Globe At Night Returns

The 6th annual Globe At Night campaign to measure sky brightness around the world is about to begin.
From February 21st to March 6th you'll have the opportunity to measure sky brightness by counting the number of stars visible in the constellation of Orion. It is easy, fun & very worthwhile. So click on over and become a citizen scientist by measuring sky brightness where you live.

Winter Weather to Return this Week

It is time again to roll out the old photo of the dome and the weather gear to let people know that some rough weather is expected to head our way that will likely close the observatory to visitors in the coming days.

Rain, fog, wind, & snow are all in the forecast between tonight and Sunday night. In the coming days please pay close attention to weather forecasts (such as this Special Weather Statement issued by the National Weather Service) and any road or other closures before heading up to visit the observatory or the Palomar Mountain area.

Palomar History Photo of the Week - Building a Dome

Here is another photo taken in the 1940s by Lee A. Farnsworth, Jr. It shows the dome of Palomar's 48-inch Schmidt telescope (now called the Samuel Oschin Telescope) while it was under construction.

Good Times in Seattle

Thanks go out to the Seattle Astronomical Society (SAS) for having me up to speak last weekend at their annual banquet.

I think it was the only talk that I have ever given that had boats parked just outside the venue. Possibly they were there for me to make a quick escape if needed.


Fortunately the boats were not needed. The SAS took good care of me and everyone seemed to have a good time. They even had this sweet (in more ways than one) Palomar cake:

You can read a review of my talk here on Greg Scheiderer's nice Seattle Astronomy blog. Thanks for the nice words, Greg!

Open Again

Palomar Observatory is open again to the public with our regular 9:00 a.m. - 3:00 p.m. visiting hours.

Observatory Closed January 31st

I just found out that Palomar Observatory is closed to the public today.

Palomar History Photo of the Week - Sitting Down on the Job

A couple of weeks ago I posted photos of the mirror cell for the 200-inch telescope as it arrived in California via ship. This week's photo was taken January 27, 1936 - two weeks after its arrival.


It shows the mirror cell sitting on the mirror's grinding machine with a member of the optical shop posed sitting with his legs in the center hole. Note that there are three other people in the photo working on the rail to the upper right of the mirror cell. Unlike the man posed on the cell, they were working look blurry - a result of the slow films in use back then.

Robo-AO in Action

I am hearing that the Robo-AO team has had a good week of testing here on the Palomar 60-inch telescope.

Their ultraviolet (UV) laser is mounted on the south side of the telescope. One of the chief issues for the week was the installation and testing of their periscope which transfers the laser beam from being just offset from where the telescope is pointing to being on axis with the telescope.

If you look at the photo below you can see the location of the laser, which is located in the black box just under the telescope on the right side. From this position the laser will propagate to the upper left where their periscope assembly is located. You can see that as the black end of the telescope with something hanging off of it.


The second photo shows the whole set up from a different perspective. Note that the cover to the laser has been removed. Click on the image to get a better look at its innards.

Photo by Christoph Baranec

The third photo shows the periscope assembly from a different vantage point. Christoph Baranec (Robo-AO's principal investigator) can be seen adjusting a mirror. In this image the UV laser is on. UV light is invisible, but still potentially damaging so you'll notice that Christoph is wearing a face shield to protect his eyes (I was wearing one too when I took this photo). Also notice that the mirror on the center axis of the telescope is fluorescing due to the UV light shining on it.

Saving the best for last, this final photo shows the top of the telescope. It was taken with a camera that records UV and visible light, so it reveals both the telescope and the normally invisible UV laser beam.

Photo by Christoph Baranec

The team has also been evaluating any flexure in the telescope and laser pointing to better ensure better results in the future.

Stay tuned for more on the Robo-AO program. Their next observing run will be in March.

Robo-AO Returns to Palomar

This week the Robo-AO team is back on Palomar for some tests of their laser-guide star adaptive optics system for our 60-inch telescope.

I will post some updates and shots of the laser in action over the next week or so, but here is a shot looking at the back end of the telescope showing some of the equipment that is in use for the project:

Palomar History Photo of the Week - Building the Horseshoe

On January 17, 1939, seventy two years ago today, the last of the three big pieces of the 200-inch telescope's north horseshoe bearing was lifted into place. The bearing is a key component the 530-ton telescope, allowing it to pivot to look east or west. The horseshoe bearing floats on a thin film of pressurized oil and helps to support the weight of the telescope.

These photos were taken from the dome's inside catwalk by Lee A. Farnsworth, Jr. who worked at the observatory during construction of The Big Eye.

The first picture captured the view from just southwest of the telescope looking northeast toward the horseshoe. The east horn of the horseshoe is easily visible on the right.


The second photo shows the west horn of the horseshoe as it is being lifted by the crane at the top of the dome. The


The final shot shows the west horn of the horseshoe being lifted into position. Note the person in the photo. The fully assembled bearing is 46 feet across would still need to have its pieces welded together to become functional.

The successful welding of the horseshoe marked the completion of the telescope's mounting structure. In the months that followed the Palomar crew would move on to assemble the 200-inch telescope.