Apo-tmosphere: Gutekunst ADC Review
Sep 23 2015 11:18 AM by pbsastro
Optolong LRGB Filter Testing and Comparison wit...
Sep 22 2015 01:41 PM by turbo399
First Light Review: Teeter Custom TT Planet Kil...
Sep 04 2015 12:57 PM by Zellmer
The Baader Planetarium Morpheus
Aug 20 2015 10:45 AM by wapaolini
Categories See All →
- CN Reports
- User Reviews
- How to . . .
- Observing Skills
- Astronomical History
- Optical Theory
- Vision and Related Experiments
- How to Gain the Support of your Family for your Astronomical Pursuits
- Evaluation Tips
- Special Events
- The Elements
- New Articles in [!monthname!]
- Telescope Articles
- Submit a Review / Article
- Monthly Guides
- Behind the Scenes
- About Us
- Copyright ©
- Terms & Conditions
- Tiny Eyes on the Skies
- From the Editor's Desk
- What's Up . . .
- The Light Cup Journals
- Who is this Super Light Cup?
- Cloudy Nights T-Shirts
- Imaging Contest
- Small Wonders
- Previous Imaging Contest Winners
- This Month's Skies
- Mike's Corner
- The Cloudy Nights Friends and Family Discount
- Uncle Rod's Astro Blog
- Fishing for Photons
- Binocular Universe
- Article Submissions
In spite of its advantages, the HyperStar system is not quite as easy to use as a modern day apochromatic astrograph and many users have trouble achieving good results. The problem generally isn’t with the optical system; it’s often the result of not knowing how to properly align and use the system. Although Starizona provides user instructions for aligning and using the HyperStar system, the manual is fairly basic. This guide is intended to provide additional information to get the best performance out of the HypeStar System.
Refraction changes the shape of the setting sun. The oval shape most commonly seen is just the simplest example. Much more complex changes in appearance can occur because of refraction and these are called mirages.
I can’t tell you how many negative things I had heard about them, but in their day everybody wanted one. They were the first, each one was removed from the factory, had the electronics added on and shipped back for delivery.
In 1814 Bavarian optician Joseph Fraunhofer invented the modern slit spectroscope. He demonstrated bright emission lines when burning various elements, as well as numerous dark absorption lines in the spectrum of sunlight which are in his honor still called Fraunhofer lines. In 1821 he improved the diffraction grating first invented in 1785 by American astronomer David Rittenhouse. Fraunhofer then founded stellar spectroscopy by showing that spectra of several bright stars differed from each other and from the spectrum of the Sun.
With DSLRs and standard camera lenses astrophotography is on the verge of a new epoch, where tracking is no longer absolutely mandatory. When we heard about the technique described in this article, we immediately wanted to give it a try. It allows any stargazer using a modern DSLR to capture colorful, noise-free images of deep-sky objects, without an equatorial mount or tracking device needed.
The time between sunset and night's darkness is divided into three intervals based on how brightly the sky is illuminated.
"Star light, star bright,
First star I see tonight,
I wish I may,
I wish I might,
Have the wish I wish tonight."
This familiar nursery rhyme is actually a good definition of civil twilight, which starts at sunset and continues until the brightest stars are first seen. It's the common legal meaning of twilight, as there is still light for many outside "civil" activities and most streetlights haven't been turned on. Technically it ends when the sun is 6 degrees below the horizon, or about 25-30 minutes after sunset for temperate latitudes most times of the year. Sunlight still streams 20 miles up. Nautical twilight continues from this point until the horizon blends with the sky, when the sun is 12 degrees below the horizon, about 50-60 minutes after sunset. The sun is setting at the top of the atmosphere about 90 miles (140 km) above you. Marine navigation using traditional visual methods such as sextants becomes difficult, since many of them involve a clearly defined break between sea and sky. The last interval, called astronomical twilight, starts with the end of nautical twilight and goes until the sun gets to 18 degrees below the horizon. This is the time about 70-90 minutes after sunset when no sunlight, either direct or scattered, illuminates the atmosphere above the horizon.
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.