Planetary Photography

When it comes to planetary photography, there are two distinct methods for capturing or creating planetary images. When I say capture I am referring to the traditional method of photographing an image. Originally we used photographic film which is covered in light sensitive crystals (silver halide) that vary in size depending on the film’s speed. The slowest films, ISO 100 or less, had very fine grains of these crystals that were quite slow to react to light.

As the films got faster, the size of the grains had to grow to make them more sensitive to light. Consequently the pictures became less and less detailed (or grainy). ISO numbers use a doubling scale to reflect their sensitivity such as 25, 50, 100, 200, 400, 800, 1600, and 3200. With modern digital cameras we still use that scale today even though we don’t use film.

The other method is to create the image using multiple exposures and a piece of Free software (see below for link) to process your shots into something surprisingly good.

Traditional Capture

Now you could do so with a film camera on a mount and a two metre long telephoto lens (2000 mm effective length, say a 650mm and a 3x Barlow) but that would be insanely difficult and very costly in terms of film. Even a large expensive roll of film only has 36 exposures on it; each roll costs money to develop and there is no guarantee you have a good shot anywhere on the roll.

Most people have switched to digital cameras, particularly Digital Single Lens Reflex (DSLR) cameras that show you through the viewfinder exactly what the lens will see when you click the shutter. If you haven’t purchased yours yet, consider getting a 24 Megapixel camera with a 10x zoom on the viewfinder and (for other reasons) a Long Exposure Noise Reduction feature. These are generally well suited to astrophotography.

Telescopes

Instead, of buying expensive dedicated camera lenses, practical people will pick up a nice telescope for this sort of work. Personally my preference is for reflectors, since they are relatively inexpensive for surprisingly good quality. Mirrors, in my opinion, eliminate chromatic aberrations better than inexpensive refractor telescopes. And expensive refractors ($800-5000) deliver equivalent images to a relatively inexpensive reflector ($200-600).

Modern-Age Planet Photograph Creation

The new trick is to use a digital webcam and attach it to your telescope in place of a DSLR camera. Why? These cute little guys have a relatively small CCD (Charge Coupled Device) light collector that is ideally sized to capture a planet image, plus they can handle 30-60 frames per second.

After

After

Before

Since you’re trying to achieve between a ½0th and a ⅙0th of a second of exposure time you can get thousands of frames per minute, which, as you can imagine, is impossible with 36 exposures on a roll of film. Of course looking at all those images in any meaningful sort of way would be ridiculously difficult. For that we have a FREE piece of software that sorts through your massive image collection and picks out all the best ones then stacks them on top of each other reinforcing identical pixels from image to image and eliminating spurious ones.

What you will Need

  • A good solid tripod, especially if it is a bit windy
  • A Barlow lens (2x or 3x)
  • Something to keep your lenses from fogging up (cloth wrap and elastic bands work)
  • Fully charged batteries, as long exposures are draining, or somewhere to plug in
  • A hat and thermos of hot drink
  • A remote trigger for the camera (radio, infrared, or squeeze bulb)
  • A Star Chart to find your target
  • MP3 player or book to fill the time during long exposures

Limited Planetary Targets

Neptune - Post Processing

Neptune – Post Processing

Neptune - Pre Processing

Neptune – Pre Processing

For the most part what you’re going to be able to image will be Mars, the Moon, Jupiter, and Saturn. We’re got a few other things in the Solar System such as Ceres and other planetesimals in the Asteroid Belt. I’ve seen an image of Neptune done with this method and it was quite impressive when you consider that the pre-processed image is almost non-existent. Time exposure was 100ms with almost maximum gain for the image (usually a horrible idea but it works with Neptune) and you get a (true) blue color that no other planet presents (except Earth).

Conclusion

Ultimately it comes down to experimentation. You’ll have to find what satisfies you personally. If you haven’t purchased your equipment yet, join a local astronomy club, if there is one, and learn to use other people’s telescopes and seek out their advice for DSLR cameras or CCDs. That will be the best guide as to what you want for yourself.

No Comments

    Leave a reply