Many sophisticated methods of evaluating the optical quality of a telescope have been developed over the years. But there’s one very simple, convenient, and sensitive test that’s easy to perform any clear night. Known as the extrafocal image test, it uses an actual star as the test source.
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Category Archives: Sky Talk
Three Plus One = Four Planets At Dusk!
A dramatic trio of planets play tag with each other after sunset low in the west-northwestern sky during the last week of this month–along with a lone lovely planet in the southeastern one all month long. Here’s an opportunity to see the two innermost and fastest-moving planets bunched together with the largest of all such worlds, and across the evening sky the most beautiful planet in the entire heavens.
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Monster Telescopes!
For decades after its dedication in 1948, the famed 200-inch Hale reflecting telescope at Palomar inCaliforniareigned supreme as the world’s largest telescope. (Russiahad built a somewhat bigger one but it never performed as hoped.) Then came the twin 400-inch scopes at the Keck Observatory inHawaii, twice as big as Hale. But now, two instruments are in the works that will absolutely dwarf all those that have come before them!
Comet PanSTARRS Alert!
Skimming along the western horizon some 30 to 45 minutes after sunset in March, a bright new comet will be making its appearance in our evening sky. Predicted to be easily visible even to the unaided eye—and sprouting a noticeable tale pointing northward— it promises to be quite a spectacular sight in binoculars and wide-field telescopes.
What Type & Size Telescope Is Best?
Those new to the hobby of astronomy who are considering a telescope purchase typically wonder just which type and what size are the best choices. This month we provide no-nonsense succinct guidelines to help answer these questions.
Jupiter Rules the Night
Appropriately for the king of the planets, giant Jupiter dominates the night sky beginning this month (and well into the spring as well). And as January opens, it gets off with a bang sky-wise with a meteor shower. Throw in the bright winter constellations like Orion now in full view and you have a wonderful way to spend a clear cold evening!
This Year’s Best Meteor Shower!
The 2012 Geminid Meteor Shower promises to be the most spectacular of all this year’s major annual displays of “shooting stars.” Be sure to mark Thursday evening into early Friday morning, December 13th to 14th, on your calendar and plan to head outdoors if skies are clear. The total absence of the Moon and an early evening start to the event combine to make ideal conditions for meteor watching this month.
Observing The Aurora Borealis
With our “Daytime Star” now revving up for another sunspot maximum in 2013, displays of the beautiful Aurora Borealis are becoming increasingly numerous. They are considered nature’s grandest light show and if you’ve never witnessed one, be prepared to be “wowed”! And the best part is that no equipment is needed-just your eyes (with their amazing “all-sky” viewing capability) and a clear night. Continue reading
The Amazing “Coathanger” Asterism
The night sky is full of wonders of many kinds. One of the most common and surprising are the groups of stars known as “asterisms.” These are distinctive stellar patterns lying within a constellation or, in some cases, one made up of those from two or more adjoining constellations.
Some are so unusual and artificial-looking that they seemingly couldn’t possibly be real! One of these is the famed “Coathanger” asterism, now well placed for viewing with your Edmund binoculars on October evenings. Continue reading
The Moon’s Non-Rotation & Dark Side
Two of the enduring misperceptions of astronomy are that the Moon doesn’t rotate since we see the same side of it all the time, and that the back side of the Moon is its dark side. But neither one is true! A simple demonstration in the one case and a bit of logic in the other will quickly dispel both myths. Continue reading
