Globe at Night, Part 2

My son and I collected some more sky brightness measurements on the night of February 9, 2016 in the vicinity of the small town of Bedias, Texas. Bedias is located in a rural area, surrounded by flat pastureland. There are many areas with views down to the horizon, or nearly so. Regretfully, there are several light domes that spoil what would otherwise be a spectacular view. Still, the skies there are fairly dark, at least at zenith.

The following two images were taken with the same equipment and settings as those in the previous post.

For reference, here is an image of the Orion constellation taken from my house the same night as the Bedias trip:

Orion at the ObservaRory

This image was taken on a county road near the western edge of Walker County, just a few miles east of Bedias.

A few miles east of Bedias, Texas. The red line to the left was from a passing aircraft.

The light dome of Houston, Texas and surrounding cities dominated the sky to the southeast. The light dome of Huntsville was visible to the east, and Madisonville's light dome was barely visible to the north.

While not as dark overall as the sky near Weldon, the view was very nice, with many faint stars visible to the naked eye at zenith, and the Milky Way clearly visible.

Globe at Night

On the night of February 3, 2016, my son and I went on a little expedition to collect sky brightness measurements for the Globe at Night campaign. Globe at Night is a citizen-science project for raising public awareness of the effects of light pollution. Several times a year they host campaigns where participants observe a selected constellation and report how it appears in relation to a series of magnitude charts.

Our trip took us a few miles north of our house where, according to DarkSiteFinder.com, the sky brightness is rated around 3 on the Bortle scale.

The two images illustrate the difference in sky brightness between the ObservaRory (my house) and a location a little north of the town of Weldon, Texas. Both are 30-second exposures taken with a Canon EOS Rebel T3 with a 18-55mm zoom lens at 18mm (f/3.5) at ISO-1600. Both images are unprocessed, except to reduce their sizes.

Orion at the ObservaRory, about a mile north of the city limit of Huntsville, Texas.
The sky here is around 4.5 on the Bortle scale.

Orion north of Weldon, TX. The sky in this region measures 3 on the Bortle scale. Some of the light dome of Huntsville and a nearby prison unit are visible to the lower-left. Fainter objects, such as the Rosette Nebula, that are washed out by the skyglow in the previous photo are visible here.

To me, the most striking thing about the second image is the darkness of the background sky--there is no nauseating soup of mercury and sodium lights washing out the stars.

To learn more about light pollution and its effects on the environment, health, and energy consumption, I suggest the following links:

• Globe at Night - What is Light Pollution
• Dark Skies Awareness: Light pollution, what is it and why is it important to know?
• Light pollution at Wikipedia

Moon

Just a quick post to let everyone know that I'm still here. It's been a few months since I've done anything with my own scopes. Tonight, the kids and I went outside to look at the Moon, and I took a few shots. Nothing spectacular. But I am very pleased with this Baader Contrast Booster filter. It does a really good job mitigating the chromatic aberration produced by the ST80.

The Moon, December 17, 2015; ST80 w/CB on Vixen SP
42 images, ISO-100, 1/200 second exposures

X Bar Ranch Nature Retreat

My older son and I spent a couple of nights at the X Bar Ranch Nature Retreat near Eldorado, Texas. The ranch features hiking and bike trails, and they have observing fields for amateur astronomers. They also host the annual Eldorado Star Party.

The sky at the X Bar Ranch is rated Class 2 on the Bortle Scale, which is almost as dark as possible. The night sky is amazing!

Below is a panorama of the one of the observing fields, taken from the deck of the Live Oak Lodge. The area is kept mowed, and electrical outlets are located on the back of the lodge and surrounding cabins:

We stayed two nights, but it was only clear on the first night. Seeing was steady above about 20 degrees, with some haze below that. I set up in a small field outside of our cabin and took some pictures of the Milky Way, and the Lagoon and Trifid nebulae. Here is a single 2-minute exposure of the Milky Way taken at ISO-3200 with the Canon EOS Rebel T3 (1100D) mounted on the Vixen Super Polaris:

The very dim illumination of the field at the bottom of the image is from some small, solar-charged walkway lights located behind the camera. The regular observing field is darker.

This is a crop of a stack of 27 2-minute exposures at ISO-3200:

Compare that image to images that I took at the same time two years ago from the SHSU Observatory. While I am pleased with how the older images turned out, they required a great deal more processing to tease the stars out from the light pollution. Most of the time that I spend processing images is usually concerned with removing haze and gradients caused by city lights. More on light pollution later...

One of my goals that night was to make a mosaic of four to six images in the area around the Lagoon and Trifid nebulae. Time was running short, though, and the Trifid was in the haze by the time I got to it. I had to settle for three sets of images. Still, I think it turned out well over all. Here is a mosaic stitched together using Microsoft Image Composite Editor (free software alert!):

Each of the three images is a stack of 12 2-minute exposures at ISO-3200. All were taken with the Canon EOS Rebel T3 (1100D) on the Orion ShortTube 80 with a Baader Contrast Booster filter. The scope was mounted on the Vixen Super Polaris.

I'm really impressed with how well the Baader Contrast Booster works at minimizing chromatic aberration. After using this filter a few times I've concluded that my ShortTube 80 crown/flint achromat is now working about as close to the performance of an ED achromat as it ever will. If only I could find a 1.25" field flattener...

Here are close-ups of the Lagoon and Trifid from the images that compose the mosaic:

Messier 8, The Lagoon Nebula

Messier 20, The Trifid Nebula

The sky here at the ObservaRory is about a 4.5 on the Bortle Scale. The Milky Way is fairly bright overhead, but is lost in the light dome of Huntsville, Texas near the horizon. The difference between the ranch's Class 2 sky and my Class 4.5 sky was immediately apparent, both to the naked eye and through the scopes. Even the polar alignment scope on the mount had a better view at the X Bar Ranch!

To illustrate the difference, compare these two subs taken exactly one month apart. Each image is a 2-minute exposure taken at ISO-3200 with the same equipment under similar weather conditions. No processing has been performed on either image, except to reduce them for display here. (The yellow cast was caused by the Baader Contrast Booster.)

Bortle Class 4.5 Sky at the ObservaRory

Bortle Class 2 Sky at the X Bar Ranch

Besides the darker background, many more stars are visible along with fainter portions of the nebula.

I am definitely spoiled by the sky in West Texas. I plan to make more trips as often as I can.

I hope to visit the X Bar Ranch again, too. The accommodations are comfortable, and the scenery is beautiful. The Meador Family, who own the ranch, are terrific hosts. They've thought of nearly everything and seem very friendly. If you happen to head that way, also check out the Caverns of Sonora:

Lower Room, Caverns of Sonora

Pluto

On the evening of July 14, 2015 I took a picture of Pluto to celebrate the flyby of Pluto by NASA's New Horizons spacecraft. But, there was a problem: I couldn't find it!

Pluto is very small, and also very dim. It is typically around 14th magnitude, which is about 128 times dimmer than the human eye can see in Earth's darkest skies. It's not even visible in most amateur scopes, outside of using long-exposure photography. In addition, the part of the sky that Pluto is currently located in is along part of the Milky Way. How was I to locate such a small, dim object among all of those stars?

Plan A was to use my various planetarium programs to find reference stars that would aid in locating Pluto. That failed because none of them had enough stars in their databases to account for everything I was seeing. I made an educated guess (which I discovered was correct), but there was no way to tell for sure until I could implement Plan B.

Plan B was to use a technique similar to that used by Pluto's discoverer, Clyde W. Tombaugh. Tombaugh worked for the Lowell Observatory in the 1920s and 1930s. He would select a part of the sky and take a picture of it with the observatory's 13-inch astrograph (a telescope designed for photography). A few nights later he'd take another picture of the same area. He then used a blink comparator to look for differences between the photographs. Objects that stayed in the same position were stars, but anything that moved was a comet, asteroid, or a planet.

I took my second set of images on the night of July 24, 2015. After processing and lining up the images I was able to see that my suspect Pluto was, in fact, the real thing! The animated GIF below shows Pluto's position on the two nights:

Pluto! Click on the image for a larger view.

To further illustrate how inconspicuous Pluto is, I put together this movie from the July 14th image:

So, there you have it. A mundane little dot moving among a sea of other dots. Who knew what a beautiful little world Pluto would turn out to be?

Public domain image courtesy of NASA and Wikimedia Commons.

Waxing Moon, July 24, 2015

The Moon, July 24, 2015; ST80 w/CB on Vixen SP
38 images, ISO-100, 1/160 second exposures

Click here for the full-size image.

This is my first attempt at imaging the Moon using the new Baader Contrast Booster filter. When I image the Moon with the ST80, I generally use the stop-down adapter that's built into the dust cap. This reduces chromatic aberration, yielding a sharper image with a less-pronounced red/blue halo surrounding the Moon. The disadvantage to using the adapter is that it greatly reduces the telescope's aperture, which reduces the amount of detail in the image.

This image was made without using the stop-down adapter. It was stacked in RegiStax 5.1 and processed in Photoshop CS6. There were some color anomalies, but I hid them by slightly desaturating the image and adjusting the curves a bit. The ST80 certainly doesn't capture the Moon's color characteristics as well as the Epsilon 200, but overall I'm pleased with what the filter can do.

Next, I may try using a Barlow to get a closer view.

Baader Contrast Booster

This post is fairly long, so here are the pictures. I'll meet you on the other side!

Messier 8, the Lagoon Nebula; ST80 w/Baader CB on Vixen SP; Canon EOS Rebel T3; 11x120 @ ISO-3200

Messier 7, Ptolemy's Cluster; ST80 w/Baader CB on Vixen SP; Canon EOS Rebel T3; 32x60 @ ISO-3200

Back in February I purchased two new toys for my ST80/Vixen Super Polaris rig: a Baader Contrast Booster with IR-Cut filter, and an ADM dovetail saddle adapter. Family, clouds, weather, clouds, personal health, clouds, work, clouds and clouds prevented me from doing any astrophotography until mid-July.

The Vixen Super Polaris was the last mount of the Polaris line that was produced without a dovetail saddle. Personal budget limitations have prevented me from upgrading to a modern mount, but ADM Accessories makes an adapter within my price range. The VSAD-SP bolts to the top of the mount head. Two large, spring-loaded screws on the saddle grip the male dovetail bar very securely. Installing and removing the scope is very easy now. In addition, the telescope and camera can be properly balanced on the declination axis, which was impossible before because of the size of the scope and arrangement of the rings.

I'm always trying to find ways to get better images out of sub-par equipment. The ShortTube 80 is a great little scope for casual viewing, but the chromatic aberration inherent to fast achromats makes it unsuitable for imaging. A quality imaging scope is still outside of my price range for the foreseeable future, so I am trying to make the best with what I've got.

My research and experimentation led me to try the Baader Contrast Booster. The Contrast Booster filters out wavelengths on the extreme ends of the visible spectrum that are responsible for much of the blurring and halos caused by chromatic aberration. It also filters out wavelengths produced by common sources of light pollution.

I had the opportunity to try the filter visually against the Great Orion Nebula back in March. The moon was at 68% illumination and the nebula was about 30 degrees above the light-polluted horizon. Despite all of that, I could see a remarkable difference in contrast.

The two images above were made using the Baader Contrast Booster. The chromatic aberration, while not competely removed, was significantly reduced. This was a major improvement over my best results with the Orion SkyGlow Astrophotography Filter and the #15 yellow filter discussed in the Fixing Halos post.

The three following images illustrate the differences among the filters:

Baader Contrast Booster

Orion SkyGlow Astrophotography Filter

Yellow #15

The stars in the Contrast Booster image are larger, but that may be due to the fact that it was shot at ISO-3200 versus ISO-800 for the other two. The important thing to note is that the halos are confined to a tight ring around the stars.

The image of the Lagoon Nebula at the top of the post was processed without attempting to remove the effects of chromatic aberration. I applied the Color Layer technique to the image of Messier 7 to reduce an overall purple hue that was likely the result of all of those bright stars.

I was concerned that the Contrast Booster might cut out too much blue from the images. Pure blue hues are not common in astroimages. The best example that I can think of is Messier 20, the Trifid Nebula. This nebula presents a striking contrast between a red emission region and blue reflection region. The image of M20 below was compiled from only five subs, so it is fairly grainy. However, the blue came through the filter nicely:

Messier 20, the Trifid Nebula; ST80 w/Baader CB on Vixen SP; Canon EOS Rebel T3; 5x120 @ ISO-3200

I plan on doing more tests and reimaging more objects with the Baader Contrast Booster. So far, however, I think this filter brings the ST80 close to the performance of an ED refractor--at least as close as it can reasonably get.