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.