Sunday, August 19, 2012

Controlling Canon EOS 1100D with Linux

I bought a DSLR camera mainly for astrophotography. Of course I use it for other photography as well (like 20GiB of photos of our 2 months old son) but reason for buying it was astrophotography. I decided to go as cheap as possible and found a Canon EOS 1100D for 300€. Not bad.

I can set the exposure time for 1100D to max 30s. While this is a long time, it's not enough for photographing nebulae or other dim objects. I got a tracking mount EQ3-2 which is supposed to make possible exposure times of couple of minutes. Still I have to take several exposures of the same object to get total exposures of maybe 20 minutes. I still haven't had a chance to test my equipment because of the summer here in Finland. Too much light even on midnight.

To take exposures longer than 30s I have to use camera's bulb setting. I use mainly Linux at home so I can't use Canon's EOS utility. Luckily there is Gphoto. It doesn't support all the cameras and for a while looked like 1100D wasn't on the supported list. I could take photos and change settings but couldn't get bulb to work. Developers on #gphoto in Freenode were kind to help me out and the correct commands for changing settings and using bulb are:

# gphoto2 --set-config iso=400
# gphoto2 --set-config shutterspeed=bulb
gphoto2 --wait-event=2s --set-config eosremoterelease=Immediate --wait-event=180s --set-config eosremoterelease=Off --wait-event-and-download=5s

The red --wait-event tells camera the exposure time in seconds.

I'll probably get the adapters required to mount camera on EQ3-2 next week and be able to test everything. Later I'm supposed to get a Raspberry Pi (might take two more months) and my plan is to use that to remote control the camera. I'll install Debian on the RasPi and use ssh to control it. If everything works as planned I'll get to sit inside while taking the photos of night sky.

If I blog here about instructions for something I usually write about it to a website as well. Blog doesn't work too well with information that might change and the reason for me to blog is to help others that might be doing the same thing. So you might want to check this page for Gphoto instructions.

Sunday, August 12, 2012

Planning to find Ceres

Last day of my summer vacation... Yesterday I was out rollerblading at 22-23 and it really started to get dark. Closer to midsummer that was the best time since it wasn't so hot anymore, but now, note to self, better go a bit earlier.

Anyways the darkess made me start planning future observations. Some time ago, might have been while watching Venus transition (btw I think I should blog about that as well even though it was months ago) I started thinking if it were possible to see dwarf planet Ceres with my telescope. Checking Wikipedia about Ceres tells me that its magnitude ranges from 6.7 to 9.3. Being still such a beginner at this, I really don't know if that's something I can see from my backyard.

I had taken photos of Orion's sword and Pleiades with Canon SX 200 IS, which is a compact camera with 60mm (or 12x) zoom. The photos were taken with exposure time of 1 and 2 seconds (on a tripod without tracking), 40 shots and then combined with DeepSkyStacker. I compared the photos with star charts (Stellarium) to see how faint magnitudes can be seen where I observe. Here's an example of Pleiades:

Pleiades with a few apparent magnitudes of visible stars.
So... The brightest star on Pleiades is 2.85. There are several stars of approximately magnitude 7. I could even see stars with magnitudes of 10 and 11.25 (according to Stellarium). I'm a little sceptical about that 11.25, but 10 seems reasonable.

For now it looks like it is possible to see Ceres. Nowadays I have better optics (Canon EOS 1100D and max 300mm zoom) and a tracking mount (EQ3-2). And of course I'd like to have a visual observation rather than a photo. First I'm going to find the dwarf planet on camera, then try to see it through a telescope.

Hello World!

For a while now I've been writing a blog about my hobby as a stargazer: Mikon tähtiharrastusblogi (Finnish only). The idea of the blog was to write down notes about everything I learn while looking through my telescope. Another motivation was to learn some web programming. I wrote the whole blog from nothing with PHP.

While this was (and still is) an entertaining project, I found out quickly that also wanted to share more static infromation than my blog makes possible. This blog is an attempt to do just that. Another framework I thought was Google Sites and perhaps that would have been a better choice for the static information... But I also wanted a blog.

My english is far from perfect. I hope I still get understood, and that I don't accidently say anything weird.

Most texts I write here are probably originally from my Finnish blog. The content there is more dynamic and I might do updates several times a day on some topic. I'll try to keep my posts here better planned.