How to Use the Peyton Hall Telescope

Congratulations; you will be using Peyton Hall's telescope!

First, a word about the telescope, since interested people sometimes ask. The telescope is a 12" Schmidt-Cassegrain reflector by Meade, which is a high-end amateur telescope. You can buy similar telescopes for about $7000, and they all come with electronic controllers such as this one these days, which since they became possible just a decade or so ago have revolutionized amateur astronomy. If people are interested in taking up amateur astronomy as a hobby, they should be aware that binoculars are probably the way to go until they are serious, and then they could invest in a small telescope from Meade or Celestron. Other web pages describe a recommended route to amateur astronomy in more detail.

Basic Setup

It is helpful before you stqrt to have a computer with a web browser opened to the peyton hall observing reference page.

Open the dome shutter: Use the crank located along the rim of the dome.
Rotate the dome: You'll be rotating the dome with the dome controls. There are two buttons which rotate the dome in each of two possible directions...but the right-hand button moves the dome to the left, and vice versa. Beware, the switch that turns on a mysterious red light doesn't actually have anything to do with the dome controls.
Turn on the telescope: Use the on/off switch located to the upper right in the panel. This automatically turns on tracking as well as the computer (hereafter controller) that we will be using to point at objects. Don't touch the N/S switch: keep it on N, which indicates that we're in the northern hemisphere. There is a little bar graph which measures current to the system; it should go to about half full scale.
Remove the lens caps: You'll want to remove the "lens" caps of both the telescope and the finder. There should also be lens caps for the eyepiece ends, but they have long since disappeared; there is a plastic bag over the main telescope eyepiece which needs to be removed and put someplace where it can be found..

How to Operate the Telescope

Now take a look at the controller. This is what you'll be using to point at objects. In the following discussion note the difference between PRESSing a button briefly and HOLDing it down for about a second - when you hold a button usually it beeps to let you know you've held it successfully.

The telescope is on an equatorial mount, which means that the plate that it's mounted on has a normal vector permanently pointed at the north pole. Thus, to track an object, the telescope can rotate at the rate of one revolution per sidereal day in the ra degree of freedom while keeping the dec degree of freedom fixed. That means that in order to align the telescope (i.e. provide an absolute reference point) you only need to tell it where one star is. Also, the telescope needs to know what the sidereal time is, so let's start with that.

you should check to see if the local time and date are correct, and fix it if not. Read on.

Changing the Mode

Feel free to press MODE repeatedly. You will cycle through about 4 or 5 modes, such as the following (one mode, not pictured, is a complete shut-off of all light, so don't be fooled when you get to that mode).

Telescope/Object library control various settings, such as the location (i.e., Princeton's coordinates). Consult the manual for more info.

This screen tells you the coordinates you're pointed at (but these are nonsense if you haven't aligned yet, of course).

This screen tells you the local and sidereal time.

This is information about the local power line frequency, which the controller uses to run its drives and clocks.

Setting the Date and Time

To set the time and date, press MODE until you see the local time, then hold ENTER. Press numbers to set the time. W and E go forward and back if you make a mistake. Press ENTER when done and enter hours from GMT (remember, 5 in winter, 4 in summer); then press ENTER again. The local time is set. Now press ENTER to get to the date display, and similarly hold ENTER to set it. Once you've set the local time and date the sidereal time should take care of itself and be correct; you can check it with a sidereal time clock.

Aligning the Telescope

Choose a Bright Star

Setting the time is the hardest part. Now comes the fun part: finding a bright star to align on. You need to find a bright star and know its name. The stars the telescope's controller knows about are in the list located on the Meade Stars page. Use a star chart if you have to. (You can also align on the moon or planets but I'll leave that as an exercise for the reader to figure out - it also doesn't seem as reliable to me.) Here is a helpful way to memorize the 15 brightest stars. In the winter, it's easy to locate Orion (which has Betelgeuse and Rigel); also note that Castor and Pollux form a pair. These days there are cell phone apps which tell you what the sky looks like where you are pointing the phone; the Meade Stars page also tells you what the azimuth (angle from north measured to the east) and altitude (angle above the horizon) of each star is at the present time; this is usually enough to find bright stars. It also tells you which ones you can see (green) and which ones you can't (because they are below the horizon) (red).

Slew to the Bright Star

Slew the telescope to your star using the N, S, E, and W buttons. Make sure the speed is set on SLEW (7). In order of decreasing speed, you can also select FIND (4), CNTR (1), or GUIDE (0). Getting your star in the field of view of the telescope (or even finder) may not be so easy at first, but becomes easier with practice. Once your star is in the center of the field, consult the Meade starlist and find your star's code. The following two pictures show how you might align on Sirius.

Press STAR (6) and then the code...

...then press ENTER. The display will tell you the object's magnitude and size.

So far we've just told the computer "tell me about Sirius." To align the telescope on Sirius, hold ENTER until you hear a beep. The telescope is now aligned and we can point at more interesting objects.


Now that you're on a star is a good time to make sure the focus is correct. You can focus with the silver knob protruding from the backside of the telescope. You can also focus by moving the eyepiece in and out, but since it's complicated to describe to the public and has the potential of the eyepiece falling out, keep that trick to yourself.

Select a Target

Use the observing list. Objects are sorted by RA, which means all the objects available for viewing at any one time are all in the same half of the list. (To add items to the observing list, see my IDL routine /u/esirko/WWW/public/sky/ To go to a Messier object, press M (9) and then the Messier number. To go to an NGC object, press CNGC (3) and then the NGC number. To go to a star, press STAR (6) and then the star code. Planets are actually stars: press STAR (6) and then 901 (Mercury), 902 (Venus), 903 (moon), 904 (Mars), etc. Once you enter the code for the object you want to go to, press ENTER as before to get its information; then press GOTO and the telescope will magically slew to the right spot on the sky.

It is also possible to enter RA and Dec coordinates directly, but I'll leave that as an exercise for the reader. It usually won't be necessary.

Cleaning up

  1. Replace the lens caps.
  2. Park the telescope in the `home' position (declination about zero, hour angle about zero).
  3. Park the DOME with the slit due south. this minimizes risk from bad weather causing leaks and damage, since bad weather generally comes from the north and dome slits always leak.
  4. TURN OFF THE TELESCOPE! Otherwise the telescope will continue to rotate, once per day, and the cords will wind up and eventually rip. Or at least the motor will compete with the cords. Someone loses. It HAS happened on a couple of occasions (once by JEG!), with minimal damage, but we have been lucky. Please don't forget.
  5. CLOSE THE DOME! It HAS been forgotten, and the telescope has been snowed upon as a result. DON'T forget.


The telescope complains that an object is below the horizon when it is clearly above the horizon.
This is a symptom of the time and date not being correct.
The telescope won't rotate in its full range of motion.
This happened once when someone didn't know what they were doing, apparently, and disengaged the dec locks on the telescope as a substitute for pressing the N and S buttons.


Public observing is held generally on Wednesdays of every month, with a makeup session generally on the Wednesday following in the event of cloudy skies. These dates are arranged around the lunar calendar, in such a way that the moon is not too bright during the session; one can see very little with a bright moon, and the moon itself is blindingly bright. The times are set by the end of nautical twilight in the spring and summer, but no earlier than 7:00 to give folks time for dinner. We go through the academic year, and if we have enough enthusiastic volunteers through the summer. There are other sessions to accomodate requests from undergraduate groups, scout groups, and public school groups, in addition to some which are part of undergraduate astronomy and physics classes at the University.

Contact Stephanie (she should know, but check) in advance of observing, who will then contact the appropriate authorities, which include 1. public safety unlocking and locking the doors to Peyton hall, 2. stadium and Fine Hall lights being turned off.

Use as much information as you can in determining whether the weather will be clear at public observing. The cleardarksky clock is a helpful forecast; be familiar with their animated cloud map. But sometimes additional information is helpful; I also try to look at accuweather. Update the webpage by 3:00 on the day of scheduled public observing to indicate whether that night's session is "ON" or "CANCELED." Remember to schedule the next session and mark it as "SCHEDULED." The webpage is the file /u/www/events/openhouse.html.