Saturday, December 26, 2015

McDonald Observatory, Davis Mountains, Texas

I passed this historic ranch on the way to the Observatory. They have horseback riding there and I tried to book a ride, but I had no phone service in the campground and they did not answer when I called from town. So next time, perhaps.
Historical marker about the ranch.
Heading into the Davis Mountains on the scenic loop road that I didn't have time to complete.
Approaching the observatory. Two of the larger telescopes can be seen on the mountaintop.

The Visitor Center: I arrived just in time for the live Solar Viewing and tour.
Our tour began with a 45 minute college level lecture before the live solar viewing. In this filtered live view of the sun you can see two sun spots, the dark one on the right and one forming on the far left where the red laser is pointing. The white spot in the center is a solar flare, and the dark line above it is another feature that I can't remember the name of. Good thing there was no test.
Close up of the Sun Spot. In the live view you could see the shimmering movement of the gases around it.
By covering the rest of the sun with the red they can highlight the solar flares at the edge.
After the solar viewing we were off to tour the two main telescopes. The first we will see is the 107" (mirror) Harlan J. Smith Telescope. Notice the temperature inside the dome is 46 degrees. They keep the temperature the same as the expected nighttime outside temperature so when they open the dome for night viewing there will be no fogging of the view due to temperature differences.
Our second stop will be at the newer 362" (mirror array) Hobby-Eberly Telescope, currently the 3rd largest in the world. (Canary Islands and Hawaii have #1 and 2)
Outside the Visitor Center is this large sundial whose shadow shows the current time. We board a shuttle from here to take us the rest of the way up the mountain.
View of the Hobby-Eberly Telescope.
The dome on the left holds the first telescope built at the McDonald Observatory by the University of Texas in cooperation with the University of Pennsylvania if I remember correctly. Texas had the money collected in donations, and Pennsylvania had the Astronomy Program. The dome on the right is where we will go first...Harlan J. Smith Telescope.
View from the top. It is the highest point in Texas accessible by road.
This is the residence of the lead astronomer....not bad.
And other resident and guest astronomers reside here.
View of the Hobby-Eberly Telescope atop a nearby mountain.
Some facts about the telescope:
We had a choice of elevator or stairs. My Fitbit wanted to do some stairs.
The huge Harlan J. Smith Telescope attached to an arm with counterweight on the right. The stairs allow access to the telescope from above.
The round hatch on the side is one of the places where additional mirrors can be attached depending on the study being done.
Our guide at the control panel.
Notice how he is raising the platform he is standing on. This helps workers access the telescope from below.
The guide uses a small model of the telescope to show the location of the large mirror.
Next he operates the control to raise the telescope. Click on the short video.
The white covering over the opening to the sky can be moved to access other equipment as well.
This video shows how that works.
A crane is exposed that is used to move supplemental mirrors into place on the telescope.
 Finally the whole outside dome is rotated to move the opening to the right angle depending on what part of the sky is to be observed. 
Watch the video of the dome rotating. The dome is mounted on castors that are not attached to the floor where the telescope is, so there are no vibrations affecting the telescope.
When in position then the outside doors are opened for the telescope to view the night sky. We can't watch that because they never open them in the day due to the difference in ambient temperatures.
You can see the doors to the opening from the outside. 
Our next stop is at the newer Hobby-Eberly Telescope, named for its chief benefactors.
This telescope is much lighter and cheaper to build due to its design. Instead of one big mirror it has an array of mirrors. 

As with both of these large telescopes, one does not view the sky through an eyepiece mounted on the telescope itself. Instead telescopic views are transmitted to computers in the control room.
This telescope is out of commission while it is being prepared for an upcoming study. Unfortunately it is pointed away from our view, so it is hard to get a view of the segmented mirrors. Here you can see the edge of one mounted on the blue frame below. 
This telescope is not mounted on a large arm like the other. Instead it is on a platform whose "feet" are inflated in such a way that the platform hovers and moves on a cushion of air. 
View from the shuttle of the Visitor Center and some smaller telescopes below as we descend the mountain.
 And view from the road as I return to the campground.
If you ever have the chance to visit an Observatory, it is a very interesting tour. They also have night sky viewing tours.

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