> STACKED IMAGE VS. LONG EXPOSURE
Witch is better. Stack or long exposure? It depends…
Long exposure will reveal more details but stack will improve the contrast and faint details by decreasing the background noise. It also decrees the atmosphere turbulence winch as the noise has a random distribution (of course this is more obvious for short exposures)
Long exposure is also hard to shoot as you need guider setup. Also at my place there is a lot of wind, so this is a hard thing to do. Best is to estimate the limited exposure of the sky background and do a stack with that exposure. To estimate it look at the histogram the peak should be 1/3 away from the left.
Below is a comparison of Galaxy M33 between long shot – 80 seconds at ISO 51200 and stack of 20 frames by 30 sec. at ISO 12800.
The single frame is easier to process but stacked frame give us more signal to noise ratio. We can always add more and more signal by taking extra frames. You can use higher ISO and reduce the noise that way.
SKY is the limit :)
One shot:
Stack:
Recently I got one very good lens the Asahi Takumar 135mm 1:2.5. This is fast telephoto lens and from my point of view a good lens should be with aperture from 1:1,2 to 1:2,8.
Moon at 45% illumination and 70x magnification. With aperture of 200mm,14,1 stops dynamic range, color depth of 23.7 bits at this image there are slight color variation on the moon surface that reveals it’s structure.
This is the beginning of my research on how dark the sky could be and what is benefit of a dark sky for astrophotography. I was inspired from those 2 sites. First one presents mathematical model of how dark the sky is.
You can find my last DSLR Astrophotography article in Bulgarian at page 76. I am sharing my last findings for this publication, Specially written for the Institute of Astronomy.
Satellites, cosmic trash or UFOs, the moving spots are everywhere on the sky. Typical satellite behavior is to reflect sun light. It should be yellow or white and could fade and shine due to its rotation.