Galileo's Camera

We are going through the monsoon season again, and well needless to say, not a very great period for astrophotography. Had somewhat of a clear sky today and decided to snap some quick photos and stack them using Deep Sky Stacker. Crux - The Southern Cross In the image above, in the thumbnail view, the main stars of crux is quite obvious. However, when you see the full sized image, you will see that the image is pretty detailed. The top most star is Gamma Crucis. The right most point of the cross is Delta Crucis. The brightest start of the constellation is Alpha Crucis, or the bottom-most star in the constellation. However what interested me was Mimosa (or Beta Crucis), the left most point of the cross. The open cluster NGC4755 resides close to Beta Crucis. This being my very first deep sky imaging attempt (or at least the first decent one), I did not expect much and kept shooting with my 75-300mm lens on a 550D. NGC 4755 Obviously the shot isn't great. But I believe

With all the preparation yesterday and day before, I was quite hopeful that I could get a few decent shots of the transit. I was specifically planning for one good shot through the telescope and a time-lapse shot of the transit across the solar disc. So imagine my delight when I work up today morning and found this greeting me: So much for the plans of scope photography! Managed to capture this during the small time sun was visible, and had it not been for that, my plans for the next century might have needed considerable reconsideration. Transit of Venus - 06 Jun 2012, between 09:10-09:15 local time Sri Lanka

Just a quick post on viewing the transit of Venus tomorrow: Timing You can find timing related information from http://eclipse.gsfc.nasa.gov/transit/venus/city12-1.html and http://eclipse.gsfc.nasa.gov/OH/transit12.html . For those of us from Sri Lanka, the transit will be visible from the sunrise it self. The peak of the transit would be around 07:30 AM. The transit will end around 10:21 AM. The latter link actually has a nice image of the path of Venus across the sun. Viewing Do not use sunglasses or xray film to look at the sun. Most of the damage that happens to the eye can happen due to the wavelengths which are not visible. If you do have xray film and a camera/webcam with a reasonably good zoom, put the xray film in front of the lens and use the live-view of the camera to view the transit (or you can hook it up to a laptop). It is also possible to use a pinhole camera to project the image of the sun to a wall. During 2010 annular eclipse, I came across a natural pinho

After getting necessary film to cover the whole aperture of the lens, I decided to try out a few shots in the morning. Starting off with the highest shutter speed of 1/4000, I realised that even that gives a VERY bright picture (as opposed to the 1/80-1/40 shutter speed which gave a "reasonably ok" view yesterday). Now here's a bit of math. The "brightness" of the image is dependent on both the expose time and the aperture. The expose time has a linear effect (i.e. you expose for 2 seconds, you get twice more light than when you keep it open for 1 second). What sort of an effect does aperture have? Assuming aperture is measured as a diameter of the lens/opening (and that it is circular), the area that is open is given by pi*(d/2)^2 where d is the diameter of the aperture. The area it self has a linear effect on the brightness as well. I.e. you let twice as much as light in for the same period of time, you get an image that is bright twice as more. If the tw

I noticed quite late that we are going to have another Venus - Solar transit in a few days and that is going to be the last Venus transit for almost a century. I have not done any serious solar viewing or photography before this. But the rarity of the event and the equipment I have now wants me to take a shot at it. It goes without saying that you need a solar filter. Over here in in SL, they are a bit too hard to come by. Previously when I was photographing and viewing the annular solar eclipse in 2010, I used a cut up x-ray film with my Canon S2IS (this method is debated). The problem this time is that I now have a Canon 550D, whose lenses have a much larger aperture and the original x-ray cut ups wouldn't work anymore. 1st attempt: Use a type of coloured cellophane that is available over here as a filter. A single sheet is way too thin so tried stacking up about 10-12 on each other. However it diffuses the light so much that it is barely of any use. 2nd attempt: Center the