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The Best Telephoto Lenses for Astrophotography

Jun 27 2015 04:15 PM | rekokich in Articles

Over the years, I have tried more than two dozen telephoto lenses, until I finally found three or four perfect solutions. But first, there are several general rules which must be understood.

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How to Better Balance Big Binos

Jun 27 2015 03:03 PM | jtsenghas in Articles

Have you ever mounted large binoculars on a parallelogram mount, whether or not you built it yourself, and struggled with having it balance well at various angles, drifting up or down at various heights, but balancing perfectly at others? Here are explanations of the two-dimensional nature of this behavior and tips for minimizing it, along with a spreadsheet tool with graphical output which may help you to improve your existing setup or to design a better one.

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The World's Simplest Telescope -- Now you c...

Jun 27 2015 01:00 PM | ed_turco in Articles

This is a very worthwhile, instructive project for young and old. Try it and be amazed!

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A new Performance Index for Binoculars

Jun 13 2015 01:24 PM | Fomalhaut in Articles

Closing a gap in the technical literature on the topic of the visually accessible stellar limiting magnitude.

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Blue Skies, Red Sunsets & Company Part 2: S...

May 25 2015 02:19 PM | Snickersnee in Articles

When the sun is on the horizon, then the line between darkness and light created by the glowing sun and the shadow-casting earth is sweeping through your position. It's called the terminator as it terminates or ends the daylight. The terminator passes overhead twice a day with sunrise and sunset. At sunrise, the effects of the daily pageant play with darkness giving way to light, while for sunset the sequence is simply reversed. Descriptions here with the sunset will mean things that can happen at both times of day.

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The Definitive Newtonian Reflector

May 11 2015 12:30 PM | ed_turco in Articles

Amateur astronomers and telescope makers have debated from time immemorial the advantages and disadvantages of different telescope designs.  In particular, mountains of hard copy and electronic articles are available on the merits of refracting and reflecting telescopes, more recently, apochromatic refractors vs. Newtonian reflectors. This debate has become rather rancorous (Newtonian telescopes as APO "killers" comes to mind.) and unscientific, to say the least. And when all is said and done, in a discourse without loaded words and acrimony, a discussion devolves to one concerning perfect optics.  And isn't this what we all want or wish we had?

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Blue Skies, Red Sunsets & Company: Part 1:...

Apr 16 2015 02:37 PM | Snickersnee in Articles

Sunsets, sunrises and twilight, as well as clear blue skies and the less familiar crepuscular rays, mirages and green flashes are all examples of atmospheric optical effects that can be readily seen at many times of the year from many places on the earth. No special equipment beyond your eyes, a bit of patience and an openness to learn is needed to see and feel the beauty of the interaction of natural light and the air.

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A tale of two craters

Apr 15 2015 12:40 PM | skyaddict in Articles

Most craters on the Moon are named after famous individuals associated with our satellite, and those on Mare Crisium, the 'Sea of Crises' are no exception. After a little map reading, I decided to make the focus of my evening’s viewing a pair of craters named after the founders of two of the most famous Observatories on Earth.

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Apr 01 2015 03:00 AM | Doc Willie in Articles

This glossary was complied largely from a thread called “Astronomy Terms for Fun” on the General Observing Forum of Cloudy Nights.

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Virtual Pinhole

Nov 25 2014 01:26 PM | NJJ in Articles

I have devised a laser collimation test for Cassegranian systems. An on axis laser beam falling onto a 3M type reflective film creates a “virtual pinhole.” The backscattered light is sufficient to form an adjacent image from the primary that may be adjusted until it is brought into coincidence with the “virtual pinhole. This collimates the primary and allows the secondary to be collimated by conventional process, similar to Newtonians.

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