Lying amongst the Milky Way star fields over 4000 light years away, M17 is a distinctly reddish nebula due to excitement of hydrogen gas heated up by hundreds of new-born stars embedded in it. It has a white core of hotter gas at its centre, where many of the young stars reside.
The visible nebula is about 15 light years in diameter but the full gas cloud extends way beyond that.
I chose shorter than usual exposures on this occasion, to avoid the risk of trailing stars, as my polar alignment was relatively poor. This image was a 75 minute exposure, composed of 287 x 15.75 sec sub-frames. The lap-top was playing up too, freezing up and dropping quite a few sub-frame images.
Designation: Messier 17, NGC 6618.
Visual magnitude: +6.0.
Apparent size: 46′ x 37′.
Diameter: 56.7 light years.
Distance: 4,200 light years.
Altitude during exposure: 65° above NE horizon.
End of blog.
Skip the technical stuff below if you like and leave a comment at the end.
Exposure: 75 minutes ( 287 x 15.75 sec).
Location: outer suburban.
Moon: 4 day old crescent.
Sky: 2.04 e/pixel/s.
Image acquisition software: SharpCap, live stacked.
Image post-processing: GIMP.
Cropping: edges 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:||12’ 28” (poor)|
[ZWO ASI071MC Pro]
Output Format=FITS files (*.fits)
Frame Rate Limit=Maximum
White Bal (B)=60
White Bal (R)=60
Auto Exp Max Gain=300
Auto Exp Max Exp M S=30000
Auto Exp Target Brightness=100
Anti Dew Heater=Off
Display Black Point=0.154207155477032
Display MidTone Point=0.370303618066313
Display White Point=0.998046875
Image © Roger Powell