After I bought the D750 I rarely used the D7000 any more. As it has been heavily used it would probably not get a lot if I sold it, so It mostly stayed in the closet.
Then I learned that the Nikon D7000 sensor is still used in current astronomical CMOS cameras (e.g. ASI071MC Pro or QHY168C) apart from the cooled sensor the main advantage of the astronomical cameras is the better response to H-alpha emission because of different IR-cutoff wavelength.
H-alpha emission is the red light created when young, hot stars excite hydrogen gas in the interstellar medium. Regions of onging star birth are usually distinctly red. Sadly regular DSLR cameras pick up that red light only very faintly.
After a discussion with a colleague of the Vorarlberger Amateur Astronomen I plucked up the courage to take the camera apart and get rid of the IR blocking filter. Read More →
The last time I wanted to do some deep-sky astrophotography, I ran into an issue with our astronomy club’s LXD-650 mount – immediately after switching it on the declination motor started to run at high speed.
After some research on the internet I was able to resolve the issue, by tweaking the setting on the potentiometer responsible for the declination encoder LED light.
A test of wide-angle lenses for astrophotography on FX format. The shots were taken from suburban conditions, the camera was mounted on a static tripod without guiding. The left image is always the full frame, the middle one is the center, and the right one is the upper left corner of the image. Read More →
Most people don’ t realize that the bright spots below a tree in the grass are actually images of the sun formed by small holes created through overlapping leaves in the tree’s branches. Because the sun is a sphere, the images are also circular (depending of the angle of the surface).
A similar situation occurs when the sun shines through the small holes in blinds – round images of the sun are projected against the foor or wall. The images become interesting when the sun’s disk is obscured by something, e.g. the moon during a solar eclipse or trees when the sun is rising or setting on a wooded horizon. Read More →
Time-lapse animations have always fascinated me. With a time-lapse you can make things visible to the human eye that are normally happening too slow. The movement of stars in the sky or the process of putting up a house are very interesting to look at when the clock has been accelerated.
Apart form creating time-lapse animations using my own pictures I also found it worthwhile to create them from web-cam images. A webcam near the place I live provides images of quite high resolution. With the little script below, I was able to create this video: Fog over Dornbirn
I found that for videos that include clouds it is ok to take a frame every 5 seconds or so. As I don’t have the time and patience to save the webcam images manually, I created this bash script which was improved by Jürgen Hofer subsequently:
# copyright Philipp Salzgeber - www.salzgeber.at
# adapted by j! for cleaner results
# first cmd line parameter is the delay in seconds (optional, default is 60)
# script stops if there is the file 'killme' in directory (for remote stop via dropbox)
let"pause= $divider * 90 / 100"
#wait for zero crossing
let"mod= $secs % $divider"
let"mod= $secs % $divider"
# create a filename with date and time portion
# use wget to download the current image from the webcam
While in the process of making a photobook in Lightroom I wanted to review the book before actually ordering it. For this I wanted to have the pages in JPEG format instead of one big PDF.
It turns out that with ghostscript one can easily extract the images.
I am using cygwin on a Windows 7 64 Bit operating system to work with ImageMagick, Ghostview and the like.
But before I was able to use ghostscript I had to fix this error I was getting about the font Arial.ttf not being found, after some research I found that creating the missing directories and adding a link to the font in the Windows directory fixes that issue:
Lightning occur during thunderstorms – apart from the dangers of a hunderstorm (floods, hail, storm, breaking branches, falling trees) lightning itself is dangerous, and potentially deadly. So don’t go outside when lightning is near. If 3 seconds pass between lightning and the accompanying thunder-clap the lightning was only 1000m away! More information on lightning can be found here:http://en.wikipedia.org/wiki/Lightning Read More →