Outdoor Setup Alignment and Checkout

The first priority on this first evening with the new telescope is finding a place to set it up, and the good old backyard is a natural. No, the skies probably are not dark, but this first time it is probably best to stick close to home, even if the sky is badly light polluted. You are going to spend as much time squinting at the instruction manual as squinting through the eyepiece, and it will be nice to be able to turn on a white light without incurring the wrath of fellow observers when there are problems— which there probably will be on this first run.

Where exactly should the scope be set up? That is easy. Take it to an open space with as clear a view of the sky as possible that is also as shielded as possible from ambient light sources. If the CAT is equipped with a German equatorial mount (GEM), try to find a location where Polaris is visible. As for ambient light, just do the best you can; the average suburban or urban backyard is illuminated by dozens of streetlights and porch lights. That is really not a problem this first evening, anyway. The goal the first time out is to make sure the scope is okay, not hunting dim deep sky objects.

R. Mollise, Choosing and Using a New CAT, 16

DOI: 10.1007/978-0-387-09772-5_7, © Springer Science + Business Media, LLC 2009

When should the Schmidt Cassegrain telescope (SCT) go outside? Get it out into the yard at least half an hour before dark to allow the optics to acclimate to outdoor temperatures. Normally, unless high-power views of the Moon and planets are on the evening's observing menu, cooldown is not a big deal. Deep sky objects look pretty good even in a nonacclimatized scope. One of tonight's tasks, however, will be to check the telescope's optical quality, and that does require it to be thoroughly "equilibrated" to outdoor conditions.

Maksutov Cassegrains tend to take longer than SCTs to cool off, especially in apertures larger than 6-inches, so "an hour or two"—or more—may be required for them to equilibrate. The reason for this difference is controversial, with some optical gurus asserting the thicker Mak corrector does not help speed along the cooldown time. The fact is that these telescopes do take longer to adjust, whether that is due to their "salad bowl" correctors or just because their longer focal length/higher magnification nature exaggerates the optical problems of a nonacclimatized scope. Longer cooldown times may also be required for SCTs larger than 8-inches or if the temperature differential is large between outdoors and indoors.

After a good spot has been found for the CAT, the next thing to do is assemble and level the tripod. There is no need to be obsessive. Getting the tripod precisely level will not, contrary to what some go-to users think, improve object-finding accuracy. Ensuring the scope is level is a help during alignment since the closer an alt-azimuth-mode scope is to level, the closer it will come to initial alignment stars. Celestron scopes are a little picky about tripod leveling when the SkyAlign procedure is used, but there is still no need to obsess. Get the thing reasonably level with a bubble level and move on.

When it is time to place CAT and mount on the tripod, follow the same procedure as when assembling it for the fake alignment, referencing the manual and the instructions in Chapter 5. As with the fake alignment, even if a fork-mount scope is to be used in equatorial mode on a wedge later, set it up in alt-azimuth mode tonight to simplify outdoor setup the first time. If the CAT's optical tube assembly is mounted on a GEM, point the right ascension axis of the mount north, using a compass if necessary (if Polaris is not visible), place the scope on the mount, and secure it according to the manual's instructions. In the Southern Hemisphere, a compass will be a necessity since the southern Pole Star is a dim magnitude 5.5. At this time, GEM users should skip ahead to the polar alignment section that comes just after the Tips for Happy Go-toing. When the mount is polar aligned, return to this section.

While waiting for the telescope to cool and darkness to arrive, install the accessories. If the finder was removed for storage, reattach it to the OTA. Remove the rear port's cap and thread on the visual back. Install the star diagonal and insert a low-power ocular into it. Some amateurs like to wait until darkness comes to screw on the visual back, diagonal, and eyepiece, leaving the rear cell uncapped until then to speed cooldown. But, you might want to wait a little longer for cooldown than try to figure out how to remove a mosquito from the OTA interior—something that has happened to amateur astronomers a time or two. Either attach the diagonal and eyepiece or leave the rear port capped to keep dust and critters out.

Connect the CAT's hand control and battery. Plug the HC into the proper port (be sure) and, after checking that the power switch is in the off position, connect the direct current (DC) power cable to scope and battery. If an AC adapter will be used to power the CAT, get set up with extension cords and power strips as needed. Do not use an

Plate 46. (Heater) Correctly positioning a dew heater strip behind the corrector assembly is important for good performance. Credit: Author.

extension cord any longer than absolutely necessary. The voltage drop incurred by a long cord run can make some computerized telescopes act "squirrelly."

With darkness falling, it is time to prepare the scope's dew-fighting tools. If the only antidew provision is a dew shield, set it aside until it is time to start observing. There is no point in exposing the corrector to dust and the depredations of birds until it is time to begin. Unless the backyard is large and open, the dew shield is probably all that will be needed to keep the corrector dry. Trees and houses ringing the scope tend to act as a natural dew shield, blocking portions of heat-sucking sky from the scope's view. If another dew-busting apparatus will be needed, go ahead and drag it out. Connect a dew zapper gun to its battery and place it somewhere where it will be handy. If a corrector plate heater system has been purchased, install it. Some SCT users wrap the heater strip over the corrector assembly at the end of the tube, but some of the best results come by wrapping it around the tube itself, just behind the corrector assembly (Plate 46). Where does the dew heater control box go? You can attach it to a tripod leg with Velcro.

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