5. Lab telescope (8 inch Dobsonian-mounted reflector)
6. Eyepiece bag (should contain 3 eyepieces and one filter)
Optional - binoculars, coffee
Objective: The objective of this lab exercise is to view several different objects and types of objects using a medium sized telescope. While many of the brighter objects in the sky (including planets) can be viewed using a smaller telescope, the "faint fuzzy's" usually require more aperture to resolve enough detail to keep it interesting. This will be an exercise in Deep Sky observing.
Chose your objects: Before you go out, determine what objects you want to try to find. You should choose at least one from each category: globular clusters, open clusters, nebulae (emission or planetary), and galaxies. Some students can find these objects easily, so they may want to view more objects. Some suggested Fall objects are listed below. Most of these are identified by their Messier, or "M" number. Charles Messier was a French comet hunter. He assembled a catalog of objects that he thought might be confused with comets. Today, his catalog is used because it is a list of many of the brighter, and more interesting objects that can be seen with a small telescope. Some objects are identified by their listing in the New General Catalog, by their NGC number. You will need a field guild, or detailed star chart to locate your objects. You will be finding them by "star hopping". You need to become familiar with the brighter stars in the area of these objects and make plans as to how you will "triangulate" to find your objects. Some objects have very clear "pointer stars", while other objects are "out in the middle of nowhere" and therefore much harder to find.
Suggested objects for Fall viewing objects:
Globular Clusters: M13 (Hercules), M22, M4,
Open Clusters: M7 (wild duck), M11, NGC 884-869 (double cluster),
Find a Dark Site: A dark location will help your deep sky observations even more than telescope aperture. This means get out of town! This also means NO MOON!
Adapt to the Conditions - Once there, both your eyes and the telescope will have to adjust to the conditions. Your eyes will need at least 20 minutes to become dark adapted. Longer is better. To help you maintain your night vision, only use a red flashlight if you need one for writing. You will be surprised at how much you can see without a flashlight if your eyes are truly dark-adapted. In addition to your eyes having to adjust to the dark, the telescope will probably need to adjust to the cooler outside temperature. As the mirror cools, thermal currents inside the telescope tube will make the image unstable. It often takes an hour or more for an 8" telescope to fully cool. Fortunately, the image at low powers stabilizes much quicker than that, so you should be able to start observing as soon as your eyes are "ready." Note that you should expect your images through the telescope to improve during your observing session.
Align your telrad and/or finder scope: You should be familiar with this procedure from the in-class exercises. If your finders are not aligned, you will only find anything with lots of luck. However, if they are aligned properly, skill and practice will let you find anything.
Find your objects: One by one, locate the objects you chose to find. This will take patience and practice. Always use the lowest power eyepiece to find the objects, because that will give you the widest field of view. Many of these objects are visible in binoculars, especially if the binoculars can be mounted on a tripod for stability. Be aware that some of the objects, especially the planetary nebula might be very small in the low power eyepieces. However, they will not be pinpoints, as are the stars. Sometimes you may have found your object if one of the "stars" in the field looks slightly out of focus. Change to a higher power eyepiece to see if this is correct. If you have problems finding the objects, take turns doing a regular sweep of the sky near where you think the object should be.
Observe your objects: Spend at least 10 minutes observing each object. Try different eyepieces to see which one gives you the best view. Using a pencil, sketch what you see with the eyepiece that gives the best view. Note that what you see (and therefore your sketch) will NOT look like the photos in a field guild. Be sure all your sketches are to scale. The circles represent your field of view. Sketch a negative image using a pencil. Dark marks represent bright areas. Take turns finding the objects. Not everyone will be able to find all the objects easily, but it is important for everyone to get a chance. Describe in words what you see through the eyepiece.
Use averted vision - Don't look directly at the object. Glance to the side in your field of view. Often faint images show up better in the periphery of the eye's retina.
Jiggle the Telescope - The eye is very sensitive to motion and can often see moving objects more readily. Tapping the scope will often show you where an object is if you think it is in the field of view, but can't quite see it. Jiggle gently!
Relax your other eye - Try not to squint. Gently covering your non-viewing eye with a hand will keep your face muscles relaxed so you can concentrate on observing.
Report: Your report should consist of one page describing when and where you observed and what objects you looked for. Include any operational details about field guild use, telrad alignment, dew, meteors, etc. that might be important. Briefly describe the overall experience. Then discuss the objects you viewed. Use a separate page for each object. You can print our multiple copies of the following page to use in your report. On each page, include:
a sketch of the star field you used to find your object.
a description of your "star pointers'.
your sketch of the object as seen through the eyepiece.
a brief description of what you see through the eyepiece.
Object _____________________________ Eyepiece that gives the best view _______________________
Sketch the star field you used to find your object.