A 6V Lead-Acid Battery Charger Using the LM555

How do you power a device that must stay on through an event that may cause a power outage? Battery backup of course. But that answer leads to whole new level of complications. There must be a circuit in place to allow power to be drawn from the battery or the power supply. The proper battery technology should be chosen. You need a another circuit to care for the battery, allowing for very long term reliability. Long term? Years.

6V Lead-Acid Battery Charger
A 6V lead-acid battery charger based on the venerable LM555.
A good answer for the battery technology is sealed lead-acid. A properly used lead-acid battery should last a decade or more while providing power to operate for over a day. Lead-acid may not be a good choice for a portable device where weight and size are the primary considerations. But for a stationary application this venerable technology is a good choice.

What about the charge circuit? A simple charger that can fully charge the battery, but not overcharge the battery is needed. In the case of lead-acid charging is usually accomplished by charging to a chosen voltage before shutting off or lower the voltage to a safe lower value called a “float charge”.

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The Moon and Venus

Tomorrow morning, April 23rd, a pretty crescent Moon will be located close to a brilliant Venus. The Moon will be a slim 12% crescent a little over 7° from Venus shining at -4.3 magnitude. The pair will rise about an hour before sunrise at about 4am, look for the two just above the brightening glow of dawn.

e Moon, Venus and Aldebaran
The Moon, Venus and Aldebaran join up for an evening conjunction

Mercury at Inferior Conjunction

Today Mercury will be at inferior conjunction. After today the planet will reappear in the dawn, rising high enough from the Sun’s glow to be seen around the end of the month.

Mercury Transit 9May2016
Mercury transiting the Sun on May 9, 2016. Celestron C8 and Canon 6D at f/10.
Inferior conjunction is when the planet passes between the Sun and the Earth. As such the only planets to see inferior conjunction are Mercury and Venus. A transit is possible if the planet passes directly in front of the Sun, but normally this alignment does not occur, the planet passing above or below the Sun as seen from the Earth. There are no transits of Mercury in 2017, the next will be Nov 11, 2019.

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Primordial Galaxy Discovered, First of Its Kind

MACS1423-z7p64 galaxy
Graphic illustration of how MACS1423-z7p64 was detected via gravitational lensing with NASA’s Hubble Space Telescope and confirmed by W. M. Keck Observatory’s MOSFIRE. Credit: NASA/W. M. Keck Observatory/A. Hoag/M. Bradac
W. M. Keck Observatory press release

Seven years of meticulous observing have resulted in a cosmic discovery that comes from an era dating back 13.1 billion years, giving scientists a detailed glimpse of what may have happened just after the Big Bang.

Using the world-class W. M. Keck Observatory on Maunakea, Hawaii, an international team of astronomers from the United States, Australia, and Europe has confirmed the existence of one of the most distant galaxies in the universe.

To characterize the faint galaxy, the discovery team, led by Austin Hoag, a University of California, Davis physics graduate student, used MOSFIRE, the most in-demand instrument on the 10-meter Keck I telescope.

What makes this galaxy extraordinary is that it is ordinary. It is thought to be a common galaxy at that distance and age of the universe. However, such galaxies would normally be too faint to detect. The astronomers used a method called gravitational lensing to magnify the galaxy so they could study it.

“Most objects that we’ve seen at that distance are extremely bright, and probably rare compared to other galaxies,” said Hoag. “We think this galaxy is much more representative of other galaxies of its time.”

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W. M. Keck Observatory Achieves First Light with New Instrument

W. M. Keck Observatory press release

W. M. Keck Observatory overnight captured the very first successful science data from its newest, cutting-edge instrument, the Keck Cosmic Web Imager (KCWI).

KCWI First Light Image
KCWI’s first look at the cosmos involved a spectral image of an exquisitely dense core of an ancient astronomical relic, showcasing the highest spectral resolving power and spatial resolution of the instrument. Credit W. M. Keck Observatory
KCWI captures three-dimensional data, as opposed to the traditional two-dimensional image or spectrum of conventional instruments. In a single observation, it records an image of the object at multiple wavelengths allowing scientists to explore both the spatial dimension (as in an image) and the spectral dimension (or color) of an object.

“I’m thrilled to see this new instrument,” said Keck Observatory Director Hilton Lewis. “It takes years to design and build these very sophisticated instruments. KCWI is a superb example of the application of the most advanced technology to enable the hardest science. I believe it has the potential to transform the science that we do, and continue to keep Keck Observatory right at the forefront of astronomical research.”

KCWI is extremely sensitive, specifically designed to capture high-resolution spectra of ultra-faint celestial bodies with unprecedented detail. It is able to differentiate even the slightest changes in spectral color with a great degree of accuracy.

This powerful capability is key for astronomers because a highly-detailed spectral image allows them to identify a cosmic object’s characteristics, including its temperature, motion, density, mass, distance, chemical composition, and more.

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The Canon EF-M 28mm f/3.5 Macro IS STM lens

There are not a lot of native lenses found in the Canon EF-M series, but this is changing with a number of new offerings. There is a new 18-150mm general purpose zoom that looks pretty good.  The new lenses include a rather specialized lens, the EF-M 28mm f/3.5 Macro IS STM, a purpose built macro lens.

EOS M5 and 28mm f/3.5 macro lens
EOS M5 and 28mm f/3.5 macro lens

This lens is different. The lens is designed from the start to be a macro lens, not a general purpose lens that also does a little macro as a secondary feature.  There are a number of features that are quite unusual found on this macro lens.

The first, and most obvious feature is the built-in ring light, a rather useful feature in very close macro photography where light is everything. A set of bright white LEDs is arranged on the front of the lens behind a diffuser. The LED’s are powered by the camera, no separate battery is necessary.

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