QHYCCD cooled cameras: computed sensor sizes, pixel areas and fields

QHYCCD publishes pixel counts and pixel sizes for every cooled camera here, but a millimetre sensor size for only some of them. The QHY600, QHY294M Pro, QHY183 and the two discontinued models come with dimensions. The QHY268M/C, QHY533M/C and miniCAM8M are described only as “APS-C”, “Typical 1 inch” or “1/1.2 inch”. For those, the spec table computes the size as pixels × pitch and marks it †; the field-of-view table uses pixels × pitch for every camera, so for these three the two tables agree exactly.

Effective and total pixel area

QHY often lists two pixel arrays. The QHY268 page gives an effective area of 6252 × 4176 and a total area of 6280 × 4210 that, in QHY’s words, includes the optical-black and overscan areas. Those extra rows and columns do not record sky. Computed with the 3.76 µm pitch, the effective array is 23.51 × 15.70 mm and the total array 23.61 × 15.83 mm; at 600 mm that is 2.24° × 1.50° versus 2.25° × 1.51°. Our tables use the effective figure.

The QHY533 is harder. Its product page publishes only “Total Pixel Area 3008*3028”, again including optical-black and overscan rows, plus “9 Megapixels” effective. With no separate effective array to use, the table works from 3008 × 3028. That makes the computed frame 11.39 mm tall, 0.075 mm (0.66 %) more than the 3008 × 3008 that other makers publish for the same IMX533. At 1000 mm the difference is 39.1′ versus 38.9′. The IMX533 comparison shows the rows side by side.

QHY’s own Specifications Comparison page adds a labeling wrinkle: it puts 6280 × 4210 and 3008 × 3028 under “Effective Pixel Area” while noting in the same cell that they include optical-black and overscan areas. The product pages call the same numbers “Total”. We follow the product pages.

Where QHY does publish millimetres

When QHY gives a size, it matches pixels × pitch closely. The QHY294M Pro’s 19.28 × 12.95 mm is exactly 4164 × 2796 at 4.63 µm. The QHY183’s 13.3 × 8.87 mm compares with a computed 13.31 × 8.84 mm, a 0.03 mm gap in height. The QHY294 page also describes a second readout mode that unlocks the sensor’s on-chip binning: 8340 × 5644 pixels at 2.315 µm and 12 bits. The field is unchanged, but the image scale halves, from 1.59″/px to 0.80″/px at 600 mm. Our table lists the default 4.63 µm mode.

Back focus depends on the body version

QHY’s figures vary with the version. The current QHY268 PH bodies list 14.5 mm (±0.2), and the product page notes that the color model moved to the shorter top part in January 2023, while the earlier QHY268C had 17.5 mm. The QHY600 page lists 17.5 mm plus a 6 mm CAA for the standard PH body and 14.5 mm for the SBFL version. The QHY533M and QHY533C differ from each other: 14 mm and 17 mm. Check the exact version before working out spacers; the back focus guide covers the arithmetic.

Cooling figures and the miniCAM8M

QHY quotes cooling at a +20 °C test ambient and, for the QHY268, QHY533 and QHY600, splits it by exposure: typically 35 °C below ambient for exposures over one second and 30 °C for sub-second frames. The miniCAM8M is listed with a 45 °C delta and is not a guide camera: it combines a cooled IMX585 with a built-in 8-position filter wheel and a 17.5 mm back focus. QHY again gives only a total pixel area for it, 3856 × 2180.

Two discontinued bodies

The QHY410C and QHY163M appear on QHY’s Discontinued Products page as discontinued in 2023, with their specifications kept in an archive table. The QHY163M’s sensor is described only as a Panasonic 16-megapixel 4/3-inch chip, with no part number. Its full well is given as a range, 18–20 ke⁻, so the table leaves that cell as not published rather than picking a value. The QHY410C uses the full-frame IMX410 with 5.94 µm pixels, which reaches 1″/px only at 1225 mm.