IMX585 cameras: cooled and uncooled 2.9 µm bodies for planets, EAA and small targets

The IMX585 fills more roles in our data than any other sensor: planetary, guide, all-round and cooled deep-sky. ZWO sells it as an uncooled planetary camera and as a cooled deep-sky camera; Player One’s uncooled Uranus-C page pitches it for planetary, EAA and lucky imaging; QHY builds it into the miniCAM8M with an 8-position filter wheel; ToupTek’s ATR585C page calls it suitable for planetary and deep-sky photography. ZWO’s ASI585MC/MM Pro page says the sensor’s frame rate makes it suitable for deep-sky as well as solar, lunar and planetary work.

A small 16:9 frame

The frame is 11.1–11.2 mm by 6.3 mm, a 16:9 shape like a 4K video frame. At 400 mm that is about 1.60° × 0.90°; at 1000 mm, 38.3′ × 21.5′. The short side is the constraint: a target taller than the frame’s height needs a shorter focal length or a mosaic, even if its long axis would fit. For round objects, only 44 % of a 16:9 frame lies inside the largest circle that fits, compared with 78.5 % on the square IMX533.

Two pixel arrays are published for the same sensor. ZWO and ToupTek’s ATR585M give 3840 × 2160 (11.14 × 6.26 mm); QHY, Player One and ToupTek’s ATR585C page give 3856 × 2180 (11.18 × 6.32 mm). The difference is 0.16′ in width at 1000 mm. QHY labels 3856 × 2180 as the “Total Pixel Area” on the miniCAM8 page but as the “Effective Pixel Area” on the QHY5III585 page, so the label alone does not tell you which pixels record sky.

Sampling with 2.9 µm pixels

image scale (″/px) = 206.265 × 2.9 ÷ focal length (mm) = 598.2 ÷ focal length (mm)

The scale is 1.50″/px at 400 mm, 1.00″/px at 598 mm, 0.60″/px at 1000 mm and 0.29″/px on an 8-inch SCT at 2032 mm. For planets, the fine end is the point: at f/10 the pixel falls about 1.9 times across the Dawes limit, and the QHY5III page shows the focal ratio for other targets. For deep-sky work at long focal lengths it is finer than seeing usually supports. If you assume 2″ seeing, 2032 mm gives about 6.8 pixels per star FWHM; binning 2×2 gives 0.59″/px (3.4 px) and 3×3 gives 0.88″/px (2.3 px), the latter inside the sampling calculator’s default 2–3 px band. The sampling and seeing guide explains the trade-off.

Cooled and uncooled versions side by side

Maker	Uncooled	Cooled	Back focus as published
ZWO	ASI585MC	ASI585MC Pro	17.5 mm for both (ZWO also lists 6.5 mm without the 11 mm ring)
QHY	QHY5III585C	miniCAM8M (with filter wheel)	17 mm with adapter, 8 mm without / 17.5 mm
Player One	Uranus-C	Uranus-C Pro	12.5 mm / 17.5 mm
ToupTek	none	ATR585C, ATR585M	17.5 mm

Cooling is published as more than 35 °C below ambient (ZWO), 45 °C (QHY miniCAM8M, ToupTek), and 35–40 °C (Player One). The uncooled bodies have no regulated set-point, so their dark frames cannot be shot at a fixed sensor temperature; the calibration frames guide covers how to handle that.

Published figures that disagree

Full well ranges from 38.9 ke⁻ (ATR585M, LCG mode) to 54 ke⁻ (miniCAM8M), and QHY’s own two IMX585 pages say 52 ke⁻ and 54 ke⁻. ZWO’s product page gives the ASI585MC 0.7 e⁻ read noise and 40 ke⁻, while its compare page lists 0.8–12 e⁻ and 47 ke⁻ for both the ASI585MC and the Pro. Player One’s product pages say 7.2–0.7 e⁻ for both Uranus models, and the Uranus-C manual says 6.5–0.7 e⁻. Treat these as each maker’s statement for its own modes and firmware, not as measurements of the sensor.