9 March 2016
Ternate - Maluku Island - Indonesia
Institut d'Astrophysique de Paris - CNRS & Sorbonne Université
Mission directed by Serge Koutchmy
Images and processing by Christian Viladrich
Local circumstances
Location : North 0° 46' 31.2" - East 127° 22' 38.0. Measured to 16 m accuracy with GPS.
C1 : 23h 36 mn UT
C2 : 0h 51mn 37s UT
Max : 0h 52mn 57s UT
C3 : 0h 54mn 19s UT
Instrumentation
Telescope :
Skywatcher Maksutov 127 mm F/12 - Approximate focal length = 1500 mm - Measured Scale : 0.82 arcec/pixel (to be refined latter)
The optics were measured to lamda/8 P-V in red light : HASO-test.
The optical tube was insolated to reduce focus shift with temperature. Still, the focus changed by 0.5 mm between 9h20 mn and 9h42 mn TL (0h20mn UT and 0h42 mn UT). Focus accuracy is estimated to 0.1 mm (ie defocus aberration = lambda/6 P-V in red light).
Seeing conditions :
Excellent seeing during the partial phase. Seeing degradation due to passing thin clouds during totality.
Seeing to be evaluated more precisally later by estimation of Edge Spread Function on lunar limb.
Camera :
Basler 1920-155 with IMX 174 sensor - Field of view : 26.2 x 16.4 arcmin - Passive cooling with heat sink.
12 bits acquisition.
The acquisitions were made with the gain value set to minimum in order to maximise dynamic range and S/N max. Resulting dynamic range = 12.2 bits and S/N max = 7.5 bits.
Gamma value was set to 0.6.
Indicative IMX174 quantum efficiciency curve. Looks over-optimistic ... Source : Point Grey : http://www.ptgrey.com/support/downloads/10414?
Filter :
Astrodon Sloan r' filter generation 1 (yellow color). Square transmission from 555 nm to 696 nm :
Telescope mount : Unitron equatorial mount with model 128 electric drive aligned to the celestial pole (no field rotation during acquisition).
Processing :
- Correction of Fixed Pattern Noise and vigneting (and speckes of dust) by flat image.
- X /Y registration of video frames : not very accurate so far. To be improved latter. Use of one correlation zone (200 x 200 pixels) set on solar corona. Autostakkert 2 software. No frame selection, all frames of the video files are stacked to maximize S/N.
- Correction of radial gradient : Image = Image / Image convoluted by Gaussian (sigma 30 pixels).
- Visualisation : unsharp mask (sigma = 3 pixels, k = 30) or wavelet processing (Registax 6 software : Dyadic wavelet, k = 100 and 130 for scale 3, k = 50 for scale 5).
South limb
30 s acquisition centered on 00h51mn58s UT, 77 fps, 2332 frames acquired, stacked frames = 1700 first frames x 10 ms, moving thin clouds
"unsharp mask" version
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"wavelet" version
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West limb
30 s acquisition centered on 00h 52mn 59s UT, 25 fps, 750 frames acquired, stack frames = 750 frames x 40 ms, moving thin clouds
"unsharp mask" version
Click on image for full-resolution image
"wavelet" version
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North limb
30 s acquisition centered on 00h53mn55s UT, 66 fps, 2000 frames acquired, stack frames = 2000 frames x 15 ms, moving thin clouds
"unsharp mask" version
Click on image for full-resolution image
