Wednesday, November 28, 2012

Cloudy Skies Astronomy: Radio

Each year the clouds move in during fall, before the clear, cold nights of winter. Each year I lay aside active astronomy for reading and other pursuits. But, I also think about picking up radio astronomy to "see" through the clouds.

I haven't been a victim of the clouds every year. For three years when I was a teen, I actually did some radio astronomy. I had a short wave radio receiver, and I built new antennas for it each year. I started with a simple wire-wound antenna, using magnet wire wrapped around a fiberglass pole from a bicycle safety flag. It picked up the sound of electrical discharges between Jupiter and Io. The next year I made a simple dipole, which was a bit more directional, especially since the Earth and my apartment building blocked signals from two directions pretty well. But the apex of my experiments was the same dipole the next year.

I trimmed its length to let it catch the frequencies I wanted more precisely in my high school's electronics lab. I didn't have any of the tools for that at home. Then I made a rickety "corner reflector" for it out of chicken wire and 2x2 lumber.

With it I was able to catch the sounds of Jupiter and some other strong astronomical radio sources much more clearly. The background static was much reduced, and there was more detail to the sound, in fact, it started to sound like sounds rather than lightning discharges on an AM radio. I used this same get-up to catch some radio noises from Earth's own atmosphere, too.

The results were enough that I've stayed interested in doing radio astronomy ever since, though I haven't done anything practical about it. But I sure think about it, every time the clouds move in.

simple satellite dish antenna
If you're more motivated than I am to actually do something, here are some links that may interest you:

Some great projects using satellite TV dishes as antennas:
NRAO Information for Amateur Radio Astronomers

Jupiter and Other Simple Starter Projects:
Detect Radio Emissions from Jupiter
Small Amateur Radio Telescope

More projects from the U.K.:
UK Amateur Radio Astronomy

A book, with some thick crunchy bits, that I recall reading back when I was getting started:
Radio Astronomy for Amateurs

And more fun stuff:
Radio Astronomy Projects
Radiosky Radio Astronomy Projects

This year I'll probably be distracted by "chasing DX" in amateur radio. I got my license last year, and I've only recently made my first contacts on the "HF" bands (short wave radio, basically.) But I may see if I can tune in Jupiter along the way.

Friday, August 10, 2012

How Big is a Constellation

One of the most difficult things many people find in stargazing is learning the constellations. Most people can find Orion, and the "Big Dipper" here in the northern hemisphere, which pretty well passes for Ursa Major (the Big Bear.)

But others are more difficult.

Most constellations are not as well defined as the most popular ones. The three stars of Orion's belt are not only bright, but they're all about the same brightness. Which makes them easier to pick out. Then, finding the other bright stars of the body isn't that hard. Most folks don't bother picking out the stars of the head, shield, and so on.

The Big Dipper is an asterism (sort of a non-official constellation, the words asterism and constellation mean the same thing but they're used differently.) It is made up of seven stars of roughly equal brightness that stand out from the background of the sky around them.

But other constellations don't have nice patterns like this, with groups of stars of roughly equal brightness that are also brighter than other stars in the area, and with a nice fairly dark buffer space between them and the next constellation over.

Another thing that makes it hard to find constellations, even when you use a star chart, is having a sense of how large they appear in the sky.

Some are very large and spread out. Scorpius has a tail that stretches off across the sky. Ophiuschus, the Snake Handler, covers a large area next to Scorpius, along with the Snake he's holding. But the Fox and the Arrow are small.

Start With What You Know

Before wandering too far out into unfamiliar territory, it usually helps to start with the constellations you know. That way, you already have a sense of where something is in the sky, and a general idea of what its boundaries are. Knowing more there can help, too. If there is a constellation you already know, compare the version of it you recognise in the sky with the version of it on the star charts. Are there large parts of it you aren't counting in when you see it? Where does it begin and end?

Then, starting there, and considering the orientation (which changes over time), can you find some other constellation next to it from the chart?

If you've already taught yourself to find the legs of the Big Bear coming off the Big Dipper, and the nose of the bear, then you're prepared to find the Hunting Dogs, a pair of stars beneath the curve of the Big Bear's tail. It's not much of a constellation, just a pair of stars, visually, but it is another constellation.

Likewise, knowing both the Big Dipper and the Little Dipper, there's that line of stars running along between them. Those belong to Draco, the Dragon.

Further south, once you've found the limits of Orion's limbs, you can easily find the Rabbit beneath his feet. And the Big Dog to one side of him, with the bright Dog Star, Sirius, in it.

Pushing out your knowledge step-by-step in this way is a good way to learn constellations, because you can learn how to locate them again later, in a month or two, when the position of the constellations in the sky has changed.

Further Afield

There are a few constellations that look like what they're named for. Scorpius is one of them. The bright red star Antares makes it easy to pick out in a July/August sky, with the head and claws nearby in a nearly straight line of stars that, while not all that bright, are easy to associate with each other because they're about the same brightness.

From those, the Scorpion runs back through bright red-orange Antares then sweeps around in a long fish hook shape with a sort of barb on the end. (This constellation is Maui's Fish Hook to the Pacific Islanders.) A constellation that looks like its name, with a bright, distinctive star in it makes a good starting point when not working off a familiar constellation's side.

Then, once it is learned, other nearby constellations can be learned.

The Power of Asterisms

Just as the Big Dipper isn't an official constellation, but just a part of the Big Bear, there are other asterisms in the sky. Asterisms are more commonly named for what they look like than the traditional constellations. And many of them make up enough of the actual constellation they're part of that finding the asterism is about as good as saying you've found the constellation itself.

The Teapot is an asterism that occupies the main part of Sagittarius, the Archer. The Teapot shape is not hard to see once it "pops" for you. If you hold your hand out at arm's length but bend it so that it's at about a right angle to your arm, it will about cover the area of the Teapot. The Teapot lives behind the tail of the Scorpion.

It has a narrow right triangle as a spout, with the cloudiness of the Milky Way looking like steam coming from the spout. The body is a large trapezoid, which shares one side with the spout. On top (it's upside-down in the southern hemisphere) is a triangle of stars that's just a bit flat of an equilateral triangle which forms the lid of the Teapot. Finally, the handle is another trapezoid which is short and wide, with its bottom the side of the body that's opposite the spout.

If you're in mid-northern latitudes it will be in the south near the horizon during summer.

There are other asterisms like the Summer and Winter Triangles (the names are northern hemisphere centric) where each of the stars in the triangle is in a different constellation. By learning to find these, you get a foothold into three constellations apiece!

The Winter Triangle has a star in Orion, the other stars are in the Big Dog (Sirius, the brightest star) and the Little Dog (Procyon, the dimmest star in the Triangle.)

The Summer Triangle has a star in the Harp, the Swan, and the Eagle. Vega, in the Harp, is the brightest star. Deneb is a middling-bright star in the Swan, at the tail of the constellation (another constellation that has a resemblance to its name.) Altair is a bright yellow star in the Eagle. It forms one end of a pair of much smaller triangles that make up the wings of the Eagle.

Looking Gets You There

It's not easy to learn your way around, unless you have somebody who's patient, already knows their way around, and there's a green laser pointer for them to use. Even at that, once the sky moves over the course of a few weeks, you will need to get re-oriented. But once you take the time to learn on your own, or through a guide, you will be able to star expanding on what you know quickly.

Just as it's easier to find your way to more places around town, the more places you already know and can use as waypoints, you can find your way around more of the sky for each constellation you add to your personal list.

Pretty soon the individual ones you know that are away from each other start growing into ones you know that run into other groups of constellations you know. Then you're looking at the areas in the middle of the constellations you know and wondering what those stars are. Whole sections of the sky become familiar.

Learning the constellations is satisfying and enjoyable in and of itself. I still spend most of my time under the sky with no telescope or binoculars or other "distractions". But the side benefit is that once you do take out an instrument, you can now easily find many items to look at if you know at least a handful of the current constellations in the sky. Some of the best things to look at are placed in easy to aim at places in the constellations. Or, if you have a computerized telescope, you can more easily and more surely give it its guide stars to get its computer started off.

Wednesday, July 11, 2012

Hot Summer Solar Observation

Our community holds a celebration each year to one side or the other of the Fourth of July. We have a street fair, dachshund races, parade, and, usually, fireworks. Lots of locals like it because it lets them extend their Fourth of July celebration a bit and get in some extra fireworks each year.

Don Machholz organizes the local astronomers to take part in the street fair, where we take out our telescopes and show off the sky, as much as we are able, to the local community. We enjoy sharing our hobby, as well as letting them know about the other events we have going on.

Each year we have several solar telescopes out, as well as viewing planets in the daytime when the conditions are right.

Last year we weren't able to attend, but the year before that we were there, showing the sun and explaining to people that usually there are things to see there other than a featureless circle. But a featureless circle was about all we had to show. There was a bit of unimpressive detail through the H-alpha filters, but chances are most of the attendees that looked didn't get so far as noticing it.

This year was a great change for the better. There were sunspots, and prominences. Sunspots are nice since they show up in an ordinary telescope with a solar filter. We had a scope with a solar filter, plus a solar projection screen that both showed the sunspots very nicely. Viewers compared them to the islands of Hawaii.

Through the H-alpha filters there were a bunch of prominences around the edge of the Sun. Solar flares, if you will. They change with time, each lasting several hours or longer and changing their appearance over that time.

Why the Difference?

A normal solar filter shows all the different visible frequencies of light. All it does is cut the amount of light down to a level where it doesn't damage our eyes or the telescope. It's what we'd see if we could stand to look straight at the Sun and still make out any detail. Plus the telescope provides magnification that makes it look larger so that we can pick out small details more easily.

An H-alpha filter is a filter that only lets through one wavelength of light, the light emitted by one type of ionized hydrogen (that's where the "H" in H-alpha comes from, H is the symbol for hydrogen). This light is in the red wavelength for us, so the image becomes a "red and white" (as opposed to black and white) monochrome image.

This clears out other light frequencies that smear out or otherwise hide a lot of interesting detail on the Sun. In H-alpha light we can see the magnetic cells of the Sun. These cells are not like the cells in our bodies, the word cell originally meant "chamber" so it got used wherever early scientists saw things divided up into little "rooms" or "chambers".

It also allows us to see the energetic material being ejected, and pulled back into the Sun. Normally the other light hides these flares and loops and other prominences. But in H-alpha light, the other light is blocked out, allowing us to see these interesting solar features.

A Good Show, Again

So now we have a good show on the Sun again. This is likely to be the case for at least the next couple of years. Usually there are only one or two years out of each solar cycle (an 11 or 22 year period, depending on how you look at it) where the Sun isn't putting on a show. And the quiet period we're coming out of was far quieter and longer than any other I've ever experienced.

Which is nice. It's a lot easier to get people interested in what's going on "up there" when you've got something interesting to show them.

Wednesday, June 6, 2012

Transits of Venus

Hopefully you had the chance to see the transit of Venus yesterday (5th or 6th of June, depending on where you were). A transit, in astronomy, is when one body (usually a planet) passes between another body and the Sun. In this case, the planet Venus was directly between the Earth and the Sun. Another example might be when the planet Earth goes directly between Mars and the Sun. This would be a transit of Earth to the rovers on Mars.

Observing Venus

Image of Venus Transit of the Sun
Projected Image of Venus Transit from a Telescope run by George Robinson at the Auburn Dam Overlook in California.

Here on Earth we only have two planets to come between us and the Sun, Venus and Mercury. The Moon comes between us and the Sun, too, and those are solar eclipses, an even very similar to a transit (it wouldn't be totally inappropriate to call it a Lunar transit.)

Why is it Special?
You'd think this would happen all the time. After all, since Venus and Mercury are within the orbit of the Earth, and orbit the Sun in less time than we do, it seems like they'd always be crossing between us and the Sun. The thing is, those planets have orbits that aren't perfectly flat compared to ours. If their orbits were flat compared to the Earth's, then we would see them cross the face of the Sun every time they were at "inferior conjunction", that is, as close to us as they get in their orbit. ("Superior conjunction" is when they're on the far side of the Sun from us.)

But their orbits are tilted. That means that they need to be in a part of their orbit that is in line with our orbit at the same time that they are at inferior conjunction. With planet Mercury, this happens a bit more frequently than once every ten years or so. Since Mercury's orbital time is so much shorter than our own, there are many more opportunities for things to line up like this than with Venus.

Observing Mercury

With Venus, this sort of line-up only occurs a couple of times over the course of a bit over a century. For these last two occasions, those times were separated by eight years, leaving 105 years until the next line-up.

How It Looked
Yesterday was the first transit of Venus I've seen. I missed the last one because I wasn't in a position to travel at the time it occurred. I've seen transits of Mercury, so I thought I knew pretty well what to expect. I expected pretty much the same thing, with Venus a bit larger against the surface of the Sun.

In fact, it was a lot different. For one thing, Venus was a lot larger against the Sun than I expected. It was also a much crisper image, sharply defined at the edges, compared to Mercury. Mercury looked kind of fuzzy, like heat waves were around the edges. Venus was large enough that the edges didn't look this way.

We got to see it through several different telescopes, including two with H-alpha filters that let you see the prominences and solar flares on the Sun. One clever set-up from our friend Larry had a pair of binoculars rubber-banded to a piece of two by four lumber, with a cardboard sun screen, and the image from one of the two binocular lenses projected onto a paper plate at the other end of the two by four. The assembly was supported by the rungs of an overturned stool, which could be turned several ways to get different heights.
Simple Solar Observing Set Up, Viewing Venus transit.
Larry, the master of laid-back astronomy, brought this portable solar observatory along with his 8" Dobsonian telescope.

As much as I enjoyed looking at various magnified images, I was most impressed by looking at the Sun directly through a pair of solar filter glasses. The circle of Venus was easy to pick out (Mercury isn't), and it looked a bit eerie just hanging there in the sky in front of the Sun.

It will be a long time until we can see another transit of Venus on Earth (105 years), but there will be a transit of Mercury in 2016, and spaceflight offers more opportunities for viewing transits off of Earth. Hopefully by the time of the next Venus transit, viewing transits of the planets won't be limited to the Earth and low Earth orbit.

A good article on why transits happen as infrequently as they do is at Sky and Telescope.

Saturday, April 14, 2012

Stargazing: Looking to See

Whether you're using your eyes or a telescope or binoculars, it takes time to see everything you can see.

To see the most, pick details out of faint contrast, or simply enjoy the view takes enough time to relax a bit and soak it in.

That means you have to be able to spend some time doing it. Which is not possible if you're uncomfortable, you or any instruments aren't stable, and if you just don't take the time.

There'll be more to see, and enjoy, in the sky if you give yourself the things you need. Time, comfortable clothing, a good, safe place to observe, well-chosen instruments with the right accessories for basic use, a place to stand, darkness.

It sounds obvious, but I know I've talked myself out of one or more of these at various occasions. I doubt I'm alone.

Dark skies and good seeing.

Tuesday, March 6, 2012

Seeing Mars in 2012

We're near our opposition with Mars as I write this (March 2012), an event that comes every 26 month, approximately. This year, we're going to have a Mars in our sky at night for many months:

  • March: up all night. Size: 13 to 14 arc seconds. Brightness: magnitude -1.0!

  • April: up till about 3:30am. Size: 10 to 13 arc seconds. Brightness: magnitude -0.35!

  • May: up till about 2am. Size: about 9 arc seconds. Brightness: magnitude 0.26.

  • June: up till about midnight. Size: about 7 arc seconds. Brightness: magnitude 0.7.

  • July: up till about 11pm. Size: about 6 arc seconds. Brightness: magnitude 1.

As you can see, Mars will be bright and fairly good sized for much of the year. However, in July Mars will be less than half the size it is in March. That means it will take over twice the magnification to get a comparable level of detail. But it will be dimmer, too. So the closer to the opposition you view, the better view you'll get. The fact is, magnification will not make up for the smaller size of Mars.

But Mars will still be putting on a good show, even this summer when it will be nice and warm out at night.


Tuesday, January 24, 2012

Observing Mars

Mars is getting close to its "opposition". That's the best time to observe Mars, generally (depending on conditions otherwise.) That's because that's when Mars is closest to Earth, and it is its brightest.

Image by amateur astronomer Arnomane of Wikimedia
Image by Arnomane

That also means that Mars is at its largest, as viewed from Earth. Oppositions occur roughly once every two years. This time, Mars will be about 13.9 arcseconds across, at a distance about 1.66 times the distance to the Sun. For comparison, the Moon is about half a degree across, or just about 30 arcminutes. Each arc minute is sixty arc seconds. That means that the Moon is about 1800 arcseconds across.

The Moon is large enough to see a fair amount of detail by eye. But to our eyes, Mars appears only as a bright dot, even at its largest. The minimum angular resolution of the human eye is about 1 arc minute, or 60 arc seconds. Mars would have to be over four times larger for us to see it as anything other than a dot by eye. It certainly never gets as large as the Moon! This is known as the Mars Hoax, an internet hoax that's been going around, and around, and around on the internet for about nine years now. It just can't look that big!

Make It Bigger

Since we can't see a lot of detail by eye, we use magnification to see the detail of Mars's surface. At the low magnifications of ordinary binoculars (7x to 20x), Mars shows as a small disk, but little or no detail is visible. A stable mount and higher levels of magnification are needed, which means that a telescope is the best instrument for observing Mars.

Mars will begin to show details at about 35-50 powers of magnification. This is low magnification for your telescope. At this level large things like the polar ice caps and Syrtis Major (pronounced like "Sir Tiss Major"), a large dark area on Mar's surface, become visible. To see more details requires increased magnification.

How much magnification you can use will depend on the observing conditions, the quality of your scope's mount and tracking, and your experience in astronomical observation. Mars is a good object to learn with. It's bright, it has both strong and subtle details. If you want to get good at using higher powers (over about 150-200x) on your telescope, this is a great opportunity.

For myself, I do my detailed observation at about 350-400x. At this level I find I can get the most detail with my 8" Newtonian telescope without it being a strain to track Mars with my scope, or having to break off my observation too often. Larger telescopes, and very well made refractors with good mounts will be able to use higher powers, but for most observers with little high power experience, anything over about 200x will be challenging.

Now in Living Color!

To tease out the finest details of Mars, it can be very beneficial to use colored filters. I have two sets of colored filters that I use for general observation. Dim objects don't work well with filters because the filter cuts off too much light to leave a bright enough image to see. Fortunately, Mars is quite bright.

I observe Mars with all the different colors of filter, but I find the red and yellow color filters to bring out the most unique detail. A blue filter is often worth observing with, it brings out polar caps and clouds on Mars. Yellow and orange filters bring out details, usually better than a red filter.

There are no hard and fast rules I've found in my own observation of Mars with colored filters. Different viewing conditions and different seasons on Mars each have an effect on what will be seen. So I usually cycle through all of them in an evening, then go back to those that brought out the most unique detail.

Take a Picture, It'll Last Longer

To really teach yourself to see detail, try doing sketches of Mars at the eyepiece. I draw several circles on a sheet of paper ahead of time for the outline of the planet (or just print out a sheet with circles about 2" in diameter on it), then sketch in basic light and dark areas with a normal pencil.

I then take notes of the time, date, magnification, and any filters that I am using. I make sketches with each of the different filters that I find work well on Mars during that observing session.

When I'm observing without a filter, I make notes on the colors of the details and try to fix them in my mind. Later, when I'm inside with light, I color in areas of my sketch with colored pencils to try to capture the colors, or color differences, that I saw on Mars.

Drawing Mars really helps you to learn to see the details on Mars. It also gives you a personal record of what you saw. You can go to the internet with the time that you saw Mars, or to your favorite astronomy program, and look up Mars's orientation at the time you drew it. Compare what you find with what you drew. It will never look the same, but you can see a match between different parts of your drawing and the image of Mars as it was when you drew it. Going back later, you may see other details that you didn't capture in your drawing.

At which point it's time to start another drawing. :)

Saturday, January 14, 2012

Cold Weather Astronomy: Be Prepared!

In my prior article I discussed ways of staying warm and safe while observing in the cold by controlling your location and taking advantage of what's nearby. In this article I'll discuss personal preparation and protection from the cold.

Fashion Sense and Sensibility

Obviously clothing is an important part of staying warm when out stargazing in winter. Having the right clothes for the conditions is critical. When it's really cold, it's not something you can fake easily with substitutions. Proper winter wear that protects both your core temperature and your extremities is critical.

Humidity Good and Bad

Even though the humidity high in the sky is very low, thanks to the cold conditions, the humidity levels at ground level can be quite different. If it's at all damp where you are, this can make it feel far colder than the temperature would suggest. Also, as the evening cools this dampness can condense on you and freeze as well. So any clothing used must protect against moisture.

While humidity outside your clothes can be a problem, inside your clothing it's part of keeping yourself warm. Clothing that helps trap your body's moisture to some degree helps keep you warm. The colder it is, the more your clothing should confine the moisture.

The Layered Look

Layers of clothing are important, both to provide redundant levels of protection from the cold and to serve different purposes. Clothing worn near the skin should be porous and absorbent to keep moisture from collecting on the skin, which can chill. It also allows the warm air trapped within your outer clothing to circulate some to better distribute your body's heat.

The next layer out should be chosen for warmth, and should also breath some. Wools and acrylics are good choices, as they will keep you warm no matter what the level of moisture.

The outer layer should prevent wind from getting in and your body's heat and moisture from getting out.

Easily Freezable Bits
Hands, feet, ears, and other outer parts of your body deserve special attention. They freeze easily, and are easier to forget when a particularly nice bit of galactic detail swims into view.

Heated socks and gloves are available, and heated hats. Some use batteries and heating elements, others use chemical packs to generate warmth. In my case I've found aluminized clothing to work just as well. I have aluminized socks and glove liners that I wear in cold weather. They work so well they literally feel as if they are electrically heated.

For example, I usually wear the following on my feet:
  • Inner cotton socks

  • Acrylic knee-high socks

  • Aluminized socks

  • Outer wool or thick cotton socks

I have a loose pair of older leather boots that I wear in winter to accommodate these layers of socks.

On my head I wear a balaclava under a heavy winter hat.

On my hands I wear a pair of cotton-lined aluminized gloves, with a pair of leather "police inspection" gloves outside of them. These aren't quite enough to protect my hands on the coldest nights, but I use these because it still leaves me enough dexterity to handle eyepieces and focusers. I put my hands inside heavy pockets when I'm not actually handling things, or use an outer pair of heavy mittens if I'm not going to use the pockets or if the pockets just don't stay warm enough.

Internal Preparation

Before going out into the cold, it's important to be well fed. Don't go out hungry, it leaves your body with insufficient reserves to keep you warm, and keep you alert enough to notice if you're getting too cold to be safe.

I usually plan a warm meal with a warm drink before going out. I also keep something warm to drink, and a high calorie snack available for observing breaks. If at all possible, these breaks should be taken in a warm place.

Breaks and Self-Inspections
Plan to have breaks in your observing sessions. They should be long enough to let you warm up completely. You need to be able to tell if parts of you are getting too cold, or if you're having trouble making decisions clearly. I do a bit of observation logging during my warm-up sessions to give me something to do while warming.

When outside, and when inside, perform a self-inspection to see if any part of yourself is getting cold and numb. Frostbite is not a necessary part of astronomy. Check your fingers and toes for flexibility and feeling. Check your ears, nose, chin, scalp, elbows and knees. Poke your calves and forearms while you're at it. Blink your eyes and make sure any cloudiness blinks away. Touch any exposed skin to make sure it's still there.

Two Ways to Err
It's possible to make mistakes in either of two ways: being too gung-ho and ending up regretting an observing session that goes too long or that you get too cold. It's also possible to miss out on some of the best observing time of the year by being too timid and hiding from the cold when the proper location and dress would be all it takes to have an enjoyable time under the sky.

Don't miss out on winter observing, and don't over-do it, either!

Plus, if you have any personal tips or tricks you use, please share them in the comments.

Saturday, January 7, 2012

Keeping Warm When Observing in Winter

Winter skies can be some of the best of the year. But it's hard to enjoy them if you're not safe and comfortable while observing. Cold air may being doing something wonderful for the skies above, but there are lowly land-level things to take into consideration.

Losing Sky to Gain Warmth
Where you observe can have a lot of effect on the conditions. Open areas far from buildings and trees are the best for views of the sky, but they are usually the coldest as well. Ground level temperatures at night are strongly affected by radiation of heat from the ground. When the area has a clear view of the sky, it radiates its daytime heat more readily into the sky, cooling more and faster than if it has partial cover.

If it's just plain too cold to enjoy the sky from a completely open area, observing the sky from one or more sites that have some partial cover can save the evening. It can be several degrees warmer in a location that has partial tree cover. Buildings keep the areas immediately next to them warmer as well. If you are viewing in a direction away from the building, any air currents caused by heat coming off the top if the building can be avoided.

By choosing partially covered locations well, you can move from place to place and be able to observe all or most of the sky without being quite so cold.

Cover the Cold Ground
Observing atop a non-porous ground cover helps significantly as well. A tarp or sheet of painter's plastic makes a good ground cover. Something else thrown on top of the ground cover will help keep the site even warmer. An old blanket, chunk of carpet, or some other form of insulating material on top of a ground cover will help make the observing site far more comfortable.

If there is any wind, some form of wind block will obviously be helpful to staying warmer. For foliage and sizable structures, you'll usually get the best protection on the downwind side of it. For smaller or erected wind breaks, the best protection may be on the downwind side but in many cases will be on the upwind side. In these instances a dead zone forms in the upwind area, whereas the downwind side may actually be colder due to air flow caused by the low pressure area formed on the downwind side. Be prepared to try both. This can also occur with some building layouts, but is more common with small wind screens, fences, and the like.

Slippery Slopes
Sloping ground can also be colder than flat areas. Convection along the sloping surface can make for a drifting draft that chills astronomers. At my prior home we lived on a slope just beneath a ridge line. Our weather was far colder than many other places at our elevation. We would have snow at times when the properties around us were clear. Our location gave us a great view of the sky, but it was colder.

In one corner of our property there was a dell with less of a view of the sky, but warmer air tended to pool there for some reason (I'd have expected it to be colder.) But I noticed that snow appeared there later than anywhere else nearby. Once snow got in there it stayed later than anywhere around because it received little sunlight. But at night, it was one of the warmest places to be, thanks to low airflow, partial tree cover, and a thick bed of leaves on the ground.

It's also important to be in a safe place to stand and move around a bit in the dark. Our present property has a steep section above a cut. It happens to give the best views to the north and east, but most of it isn't safe to traverse at night without light and extreme care. For this reason, I avoid it. Falls and injuries are a bad way to end an observing session. And it doesn't get you any warmer.

Warm Up Shack
Having a nearby location where you can take breaks from observing and warm up is a good idea. My number one observing location is at home, but I also travel to nearby locations that give a better view than my home. At the very least, I have my car as a place to go for breaks. I keep both a wool blanket or sleeping bag and a space blanket on hand. I run the engine for the heater while inside, and put a piece of cardboard on the dash to block the lights to preserve my night vision.

I keep some high calorie snacks in there, and a thermos of something warm to drink when I've though ahead that far (boy, I regret it when I don't!)

A car isn't the best warm-up shack, and a club site or other prepared observing location can have a dark warm-up room that allows you to duck in for a while to warm up, count your appendages, and generally decide whether to continue your time under the sky in warmth and comfort without having to wait half an hour for your night vision to fully return just because you wanted to get in out of the cold for a bit.

At home, I work with my family to choose a door I can go in and out of to a darkened area. That makes it easier for me to come in every so often without having my night vision ruined every time I do. Usually I keep my log and a red LED light there, I'll update my log while I'm warming up and possibly think of some more things I can look at if I go back out.

Having something to do when I first come in makes it easier for me to wait the time it takes to get warm enough to make a reasonable decision about whether I should go back out, and to keep me from rushing back out before I'm really completely warmed up. Not being able to feel your feet isn't a good sign, but it's one I've missed at times when I didn't make sure I got warmed up properly before going back out (fortunately the warming was enough that I did get sharp pains about ten minutes after going back out, rather than just numbness. That hint I did catch!)

Prepare Yourself

In the next article I'll discuss what you can do in the way of clothing and self-preparation to make winter observing more enjoyable.

Sunday, January 1, 2012

Winter Observing

This time of year is winter for us in the northern hemisphere. It's one of my favorite times for observing. Both with telescopes and with my eyes or binoculars. Even if it's nothing more than lingering in the driveway to enjoy the sky for a few minutes after a drive home, the clarity of the sky makes the stars stand out with the best contrast of any time of the year.

Winter brings cold, but on clear nights that cold makes the sky especially clear. The upper level cold freezes out moisture in the air. It's a perfect time of year for looking at faint fuzzies. If you have a smaller instrument, this is a great time to see things that are fainter than you can normally expect to find when the humidity is higher.

I have started many of my personal observing programs during this time of year, including seeing how many galaxies I could see with 7x35 binoculars, learning my way around the deep sky north of 70 degrees with a 75mm reflector, and seeing how close of doubles I could pick out by eye. The sharp appearance of the sky makes winter the perfect time to start new observing objectives.

With larger instruments, this is still a good time to view objects that are challenging, or to see more detail in familiar objects, like picking out more detail in galaxies.

Whether you're using your eyes or a light bucket, now is the perfect time to get out and enjoy sharp, high contrast skies. While the clouds are away, let the cold air freeze out the atmospheric humidity so that you can get the best views.

Stay warm with layered clothing, good socks, and good gloves.