Overpass 0.4.3

Download

• Mac: Overpass-0.4.3.dmg below, for macOS 14 or later, signed with my Developer ID and notarised by Apple. Open it and drag Overpass to Applications, replacing 0.4.2.
• iPhone and iPad: join the TestFlight beta at https://testflight.apple.com/join/nA7S2Nkn and install it with the TestFlight app.

TLE sources

• On Observe, a satellite's name in the pass list and the selected objects is followed in small grey type by the source its elements come from, such as MESAT1 Amateur radio. The Look Up card shows it too.
• When more than one enabled source lists a satellite, the one named is the one whose elements are in use, the newest set, with a count of the others. Hovering over it on a Mac names them.

The changes in 0.4.0 to 0.4.2 are in their release notes.

Overpass 0.3.2

Download

• Mac: Overpass-0.3.2.dmg below, for macOS 14 or later, signed with my Developer ID and notarised by Apple. Open it and drag Overpass to Applications, replacing 0.3.1.
• iPhone and iPad: join the TestFlight beta at https://testflight.apple.com/join/nA7S2Nkn and install it with the TestFlight app.

Conjunctions

• The search follows the location in Settings, and runs again when it changes. It used to pick up a new location only when one of its own options changed.
• "Search for a place…" uses Apple's map search and lists the matches to choose from, landmarks included. The address lookup before it found no landmarks.
• On iPhone, each button in the options row answers only its own tap. A tap anywhere in the row used to press them all, which could turn off both the Moon and the Sun and leave the search empty. With neither on, the summary now says so.
• On an iPhone on its side, an event's map stays full screen, and the details card folds to one line with the chevron by its title. The card no longer slips behind the tab bar.

Units

• Settings > Appearance > Units: metric or imperial, for every distance and height the app shows. The first launch follows the system setting.

Globe

• No orbit line. Drawn over the turning Earth, a high orbit smeared into long curves through space. The ground track, the satellite at its height and its footprint stay.

Overpass 0.3.1

This is the first version on TestFlight for iPhone and iPad, and the Mac download below is the same version.

Download

• Mac: Overpass-0.3.1.dmg below, for macOS 14 or later, signed with my Developer ID and notarised by Apple. Open it and drag Overpass to Applications, replacing 0.3.0.
• iPhone and iPad: join the TestFlight beta at https://testflight.apple.com/join/nA7S2Nkn and install it with the TestFlight app.

North

I tested the HAZ46 at north in both hemispheres. Its goto never turns through north and always goes the long way round, so north is the cable stop and there is no setting for it.

• When tracking reaches north it stops and asks before unwinding. A setting unwinds without asking.
• In Special mode, an option tracks up to 90° past north and unwinds when tracking ends.

Seeing where satellites go

• Sky, Globe and Map views above the sky chart, with up to five tracks at once. ⌘-click or ⇧-click passes to add them.
• The globe is a 3D Earth with day and night, the tracks at their real height, and the focused satellite's footprint. The map is a flat world map centred on you. Both work offline.
• Look up on iPhone and iPad: hold the phone to the sky to see where satellites are and where they will rise.

The mount

• Mount GPS status in the mount panel, and its location as yours once the fix is steady.
• Overpass always launches in Normal mode, and disconnecting or quitting puts the mount back in Normal mode.
• Stop leaves the mount's own sidereal, lunar or solar tracking running. A setting, on by default, turns the mount's tracking off when Overpass connects.
• Switching between Normal and Special mode keeps the alignment, going by the mount's own reading.

Camera

• Exposure and gain for USB guide cameras that offer them, such as iOptron's iPolar.
• Click an object in the camera image and the mount follows it.

Conjunctions

• Search for any satellite by name or catalog number, such as ISS, as well as the space stations.

Fixes

• The app no longer lags on iPhone. A timer in every row of the pass list kept the main thread busy.
• The Mac toolbar stays in one place between tabs.
• A footprint over a pole, and a high satellite's footprint on the globe, now draw correctly.

Overpass 0.3.0

I spent an afternoon with the HAZ46 and the Sun moving the mount between Normal and Special mode, and most of this release is what that turned up about how the mount behaves when it changes mode.

Download

Overpass-0.3.0.dmg below, for macOS 14 or later, signed with my Developer ID and notarised by Apple. Open it and drag Overpass to Applications, replacing 0.2.0.

Normal and Special mode

• Connect by USB in Normal mode as well as Special mode, for Passive and Step tracking over the cable without the mount's WiFi.
• Connected by USB, a button in the mount panel switches between Normal and Special mode without disconnecting. Tracking stops and the mount is held still before the switch, including the sidereal tracking Normal mode can start by itself.
• It turns out the HAZ46 keeps its position through a mode switch, but for a few seconds after leaving Special mode Normal mode reports a placeholder of az 0, alt 0 or az 180°, alt 90°. A sync sent during that window is added to the position the mount kept, which is how I managed to double mine. Overpass now waits for the real position before doing anything.
• After leaving Special mode the hand controller asks for an alignment, and Normal mode will not track until it is synced. Overpass syncs it once the real position is back, on the target if the scope is within half a degree of it, otherwise on where it knows the scope points, and reads the position back to check. If the mount was left that way by a disconnect, it happens on the next Normal mode connect.
• Overpass keeps its own record of where the scope points across launches, holds it when the mount disagrees so a bad reading cannot overwrite a good one, and writes every mode switch and sync to a mount log.

Syncing

• Sync on the target works in both modes. In Special mode it moves Overpass's own alignment zeros and sends nothing to the mount; in Normal mode it syncs the mount and reads the position back.
• Settings has "Set position" for when you know where the scope points, and "Test mode switching", which switches modes with nothing moving and reports what the mount reads at each step.

Tracking

Overpass has three ways to track, and which one you get depends on the mode the mount is in.

• Passive, in Normal mode, is the mount doing the work. Overpass slews to the object the allowed way round the cable stop, sends an RA/Dec goto, sets the mount's own tracking rate (solar for the Sun, lunar for the Moon, sidereal for stars and planets) and then leaves it alone. It re-centres the Moon every five minutes, because the Moon's parallax moves it more than the lunar rate allows for, and for a geostationary satellite it slews there and holds. It is the right choice for anything that moves steadily across the sky, and the wrong one for a satellite crossing it.
• Step, in Normal mode, is Overpass sending a goto to where the target will be every few seconds. Fine for an antenna, jumpy in a telescope.
• Smooth, in Special mode over USB, is Overpass varying both axis speeds continuously. This is the one for satellites.

Changes this release:

• Passive tracking stays active while the mount tracks, watching the mount's own status and saying so if it stops. Before this it handed over to the mount and looked finished, which on the Sun was enough to convince me it had stopped. Overpass sends no motion commands in that time, only a status check every few seconds.
• How often Normal mode is polled and the shortest Step interval are a setting, from 0.5 to 5 s with 1 s as the default, since sub-second commands in Normal mode have given me trouble.

Sky view

Drag on the dome, or twist on a trackpad, to spin it to the way you are facing. It snaps to N, E, S and W, and the buttons in the corner flip east and west and put north back at the top.

Not yet tested on hardware

The automatic sync after switching to Normal mode, Passive tracking's status watching, and crossing north under rate control during a slew. Every quirk measured so far is in docs/iOptron-Special-Mode-Protocol.md under "HAZ46 quirks, measured", which is worth reading before trusting any of it on an HAE.

Overpass 0.2.0

The first week of running Overpass against a HAZ46 at the end of a pass turned up a few things worth fixing, and the object list got a lot more to say about what is up there.

Download

Overpass-0.2.0.dmg below, for macOS 14 or later, signed with my Developer ID and notarised by Apple. Open it and drag Overpass to Applications, replacing 0.1.0.

Tracking

• Smooth tracking used to hold the planned speed constant for each second of the plan and step it at every sample, which near the top of a pass you could hear as a jolt once a second. The planned speeds now come from a cubic through the plan, so they change a little at every update.
• How often Smooth tracking updates is a setting, from every 0.05 s to every 2 s. The correction gain and the planned speed adjust to the period, so the slow settings stay stable. Each update costs about 45 ms on a HAZ46, so 0.05 s is close to as fast as the mount answers. The setting only applies once the mount is on target and tracking; waiting at the start point and catching up run at four updates a second.
• Catching up under rate control now runs at the full axis speed. It was limited to 2°/s, and one 216° catch-up took 110 s that should now take under 40 s.
• The tracking trace keeps four minutes for export, enough for a whole pass. The chart still shows the last minute.

The mount's own slew

It turns out the HAZ46's :T0 slew treats +180° and −180° on the azimuth axis as two separate ends, and on a HAZ that is due north. Asked to cross it, the mount sets off the long way round, which on my mount was heading for the cables. It also accepts a slew to within a few degrees of ±180° and then quietly does nothing.

Native slews now stop 8° short of ±180° and cross north under rate control at full speed. Any native slew that starts heading away from its target is stopped within about a second and finished under rate control. Settings has a "Test the mount's slew" button that measures all of this on your own mount, which is worth running once on an HAE before trusting it, and the details are in docs/iOptron-Special-Mode-Protocol.md.

Objects

• Satellites are listed in columns: number, international designator, type, owner, launch date, period, perigee, apogee, inclination, length by diameter, span, radar cross-section, a small, medium or large size class, and TLE age. Click a column header to sort that source by it, and again to reverse. Each source keeps its own sort, and columns that do not fit the window are dropped, least useful first.
• Search compares attributes as well as names: launched>2020, period<100, perigee>500, inc>50, rcs>10, span>20, size=large, owner=PRC, type=debris, combined as you like.
• The launch, orbit and radar cross-section come from CelesTrak's satellite catalogue. The physical dimensions come from Jonathan McDowell's General Catalog of Artificial Space Objects, under CC BY 4.0, which covers Tiangong, Starlink and most of what has no published radar cross-section. Neither needs an account. Together they are about 26 MB, downloaded in the background once a week and kept for offline use.
• The Observe list's brightness sort falls back to radar cross-section and then physical size for satellites, since TLEs carry no magnitude.

Not yet tested on hardware

Crossing north under rate control during a slew, and the 0.05 s and 1 to 2 s update periods over a whole pass. Camera guiding is moving to its own branch while I work out what a cheap UVC webcam will and will not let me control, which so far is not the exposure.

Overpass 0.1.0

First version. For the longest time I have been driving my iOptron HAZ and HAE mounts from a Windows laptop running Heavenscape SkyTrack, and Overpass is what I wrote to stop doing that.

Download

Overpass-0.1.0.dmg below, for macOS 14 or later. It is signed with my Developer ID and notarised by Apple, so it opens without Gatekeeper complaining. Open it and drag Overpass to Applications. There is no iPhone or iPad build to download; those will need TestFlight.

SHA-256: c21814cbf6e414d9120812bc0993e80b7f4a8b2d0b5b019a858662700e882bac

What is in it

• SGP4 pass prediction from CelesTrak groups, URLs or local TLE files, with pass filters and a time bar that moves the sky up to two days either way.
• Passive and Step tracking over WiFi, and Smooth tracking over USB in Special Mode, which settles to a median error of about 2″ on a HAZ46.
• A cable stop the mount never rotates through, with slews that go the long way round when they have to.
• Conjunctions: ISS and Tiangong transits of the Moon and Sun around a place you choose, on a map, refreshed as the event gets closer.
• A pass calculator out to fourteen days, star alignment, iPhone camera guiding through Continuity Camera, and red night vision.

Tested on a HAZ46

The WiFi connection, Passive tracking of the Moon, Step tracking, USB Special Mode and Smooth tracking. Not yet tested on hardware: the iOS build, the USB relay, camera guiding, the route around the cable stop, and the fix for the HAZ's 5 second late reply.

Before you connect

Set the cable stop azimuth in Settings before tracking anything; the default is north, which may not be where your cables are. Be aware that the mount stays in Special Mode across power cycles and WiFi does not work while it is in it, so leave "Leave Special mode when disconnecting" turned on.

Satellite positions agree with the reference SGP4 within 10 m and with transit-finder.com within 0.13 s, after working around a drag bug in SatelliteKit (#16, fix in #17).