Donnie’s Blog

Saturday, November 10 was the ACM regional programming contest. Caltech won yet again… Go Caltech!

This year was definitely one of the least intentional wins. There was little interest in an ACM programming contest track for CS11, so we just didn’t have one. Then, two weeks before the contest was scheduled, some all-star students expressed interest in going, so we arranged it. And they won! Caltech rocks.

Anyway. Hopefully we won’t do it this way ever again. Next year I want to really try to drum up interest in the contest and actually get 3 or 4 teams out there. But at least we were able to land the win this year!

A week ago, Caltech had its very first olive harvest. Caltech has many olive trees all over campus, and usually they are quite a nuisance because they fall on the ground, get squished under foot, and leave oily splotches on the concrete for months. In the past, the grounds crew would spray the trees to get them to produce less, but then two students decided to pick some olives and make olive oil out of them. (A very clever way to avoid homework, I must say.) Once the students succeeded at producing some actual olive oil, the administration decided to make an annual event of this.

So, call me crazy, but I would think that after an “olive harvest,” there wouldn’t be any olives on the trees anymore after that. Yet for the last week I have been walking around campus and looking at those trees, and guess what — still lots of olives.

I’m pretty annoyed by this. My coworkers think my standards are too high, but if you’re going to do something, do it right. No Olive Left Behind.

Now that I have had a couple of serious astrophotography experiences with my new Canon 40D, I figured that I should actually write a bit about it. Before the 40D I used a 20D, which was certainly better than film, but I never was really able to achieve the level that I wanted to. The primary problem is invariably achieving a good focus. There are several techniques for getting a good focus, the best of which is probably using a focusing aid like the Kendrick Kwik Focus. The concept is simple - when the telescope is out of focus, the light takes on the shape of the aperture of the telescope, central obstruction and all. Thus, if you put a mask on the front of the telescope with two or three holes, you see two or three spots if the scope is out of focus. But, once the telescope is brought into focus, all of those spots converge, and you see only one image.

Aside: Most focusing aids use circular holes, but if you are making your own focusing aid (and why wouldn’t you?) you probably would do best with triangles at different orientations, rather than circles. This way you get some diffraction spikes as well, and when they are all centered around one point in the field of view, you know you are in focus.

There is one feature on the 40D that hands-down makes it a sheer joy to work with: Live View! Live View lets you get a really good look at what is coming into the camera, before you actually take any photos. This means you can point the telescope at a bright star, switch on Live View, zoom in on the image, and get a really good focus on that star before taking any photos. I have used Live View for both piggyback-mount photography and prime-focus photography, and it is just great for getting a good sharp focus. (I do have to say though, nothing shows the ugly realities about the quality of your camera lenses like focusing on a star. Oh well…)

The Canon 40D has a number of other nice features for use with astrophotography. I always switch the camera into timer-mode and set the mirror to pre-fire so that there is as little motion as possible when the photo is taken. (Even with that, there is still vibration from the shutter, but you can see my previous post for details about that.) I also use the TC80-N3 timer-remote to control the camera without touching it. Of course, the main feature I use is the timed-exposure functionality; the other features of that remote aren’t so relevant to astrophotography. If you switch the camera into M (manual) mode, turn on the camera’s 10-second timer, and set the timer-remote to your desired exposure length plus 10 seconds, everything works great. The only hard part is sitting there waiting to see the results.

That is about all I have to say about using the 40D for astrophotography at this point. I don’t know much about “frequency-response curves,” how suitable the camera is for imaging hydrogen-alpha wavelengths of light, or anything like that. I’m an amateur. I just know that this camera is a whole lot easier to use than the 20D, and it really has me motivated to get out of the city a bit more often to take some pictures of the sky. I’m happy with that!

For the last couple of weeks there has been a strange, tailless comet in the constellation Perseus. It started getting more attention in the news when it suddenly brightened, so it’s one of the more popular things in the sky at the moment. Hopefully it will be around for a while; you don’t normally have things that easy to see from the city.

Now, usually I would be whining about how much I hate comets, but this time I was actually able to find it myself, so this one is okay.

Here is a wide-field photo of Holmes, taken with my camera mounted piggyback on my telescope, using a 100mm macro lens:

And, here is a close-up taken through the telescope:

You can see some vibration in the close-up photo. I am pretty sure this was caused by the shutter when I took the photo. Normally I set the mirror to pre-fire, and I take photos on a timer, so I can’t think of anything else that could cause any vibrations.

There is this technique called the “hat trick” (at least, that’s what Michael Covington called it in his great book on astrophotography), which is the simple solution to this problem. Put something large and dark in front of the telescope - say, a hat - start the exposure, then move the hat out of the way. That way there will be absolutely no vibrations during the exposure.