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The Hole in the Trees Skybox | all galleries >> Deep Sky >> Planetary Nebulae > Sh 2-188
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Sh 2-188

PK128-04.1/Simeis 22/The Dolphin Nebula in Cassiopeia

Optics/Mount: CPC1100 with f6.3 Celestron reducer on a Milburn Wedge. Dec antibacklash set to 27/27. PEC on.
Camera: SXVR-H694
Exposure: 48 x 5 minutes Ha, 48 x 5 minutes OIII, 78 x 5 minutes SII, all bin 2x2
Filters: Astronomik 12nm OIII, Astrodon 5nm Ha and SII
Date: September 22 November 11, 2012

Imaging automation and capture: Sequence Generator Pro

Guiding Hardware: Flea 3, Taurus Tracker III off axis guider. Guiding scale 0.72 arcsec/pixel. 1 second guide exposures.
Guiding Software: PHD. Aggressiveness 80, Hysteresis 0, Minimum Move 0.9, Max RA 1000, Max Dec 600. Dec set to auto/resist switching. Dithering set to Extreme with Settle < 1.2. Calibration steps 8 x 9.
Guiding performance: HFR of subs ~1.5 arc seconds
Focusing: Rigel Systems GCUSB/nStep on stock C11 focuser
Light pollution: Bortle 8 (white zone, NELM about mag 4.5)
Conditions: Seeing generally average, transparency average
Image scale at capture: 1.2 arcsecs/pixel bin 2x2 = f/5.7
Scale of presentation: 1.2 arcsecs/pixel (50%)
Processing: Bad pixel map in Nebulosity 2, stacked with Deep Sky Stacker, post-processed with Photoshop CS2.


This ancient planetary nebula is either 600 parsecs or 965 parsecs away. It is very reminiscent of the Medusa Nebula. The central star is reported to be a very tiny blue star just inside the OIII zone.


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silverghost195112-Nov-2016 17:15
voted: This reminds me of somebody I knew.