Solar Observing

This summary of how to operate the York wide-field telescope, located in the 40cm (east) dome, is written for the Solar observer. Remember, when observing the Sun,

NEVER LOOK DIRECTLY AT THE SUN THROUGH ANY OF THE TELESCOPES.

NEVER UNCAP THE 40 CM TELESCOPE.

If you encounter a serious problem while operating the telescope, shut the power off to the telescope and camera, close the dome and leave a written message with the Undergraduate Secretary (from whom you likely obtained the observatory key). Also send an email reporting the problem as explicitly as possible to ouvarova@yorku.ca. In case of emergency, please contact Ms. T. Ouvarova at 416-999-4769 (mobile) or at 416-650-3570 (home).

Access to the Dome

To gain access to the 40cm dome, you will require a key. Keys will only be provided to authorized students registered in the class. The key may normally be picked up from Ms. Lauren O'Brien in the Physics and Astronomy Department office in 128 Petrie between 10:00 am and 4:30 pm Monday through Friday. (Note that the office is normally closed between 1pm and 2pm daily, so if you wish to observe during this period, sign out the key before noon.) You will be asked to leave your student card with one of the secretaries in the office while you are in possession of the key. The secretary will also keep a record of your visit and will not issue a key to you if inclement weather exists or the telescope is unavailable. Weekend observing is neither necessary nor permitted. Please note that the above times may vary somewhat due to operation considerations: be patient and attentive to the opening and closing times of the Departmental Office..

Getting Started

As you enter the dome, to your right is a dimmer switch that controls the intensity level of the incandescent lights. During Solar observing, these lights can be left at a low level (when the dome is closed) so you can safely negotiate the stairs. To prevent the possibility of damage to equipment, NO FOOD OR DRINK IS PERMITTED ON THE OBSERVING PLATFORM.

After reaching the platform, you need to open the dome slit. The slit assembly consists of two parts, the shutter (the bulk of the slit) and a wind screen at the bottom. Unless the Sun is particularly low in the sky and would be blocked by the wind screen, it is recommended that the wind screen be detached from the shutter. The mechanism that controls the mating of the pieces is located on the right (west) side of the slit. It is manipulated with a rope. The shutter will separate from the wind screen if the rope is held down while the shutter is being raised (which is why you should observe with a partner if at all possible). The shutter is raised using the southern-most switch on the base of the telescope pier. Dome rotation is controlled by the other switch on the base of the telescope pier. Both switches are well labeled.

In order to raise or lower the shutter, it must be facing south. The shutter will not have power if it is not facing south. If nothing happens when you turn the control switch, check the dome position.

The wide-field telescope is the white refracting telescope mounted on top of the 40cm telescope. The wide-field telescope is pointed at a source in the sky by moving the 40cm telescope, whose operation is described below.

Next turn on the video camera monitor and plug the video camera into one of the outlets on the telescope pier if it is not already.

Pointing the Wide-Field Telescope

There are two ways to move to an object on the sky using the 40cm telescope. The first method, used for night-time observing, is to use the computer database of the 40cm telescope. The simpler way, for large, bright objects like the Sun, is to use the manual north, south, east and west controls of the 40cm telescope hand paddle controller shown below.

40cm Telescope Hand Paddle

Turn on the power to the 40cm telescope which is controlled by the white switch on the west side of the pier. A red light should come on. (Do not touch any other switches on the 40cm telescope!) The figure above shows the controls needed to point the telescope at the Sun. There are the north, south, east west controls (labelled N, S, E, W, respectively) and four speeds for moving the telescope which are the four left-most buttons on the hand paddle. Use the first two speeds (32X and 16X) to maneuver the Sun on the monitor, and the slower motion controls (8X and 2X) to centre accurately.

The process for centring the Sun is as follows. Move the dome so that the Sun is centred in the slit. MAKE SURE THAT THE 40CM TELESCOPE IS CAPPED-- IF IT ISN'T IT MAY BE DAMAGED ONCE POINTED AT THE SUN. Use the fast motion controls (32X and 16X) to point the telescope in the vicinity of the Sun. Now put your hand or a sheet of paper about 40 cm behind the finder scope. (The finder scope is the small telescope located to the left of the wide-field telescope). A good rule to follow is that solar observations can be taken if you can see distinct shadows outside. On partly cloudy days, patience is required. Adjust the position of the telescope to make the shadow of the finder scope as small as possible. The Sun should then appear on the monitor. Now reduce the slew speed to place the Sun into the center of the monitor. This may take some practise and for your first visit may take a few minutes. The entire Sun should be visible as a bright round object on the monitor. The telescope should be nearly in focus already, but you may have to adjust the focus using the focus knob/wheel slightly depending on the circumstances. If you do not see any sunspots, check the focus of the telescope.

With the Sun now centred, the telescope will track the Sun fairly accurately. Place your overhead transparency on the monitor's screen using some masking tape and sketch all sunspots observed. (Be sure to trace carefully the outline of the larger spots and to be as accurate as possible in general.) If you are in doubt whether an object is a dust speck or a sunspot, just move the telescope a small amount. Real sunspots will move with the Sun. Once all your spots are sketched, you need to record the north, south, east and west directions on the sketch, as well as the local (standard) time of your observation. These last steps are essential, otherwise these data are useless!

To figure out directions, first make sure you have the hand controller on 8X speed. Now move the telescope a little north. The image of the Sun on the monitor, and any sunspots, will move in a direction which is towards the south because the telescope is moving towards the north. Repeat the procedure with the east button to identify west. You MUST determine and label the cardinal directions EACH time you observe. (Another useful tip is to trail the Sun in a given direction and watch where it last touches the circle. This point will be the direction opposite to the motion selected. For example, if you slewed the Sun to the east, then the point where the Sun last touched the circle is due west.) After you leave the dome, photocopy your observations then clean the transparency for repeat use next time you are observing.

Shutting Down

Now that you are a proficient telescope operator, closing the telescope will seem simple. Replace the dust covers and move the telescope so that it is facing approximately south and is horizontal. The exact position does not matter. Turn off the monitor and the power to the 40cm telescope and turn off the video camera. Rotate the dome so that the slit faces south and then close the shutter entirely. When the shutter is closed all the way, release the rope to clamp it to the wind screen. Be sure to lock up when leaving. RETURN THE KEYS TO THE PHYSICS AND ASTRONOMY OFFICE, PETRIE 128, WHEN YOU LEAVE.

Check List Summary for Solar Observing

Pick up the keys from the Physics and Astronomy Department Office, room 128 Petrie building. You will also have to "sign in" at the office.
Enter the observatory dome (40 cm telescope) and switch on the lights (dimmer switch is on the wall to the right of the door).
On the platform, open the shutter completely (south switch, east side of pier).
Rotate the dome so the Sun can be seen through the dome slit (north switch, east side of pier).
Power up the telescope (white switch, west side of pier).
Power up video camera (toggle switch on box on telescope base).
Power up video monitor on bench.
Remove plastic drop sheet (carefully) from telescope if necessary.
Using the hand paddle, point the telescope at the Sun using "shadow method"
NB. NO dust covers are to be removed. Minimize the telescope shadow to locate the Sun. NEVER look directly at the Sun with anything except the video camera on the solar-filtered telescope.
Ensure the Sun is in focus using the focus knob/wheel on the refractor. Check that the limb of the Sun is as sharp as possible.
Lightly tape the supplied transparency on the monitor and record the Sunspots, etc.
When the observations are complete, park the telescope, return the plastic drop sheet to cover the telescope, power down all systems, close the dome, turn out the lights, return the keys to the office (Petrie 128).