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Astrophotography by Bob Franke

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Sh2-73 - Nebula

 

Click the image for a larger view. (1676 x 1257 - 1.02 MB)

Instrument

Takahashi FSQ-106ED @ f/5.0 (530 mm F.L.) Captured at 2.1 arcsec/pixel.  Shown at 4.2 and 9.39 arcsec/pixel.

Mount

Losmandy G11 with Gemini L4 v1.0

Camera

SBIG STF-8300M Self Guiding Package w/ mono ST-i, using Baader LRGB filters.

Acquisition Data

4/30/2014 to 6/20/2014  Chino Valley, AZ

Exposure

Lum

585 min. (39 x 15 min.)  binned 1x1

Red

330 min. (22 x 15 min.)        "

Green

315 min. (21 x 15 min.)        "

Blue

435 min. (29 x 15 min.)        "

eXcalibrator RGB ratios are 1.00, 1.21 & 1.33

Software

  • CCDSoft, CCDStack, PixInsight & Photoshop CS6.

  • eXcalibrator v4.30 for (g:r) color balancing, using 314 stars from the SDSS-DR9 database.

  • CCDStack to calibrate all sub exposures, register and stack the color and create the RGB image.

  • PixInsight processing includes registering and stacking the luminance, gradient repair and non-linear stretching with HistogramTransformation.

  • PhotoShop for creating the LRGB and final touch up.

  • Noiseware 5, a PhotoShop plug-in.

Comment

North is to the top.
Sh2-73 is located in the constellation Hercules and was mistakenly included in the Sharpless catalog as an emission nebula. With no association with a nearby hot star, to ionize gas, we now know that the nebula is simply a molecular cloud. With its relatively high galactic latitude, about 45, the integrated light of the galaxy illuminates the nebula. Therefore, we can refer to Sh2-73 as an integrated flux nebula, as defined by Steve Mandel.

Additionally, the image has 48 visible quasars with a maximum red shift of 3.04.
Light Travel-Time : 11.202 Gyr
Age at Redshift 3.049881 : 2.097 Gyr
Age of Universe : 13.299 Gyr