Celestron C10-N, C8-NGT manual Alignment Procedures, Startup Procedure

Mount Calibration

After an Auto Align is successfully completed, the hand control will display the message, Calibrating...

This automatic calibration routine is necessary to calculate and compensates for "cone" error inherent in all German equatorial mounts. Cone error is the inaccuracy that results from the optical tube not being exactly perpendicular to the mounts declination axis as well as various other inaccuracies such as backlash in the mounts gears. The telescope is able to automatically determine the cone error value by always using alignment stars on both sides of the Meridian (see Figure 3-2). Mechanical errors can be reduced further by always centering alignment stars using the up and right arrow buttons as described in the Pointing Accuracy box below.

Alignment Procedures

In order for the telescope to accurately point to objects in the sky, it must first be aligned to three known positions (stars) in the sky. With this information, the telescope can create a model of the sky, which it uses to locate any object with known coordinates. There are many ways to align your telescope with the sky depending on what information the user is able to provide: Auto Align allows the telescope to select three stars and uses the entered time/location information to align the telescope; Auto Three Star Align involves the same process as Auto Align, however it allows the user to select which star to use to align the telescope. Quick-Alignwill ask you to input all the same information as you would for the Auto Align procedure. However, instead of slewing to the alignment stars for centering and alignment, the telescope bypasses this step and simply models the sky based on the information given. Finally, Last Alignment restores your last saved star alignment and switch position. Last Alignment also serves as a good safeguard in case the telescope should lose power.

Startup Procedure

Before any of the described alignments are performed, the telescope mount needs to be positioned so that the index marks are aligned on both the right ascension and declination axes (see Fig 2-8).

First index its switch position so that each axis has an equal amount of travel to move in either direction. Once the index position has been set, the hand control will display the last entered date and time information stored in the hand control. Once the telescope is powered on:

1. Press ENTER begin the alignment process.

2. The hand control will ask the user to set the mount to its index position. Move the telescope mount, either manually or with the hand control, so that the index marked in both R.A. and Dec are aligned (see Fig 2-8). Press Enter to continue.

3. The hand control will then display the last entered local time, date, time zone, longitude and latitude.

• Use the Up/Down keys (10) to view the current parameters.

• Press ENTER to accept the current parameters.

• Press UNDO to enter current date and time information into the hand control. The following information will be displayed:

Time - Enter the current local time for your area. You can enter either the local time (i.e. 08:00), or you can enter military time (i.e. 20:00 ).

• Select PM or AM. If military time was entered, the hand control will bypass this step.

• Choose between Standard time or Daylight Savings time. Use the Up and Down scroll buttons

(10) to toggle between options.

•Select the time zone that you are observing from. Again, use the Up and Down buttons (10) to scroll through the choices. Refer to Time Zone map in Appendix for more information.

Date - Enter the month, day and year of your observing session.

•Finally, you must enter the longitude and latitude of the location of your observing site. Use the table in Appendix C to locate the closest longitude and latitude for your current observing location and enter those numbers when asked in the hand control, pressing ENTER after each entry. Remember to select "West" for longitudes in North America and "North" for latitudes in the North Hemisphere. For international cities, the correct hemisphere is indicated in the Appendix listings.

4. Select one of the four alignment methods as described below.

17