How Do I Prepare for High Resolution

Like real estate, the old adage of "location, location, location" rings true for obtaining the highest resolution CCD images. Some areas are simply better than others. Mountaintops in the desert areas of the Southwest United States, Southern Africa and South America have the highest number of nights of very dark, sub-2-arcsecond seeing. Most of us have to accept what lies overhead, whether it is turbulence from the Rockies or the air-mixing effects of powerful jet streams. These atmospheric phenomena are part of the macro-seeing environment, and they are totally outside our control. Surprisingly, though, we can significantly control the "local" or micro seeing environment for imaging, but we understand that everything conspires against us working at sub-arcsecond/pixel image scales!

Here are a few lessons based on my experience:

Rooftops: Homes heat up during the day and take a long time to cool down, especially with roofs made of ceramic tile or asphalt shingles and where the structure is brick or stucco. Do not select a target downwind of your home unless you have allowed adequate time for cool-down. My observatory is about 70 feet from my house, and it is not practical to image until about 3 hours after sundown if my target is downwind of the house.

Chimneys: Streams of chimney exhaust travel surprisingly long distances. This meandering stream can cause the loss of guide-stars and create large variations in your star sizes if it crosses over the area imaged by your telescope. A few very prominent imagers have confessed to turning off their furnaces at night, even in the dead of winter, while imaging. Tip: for family unity put up a reminder to turn it back on when you've finished!

Figure 8.3. Galaxy M106. L(Ha/R)GB image of 150:50:50:70 minutes total exposures, respectively (3-minute individual exposures) using a non-IR-blocked luminance image and Custom Scientific RGB filters. A separate 90-minute Ha image (5-min. individual exposures) was combined 50/50 with the R frame to better highlight the galactic jets. Image calibration and color combination using MAXIM DL (RC Console for sigma combine and pixel cleanup within Maxim DL), image registration using Registar, Ron Wodaski's gradient removal, AIP for Lucy Richardson deconvolution on the luminance, luminance layering in Photoshop for final color and star shaping processing. Equipment: RCOS 20-inch f/8 RC and Finger Lakes IMG6303E CCD camera with all images acquired in 2 x 2 bin mode for an image scale of .92 arcsecond/pixel in 3 arcsecond seeing and magnitude 4.9 suburban/rural skies.

Figure 8.4. Brian Lula with his 20-inch Ritchey-Chretien (RC) telescope and home-built heavy-duty equatorial fork mount. This telescope replaced a personally built 20-inch F/5 Newtonian astrograph used to take some of the deep-sky images in this chapter. Note the silver wrap on the telescope pier. The pier produced considerable thermals during the night, seriously affecting local seeing. An inch-thick layer of rigid Styrofoam glued all around the pier and further wrapped by aluminized polyethylene bubble wrap improved seeing conditions considerably.

Figure 8.4. Brian Lula with his 20-inch Ritchey-Chretien (RC) telescope and home-built heavy-duty equatorial fork mount. This telescope replaced a personally built 20-inch F/5 Newtonian astrograph used to take some of the deep-sky images in this chapter. Note the silver wrap on the telescope pier. The pier produced considerable thermals during the night, seriously affecting local seeing. An inch-thick layer of rigid Styrofoam glued all around the pier and further wrapped by aluminized polyethylene bubble wrap improved seeing conditions considerably.

Asphalt parking lots and driveways: These are also strong heat absorbers that will continue heating up air long after sunset. Avoid imaging downstream or on top of these areas until they have adequately cooled down. Large grassy areas are optimum.

Home observatories: Modern professional observatories are especially designed to alleviate local seeing effects produced by the telescope enclosure. Not surprisingly, the same applies to our personal observatories for high-resolution work. Open up domes or roll off roof observatories well before sundown to give them plenty of time to cool down. Even better is to pull air into your observatory with fans. Avoid cinder block or brick walls and concrete floors: They will absorb significant amounts of heat during the day and expel it for long periods during the night. Insulate large concrete or steel piers that support the telescope. I use a rigid styrofoam insulation board to insulate the concrete pier and further wrap it with aluminized "bubble wrap" to protect it (see Figure 8.4).

We can spend considerable effort and money managing the thermal behaviors of our telescopes with fan cooling and zero expansion optical/structural materials. However, overall imaging performance can be as much affected by local seeing phenomena as by our scope performance.

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