Forum Replies Created
-
AuthorPosts
-
Alan SnookParticipant
Much appreciated Folks, that’s all most helpful. Certainly Stellarium seemed the most promising (least worst?) of the 3 packages I tried initially. I spent a half-day on it yesterday trawling through the 420-page instruction manual and so far I’ve moved the output to about half-way to where I’d like it. I found the planetary satellite displays you mentioned, I can see that being useful. It would be good to keep Megastar going if possible so I’ll try Emil’s dowload, and check out the Aladin link too. Much appreciated. Alan.
Alan SnookParticipantS&T didn’t worry about making a political statement when they took a cheap shot (Dec 2020 p21) at Patrick Moore. They criticised Patrick’s politcal and social opinions which were not especially unusual for his time. I felt this was not simply a failure by the author but a full editorial failure. If the author could not write the article without denigration then it should not have been written at all. I doubt they would have attacked a living person or an American citizen in this way. I wrote to S&T but received no response. Much later they printed (Apr 2021 p6) a letter from a British Columbia reader which did little more than merely note the aberration. This wasn’t sufficient retraction in my book and so they have lost a 25-year subscriber. For these reasons I counsel all of you to shun S&T.
Alan SnookParticipantI used 3M 4200 marine adhesive sealant when I set up the 3.5m dome (see small ads in the back of JBAA Dec 2019). This was at the recommendation of the dome manufacturer – Sirius in Australia. Get it from some chandlers. The bottom edge of the GRP panels was abraded a little with wet ‘n’ dry to key the surface. I did the work in Sept 2020 and so far it has kept the water out. I got through three tubes of the stuff. However I fear your joint may now be contaminated with mastic, window sealant etc; you will surely need to remove all traces from both the GRP walls and the concrete before using the 3M product or it will be good money after bad,
Alan SnookParticipantHaving extracted more than 40 famous astronomers from the memory but still left with gaps, the penny finally dropped last night. I am looking forward to reading a paper in a future Journal detailing the previously unknown astronomical works of Messrs Alkali Stone, Ten Elite Brains, Harry Can Find Me and Crime Or Fine. Aside from that, many thanks to the contributors for an excellent selection of brain teasers. I am attempting it without any research, just staring at questions and worrying them to death. Just the job for those of us suddenly in Tier Alcatraz.
Alan SnookParticipantThanks Dominic, with your pointers and a couple of sessions with a wet towel I’ve got up to speed with how it all works. It’s a bit of an eye-opener to discover that the format of these 2-line-elements harks back to the 80-line punched cards of the 1960’s including only two digits for the year!
Alan SnookParticipantHe’s used a Baader 8.5nm CCD narrow band filter. The graph shows it is fairly transparent beyond 1,050nm.
Alan
Alan SnookParticipantMany thanks folks, I’ll pass those comment back no and let you know what flows from that.
Sorry about all the rubbish lines in my first post. I don’t know why it’s done that.
Alan
Alan SnookParticipantQuoting from ‘The Modern Moon’ by Charles Wood, page 93 “Surprisingly not much changes until the impact angle is less than 45 degrees (measured from horizontal). But at shallower angles the crater become increasingly elongated in the direction of projectile travel, and portions of the projectile ricochet and gouge out a series of small pits downrange from the main crater. As the impact angle decreases the ejecta and rays undergo even more pronounced changes than the craters do. When impact angle is less than 15 degrees the ejecta pattern becomes elongated in the downrange direction and a ‘forbidden zone’, where no ejecta appears, develops in the uprange direction. For grazing impacts of just a few degrees the rays go sideways only, producing a butterfly wing pattern. Amazingly, examples of all these exotic ejecta patterns can be found on the Moon, Mars, and Venus. Thus, the asymmetric Proclus ejecta and rays were formed by an oblique impact. … Palus Somni is simply the ray-excluded zone of the Proclus oblique impact.”
On page 94 he goes on to explain how Messier & Messier A were formed by a grazing impact in the range 1 to 5 degrees by a projectile coming from the east. Messier is very elongated, 14 x 6 km. He continues “Bigger craters formed obliquely too, look at the ray patterns of Proclus, Kepler & Tycho. Mare Crisium is simply a larger version of Proclus and Messier. The basin’s elongated shape, low rims on the east and west, and butterfly-wing-like distribution of ejecta to the north and south are all consistent with the low angel impact of an asteroid or comet approaching from the west.” (n.b. Crisium is longer EW than NS, it doesn’t look that way to us because of limb foreshortening.)
Alan SnookParticipantSetting up in the garden at 9.30pm yesterday, glancing up I was taken aback to see half a dozen bright lights overhead, sweeping west to east in follow-my-leader order at 20 degree separation. And they kept coming. I lost count. Their track was from Procyon, between Leo & Leo Minor, and away through Bootes. Ten minutes later they were still coming. Every light was brighter than any of the seven stars of the Plough. To think once we made a big thing of seeing the old Echo balloon satellite. Dear o dear, human’s ability to screw things up in innovative new ways knows no limit. It’s just as well we get old and die.
Alan SnookParticipantGood 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.
Alan SnookParticipantHi 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
Alan SnookParticipantI 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.
Alan SnookParticipantI 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.
Alan SnookParticipantThanks Xilman & Bill. I’ve consolidated my scribbles and added written notes, here it is for what its worth. I’ll try out NASA’s Dial a Moon thing this eve and see if that sheds any light.
-
AuthorPosts