published monthly in Astronomy, Sky & Telescope, or other astronomy magazines to locate them. Venus, Mars, Jupiter, and Saturn are the brightest objects in the sky after the Sun and the Moon. Not all four of these planets are normally visi- ble at any one time.
JUPITER The largest planet, Jupiter, is a great subject to observe. You can see the disk of the giant planet and watch the ever-changing positions of its four largest moons, Io, Callisto, Europa, and Ganymede. If atmospheric conditions are good, you may be able to resolve thin cloud bands on the planet’s disk.
SATURN The ringed planet is a breathtaking sight when it is well positioned. The tilt angle of the rings varies over a period of many years; sometimes they are seen edge-on, while at other times they are broadside and look like giant “ears” on each side of Saturn’s disk. A steady atmosphere (good see- ing) is necessary for a good view. You may probably see a tiny, bright “star” close by; that’s Saturn’s brightest moon, Titan.
VENUS At its brightest, Venus is the most luminous object in the sky, excluding the Sun and the Moon. It is so bright that sometimes it is visible to the naked eye during full daylight! Ironically, Venus appears as a thin crescent, not a full disk, when at its peak brightness. Because it is so close to the Sun, it never wanders too far from the morning or evening horizon. No surface markings can be seen on Venus, which is always shrouded in dense clouds.
MARS If atmospheric conditions are good, you may be able to see some subtle surface detail on the Red Planet, possibly even the polar ice cap. Mars makes a close approach to Earth every two years; during those approaches its disk is larger and thus more favorable for viewing.
Stars
Stars will appear like twinkling points of light in the telescope. Even powerful telescopes cannot magnify stars to appear as more than points of light! You can, however, enjoy the differ- ent colors of the stars and locate many pretty double and multiple stars. The famous “Double-Double” in the constella- tion Lyra and the gorgeous two-color double star Albireo in Cygnus are favorites. Defocusing the image of a star slightly can help bring out its color.
Deep-Sky Objects
Under dark skies, you can observe a wealth of fascinating deep-sky objects, including gaseous nebulas, open and globu- lar star clusters, and different types of galaxies. Most deep-sky objects are very faint, so it is important that you find an observ- ing site well away from light pollution. Take plenty of time to let your eyes adjust to the darkness. Don’t expect these subjects to appear like the photographs you see in books and maga- zines; most will look like dim gray smudges. (Our eyes are not sensitive enough to see color in such faint objects.) But as you become more experienced and your observing skills get sharper, you will be able to discern more subtle details.
Remember that the higher the magnification you use, the dim- mer the image will appear. So stick with low power when observing deep-sky objects, because they’re already very faint.
Consult a star atlas or observing guide for information on find- ing and identifying deep-sky objects. A good source to start with is the Orion DeepMap 600 (part #4150).
7. Astrophotography
There are several different types of astrophotography that can be successfully attempted with the Skywatcher 90:
Moon Photography
This is perhaps the simplest form of astrophotography, as no motor drive is required. All that is needed is a Universal 1.25" Camera Adapter (part #5264) and a t-ring for your specific camera. Connect the t-ring to your camera body, and then connect the nosepiece of the camera adapter to the t-ring (the body of the camera adapter is not needed). Insert the camera, with the camera adapter attached, directly into the telescope’s focuser drawtube (remove the star diagonal), and secure firm- ly with the setscrew on the drawtube. Make sure the setscrew is tight, or your camera may fall to the ground!
Now you’re ready to shoot. Point the telescope toward the Moon, and center it within the camera’s viewfinder. Focus the image with the telescope’s focuser. Try several exposure times, all less than 1 second, depending on the phase of the Moon and the ISO (film speed) of the film being used. A remote shutter release is recommended (part #5232), since touching the camera’s shutter release can vibrate the camera enough to ruin the exposure.
This method of taking pictures is the same method with which a daytime, terrestrial photograph could be taken through the Skywatcher 90.
Planetary Photography
Once you’ve mastered basic Moon photography, you’re ready to get images of the planets. This type of astrophotography also may be used to capture highly magnified shots of the Moon. In addition to the adapters already mentioned, the sin- gle-axis motor drive is also required. This is because a longer exposure is necessary, which would cause the image to blur if no motor drive were used for tracking. The equatorial mount must be precisely polar aligned, too.
As before, connect the t-ring to your camera. Before connecting the camera adapter to the t-ring, an eyepiece must now be inserted and locked into the body of the camera adapter. Start by using a medium-low power eyepiece (about 25mm); you can increase the magnification later by using a higher-power eye- piece. Then connect the entire camera adapter, with eyepiece inside, to the t-ring. Insert the whole system into the telescope’s focuser drawtube and secure firmly with the setscrew.
Aim the telescope at the planet (or Moon) you wish to shoot. The image will be highly magnified, so you may need to use the finder scope to center it within the camera’s viewfinder. Turn the motor drive on. Adjust the telescope’s focuser so that the image appears sharp. The camera’s shutter is now ready to be opened. A remote shutter release must be used or the image will be blurred beyond recognition! Try exposure times between 1 and 10 seconds, depending on the brightness of
