After a couple of weeks of trial and error with rails and counterweights, I took my William Optics RedCat 250/51 mm telescope out for some first light images with the Sony a7iii. Conditions were typical under the Austin light dome, with occasional thin high clouds that ate about half my images. I was also photo-bombed by a train of satellites running through Orion. Mounting the telescope and camera, finding and framing my first target went smooth as can be. I then made a rookie mistake and balanced my rig spot on for the driven RA axis. I spent most of an hour trying to find the source of the tracking errors, before sliding my counterweight over to consistently take up the gear backlash. By then the Pleiades’s were loosing contrast and I switched to Orion.
I was getting cold so I set up to shoot a quick sequence of 30 second exposures at ISO 6400. The full frame image is vignetted and a bit dimmer in the corners, but stars look good and sharp across the image without noticeable color aberrations. The image below, taken from my home under a Bortle class 6 light dome, compares very favourably to a similar image I took in Terlingua, a Bortle class 1 dark sky site, with a Nikkor 300mm ED lens.
First light with a Williams Optics RedCat 250/51mm telescope and Sony a7iii. 28 minutes total of 56 30" exposures at ISO 1600. Bortle Class 6 light dome with fair transparency. Stacked in Nebulosity, with cropping and exposure adjustment in Photoshop.
Many of my exposures showed a train of satellites right through Orion, possibly the SpaceX Starlink satellite constellation. A crop of a typical frame is shown below.
My imaging setup is shown below:
The following crops from a sample 6000x4000 pixel full frame image are unprocessed other than the conversion from RAW to JPEG formatting and cropping:
Center sample image
Upper Left sample image
Upper Right sample image
Lower Left sample image
Lower Right sample image
Content created: 2019-12-23
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