Hemisphere:  Northern  ·  Constellation: Taurus (Tau)  ·  Contains:  Solar system body or event
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Comet Lovejoy C2014 Q2 from Mauna Kea, 



    
        

            Roger Clark
Comet Lovejoy C2014 Q2 from Mauna Kea
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Getting plate-solving status, please wait...
Comet Lovejoy C2014 Q2 from Mauna Kea, 



    
        

            Roger Clark
Comet Lovejoy C2014 Q2 from Mauna Kea
Powered byPixInsight

Technical card

Frames: 21x30" (10' 30")

Integration: 10' 30"


Basic astrometry details

Astrometry.net job: 3528567

RA center: 03h27m41s.8

DEC center: +17°0650

Pixel scale: 10.419 arcsec/pixel

Orientation: 333.083 degrees

Field radius: 2.412 degrees


Resolution: 1400x904

Description

Comet Lovejoy C/2014 Q2 shows an intricate ion tail On January 12, 2015. Image from Mauna Kea, Hawaii at the 9,200 foot level. This image was obtained with a Canon 7D Mark II 20-megapixel digital camera and 300 mm f/2.8 L IS II lens at f/2.8 and ISO 1600. No dark frame subtraction, no flat fields. Tracking with an Astrotrac and no guiding. This is 10.5 minutes total exposure (twenty one 30-second exposures).

During the approximately 16 minutes to make the exposures, the comet moved significantly. The 21

exposures were aligned in two ways: align on the comet head so the combined image had stars trailing, then align on the stars with the comet trailing. For the align on the comet image, the stars were

deleted, and for the align on the stars image, the comet was deleted, then the two images combined. To delete stars and not destroy detail in the comet's tail, I found that methods on the internet were

poor, so I deleted the stars using the healing brush in photoshop in a long and tedious process.

Removing the comet was easier: use the comet only image, blur it and subtract it from the image

aligned on the stars.

Modern DSLRs like the 7D Mark II include on sensor dark current suppression and low fixed pattern

noise at ISOs around 1600 and higher, making no need for dark frame subtraction. Modern raw converters correct for light fall-off and also correct for hot/dead/stuck pixels. This makes processing low light images easy: simply align and average.

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Sky plot

Sky plot

Histogram

Comet Lovejoy C2014 Q2 from Mauna Kea, 



    
        

            Roger Clark