Planetary Nebula Messier 57 in Lyra
The Ring Nebula
A planetary nebula - a star has ejected its outer layers as it nears the end of its life. The central remnant white dwarf gives off extremely hard UV light which makes the shells of gas fluoresce. Blue/Green is Oxygen. Red is Hydrogen and Nitrogen. Yellow is an overlap of Green + Red.
At a diameter of 1 arc minute, it is only about 60 pixels across at this image scale. The central white dwarf which has a surface temp of about 100000c can just be seen.
Diameter is 1 arcminute
ZWO ASI2600MC 61 x 3 minute subs at gain 100, offset 50 at 0c.
Equinox ED 900mm f/7.5 scope x0.85 focal reducer.
IDAS P3 LPS 2" filter in focal reducer.
SkyWatcher EQ6 pro mount with Rowan belt drives.
Guided by PHD2 via PrimaLuce 240mm f/4 guidescope.
Atmospheric
Clear throughout. No subs lost.
Light pollution; 20.02 measured with Unihedron SQM (L)
Calibration
50 flats (EL panel at 1/4 second)
50 darks at 0c
50 bias at 0c and 1/16000s
Processing
PixInsight 1.8.8
Polar Alignment:
“Resume from Park” - I left the scope up from last time.
Error measured by PHD2= 0.2 arc minute.
RA drift + 1.27 arcsec/min
Dec drift +0.05 arcsec/min
Guiding:
PHD2 guiding with ZWO ASI290mm/PrimaLuce Lab 240/60mm guide scope. Multi-star guiding.
RA RMS error 0.61 arcsec.
Dec RMS error 0.64 arcsec.
Astrometry:
Resolution ............... 0.987 arcsec/px
Focal distance ........... 785.59 mm
Pixel size ............... 3.76 um
Field of view ............ 33' 10.2" x 26' 8.7"
Image center ............. RA: 18 53 35.937 Dec: +33 01 49.32
There was a little tilt between focuser draw tube and focal reducer which distorted the stars. I used Free Transform in Photoshop to distort and tilt the image back again!
Overall, I need to get the colour balance sorted out and probably use no more than about 2 minute exposures.
Planetary Nebula Messier 57 in Lyra
The Ring Nebula
A planetary nebula - a star has ejected its outer layers as it nears the end of its life. The central remnant white dwarf gives off extremely hard UV light which makes the shells of gas fluoresce. Blue/Green is Oxygen. Red is Hydrogen and Nitrogen. Yellow is an overlap of Green + Red.
At a diameter of 1 arc minute, it is only about 60 pixels across at this image scale. The central white dwarf which has a surface temp of about 100000c can just be seen.
Diameter is 1 arcminute
ZWO ASI2600MC 61 x 3 minute subs at gain 100, offset 50 at 0c.
Equinox ED 900mm f/7.5 scope x0.85 focal reducer.
IDAS P3 LPS 2" filter in focal reducer.
SkyWatcher EQ6 pro mount with Rowan belt drives.
Guided by PHD2 via PrimaLuce 240mm f/4 guidescope.
Atmospheric
Clear throughout. No subs lost.
Light pollution; 20.02 measured with Unihedron SQM (L)
Calibration
50 flats (EL panel at 1/4 second)
50 darks at 0c
50 bias at 0c and 1/16000s
Processing
PixInsight 1.8.8
Polar Alignment:
“Resume from Park” - I left the scope up from last time.
Error measured by PHD2= 0.2 arc minute.
RA drift + 1.27 arcsec/min
Dec drift +0.05 arcsec/min
Guiding:
PHD2 guiding with ZWO ASI290mm/PrimaLuce Lab 240/60mm guide scope. Multi-star guiding.
RA RMS error 0.61 arcsec.
Dec RMS error 0.64 arcsec.
Astrometry:
Resolution ............... 0.987 arcsec/px
Focal distance ........... 785.59 mm
Pixel size ............... 3.76 um
Field of view ............ 33' 10.2" x 26' 8.7"
Image center ............. RA: 18 53 35.937 Dec: +33 01 49.32
There was a little tilt between focuser draw tube and focal reducer which distorted the stars. I used Free Transform in Photoshop to distort and tilt the image back again!
Overall, I need to get the colour balance sorted out and probably use no more than about 2 minute exposures.