Deep sky observing report (2009 Jan 01/02)

posted: 3120 days ago, on Thursday, 2009 Jan 08 at 16:17
tags: astronomy, deep sky, observing report, Sutherland.

During the New Moon at the start of 2009, Zbig Zembaty and I enjoyed some dark sky viewing from Sutherland.

Observing from a new site is always both exciting and a gamble, so it was with mixed feelings that we made our way on January 01 to the farm Middelfontein, just outside Sutherland, for the first observing night for 2009.

After setting up and dark adapting, it soon became clear that the evening's cloud-free skies would be good. Despite the proximity to the town of Sutherland, and the occassional distant headlight from a lone car on a remote back road, we were soon enjoying good conditions. Even with my poor naked-eye sight I could see V=6.5 near the zenith.

Zbig was engrossed in taking photos of the "foreign" skies, while I browsed around with Maphefo, the 8-inch f/6 Dobsonian.

Early in the session, I turned the 8-inch on Orion to pick out the Horsehead. NGC 2024, the complex of bright and dark nebulae east of Alnitak (zeta Ori) was obvious, as was the off-centre glow of NGC 2023. And a short glance southward revealed the dim Horsehead, somewhat more apparent at 96x. Amazing what a proper name does for the status of an object! I can think of any number of fields in Argo that hold more picturesque dark nebulae.

Another early target was NGC 4945, an edge-on galaxy in Centaurus. It is a prominent, very much elongated glow at 48x, a ghostly slash hanging in black space between two 4.5th mag stars. One of the easiest bright galaxies to find.

Nearby NGC 4976 was so obvious that it was noticed while sweeping. At 48x it shows as a round glow, growing brighter to the middle. The little galaxy makes a triangle with an 8th mag star (due East) and a nearby 11th mag star.

NGC 4945A again eluded me I will have to try harder, and perhaps use a better map.

A totally different object is NGC 3960. Sweeping the sky at 48x shows a star-rich field which includes an obvious 25-arcmin triangle of 8-9th mag stars. Along the eastern leg of the triangle lies NGC 3960, a ghostly, round, glow of very delicate starlight. Not surprisingly, it is a Bennett object. Its gentle glow is visible in the 9x50 finder. This will be another of my targets for Bertha (12-inch Dob) at the end of the month, because I don't see the "long appendages" that John Herschel noted. Yet, in 1997 Magda Streicher, using an 8-inch SCT and 18mm eyepiece, noted that its stars "form little arms in a spiral structure" so the game's afoot.

It almost goes without saying that a telescope set up in the southern hemisphere, when Argo is visible, is going to be pointed to NGC 3372, the eta Carinae nebula. Casually sweeping over the neighbourhood of the nebula is a jaw-dropping experience. Eta itself is a bright orange star, set in a field overflowing with intricate nebulosity, bright and dark.

Scrutiny of the star itself shows something curious: it is distinctly elongated. Conditions were good so powers of up to 380x could be used to take a closer look. The star is centrally located in an oval nebula, oriented roughly northwest-southeast. The southern part of the nebula is clearly brighter, and very slightly larger, than the north-western part. Beginning at 120x I noticed that a fine dark line (~NE to SW) divides the oval nebula in two, centred on eta, creating the impression of two distinct lobes (or a cocktail sausage pinched in the centre, if you're peckish). Even a wide-field 75-power view shows the two-lobed nebula distinctly.

The entire field is stuffed with mottled patches of light and dark (thank heavens for photography!) that certainly defies my ability to sketch. Perhaps Magda or Carol will take up the challenge.

On closer inspection, the main lobe is oriented to the east-southeast of eta (not southeast); the smaller lobe, at its base, is just 60% the width of the larger, and extends outward for only 75% of its larger cousin's distance. It thus appears narrower than seen at first. More significantly, I get the distinct impression that the two lobes are not oriented with their major axes parallel; the smaller lobe deviates ~20 degrees off the parallel, so that it lies more north-west than NNW (a sketch should make all this clear!). Overall, the nebula is about 15 arcseconds from side to side; the brighter half is 10" at the base extending for 8", while the fainter portion is 6" x 6".

The next night we set up at the old quarry (my usual observing spot) so that I could compare conditions with Middelfontein. Ed was using Lorenzo and I was on Maphefo, while Zbig was taking more pictures. His 10-mm wide-angle lens was capturing some memorable shots.

Before it got too low, we took a look at NGC 253, a delightful object, as always. This slash of gray light amongst bright stars is plainly visible in the 9x50 finder.

I'm always pleasantly surprised by NGC 300, a large oval nebula readily seen at 96x, with several small stars involved. Its moderate surface brightness lends it an ethereal quality and is reminiscent of the SMC seen with the naked eye; or one of the many starry nebulae seen in the Cape Clouds.

Within the great eastward bend of Eridanus the River lie a host of galaxies. A personal favourite is the duo of NGC 1531 & NGC 1532, an easy star-hop from upsilon-4 Eridani. These distinct nebulae, within an obvious triangle of stars, are readily seen at 48x. The pair make a lovely contrasting grouping, floating in space.

NGC 1531 initially appears round but is actual slightly elongated, oriented almost directly towards NGC 1532. It becomes noticeably brighter towards the middle. NGC 1532 is much elongated and grows brighter to the middle to a broad elongated nuclear patch.

NGC 1537 (also in Eridanus) is an obvious little patch within a slender Corvus-shaped asterism of 7-8th magnitude stars. It shows at 96x as a small, round glow growing brighter to the middle.

North-westward from the False Cross is an obvious right-angled triangle asterism of gamma & lambda Velorum, and zeta Puppis (the "Southern Right-Angle"). Sweeping through this triangle at low power is a delight.

Scanning the region more or less midway between gamma & lambda Velorum with 48-power shows field upon field of black, richly sprinkled with tiny stars. My journey is halted at a prominent half-degree right-angled triangle of 6th magnitude stars, and just off its northern tip lies the beautiful ghostly cluster NGC 2659. At least two-dozen stars are obvious, although it is clearly very rich in fainter luminaries, appearing as a large oval over-dense milky way region. Don't let the tiny symbol on the Uranometria chart mislead you this is a big one, about 12 arcminutes in length, oriented northeast-southwest. Brian Skiff exclaimed: "a real cluster for once!"

New Moon month's end here I come.

nothing more to see. please move along.