Telescope Reviews: Constellations Obsolete in Astro Guides & Lists?

Planispheres

There has not been a lot of talk in this thread about planispheres (possibly one or two references). I thought I would say a few words about this simple, yet effective instrument to estimate locations of constellations, bright stars, Messiers, and RA and DEC coordinates.

How I use a planisphere to estimate RA in the night sky

The way I estimate RA in the night sky is to use a planisphere, along with a watch and a field compass.

The field compass marks the fixed meridian or transit line (North-South line passing from the Northern horizon through zenith to the Southern horizon). While the RA hours do change throughout the night, the meridian is permanent from a single observing position. However, if I move to a new observing position on the ground, I need to take a new meridian reading.

The hole in the center of the planishere is Polaris, the North star, from which all RA lines radiate. I rotate the planisphere to align the current month, day, and time.

Next, I hold the planishpere up against the sky with the hole in the center covering the actual North Star in the sky. The lines and tick marks on the planisphere for each of the 24 RA hours enable me to estimate the position of RA hours in the night sky radiating from the North Star. The planishere also has DEC tick marks for estimating DEC°.

As the time changes throughout the night, I rotate the planisphere to align the new time with the month and date, and again hold the planisphere over the actual North Star in the sky to estimate the new RA postions.

Observing at meridian

Now is a good time to bring in the oft-quoted and long out-of-print 1001 Celestial Wonders, 3rd ed. (Barnes, 1931), a well written observing guide for keeping one's telescope fixed at meridian over the course of 12 months. Read the magic as the RA 5th hour transits Barnes's meridian on January 13, 1926, at 9 p.m. (p. 51).

For who would acquire a knowledge of the heavens in little, let him give up his days and nights to the marvels of Orion. Here may be found every conceivable variation of celestial phenomena: stars, giants and dwarfs; variables, doubles, triples, multiples; binaries visual and spectroscopic; clusters wide and condensed; mysterious rayless rifts and nebulae in boundless variety, with the supreme wonder of all supernatural wonders at its heart--the Great Nebula--before which the learned and the laymen alike have stood silent in awe and reverence since the first lens unfolded to man's gaze its true vastness and intricacy; and which offers abundant field for all the geniuses of science, with their super-refinements of means and methods, for generations to come. To know Orion is to know astronomy! Which planisphere do I use?

I prefer David Chandler's The Night Sky planisphere over other planispheres because it has lines and tick marks for each of the 24 RA hours and every 10° of DEC. Some planispheres I have seen only have lines for every 3 RA hours. In addition to RA and DEC, most planispheres also have visible Constellations marked, as well as many bright stars and Messiers.

If I am sitting at my desk and want to consult a planisphere, I often use the planisphere views in the SkyTools 3 software program or reach for Sky & Telescope's Star Wheel.

In my easy chair, when I read an astronomy magazine or observing guide, I like to have S&T's Star Wheel at my side because of its large size and colorful sky background printed on heavy cardboard. As I read about an interesting star or DSO, I pick up the planisphere to find out when it will be visible from my location.

However, for outside use in the dark, I prefer David Chandler's planisphere because of its simplicity and plastic material.

--------------------
Bob
38°N