open cluster A Cluster of Pearls in the Southern Skies ( NGC 3766 "The Pearl Cluster" in Centaurus ) - updated

[MikeODay]

21st April: Re-processed to better show the colour of the fainter stars ...

 

 

.......

Shimmering like a pearl to the naked eye, this open cluster of mostly young blue stars ( known as the "Pearl Cluster" ) is approximately 5500  light years from Earth and was discovered by Abbe Lacaille in 1752 from South Africa.  

This HDR image is constructed from 11 sets of exposures ranging from 1/4 sec ( to capture the centre of the brighter stars ) through to 240 seconds ( for the fainter stars of the Milky Way ).  Total exposure time was around 5 hours.

A Cluster of Pearls in the Southern Skies ( NGC 3766 " The Pearl Cluster" ) 
( please click / tap on image to see larger and sharper - a full size image can be found here )

12 April 2018

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Image details:

Field of view ..... 58' 49.8" x 39' 36.4"
Image center ...... RA: 11 36 03.890  Dec: -61 35 30.17
Resolution ........ 0.586 arcsec/px  ( full size image )
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)

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

Capture ( 12 April 2018 ):
11 sets of sub-images with exposure duration for each set doubling ( 1/4s to 240s ) all at ISO250.
( 70 x 240sec + 10 each forthe other durations )

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

Pixinsight April 2018

[pi_co100]

Beautiful! Thanks for sharing.

[MikeODay]

17 hours ago, pi_co100 said:

Beautiful! Thanks for sharing.

Cheers, thanks for that.

[Allinthehead]

Wonderful work Mike. Your hdr method works very well with star clusters.

[MikeODay]

4 minutes ago, Allinthehead said:

Wonderful work Mike. Your hdr method works very well with star clusters.

Thanks Richard.  It certainly helps to bring out the subtle colours

[MikeODay]

A subtle tweak to lift the background a little ...

What do you think, better or not ?

[MikeODay]

And some crops from the full size image ( the top two can be enlarged further by clicking on them, the bottom three are already at 100% ).

 

 

 

 

 

 

 

 

 

I fascinated by the twirls, swirls and straight lines formed by the apparent positions of the stars.

[Allinthehead]

8 hours ago, MikeODay said:

What do you think, better or not ?

Yes the second is better, slightly brighter without making the stars bigger.

[MikeODay]

Thanks Richard.  After working on and looking at an image for a long time I sometimes find it hard to judge the impact of small changes so another pair of eyes are much appreciated

 

[MikeODay]

Re-processed to bring out the colour in the fainter stars ...

 

 

 

 

 

[MikeODay]

Some more 100% crops showing patterns and the colours ranging from bright blue to deep orange