(thanks to the generosity of the Tri-Valley Stargazers!)

With the nice climate of California, due to the high pressure center off of the coast that dominates the prevailing flow for most of the year, and access to Hidden Hill Observatory (a reasonably dark observing site in the San Francisco Bay area with access being a benefit of  membership in the Tri-Valley Stargazers (TVS)), I've been doing various forms of astrophotography since 1992. My main interest is photographing emission and reflection nebula, although I have also photographed galaxies. With my recent acquisition of  a Coronado SM-60 Hydrogen alpha (H-alpha) filter, solar observing has become part of my schedule, and my sleep deprivation has increased!

This hobby requires lots of patience as the exposure times for deep-sky objects range from about 1 hour to 3 hours!. All the while one must keep a guide star centered on the illuminated crosshair of a high power eyepiece by manually entering corrections to the motor drive, which tracks the stars as they move across the sky due to the Earth's rotation. I followed this procedure for many years as I honed my skills, but eventually freezing my tail off while hovering over the eyepiece on long winter nights lost its appeal. With the purchase of a Santa Barbara Instrument Group (SBIG) ST-4 autoguider, the quality of my photographs has improved due to more accurate guiding. This is a charged coupled device (CCD) that automatically makes guide corrections on a guide star of my choice. The added benefit is that I'm able to take a cat-nap in my truck while the ST-4 does the tedious work, and this makes for a much less risky drive down the mountain in the morning.

In 1994, my first concerted effort at deep-sky consisted of piggyback photography. I mounted my 35mm camera with a 50mm or 90-230mm telephoto lenses attached onto the top of my Meade Schmidt-Cassegrain telescope. Sweeping vistas of the night sky are possible with this configuration including wide-field views of the Milky Way. With the 50mm lens one can capture a field of view (FOV) of about 28 degrees on film, while with the telephoto set at 230mm, about 8.75 degrees of sky is visible. With the telephoto lens and color film one can obtain photos with a reasonable image scale of the North American Nebula (NGC7000), the Orion Nebula (M42), the Andromeda Galaxy (M31), or even comets. Others, such as Chuck Vaughan, have used high-end telephoto lenses with hypered Kodak Tech Pan b/w film and a nightime Hydrogen alpha filter (beware, not the type used for solar observing or solar astrophotography!!!) to obtain extremely rich photos of nebulosity and star fields. Piggyback astrophotography is also great for capturing meteor trails. This is the simplest form of guided astrophotography, and due to the difference in magnification between the camera and the guiding telescope, errors in guide corrections have a minimal impact, provided you have good polar alignment. For example, during 1997 I was taking a piggyback photo of Comet Hale-Bopp during very windy conditions. As a result the comet nucleus jumped about the field of view, well outside the crosshairs of the guiding eyepiece (since the comet moves relative to the stars I guided on the nucleus). I thought the photo would be trash, but to my great surprise it came out fantastically (at least from a guiding point of view).

My initial foray with piggyback astrophotography gave me the time to develop two crucial skills for obtaining successful astrophotos, (1) accurate polar alignment: the better your polar alignment, the fewer guide corrections you have to enter, and (2) experience entering guide corrections. With the favorable image to guide ratio (discussed above) you to can successfully photograph the beauty of the night sky with a little practice. With encouraging results, the next logical step is prime focus astrophotography in which the optics of the telescope are used in place of the camera lens. In this case I attached my 35mm camera body to a Lumicon Giant Easy Guider on my Meade 10" f/10 Schmidt-Cassegrain telescope. The easy guider contains a focal reducing lens that gives a larger field of view (~1 degree of sky) and a faster focal ratio (~f/6.3). Since the exposure time goes as the square of the focal ratio, the focal reduction cuts the necessary exposure time drastically. For example, at f/6.3, a good beginning exposure time would be about 40 minutes. The same photo at f/10 would take 100 minutes to achieve the same color saturation and brightness as the f/6.3 photo (assuming reciprocity failure of the film remains unchanged). With the easy guider, the guiding eyepiece is located in front of the focal reducing lens, thus guiding is performed at f/10 while the photo is taken at f/6.3. Thus, the added magnification of the guiding eyepiece gives a better chance of obtaining an accurately guided photo, provided your guiding technique is up to snuff. Using a light pollution filter, such as the Lumicon Deep-Sky filter or the IDAS LP-1, enables one to take exposures up to 3 times longer. These filters are most useful for photos emission nebula, but depending on the film used a color shift may result. Numerous articles in astronomy magazines compare results using different films and filters. I have used this configuration to photograph emission and reflection nebula, planetary nebula, galaxies, and the moon.

After years of astrophotography using my Schmidt-Cassegrain, I longed for widefield photos of the Veil Nebula (NGC 6992, 6995, 6960 are the brighest portions; 6974, 6969, and Pickering's Triangular Wisp are more elusive). To me, the Veil Nebula has almost become an obsession, both visually and photographically. To obtain these images, I acquired a 4" Takahashi refractor. The Veil Nebula is the result of a shockwave from a 30-40,000 year old supernova remnant that is impacting dense regions. This causes the gas to fluoresce, giving rise to regions of lacey beauty that in my opinion are unrivaled in the Northern Hemisphere. From my observing site an Oxygen III filter (I own the Lumicon OIII filter) provides the necessary contrast for visual observations. The OIII filter isolates the two doubly ionized lines of oxygen at 496 and 501 nanonmeters that dominate the emission of planetary nebula. It suppresses starlight and light pollution that compromise the sharp contrast that is necessary to observe these phenomena. As I became more experienced over the years, I no longer needed the OIII filter to see the brightest portions of the Veil Nebula. However, using the OIII filter has always improved the views I have had. The OIII filter is not used in photographic applications.

Recently, I have been using a Phillips ToUcam Pro (your typical "watch the coffee pot" webcam) for digital imaging. This was inspired by the presentation of Gert Gottschalk and Sibylle Frohlich at the April 2003 TVS meeting. They showed fantastic solar, lunar, and planetary images made using a ToUcam, and with the impending Mars opposition in August 2003, I decided then and there that I had to try my hand at it. I thank Gert and other TVS members for helpful hints on set-up and image processing.

Astrophotography Equipment:

Telescopes:
1) Meade 10" f/10 LX-200 Schmidt-Cassegrain telescope equipped with a Lumicon Giant Easy Guider to reduce the focal ratio to ~f/6.3 (FOV ~1 degree).

2) Takahashi FS-102 4" f/8 refractor
    I use this telescope in the standard f/8 configuration (FOV ~2.8 degrees) and with an f/6 focal reducer for wider field astrophotos (FOV ~3.25 degrees).

3) Meade 8" f/6 Newtonian reflector (used mainly for solar photography with a Thousand Oaks white light filter, see below).

4) TeleVue Pronto 70mm f/6.8 refractor

Mounts (see pictures above):

AP1200 and AP900 GOTO Mounts: Eventually, I will put a 12.5" Optical Guidance Systems Ritchey-Chretien on the AP1200. In the mean time I will use these mounts with the Takahashi
Losmandy G-11: this is the mount for the Takahashi and Pronto refractors

Filters:

1) Astrodon LRGBCHa for color imaging with my SBIG ST-2000XM

2) Astronomik IR-Block filter for planetary and lunar ToUcam CCD imaging

3) Lumicon Deep-Sky and IDAS LP-1 light pollution filters for film photography of emission nebula

3) Coronado SM-60 Hydrogen alpha filter for solar astrophotography/imaging. This filter has a bandpass of <0.7 angstroms centered at 6562.8 angstroms and is used to visualize sunspots, faculae, filaments, flares, prominences, and coronal mass ejections. With the included T-Max tuner, the interference filter can be manually tilted to detune the filter to shift the central pass band to better visualize doppler shifted features such as flares and coronal mass ejections

4) Thousand Oaks broadband solar filter

All photos are copyright K. R. Sperber