https://aussiescience.com/starlog/StarlogLearning the southern sky on cheap gear, logged honestly.2026-11-04T00:00:00+10:30Brendanhttps://aussiescience.com/starlog/learned/one-star-is-not-an-alignment/One star is not an alignment2026-11-04T00:00:00+10:30Aligning on the target alone tells the mount where it is pointing, not how far it is from level. The tracking rates that come out of a one-point model are wrong by a steady amount, and the planet drifts at a steady speed with the motors running exactly as told. Two points, well apart, or it is not an alignment.https://aussiescience.com/starlog/sessions/2026-11-03-a-saturn-worth-keeping/A Saturn worth keeping2026-11-03T00:00:00+10:30Saturn on the 127 with the ZWO, at 20 ms and gain 335, near its highest. The planet drifted out of the frame all night even with tracking on, and the stacker had to chase it. Twenty-four recordings, three of them full-frame by mistake, then cloud. The best six minutes gave a Saturn with the ring gap, the ring shadow and a belt, and it is the first picture with my name on it.https://aussiescience.com/starlog/learned/the-detail-was-in-the-recording/The detail was in the recording — the stack was hiding it2026-10-31T00:00:00+10:30The first Saturn stacks from the ZWO came out as white, colour-fringed blobs. The same recordings, put through a proper planetary chain, showed the ring gap, the ring shadow and a belt. Selection at full resolution, sub-pixel alignment, lining up the colour channels, deconvolution, and a tone curve that does not burn out the globe.https://aussiescience.com/starlog/sessions/2026-10-29-first-light-for-the-zwo/First light for the ZWO2026-10-29T00:00:00+10:30First night with the ZWO ASI662MC, on the 127 Mak with the SV205 moved to the finder. Saturn came out soft in sixteen recordings, which I blamed on my focus; the numbers said seeing. After midnight, five 7x4 lunar mosaics: one from auto exposure, one lost to dew, two that sat too low, and one keeper. Then the Moon went behind the house.https://aussiescience.com/starlog/sessions/2026-10-27-the-setting-moon-from-the-back-yard/The setting Moon from the back yard2026-10-27T00:00:00+10:30Two nights in one entry. 26/10 clouded out. On 27/10 the Moon came up behind the verandah and into cloud, and an 8x5 at 23:00 got the lower two thirds before power lines blacked it out. At dawn, with the scope moved to the back yard, a grid at 12-15 degrees, a column down the left limb and one extra panel at the top stitched into a complete waning Moon.https://aussiescience.com/starlog/sessions/2026-10-25-the-whole-moon-in-one-piece/The whole Moon in one piece2026-10-25T00:00:00+10:30A day before full, on the 127 Mak and the AZ-GTi, in wind. The laptop ran out of power mid-session and the mount found the Moon again from where it had stopped. A 7x5 mosaic at 14 ms and a patch along the top made the first complete, clean Moon from this rig. Three more grids after it: one walked off, one was too slow on the USB drive and was deleted, and combining all of them made the mosaic worse, not better.https://aussiescience.com/starlog/sessions/2026-10-23-a-gibbous-moon-and-a-grid-that-would-not-stay-on-it/A gibbous Moon, and a grid that would not stay on it2026-10-23T00:00:00+10:30A 91% gibbous Moon on the 127 Mak and the AZ-GTi. The finder-to-Mak offset from last week worked first time, focus was good and one 300-frame run stacked cleanly. Then three mosaic attempts in forty minutes: the new disc-measuring mode lost the limb, a bug stopped the fixed grid from planning, and the two grids that did run walked off the Moon partway through. Cloud from about 20:10 finished it. I called it at 21:40.https://aussiescience.com/starlog/notes/2026-10-19T1415-the-mosaic-measures-the-moon-first/The mosaic measures the Moon before it lays the tiles2026-10-19T00:00:00+10:30Written the day after two 43-panel runs each missed most of the half Moon. Every goto that night landed within two arcseconds. The tiles were in the wrong place because the grid was laid out around where the alignment thought the disc centre was. After an hour, a one-point model was several arcminutes out. That was more than the margin, and nothing checked it.https://aussiescience.com/starlog/sessions/2026-10-18-two-half-misses-make-one-moon/Two half-misses make one Moon, and Saturn in the wrong hole2026-10-18T00:00:00+10:30The best sky of the spring. Two 43-panel lunar mosaics on the AZ-GTi, 128 GB each, every goto within two arcseconds, but each grid missed most of the Moon; stitched together, the two make a complete half Moon. Getting there took an hour: the finder and the Mak point about a third of a degree apart and nothing recorded it. Saturn reached the finder and never reached the Mak; I packed up at 23:05 with the conditions still excellent.https://aussiescience.com/starlog/sessions/2026-10-17-the-helper-ran-out-halfway-through/The helper ran out halfway through2026-10-17T00:00:00+10:30Codex rebuilt a lot of rig-ui during the day and helped drive the evening until its usage limit cut it off at 20:04. I shot the 7x4 mosaic myself at 20:28. It ran to 25 panels, but the grid sat too high and missed a limb, the SV205 repeated frames, and tracking only half held. Omega Centauri came out black. Processed the next day into a good, cropped half Moon.https://aussiescience.com/starlog/sessions/2026-10-16-saturn-in-colour-with-astrodmx/Saturn in colour, with AstroDMx2026-10-16T00:00:00+10:30An AstroDMx night with the 127 on the AZ-GTi and no agent driving: 38 runs of 50 full-size frames, the crescent from 19:29 and Saturn from 21:19. Codex could not reach the rig from its sandbox and only did the processing afterwards, which gave a crescent mosaic, detail crops and Saturn in colour from 300 frames.https://aussiescience.com/starlog/sessions/2026-10-15-thirty-five-panels-and-a-dimming-i-never-explained/Thirty-five panels, and a dimming I never explained2026-10-15T00:00:00+10:30The 127 on the AZ-GTi, run from the mount's hotspot. A 35-panel crescent mosaic at 19:44, anchored 11 arcminutes off the disc centre with a new shift option; a second, softer one after the image dimmed twentyfold at 21:33 and I blew into the tube thinking the mirror had fogged. Saturn reached the Mak at 23:02, and the recording of it was too small to use.https://aussiescience.com/starlog/sessions/2026-10-14-the-moon-in-the-127-found-by-eye/The Moon in the 127, found by eye2026-10-14T00:00:00+10:30A night of near misses with the 127 and the AZ-GTi: the mount's WiFi link lost half its packets, the house power went out, the finder-to-Mak offset turned out to be more than a degree and a two-degree camera sweep never found it. The Moon reached the Mak at 22:15 because I saw it in the eyepiece, and was focused at 22:23 with craters on the terminator. The recording of it is 227 black frames.https://aussiescience.com/starlog/sessions/2026-10-13-first-light-for-the-127-with-the-mount-asleep/First light for the 127, with the mount asleep2026-10-13T00:00:00+10:30The 127 Mak's first frames of sky: an 8% crescent at 15 degrees, hand-pointed and untracked, craters along the terminator in a 50-frame PNG run. The AZ-GTi never spoke to the laptop all night - its WiFi had quietly gone back to hotspot mode - so rig-ui could not jog, track or centre anything, and the Moon crossed the sensor in forty seconds.https://aussiescience.com/starlog/sessions/2026-09-28-the-whole-moon-and-a-search-that-found-saturn/The whole Moon, and a search that found Saturn2026-09-28T00:00:00+10:30A complete Moon at last - 24 panels, 100% of the sunlit disc, measured and not just looked at - and my first Saturn, rings and all, in a single overexposed frame. On the way: a spiral search built at the eyepiece that found Saturn in two and a half minutes, a go-to that "overshot by 300.8 degrees" because two threads were reading each other's mail, a crosshair drawn in the wrong place, and cloud that took Saturn just as the focus came good.https://aussiescience.com/starlog/sessions/2026-09-22-still-not-a-complete-moon/Still not a complete Moon, and I said it was2026-09-22T00:00:00+10:30Best image yet and still 11.8% of the sunlit disc missing. Three launches, a plate scale that had been 15% wrong all along, and a centring error of 8'.https://aussiescience.com/starlog/sessions/2026-09-21-a-mount-that-answered-every-question-and-refused-to-move/A mount that answered every question and refused to move2026-09-21T00:00:00+10:30The best sky in weeks, and two hours lost to a mount that talked happily and would not turn. Saturn is a fortnight from opposition.https://aussiescience.com/starlog/notes/2026-09-20T1642-turn-the-exposure-right-down-in-daylight/Turn the exposure right down in daylight2026-09-20T00:00:00+10:30Out in a gale this afternoon with the Moon sitting at 55 degrees in a blue sky, and the first thing the camera gave me was a completely white screen while I could see the Moon perfectly well through the finder with my own eye. I spent a while treating that as a camera fault. It was not.https://aussiescience.com/starlog/notes/2026-09-20T0623-daylight-plan-for-the-tracking-restart/Daylight plan: teaching the mount to keep tracking between panels2026-09-20T00:00:00+10:30The one job left from 19 September. Written down before I start because it involves unbounded motion, and the whole point is to do it somewhere I can watch it rather than at 21:00 on the one clear night.https://aussiescience.com/starlog/notes/2026-09-20T0520-how-the-lunar-mosaic-is-made/How the lunar mosaic is made, end to end2026-09-20T00:00:00+10:30Written down properly after the 19 September run, because the method now has enough moving parts that I will not remember which order they go in, or why half of them are the way they are. This is the whole path from a cold tripod to a finished picture.https://aussiescience.com/starlog/learned/a-sync-cannot-reach-the-encoder-frame/A sync fixes the mount's model, not the mount's encoders2026-09-20T00:00:00+10:30Syncing on the Moon in the SynScan app corrects the firmware's pointing model, which is what GOTOs use. A script that reads raw axis counts never consults that model, so the sync is invisible to it. My azimuth error sat at about 8 degrees through three syncs and two re-centrings and did not move, because nothing I did in the app could have moved it.https://aussiescience.com/starlog/learned/bounded-motion-is-the-safety-property/Bounded by construction: why an offset goto is safe and a rate command is not2026-09-20T00:00:00+10:30An offset goto carries its own stopping condition — a step count the motor controller counts down to zero. A slew-rate command carries none: it runs until something else stops it. That difference, not the size of the number, is what makes automated mount motion safe to leave running. A step cap protects the first kind and cannot protect the second.https://aussiescience.com/starlog/learned/seventeen-milliseconds-per-pixel/Seventeen milliseconds per pixel: untracked panels can never line up2026-09-20T00:00:00+10:30Every goto stops firmware tracking and nothing restarts it, so each mosaic panel is exposed with the mount standing still while the Moon runs at 13 arcseconds a second. At 0.222 arcsec per pixel that is one pixel every 17 milliseconds. A two-second panel travels 117 pixels. Pixel-accurate placement is not hard under those conditions — it is arithmetically impossible.https://aussiescience.com/starlog/sessions/2026-09-20-the-only-thing-that-worked-was-the-thing-i-came-to-test/The only thing that worked was the thing I came to test2026-09-20T00:00:00+10:30I went out in a gale to do one job: make the mount keep following the Moon while a panel is being exposed. That job is done, measured, and finished. Almost everything else about the evening went wrong, and most of it went wrong in ways that were my own fault and that I could not see at the time.https://aussiescience.com/starlog/sessions/2026-09-19-every-goto-was-perfect-and-the-picture-still-didnt-line-up/Every goto was perfect and the picture still didn't line up2026-09-19T00:00:00+10:30The night I found out the mosaic was never going to work the way it was built. Every goto landed within an arcsecond — seventy-two panels across two grids — and the tiles still did not line up, because the mount is stopped while each panel is exposed and the Moon crosses a pixel every seventeen milliseconds. Also: a sync cannot fix the pointing frame this script uses, the frame drift has no confirmed cause, and 250 frames per panel is far worse than 30. Hugin rescued the picture at four in the morning. Written up after the fact: I was asleep from 21:00, so this entry claims only what the instruments recorded.https://aussiescience.com/starlog/sessions/2026-09-18-the-mount-moved-on-its-own-forty-eight-times/The mount moved on its own, forty-eight times, and every one of them was where I sent it2026-09-18T00:00:00+10:30The night the laptop drove the telescope. INDI could connect but never finish a goto, so the mount went on raw motor-controller commands instead: a 0.05 degree test that landed to one arcsecond, then a 2 by 2, then a full 8 by 6 — 48 panels, 96 moves, none more than six arcseconds off. It took four hours of false starts to get there, most of them mine, and the best single frame of the night came from a fifty-frame manual run in between.https://aussiescience.com/starlog/sessions/2026-09-17-five-metres-of-cable-and-an-empty-focuser/Five metres of cable, an altitude limit, and an eyepiece where the camera should have been2026-09-17T00:00:00+10:30Four and a half hours between first question and first frame, almost none of it spent on the sky. A new five-metre USB cable that would not enumerate, an altitude limit I had set and forgotten, a star alignment attempted before any stars were out, and ninety seconds of black frames that turned out to be an eyepiece sitting where the camera should have been. Then thirty-one minutes, eleven runs, 5,500 frames, and the best Moon I have. Went back out at nine, got fifteen more runs, and then spent an hour trying to hand the mount over to the laptop. Got it talking, got it connected, got it to move — and then a coordinate bug slewed it two degrees off the Moon and I could not find it again.https://aussiescience.com/starlog/notes/2026-09-13T1908-clouded-out-and-glad-of-it/Didn't set up, and then it clouded over anyway2026-09-13T00:00:00+10:30Checked what the Moon was doing tonight and decided not to bother. Then it clouded over. First time a decision not to observe has been confirmed by the sky an hour later.https://aussiescience.com/starlog/learned/compass-north-is-not-true-north/Compass north is eight degrees off, and the mount has no way to know2026-09-12T00:00:00+10:30A phone compass points at magnetic north. At Goolwa that is about 8 degrees east of true north, and an alt-az goto inherits the error whole. Measured it at 7.4 degrees by centring Venus by hand and reading how far the mount had to move.https://aussiescience.com/starlog/learned/lower-resolution-is-not-a-roi/A lower resolution is not a region of interest — the SV205 scales, it doesn't crop2026-09-12T00:00:00+10:30Dropping AstroDMx from 3264x2160 to 800x600 shrank the files fifteen-fold, shrank Venus threefold, and left the frame rate exactly where it was. The camera downscales the whole field instead of reading out part of the sensor, so the mode throws away the resolution you are trying to record and buys nothing back.