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Good to see the scale of the reduction in the hard data from the meteor cameras noted above. I just tried Flightradar24 but there’s something amiss, the map appears but no aircraft at all, yet I can hear one overhead. Maybe the site is swamped by the at-home cautionary-quarantiners looking for amusement.
Hi Peter, the jet in M87 is number 152 in the Arp Atlas of Peculiar Galaxies. I’ve tried for it several times with not a sniff of success. I’m using a 50cm f4.1 dob. There is no drive so in practice my highest usable magnification is x415. In Howard’s article he’s talking about x600 to x700. In the Kanipe/Webb book about the Arp objects, on p303 it cites an observation by the late Barbara Wilson (of AINTNO 100 fame) also using a 20-inch f4, at x340 and x410. She noted “Jet visible running out of core. Difficult. Requires excellent seeing and transparent skies.” This comes back to Owen’s point – the American’s have a much easier time of it. In the Arizona desert and Bryce Canyon in Utah with the unaided eye I’ve seen mag 6 stars as they clear the horizon. At home here, I’m lucky to see anything below Epsilon CMa even when it’s near culmination! Try for the jet on one of those rare nights when anything seems possible.
Alan
I appreciate your take on this Paul. Our different interpretations are certainly a measure of how the appearance of the ground changes hugely with the angle of the Sun. What I’ve done now is transfer my sketch to tracing paper so I can better test the match-up with my downloaded NASA Moon and with your screenshot. If I anchor the sketch at Anaxagoras and adjust the scale to match up the “dark floored crater” with Scoresby, it pushes the limb to the wrong place and the wrong angle. The east end of the “dark feature” is pushed off the disk. Conversely if I scale to match that squashed figure-8 in the sketch to Challis & Main then the limb is spot on. But that leaves me wondering why I didn’t note anything of Scoresby. On the both the virtual Moon and the old-school Hatfield Photographic Atlas it’s a prominent feature! Sun angle again I guess. Your interpretation has the merit of explaining more of the small bright patches.
The tracing paper overlay also suggests the E end of the “dark feature” is due to the crater de Sitter at 80 degrees N but the match is not convincing. Now better informed, I think I need to look out for the next favourable libration and have another go.
I have used the NASA link in Bill’s post to generate the libration-corrected map (what a magic tool!), scaled it to match my sketch which I then overlaid. That’s blown away a lot of the fog and a fair bit of the sketch makes sense now. I’ve uploaded my conclusions. The dark plain right on the limb remains a puzzle however.
