DEEP-SKY OBSERVING
by
Eric Brindeau & Peter Baxter

This month we star hop in the regions of the large constellations of CAPRICORNUS and AQUILLA, which will be gracing our night skies for the months to come. We also take a peak close to the galactic centre near the constellations of SAGITTARIUS and neighbouring SCORPIUS, which are fast heading towards the western horizon.

We will be hopping to a few of the brighter deep sky objects that can be found in a small scope, as well as offering a few challenging ones. Neptune and Uranus are both travelling through Capricornus at the moment, and we suggest adding these to your observing itinerary.

If you recall the previous SSSH article that featured the constellation of LEO, you might have been enjoying the beautiful sight of Venus edging slowly towards Regulus that lies on the ecliptic.

 THE DEEP SKY STAR HOP

 We have been admiring the night sky regions of Scorpius and Sagittarius, as the galactic centre of the Milky Way has passed overhead. These constellations have so many deep-sky objects, they seem to equal the density of the star fields in the rich knots of the Milky Way, several spiral arms thick. It is easy to understand how many of us do not get to explore further than the Lagoon (M8), Trifid (M20) and the Omega (M17) nebulas which are small deep-sky macrocosms on their own. Sagittarius alone contains more Messier objects than any other constellation (7 globular clusters, 5 open or galactic clusters and 3 gaseous nebulas).

 We will use the sting of the Scorpio tail to star hop passed the open cluster of M7 and head for a challenging planetary nebula in Sagittarius.

Scorpius is a magnificent constellation, one of the few that visually live up to its name. An imaginary line drawn from alpha (a ) Crucis through alpha (a ) Centaurus will take you roughly to Scorpio with the unmistakable red super giant of Antares.

Starting at upsilon (u ) and lambda (l ) Scorpii, the two stars that make up the scorpions sting, head for G which is positioned by triangulating chi (c ) and lambda (l ) Scorpii. Very close to G is perhaps one of the easiest globular clusters to find. NGC 6441 lies right next to the bright yellow G making a stunning contrasting view. The globular appears as a bright round hazy disk at magnitude 8.0 and is difficult to resolve even in the largest amateur telescopes.

 Moving further towards Sagittarius you will pass the magnificent naked eye open cluster M7. This object can be appreciated in almost any size scope, but a good pair of binoculars remains one of the best ways to enjoy the wide sprinkling of stars. M7 is nearly double the size of the full moon and contains about 80 stars brighter than 10^th magnitude.

 If you are viewing with an 8" or larger telescope, you may want to try to find the tiny 10^th magnitude globular cluster NGC 6453 lurking on the edge of the open cluster. M7 is also home to a few faint planetary nebulas, beginning at magnitudes 13 and fainter.

 Finding NGC 6453 seems a daunting task at first as one is faced with such an array of stars. The globular lies to the edge of M7, slightly away from the denser centre and easily located using three brighter guide stars that remind one of Orion’s belt.

 Centre the cluster in your finder and try to keep in mind an imaginary line going back to the Scorpio sting. To one side of the cluster centre are three distinctively spaced bright stars, which form a line in between the Scorpio sting and M7. The closest star of this trio to the centre of the open cluster has a fainter companion. Visualising a triangle with the first star (with its companion) and the next of the trio as the base will give you the location of the globular cluster. NGC 6453 appears as a small irregular shaped disk of even brightness, with a few stars involved as seen in a 12". Finding this gem is a challenge and it is worth the hunt.

 Sagittarius the Archer is too an easily recognisable constellation. We would have to disagree with Patrick Moore in his book "Stars of the Southern Skies" where he states "-but there is no obvious pattern. It is often nicknamed the Teapot, though I have never been able to understand why!" As a shape the Teapot makes more visual sense once you grasp the figure for the first time – granted that for us in the southern hemisphere the Teapot is not always directly perceivable as it is often seen on its side or upside-down.

 The next object is a 13^th magnitude planetary nebula NGC 6563, which is located near the Teapot spout. If you have ground and polished you’re own 6" or larger mirror in the societies telescope making classes, this object will test its performance and your viewing skills. It is now referred to as Peter Baxter’s Planetary in our unofficial catalogue after finding this little planetary in his 6"f /6.5 scope finished in the classes a few years ago.

 Peter Baxter’s Planetary is very faint, but the undertaking is made simpler as this object is very easy to locate. Imagine an equilateral triangle using epsilon (e ) and eta (h ) Sagittarii as the base, the planetary will fall at the apex. Aligning your finder with eta (h ) and epsilon (e ) in view, you will see a small right-angled triangle at the apparent apex. The planetary lies almost midway of the hypotenuse (long side) as in the accompanying finder sketch. Depending on the sky conditions and the size of scope, you might have to use averted vision to see this round grey disk. In a 12" scope it appears as a round pale grey disk 50x35 arcseconds with even illumination.

CAPRICORNUS and AQUILLA are the most prominent constellations coming up behind Sagittarius. Capricornus the Sea Goat is associated with the ocean-orientated part of winter constellations along with Aquarius, Pisces and Cetus. Aquila the Eagle can be seen soaring as its spread wings dominate the evening skies (more like a manta ray).

Using a lot of imagination, Capricornus represents a goat with a fish tail. Using less imagination, we liken Capricornus to the continent of Africa (the early version as first sketched by the 16^th century seafarers!). In John Sanford’s "Observing the Constellations", he describes how some amateurs have come to call Capricornus the "Bikini Bottom" (must have originated from an astronomical society in Florida). The large constellation is devoid of many deep-sky objects, but it is the starting point of finding two bright globular clusters as well as being home (for the moment) of the planets Uranus and Neptune.

M 30 is a rich globular cluster for the small telescope and can be seen in binoculars as a fuzzy spot. Catalogued by Messier in 1764, this globular is bright and the edges can be resolved in scopes as small as 4 inches. M 30 is easy to find by using epsilon (e ) and zeta (z ) as the base of a triangle, the globular falling at the apex next to a bright star 41 Capricorni. The accompanying star hop uses three pairs of stars to get there – starting with delta (d ) and gamma (g ), going through epsilon (e ) and chi (c ) and ending with the bright pair containing 41 Capricorni. Studying the arrangement of stars carefully will reveal a horseshoe string of stars as situated on one edge.

Before leaving Capricornus, study the multiple star system of alpha (a ) Capricorni. Alpha (a ) is a naked eye double consisting of the components a1 and a2 which are 376 arcseconds apart (unrelated). Each star is again a double – a1 has a 9^th magnitude companion and a2 has an 11^th magnitude companion (also a double star).

Another excellent bright globular cluster lies to the other side of Capricornus (on the West Coast) in the top of the constellation Aquarius. Burnham’s describes the fine globular cluster M 2 as a "ball of glowing mist". At an integrated magnitude of 6.0, this globular should be a naked eye object for someone with keen eyesight. It lies in a sparsely populated region of the sky with no distinct bright markers to star hop from.

Starting with the tip of Africa in Capricornus as our point of departure using delta (d ) and gamma (g ), move into Aquarius and find the first really bright star – beta (b ) Aquarii. M 2 is a star hop away in the same direction as we have just come. The finder scope views will show the exact star detail as one moves away from beta (b ) towards M 2, which is flanked by two pairs of stars. The cluster begins to resolve in telescopes of 8 inches and up.

Below Altair, the brightest star in Aquila, you will find the small constellation of DELPHINUS the Dolphin. This kite-shaped constellation is easily recognised and lies on the edge of the Milky Way in a fairly open part of the sky. What first attracted our attention is the beautiful double star gamma (g ) Delphini, consisting of two yellow stars of 4^th and 5^th magnitudes - moderately easy to split in small scopes at 9.6 arcseconds.

Delphinus is also home to two planetary nebulas, as well as two globular clusters – one of which is thought to be the most remote globular of our galaxy (comparable to the Magellanic clouds). The globular is lying at about 150 000 light years from the centre of our galaxy, making it about 185 000 light years from the solar system. Considering the interesting fact that globular clusters indicate a galaxy’s extreme dimensions, this is an interesting deep sky target.

NGC 7009 glows at magnitude 11.5 (or 10.6 depending on the source) and appears as a one-arcminute disk. The globular remains a fuzzy disk in amateur telescopes, the brightest stars are of 16^th magnitude! NGC 7006 is visible in a 6" scope and it is not too difficult to hunt down.

 If you have an equatorial mount or other drive system which will allow you to set the RA (right ascension) and DC (declination), centre your view on gamma (g ) and either move your scope in 18 minutes of RA, or switch your drive off while you go make coffee. The co-ordinates for gamma are provided below.

To star hop, centre gamma (g ) in your finderscope and start to move the scope in the same direction as the line from alpha (a ) to gamma (g ). Not too far away you will come across two odd box shapes as per the finder sketch. The globular lies just to the top of the parallelogram-shape, making a triangle with the top two stars of that asterism.