The bright planet Venus will appear in the dawn sky over the next couple weeks, climbing higher to become the morning star for the remainder of 2017. It is currently 15° from the Sun and shining at magnitude -4.3, bright enough to be seen against the dawn sky. It will reach maximum elongation on June 3rd, 46° ahead of the rising Sun.
I took a break from working with a “big” microcontroller to work with a little one. The PIC12C671 is definitely little when compared with the PIC18F66K80 I am using in the GenPIC utility PCB. With less than 2k of program space and a mere 128 bytes of RAM it is definitely limited. Consider that the chip only has eight pins, two of which are power and ground, leaving six I/O pins to get the job done. No problem, I only need two I/O pins for this task and that few bytes of RAM is more than enough!
A simple heater using a bang-bang controller.This project is pretty basic… A bang-bang heater controller. This simple form of controller simply turns on and off as the temperature (or some other controlled parameter) goes up and down, there is no attempt to vary the output, all or nothing. Bang on, bang off, or simply a bang-bang controller as it is known in the trade.
A bang-bang controller is inherently reliable and stable because it uses two different control setpoints, a high and a low. Because these control points are separated by a large margin, called hysteresis, the controller will not oscillate or rapidly turn on and off. In this case the heater will not turn on until the temperature falls below 10°C and will not turn back off until the temperature rises above 15°C. That five degree margin is called hysteresis, and ensures a good period of time between on and off.
Today Mercury will be at maximum eastern elongation, as high in the evening sky as it will appear for this current apparition. After today the planet will slide back into the sunset, passing through inferior conjunction on April 19th to reappear in the morning sky around the end of the month.
Mercury transiting the Sun on May 9, 2016. Celestron C8 and Canon 6D at f/10.Mercury typically completes three morning and three evening apparitions in each year. While the innermost planet never gets very far from the Sun, maximum elongation represents the best time to observe Mercury as high in the sky as possible.
There are no transits of Mercury in 2017, the next will be Nov 11, 2019.
Today Venus is at inferior conjunction, passing between the Earth and Sun. It will reappear in the dawn sky early next month to become the morning star for the remainder of 2017. The planet will reach maximum elongation on June 3rd at 46° from the Sun.
Venus approaching inferior conjunction, 24Dec2013As Venus emerges from the Sun’s glare it will be a fine crescent, growing thicker each day as we see more of the sunlit side of the planet. While it is still low in the dawn it can be a fine telescopic target. It is these phases of Venus that Galileo noted 400 years ago, one more bit of evidence to the true, Sun centered, nature of our solar system.
Across the room from my desk is a large cabinet full of blueprints and sepia prints. Stacks of large prints that represent the original drawings from which the W. M. Keck Observatory was constructed. Floor plans, foundation plans, the structural steel of the telescope itself.
The original blueprints by which Keck Observatory was constructedThe prints are in many ways works of art. Often drawn by hand these old prints represent a lost skill, the art of the draughtsman from before computers irreversibly changed the profession. Impeccably neat lettering, an arcane menagerie of symbols, coded shading to represent different materials, it takes time just to learn to read these drawings properly.
Late last fall I put a new vegetable bed into use. After several years of accumulating compost and shoveling cinder soil I actually have something like real soil in a large enough quantity to call a vegetable garden.
One of the first things planted were sweet potatoes. Deb and I love the local purple sweet potatoes. The Okinawan variety is a favorite through the islands and has become a staple on our table as well, usually purchased from local growers at the farmers market.
Knowing that these are pretty easy to grow I gave it a try. I planted a ten by ten area with half a dozen slips and arranged a soaker hose that runs on the automatic drip system. It was not long before I had green foliage popping up. The potato patch certainly looks healthy enough, the plants thriving in the Waikoloa sunlight. The patch quickly became a heavy tangle of vines with pretty white and purple flowers.
A single enormous Okinawan sweet potato tuber from our garden.This weekend I finally decided to do a trial run at digging up a plant to see what I have… To my stunned amazement I have not a pile of little tubers, but one giant tuber right underneath the main plant. What the heck is this?
This thing was huge, six inches long and five inches in diameter, weighing several pounds. There was enough in this single tuber for several meals!
Consider the usual Okinawan sweet potato is an inch or two in diameter and four or five inches long. Why is this so different? The starting stock for my potato patch was quite typical, just a few Okinawans I had bought at the farmers market and set aside for planting. I expected to get much the same out of the ground, not this giant.
