Rough polaraxis alignment on Polaris

Your task is to find Polaris, then aim the telescope directly away from its base (Figure 4.7) and center Polaris by adjusting the tripod. The computer in the telescope is not involved, and if you can unlock the brakes and move the telescope manually, the computer need not even be turned on.

After centering Polaris, you can obtain greater accuracy by moving about 0.8° toward Cassiopeia, away from Ursa Major.

JANUARY

CAMELOPARDALIS

CASSIOPEIA

CC 111 m O

CEPHEUS I

Polaris

/ "Pointers"

*KochabURSA MAJOR

/ DRACO

Mizar /

Ainr

Figure 4.6. Field of Polaris. To see the orientation at 9 p.m. local time, put the current date at the top.

To celestial pole

(align on Polaris by adjusting wedge and tripod)

Telescope aimed directly away from Its base (critical)

Eyepiece between fork arms. Rotate telescope around polar axis as needed for access to finder

Angle normally equal to latitude, but alignment on Polaris takes precedence

Setting circle (if present) reads 90°

Leveling of base helpful but not critical

Setting circle (if present) reads 90°

Leveling of base helpful but not critical

Eyepiece between fork arms. Rotate telescope around polar axis as needed for access to finder

Angle normally equal to latitude, but alignment on Polaris takes precedence

Figure 4.7. During polar alignment, the telescope points directly away from its base.

To celestial pole

(align on Polaris by adjusting ^ wedge and tripod)

Figure 4.8. A simple tool for aligning a wedge before putting the telescope on it.

Actually doing this may not be easy. One challenge is getting the telescope pointed directly away from its base. Meade LX200 and ETX telescopes have setting circles to tell you when they are in this position; the NexStar 5 does not. Even if you have setting circles, they may not be accurate (see p. 34). The computer is no help because it can't read declinations accurately until you have sighted on some stars. Don't panic; if you point the telescope away from its base "by eye" you'll get close enough to start. Later, you can find the proper position with a bubble level and mark it.

A more serious problem is that you may not be able to look through the telescope or its finder while it is in this position. You are free to swivel the telescope around its polar axis (slew in right ascension) as needed, since the telescope is aimed directly away from its base the whole time. But even so, the eyepiece and/or finder may remain inaccessible between the fork arms.

In that case, the gadget in Figure 4.8 will prove indispensable. It enables you to line up the mount before putting the telescope on it. I made my own, with an old finder and a block of wood, but commercial versions exist. Drilling must be done carefully, with a drill press, for good perpendicularity.

Remember that Polaris is 0.8° away from the true pole, in the direction of the fainter end of Cassiopeia, away from the handle of the Big Dipper. As far as possible, line up on that point rather than on Polaris itself.

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