Comet 46P/Wirtanen

46P/Wirtanen is a periodic comet, discovered in 1948, by the American astronomer Carl  Wirtanen. It is will make its closest approach eight days after this image was taken, on 16th December 2018, as it makes its way out almost as far as Jupiter’s orbit.

I was still suffering from the unreliable alignment of my SkyWatcher EQ6-R mount and had to manually locate the object.

Well…… to be honest, I found it with  the guidance of my friend John Rombi, who patiently aimed his laser pointer at the target while I battled with the controls, using my red dot finder from an unnatural position somewhere in the tangle of cables below my ‘scope.

Object Details:
Comet 46P/Wirtanen
Constellation: Eridanus.
Visual magnitude: +4.2, brightening.
Actual diameter of nucleus: 1 km
Actual diameter of coma: tbc
Period, 5.4 years.
Distance: 0.09 AU or 13.7 million km (for a comet, that’s close!)
Altitude: 59°.
Tail: not seen.

2018-12-08 Comet 46P Wirtanen 11.13 UTC
Image: JPL Small-Body Database Browser

Exposure: total 19 minutes over 25 frames.
Date: 2018-12-08.
Location: The Oaks, NSW.
Sky: semi-dark rural.
Cloud: no.
Moon: no.
Image acquisition software: SharpCap.
Image post-processing:  PIPP; Deep Sky Stacker > GIMP.
Cropping: slight.

Imaging telescope: Skywatcher Esprit 120ED Super APO triplet refractor.
Focal length: 840 mm, focal ratio: f/7.
Telescope mount: SkyWatcher EQ6-R.
Optical: field flattener yes; filter no.
Imaging camera: ZWO ASI 071 MC Pro.
Polar aligning method: QHYCCD PoleMaster.
Polar alignment error: 1′ 42″ (Synscan).
Guiding: none.

SharpCap Camera Settings:
[ZWO ASI071MC Pro]
Output Format=PNG files (*.png)
Capture Area=4944×3284
Colour Space=RGB24
Hardware Binning=Off
Turbo USB=80(Auto)
Frame Rate Limit=Maximum
Timestamp Frames=Off
White Bal (B)=61(Auto)
White Bal (R)=59(Auto)
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=On
Banding Threshold=35
Banding Suppression=0
Apply Flat=None
Subtract Dark=C:\Users\Roger\Desktop\SharpCap Captures\darks\ZWO ASI071MC Pro\RGB24@4944×3284\13.4s\gain_503\dark_5_frames_-14.1C_2018-12-07T11_17_24.fits
#Black Point
Display Black Point=0
#MidTone Point
Display MidTone Point=0.5
#White Point
Display White Point=1

Observing Notes:
Another test night for the EQ6R, following eleven months of unreliability. It failed to align again, with an errot of over 5° and will be returned to the manufacturer for the third time.

Image © R.Powell



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