Laboratory 7: Astrophotography Star Trails This lab is worth 3 course points. It is DUE on Monday. November 13. by 6:00 pm PST. via Gradescope. DON'T turn the lab in prior to the week of November 6. Star trails like the ones shown in class are easy to photograph. with the right kind of camera. Simply set your camera on a tripod (or. if you don't have a tripod. secure it to a rock. a fence post. etc.). Then point up. make the lens opening wide (that is. set it to a low fnumber. like f/'2.8). disable the ash unit. set the camera focus to innity. and open the shutter for some period of time (preferably with a cable release to minimize vibrations). Be careful not to shine lights near the camera while the shutter is open. Your camera must have the option of taking a long exposure (normally the \"bulb\" setting of cameras); an \"instamatic camera\" wont work. and even some automatic singlelensreex (SLR) cameras don't have this option. Your best bet is a manual SLR or manual digital SLR. The point of this lab is to obtain trailed photographs of the stars. This will (a) give you a sense of the rotation of the celestial sphere (i.e.. the rotation of the Earth). (b) allow you to photograph and learn some constellations. (c) appreciate the different colors of stars. and (d) perhaps catch some meteors (\"shooting stars\") on lm if youire lucky. You may point anywhere in the sky; if you want to choose some specic constellations. however. perhaps consult the star charts on the inside front and back covers of The Cosmos (Pasachoff 32: Filippenko). Take at least three photographs of the sky with ISO 100400 color print lm. or make a color print from a digital camera. (If using faster lm from a bright location. you should use a higher f number than f/QB. like f/4 or f/5.6. to cut 0th some of the light.) Use different exposure durations for each photograph. with a minimum duration of 1 minute. (Vi-Te want to see star trails due to the rotation of the Earth. so the exposures shouldn't be too short.) For example. from a bright site like Berkeley you could use 1. 2. and 4 minutes. Longer exposure times will give you longer star trails and will improve your chances of catching a meteor (or an airplane). but exposure times shouldn't be too long if your location suffers from light pollution. For best results in a bright location. point your camera toward bright stars. More pleasing photos can be obtained from a dark location. away from city lights: you can then use faster lm (e.g.. ISO 800) and longer exposure times (perhaps 5. 10. and 20 minutes). For more details on astrophotography. including digital cameras. see the tips on the next two pages. Be sure to write down the date. starting time. exposure duration. and sky conditions (clouds. moonlight. etc.) for each photo. Bring a notepad and a small ashlight for this purpose. (The ashlight will also allow you to examine your camera settings.) Turn in your three best photos having different exposure durations. and write a few sentences describing or interpreting what you recorded. You can talk about the star brightnesses. colors. patterns. etc. If you think you recorded an airplane. articial satellite. or meteor. discuss your reasoning. Also. please write down the location you chose from which to photograph the sky. You may photograph the sky with your friends. but each of you should turn in die'rent photographs and your own descriptions