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MetaGuide: M4 globular cluster in i'r'g' colors, with Atik 383L+ and EdgeHD 11 with reducer on CGE-Pro

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This is in semi-false Sloan colors, with i' -> red, r' -> green, g' -> blue. This gives a wider spectral range with no gaps. The colors were calibrated using custom code and UCAC4 field stars with AMASS Sloan photometry. The color calibration was deterministic and Photoshop CS6 was used only to apply levels. The result is consistent with a mostly red/orange cluster, corresponding to a very old system.

Imaging OpticsCelestron EdgeHD 11 with reducer at f/7
MountCelestron CGE-Pro
Guiding SoftwareMetaGuide with dithering from SGP
Guiding ModeOff-axis guiding with Hutech OAG5
Imaging CameraAtik 383L+
Guiding CameraQHY5l-ii
FocusSGP and RoboFocus on the primary focuser - no mirror locks used
Exposure Time3x20x1m Exposures kept short to avoid saturating
Image Scale0.57" per pixel
Raw FWHMDown to 1.5" in subs
Image ProcessingCalibration and stack in custom software, only levels in Photoshop CS6 - no other processing
Image Processing - OtherColors calibrated with Sloan magnitudes using UCAC4 field stars and custom code
Image AcquisitionSGP
Other SoftwarePECTool, TheSkyX Pro for best guidestar selection with field of view indicator (FOVI)
Other HardwarePyxis OAG Rotator for best guidestar, Telegizmos 365 cover, Long usb cable to outside setup
DateJuly 20-1, 2015
FilterAstrodon Sloan i', r', g'

Close up of single unprocessed sub showing < 1.5" fwhm in Maxim with 0.57" per pixel