Likewise and always good to hear from you. I extended your script to attempt to determine what this moon might look like from the points we have defined and their antipodes. Any observation also needs a height which I have set at the height of Boise. I threw in the planets Venus, Saturn, and Jupiter too, as they seem to be part of the big celestial show for the next few days.

I also use Log::Log4perl, because these data would overwhelm STDOUT. The .conf files are from the examples.

My first question is how the azimuth is defined. Astro::Coord is suuuper complicated. Looks like there's even fortran in there. Physicists and mathematicians do things differently in a lot of settings. I can't tell if my results are wrong or untransformed.

The same time is used for 4 different places. (Not that they're gleichzeitig.) I'll put the log and then the source between readmore tags:

One thing I noticed is that these data are very sensitive to altitude of the defined observer. A person at 817 meters above the Scylla would have a much better view of rising and setting planets. Is there any way to figure out what a reasonable guesstimate is of altitude given latitude and longitude?

How long does the moon's transit from Venus to Jupiter take?

How can I determine that a priori? I know that I can bound the value in DateTime with output from the original post. Can one loop over this interval with the methods of DateTime adding the duration of a second and then checking values. A month isn't a lot of seconds for a computer.

Great additions Aldebaran!

DateTime can do date arithmetic as simply as:

my $dt = DateTime->new(
    year      => 2021,
    month     => 4,
    day       => 5,
    hour      => 2,
    time_zone => 'Africa/Nairobi',
);
# or, create a DateTime object from an ISO timestring
my $isostr = '2021-10-11T11:13:57';
my $dt = DateTime::Format::ISO8601->parse_datetime($isostr);
# add a second to what $dt currently holds
$dt->add(seconds => 1);
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Regarding your other questions, I have no clue about celestial mechanics. Nonetheless I have whipped up a Perl sub to get you the elevation given coordinates. It uses a site which I am not sure if they would like people using their services in this way. So with that in mind:

# usage:
# my $elevation = get_elevation_from_coordinates(15.6325, 38.245833, 0
+);
sub get_elevation_from_coordinates {
    my ($lat, $lon, $debug) = @_;

    $debug //= 0;

    my $ua = LWP::UserAgent->new(
        agent => 'Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100
+101 Firefox/78.0',
    );

    my $response;
    my $payload =
        'latitude='.$lat
        .'&longitude='.$lon
        .'&application_max_assets_mtime=1559625591'
    ;
    my $payloadlen = length($payload);
        # this request was translated from Curl command-line
        # by [Corion]'s https://corion.net/curl2lwp.psgi
    my $req = HTTP::Request->new(
        'POST' => 'https://www.mapcoordinates.net/admin/component/edit
+/Vpc_MapCoordinates_Advanced_GoogleMapCoords_Component/Component/json
+-get-elevation',
    [
        'Connection'      => 'keep-alive',
        'Accept'          => '*/*',
        'Accept-Encoding' => 'gzip, x-gzip, deflate, x-bzip2, bzip2',
        'Accept-Language' => 'en-US,en;q=0.5',
#        'Host'            => 'www.mapcoordinates.net:443',
        'Referer'         => 'https://www.mapcoordinates.net/en',
        'User-Agent'     => 'Mozilla/5.0 (X11; Linux x86_64; rv:78.0) 
+Gecko/20100101 Firefox/78.0',
        'Content-Length' => $payloadlen,
        'Content-Type'   => 'application/x-www-form-urlencoded; charse
+t=UTF-8',
        'DNT'            => '1',
        'Origin'         => 'https://www.mapcoordinates.net',
        'X-Requested-With' => 'XMLHttpRequest'
    ],
        $payload
    );
    die "call to HTTP::Request has failed" unless $req;

    if( $debug > 0 ){ print "$0 : $payload\n$0 : sending above payload
+, of $payloadlen bytes...\n" }

    $response = $ua->request($req);
    die "Error fetching: ".$response->status_line
        unless $response->is_success;

    my $content = $response->decoded_content;
    my $data = Data::Roundtrip::json2perl($content);
    die "failed to parse received data:\n$content\n"
     unless exists $data->{'elevation'};

    return $data->{'elevation'};
}
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bw, bliako

Is there any way to figure out what a reasonable guesstimate is of altitude given latitude and longitude?

Geo::WebService::Elevation::USGS - Elevation queries against USGS web services.

Thanks for this. It works for trump's (real) tower but scylla is shown to be somewhere near Hades (for a country with planetal ambitions, their map services are curiously modest to confine within the national boundaries and that "feet" default indicates possible time-warp to past eras):

use  Geo::WebService::Elevation::USGS;
use Data::Dumper;
my $eq =  Geo::WebService::Elevation::USGS->new(
    timeout => 60,
);
# white house
my $x = $eq->elevation(38.91205168958467, -77.03355236501928);
print Dumper($x);

# scilla sicily
$x = $eq->elevation(38.17378844699463, 15.83642789839883);
print Dumper($x);
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$VAR1 = {
          'Units' => 'Feet',
          'Data_Source' => '3DEP 1/3 arc-second',
          'y' => '38.9120516895847',
          'Elevation' => '96.95',
          'x' => '-77.0335523650193'
        };
$VAR1 = {
          'y' => '38.1737884469946',
          'x' => '15.8364278983988',
          'Elevation' => '-1000000',
          'Units' => 'Feet',
          'Data_Source' => '3DEP 1/3 arc-second'
        };
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