I have dug a Stratoscope II view of Io from March 27, 1970. The original image was constructed from scanning 15 film images and stacking them (this was done at the time). UT time was somewhere between 0:15-2:00 (some of this would have been the time span of imagery, but part of the issue that creates the wide span here is contradictory sources. The phase angle was 290, if that helps. I based the reprojection at around 1:45, but I think I may have erred to the late side). I have posted my slightly enhanced version below, as well as a comparison with Voyager (the middle view is a degraded version of the Voyager view). Some albedo features are clearly consistent. I have also posted a link to a zip file where I put the image in the original form I got it in. There is also a stellar reference image. The resolution was determined to be about .1 arc seconds. The image is sensitive to roughly .38-.58 microns. Stratoscope II was a .9 meter balloon-borne telescope that took several flights in the 1960s and 70s (Stratoscope I was a balloon-borne solar telescope).
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