo.

The target I had in mind wasn’t the Orion nebula itself, but two very different nebulae near the left-most belt star Alnitak (Zeta Orionis). Just to the left of Alnitak is a bright yellowish nebula called the Flame. In a telescope it shows a lot of detail, looking almost like tire tracks. The full-resolution picture of the constellation has just a hint of the flame. If you already know it’s there, you might be able to see it.

For my piggyback photos I used my Canon 20D digital SLR camera, mounted on top of the AP Traveler. I shot 5-minute exposures, and tried to subtract a 5-minute dark frame, which doesn’t seem to make much difference.  The camera does leave behind a reddish glow which I’ve removed in Photoshop.

Just below Alnitak is the Horsehead nebula, also known as Barnard 33. Seeing the Horsehead visually is a fun and difficult project, requiring really good transparency and a fairly large telescope. Jane observed it visually in her 12.5-inch.

The Flame and the Horsehead in Orion

I never dreamed the image would turn out this nicely. The big white bright blob just above center is Alnitak. In the lower right is Sigma Orionis, one of my favorite multiple star systems. Of course the bright Flame is just left of Alnitak, and dark nebula B33 is just below center.

Just as with M33, this image is made up of four 15-minute exposures. The telescope is a 105mm f/6 Astro-Physics Traveler, with an SBIG ST-4000XCM one-shot color CCD camera. The mount is the AP Mach-1 GTO on wooden tripod, and I did autoguiding and image capture with Software Bisque’s CCDSoft. I used SBIG’s CCDOps software to process the Bayer-matrix one-shot color pixels out to luminence and RGB components, combined the L and RGB components in Photoshop, then stacked the four color images for the final photo.