Orion 9862 Using the Polar Axis Finder, Tracking Celestial Objects, Optional Motor Drive

7.Rotate the mount 180° about the R.A. axis. Again, it may be convenient to remove the counterweights and optical tube first.

8.Look through the polar finder again. Is the object being viewed still centered on the crosshairs? If it is, then no fur- ther adjustment is necessary. If not, then look through the polar finder while rotating the mount about the R.A. axis. You will notice that the object you have previously centered moves in a circular path. Use the three thumbscrews on the housing to redirect the crosshairs of the polar finder to the apparent center of this circular path. Repeat this proce- dure until the position that the crosshairs point to does not rotate off-center when the mount is rotated in R.A. Once this is accomplished, retighten the thumbscrews.

The polar axis finder scope is now ready to be used. When not in use, replace the plastic protective cover to prevent the polar finder from getting bumped, which could knock it out of alignment.

Using the Polar Axis Finder

When using the polar finder in the field at night, you will need a red flashlight to illuminate the finder’s reticle. Shine the flash- light at an angle into the front opening in the R.A. axis. Do not shine it directly into the opening, or the light will be too bright, and you will also obstruct the view of the polar finder. It may be helpful to have a friend hold the flashlight while you look through the polar finder.

For most accurate polar alignment, you will need to know the approximate longitude of your observing site. This information can be obtained by looking at a local map. Now, figure the difference between the longitude of your observing site and the closest standard time meridian. The standard time merid- ians are 75°, 90°, 105°, and 120° for the 48 continental states (150° and 165° for Hawaii and Alaska). Choose the standard time meridian that is closest in value to your local longitude, and then calculate the difference. If your local longitude has a value less than the closest standard time meridian, you are east of the standard time meridian by the calculated amount. If your local longitude has a value greater than the closest standard time meridian, you are west of the standard time meridian by the calculated amount. For example, if you are in Las Vegas, which has a longitude of 115°, the closest stan- dard time meridian is 120°. The difference between these two numbers is 5°. Since Las Vegas’ longitude value is less than the standard time meridian value, you are 5° east of the clos- est time meridian.

Take your calculated difference from the closest standard time meridian and rotate the date circle so that the meridian off- set scale line that corresponds to your calculated difference lines up with the engraved time meridian indicator mark on the polar finder housing. Each line of the meridian offset scale represents 5° of longitude. Lines to the left of the “0” on the meridian offset scale indicate east of the closest standard time meridian, while lines to the right of the “0” indicate west of the closest standard time meridian.

Continuing with the prior example of observing in Las Vegas, you would rotate the date circle so that the first line to the left

of the “0” on the meridian offset scale lines up with the time meridian indicator mark.

Make sure that the “0” mark on the R.A. setting circle lines up with the pointed indicator cast into the mount, and that the large thumbscrew just above it is tightened. Now, rotate the mount about the R.A. axis until the line on the R.A. setting circle that corresponds to your current local time lines up with the line on the date circle that indicates the current date. If you are on daylight savings time, subtract one hour from your current local time. For example, if it was November 1 at 9 PM, standard time, you would rotate the telescope in R.A. until the line above the “21” (9 P.M.) on the R.A. setting circle lines up with the long line between the “10” and “11” on the date circle. The long line indicates the first day of the higher numbered month, i.e. the line between “10” and “11” marks November 1st.

Finally, look through the polar alignment finder scope while shining a red flashlight at an angle down the front opening of the R.A. axis, and center Polaris in the small circle. Adjust the tilt of the altitude up-or-down with the latitude adjustment T-bolts and use the azimuth fine adjustment knobs (Figure 8) for final positioning. To do this, you will first need to loosen the big tripod attachment knob directly underneath the base of the equatorial mount. The fine adjustment knobs work by loosen- ing one and then tightening the other. When done, retighten the tripod attachment knob to firmly secure the mount and tri- pod. If the fine adjustment knobs do not allow the mount to move far enough to center Polaris, you will need to rotate the entire tripod left or right to get it within the fine adjustment’s range.

Once Polaris is centered in the small circle, you are done. The telescope is now accurately polar aligned, and can be used for advanced observational applications, such as astro- photography or precise use of the manual setting circles. As mentioned before, only move the telescope along the R.A. and Dec. axes; if you move the tripod, or change the tilt of the equatorial mount, you will need to polar align again.

Remember, accurate polar alignment is not needed for casual visual observing. Most of the time, approximate polar align- ment, as outlined previously, will suffice.

Tracking Celestial Objects

When you observe a celestial object through the telescope, you’ll see it drift slowly across the field of view. To keep it in the field, if your equatorial mount is polar-aligned, just turn the R.A. slow-motion control. The Dec. slow-motion control is not needed for tracking. Objects will appear to move faster at higher magnifications, because the field of view is narrower.

Optional Motor Drive

Optional DC motor drive systems can be mounted on the AstroView 100 EQ’s equatorial mount to provide hands-free tracking. Objects will then remain stationary in the field of view without any manual adjustment of the R.A. slow-motion con- trol. A motor drive system is necessary for astrophotography.

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