SQM History

Tools ▸ SQM History shows everything you have recorded, grouped by night, week, month, season or year.

Choosing what to show

From / Through	The dates to include. It opens on the 30 days up to your most recent night with readings.
◀ ▶	Jump to the previous or next period that has readings, skipping empty stretches.
Group	One row (or point) per night, week, month, season or year.
Interval	Which part of each night is counted. Astronomical night by default; see what is counted.
Moon down only	Leave out readings taken while the moon was up. See the moon.

Three views

Table	One row per period with every statistic and how many readings went into it. Double-click a row to open that period.
Trend	One dot per period at its mean, with a line from the 10th to the 90th percentile of its readings. The background is shaded in the Bortle class colours, so each dot sits in its class. The scale stays at 16–22, so the space above the dots shows how far each period was from a truly dark sky. Dates are spaced in real time, so a gap between observing runs shows as a gap.
Calendar	Month pages with each night coloured by its class. Colour chooses whether that is the night’s mean or its darkest reading. Each date also shows the moon. Click a night to open it.

SQM History showing the Trend view — Trend: each night’s mean against the Bortle classes.

SQM History showing the Calendar view — Calendar: each night coloured by its class, with the moon’s phase.

Click a class in the legend below the views to show only that class; Ctrl-click to add more. Other periods are dimmed, not removed.

One night in detail

Opening a night shows its chart, every reading in a list, and the details of whichever reading you select: its time, value, class, and exactly what the meter sent back. Click a point on the chart or a row in the list.

The Night detail window — One night in detail, with a reading selected.

Nights that recorded nothing usable

A night when the meter ran but every reading was saturated, stale or failed is not the same as a night nobody recorded, and the application keeps them apart. It shows as dashes in the table, a tick along the bottom of the trend, and a hatched day on the calendar. Open it to see what went wrong.

The line under every view

Under each view a short note says which interval was used, which average is shown, and how many readings were counted out of how many stored. If a number ever looks surprising, start there.

Saving and exporting

Export to CSV	The rows on screen, in the same order, ready for a spreadsheet. The note about what was counted goes at the top.
Save as PNG	The Trend or Calendar as an image, with its own title, dates and colour key, ready to share.