15 THINGS STARGAZ­ERS SHOULD KNOW

Learn­ing astronomy from books is fine, but noth­ing beats what you learn from ex­pe­ri­ence.

Sky at Night Magazine - - CONTENTS - writes Jamie Carter

There’s an ‘ob­serv­ing win­dow’ each month

Bright moon­light is a big light pol­luter, so it pays to keep track of the Moon’s move­ments and phases. From about four days af­ter new Moon, our lu­nar neigh­bour grows from a slim cres­cent to a bright orb that blots out stars right up un­til about six days af­ter full Moon, af­ter which it doesn’t rise un­til the early hours. As a re­sult, there’s a win­dow of about 12 days sur­round­ing new Moon when you’re as­sured of a dark Moon­less sky that is ideal for stargaz­ing.

HOW TO FIND IT:

Get a poster of Moon phases or find the info on­line and be sure to plan any stargaz­ing ac­tiv­i­ties around new Moon.

Find that un­miss­able ‘smudge’ in the win­ter night sky

Does a bright blob al­ways catch your eye when you’re out stargaz­ing in au­tumn and win­ter? It’s al­most cer­tainly the Pleiades (M45), a clus­ter of stars 440 mil­lion lightyears dis­tant that’s also called the Seven Sis­ters. It’s a young clus­ter of stars just 100 mil­lion years old. Even with the naked eye you should be able to make out about five or six of its stars form­ing the shape of a mini Plough.

HOW TO SEE IT:

Low in the east at dusk in Novem­ber, the Pleiades is a gem of the win­ter night sky. Part of the con­stel­la­tion of Taurus, it’s vis­i­ble every night un­til May.

Ob­serv­ing the full Moon is best done at moonrise

Most begin­ners pre­sume that the best time to ob­serve the Moon is when it’s high in the night sky, but at that point it’s way too bright. In­stead, find out the ex­act time of moonrise on the night of the full Moon and watch our satel­lite ap­pear on the horizon dur­ing dusk in a gorgeous pale orange colour.

HOW TO SEE IT:

Get some­where rea­son­ably high with a clear view of the east­ern horizon at dusk on the night of the full Moon.

Night vi­sion makes stargaz­ing much eas­ier

As your eyes grow ac­cus­tomed to dark­ness, your pupils di­late and al­low in more light. It’s why pa­tience is so im­por­tant when stargaz­ing.

HOW TO GET IT:

Keep away from all bright lights for at least 20 min­utes (yes, that ab­so­lutely does in­clude your smart­phone!) and, if you do need to use il­lu­mi­na­tion in the field (to read or make notes), use a dim, red light.

Light pol­lu­tion can be help­ful

A dark sky full of stars is an in­cred­i­ble sight, but light pol­lu­tion isn’t al­ways a bad thing. When you’re try­ing to learn the shapes made by the main, bright stars of con­stel­la­tions, the fact that the back­ground of thou­sands of stars is ‘miss­ing’ be­cause of ur­ban light­ing can ac­tu­ally be use­ful. So for now learn to live with light pol­lu­tion… you’ll grow to hate it soon enough.

HOW TO AVOID IT:

If you’re stargaz­ing from an ur­ban area, stand in the shadow of a build­ing where there are no street­lights or other lights di­rectly in your field of view.

Pick your me­teor-spot­ting ses­sions care­fully

The thought of shoot­ing stars ‘rain­ing down’ is enough to ex­cite any stargazer, but in prac­tice many of the mi­nor me­teor show­ers can be a let-down. Firstly, it’s quite of­ten cloudy on ‘peak’ night. Se­condly, the num­ber of me­te­ors you can see in an hour of peak ac­tiv­ity is change­able. Thirdly, strong moon­light and light pol­lu­tion can com­pletely wipe out most of them.

HOW TO SEE THEM:

Mi­nor me­teor show­ers such as the Lyrids, Ori­on­ids and Leonids pro­duce at most 10-20 shoot­ing stars per hour, and of those far fewer are likely to be eas­ily vis­i­ble. Their peak nights are best treated as great nights to go gen­eral stargaz­ing, with the added bonus of see­ing a few shoot­ing stars. Only the year’s ma­jor me­teor show­ers – the Per­seids in Au­gust and the Gem­i­nids in De­cem­ber – are worth a ded­i­cated trip to a dark sky site.

The chang­ing sky

As Earth or­bits the Sun, the po­si­tions of stars change slightly, ris­ing in the east four min­utes ear­lier each day. Con­se­quently, the en­tire night sky ap­pears to shift for­wards by four min­utes each night. You most likely won’t no­tice this if you spend a few con­sec­u­tive nights stargaz­ing at the same time of night, but over the course of a month it’s a two-hour dif­fer­ence. So stars ris­ing at 10pm in Oc­to­ber can be seen at 8pm by Novem­ber.

HOW TO SEE IT:

Look at the sky at a com­pletely dif­fer­ent time of night than you’re used to. In fact, if you stargaze at 2am in Oc­to­ber you’re ac­tu­ally look­ing at the same night sky that will be vis­i­ble at 8pm in Fe­bru­ary. So it doesn’t ac­tu­ally take a year to ob­serve all the sea­sonal stars and con­stel­la­tions, af­ter all.

The Milky Way is only over­head in sum­mer

That bright core of our Gal­axy that you al­ways see in pho­to­graphs is only vis­i­ble over­head dur­ing sum­mer, when Earth is fac­ing to­wards the cen­tre of the Milky Way about 75,000 lightyears away. In win­ter, we’re look­ing out­ward into deep space.

HOW TO SEE IT:

Look south­east af­ter dusk in June, July and Au­gust from a dark sky site.

Some stars are vis­i­ble all year long

Earth’s northerly axis points roughly to Po­laris, the North Star, which ap­pears sta­tion­ary in the night sky as all other stars in the north­ern sky ap­pear to re­volve around it. The two close con­stel­la­tions of the Plough and Cas­siopeia are thus al­ways vis­i­ble to stargaz­ers in the north­ern hemi­sphere. In the rest of the north­ern hemi­sphere sky, stars rise in the east and set in the west. Fur­ther south, there’s a whole hemi­sphere of stars and con­stel­la­tions that we, at our northerly al­ti­tude, never get to see.

HOW TO SEE IT:

Look north at any time of year to find Po­laris be­tween the Plough and Cas­siopeia (though in au­tumn and spring they can get lost on the horizon). If you stargaze at the same time of night through­out the year, you’ll see that stars and con­stel­la­tions are each vis­i­ble for six months, dur­ing which time they shift slowly from east to west. For the rest of the year, they’re only ‘up’ dur­ing day­light.

Satel­lites are a reg­u­lar sight

You don’t have to stargaze for long be­fore you see a satel­lite whizz across the night sky. Dur­ing an hour’s stargaz­ing you can see dozens, all of which are over 6m in length and in a low-Earth or­bit around 160640km up. You’re look­ing at re­flected sun­light, so it’s a con­stant light un­like the flashes from air­craft.

HOW TO SEE THEM:

You’ll see more satel­lites just af­ter dusk and just be­fore dawn, though in the UK sum­mer the Sun doesn’t sink as far be­low the horizon, so satel­lites can be seen all night.

Travel north for a bet­ter chance of an aurora sight­ing

The re­sult of elec­tri­cally charged par­ti­cles ejected from the Sun in­ter­act­ing with Earth’s mag­netic field and at­mos­phere, the North­ern Lights, or Aurora Bo­re­alis, move in an oval shape around the Arc­tic Cir­cle on the night-side of Earth. Th­ese au­ro­rae wax and wane from north to south, so they can oc­ca­sion­ally be seen from Scot­land, north­ern Eng­land and north Wales.

HOW TO SEE IT:

If you want to max­imise your chances, take a trip to a place within the lat­i­tudes of 64º and 70º north be­tween Oc­to­ber and March: places such as Ice­land, north­ern Nor­way, La­p­land in Finland or Swe­den. How­ever, if there are huge sunspots, stargaz­ers can some­times see a green glow on the north­ern horizon from the UK. The best places are Scot­land’s north­ern coast and Orkney (both at 59° north), and the Shet­land Is­lands (60.5° north).

Your pe­riph­eral vi­sion is pow­er­ful

The hu­man eye’s pe­riph­eral vi­sion is very sen­si­tive to bright­ness, so look slightly to the right of a star clus­ter, ne­bula or gal­axy to see its glow. Con­versely, when ob­serv­ing a star or planet, look di­rectly at it to see colour.

HOW TO SEE IT:

Look just above the Pleiades for a good les­son in this ‘averted vi­sion’ technique, which works just as well with the Orion Ne­bula (M42), the An­dromeda Gal­axy (M31) and any star clus­ter.

Flar­ing could be satel­lites

If you see a satel­lite sud­denly go ex­tremely bright for a few sec­onds be­fore fad­ing fast, that’s an ‘Irid­ium flare’, a glint off one of a net­work of satel­lites from the Irid­ium Satel­lite Com­mu­ni­ca­tions com­pany. If it was much quicker, you prob­a­bly saw a me­teor.

HOW TO SEE THEM:

Since irid­ium is now de-or­bit­ing its old flar­ing satel­lites and re­plac­ing them with smaller ones, flares are be­com­ing rarer. They are due to be nonex­is­tent by the end of 2018 so if you want to see one, be quick! Visit heav­ens-above.com/Irid­i­umFlares.aspx to get ex­act tim­ings for where you live.

Spot the space sta­tion mov­ing from west to east

If you see a bright light rise roughly in the west, get ex­tremely bright and then dis­ap­pear in the east­ern sky, you prob­a­bly just saw the In­ter­na­tional Space Sta­tion (ISS) or, rather, its huge so­lar pan­els re­flect­ing sun­light. The ISS or­bits Earth 16 times each day at 27,600km per hour, which is around 8km per sec­ond.

HOW TO SEE IT:

You can only see the ISS when it’s cross­ing over­head just af­ter dusk and just be­fore dawn. If you do see it soon af­ter dark, wait 92 min­utes and you’ll prob­a­bly see it again. Visit NASA’s spot­thes­ta­tion.nasa.gov web­site to get ex­act tim­ings for where you live.

Plan­ets are very easy to find

The Sun and the plan­ets ap­pear to move across the sky on roughly the same path, which re­veals that all the plan­ets in the So­lar Sys­tem or­bit the Sun in a vir­tu­ally flat disc. This is called the eclip­tic, and it’s here that you’ll find the plan­ets close by. The Moon also roughly fol­lows the eclip­tic.

HOW TO SEE IT:

The eclip­tic stretches from the point on the east­ern horizon where the sun rises to where it sets in the west; look to the south af­ter dark and trace the po­si­tion of the plan­ets. Since Mer­cury and Venus are in­ner plan­ets, they are only vis­i­ble in the west soon af­ter dusk, or be­fore dawn.

ABOUT THE WRITER Jamie Carter is a sea­soned astronomer and au­thor of A Stargaz­ing Pro­gram for Begin­ners: A Pocket Field Guide

Prac­ti­cal, hands-on ob­serv­ing is of­ten the best way to truly get to grips with the sub­tleties of stargaz­ing

You can find the same in­for­ma­tion on the in­ter­net but noth­ing beats the at-aglance sim­plic­ity of a Moon phase poster

The Pleiades is the most eas­ily vis­i­ble open clus­ter in the night sky with the naked eye M45, the Pleiades

Top tip for ob­serv­ing the full Moon – catch it early

Use a red light when ob­serv­ing to main­tain your dark-adapted vi­sion

Some me­teor show­ers are more re­li­ably spec­tac­u­lar than oth­ers

Try think­ing of ur­ban glow as a handy begin­ner’s fil­ter

The fact that the stars move is no great rev­e­la­tion, but know­ing by how much can be very use­ful

The peak of the ‘Milky Way sea­son’ is around the June sol­stice

In the north­ern hemi­sphere, the en­tire sky re­volves around the Pole Star, Po­laris

Your chances of see­ing the North­ern Lights in­crease the fur­ther north you go

Shoot­ing star or satel­lite? Is it wrong to wish on space hard­ware?

You can find all the plan­ets along the eclip­tic – the path of the Sun

Al­though it seems counter-in­tu­itive,not look­ing di­rectly at a gal­axy can make it ap­pear brighter

If it’s trav­el­ling fast and in a dead straight line, it’s the In­ter­na­tional Space Sta­tion

Flar­ing satel­lites will soon be a thing of the past

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