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. 😨
Designation: The Jewel Box Cluster, NGC 4755, Caldwell 94.
Visual magnitude: +4.2
Apparent size: 10′ x 10′.
Diameter: 18.7 light years.
Distance: 6,400 light years.
Altitude: 47° above SW horizon.
Exposure: 2700 sec (45 minutes) 113 frames @ 23.9 sec
Location: outer suburban.
Moon: yes, FQM+1, 62° from target
Sky: 2.66 e/pixel/s
Image acquisition software: SharpCap, live stacked.
Image post-processing: GIMP.
Cropping: slight edge trim only.
|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”|
Jewel Box Cluster taken in 2015 with Canon 60D and 8″ Schmidt-Cassegraine telescope.
[ZWO ASI071MC Pro]
Output Format=FITS files (*.fits)
Frame Rate Limit=Maximum
White Bal (B)=50
White Bal (R)=53
Auto Exp Max Gain=300
Auto Exp Max Exp M S=30000
Auto Exp Target Brightness=100
Anti Dew Heater=Off
Display Black Point=0
Display MidTone Point=0.5
Display White Point=1
Image © Roger Powell