M13 (Her)

M13 (Her)

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Date/Site: 29. May 2020, remote observatory on the AAR club's site in Presberg
Exposure/
Filters:
R: 19 x 180 seconds,
G: 18 x 180 seconds,
B: 11 x 180 seconds (-20°C)
Camera: QSI 632 with Astronomik Type II-filters
Optics/
Instrument:
250mm f/4 Newton with Baader RCC1 on 10Micron GM1000 HPS
unguided,
focusing: Microtouch and FocusMax,
data acquired remotely using CCD-Commander and MaximDL 6,
calibration and processing: PixInsight 1.8

Compare this with the image done some days later with the ASI071 and the 40cm-Newton.
 
 
A somewhat older image of this classic:

M13 (Her)

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Date/Site: July 8th, 2010, AAR-observatory in Presberg
Exposure/
Filter:
R: 7 x 200 seconds, G: 4 x 200 seconds, B: 3 x 200 seconds (-15°C)
Camera: SBIG ST10XME, CFW9 with SBIG LRGB-filters, AO-8
Optics/
Instrument:
26cm-Newton on Gemini 41 Observatory
Focusing with Robofocus
Darks, flats, deblooming, alignment and stacking: MaximDL 5,
Levels and curves: Photoshop CS3.

After the purchase of an active optics standard objects were the choice of the evening.
As long as the AO-8 can guide on a sufficiently bright star frames are of a quality unknown before. Starlight does not get smeared, so even moderately bright stars get saturated. I had to discard all L-frames of M13 because the stars in the core of the cluster bloomed – with only 200 seconds integration.
The AO produces relatively high-frequency vibrations while calibrating and localizing a guiding star. The Newton's tube is rotated inwards, so the focuser always is turned towards the mount. But then it points more or less downwards and camera and accessories pull on it. The rapid movements of the optical window during localizing and tracking cause the otherwise quite sturdy focuser to loose a bit of its grip. Focusing was necessary more often.
The MPCC coma-corrector cannot work in combination with the AO-8, so a bit of distortion is visible in the corners of the frame.
 

© Friedhelm Hübner, last revision:  17.01.2021