Cat’s Paw Nebula

A bright emission nebula, located 820 light-years away in the Scorpius region of the Milky Way. The red colour comes from ionised hydrogen atoms, excited by young bright stars within.

This was a one hour exposure, unguided.

Since I began reusing my light pollution filter a couple of months ago, the SharpCap software has been recognising a more contrasty sky and as a consequence has been recommending longer optimal frame exposures. So I felt the need to resume image guiding; and this field night with the Society marked my return to  guiding after a gap of twelve months (when my Starshoot guide camera carked it). I had been making do with multiple short exposures but this night I set up my ZWO 290 as guide camera in order to take a lesser number of longer exposures.

Not all went well of course.

I took two deep sky images during the evening and the guiding was perfect for the other image but failed completely for this particular one. One of those  mystery glitches, I suppose – the two objects were only 15° apart.

The Moon is now waxing and will make it difficult to do any serious imaging for the next two weeks but I have two more images left to post over the next few days.

Weather is always an issue and tonight was a scheduled First Quarter Moon Public Night with the Society and the sky was clear but the wind was gusting up to 60 kph, making it unsafe to venture over to the Observatory. How strange to have a clear sky and still be forced to cancel!

Object Details:

Designation: Cat’s Paw Nebula, NGC 6334, Gum 64.
Constellation: Scorpius.
Visual magnitude:  +10.0
Apparent size:  40′ x 30′
Diameter:  9.5 light years.
Distance:   820 light years.
Altitude during exposure:  57° above W horizon.

Please feel free to ignore the technical stuff.


Exposure:  83 x 43.75 sec = 60 min.
Gain: 260
Date:  2019-09-03
Location:  semi-dark rural.
Conditions:  clear
Moon: Crescent NM+4


Image acquisition:  SharpCap.
Method: Live stacked.
Darks: 10x
Image post-processing:  GIMP.
Cropping:   Yes
Sky:   0.27 e/pixel/s .


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 (failed)
Polar aligning: QHYCCD PoleMaster Polar Error: 00’ 28”

Geek Log:

[ZWO ASI071MC Pro]
Debayer Preview=On
Output Format=FITS files (*.fits)
Capture Area=4944×3284
Colour Space=RAW16
Hardware Binning=Off
Turbo USB=40
Frame Rate Limit=4 fps
Timestamp Frames=Off
White Bal (B)=50
White Bal (R)=53
Cooler Power=45
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\118.4s\gain_220\dark_10_frames_-14.8C_2019-09-03T09_45_02.fits
#Black Point
Display Black Point=0
#MidTone Point
Display MidTone Point=0.5
#White Point
Display White Point=1

Image © Roger Powell

1 Comment

Your say.......

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s