November 2018 DFAC Update

quidnoviNewsletter of the Desert Foothills Astronomy Club
Captain’s Log: November 1, 2018

Greetings Fellow Stargazers,

Other than shows at the Star Barn (see our DFAC Events page) there will be no further formal club activities until after the holidays. Too many members are busy or traveling. I’d like to host a Holiday Social and play some Asteroid Billiards, but I’m booked with 4 contractors trying to complete some work yet this year. And so it goes. Enjoy your Thanksgiving, and we’ll see you in December!

1. Speckle interferometry
That said, Richard Harshaw has extended an open invitation to all members for a 3-hour lesson in his current area of research. If the forecast says the sky is clear, then you can usually expect Richard will be running measurements that night. Give him a call or email (info available via DFAC Events) and let him know you’re interested. This works best if 1 or 2 people attend. There’s space inside the observatory for 3 people, and that’s the best way to watch the science happen.

2. Speckle interferometry — the experience
Last week Ron Walker and I were the attendees at a speckle interferometry demo at Brilliant Sky Observatory. We started shortly after sunset, comfortably ensconced inside the “dome” on padded chairs, with a full and close-up view of the instrumentation and computer display.

Richard started with an intro to the optics and mechanics of his observatory. It’s a roll-off roof design with a pier that can extend or retract vertically. That’s nice for keeping the eyepiece accessible. He’s got a dedicated state-of-the-art PC running various software to support his speckle interferometry research.

An explanation of speckle interferometry followed. The math is a bit complex, but suffice it to say that you start with a faint double star in the FOV. At high mag you can see it “twinkling” from atmospheric distortion. The two points of light randomly jump all around the FOV. Then you take a few hundred frames of video, saving it as a 3D array of pixels over time.

That image file is next run through a complex mathematical algorithm. In less than a minute two clearly separated circular dots are displayed. These are the binary star components. It’s amazing to witness. Their separation in arcseconds is measured by the software, and the data is logged (at BSO and online).

You may ask: What is this data used for? By plotting the positions of the binary components over time (usually decades) it is possible to determine the orbital parameters. With additional spectroscopic data, much can be learned about the evolution of binary systems, and add fine details to the Hertzsprung-Russel diagram.

So this is real science. Richard currently holds the esteemed position of #3 on the planet for most reported measurements of this type, and he’s happy to show you how it’s done. We tried to organize this as a club event and were shut down by weather 3 times. The flexibility of Richard’s open invitation is sincerely appreciated, and gives all interested members the opportunity of participating. Highly recommended.

3. Telescopes to Tanzania
For the last few months I’ve been involved in this Astronomers Without Borders project. We have a refurbished Cave Cassegrain 10″ manufactured in the early 60s. The optical work was done by an astronomy club in Racine, Wisconsin. The scope is now in my garage, having been transported here in a van by Kai Staats. Our job is to install a new 12 VDC stepping motor drive system to replace the existing 110 VAC synchronous motors. The power grid in Tanzania (when it’s on) provides 220 VAC at 50 Hz, so these new motors were the obvious solution. The drive controller was assembled by Buckman Hardy Associates and AWR Technology, Electronic Engineering Consultants in the UK and just received a week ago. We now need to assemble and test the system before it ships to the Mt. Meru Astronomical Observatory in Tanzania. My workshop has been taken over by telescope parts for a couple months now, but we are nearing completion and hope to ship some time in November.

You can read our latest update (with photos) on the AWB website by clicking here.

4. Astronomical Eye Candy
With the holidays approaching it just seemed like some aurora action would be appropriately festive. This video is by Christian Mülhauser of Norway. The sound track, created for this video, is by Jonathan Geer. You can see more of Mülhauser’s work at:

Till next we meet, clear skies.

Dan Heim
Desert Foothills Astronomy Club

October 2018 DFAC Update