Sequencer

The sequencer, in Observatory → Sequencer, runs a whole imaging night automatically: cooling the camera, waiting for darkness, slewing and centring on targets, focusing, guiding, taking exposures through different filters, flipping at the meridian, reacting to bad weather, and parking at dawn.

A sequence is a tree of instructions. Containers group instructions and can repeat them; triggers watch for conditions between exposures and step in when needed.

Test every new sequence with the simulated observatory first, and stay with your equipment the first time you run it for real.

Contents

• The sequencer tab
• Building a sequence
• The template
• Containers
• Instructions
• Triggers
• Running a sequence
• Saving and loading
• Example: LRGB night with two targets

The sequencer tab

Area	Contents
Toolbar	Add, Remove, Up, Down, Template…, Open…, Save…, Run sequence, Stop
Left	The sequence tree
Properties (right)	The settings of the selected instruction
Triggers (checked between exposures)	The triggers, each with a tick box to enable or disable it
Bottom	The log of the running sequence, with time stamps

Each instruction in the tree shows its status: ▶ running, ✓ done, ✗ failed, – skipped, and "(disabled)" if you switched it off.

Building a sequence

1. Select the container where the new instruction should go (or an instruction after which it should go).
2. Click Add and choose the instruction type from the menu.
3. Edit its settings in Properties.
4. Use Up and Down to reorder, Remove to delete.

Every instruction has an Enabled property. Disabling an instruction keeps it in the sequence but skips it, which is handy for testing. Stop on error decides what happens if the instruction fails (see below).

The template

Template… builds a typical deep-sky night for the selected object (or M 31 if nothing is selected):

Night of 2026-10-18
├── Cool camera              −10 °C over 5 min
├── Unpark telescope
├── Wait                     until astronomical dusk
├── Target: M 31
│   ├── Wait                 until target altitude > 25°
│   ├── Slew, plate solve & center
│   ├── Autofocus
│   ├── Start guiding
│   ├── Loop (UntilAltitudeBelow)   alt < 20°
│   │   └── Expose light frames     10 × 180 s, filter L
│   └── Stop guiding
├── Park telescope
└── Warm camera              over 5 min

Adjust it to your needs instead of starting from scratch.

Containers

Container	Behaviour	Properties
Sequence container	Runs its children in order	Name
Target container	Runs its children with a target. Slew, centre, meridian flip and altitude conditions inside use this target	Target name, RA and Dec (J2000), optional rotation
Loop container	Repeats its children until its condition ends	Condition: Count (a number of Iterations), UntilTime (Until utc), UntilAltitudeBelow (target below Altitude deg), UntilAstronomicalDawn, or Forever (until stopped)

Containers can be nested, for example a loop of filters inside a target inside a loop that repeats every target.

Instructions

Instruction	What it does	Main properties
Slew to target	Slews to the current target's apparent position
Center target ("Slew, plate solve & center")	Slews, plate-solves, syncs and re-slews until the target is centred	Tolerance arcmin (1), Exposure (5 s), Bin (2)
Start guiding	Starts PHD2 guiding	Force calibration
Stop guiding	Stops guiding
Take exposures ("Expose … frames")	Takes a series of frames and saves them	Count, Exposure, Filter, Bin, Gain and Offset (−1 keeps the camera's value), Frame type (chosen from a list: LIGHT, DARK, FLAT, BIAS), Dither every N frames, Dither pixels
Record video	Records a planetary SER video, named after the target and saved under Planetary\<target>\	Exposure ms, Region (centred on the sensor, the same choices as in the Imaging tab: Full sensor or 1920 × 1080 down to 320 × 240), Bin, Gain and Offset (−1 keeps the camera's value), Filter, Max frames, Max seconds (stops at whichever comes first)
Run autofocus	Runs the V-curve autofocus routine	Exposure, Step size, Steps
Switch filter	Moves the filter wheel	Filter name, chosen from the wheel's filters
Cool camera / Warm camera	Ramps the sensor temperature gradually	Temperature, Minutes, Warm
Wait	Pauses	Kind: Seconds, UntilTime, UntilAltitude (target above Altitude deg), UntilAstronomicalDusk, UntilNauticalDusk, UntilSafe (safety monitor reports safe)
Park telescope / Unpark telescope	Parks or unparks the mount	Unpark
Dome shutter ("Open dome" / "Close dome")	Opens or closes the dome shutter or roof	Open
Run script ("Run external program")	Runs a program or batch file, for example to switch dew heaters or send a notification	Command (click … to choose the file), Arguments, Timeout sec
Annotation ("Note")	Writes a note to the log; does nothing else	Text

The Filter of an instruction is chosen from the connected filter wheel's filters (the simulator's L, R, G, B, Ha, OIII and SII when no wheel is connected), and another name can still be typed for a wheel that is not connected while you edit. In Take exposures and Record video the empty choice keeps the current filter.

For a planetary rotation series, put Record video in a Loop with a Wait after it, for example a 90-second video every 5 minutes until the planet sinks below 25°. With a filter wheel, use one Record video per filter (R, G, B) in the loop. The videos are named in the WinJUPOS style, so the Derotation tab can combine them later.

If an instruction fails, it is marked ✗, the error is shown in its properties and written to the log, and the sequence continues with the next instruction. Turn on Stop on error for instructions that must succeed (for example centring before a long series): when one fails, the rest of the container it is in is skipped (the rest of that target, say), and the sequence continues after that container, so a closing Park or Close dome still runs. An instruction directly in the sequence's top level ends the whole sequence.

A loop whose instructions all fail in one pass (for example because the camera stopped responding) stops instead of repeating the failure: it is marked ✗ with "Loop stopped: no instruction in it succeeded", and the sequence continues after the loop, so a closing Park or Close dome still runs.

Triggers

Triggers are checked between exposures. Tick the ones you want in the Triggers card:

Trigger	When it fires	What it does
Park and close when unsafe	The safety monitor reports unsafe (rain, clouds, wind)	Stops guiding, parks the mount, closes the dome, waits until conditions are safe again (checking every 30 s), then reopens, unparks and continues
Meridian flip 5 min after transit	A German equatorial mount on the east side of the pier is tracking a target that passed the meridian 5 minutes ago	Stops guiding, re-slews to the target so the mount flips to the west side, re-centres by plate solving and resumes guiding
Autofocus when HFR rises 15%	The median half-flux radius of the last 5 frames is 15% above the value measured at the last autofocus	Runs autofocus

The sequencing engine also provides Autofocus after 1.5 °C change (temperature-compensating refocus) and Autofocus every 30 exposures. They are available to scripts through Sidralune.Devices.Automation.

Running a sequence

Click Run sequence. The sequence runs in the background: you can keep working in other workspaces, and the task pill in the status bar shows its progress. The tree marks each instruction's status and the log records every step with its time.

Before it starts, Sidralune checks that the devices the enabled instructions need are connected: a camera for exposures, videos, centring and autofocus, a telescope for slewing, centring and parking, a focuser for autofocus, and a filter wheel for Switch filter. If one is missing, the sequence does not start and a message names what to connect. Guiding, cooling and dome instructions are skipped when their device is absent, so they do not block a run.

Each frame the sequence takes is shown in the Imaging tab as it arrives, with its star count, HFR, FWHM and file name. Videos are shown there too while they record, with the frame count and frame rate, and Open in Planetary opens the last one. Stopping the sequence during a video ends the recording and keeps the frames so far. While the sequence runs, everything else that uses the camera is disabled so that nothing can fight over it: Start and Loop in the Imaging tab, Run autofocus, Center, and Start polar alignment. The sequence's own autofocus and centring instructions are not affected. If a capture, preview loop, autofocus run, centring or polar alignment is already running, Run sequence is disabled until it has finished or you stop it.

Click Stop (available while a sequence runs), or run the Observatory: abort all command, to stop. The current exposure is aborted and the mount stops slewing; it does not park automatically, so park it yourself if you are ending the night.

Frames are saved with the file name pattern from the Imaging tab, under the image folder from Settings → Observer & accounts.

Saving and loading

While a sequence runs you can still change it, in case you forgot something: edit the Properties of instructions that have not run yet, and Add, Remove, Up and Down instructions. After each instruction the sequence goes on with the next one below it that has not run yet, so an instruction added below the running one runs, one added above it has already been passed, and an instruction moved below the running one after it has run does not run again. The running instruction (or a container while one of its instructions runs) cannot be removed or moved; Stop the sequence for that. Template…, Open… and Save… wait until the sequence has stopped.

Save… writes the sequence tree to a .json file, and Open… loads one. The file is plain JSON, so you can also generate sequences with a script or edit them in a text editor. Trigger choices are not stored in the file; set them before you run.

Example: LRGB night with two targets

Night
├── Cool camera              −10 °C, 10 min
├── Unpark telescope
├── Wait                     until astronomical dusk
├── Target: NGC 891
│   ├── Wait                 until altitude > 30°
│   ├── Center target
│   ├── Switch filter        L
│   ├── Run autofocus
│   ├── Start guiding
│   ├── Loop                 Count, 3 iterations
│   │   ├── Switch filter    L
│   │   ├── Take exposures   12 × 120 s, L, dither every 2
│   │   ├── Switch filter    R
│   │   ├── Take exposures   4 × 120 s, R
│   │   ├── Switch filter    G
│   │   ├── Take exposures   4 × 120 s, G
│   │   ├── Switch filter    B
│   │   └── Take exposures   4 × 120 s, B
│   └── Stop guiding
├── Target: M 33
│   ├── Center target
│   ├── Start guiding
│   ├── Loop                 UntilAstronomicalDawn
│   │   └── Take exposures   10 × 300 s, Ha
│   └── Stop guiding
├── Park telescope
├── Close dome
└── Warm camera              10 min

With the safety, meridian flip and HFR autofocus triggers enabled, this runs unattended from dusk to dawn.