Contains: Comet, NGC 281, The star ηCas
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Comet 8P (Tuttle) close to NGC 281

Technical card

Imaging telescope or lens: Televue TV-85

Imaging camera: canon 450D

Mounts: Losmandy GM-810 Micron 1000 HPS

Focal reducer: TeleVue TRF-2008 0.8x

Filter: Astronomik L UV-IR Block Clip-in

Resolution: 2350x1292

Dates: Dec. 22, 2007Dec. 6, 2013Dec. 30, 2013

88x300" ISO1600
117x120" ISO800

Integration: 11.2 hours

Darks: ~32

Flats: ~25

Flat darks: ~25

Avg. Moon age: 14.75 days

Avg. Moon phase: 39.70% job: 176826

RA center: 13.240 degrees

DEC center: 57.019 degrees

Pixel scale: 4.503 arcsec/pixel

Orientation: -94.093 degrees

Field radius: 1.677 degrees

Locations: Dark Sky Site, Kirby Malzeard, North Yorkshire, United Kingdom


The original version of this image was shot 22 December 2007 using an unmoddified Canon 10D with a TV85 scope (with focal reducer) on a Losmandy GM/8 mount using 2 minute exposures at ISO 800. Because the original camera poorly captured NGC 281, I reshot the background stars and nebular last winter using a Canon 450D (modified) on the same TV85 scope but on an 10Micron GM1000HPS mount using unguided 5 minute exposures at ISO1600 in two sessions to create a two frame mosaic to better balance the composition. (frame overlap was 60%).

Calibration and stacking was done using DSS on the two separate background groups. The background mosaic was constructed using Autopano Pro with a custom warp map to ensure the projection transformations where centred in the final frame.

The comet was isolated from the original 117 frame stack by aligning all frames on the comet and using a sigma-kappa rejection method to remove the stars (kappa 1.15, iterations 10).

Finally the stacked comet image was resized (Canon 10D to 450D scaling is 141.8%) and reorientated using a reference frame to match the background image and composed into the background image using a Gaussian masking and screen blending technique (not lighten blending as that does not handle coma transparency)



Tony Cook

Sky plot

Sky plot


Comet 8P (Tuttle) close to NGC 281, Tony Cook

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Comets Imaging
Cloudy Nights