Lambda Centauri Cluster

The Lambda star cluster (IC 2944) and the Running Chicken emission nebula (IC 2948).

I think I considerably under-exposed this image. The cluster shows up reasonably well but there is considerably more nebulosity available than I managed to draw out in post-processing.

One of the features of the SharpCap Pro image acquisition software is the ability to advise on the best exposure levels suited to this particular night sky with that particular CMOS camera. I’m slowly beginning to get the hang of SharpCap but I goofed a bit this time and the image was disappointing.

2019-02-11 Brain
2019-02-11 The Brain function of SharpCap’s Smart Histogram advises on exposure levels for the prevailing conditions.

It may look complex but this SharpCap graph simply indicates that the optimal exposure I should use have used with my ZWO ASI071 camera that night was 31.6 seconds with a gain setting of 92.

It also clearly indicates that long exposures of several minutes (as CCD camera users would be required to use) would not have been useful for this camera in this light polluted sky.

After trying it, I reduced the exposure period to 25 seconds, because – in my naivity – I thought it was over-exposing. I ended up regretting it because the reduction of about 20% actually underexposed the image.

Next time I might follow the instructions….  🤓

Constellation Centaurus Altitude: 45° above SSE
Magnitude: +4.5 Apparent Size 65′
Diameter 111 light years Distance 5,900 light years
Exposure: 25.9s x 142 live stacked Gain: 92
Date 2019-02-11 Time: approx 11.30 pm
Location: Home Sky: Suburban pollution
Cloud: Mostly clear. Moon: 33% set aprox 11.30 pm
Acquisition: SharpCap live stack. Processing: GIMP
Cropping: Yes
Telescope: Skywatcher Esprit 120ED Type: APO 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: yes; filter: no. Guiding: No
Polar aligning: QHYCCD PoleMaster Polar Error: 03’ 15”

Link to annotated astrometry image.

Geek Log:

[ZWO ASI071MC Pro]
Debayer Preview=On
Output Format=PNG files (*.png)
Capture Area=4944×3284
Colour Space=RAW16
Hardware Binning=Off
Turbo USB=100
Frame Rate Limit=Maximum
Timestamp Frames=Off
White Bal (B)=50
White Bal (R)=53
Cooler Power=100
Target Temperature=-15
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=C:\Users\Roger\Desktop\SharpCap Captures\darks\ZWO ASI071MC Pro\RAW16@4944×3284\25.9s\gain_92\dark_20_frames_-12.3C_2019-02-09T10_58_25.png
#Black Point
Display Black Point=0
#MidTone Point
Display MidTone Point=0.5
#White Point
Display White Point=1


Images © Roger Powell


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