Serious Star Gazing

Another attraction of Fort Davis is its close proximity to the McDonald Observatory.  This is a full-on research facility with multiple telescopes, large and small with a great public program.  We decided to take in both their day and night programs.

The day program is a solar viewing and tour of a couple of the more impressive telescopes.  Cyndee and I headed out for the 15 mile drive from Fort Davis to the mountain top where the observatory is.  Its a really nice drive and would be worth doing even if there were no telescopes at the end.  The visitors center was a nice facility although many of the interactive displays were in need of attention or outright overhauling.

McDonald Observatory visitor center atop Mt. Locke.

A barn swallow thought the visitor center was a good nesting place.  She is literally raising her clutch at the front door to visitor center.

Pronghorns on the foothills to Mt. Locke.

 The solar viewing occurs in a small auditorium at the visitor center but then it is a ride in a van to the peak where we start the tour outside the dome to the 107" telescope.  In the panorama below the dome to a 12" telescope can be seen as we look out across the Davis Mountains.  I never did understand why they put a telescope on the side of a mountain, below the foundation of another telescope.  Its view of the sky is really limited.

View of Davis Mountains from Locke Peak and the parking lot of the Harlan J. Smith Telescope.

Inside the structure for the 107" telescope we climb up three landings of stairs and enter the dome where the telescope resides.  It is cold in the dome, they keep the climate control system operating at the predicted temperature and humidity that is expected at the time they will open the dome for the night.  Tonight, when the sun is well below the horizon, it is expected to be 55 deg.  So that is what it is in the dome right now.  When the door opens there will be no fogging of the mirror or warping of the giant metal housing holding the mirror due to thermal shock.

Glad I wore long sleeves and a vest.  Chillers were keeping the inside of the dome at 55 deg in anticipation of that being the temperature when they open the dome on this night.

Our tour guide, Rachel, did a great job keeping the tour interesting and moving along.

The star of this part of the show is the Harlan J. Smith Telescope, a single-piece mirror 107" in diameter and over 12.5" thick, made of fused silica.  The above photos have only provided a glimpse at the giant looking glass.  Below is a little more comprehensive view.

Harlan J. Smith 107" diameter telescope.

The Harlan J. Smith is built old-school, using a single mirror and enclosed tube.  It makes for a fine instrument but it also makes it incredibly heavy and expensive.  That big hunk of iron hanging off to the side of the telescope is a counterweight.  Total tons for this bad boy - 160.  The dome housing the telescope is another 435 tons.

Just for fun, our tour guide changed the position of the telescope and rotated the dome, but never opened it (couldn't until the temp outside equaled the temp inside).  The impressive part of this, outside standing under nearly 600 tons of moving mass, was that the 160 ton telescope was being moved by a motor rated at less than one horsepower.  I guess they got that counterweight balanced just right.

Our next stop on the tour is about a three quarter mile ride to Fowlkes peak and the Hobby-Eberly Telescope.  One of the largest telescopes in the world.  This one is a 433 inch diameter.  That's a whopper in the telescope world.  And this one was built new-school.  The mirror is segmented, 91 hexagonal shapes and no enclosed tube.  It was built for a fraction of the cost of an old-style, single mirror, enclosed tube telescope one fourth the size.

Hobby-Eberly Telescope.
The big nub sticking up is a laser alignment device that keeps all 91 hexagonal mirrors properly focused.

The day we were at the H-E-T it was in the middle of an upgrade.  Many of the mirror segments were out for refinishing and the collector at the top of the scope was being completely replaced.  Hence the big blue tarp hanging above the mirrors to catch a dropped tool.

As cool as the daytime tour was we were anticipating our night program.  This time of year it only happens a couple nights a week.  We watched the weather forecast for a few days and chose the Tuesday night program.  That night was predicted to be the clearest of all the nights we were going to be around.  However, it was also predicted to be windy and cold.  We would have to layer up.  Another detractor, at least for a star party, is that we are going to be under a full moon that will rise just as the program starts.

 

Looking west from the visitor center entrance.  When the sun goes down the red exterior lights come up.

Looking east, up the pathway to the amphitheater.  The glow of a full moon about to rise is beginning to show.

Hard to tell but this is the amphitheater.  Red lights are at the end of each row of benches.

I cranked up the light sensitivity of my camera's chip to the max and tried to grab some shots.  It is impossible to tell from the above amphitheater shot but there are about 150 people sitting there.  It is cold and the wind is blowing and a lot of the guests didn't head the advisories to dress warmly.  Even with all the layers we put on it is not enough to keep the wind from cutting through.  I predict some early departures.

As our guide was giving us a tour of the sky, using the most awesome laser pointer I have ever seen, you could hear shuffles and see shadows of people beating a retreat to their cars.  If there had been enough light I am sure we would have seen lots of blue skin.  We started getting snotcicles but we stuck it out so we could get access to the more than half-dozen telescopes.  Each pointed at a different object in the sky.

Even thought the moon has yet summited the horizon, its light is already cloaking all but the brightest stars.
Just barely visible is the constellation Orion.

Normally the moon is welcomed and romantic and all that stuff.  But not tonight, tonight it is the spoiler.
So bright it was, I took this shot hand-held.

It was great.  We made our way around to each telescope and looked to see what it had to offer.  For me the highlight of the evening was looking at Jupiter and four of its moons.  It was so cool, there was about a third of the planet in view and then four bright white dots in a perfect line against a backdrop of ink black space.

By the time we sat through the sky tour and made a stop at all the telescopes we were as frozen as the popsicles that left early.  We had hot chocolate we were going to get into when we got back to the rig.