Instrument

12.5" RCOS @ ~ f/9 (2880 mm fl) at 0.64 arcsec/pixel. Shown at  1.27 & 3.05 arcsec/pixel.

Mount

Paramount ME

Camera

SBIG STL-11000 w/ FW8 filter wheel & AstroDon Gen-2 Ha 6nm and LRGB filters.

Acquisition Data

12/12/2017 to 2/7/2019 Chino Valley, AZ. with CCD Commander & CCDSoft.  AOL guided

Exposure

eXcalibrator RGB ratios are 1.00, 1.35 & 1.22

Software & Processing Notes

• CCDSoft, CCDStack, PixInsight, Photoshop CS6.

• eXcalibrator v6.2 for (g:r),(b:r) color balancing, using 700 stars from the Pan-STARRS database.

• CCDBand-Aid to repair KAI-11000M vertical bars.

• CCDStack to calibrate & normalize all sub exposures and to data reject and mean combine the color data.

• PixInsight to register, data  reject, mean combine the luminance and Ha sub exposures, create the LRGB image, gradient removal, non-linear stretching with HistogramTransformation and green cast removal with SCNR .

• PhotoShop for adding the Ha data, additional background neutralization and background smoothing.  The second image uses the red and blue plates from the POSS2 survey. Noel Carboni's action created the synthetic green channel.

• Noiseware 5, a PhotoShop plug-in.

Comment

Shown rotated 160° counter clockwise.

There is almost no information about this nebula except that it is classified as a reflection nebula in the Simbad database. Simbad notes the small orange area, at the top of the nebula, as a star cluster and a young stellar object.

Johann Dorschner and Joachim Gürtler added this object to their catalog sometime around 1963. Beverly Lynds cataloged the object as LBN 818 in the early 1960's. Lynds discovered the object while examining the Palomar Sky Survey plates (POSS1). It is unlikely that Dorschner and Gürtler used the POSS1 images.

An Internet search found no images of the nebula. It only seems to show up on sky surveys. So, this may be the only image that specifically targets DG66.

Further processing notes:
The FPO background had extreme color gradients. The mouse over image shows a colorless background. Adding the highly stretched Ha data revealed the nebula's structure.

The POSS2 image appeared to have proper background color. So, the POSS2 background and nebula were added to the FPO image with PhotoShop's lighten blend mode. This gave a more correct background and better highlighted the bright spot at the upper left corner of the nebula.

The finished FPO image shows more structure. However, the POSS2 image is probably a more accurate general representation, but with incorrect star color.