IC 405 The Flaming Star nebula in Auriga
Most astronomers know M42, the Orion Nebula that has 4 bright O class stars - the Trapezium. It’s thought there were originally 6 stars there- 2 were thrown out by gravity and travelled in opposite directions. One of these 2 runaways is the star AE Auriga. It’s currently passing through a dust and hydrogen cloud and illuminating both. The dust clouds reflect the blue light of the giant O class star and the hydrogen gas fluoresces red. The nebula is known as the Flaming Star nebula.
480/80mm f/6 Altair Starwave refractor. Altair Planostar FF.
Astro-modified Canon 80D at ISO400, IDAS clip-in LPS D2 filter, 34 x 5 minute subs.
NEQ6 pro mount with Rowan belt drives -2 star align.
Mini-PC with WiFi
Mount WiFi control with ASCOM/AstroPhotography Tool
Camera WiFi control with Backyard EOS
42 dark frames
40 flat frames (electroluminescent panel @ 1/40s)
Master bias from library.
Post processed in PixInsight 1.8 and Photoshop
Local parameters:
Temp: 3.2- 3.7c
Humidity: 84- 91%
Pressure: 1011 kPa
Camera Sensor Temp: 10-13c
Light Pollution and Weather:
SQM (L) at start of session (2108 hrs UT) =19.85 mag/arcsec2.
SQM (L) at end of session (0043 hrs UT) = 20.11 mag/arcsec2.
Clear, very occasional cloud. Some smoke from neighbour's chimney!
Polar Alignment:
QHY Polemaster alignment -
Error measured by PHD2=0 .8 arc minute.
RA drift + 1.64 arcsec/min
Dec drift -0.20 arcsec/min
Guiding:
PHD2 guiding with ZWO ASI290mm/Altair Starwave 206/50mm guider. Dithered.
RA RMS error 0.75 arcsec, peak error 2.66 arcsec
Dec RMS error 0.52 arcsec, peak error 2.17 arcsec
Astrometry:
Center (RA): 05h 15m 56.380s
Center (Dec): +34° 23' 41.347"
Size: 1.18 x 1.07 deg
Pixel scale: 1.59 arcsec/pixel
I’ve always had a problem with my scope - bright stars have been shaped like an “iron cross”. Initially I wondered if it was related to a rectangular LPS filter but changing to a round filter didn’t help. Some articles suggested it could be a diffraction problem from clips holding baffles or spacers in but I couldn’t see any. The solution to that problem is to stop the scope down but that would make it slower than f/6.
I recently found an article suggesting it was “pinched optics” - where the screws holding the lenses in are too tight and distort the optics. It’s commonly seen with reflectors, where the mirror is held by 3 screws giving a triangular diffraction pattern.
On looking at my scope, there were 4 sets of screws holding the lens elements in place. I have gently loosened these and the “pinched” effect has gone away but I’ve developed an eccentric halo artefact now that is worse towards the edge of the chip. This might be from my new D2 Clip-in LPS filter - I can replace this with a 2 inch filter that screws into the front end of my focal flattener.
IC 405 The Flaming Star nebula in Auriga
Most astronomers know M42, the Orion Nebula that has 4 bright O class stars - the Trapezium. It’s thought there were originally 6 stars there- 2 were thrown out by gravity and travelled in opposite directions. One of these 2 runaways is the star AE Auriga. It’s currently passing through a dust and hydrogen cloud and illuminating both. The dust clouds reflect the blue light of the giant O class star and the hydrogen gas fluoresces red. The nebula is known as the Flaming Star nebula.
480/80mm f/6 Altair Starwave refractor. Altair Planostar FF.
Astro-modified Canon 80D at ISO400, IDAS clip-in LPS D2 filter, 34 x 5 minute subs.
NEQ6 pro mount with Rowan belt drives -2 star align.
Mini-PC with WiFi
Mount WiFi control with ASCOM/AstroPhotography Tool
Camera WiFi control with Backyard EOS
42 dark frames
40 flat frames (electroluminescent panel @ 1/40s)
Master bias from library.
Post processed in PixInsight 1.8 and Photoshop
Local parameters:
Temp: 3.2- 3.7c
Humidity: 84- 91%
Pressure: 1011 kPa
Camera Sensor Temp: 10-13c
Light Pollution and Weather:
SQM (L) at start of session (2108 hrs UT) =19.85 mag/arcsec2.
SQM (L) at end of session (0043 hrs UT) = 20.11 mag/arcsec2.
Clear, very occasional cloud. Some smoke from neighbour's chimney!
Polar Alignment:
QHY Polemaster alignment -
Error measured by PHD2=0 .8 arc minute.
RA drift + 1.64 arcsec/min
Dec drift -0.20 arcsec/min
Guiding:
PHD2 guiding with ZWO ASI290mm/Altair Starwave 206/50mm guider. Dithered.
RA RMS error 0.75 arcsec, peak error 2.66 arcsec
Dec RMS error 0.52 arcsec, peak error 2.17 arcsec
Astrometry:
Center (RA): 05h 15m 56.380s
Center (Dec): +34° 23' 41.347"
Size: 1.18 x 1.07 deg
Pixel scale: 1.59 arcsec/pixel
I’ve always had a problem with my scope - bright stars have been shaped like an “iron cross”. Initially I wondered if it was related to a rectangular LPS filter but changing to a round filter didn’t help. Some articles suggested it could be a diffraction problem from clips holding baffles or spacers in but I couldn’t see any. The solution to that problem is to stop the scope down but that would make it slower than f/6.
I recently found an article suggesting it was “pinched optics” - where the screws holding the lenses in are too tight and distort the optics. It’s commonly seen with reflectors, where the mirror is held by 3 screws giving a triangular diffraction pattern.
On looking at my scope, there were 4 sets of screws holding the lens elements in place. I have gently loosened these and the “pinched” effect has gone away but I’ve developed an eccentric halo artefact now that is worse towards the edge of the chip. This might be from my new D2 Clip-in LPS filter - I can replace this with a 2 inch filter that screws into the front end of my focal flattener.