Basic Astrophotography

By Bill Huegerich

Any digital or film camera, depending on what you want to photograph (DSLR’s are great for many subjects).

High sensitivity sensor or film (ISO 400 or higher)

Tripod or tracking mount are helpful. Self timer or cable release. Bulb setting often needed.

Earth’s rotation causes stars to trail in long exposures. Equatorial mount/barndoor tracker can adjust camera

and/or telescope to follow rotation Polaris (the North star)

Almost directly off the Northern axis of the earth, stays in same position.

Everything else in sky appears to rotate around this axis.

Use skymap to find and identify things in space. www.skymaps.com

Night vision It takes your eyes about 30 minutes to adjust to dark. Use red LED flashlight to preserve night vision.

Done with normal camera lenses (wide angle is easier to work with.

Can photograph Milkyway, constellations, meteor showers, comets, etc.

Fast lenses better to reduce exposure times (f/1.8 much better than f/4.)

ISO 400 or higher sensitivity. Long exposure noise reduction will help reduce

noise, but takes twice as long to create one exposure.

Try 10-30 second exposures.

Use solid tripod. The longer the exposure, the longer the

star trails. Try ISO 400. Use smaller aperture (f/5.6 or f/8).

Will reduce sky glow from nearby towns/lights. Have fresh batteries in your camera. Star trails will rotate around Polaris. Shoot from a dark location.

Brightest object in night sky, similar to photographing on earth in daylight.

Easily done with normal zoom lenses (long focal length) on any type of camera.

Webcams have become popular for lunar photography.

Thinner crescent moons show craters and mountains better because of side lighting.

This is one of the best first target for astrophotography.

Requires extreme focal length telescopes (4,000-5,000 mm common for these shots.

Dedicated astrophotograpy CCD cameras and webcams best for planetary photography.

SLR’s not good due to shutter vibration and mirror slap.

Generally done with video to stack hundreds of frames to increase signal to noise ratio.

DSO’s are generally very dim and require very long exposures and/or many shorter exposures stacked together.

They generally require tracking the earth’s rotation in order to get long enough exposures with long focal length lenses.

Other galaxies, nebulae, and star clusters would fall into this category.

Trial and error. Start with high ISO (1600-3200) and take

quick exposure with lens wide open. Preview image on LCD screen and zoom in

as far as possible on a single star. Examine star, you want as close to a pin-

point star as possible. Slightly adjust focus and repeat until you get

best focus. Tape focus ring down and change settings

for real exposures.

Ronchi focus screen. Magnified angle finder. DSLR Focus or other software based aids. Hartman mask. Focus on something at infinity during day

and tape down focus ring. Live view – focus on live view zoomed in

as far as possible.

Light pollution will create skyglow in your images. Get away from street lights and cities.

Wait until well after sunset for sky to get as dark as possible.

Tracking can be difficult, especially with longer focal lengths.

Focus, focus, focus (autofocus not very reliable) Crop sensor digital cameras have dim viewfinders

and it is very difficult to achieve pin-point stars.

Try setting white balance to Tungsten. Auto white balance will make red cast from

light pollution. Set camera for long exposure noise

reduction. Use mirror lockup to eliminate mirror slap. Use cable release or self timer to avoid

vibration from touching the camera. Hat trick. Turn off in-camera sharpening, shoot RAW

mode.

billhuegerich@yahoo.comwww.pbase.com/billhuegerich