Friday, September 10, 2021


For lifelong learning, most of your time will probably be spent in your own neighborhood, and that's okay. The same things that make the universe go, that create stars and make atoms spin, are the same things that make your local world go. And all places have their points of interest.
I live at the western edge of the great plains. We have some nice wildflowers including my favorite, milkweed. The plains are home to spectacular sunflowers and there's a patch of solanum rostratum, buffalo bur, that had taken up in our back yard.

But the headliners of the plains are the grasses and their relatives, the sedges and rushes.

Most people aren't that impressed with grasses. They aren't very colorful. "Hey. I have a lawn. What's so special about grass?"

What grasses lack in color, they more than make up for in patterns. Take the three grasses I spotted the other day on a grocery run.

Setaria grasses include some of our  grains like millet and korali. These wild ones are little puffs.

These silky grasses are called bromus or cheat grasses. I identified them using Google Lens, an app that will take a photo and give you options to identify what's in the picture. I've found it very useful for identifying everything from wild plants and animals, to architecture, to landscapes. 

Blue Grama, the state grass of Colorado, puts out feathery blooms. 

Different grasses bloom and seed at different times so any hike down the Little Dry Creek trail will give me something different to see.

What's special about your area?

Monday, September 6, 2021

Three shades of twilight

It's hard to pinpoint when twilight - dawn and dusk - begins or ends. If I hike to the top of the hill, right around where I stop in at Milano's Coffee for a milkshake, I can see the horizon out on the plains and, as soon as the center of the sun clears the horizon, that's the end of twilight. But dawn begins as a gradual lightening of the skies.

I can't see the geographic horizon to the west since the massive mount Evans blocks my view, so I have no visual indication of when dusk begins or ends. 

Astronomers can be much more precise. There are three stages of twilight. Say that you are on a hike along a trail and you expect it to turn into a night hike. You will notice that, even after the sun has set, you will have some time before you have problems seeing what's around you. That's called "civil twilight." Astronomers peg it from the time the center of the sun drops below the horizon to when it is 6° below the horizon.

As you continue to walk, you can still see pretty much where you're going but it's harder to see objects at the side of the trail. And you can see some of the brighter stars. This is the time of "nautical twilight". This was prime time for ancient mariners because they could see both the horizon and navigational stars like Polaris and navigation was easy. For astronomers, nautical twilight is the period when the center of the sun is from 6° below the horizon to when it is 12° below the horizon.

Pretty soon, you have to pull out your flashlight to see where you're going. Keep the red light mode on so you don't destroy your night vision. There's still a little light but the stars are beginning to really put on a show. You might see tiny stars shining back at you from the undergrowth, eyes reflecting your light back at you. This is "astronomical twilight" when the center of the sun is from 12° to 18° below the horizon. After that is night proper until the sequence reverses in the east with the beginning of dawn.

You can pinpoint the three stages of dawn and dusk by pulling up the Time and Date website:

and type the name of the nearest town into the search bar at the top of the home page. You'll get a lot of information including a link entitled "Show more twilight and moon phase information". It will take you to a page that gives you all the times of day (and night, and all the twilights.)

Between day and night is a band of half-light, called the "terminator", that moves across the globe as the Earth rotates. If you have Google Earth, you can see it. There's a button in the toolbar at the top labeled something like "Show sunlight on the landscape."

How broad is the band? That varies according to the time of year and your latitude, but with those two pieces of information, you can calculate it. Start by figuring out how long your twilight lasts from the times at Time and Date. You can get your latitude from Google maps or Google Earth, or by finding your location in Wikipedia. If it has an article, it will tell you the geographic coordinates. You will want the degrees latitude as a decimal fraction (instead of degrees, minutes, and seconds).

You can figure out the circumference of the circle around the Earth at your latitude using the following equation:

c=2πR(cos l)

where R is the radius of Earth (6371 km or 3959 mi.) and l is your degrees latitude. You know that there are 360° in a circle, and you know (or now know) that it takes one hour for the Earth to rotate 15°. Can you figure out how broad the terminator is in kilometers or miles?

Give it a try, and while you're on your night hike, take in the beauty of the sky and trail, but watch your step!

Thursday, August 19, 2021

When you can't see the stars...

Astronomy is a sometime thing (apologies to George Gershwin). Light pollution, haze, clouds, so many things can sabotage a night of stargazing, so what do you do when you want to see a star but can't.

Well, study the thing that blocks your view. I've been impressed with how well phone cameras can perform after the sun goes down. For instance, sunset doesn't necessarily end when the sun goes down. The sun may have set on you but the clouds above you are still in line if sight of a low, red sun.

Here are some low clouds over Centennial, Colorado about half an hour after sunset. 

Recently, we've been having some very uncharacteristic thunderstorms in the area. It's difficult to impossible to capture a lightning strike in a photograph, but a video is a different thing entirely.

Fog, smog, clouds are all interesting in their own light and they show a different face at night than they do during daylight.

Tuesday, July 20, 2021

The Foundation

That's what physics is...the foundation of science. It's at the bottom of every material and energetic process in the universe from the exotic heart of a supermassive black hole, to your car's engine, to your own metabolism. So, physics is important.

I still plan to shift my focus to chemistry and geology next year. I'm really looking forward to exploring the spectacular geology in my area. But I don't want to drop physics and astronomy, so I will continue working on the physics and astronomy LabBooks.

It will be awhile before I've finished the introductory section of the Astronomy LabBook but I've completed the first two brief, introductory sheets of the Physics LabBook and an indepth exploration of measurement, precision, points, graphing, and geometry with lots of hands on excursions. You can find it here:

The first few sheets will be concerned with the fundamental measurements and methods that physicists use to explore the world. I make sure to bring it home to do it yourself projects and survival techniques.

Like the other LabBooks, this one is a LibreOffice spreadsheet, so download and install the free LibreOffice suite before trying to view it.

Wednesday, May 19, 2021

Catch the sun

You've probably read that you can't look directly at the sun without damaging your eyes. At an approximation, take that as a fact.

It's not exactly true, though. You can actually look at the sun briefly without burning a hole in your retina. A little longer and you will temporarily wipe out the part of your retinas that the image of the sun fell on. Longer than that and that part of your retina will be permanently out of operation. 

The problem is that everyone is different. If someone tells you that they looked at the sun for three seconds without lasting effects, your eyes might be able to take only one second. And that is why I suggest that you never look directly at the sun.

Your vision is precious. Don't risk it.

The image of the sun on the light sensitive part of your camera will also destroy it in a very short time.

But there are ways to observe the sun. You can get a blurry image with little cost. It's acceptable for viewing solar eclipses but not for detailed solar observation. For that, you will have to put out some cash.

I only do the inexpensive stuff here. This is my solar observation tool kit.

The most common means of viewing the sun is with a pinhole. That's what the silver rectangle is. I cut a small square out of two pieces of card stock (index cards are perfect, and folded a piece of light weight aluminum foil over one side. In the middle of the square hole, I used a pin to punch a tiny hole in the foil. To punch the hole, I placed the foil side down on a hard surface (I used a craft cutting board but a marble table top or similar surface will work fine) and pressed a pin point against it.

Holding the pinhole over another card and using it to project the sun's image, I got the following.

It's...uh, that tiny dot in the center of the black might have to enlarge the photo. You can move the pinhole nearer and further from the card. When you move it away, the dot gets bigger. The problem is that it also gets dimmer.

A large hole will provide a larger image but it will be dimmer and fuzzier. The main problem is that light from the surrounding area will wash out any details.

I have two inexpensive (but very cool) science kits that include pinhole projects. The white box is from the ScienceWiz: Light kit. I cut a hole, about a half centimeter, into one wall of the box opposite the side that isn't there (the box only has five sides. The missing side has been replaced with wax paper.) When I aim the pinhole at the sun, the sun's image is cast onto the wax paper. The box shields the image from glare.

The hole wasn't very round so the image came out sorta whompsided. A paper punch would have given me better results. But, if you do this project, don't expect to see a lot of details. The big hole is better suited as a pinhole camera for landscapes.

I got a much nicer image by replacing the lenses from a simple refractor telescope kit (the Project STAR telescope bought from Home Science Tools) with a foil pinhole (I punched a pushpin completely through the foil to create a larger pinhole) at one end and wax paper at the other (the kit instructions tell how to build the pinhole tube). 

With a pinhole tube, you can slide the telescoping cardboard tubes in or out to sharpen the image.

You can also use telescoping mailer tubes to create a pinhole tube.

A second way to inexpensively look at the sun is to use a #14 welder filter. It cuts out more than 99% of the sun's light. Eclipse glasses (which are really inexpensive) do much the same thing. Old science kits suggest that you use a candle to coat one side of a microscope slide with soot to create a solar filter. The problem is that it's very easy to scratch away a tiny section of soot and that's all the sunlight you need to blast your retina or a camera CCD into oblivion...not a good idea.

The second photo is zoomed. Zooming with a digital camera won't give you any more details but it will make the image larger (and fuzzier).

The pinhole phenomenon produces an interesting effect during an eclipse as spaces between leaves on trees act as pinholes to cast images of the sun onto the ground.

These methods will give you great images of an eclipse. (See the blog for August 21, 2017 for images of the last total eclipse in Colorado.) For observing the sun in detail, you need something that will either project a cool image (a lens will just start fires), or a special filter. You can buy a special telescope called a sunspotter for a little over a hundred dollars. With it, you can see sunspots and flares.

You can use a sun filter (or welder filter) with a scope but the filter has to go over the objective lens and it has to cover the objective completely. You can get a sun filter for most telescopes and some binoculars. Here's my Carson telephoto lens on my smartphone with a #14 welder filter between it and the sun.

Here, you can see the sun's corona. The bubble at the upper right of the image is an artifact, but you can just see a solar flare below it. This is about the best I can do with my set up. Any sunspots would be masked by the general brilliance of the sun's image.

You can project the image if the sun through a scope but keep in mind that things (the scope's optics, the surface you project onto, whatever's under that...) will quickly heat up.

If you want to seriously get into solar observation, the sunspotter telescope is one way to go.

Another is an H alpha filter. It filters out all light except a very narrow band from the hydrogen spectrum (thus, it's name). It's expensive but it will show you incredible solar details. It will also block light pollution in urban settings.

Professional astronomers use radio, ultraviolet, and infrared telescopes (in addition to their regular telescopes) to get their solar images. For a lot of cool images of our hot sun, check out Wikipedia (

As a curious astronomy observer, you don't have to spend a lot of money to watch space and most of the inexpensive pieces of equipment are also very portable so you can easily carry them on the trail. With a little more money, you can turn astronomy into a hobby that can grow to any level.

The sun is a fascinating object to track but be safe and enjoy it.

Friday, May 7, 2021

I am a camera

Actually, I am not a camera. That was a quote from "Into the Lens", a song by Yes. You should find it on the Internet and listen to it while you read this blog.. or not.

Astrophotography is a fun hobby. To get great photos, you need to put out some substantial funds, but to get nice shots, like my shots of Venus...
You just need a phone camera, a way to connect it to a tripod, and an inexpensive telephoto lens.

You also have to have an intimate knowledge of your scope and your camera.

For any photographic work, you need to know your camera's field of view and resolution, and if you don't have this in your phone's specs, you can easily determine them like I did for my phone camera. Here's my setup.
I carried my portable podium onto the patio with a half meter ruler held up by optical bench stands (those are from an inexpensive set I bought from Home Science Tools. Great company. You could probably make your own.) Under the podium, I stretched out 20 feet of a tape measure.

On the bottom photograph above, there's a plumb bob I threw together using a random piece of plastic I had lying around. I hung it from my phone tripod clamp with a 1/4 20 wing nut and cord. I clamped that to my phone so I could tell how far away I was from the ruler using the tape measure.

To figure out the angular field of view, I stood back until the ruler filled the camera view from one side of the frame to the other. 
That was right at 2 feet (27 inches).

Next, to determine the camera's resolution, the distance at which two close objects at a specified separation can just be seen as two separate objects, I moved back until the millimeter markings on the ruler just blurred into indistinguishable marks.
That was at 28 inches.

So, why would I want an angular field of view? Many terrestrial scopes, including binoculars, give their field of view in terms of width in feet at 20 feet. That's okay when you're working at distances that can be expressed in feet, or even miles, but astronomers work in distances from astronomical units (1 AU is the average distance from Earth to the sun) to light years (a light year is about 6 billion miles) to billions of light years.

If you draw a great circle around the Earth, at any distance, it is composed of 360 degrees. The moon, as seen from Earth, has a diameter of about half a degree (we say it "subtends" an arc of 0.5 degree.) So does the sun, although the sun is much bigger. That's why the moon can block out the sun in a total eclipse. Astronomers work with arcminutes (an arcminutes is one sixtieth of a degree) and arcseconds (60 arcseconds make up an arcminute, 3600 arcseconds make up a degree). Binary stars, as seen from Earth have a separation of from 20 to less than one arcseconds.

Next...the math.

I have set up a right triangle here. The angle from one end of the ruler to the camera, back to the center of the ruler is half the angular field of view. I know the distance from the ruler to the camera (d), and I know that the half ruler is 250 millimeters long (it's a half meter ruler). I can use trigonometry to figure out the angle.

I need everything to be in millimeters, so 27 inches is 685.8 mm. The tangent of my angle is 250 mm/685.8 mm, so the half angular field of view works out to be 20° and the full field of view is 40°.

Mount Evans, pictured here, is 40 miles away. The tangent of half my view angle is the half width of my view field divided by the distance. That means the half width is equal to the tangent of half the angular field of view times the distance, or 14.6 miles. My full field of view at 40 miles is about 29.8 miles.

I figure that my measured distance to the ruler could have been off by 2 inches in either direction, so I can calculate my error by recalculating my field of view at 29 inches and 25 inches and that error turns out to be about ±3°.

I can calculate the resolution of my camera using the same method but, instead of using half the ruler, I use half a millimeter. The distance from the ruler where I can just make out millimeter markings is 31 inches or 787.4 millimeters. That gives me a resolution of 0.07° ± 0.005° . That's a far cry from being able to see binary stars as two stars, but, at least, I can see the sun and moon as a disk instead of just a point source of light.

My camera's electronic zoom does not increase resolution at all but my telephoto lens does. If I wanted to check the resolution of my camera with an optical system like a telephoto lens, binoculars, or a telescope, I wouldn't use trigonometry, I would just see if I could see a pair of stars with a known separation.

Angular field of view is a more flexible measure than width of view at a given distance, but now you know how to find your camera's angular field of view.

Friday, April 2, 2021

Blogger blogs: A little lesson

Ah, well, yes...I see..  

So, this is a lifelong learning blog in which I recount my learning experiences, and I have had a new one.

Some learning experiences are created, others just, sorta...happen to you.

I have learned that you can cut and paste images into a Blogger blog. Just don't expect them to stay there.

File it under "hoisted by my own petard". 

I discovered that I could just compose a whole blog in Google Docs and then copy the text and images over to Blogger, thus circumventing the image insert command in the Blogger editor. I started doing that at the end of 2019 and it worked well until a couple of weeks ago. Then it exploded.

It is frustrating, weird, and sort of interesting.

It seems to be chaotic. Some photos are still there. How are they different from the ones that disappeared? Computers are frustrating (or is that "fasctrating").

In Google's defense, I never saw where they suggested using cut and paste for images.

So, two years worth of photos. They're still in my photo archives. I might take a while to reinsert them, a few at a time. In the meantime, I will go back to inserting pictures via the insert command.

If you want photos from an exploded blog, drop a line and I'll be glad to send them by email.


Monday, February 8, 2021

Survey quest

Have you ever seen one? They're everywhere. They're so ubiquitous, in fact, that you might not notice them.

Survey markers.

Many show where pipes and cables are buried. Some mark property boundaries. The one pictured above is a standard survey marker placed by the National Geodetic Survey of the United States (NGS).

Each survey marker of the NGS is paired with a file in a publicly accessible database that stores a huge amount of geographic data. Other countries have their own versions of the NGS.

Geocaching is a popular pastime worldwide. People establish a container of inexpensive souvenirs for other people to find. Geocachers take an object out and leave one in its place. The fun is in the journey - the searching and finding. There are geocaching websites on the Internet. Check them out...that just might be your next passion.

Survey markers are sorta the postage stamps of geocaching and some geocaching sites have sections about survey markers. Like stamps, they all have more or less interesting backstories on file. For instance, there is a survey marker on a step in the Colorado State Capitol in Denver that shows precisely (and I mean "precisely") where a mile above sea level is.

Last fall, I used a local survey marker as a destination for a hike. I planned to use it for an activity in one of my LabBooks. I found it by using the map search engine, here:

The marker was about two miles away on the other side of nearby Interstate 25. 

The marker is on a little concrete mound on a shoulder between an urban street in the Denver Tech Center and the Interstate. There's a stake there to indicate its position.

It was a reasonable urban hike on a nice day.

If you tap (or click) the marker on the website map, you get a link to the data file.

How much information could be attached to such a little metal plate. You'd be surprised. There is position information - latitude and longitude to five decimal places of seconds, and altitude in millimeters. There's also a detailed description of the site and the buildings and streets in the area.

If you want to know your place in the world, a survey marker will tell you.

The map also gives a link to a geocaching site:

There are survey markers associated with monuments, mountain peaks and other geological points of interest, and town squares. If you think you might be interested in benchmark hunting (that's what it's called), check out this site:

Monday, December 21, 2020


I live in an extended family and as jobs and other life situations change, responsibilities shift over time. I have recently become the chief cook and bottle washer (literally) and that isn't a complaint because I really do enjoy cooking. 

I specifically enjoy cooking because I enjoy eating good food and, if I'm cooking, it lets me ensure that there will be good food. 

The problem is that, since I retired seven years ago, others have been doing the cooking. I was a little worried that I had lost my touch but, evidently, cooking is like riding a bicycle...without the pedals, of course.

A lot of the food from my first family has come to my rescue. I didn't really carry the food of my childhood with me when I started college and moved from home but, after my parents died, I found myself going back more and more.

Southern food developed in a society where people had little time away from work to deliver extravagant meals to their families and poverty often forced them to use what they produced from their own gardens or otherwise had on hand. From humble origins, a real cuisine developed.

A popular meal here centers on smother-fried meat. I didn't specify the kind of meat because pretty much whatever you excavate from your freezer will serve.

The key idea is that gravy will cover a multitude of sins. Bad cuts of meat, over cooked main dishes, left overs? Gravy is always the answer!

Smother-frying is a multi-step process.

I start with about a pound of meat for three people. If it's a big chunk like pork loin, it needs to be cut into slabs. Chicken breasts are fine whole. With a hot skillet (about 250°) with a liberal amount of oil or grease coating the bottom, I lay out the meat and sprinkle it with seasoning (Tony Chachere's seasoning is the current favorite) and a coating of all-purpose flour (I use about a half cup flour for 2 pounds of meat, then another half cup when I flip the meat ). Then, that fries for five minutes.

The flour isn't really a batter - it will make the gravy. I just want it to absorb the flavors in the pan as the meat cooks.

After five minutes covered, I flip the meat. Add a cup of water to keep the stuff in the bottom of the pan from burning to black. Charred is good, black is bad. More seasonings and most of the rest of a cup of flour goes on the meat. Cover again for five minutes.

Flip the meat and scrape up the stuff that has stuck to the bottom of the pan. Add a little more water and let it all cook covered for a couple more minutes. You'll want water and salt (I use soy sauce for the salt) on hand for the next part).

Reduce the heat to a simmer. This is the fun part where you craft the gravy.

Scrape all the stuff off the bottom of the skillet with a spatula and start adding water and, maybe, more flour until you have a lumpy gravy. This is not a place for satiny smoothness. Work out all the big lumps. Taste the gravy occasionally and add salt and other seasonings until it tastes the way you want it.

Let it simmer until you've ready to serve it and you've got a great meal.

I like this dish because you can play with it using just about any kind of meat (fish takes a delicate touch and a lighter gravy with much less thickening, in fact eggs, instead of flour makes can interesting gravy), different seasonings and thickeners, and a vast variety of sides. In the picture above, I lined up smother-fried chicken breasts with white rice and seasoned, steamed vegetables.

Smother-frying involves a good bit of style. If you try it out, you'll find yourself automatically adjusting to the amount of heat you use, how you deglaze the pan, how much and how often you add water and seasoning... it's a method you can own.

Saturday, November 21, 2020

Do you know your north?

Heh. In the Denver area, that's easy.

That's west. (See the Rockies?)

That's east. No mountains. In fact, when you top that hill, it's plains as far as you can see...all the way to the Mississippi River, 600 miles away. They don't call the Great Plains "Great" for nothing.

Facing the Rockies, north is to your right.

But why should you care?

Let's say that you're hiking somewhere other than Denver and you suddenly realize that you don't know where you are? Even if you have a map, you have to orient the map to your surroundings and the way you do that is to point north on your map (there will be a symbol pointing north just for that reason) toward geographic north.

You could just choose a direction and start walking. Surely a straight line will bring you to a road or stream or something you can follow out.

The problem there is that humans are very bad at walking in straight lines. They're much better at circles. People have a dominant side. If they're right handed, their stronger right side tends to push them to the left.

The way to walk in a straight line is to find a landmark and walk to it. When you get there, sight back to where you came from and extend that line of sight in the direction you're going, find another landmark, and walk there. Repeat.

But it's best if you have some idea of where you're going. Do you remember a road to the east of you? Is there a town somewhere to the southwest? Your reference is north.

When you face north, east is to your right, west is to your left, and south is behind you. And the sky will always tell you where north is. 

At night, Polaris, the pole star is due north (actually, it is off by about a degree but it's good enough for navigating on land.) If you know any objects in the sky, you should know Polaris, the Big Dipper, and Orion. The Big Dipper is hard to miss because it looks very much like a...well, big dipper. The two stars in the outer edge of the dipper are called the "pointer stars" because they point straight up at Polaris.

(South of the equator, Polaris australia is a very dim star, so you have to find where it should be by following the upright of the Southern Cross.)

If you find Polaris, you've found north so just walk straight toward...oh, wait, it's night. You shouldn't be walking around in a strange forest at night. Just wait until morning and, okay, where was Polaris, again?

Well, look for moss on a tree.

Eh, that's not a reliable way to find north. Moss likes sunshine and most of the sun in the Northern Hemisphere comes in from the South so, yes, mosses like southern exposures but they grow where they can. In dense forests, you can't trust them.

So, here's one.

Set up a vertical post (what astronomers call a "gnomon" - a rod used to cast a shadow or sight some object) and, at the top of its shadow, drive another rod into the ground. In about an hour, come back and place another rod at the tip of the gnomon's shadow (it will have moved). Strike a line from the gnomon halfway between the other two rods - that points north. A line from the second rod to the third points east.

The idea is that the sun rises in the east and sets in the west, and in the northern hemisphere, the sun is to the South, so the sun's shadow points north and moves from west to east. The problem is that this method depends on when you mark the shadows.

In the picture above, a line drawn from the rod at the left to the nearest rod points due north because I placed them at solar noon (not at Daylight Savings Time noon). At solar noon the sun is due South.

If you place the rods an equal time before and after noon, this method works.

Don't know what time it is? Well, start before noon and place small markers every so often at the ends of the gnomon shadow - maybe use little rocks or stick small twigs in the ground. Where the end of the shadow is closest to the gnomon - that's solar noon. Draw a line from the gnomon to that point and you have north.

If you spend a lot of time outdoors and pay attention to where the sun is, you can get to where you can just look at the sun and tell about what time it is and where north is.

Keep in mind that, in the Southern Hemisphere, you have to look for where the southern pole star would be if you could see it, and the sun will be in the north during the day.