John, that was a very nice description of what sounds like a great evening of observing. I did not view the fun frolic of Jovian moons, in fact I didn't even know about it. But reading your report brought back many good memories of viewing such things. Keep looking up! Mat -----Original Message----- From: John M. Craig <jmcraig@xmission.com> Sent: Friday, August 13, 2021 10:55 AM To: Utah Astronomy <utah-astronomy@mailman.xmission.com> Subject: [Utah-astronomy] Anyone else see the fun w/ Jupiter's moons on Wed night? I should perhaps have put a notice about this before it happened--sorry about that... For a good while before 11 pm on Wednesday night, only Jupiter's most distant Galilean moon, Calisto, was visible--or at least obvious (Ganymede and Io were occulted and Europa was transiting--I didn't have clear enough seeing or a big enough aperture to see Europa against the planet). Within about 7 minutes all 3 became visible as they appeared next to the limb of the planet. It was really fun to see. The amazing thing was that I've never seen any of the moons look anything but star-like (even in my best scopes--need to get the 10" RC Cass fixed up and working again). But with them right close to the limb of Jupiter, I was seeing them as disks at 125x with my low-budget 4" C102 achromat. Most unexpected! I think it may be a question of contrast--when they're distant from Jupiter, against the black of open space, my eyes (at least) do not see their disks: they look like bright stars. But as Ganymede and then Io emerged on one side (right close to each other almost in line with the N equatorial belt) you could definitely see that it took a fair amount of time before they became separated from the planet and then it was easy to see that Ganymede was substantially larger. Same effect with Europa: a bump on the limb, then a bigger bump, and finally a tiny disk. Amazing! Both my wife and daughter (not experienced observers) saw the moons as disks too. All this from my front yard--which is about as light polluted as it gets: we have one of the stupid acorn-style street lights just across from us and Orem is all Bortle Class 5 or worse. Hurray for bright things to see! I'm going to have to watch for times when the moons reappear from occultation and transit and check them out again. John _______________________________________________ Utah-Astronomy mailing list -- utah-astronomy@mailman.xmission.com https://eur04.safelinks.protection.outlook.com/?url=http%3A%2F%2Fmailman.xmission.com%2Fcgi-bin%2Fmailman%2Flistinfo%2Futah-astronomy&data=04%7C01%7Cmat.hutchings%40siemens-healthineers.com%7C5f75b070e96243193d2e08d95e7b2fd0%7C5dbf1add202a4b8d815bbf0fb024e033%7C0%7C0%7C637644705884299997%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&sdata=ICYNW2LyeHGYEb%2Bt%2FhGgFiZpZWvK2GBsBBaIQZk3RYc%3D&reserved=0 Send messages to the list to Utah-Astronomy@mailman.xmission.com The Utah-Astronomy mailing list is not affiliated with any astronomy club. To unsubscribe go to: https://eur04.safelinks.protection.outlook.com/?url=http%3A%2F%2Fmailman.xmission.com%2Fcgi-bin%2Fmailman%2Flistinfo%2Futah-astronomy&data=04%7C01%7Cmat.hutchings%40siemens-healthineers.com%7C5f75b070e96243193d2e08d95e7b2fd0%7C5dbf1add202a4b8d815bbf0fb024e033%7C0%7C0%7C637644705884299997%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&sdata=ICYNW2LyeHGYEb%2Bt%2FhGgFiZpZWvK2GBsBBaIQZk3RYc%3D&reserved=0 Then enter your email address in the space provided and click on "Unsubscribe or edit options".