Sunlight through the Clouds

When I first saw one of these types in Mr. Dilip Kumar’s album, I was really impressed. He mentioned that I’d get several opportunities to take such photographs during the cloudy months, and I did. Here are a few, obviously processed to enhance (?) their beauty:

Yay!

I got this:

Many thanks to pradeepto and techno_freak

LASER diffraction off a CD-ROM

I recently took a photo of LASER diffraction off a CD. Some of my friends (and I) liked it, so I thought it should appear on my blog as well. So here it is:

I’ve labelled the various beams that you see in the photograph in this version:

Trivia: Why is the second maximum beam (n=2) brighter than the first maximum beam (n=1)?

I was able to roughly estimate that the CD’s tracks are about a micrometre apart and that the pits containing the data are either further apart than that, or show a regularity on a larger scale than that. Need to do some more qualitative experiments on that.

The photo is a 15 second exposure at f/3.5 @ ISO 1600. Released to public domain. Credits requested.

Alien from StarWars pays amateur astronomer a visit

This was about an hour ago in my room. The chappy landed in a U.F.O. on my terrace and communicated with me that he wanted some fundaes on amateur astronomy. Requested him for a pose:

Thanks Amar! Now showing people the stars will be much easier! I tested out this stuff today and the beam was good enough to point to the stars.

Playing around with the Camera.

For some reason, I was not in a mood to sit at my computer tonight. I was lazing around when I noticed that the skies were clear and the moon, close to Jupiter, made a nice sight. I rushed to the terrace with my camera, but without my tripod. I was too lazy to get my tripod, so I did other interesting things than take boring constellation photographs from city skies. Here’s the outcome of one of them:

The writing is with the moon and the decorations are with a tubelight!

Farewell treat by Varun and KMap

We have two major FOSS icons of IIT Madras leaving the institute this year – Varun Hiremath, going to become an MTech in Aerospace Engg, Debian Developer, Contributor to Jajuk, going to Cornell; and Kumar Appaiah, going to become an MTech in Electrical Engg, Debian Developer, Contributor to SciPy etc, going to University of Texas at Austin.

We demanded a treat! A wonderful treat it was, indeed. [Thanks a lot Varun, Kumar!]

Group photo after we came back to our campus:

Everyone wore a “Linux” T-Shirt to the treat, except for Prakash, who woke up just then and came in a hurry.

Canon EOS 400D and Linux – Expt1

I was all excited when my new Canon EOS 400D landed in my hands today. I think that it’s a great piece of equipment, although I haven’t yet played around with it enough.

I thought I needed to buy a separate cable to computer-control it, and the USB cable was only a data transfer cable. I casually asked about software for EOS 400D on Linux on ##astronomy on freenode, and I was excited when ‘peerce’ told me that I should’ve got the USB cable for computer-control along with the camera! I ran down and brought the cable and connected the camera to my brother’s system, running Debian (testing).

I didn’t find a good “HOWTO” for the Canon EOS 400D detailing the remote-controlled capture, although I expected that somebody would’ve written one. (I think I should write one when I fully explore it, if someone else hasn’t!)

File transfer was trivially easy:

sudo apt-get install gphoto2 gtkam

gtkam

Select the ‘Add Camera’ option from the ‘Camera’ menu and say ‘Detect’.  Then click ‘Ok’. If the camera doesn’t initialize, try restarting the camera   (May not be the right way to do things). If gtkam doesn’t segfault or run into some trouble, you should see a list of thumbnails on the right half of the window, if you select the right thing (the only thing) in the tree on the left pane. Figure out, it’s quite intuitive, and it doesn’t work well   Maybe there are better methods to do this – maybe the konqueror camera:/ kioslave (or whatever it’s called) works better – please let me know in that case.

Now, I want to control my camera. So I look around for documentation. I understand that it is just

gphoto –set-config capture=on

gphoto2 -F <# of frames> -I <interval> –capture-image

That didn’t seem to work. After much experimentation, I tend to think that the camera needs details of how you want to photograph – i.e. focusing, exposure settings etc. (or does it?). Besides, capture=on must be set in the same command as the –capture-image, or so it seems, probably because every gphoto2 command sends a whole bunch of other instructions to the camera as well (isn’t that inefficient???).

So, that means that if I put the camera on Auto Mode using the Mode dial, then I can get away with:

gphoto2 –set-config capture=on  -F 1 -I 1 –capture-image

For some reason, the command doesn’t terminate (and consequently, F > 1 doesn’t work) – probably because it wants us to accept the image and save it as well. I still need to figure this out.

One more thing that I see is that if I do a

gphoto2 –list-config

I get only three options:

 /main/settings/capturetarget
/main/settings/capture
/main/capturesettings/focuslock

This is expected (after reading the documentation), because the remaining settings that pertain to capture mode are exposed only after we enable capture mode. So do a

gphoto2 –set-config capture=on –list-config

and you get a whole bunch of configurable parameters:

 /main/settings/eos-time
/main/settings/capturetarget
/main/settings/capture
/main/imgsettings/eos-iso
/main/imgsettings/eos-whitebalance
/main/capturesettings/picturestyle
/main/capturesettings/eos-aperture
/main/capturesettings/eos-shutterspeed
/main/capturesettings/eos-meteringmode
/main/capturesettings/focuslock

Ahh… so there we go. So, if I wanted a (semi-)successful manual exposure, I should do:

gphoto2 –set-config capture=on –config -F <Nf> -I <Ti> –capture-image

I still need to figure out how to retrieve the file or somehow get the command to complete.

Earlier, my AF exposures would fail, because I was trying to shoot a blank wall, so AF would fail! It took me really really long to realize that!

The following documentation will prove to be sparingly helpful:

•  http://gphoto.sourceforge.net/doc/remote/
• http://korrekt.org/page/Running_Canon_EOS_400D_under_Linux
• http://gphoto.sourceforge.net/doc/manual/using-gphoto2.html
• http://gphoto.sourceforge.net/doc/manual/ref-gphoto2-cli.html