Mastering Periodic Error Correction for Astrophotography

Periodic Error Correction

If you wish to perform high-precision astrophotography, you may wish to "train" your telescope in order to keep objects that you are imaging dead center in the telescope's mirror during the photographic exposure. Periodic error correction (PEC) helps to remove the slight perturbations from center that occur due to the mechanical nature of a telescope. To perform this procedure, you need to use a high-power reticle, such as the 9mm reticle (see OPTIONAL ACCESSORIES, page 42). PEC training is available for both drives.

Train Menu Option

If you perform this procedure in alt/az alignment, you can train the telescope in both the R.A. and the Dec. axes; in polar alignment, you need only train the telescope's R.A. axis. If you train the telescope in polar alignment, make sure that "Polar" is selected in the "Telescope: Mount" menu. "Alt/Az" is the default setting.

To perform the procedure on the R.A. axis, pick a bright star in the South that has min- imal movement and is about 30° above the horizon (Note: If in the Southern hemi- sphere, pick a star in the North that is about 30° above the horizon).

To perform the procedure on the Dec. axis, pick a bright star in the East or West that is about about 20° above the horizon.

Important Note: The Train option overwrites any previous PEC data.

1.Select "Train" from the Telescope menu and press ENTER.

2.Look through the reticle. Use the Arrow keys to keep the star centered in the reti- cle cross-hairs. Autostar II displays a count of the 200 positions of the worm gear. When the count reaches 200, one cycle is complete. A full cycle takes about 8 min- utes.

3.Press MODE to exit.

Update Menu Option

Use the Update option to further refine your training; it is recommended that you update your original training two or three times when first using your telescope. Update does not overwrite the data, but updates the training using information gath- ered from both the last and the current training sessions. Unlike the Train option, it continues onto a new cycle after it reaches a count of 200. Press the MODE key to exit from this option.

Erase Menu Option

Select this option to erase all PEC training data.

On and Off Menu Options

Select "On" when you want the telescope to use the training information. Select "Off" when you do not want for the telescope to use the training information.

LX200GPS TIPS

Star Charts

Even with the Autostar II's massive 145,000 object library, star charts and planispheres are still useful for a variety of reasons. In particular, they are a great aid in planning a night of celestial viewing.

A wide variety of star charts are available in books, in magazines, on the inter- net and on CD Roms. Meade offers Epoch 2000sk™ and other star locator software. Contact your Meade dealer or Meade's Customer Service depart- ment for more information.

Astronomy and Sky and Telescope magazines print star charts each month for up-to-the-minute maps of the heavens.

The Norton Star Atlas and Reference Handbook by A. Norton and Sky Atlas 2000 by W. Tirion and R. Sinnot are two of the most popular star charts on the market.