Sky & Telescope Astrophotography Guide

In Sky & Telescope, images are as important as text. When authors or photographers provide images to us, the quality we can reproduce in the magazine is directly proportional to the quality we get in the first place. How a picture was taken is as important as how it was developed and printed or, for a digital image, how long the total exposures contributing to the final image (through individual color filters, or simply the cumulative exposure time).

Here we'll go over some basic techniques for setting up and taking photographs of astronomical equipment and people, offer tips on processing and printing film photos, and discuss issues related to digital-image acquisition and processing.

For information about submitting photos of astronomical objects, please see our Astro Imager's Guide.

Cameras and Films

Camera quality matters. A high-quality digital single-lens-reflex (DSLR) camera will give a nice, sharp picture — if the lens is focused properly. DSLR’s infinity focus does not translate to perfectly focused stars. You’ll need to find proper focus using one of the common methods discussed in many of the astrophotography article in the magazine. Mid-level to advanced point-and-shoot cameras can also do a respectable job.

Film quality (if you still use film) matters too. Color negative film has a much wider exposure latitude then color slide film, so it's easier to achieve a top-quality scan from negatives. The latest 400-speed films from Kodak, Fuji, and Agfa have great latitude and very fine grain; these are the best choices even for pictures taken in bright daylight, and in some cases still produce a better picture than digital cameras.

Setups, Shots, and Scans

Now lets move on to the actual setup. If you're photographing a white telescope on a sunny day, don't place it in front of a dark background (a tree or building shadows); no matter how good your film, it's going to have a hard time coping with these extremes of bright and dark. Instead, place the scope in front of a large area of evenly lit grass, dirt, or even asphalt; your film will handle the contrast better. Putting the telescope in a large area of open shade can work, but open shade lit by a large expanse of blue sky will lend a blue cast to your photos. Use an 81a or 81b filter to compensate.

The best light for outdoor shots of equipment and people is slight overcast — it evens out the sunlight and helps eliminate harsh shadows. Heavier overcast is fine, but use an 81a filter to warm up the colors. To minimize vibration, mount your camera on a tripod and use a cable or remote shutter release.

Now that digital cameras have become very popular, many of the images sent to us for possible publication are electronic. Although the standard for image resolution is 72 dots per inch (dpi), this is really only for Web and e-mail applications. Magazine publication usually means an image needs to be around 300 dpi. The other default standard is that most cameras save files in JPEG format. This is used so that the camera can squeeze as many images onto a memory card as possible. Unfortunately JPEG compression degrades the image — the higher the compression, the worse the image becomes. Newer and better digital cameras allow you to change the file format that the camera uses to save images. Specify the least amount of JPEG compression or, if possible, switch to TIFF or RAW format. This will result in larger files but produce images of superior quality.

Returning Your Pictures

Although this is becoming rare, when sending slides or prints, be sure to send only copies and keep the originals to guard against loss in the mail or other mishap. Sky & Telescope does not return submitted photos unless specifically requested. While we take special care to prevent damage to film in our possession, we prefer submissions to arrive in digital format, due to our printing process. Prints, slides, and negatives will be returned to you only if you specifically request it. Write the words "Return to [your name and mailing address]" on each slide or print you wish returned. This must be on each photo, not in a separate letter or on a plastic sheet containing many slides. If this becomes tedious when submitting many photographs, we suggest using printed stickers. The information needs to be attached only once to a plastic holder containing a strip of several negatives. If we tell you we plan to use one of your images and you need it back by a particular date, let us know; we will transfer your images to digital format and then return them. Note: We generally do not return digital images supplied on diskettes, CD-ROMs, or other media.

Whether you ask for an image to be returned or not, please supply as much information about it as possible: your name and mailing address, the subject, the date, time, telescope/camera, exposure, film, etc. Again, the best place for this information is right on the print or slide itself; alternatively, you may use our image submission form.

Corresponding with Us

If you have any questions not answered by this guide, please contact us. Thanks for your interest in Sky & Telescope!