Collecting Photons

M13 Hercules

Wide Field

Objects: M13 (globular cluster); LBN 133, 134 (dust and reflection nebulae)

Constellation: Hercules

Coordinates of field center: 16h 42m +36° 26'

Notes: one of my earliest images almost fully automatized with CCDcommander, the Sky and Focus Max.

Telescope and camera: ASA 10', f 3.6; SBIG STL 11000.

Exposure: Luminance 70x4'; R, 18x5'; B 16x5'; G 17x4'. About 8.6 hrs total.

Date: 4 nights on 23, 24, 25, 28-05-2010.

Software used: acquisition, CCDsoft, FocusMax, the Sky VI for plate solving, CCDcommander for automation. Calibration; registration and stacking: CCDstack, Registar; processing: PixInsight, Photoshop CS.

Processing notes: M13 is characterized by an extremely bright central nucleus. Here the brightest stars saturate the luminance channel in only 4' and I needed to use a synthetic luminance obtained from the RGB data to rebuild these stars. This is why I used such short sub-exposures. The entire dynamic range was reconstructed by employing different degrees of stretching blended through appropriate luminance masks to allow a reasonable representation of the nucleus and of the most peripheral stars. During those nights the seeing was pretty good, FocusMax acted well and the deconvolution of the L channels brought down the FWHM to about 1.9 pixel, which is pretty unusually good at my site.

Wide field

1600x1116

This is the almost full frame image, with only minor crops along the edges because of dithering. The field is filled with tiny galaxies, some of them showing some interesting features. The most obvious is north of the cluster the spiral NGC6207 (3.0' x 1.2').

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Send anything that comes to mind to Gimmi Ratto gimmi@in.cnr.it