Telescope Observing

Telescope Observing and Sketching


1. An Activity Sheet, Clipboard, and Pencil

This sheet for each member of the audience provides space for them to draw their versions of Mars, and for their extraterrestrial creatures. You can devise your own sheet or use ours. We also provide a clipboard with attached pencil for each participant.

2. A Naked-eye Mars Projector

This is needed for the first activity. The starlike image of Mars must be moveable and similar in diameter and hue to the other red stars in the planetarium sky. Many planetarium projectors already include a good Mars projector that can be adjusted by hand. However, if your projector, like ours, produces planets much greater in diameter than the stars, you can use a single slide projector instead for Mars. We use a simple black Kodalith slide with a small orange dot which projects a star similar to the first magnitude stars in the planetarium sky. The single slide projector is moved by hand to produce the two or three relative motions that occur (during the “days”) in the program. You’ll need to make your own “dot” slide.

3. Battery-operated light pointers

These are available from photography stores. It’s good to have at least two of these: one bright and one dim. The easiest way to dim a pointer is to replace one of the batteries with a “dummy” battery consisting of a block of wood, plastic, or metal which has about the same dimensions as a battery, but that provides a short-circuit electrically through the length of the block. With the “dummy” battery installed, the bulb gets current supplied by only one battery, which makes it just the right brightness for pointing out stars and saves battery and bulb life to boot.

It’s also possible to make an inexpensive light pointer out of LED flashlight See the Constellations Tonight News and Updates on the PASS website for details.

4. Reading lights for the students

In our permanent planetarium, we have 7-watt night-light orange bulbs under the cove, with shades so they shine down on the audience. This is very convenient, because visitors can draw on their activity sheets and look back up at the sky easily. The program can also be done by turning up the daylight for people to study their charts, and then turning it down for sky examination. In our portable inflatable planetarium, we use 7-watt night-light orange bulbs in clip-on lamps, mounted to shine down on the audience for reading and drawing.

5. (Optional) An Opaque Projector

This allows participants to have their own drawings projected onto the dome for discussion. We use an inexpensive opaque projector (a “Brumberger #290 Project-0-Scope” or a “Rainbow Crafts M100”), sold in art supply stores. This produces quite an adequate image two feet in diameter in our dome. Better projectors are available at higher cost.

Presenter's Script

Turn up daylight, distribute paper, turn on reading lights full.

Here is your chance to pretend you are an astronomer, trying to help decide what the surface features are. Let me give each of you a piece of paper. On the top half there are two sketches of your telescope eyepiece, with a blank disk of Mars ready for you to complete. Now, to help determine what surface features are there, please sketch in the dark features on the surface of Mars. Watch for the brief moments of clarity, and then get as much detail as you can. We will observe for just a few minutes, and then hold a brief conference to reach our joint conclusions. There is a second blank disk on your paper in case you don’t like the way your drawing is coming out, and want to start over.

Turn off daylight. Go through three periods of clarity, then turn up daylight and turn off Mars’ special effect.

Please recall the telescope photograph of Mars that you saw a few minutes ago.

Which contains more details, your drawings or that photograph?

Any one of your drawings has more detail than that photograph which was one of the best ever taken from the planet Earth.

Compare your sketch with the person sitting next to you. Did they see some details you didn’t?

Walk around the room, select one or two examples and show using the opaque projector. These sketches are all different, although some of the features show up on most of them. Ask students to name the features on the projected image that are similar to the features on their own drawing.

Why do you think each of us made a different sketch of the same view? [Differing skills of observers, different moments of observation, different choices of what to watch.]

There are always differing interpretations of what is really there for something as new and difficult to observe as this. We cannot agree perfectly on what is really there, but we can come to agreements on broad structure. Even with all the inherent limitations of drawings, many of the best and most detailed images of Mars have come from drawings by amateur and professional astronomers, not from photographs.


(movie: Show the series of comparison images from the Optical Data Corporation’s “Astronomy” laser videodisc or slides, showing first a telescope photograph of Mars at a given time, then a corresponding astronomer’s drawing of the same side of Mars created at the same time as the photograph.