The Jewel Box

Located at 60° South, the Jewel Box (in Crux)  is one of those southern gems which I keep returning to but this is the first time I’ve imaged this object with my ZWO astro-camera.

The cluster is a closely bound group of over a hundred stars, all very young – reputed to be ‘only’ about seven million years old. 

Most of them are blue ‘giants’ but at least one of the brighter stars is a ‘red supergiant’ – and this is easily seen when I show this object at public nights.

Unlike a lot of astronomical objects, it actually bears some resemblance to its name!

---

I followed the  exact exposure and gain levels which were recommended by the SharpCap “Brain” histogram tool – but I’m wondering, with this type of object, whether it  should be factored down a bit.

---

I had to locate the object by manually searching, because the EQ6 mount 3-star alignment routine was not aligning.

American date format? ✔   Time? ✔   Daylight Saving? ✔   Coordinates? ✔   Altitude✔  Hemispheres?  ✔   Polar alignment?   ✔

It has to be one of the above settings. I tried four times but each time I sent it to an alignment star it went somewhere else not even close. Even a 1-star alignment failed.

I checked the handset entries again in daylight the next day and they seemed correct……

It’s only five months since I resolved the last alignment issue I had with it.  😨

#@#$*&@!!!??

---

Object Details:

Designation: The Jewel Box Cluster, NGC 4755, Caldwell 94.
Constellation: Crux.
Visual magnitude:  +4.2
Apparent size:  10′ x 10′.
Diameter: 18.7 light years.
Distance:  6,400 light years.
Altitude: 47° above SW horizon.

Image:

Exposure: 2700 sec (45 minutes) 113 frames @ 23.9 sec
Gain:  92
Date:  2019-06-11
Location:  outer suburban.
Conditions:  clear.
Moon:  yes, FQM+1, 62° from target
Sky:  2.66 e/pixel/s  

Processing:

Image acquisition software:  SharpCap, live stacked.
Image post-processing:  GIMP.
Cropping:   slight edge trim only.

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: N	Guiding:	No
Polar aligning:	QHYCCD PoleMaster	Polar Error:	03’ 50”

Relevant:

Jewel Box Cluster taken in 2015 with Canon 60D and 8″ Schmidt-Cassegraine telescope.

Geek Log:

[ZWO ASI071MC Pro]
Debayer Preview=On
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=Maximum
Gain=92
Exposure=23.886693
Timestamp Frames=Off
White Bal (B)=50
White Bal (R)=53
Brightness=12
Temperature=2.1
Cooler Power=100
Target Temperature=-15
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=2019-06-11T13:35:28.0442659Z
SharpCapVersion=3.2.5986.0
TotalExposure(s)=2699.196309
StackedFrames=113

---

Image © Roger Powell

---