I took some decent photos of the lunar eclipse last night, and it occurred to me how I did it might be of interest to some of you here.
In short, I put my Canon 40D on my 10" Meade LX200 telescope at prime focus. At 2500mm f/10, the moon more than fills the frame and it takes a number of exposures to cover the entire moon. I stitched them in Photoshop CS3 using Photomerge.
Here's one of the images I took during totality. I haven't processed all the data I captured yet.
Here's a bit more detail on what was involved:
1. I have a 10" Meade LX200 GPS UHTC Schmidt-Cassegrain telescope, which besides providing a very long focal length in a compact package, has motors for tracking celestial objects. This is important for lunar eclipse photography, as the exposure times can get fairly long when the sunlight has been blocked by the Earth from reaching the moon.
2. I have added a T-mount with appropriate camera adapter. One end slips into the 2" tube in the electric focuser on the telescope and secures with the thumb screws, and the other mounts to the Canon camera body like a lens. There are no electrical connections in this device.
3. Once I aligned the telescope, a process whereby it figures out (via GPS) where it is on the Earth and what direction it's facing (via a magnetic North sensor) then finally asks me to center two stars, I punched in "Solar System", "Moon", and "GOTO". The mount pointed at the moon and began to track it (not only compensating for the rotation of the Earth, but also including the rotation of the Moon around the Earth). This thing is way cool.
4. With the camera on the scope, and with the eclipse *just* starting, I enabled Live View, got the focus close and locked the mirror down in the scope. Looking at the edge of the moon at 10x in Live View, I fine tuned the focus using the scope's electric microfocuser. I set the camera to ISO 100 and 1/100 second, and took some test JPEGs. I could see some movement in the features of the moon due to atmospheric effects - heat waves. This is typical at this magnification.
5. I switched to Raw mode, and began taking sequences of shots to cover the entire moon every so often to capture the progressing stages of the eclipse. I could probably have done it with as little as 4 shots each, but I took more because I wanted to make sure to have enough overlap to get good mosaics. I used the fine positioning control on the telescope's handset to reframe the image, and my TC80-N3 remote timer controller to trigger the exposures, so as not to jiggle the scope. The difference in brightness between the bright sunlit portion and the part falling in the umbra (full shadow) of the Earth is huge, so I switched to a higher ISO and a longer shutter time to bring out shadow detail.
6. When the eclipse reached totality, I found that I was shooting in ISO 1600 for a full second, which is something like
12 stops slower than I had been shooting when the moon was entirely in the sun.
7. Creating a full mosaic of the fully illuminated or fully eclipsed moon is as easy as running the Photoshop CS3 Photomerge function. It gets more complicated when I need to mix different exposure depths. Fortunately the telescope presents a reasonably flat field to the imager, so stitching is essentially a matter of careful alignment, without need for distortion.
8. At full camera resolution the resultant moon mosaic image comes out to about 30 megapixels, but when the seeing is blurring the features on the moon like it was last night it's not necessary to use such a high resolution. Now that I'm looking over the raw data, I'd say I can use one of the lower resolutions offered by Camera Raw and still come out with a highly detailed image.
I can only imagine how spectacular the Earth looks from the moon during one of these events.
I'll post more of the images in this thread as I process them.
-Noel
It works wonders on the moon, though you have to watch out and compensate for excessive brightening around the edges due to the abrupt drop off in brightness.
Linear Mode
