Flats and Calibration

ARIS shoots flats, darks and bias as steps of a sequence, or as a run of their own with no target. The rig runs them, so they finish with the app closed. Flats use your flat panel. Darks and bias need the light path closed.

Calibration in a sequence

On the Sequencing screen, open Pre-Sequence or Post-Sequence.
Switch on Take Flats, Take Darks or Take Bias. Its settings open under the row.
Set the counts and options, then start the sequence as usual.

Take Flats is in both lists. Take Darks and Take Bias are post-sequence steps. All three start switched off, at 20 flats per filter, 30 darks and 50 bias frames.

Take Flats lists the filters your targets use. With no targets, it uses the filters the step was last saved with, or the wheel’s.

When you start a sequence, the rig checks every Take Flats step. It refuses the start if a step names a filter the wheel does not carry, or if the step’s filters share none with your lights.

Flat source: Manual, Trained, Auto

FLAT SOURCE sets how each filter’s flats are exposed. Manual is the default.

Source	What the rig does
Manual	Lights the panel at a fixed brightness (a quarter of the panel’s range unless the step sets one) and shoots 1-second exposures. Nothing is measured. You set FRAMES PER FILTER.
Trained	Uses the profile you trained for that filter at the camera’s current gain: its panel brightness and its exposure. See Trained flat profiles.
Auto	Finds the exposure while it runs. You set a Target ADU (default 30000) and a BRIGHTNESS PER FILTER. The rig takes up to five test frames, starting at 1 ms, and keeps the exposure that lands within 10% of the target.

With Trained, the editor lists each filter: a check with its brightness and exposure when a profile exists, or manual fallback when none does. In a sequence, a filter with no profile still gets flats, at a quarter of the panel’s range and 1 second, and the rig warns you. Train Missing Profiles sends you to the Flat Panel screen.

With Auto, the run’s length cannot be estimated before it starts. If no test frame lands within 10% of the target, the rig shoots the flats at the last exposure it worked out.

How a flats step runs

The cover closes first, then the panel lights.
The wheel moves to each filter before its flats.
One filter failing does not stop the others.
When the step ends, the lamp turns off. Keep panel closed (on by default) leaves the cover shut. Turn it off to reopen a cover that was open before the step.
If you stop the run, the lamp turns off and the cover stays where it is.

Flats at each rotator angle

A post-sequence Take Flats has Rotate to each target’s angle, on by default. With it on, the rig:

Shoots flats at the current angle, for every filter in the step.
Turns the rotator to the angle each other target’s lights were shot at, and shoots that target’s filters there.
Turns the rotator back.

Angles within 0.5° count as one. If the rotator refuses a turn or does not arrive, the rig skips that angle and warns you. The mount does not move. A pre-sequence Take Flats, and flats shot on their own, use the current angle only.

Where flats are saved

Each flat is saved under every target of the run that it calibrates: the same filter and, with rotation, the same angle. A flat that matches no target goes to the camera’s calibration library. Darks and bias always go to the library. See Flats go with their lights and The calibration library.

Darks and bias

Take Darks with Match light exposures on (the default) shoots darks at each exposure your targets use, listed under MATCHED FROM TARGETS. Turn it off to list your own exposures and counts under EXPOSURES.
Take Bias shoots its FRAME COUNT at the EXPOSURE (SECONDS) you set, 0.001 s unless you change it.

Cool the camera first (on by default) waits until the sensor is within 1 °C of the Cooler target, then shoots. The cooler target is the same set point as Camera settings, so a change here applies everywhere. If the sensor does not get there in 15 minutes, the step fails before any frame, moves nothing, and leaves the cooler on.

If a wheel slot has Dark, Darks, Blank, Blanks or Opaque as a word in its name, darks and bias are shot through it (the lowest such slot) and the wheel goes back afterwards. Flats never use it.

Calibration without a sequence

You can shoot flats, darks or bias with no sequence and no target. Open the calibration sheet from:

the CALIBRATION FRAMES card on the Flat Panel screen;
Shoot calibration frames on the Files screen, shown when a project has no darks, flats or bias;
Shoot darks & bias, offered after you apply a new value in Find best offset.

The sheet has Flats, Darks and Bias tabs with the same settings as the sequence steps. Its header names the rig, the camera and its gain. Darks and bias use the camera’s own gain and offset. The run button names the job and its length, for example Run darks — 30 × 120 s, ~1 h 1 min. While it runs, the sheet shows the rig’s progress and STOP.

A run on its own is stricter than a sequence step:

Trained flats are refused for a filter with no profile at the camera’s gain. The sheet offers Train for those filters.
Darks ask for the exposure outright, because there are no lights to match.
Bias is the safe one: “Nothing opens, nothing moves, the lid stays shut.”

Trained flat profiles

A trained profile stores the panel brightness and exposure that put one filter’s flats at your target ADU, at one camera gain. Train them on the Flat Panel screen, in the FLAT WIZARD card.

Choose a Mode. Dynamic Exposure keeps the panel at Brightness (fixed) and finds the exposure. Dynamic Brightness varies the panel brightness, with the exposure between Min exposure (s) and Max exposure (s).
Set a Target ADU, or pick an Auto target fraction of the camera’s full scale (¼, ⅓, ½ or ⅔). ⅓ is the recommended target.
Check Gain. It shows the camera’s gain. Enter a number only if the camera does not report one.
Pick the Filters, then tap TRAIN SELECTED FILTERS.
Under REVIEW, tap ACCEPT or SKIP for each filter. Nothing is saved until you accept it, and accepting replaces that filter’s stored profile.

If a filter cannot reach the target, its card says why and what to change, for example Panel at full brightness with Raise the max exposure.

Each filter keeps one profile per gain, stored on the rig. TRAINED PROFILES lists them. Rows at a gain other than the camera’s are highlighted, because they will not be used for flats. The wizard never changes the camera’s gain: flats always run at the camera’s actual gain.

On a rig running the ARIS backend, training runs on the rig: it keeps going if you close the app, and the results wait there for you to review. A NINA rig trains from the app.

Find best offset

Find best offset finds the lowest camera offset at which no pixel reads 0 in a dark frame, at your current gain, and adds a margin: at least 50 ADU, or 8 times the read noise if that is more.

Open the Camera screen. Under CAPTURE DEFAULTS, the line below the Offset slider has Find best offset, or Recheck once a check has run.

Close the light path. The setup page lists what the check needs: the Cover closed, the Flat lamp off and, on a cooled camera, the Cooler on. Each row has a button to fix it. On a rig with no cover, cap the scope and tap Scope capped to confirm.
Tap Start. On a cooled camera the check waits until the sensor is at its set point. It takes about 4 minutes and holds the camera until it ends, and it starts with a 3-second dark to check for light.
Read the result: Best offset for gain G: N, and the margin it adds. Pixels that read 0 at every offset are counted as dead and left out.
Tap Apply N, or keep your current offset. Applying is the only step that changes the camera.

The check returns the camera to its old offset when it ends or when you cancel. It runs on the rig, so leaving the screen does not stop it. It stops if a sequence, the Imaging Loop or another flow takes the camera.