Ghosts in the Machine: the Astro-Tech AT111EDT...
Jun 13 2015 11:23 AM by jrbarnett
My NexStar 5 Journey
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Review- Printing Astro photos on Metal with Bay...
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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.
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.
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?
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.
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.
This glossary was complied largely from a thread called “Astronomy Terms for Fun” on the General Observing Forum of Cloudy Nights.
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.