Observing Tips
"Uncle Bob"
Planning
Planning can enhance the success of an observing session immeasurably. It begins indoors in good light. The planisphere provides a year-round 24-hour map of the sky. A window opens onto the part of the sky visible in a given latitude range and specifically for the time of year and time of night. Use it to survey the possibilities.
You will be observing first with your own eyes, and then possibly with binoculars or a telescope. All sky objects are accessible to you, but for solar observation use an approved filter – this is not an accessory to gerryrig. Permanent eye damage can result from looking directly at the Sun, especially if the light is magnified.
The moon’s brightness can cause much eye strain and the neutral density filter and dark color filters for telescopes help solve this problem. If you are using binoculars, plan to take frequents breaks from the Moon.
Your eyes can observe almost every other type of object: meteors, comets, the stars and their colors, the open and globular clusters of stars, and even a few galaxies. Of course, a little magnification can yield more brightness and detail. Be sure to set some observing goals for your session in order to make a good choice of instrument. A good pair of binoculars can access every type of object, even some double stars. Telescopes are best for seeing details, but they can limit you in a few ways. For example, you would not use any aid if you were going out to see meteors or man-made satellites. You would not use a powerful telescope to see the larger star clusters in full because the field of view would be too narrow.
Field of view is measured in degrees and describes the area of the sky seen in a single view. The most common binoculars have a field of 5 to 15 degrees. The Big Dipper is 25º long, so binoculars would show but one or two of its stars at one time. Backyard telescopes can range between a half and 3 degrees of field, and most are accompanied with finder scopes in the binocular field range.
Once you have picked some objects, consult a star chart to see how large they are in degrees, and also note their brightness and angular separation from prominent objects. Make a recipe for how you will use the sky neighborhood to find your object. Sometimes these recipes call for star-hopping, i.e., making a trail from one star to the next and on to your goal. One helpful accessory for charts can be a homemade item. Twist pieces of wire into circles which match your instruments’ fields of view on the charts. You will then have a framed picture of what you will see around your target.
Dressing
Observing burns calories but creates little heat. You should dress as if it is 20º colder than the forecasted temperature, and be sure to factor in wind chill. For cold nights, a ski mask and ski pants might be called for. Heavy socks will help as well as an old scrap of carpet on the ground where you will stand. A hammock or deck chair and a sleeping bag can add warmth and reduce neck strain. You do not want to be cold, hungry, tired, or tense when trying to find faint objects.
Equipment
Pencils, notebook and sketching paper will preserve those exciting moments when memory has long since failed. Be sure to note non-sky events that can help you pinpoint the time. An observing journal can be an effective diary. Have a watch handy to record the time of observation. Also, make note of the position, appearance of the objects, and your observing conditions at the time. Have a red light to read charts and sketch by. Red plastic covering an ordinary flashlight will work.
More About Logging the Event
1. Position. If you have found the North Star
using the top edge of the Dipper to point you, then you can use other compass
directions to report the objects left-right position. What about elevation?
If you extend your right arm, fingers together and pointing to the left (a
good stretching exercise for the shoulder), thumb beside the palm (not stuck
out and not tucked), you will be looking at 10 degrees of elevation across
thumb and palm. To test this, begin at the horizon and leap frog right and
left palms (giving the other shoulder some stretch too) and see if nine palms
gets you to the "top" of the sky, called the zenith at 90 degrees
elevation.
Example position: north star is N and 45 degrees altitude.By the way, the
opening of the Dipper is about 10 degrees across.
2. Time
3. Brightness (compared to a known star)
4. Color
5. Motion (speed and direction of satellites, meteors, etc.)
6. Drawing. If you find one of those smudgy objects in binoculars
you could make a pencil sketch.
That'll do. My own log dating back to 1993 is dearly prized not just for a record, but in fixing other happenings in my life. Start modestly (scrap paper?) and if you "get into it," find a notebook to use.
Binoculars [link to an article on the details of binoculars]
Telescopes
Cleaning
It's best NOT to clean, unless you swab with camel hair brush using household alcohol. Don't wipe the glass.
The two main telescope types are refractors and reflectors. Reflectors use internal mirrors to lengthen the light path and increase the focal distance, all while shortening the instrument. This enables reflectors to have larger apertures (the size of the front lens) and collect more light for seeing fainter objects. Reflectors have a mirror in the center of the front lens.
Refractors use lenses and are said to be better for detailed planetary observing. Of course, some experts dispute any and all opinions of this nature.
Solar observing. Do NOT look at the Sun. Do NOT point a reflecting telescope at the Sun. With its internal reflections it could be destroyed and blind you in the process. Reflectors must have an approved, fitted filter. A small refracting telescope can be pointed at the Sun and project an image onto white paper.
As with binoculars, good telescopes have quality glass and coatings on the lenses for enhanced transmission of light. Some telescopes have one or two motors that can track an object – keep up with its apparent motion across the sky. Some have computer chips that assist in aligning the scope and finding objects stored in a database.
Accessories
Serious observers come to a site armed with palettes of eyepieces and filters. A change of eyepiece can adjust the magnification and field of view. Filters can enhance details of certain objects, and others can help screen out unwanted light and atmospheric interference.
Location
Atmospheric conditions can greatly affect your limiting magnitude – the dimmest objects you can see. Getting even three blocks away from the center of town can bring a comet into view. Rural sites are naturally the best – pun intended – but local lights such as road traffic and streetlights, because they are nearer, can be even more of a problem. A friendly neighbor may be willing to douse the porch light after a certain hour. The power company may be willing to shield a streetlight shining in your direction.
Lacking this type of cooperation, you can take other steps. Find a spot where tree trunks and branches block light. Create a shadowy site by using old cloths and blankets for curtains and screens.
Consider portability when making site plans. You will not want to reposition a telescope, so find an open area or limit your goals. Binoculars and a deck chair rate high in portability.
Technique
As with the weather in general, there is no controlling sky conditions at night. Partly cloudy can mean mostly indiscernible to a beginner. A few clouds can be helpful in sweeping hazy mist from the air. Some light pollution can help a beginner by blocking the thousands of objects, thereby accenting the main tableau. Perfectly clear skies can be problematic. If the day has been warm, convection currents can make your seeing wobbly.
Patience then is the watchword. Be patient with your plan. You may have to wait until conditions change to see that galaxy. It is possible that it will not appear on a given night due to haze or sky brightness. Be persistent by noting the problem and planning to have another go in the future. Be patient while you develop your night vision which can take up to 20 minutes. Keep one or both eyes closed if white light should enter your view. Alcohol use and low blood sugar are known to interfere with night vision too.
If an object seems to peek at you and then hide, try using averted vision. Look slightly above, below or to one side of the suspected location. Don’t stray too far because there is also a blind spot caused by the optic nerve connection with the retina.
Objects set in the west, so you would often make a west to east plan to catch those objects for which there is less time. Be patient also in spending time with each object. As the seeing gets better you will get more details such as features and colors.
Get the big picture first. Use your eyes to spot binocular candidates. Use binoculars or the finder scope to find telescope candidates.
Give Back
Invite the neighbors and especially any children to have a look. They want to know what you’re up to out there. Host a party for events like eclipses and comets. Invite other to bring their equipment and star stories, and you just might learn more yourself.
Enjoy!
Sources: Deep-Sky Objects for Binoculars by John Kozak. Backyard Astronomy by Alan MacRobert.
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