Saturday, August 22, 2015

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