Our main imaging location is at the front of the house where the celestial pole is obscured by the house. The mount we use is a Celestron AVX mount and some time ago we performed an any-star-polar alignment. Then we placed marks on the ground so that we would be able to place the mount back in the same position in the future.
Marks on the concrete slab to enable positioning of the mount
This arrangement works very well, but of course it is not absolutely precise. For our main task of testing during the development of AstroDMx Capture, the slight imprecision is an advantage because the location and centering of deep sky objects requires plate-solving rather than high polar-alignment precision.
The control of the mount is by AstroDMx Capture via an INDI server running on the imaging computer indoors. The camera is also controlled by AstroDMx Capture.
The problem arises when we wish to image the Moon. In this case the imprecise polar-alignment leads to the Moon being missed. Moreover, with the cameras used for Lunar imaging, plate solving is often not as easy as it is with deep sky imaging cameras, particularly under the bright glare of the Moon. Therefore another solution was used to locate the Moon.
If the finder-scope shoe was perfectly co-aligned with the optical axis of the scope, then it might be possible to use a guide-scope such as the SVBONY SV165, which has no lateral movement controls. The SV165 has a focal length of 120mm and an aperture of 30mm. It has a wide field of view which makes it suitable as a guide scope but wide enough to be able to pick up the Moon if it has been missed by the Main scope. The Ekinox ED 80mm rafractor that we use for some of our lunar imaging has a slightly offset finder-scope shoe, so using an SV165 guidescope is not possible. Instead, a low cost photographic gimbal was used so that in advance of the lunar imaging session the gimbal controls could be used to precisely co-align the SV165 with the Ekinox 80mm. A more conventional guide scope with six-point aiming controls can be used but we have found it to be too easy to disturb the co-alignment during placing the scope on the mount. The gimbal is much more resilient in this respect.
The gimbal plus SV165 guide-scope with a QHY5L-II-M guide-camera mounted on the Ekinox ED 80mm refractor.
It is possible to run two instances of AstroDMx Capture on the same computer, or one instance on one computer running the imaging camera and another instance on a separate computer running the guide camera, a QHY5L-II-M . When AstroDMx Capture sent the scope to the Moon; as expected, the main scope missed the Moon but the Moon was captured in the field of view of the SV165/QHY5L-II-M combination. The AstroDMx Capture mount nudge controls could then be used to centre the Moon in the SV165/QHY5L-II-M field of view.
The Moon Centred in the field of view of the second instance of AstroDMx Capture running the SV165/QHY5L-II-M combination
When the Moon had been centred in the field of view of the second instance of AstroDMx Capture, it was now in the field of view of the First instance with the SVBONY SC715C main imaging camera. The Moon could then be nudged into the exact position for imaging.
Two overlapping 2000-frame RAW SER files of the Moon were imaged by AstroDMx Capture.
The best 75% of the frames in the SER files were debayered and stacked in Autostakkert!4, wavelet sharpened and white balanced in waveSharp. The two overlapping panes were stitched and cropped in MS Image Composite Editor. The image was further processed in the Gimp 2.10 and ACDSee.
99% Moon
