This article covers the use of the SV705C with two telescopes to investigate its performance as a Lunar imager and also a planetary imager using AstroDMx Capture.
Using a Skymax 127 Maksutov
The first test used a motor-focus modified Skymax 127 Maksutov mounted on a Celestron AVX mount. The seeing was poor due to the jet stream and also the Moon was rather low in the sky at this latitude in the UK.
It is notoriously difficult to judge focus when the seeing is bad. It is best not to rely on judgement but rather to focus on a bright star using a Bahtinov Mask. As the Moon, the planets and the stars are all at optical infinity, this provides an objective way of achieving the best focus.
Seeing limited the magnification that could be used for imaging the planet Jupiter, so the SV705C, fitted with a UV/IR cut filter was placed at the focus of the scope and two SER files were captured, one with a wide field, to capture the planet and the four Galilean moons.
Screenshot of AstroDMx Capture capturing a SER file exposed for the Galilean moons.
Screenshot of AstroDMx Capture with an arbitrary ROI capturing a SER file of Jupiter and exposed for the planet.
NB The images in the screenshots are actually at exactly the same scale. The first screenshot has the preview window at 36% full size, whereas the second screenshot has the preview at 100% because it is a relatively small ROI.
The two images were combined to produce an image of Jupiter and the four Galilean moons.
Left to right Callisto, Io, Jupiter, Europa and Ganemede
Imaging the Moon
Six overlapping panes of the 80.5% waxing Moon were imaged as 1500 frame SER files.
Some examples are given below.
AstroDMx Capture saving a SER file of the Mare Tranquilitatis, Serenitatis and Palus Somni region of the Moon
AstroDMx Capture saving a SER file of the Tycho, Clavius region of the Moon.
Final image of the Copernicus region
Final image of the Plato, Sinus Iridum region
The 6 final images were stitched together into a 6 pane mosaic of the Moon
6 Pane Mosaic of the Moon
Using a Refractor
Another test of the SV705C OSC camera as a planetary imager was done using an F=440mm, 80mm ED refractor mounted on a Celestron AVX mount. The camera was placed at the focus of the refractor. The mount was connected to a Raspberry Pi computer running an INDI server. The Pegasus FocusCube V2 motor focuser was also connected to the Raspberry Pi. AstroDMx Capture communicated with the INDI server via WiFi.
AstroDMx Capture was used to unpark the mount and to send the mount/scope to Deneb without prior alignment. The focuser was controlled by AstroDMx Capture and the stars were brought into focus. Then AstroDMx Capture captured an image and plate-solved and centred Deneb in the field of view. Then a Bahtinov mask was used and AstroDMx Capture brought the star into perfect focus.
The Mount/scope was then sent to the Moon and the nudge functions in AstroDMx Capture were used to centre the Moon in the field of view.
AstroDMx Capture was used to draw an arbitrary ROI around the Moon, which fitted nicely into the field of view.
AstroDMx Capture was used to capture a 2000 frame SER file of the optimally focused 95.1% waxing Moon
The best 75% of frames were stacked in Autostakkert! and the resulting image post-processed in the Gimp 2.10
95.1% waxing Moon
95.1% waxing Moon slightly chroma enhanced to accentuate mineralogical differences on the lunar surface
The SVBONY SV705C OSC camera performed well as a lunar imager whether at high resolution using a long focal length Maksutov or captured as a single disk using a short focal length ED refractor.
The use of a Bahtinov mask on a bright star to achieve optimal focus even during conditions of poor seeing proved this to be a reliable method of focusing on the Moon (and also a planet) without having to use judgement to decide whether optimal focus had been achieved. This is probably the best way to achieve optimal focus, whatever the seeing conditions.
