Astrophotography with the Canon G2 Camera

Is the Canon G2 digital camera any good for astrophotography? What are some of the things to watch out for? I've used my G2 for astrophotography periodically, and I've collected some of my experiences and notes here for others with the G2 to peruse.

Overview

The Canon G2 camera is a great camera, especially for normal use, but its performance in astrophotography really depends on what you're trying to do with it. It is generally quite good for bright objects in the sky, such as the moon or naked eye planets, but it is not well suited for taking photos of deep-sky objects.

Here are the strengths of the Canon G2 for astrophotography:

• Very convenient for getting digital photograph data - no film scanners or photo scanners to muck with.
• Can take up to 30-second movies at 320x200 pixels, for image stacking. This lets you achieve far sharper images that show more detail.
• The Canon G2 comes with a remote control for easy shutter control, to avoid annoying vibrations when taking photos.

Here are some of the weaknesses of the Canon G2 camera when it comes to astrophotography:

• Large lens causes significant issues with vignetting when afocally coupled to a telescope.
• Longest exposure length is 15 seconds; there is no Bulb setting for long-exposure photographs that bring out faint objects.
• Without an external monitor hooked to the camera, it is difficult to focus very well in a telescope setup.

What this means is that if you are interested in taking photos of the sun (ONLY DO SO WITH SAFE SOLAR FILTERS IN PLACE!!!), moon, or naked-eye planets, you will probably be quite satisfied with your results. Land photography (bird or nature photography, for example) is also quite feasible with this setup. But, don't expect to get much if you go for the deep-sky photography or any photography that requires long exposure times; this camera simply isn't designed for those kind of tasks.

Now, you may still be able to get decent photos of reasonably bright deep-sky objects by taking several 15-second exposures at the camera's ISO400 setting, and then stacking the images with appropriate software. I have not personally experimented with this technique, but I have heard that others have had decent success with this approach. Once I experiment with this, I will put my results up here as well.

Now that I've gone through that overview, here are some more details on the general points I have outlined.

Vignetting

Vignetting is the single most annoying challenge to deal with on the Canon G2. Without taking special measures, you can easily end up with highly unsatisfying photos like these:

These were all taken through an 8" aperature Meade LX200 SCT, using the standard Meade 26mm Plossl eyepiece, and a variable-length eyepiece-projection adapter also made by Meade. The vignetting is so bad quite simply because there is a LOT of space between the eyepiece and the camera, and the camera's lens is significantly larger than the eyepiece's lens.

All hope is not lost, however. There is an eyepiece made by a company called ScopeTronix, called the MaxView 40. It is extremely helpful in minimizing the effects of vignetting when using the Canon G2. It does this by providing T-adapter threads right on the end of the eyepiece, so that the distance between the eyepiece and the camera's lens can be brought to an absolute minimum.

(ScopeTronix provides a very helpful document outlining some of the challenges of digital camera astrophotography. I highly recommend reading it; it is very useful. The document may be accessed here.)

Using the MaxView 40 eyepiece yields a tremendous improvement with the vignetting issue; however, you will see that the problem is not completely resolved. Here are several photos demonstrating the capabilities of the MaxView 40 when it comes to eliminating vignetting. Note that the MaxView 40 has an adjustable sleeve, allowing one to vary the distance between the camera and the eyepiece. Also, minimal vignetting is typically seen when the camera is completely zoomed in. These photos show the whole range of both camera zooming and MaxView 40 sleeve adjustments. You will see how dramatic the impact can be!

These photos are of a branch in a large tree, near dusk, from about 100' away. Some of the photos ended up with a shutter-speed of up to 1 second to take decent photos; that is why the leaves are blurred in some of the shots. The point is not the sharpness though; it's the ability of the MaxView 40 to minimize vignetting.

The following image shows the Canon G2 zoomed all the way out, and the maximal distance between the MaxView 40 and the camera lens:

The following image shows the Canon G2 zoomed all the way in (3x optical zoom), and the maximal distance between the MaxView 40 and the camera lens:

The following image shows the Canon G2 zoomed all the way out, and the minimal distance between the MaxView 40 and the camera lens. Note that there is a slight change in the brightness near the edge of the viewing area.

The following image shows the Canon G2 zoomed all the way out, and the MaxView 40 setting adjusted to minimize the brightness change near the edges of the viewing area. This result was achieved with the MaxView 40 set to about 1/8" from the closest setting.

This image shows the Canon G2 zoomed all the way in (3x optical zoom), and the MaxView 40 is about 1/8" away from the closest setting between camera and telescope. Note that there is still noticeable vignetting at the corners, and there is a gradient in brightness from the center to the outside.

This image shows the Canon G2 zoomed all the way in (3x optical zoom), and the MaxView 40 is at the closest setting between camera and telescope. The vignetting is less than the previous photo, but still noticeable.