Stitching the sky
Strangely, the other day I was thinking of giving my friend a call and using his Maksutov-Cassegrain and my Nikon D200 to do a stitch of the moon.
I should mention that when doing a stitch of an object as distant as the moon that parallax isn’t going to matter so you don’t need to rotate about the optical center when taking the photos.
One very amazing thing about this photo is that Noel brought out the colors of the moon by upping the saturation a lot in Photoshop. That’s an amazing idea since the moon is very grey and neutral colored.
Maybe you have to download the full 15 megapixel version to really appreciate it.
I’ll have to try that trick sometime.
Photographing the moon
First realize that the moon is directly reflecting the sunlight of the sun. This means that, believe it or not, it is going to photograph at a “Sunny f/16”. The typical way to do this is to spot meter directly on the moon and maybe adjust the exposure depending on how large your spot meter is.
Since they aren’t nearly bright as the moon, the stars were added in later. I don’t know what part of the star field he used in the shot. I don’t know if that sort of thing is “cheating,” but I did a similar three exposure shot in order to get the moon, the halo around it, and the redwood branches that I was peering through:
After you photograph the moon, be sure to sharpen it. A lot. Trust me. 🙂
The photo he took was 15 exposures at 1/5 of a second at ISO 100. The aperture was f/20. Based on what I said above, this may sound overexposed, however I think that is because a lot of light is lost in the mirrors of the telescope.
If it were anything other than the moon, his camera (a Canon EOS 20D) would be a great camera for this sort of thing. Besides being 8 megapixel (1.6x 35mm), the CMOS means that it won’t draw as much power for long exposure shots. You see, besides battery life, power has to go somewhere and it gets released in heat in the image processing circuitry. This heat will set off the photodiodes in the sensor. This is one of the two areas where the “Long Exposure NR” has to kick in on the Nikon D70 to reduce a redness that appears in the corner of the image.
(The other is due to to light leak from the viewfinder if you don’t remember to use the provided viewfinder cover when taking a long exposure.)
By the way, CCDs are much less noisy than CMOS. This explains why it is used for professional astrophotography: They can put the image processing circuitry in a cooling bath and use the inherent advantages of CCD’s larger photo collection area to produce noise free photographs. Unfortunately, for us consumers (and Nikon fanatics) it makes CMOS dSLRs slightly better for night photography.
This is why Canon try to capitalize on it with the short-lived Canon EOS 20Da, which was basically the 20D with the Canon’s egregiously aggressive hot-mirror removed from the sensor stack. (It also had a transmissive mirror for live focusing on the LCD mirror, but I don’t know why/how/if this worked.)
He used a Meade LX200 GPS UHTC 10″ Schmidt-Cassegrain telescope. Unfortunately, I don’t know much about astronomy to talk about this—as you can imagine I was surrounded by “my betters” throughout college when it came to this subject.
You’ll have to read about it and tell me. 😀