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Trifid Nebula from Montebello OSP July 2014, Stephen Migol
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Trifid Nebula from Montebello OSP July 2014

Trifid Nebula from Montebello OSP July 2014, Stephen Migol
Powered byPixInsight

Trifid Nebula from Montebello OSP July 2014

Equipment

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Acquisition details

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Description

Trifid Nebula from Montebello OSP at the end of July.

This is a selection from a larger image which includes M8 as well. Wanted to feature this picture as a contribution to the Cloudy Nights DSLR astrophoto forum competition for July 2014 for the M20 subject.

Taken with the Pentax K10D (modified and cooled) DSLR on the Stellarvue SV4 telescope. Guided with Orion SSAG on the Stellarvue SV70ED. IDAS HEUIB II filter was used along with the SSF6 flattener.

Stack of 19 subexposures of 1200 seconds each for a total of 6 hours and 20 minutes of integration over 3 nights (July 23, 29, 30). Calibrated with Maxim 5.25 with 64 bias, 9-18 darks (depending on temperature), and 24-64 flats (depending on date). Stacked in DSS with custom rectangle and 2x drizzle stacked. Processed in PixInsight.

Steps in PI were:

Crop to remove ragged edge, Masked stretch script, Histogram stretch to reset black point, Luminance masked noise reduction with the Denoise tool, Masked curves to darken and desaturate the background, and Unsharp mask on the brightest parts.

Exported to Lightroom for final touch (desaturate blue and red a little) and upload.

Note the rings around the brighter stars. The offset rings are from reflections inside the coverglass on the CCD. Because the larger image was framed to balance M8 and M20, the crop is not centered. Thus, the reflections are not centered.

I'm happy enough with this image, I'll revisit it with the whole frame and possibly tone down the blues a bit.

Here's the plate solve from PI:

Referentiation Matrix (Gnomonic projection = Matrix * Coords[x,y]):

+2.63494e-006 -0.000265052 +0.340236

+0.000265051 +2.03983e-006 -0.394048

+0 +0 +1

Projection origin.. [1476.697373 1298.340413]pix -> [RA:+18 02 33.19 Dec:-23 00 10.71]

Resolution ........ 0.954 arcsec/pix

Rotation .......... 90.506 deg

Focal ............. 1307.78 mm

Pixel size ........ 6.05 um

Field of view ..... 46' 56.8" x 41' 17.1"

Image center ...... RA: 18 02 33.209 Dec: -23 00 11.38

Image bounds:

top-left ....... RA: 18 04 02.155 Dec: -23 23 47.69

top-right ...... RA: 18 04 03.663 Dec: -22 36 50.97

bottom-left .... RA: 18 01 02.233 Dec: -23 23 28.55

bottom-right ... RA: 18 01 04.780 Dec: -22 36 31.98

Comments

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Sky plot

Histogram

Trifid Nebula from Montebello OSP July 2014, Stephen Migol