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The Rock
The Workshop
This first one is from a few years ago when I installed a large rock feature in my garden. As you will see, it brought out the caveman in me!
This one is from 2012. After working in a cramped annex to the kitchen for a few years I finally got round to building the ultimate man cave.
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It's Finished!
14 July 2014
Telescope Build
At last my telescope is complete! I first ordered the lens in November 2010 and I finally got my first look at the moon this Friday night.
 
The view is truly awesome. No hint of false colour and stars appear as white pin pricks over the whole field. Barry Greiner of D&G Optical certainly is a master lens maker. It has all been worth the wait. Here is a spec list for those in the know.
 
Objective type:              Two element achromat.
Objective Diameter:      6 inches.
Objective focal ratio:     F/20 (to suppress false colour without the expense of an APO).
Focuser:                        TS Optics 2 inch Crayford.
Star Diagonal:               William Optics 2 inch, 90 degrees.
Eyepieces:                    2 inch, 50 mm Erfle, 1.25 inch, 25 mm Plossl and 1.25 inch, 10 mm Vixen Lanthanum.
 
Click on the image below to see a slide show of the build. It is a large file so you may have to wait for it to download:
 
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Sunlight Flicker
07 July 2014
It is well known that the intensity of the light emitted by the sun varies over time. Most studies of solar intensity variation have concentrated on long term changes ranging from a few minutes, to days and even years.
 
These long term variations are not flicker in the way that most people understand the term. When we think about flicker we usually think of the flickering of a candle or the fluctuating light put out by an open fire. It relates to sub-second variations in light level.
 
Our everyday experience of sunlight would tend to indicate that it is constant, and flicker free. Clearly, if the sun does flicker, the effect is small. But how small is it? Is it measurable? How big are the short term fluctuations in comparison with the total amount of light?
 
After extensive searching through the available literature I have found that our knowledge in this area is woefully lacking. My question simply can't be answered in any meaningful way.
 
For Badobadop, this poses a challenge. Now that I have finished my telescope (full update next week), I have decided to measure the amount by which sunlight flickers and answer this puzzling question. You never know, I may be able to publish a short paper outlining my findings.
 
 
 
 
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I have already built a sunlight detector and I can confirm that there are measurable intensity fluctuations covering the frequency range 10 to 100 Hz. However, the results I have obtained do not eliminate the effects of the earth's atmosphere. I am currently building a second sunlight detector. Hopefully, cross correlating the outputs from spatially distant detectors will confirm that at least some of the variation I have observed really is sunlight flicker.
 
Watch this space!
Badobadop's solar flicker detector under construction.
Image: NASA
Sunlight Flicker
14 July 2014
Here is a follow up on last week's Did You Know? on sunlight flicker. You will recall that I had made a sunlight flicker detector and was in a position to confirm that there are measurable intensity fluctuations in the 10 Hz to 1 kHz range.
 
This week I have a picture of the completed sunlight flicker detector which is housed in two tin baked bean cans. I have also made a recording of the intensity fluctuations. Since the recording is in the audio frequency range, it can be listened to with headphones.
 
 
 
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Badobadop's completed solar flicker detector.
Image: NASA
As you listen to the recording you will notice two silent sections. The first is with the detector pointed at the sky, but away from the sun. The second is with the detector covered with my hand.
 
I am still unable to confirm that the variations I have recorded are solar in origin. It is possible that they are caused by atmospheric effects. However, I have now made a second, identical detector. I intend to use this to make simultaneous recordings a few meters apart. Since the light will be arriving at each detector through different columns of air, any correlation between the two signals will be evidence of a solar, as opposed to an atmospheric source. If I get correlation over a few meters, I will then make simultaneous recordings some 100 miles apart. Hopefully, I will then be able to positively confirm that at least some of the intensity variation is solar in origin.
Click the thumbnail to listen to an MP3 recording of sunlight flicker. Use headphones for a good low frequency response.
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Badobadop's Latest Project: Sub-second Solar Variation
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