Globular Cluster 47-Tucanae

Deep in the Southern sky, right next to the Small Magellanic Cloud and just 18° from the South Celestial Pole, lies this magnificent globular cluster.

With millions of stars, 47-Tucanae is the second largest globular cluster in the sky  after Omega Centauri. Its brightest stars are around 11th magnitude but despite this, the overall magnitude of about +4 makes it a fairly easy object to spot as a fuzzy object in a dark sky – provided you are situated south of latitude 18 North!

The Northern Hemisphere has its attractions, such as M31, which is so low here in Sydney. However, we are well situated here in the South to see the two brightest globular clusters – 47 Tucanae, Omega Centauri – and both Magellanic Clouds.

This 51 minute image was shot from my home in surburbia .

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Daylight saving arrived today, meaning observing sessions will be cut short.

They will at least be warmer than the field trips we’ve experienced over the winter months, where the minimum dropped to between zero and -5° C.

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Object Details:

Designation: 47-Tucanae, NGC 104, Caldwell 106.
Constellation: Tucana.
Visual magnitude:  +3.95
Apparent size:  50′
Diameter:  213 light years.
Distance:   15,000 light years.
Altitude during exposure:  48° above southern horizon.
Also in image: NGC 121, a more distant globular cluster (left, bottom ). Astrometry.net

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Technical stuff:

Image: Exposure:  35 x 88 sec =  51 min. Gain:  136 Date:  2019-10-01. Location:  outer suburban. Conditions:  clear. Moon: no.

Processing: Image acquisition:  SharpCap. Method: Deep Sky Stacker. Darks: yes. Image post-processing:  GIMP. Cropping:   yes. Sky:   0.56 e/pixel/s .

Gear:

Telescope:	SkyWatcher Esprit	Type:	120ED triplet refractor
Focal:	840 mm F/7	Mount:	SkyWatcher EQ6-R Pro
Camera:	ZWO ASI 071 MC Pro	Type:	CMOS 28.4mm 16 Mpx
Optical aids:	Flattener: Y; filter: LP	Guiding:	Yes
Polar aligning:	QHYCCD PoleMaster	Polar Error:	60”

Geek Log:

[ZWO ASI071MC Pro] Debayer Preview=On Pan=0 Tilt=0 Output Format=FITS files (*.fits) Binning=1 Capture Area=4944×3284 Colour Space=RAW16 Hardware Binning=Off Turbo USB=40 Flip=None Frame Rate Limit=4 fps Gain=136 Exposure=88.006908 Timestamp Frames=Off White Bal (B)=50 White Bal (R)=53 Brightness=20 Temperature=-16.1 Cooler Power=100 Target Temperature=-20

Cooler=On Auto Exp Max Gain=300 Auto Exp Max Exp M S=30000 Auto Exp Target Brightness=100 Mono Bin=Off Anti Dew Heater=Off Banding Threshold=35 Banding Suppression=0 Apply Flat=None Subtract Dark=None #Black Point Display Black Point=0 #MidTone Point Display MidTone Point=0.5 #White Point Display White Point=1 TimeStamp=2019-10-01T12:23:29.5441692Z SharpCapVersion=3.2.6086.0 TotalExposure(s)=3080.24178 StackedFrames=35

Image © Roger Powell