Donnie’s Blog

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.

It’s strange but true. The more sophisticated things get, the less you can actually do with them.

I tried setting up my Canon 40D with the new telescope to see how it does with prime-focus astrophotography. “Prime-focus astrophotography” is where the telescope functions as the camera’s lens. There are other ways to connect a camera to a telescope, but that is the simplest one, and best for deep-sky objects. I wanted to see whether there was any vignetting, how sharp the images look, and all that kind of stuff. Instead, all I get is:

    Err 01
    Communications between the camera and lens is faulty.
    Clean the lens contacts.

Um, of course the camera can’t communicate with the lens. The telescope mount certainly doesn’t have any electronics built in.

So, I read the manual to see if there was a way to tell the camera to ignore a “missing” lens. Nope. Search around on the Internet for a way around this? No dice. Call Canon tech support. That was the infuriating one - they acted like this was a silly thing to want. To take a photograph without a lens? Who would want to do something like that??!

Guess what - the 20D can do it! I’m sure glad I still have my 20D…

Yes yes, I just wrote about getting a new Canon 40D camera, but DSLRs aren’t always convenient, so it’s nice to have a point-and-shoot camera for casual use. I was initially looking at a much smaller and simpler P&S camera, but then I remembered that I’m an obsessive-compulsive control freak. Fortunately the G9 just came out, so I thought I would give it a try.

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I picked up one of the new Canon 40D cameras yesterday. People have been going nuts about this new model, and they are pretty hard to get a hold of. Fortunately they started showing up at Best Buy and I was able to land one before they were sold out, so lucky me.

I took some photos of the frogs in Baxter pond, with my 100mm macro lens. I also tried out the 28-135mm IS lens that came with the camera - getting the body-only package is going to be nearly impossible for a while - and as expected, I really don’t like the lens. I will have to get a wide-angle EF-S lens later on, and hopefully unload that 28-135mm lens relatively quickly.

Overall I am pretty happy with the camera so far. It has some nice features, and the camera is faster and more responsive than my old 20D. Also, the 40D LCD display is significantly larger than the 20D LCD, which makes it easier to review what you’ve just done. The only thing I am a little concerned about is that the noise becomes noticeable pretty quickly at ISO400 and up, but this seems to be what happens when sensors get larger and larger.

I will have to give this camera a try with the ol’ telescope and see how it goes. The 40D has this new LiveView feature that will hopefully facilitate getting sharp focus. I expect that the camera will work well for photographing the planets. A question in my mind is how it will do with deep-sky objects where you must take multiple long exposures at low ISO settings. If the noise still shows up at ISO100 then it’s going to be annoying, but the beauty of stacking multiple images is that the signal-to-noise ratio improves pretty quickly as you combine more images together, so it isn’t too big a deal.

Of course, the real solution for astrophotography is to get a dedicated CCD imager from a company like SBIG, but the ones I want all cost at least $5000, and I can’t get to dark-sky sites frequently enough to make it worth the price. I think that is one of those “when I retire” things.

A couple of nights ago I was turning off the lights, and I was freaked out by this gimongous moth that had landed on the screen door. I have seen some large moths before, but this was probably the largest. Of course I had to document this amazing creature, so I snapped off a bunch of photos using my macro lens. The detail is just amazing.

While I was out there I discovered why we have frogs in our pond this year. So I took a few photos of the frogs too. Again, the detail is awesome, especially the frogs’ black and golden eyes.

I think I am getting the hang of how to photograph insects at night. If they are willing to put up with the flash (and not all are willing), I try to close the aperture as much as possible to maximize the depth of field. With the macro lens the depth of field can be as small as only a couple millimeters. So, I switch the camera into full-manual mode, bump the flash up a few stops, close the aperture down as much as possible, and try a reasonably fast shutter speed to compensate for the lack of a tripod. I am pretty pleased with these photos; I think they are some of my best yet.

Now that the term is over and summer is here, I am getting to catch up on a few maintenance tasks here and there. One of the things I did was to get my photo gallery software back up and running.

I also have a ton of backlogged photos that I need to post, so hopefully I will get everything onto my website soon. To kick it all off, here are some photos of praying mantises that were hanging out in my back yard. These photos are from last year. I just saw my first mantis for this year, so I expect to take more photos soon!

Late summer always seems to be the best time of year for me to photograph big orb-web spiders. They’re all over the yard, and they’ve had time to get nice and big. In the past I only had a film camera to use with my macro lens, so it always took a while to actually see the results. Then there’s the difficulty of getting a nice, sharp close-up at night. The depth of field on a macro lens is already very narrow, and it’s even harder when the subject is floating back and forth on its web…

But, this time both problems were solved. Now I have a good digital SLR that I can use with my macro lens, so I can see the results right away, and even correct any issues I might encounter. Also, the spider happened to build its web on the front porch, directly across from the porch light. (A good place for a web, I must say!) So, I took 20-30 photos of the little beast, and a few of them actually turned out OK.

Check out the photos! This is my new “Insects” album; I’ll be uploading some other photos of dragonflies and praying mantises that I took this summer too.

To break up the monotony of grading for hours on end, I’ve been sneaking out in the early afternoons to take pictures of the interesting plants and animals in Baxter pond. It has been a lot of fun, and quite refreshing!

Today I brought in my macro lens from home, so that I could get closer photos of the things I saw, and that turned out great. I still have to upload these photos to my photo-gallery, but here is a sneak peek:

Last night I actually scraped together the energy to get out the ol’ telescope. Jupiter is out early at night, and the weather has finally started being clear at night, and I had never used my new Canon 20D camera with my telescope, so I decided to take advantage of the opportunity.

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