Author: Andrew

An electrical engineer, amateur astronomer, and diver, living and working on the island of Hawaiʻi.

Mercury at Maximum Elongation

Today Mercury reaches maximum elongation, the furthest point it will reach from the Sun in our sky and the highest it will be above the sunset for this evening apparition. The planet is easily visible as a bright, starlike object about 23° above the setting Sun as twilight begins. Over the next couple weeks Mercury will slide back into the sunset, heading for inferior conjunction on June 19th.

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Comet 209P LINEAR Meteor Shower Reminder

A reminder that there is the possibility of a strong meteor shower this evening. The Earth may pass through a cloud of debris left by comet 209P/LINEAR. Sky watchers should observe around 21:00 to 22:00HST on the evening of May 23rd.

Leonids in Orion
A pair of Leonid meteors streak through Orion
North America and the North Pacific is favored for visibility. If it occurs the peak will be short and sweet, lasting about an hour. Fortunately for us in the islands this is predicted for mid-evening hours, from 7-8UT on the 24th (21-22HST on the 23rd). Predictions for the shower range from minor to spectacular. The meteors will seem to radiate from a part of the sky occupied by the dim constellation Camelopardalis, thus some are dubbing this shower the Camelopardalids.

For Hawai’i the radiant will be low in the north, about 20 degrees above the horizon, near Polaris. This means that any meteors we see will be hitting the atmosphere at a low angle. Combined with the low speed of the meteors this could lead to very showy bolides streaking across much of the sky.

As with any meteor shower, any predictions are to be taken with a large dose of skepticism. It is important to point out that meteor prediction is not an exact science, rather a bit of an art form. In this case there are any number of unknowns involved, we could see nothing, we could see a true meteor storm. This event could be anything from “meh” to “oh wow!!!”. To their credit, the folks making these predictions have been impressively right on several recent showers.

I would strongly suggest that you at least take an effort to step outside after 9pm on Friday evening and see what the sky has to offer. All you need is a clear dark sky.

Four Lasers Aim for the Galactic Center

I am truly jealous! My friend Dan Birchall got the photo I had hoped to get… All four Mauna Kea lasers in operation at the same moment. Better yet, all four lasers were on the same target, the center of our Milky Way galaxy. The result is a great photo of four yellew beams converging to the same spot in the sky.

Four Lasers on the Galactic Center
Four lasers from Keck, Gemini and Subaru probing the center of the Milky Way Galaxy, photo by Dan Birchall
I had attempted to get a four laser shot last year. The one night all four were scheduled I was ready, on the summit with the needed gear for a photographic session. Three of the four lasers were operating, but Gemini had suffered problems and never propagated their laser. I have managed a few very nice three laser images, including one from last summer with three of the four aimed at the galactic center.

The four beams come from our two Keck telescopes, plus one from Gemini and one from Subaru. the lasers are used to create reference beacons for the adaptive optics systems used on these large telescopes. I will, with a little possessive pride, point out that the Keck lasers are much more powerful than the others.

The scheduling of all four lasers at once is a rare occurrence. All four lasers on the same target? Even more luck was involved! It helps that Dan is a telescope operator and spends far more dark time on the summit than most of us. He took advantage of the situation correctly… Grabbing the camera and shooting.

Below is more footage from Dan, a little time lapse of the telescopes working…

Planet Found with an 80,000-Year Orbit

W. M. Keck Observatory Press Release…

A team of researchers has discovered and photographed a gas giant only 155 light years from our solar system, adding to the short list of exoplanets discovered through direct imaging. It is located around GU Psc, a star with one-third the mass of the Sun and located in the constellation Pisces. See the article in The Astrophysical Journal.

GU Psc b
Artist’s view of the planet GU Psc b and its star GU Psc. Credit: Lucas Granito
The international research team, led by Marie-Ève Naud, a PhD student in the Department of Physics at the Université de Montréal, was able to find this planet by combining observations from the the Gemini Observatory, the Observatoire Mont-Mégantic (OMM), the Canada-France-Hawaii Telescope (CFHT) and the W. M. Keck Observatory.

A distant planet that can be studied in detail

The object was discovered using Gemini-South and followed-up with Gemini-North spectroscopy and CFHT photometry. Once Naud’s team had the entire spectrum, they realized the object had a very low temperature, with properties similar to substellar objects like brown dwarfs or planets.

One possibility was that the object had a peculiar spectrum simply from its youth, and that this had nothing to do with it being a binary, but the other tantalizing possibility was it was a binary planet, with one component being slightly warmer than the team derived from their analysis and the other component slightly cooler.

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A Programmable Logic Controller

My father-in-law made a career of repairing the heavy machinery of the local plywood and paper mills in the lumber and farming community of LaGrande, Oregon. Large machines such as high speed saws, conveyors, process tanks and more. One evening he was working with something I did not recognize and I made the mistake of asking what it was.

Ladder Logic
A snippet of the Keck 1 local controls ladder logic
Over the kitchen table were spread the printouts of an arcane programming language, what I learned was called ladder logic. This sort of programming is a throwback to a day when control systems were built from dozens, or even hundreds, of electromechanical relays wired together to perform complex tasks. The relays are gone, replaced by a microcontroller, the programming language remains. It really does look like a ladder, drawn the same as the wiring diagrams used for those banks of relays. Each function, or rung, is filled with symbols for relay contacts and coils.

As a computer engineering student I was appalled that anyone would program this way, I could not conceive of using such a backwards seeming technology. Why not just use a simple programming language like C to build the functions? Ladder logic was the worst sort of programming language, no abstraction, no compartmentalization, prone to building hard to understand spaghetti code.

Keck 2 Dome PLC
An Allen-Bradley PLC-2 that controls the Keck 2 dome and shutters
The ladder logic program is downloaded to a device called a PLC, or programmable logic controller. Usually a rack of cards with a controller at one end and a set of input/output modules filling the remainder of the rack. The PLC takes the code and executes it, scanning the inputs and following the rules set in the logic to switch the outputs. connected the the various push-buttons, limit switches, motors and lights, the PLC can control a huge range of industrial equipment. These devices are the workhorses of entire factories, and often observatories.

Jumping ahead more than a decade… I now find myself using this same technology and programming in ladder logic. Many of the critical systems at Keck use PLC’s for control. The dome controllers, local controls and various safety systems use PLC’s to accomplish the task. Some of these systems are over two decades old, and for the most part spares can still be purchased.

The technology is not dead, far from it. The new telescope control systems currently being designed will feature modern ControlLogix PLC’s to implement the critical safety functions. There are dozens of interlocks throughout the telescope, switches that detect the condition of the system and prevent bad things from happening. If a lock pin is not installed, if a drawbridge is down or a crane not stowed properly, the telescope does not move.

Never mind me, I am just reading a twenty year old user manual, learning how to set the serial communications on a PLC-5.