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The Jewel Box ( NGC 4755 ) is an open cluster of mostly hot young blue-white stars that appears to the unaided eye as a bright 4th magnitude star close to the Southern Cross. Only visible from southern latitudes, the Jewel Box was first recorded by Nicolas Louis de Lacaille during his visit to South Africa in 1751 and was later described by Sir John Herschel as "a casket of variously coloured precious stones" - hence the name "Jewel Box".

549E5F22-290D-4E9F-8FCC-330D52FFC70A.thumb.jpeg.c498c64b6a8a4e1a6dcdaded4479cbfe.jpeg

The Jewel Box Open Cluster ( ngc 4755 ) in the Crux constellation.  ( please click / tap to see larger and sharper )

...........

Image details:

Orientation: North is up

Telescope: Orion Optics CT12 Newtonian ( mirror 300mm, fl 1200mm, f4 ).
Corrector: ASA 2" Coma Corrector Quattro 1.175x.
Effective Focal Length / Aperture : 1470mm f4.7

Mount: Skywatcher EQ8
Guiding: TSOAG9 Off-Axis-Guider, Starlight Xpress Lodestar X2, PHD2 

Camera:
Nikon D5300 (unmodified) (sensor 23.5 x 15.6mm, 6016x4016 3.91um pixels)

image Plate Solver script version 5.0
===========
Resolution ........ 0.586 arcsec/px
Rotation .......... 0.000 deg
Focal ............. 1375.43 mm
Pixel size ........ 3.91 um
Field of view ..... 58' 49.3" x 39' 17.8"
Image center ...... RA: 12 53 40.040  Dec: -60 21 02.81
==========

Location:
Blue Mountains, Australia 
Moderate light pollution ( pale green zone on darksitefinder.com map )

Capture (  5 May 2018 ):
11 sets of sub-images with exposure duration for each set doubling ( 1/8th sec to 120 sec ) all at ISO250.
( 10 x 120sec + at least 10 each forthe other durations )

Processing:
Calibration: master bias, master flat and master dark
Integration in 11sets
HDR combination 

 

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