Stargazing Basics Tips to Go

by Jim King

Learn the basics, then work on getting better

and having more fun

BARLOW LENS: This type of lens which you install in your telescope’s focuser (and then put an eyepiece into) increases the effective focal length of a telescope and magnifies its image.  A 2x Barlow doubles the focal length and the eyepiece will provide twice the power.  If you choose the eyepieces carefully, adding a Barlow can give you a much wider range of magnifications.  

BINOCULARS: High-quality binoculars should be part of every observer’s kit.  For magnification, choose 7x, 8x or 10x.  The front lenses should be at least 50 mm across.  Smaller ones don’t collect enough light.  If your budget can stand it, check into Image Stabilized (Canon, Fuginon) binoculars to avoid having to rely on the availability of a tripod.  I have the Canon 10X30s image stabilized which are a true “grab and go” accessory for astronomy, bird-watching, etc.

CIRCUMPOLAR STAR: This term describes a star that always lies above an observer’s day or season. At the equator, no star is circumpolar.  At the North or South Pole, all stars are circumpolar.  At any other latitude, a star whose declination is greater than 90 degrees minus the observer’s latitude will be circumpolar.

COLLIMATION: Owners of Newtonian or Schmidt-Cassegrain telescopes who don’t have them set up in a permanent location, should collimate their scope, or align its components, prior to each observing session.  See the telescope’s operation manual or You Tube to learn the procedure.  (I have three Schmidt-Cassegrain telescopes, none of which have ever required collimation as long as proper handling and care are exercised...properly cased, not dropped or seriously bumped).

DARK ADAPTATION: In the first 30 minutes in a dark setting, the sensitivity of our vision increases 10,000-fold, with little gain after that.  Even brief exposure to bright light temporarily reverses the gain, though how much you lose depends on how long the light is on and its intensity.  Always opt to use dim red light or similar although even red lights can temporarily lessen eye acuity.

EYE PATCH: Cover your observing eye with a patch when you start to set up, and by the time you finish, you’ll have a fully dark-adapted eye.  Then, switch the patch to your other eye so you can keep both eyes open at the eyepiece, a technique that reduces eye fatigue.  Oh, and before you use your faint red light, move the patch back to your observing eye.  Interestingly, the pirates of old wore eyepatches, not because they lost an eye, but to help them see better at night.  True story. 

FOCUS: Here’s the most important tip on the list.  Each time you put your eye to your eyepiece, and whenever you change eyepieces, refocus.  If you do not, you are wasting valuable observing time.

HORIZON: We usually define the horizon as where the celestial sphere intersects Earth at every point. Here’s the problem, most non-ocean locations don’t offer a true horizon…that is, one 90 degrees from the zenith.  Mountains, hills, buildings, trees can all obstruct your view.  Be aware that the times celestial objects rise and set will be affected by your local horizon.

INTOXICATION: Ever notice that all observing guides recommend you bring nonalcoholic beverages when you observe? The reason is simple, alcohol impairs vision.

KNOW YOUR EQUIPMENT: You just bought a new telescope.  Don’t rush to take it to a remote site.  Set it up at home first, and in the daytime.  Just be careful NOT to point it at the Sun.  Any problem you uncover in the daytime, will be one issue less you’ll have to deal with in the dark.  And if you come across an issue, at least you’ll be familiar with the scope.  The Moon is frequently available to us in broad daylight.

LIMITING MAGNITUDE: The best way to get a feel for the quality of your observing site is by measuring its limiting magnitude (L.M.).  Most observers determine LM by identifying the faintest star they can see at the zenith.  Other like to use the region around Polaris because the same stars are visible year-round.  Your telescope operating manual can give a fair approximation of the telescope’s designed L.M.

MERIDIAN: An observer should always know the position of the meridian. It’s the great circle that passes through the zenith and the celestial poles.  Find, Polaris, draw a line to the zenith, and continue south.  When an object lies on the meridian, it has reached its highest point and is best place for observing.

NEW GENERAL CATALOGUE (NGC): Most observers are familiar with at least the main Messier objects.  The NGC is a more extensive catalogue of deep-sky objects.  The original catalogue (established in the year 1888) listed 7,840 objects, with 5,386 more added later.  Get familiar with the designations, and positions of some of the most impressive NGC objects to expand your repertoire.  A few of the brighter ones to consider are NGC 457 (The Owl Cluster), NGC 869 and NGC 884 (The Double Cluster), NGC 5139 (Omega Centauri), and NGC 7293 (the Helix Nebula).

OBSERVING CHAIRS AND LADDERS: When observing, comfort is everything, and nothing says comfort like a high-quality observing chair.  Good ones have sturdy construction and padded seats and are easily adjustable.  While chairs work fine for refractors and Schmidt-Cassegrain’s, large Dobsonian-mounted scopes require a ladder.  In this case, look for ladders with wide, rubber-covered steps and a utility tray.  

POSITION ANGLE: Learn where north is when you look in your eyepiece.  Many times, observing guides will give the position angle (P.A.) of one object in relation to another, brighter object.  This angle is measured from north through east.  For a double star, it’s the line joining the primary with the companion star.

SEEING AND TRANSPARENCY: Seeing is a measure of the steadiness of the air.  Transparency is a measure of how clear the sky is.  Weather has a huge impact on both. An air mass colder than the ground will produce unsteady air, but it’s also usually dust-free.  An air mass warmer than the ground can hold lots of dust, but images will be a lot steadier.  If a cold front has just passed your site, the seeing probably won’t be good for at least 24 hours.  Seeing can be good if thin cirrus clouds are above you, except when they combined with low-level crosswinds.

SITE SELECTION: When you are looking for an ideal observing site, three things count.  First, it must be free of most light pollution. Second, the air must contain few aerosols (dust, air pollution, and water droplets), And third, it should be at an altitude between 5,000 and 8,000 feet.  Of course, perfection is illusive, but close can be good.

YOUR SPEED: Some observers spend an hour or more on a single object, endeavoring to glean every bit of detail possible.  Others take a more leisurely pace between 5 and 15 objects per hour.  Take the time to discover what observing speed works best for you and plan accordingly.  Great nights are few and far-between. 

ZOOM EYEPIECES: If your budget for observing accessories is limited, consider a zoom eyepiece.  Such an accessory will provide a range of magnifications at a cost much less than each of the individual eyepieces in its range combined.  Fortunately, the quality of today’s zoom eyepieces is much better than those of even a decade ago.

Source: Adapted from Astronomy Magazine, September 2022

Ex astris scientia, y’all



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