|Keith's Moon Photography|
A few topics related to lunar photography...|
Although it is by far the biggest and brightest object in the night sky the moon is not an easy subject to photograph. Using a standard 50mm lens, an image projected onto a slide or negative is only about 1/50 of an inch. Also consider such issues as exposure times, film types, and lenses and you begin to understand what is needed to take photographs of the moon. With the recent introduction of inexpensive digital cameras a whole new area of lunar photography is now available to the amateur. I've included a few things to consider when trying to photograph the moon. Equipment, techniques and even a few formulas are presented.
The Moon As A Source Of Light
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|Lunar Photography Using An SLR Camera|
Determining Image Size on Film|
The formula for determining the size of the lunar images on film is found by dividing the focal length (in millimeters) by 109 to arrive at the lunar diameter (in millimeters) on the film.
Photograph Results With Various Lens Sizes |
Since your subject is primarily black-and-white 400 speed black-and-white film would be a logical choice. Color negative ISO 400 or 800 film would also work. If you bracket a lot, you can use slide film, but there's a greater danger of losing detail because of overexposure if you do. If you follow these simple tips, you'll have no problem if you attempt to photograph the moon.
When you bracket your exposure, it simply means that you make an photograph at the setting you think
is correct, but you also photograph the same subject several more times, making slight changes in either
the shutter speed setting or aperture. For most situations, we suggest that you make one or two images
giving the film less exposure, and one or two that give the film more exposure.
You can't bracket fast-moving subjects-a breaking news photo or sports action shot won't wait long enough for you to make multiple exposures. But the moon (or a landscape or scenic) isn't moving so fast relative to your camera. Therefore, it's always a good idea to bracket your exposure. For our full moon shot, in addition to 1/250 and 1/500 @ f/16, you could give a little less exposure by making a photo at 1/1000 @ f/16, and a little more by shooting at 1/125 @ f/16. You can achieve the same bracket of exposure by keeping your shutter speed at 1/250 but using different aperture openings, such as one exposure each at f/16, f/22, f/11 and f/8.
Exposure Times vs. ISO Film Speeds|
The speed (ISO) of the film being used for lunar photography determines the exposure times due to the varying brightness
phases of the moon. The higher the speed (ISO) of the film, the shorter the exposure. The drawback of using super high speed
films such as the ISO 3200 is that the finished pictures tend to be very grainy especially when enlarged. The following table
gives the exposure times (in seconds) for various speed films at different phases of the moon. Due to atmospheric turbulence
and light pollution, it is best to 'bracket' your exposures. Bracketing consists of taking exposures on both sides of the
recommended shutter speed.
Exposure Times vs. Mount Types|
It is recommended that the camera be used piggyback or as prime focus on a tracking telescope, however, depending on the size
of lens being used, photos can be taken from a tripod. The limiting factor here is to limit the exposure (depending on the lens)
to avoid star trails. Example: for a camera mounted on a tripod using a 50mm lens, the exposure can be approx. 12 seconds to
avoid star trailing; mounted on a driven telescope, the exposure can be up to 4 minutes. The table shows the
maximum exposure times using various lenses with fixed mounts and tracking mounts.
|Examples Of Lunar Photography Using An SLR Camera|
|Here are a few examples of moon photography using a SLR camera. Two of the photos were taken the same evening a few minutes a part. A slightly shorter exposure time combined with waning twilight produced pictures with differing tones and hues. The center photo was taken during hazy conditions and shows the moon fuzzy with little detail. I suggest using foreground objects such as trees or buildings in your photos to give them a more personal touch. Click on any photo for an expanded view.|
|Lunar Photography Through A Telescope|
PRIME FOCUS METHOD|
|This is the simplest method for lunar photography. If you have a catadioptic telescope, such as a Schmidt,Cassegrain or Maksutov, remove the camera lens, and using a simple adapter (T-ring, available at camera stores and astronomical supply houses), attach the camera directly to the telescope (without its eyepiece). The telescope becomes the camera lens, in effect, a very long telephoto lens. For example, a 5-inch Celestron or Meade Schmidt,Cassegrain telescope becomes a 1250mm, f/10 telephoto.|
|This method requires two tripods, one for the camera, and one for the telescope. The camera (with lens) is set up as close to the telescope eyepiece as possible, and focused on the image seen through the cam- era. The exposure time is calculated by determining the focal length (F) and the f/ratio of the telescope system. F = focal length of camera lens x magnification of telescope f/ratio = F/diameter of the telescope objective Magnification of the telescope = focal length of telescope focal length of eyepiece|
|This method requires the use of a special adapter which is much more expensive than the simple T-ring used in the prime focus method. The adapter connects the camera without its lens to the eyepiece of the telescope. This is an advanced method used in most amateur astrophotographers,|
|Digital Lunar Photography|
In the 1990s digital cameras and image processing began to make an impact on the world of photography. Digital imaging will continue to attract more fans as equipment drops and processing power increases. The Internet gives you the ability to publish and exchange information, in the future digital images will be the format of choice.
A few examples of digital lunar photography. Pictures taken
with a Sony MVC-CD1000 digital camera with maximum zoom.
Thanks to Gary Braden for the digital lunar photographs.
Although existing photographs can be turned into digital files, most
amateur astronomers are more excited about capturing images of
the moon directly in a digital format. Cameras that can record digital
images are referred to as CCD instruments.
Each graphic format used to
capture images translates the image's distinctive elements into individual bits, creating a
bitmapped version of the original. CCD stands for charge-
coupled device; a CCD camera projects an image onto a specialized
computer chip (referred to as a CCD chip), which records variations in
light intensity as a set of digital measurements.|
While several digital formats are available most cameras use a compressed format know as JPEG (Joint Photo Expert Group) This format will reduce file size and allow you to store more images for a given amount of camera memory. Although, the more you compress an image, the greater the loss of picture quality. If your particular camera has this option, try taken lunar photographs using the black and white mode. CCD images captured in black and white can actually turn out sharper than those taken while in the color mode.
Advantages of Digital Photography
Disadvantages of Digital Photography
Disadvantages of Digital Photography
|A Few Ideas And Suggestions|
|For more general information on photographing the night sky visit my Tripod Astrophotography site. Here you'll find lots of information about equipment (Cameras, tripods and cable releases), accessories, films, image processing, etc. All the things needed to get you started in the hobby of wide-field astrophotography.||