Transcript Slide 1
Review • Types of Telescopes • What you can expect to see through your scope. • Learning to use your telescope • Astrophotography • Observing Tips Aperture Aperture (diameter of the lens or mirror) is the single most important factor in choosing a telescope. The prime function of all telescopes is to collect light. The larger the aperture, the more light it collects and the brighter (and better) the image will be. Considering your budget and portability requirements, select a telescope with as large an aperture as possible. 5” 8” 14” Magnification • Mag = Focal Length of Main / Focal Length of Eyepiece • Example: A 50mm eyepiece on a Celestron C8 (2038mm fl) Mag = 2038/50 = 40.76, ~40 power Magnification is one of the LEAST important attributes of your scope! Magnification As a rule of thumb, the maximum usable power is about 50 times the aperture of the telescope in inches. Powers higher than this usually give you a dim, fuzzy, lower contrast image. For example, the maximum power on a 60mm telescope (2.4" aperture) is 120x. For a 6” telescope, it would be about 300 power Moon through C8 with 10mm eyepiece Moon through C8 with 50mm eyepiece Higher powers are mainly used for lunar, planetary, and binary star observations. Don’t believe manufacturers who advertise a 375 or 750 power telescope which is only 60mm in aperture, as this is false and misleading. Most of your observing will be done with lower powers 20x – 50x. With these lower powers, the images will be much brighter and crisper, providing more enjoyment and satisfaction with the wider fields of view. Mounts Must be stable Learning to Use Your Scope • Finding Objects is the most difficult and frustrating part of using a telescope. • Start with easy-to-find objects and move to more difficult as you grow more competent and confident. • Recommended order: Moon, Planets, DoubleStars, Bright Nebulae, Star Clusters, Galaxies • Galaxies are the most disappointing objects you’ll view through your scope (compared to photos). The Moon Prepare for an awesome spectacle. The moon's disk has a pastel-cream and gray background, streamers of material from impact craters stretch halfway across the lunar surface, river-like rilles wind for hundreds of miles, numerous mountain ranges and craters are available for inspection. At low or high power the moon is continually changing as it goes through its phases. Terminator = transition from light to dark Observing near the terminator shows the best views because of long shadows Full Moon is the worst time to observe - no shadows THE SUN It is quite safe to view the Sun if you use a proper solar filter. The Sun is fascinating to inspect as you detect and watch the ever-changing sunspot activity. If you are fortunate enough, and are willing to travel to remote locations, you may at some point experience a solar eclipse. Observing The Planets • Planets change! Some changes are observable in the course of a single evening. • Jupiter’s moons, cloudbands, and red spot will noticeably change in 3-4 hours. • Venus shows phases like the moon. • Mars approaches close to the Earth every two years. • Saturn tilts its rings over period of 29 years • Uranus and Netpune are difficult targets – but beautifully colored blue-green. The Planets Stars, Galaxies, and Nebulae • Stars appear brighter, but not larger – double stars can be split at magnification. • Large nebulae, like the Orion Nebula, are easy and beautiful targets. • Star clusters, like M13 (the Hercules Cluster) are wonderful subjects. • Galaxies are faint targets and require more skill to locate without a computerized mount. Typical views often disappoint. Stars, Galaxies, and Nebulae Learn The Sky • Astronomy is an outdoor nature endeavor. • Go out into the night and learn the constellations, star names, and patterns overhead. • Use monthly sky charts or planispheres to help. • Binoculars are a HUGE help. Always bring them when using a telescope. Observing Guides • Use available resources to learn the night sky and to find out what’s in the sky tonight. – “Sky and Telescope” or “Astronomy” Magazines – Books – Star Charts, Planispheres – Software • Plan your observing session before you go out to observe! Some Photos Nearly Full Moon Eclipsed Moon Comet 17p/Holmes 11/1/2007 5” f4 Venus Transit – 6/7/2004 Keep a Log Book • Get a spiral-bound notebook and keep it with the rest of your observing gear. • Keeping a record concentrates the mind — even if it's just a jotting like "November 7th — out with the 10x50 binocs — clear windy night — NGC 457 in Cassiopeia a faint glow next to two brighter stars." • Being able to look back on your early experiences and sightings in years to come gives deeper meaning to your activities now. Dress for Success • Dress warm! • Never underestimate the power of the cold. • A 50deg night may not sound too cold, but try standing out in it for a few hours. • Double socks, gloves, hat, thermal underwear, layers, layers, layers… • Camping and hunting stores are good sources for supplies.