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Adapters Specifications
2019 / 11 / 21


The adapter system stated in this document is intended for the following model: (small to medium) sized cooled CMOS camera, QHYOAG series, QHYCFW filter wheel series, A series integrated CCD camera。 The legacy CCD cameras (QHY23 and before) require custom adapters. Scientific grade camera usually involved custom adapter solution, which is not included in this document.
Prior to your selection, there are few basic concepts:
  1. Back focus distance: To simplified, this is the centered-focus distance of a lens or group of lenses. In camera system, this is distance of which the focused image from the center of a lens or group of lenses projected onto a film or sensor. In another word, this is the distance between the back of lens to the camera sensor. This specification can usually be found on the lens or telescope. This is the most important specification for camera to acquire a sharp image through an optical instrument.
  1. How to reach the optimum back focus distance: In general, the back focused distance is a fixed specification. The flange distance in conventional camera system is equivalent to back focus distance; for example, the modern CANON DSLR EF lens system has a back focus of 44mm. Unlike the DSLR lens flange, the back-focus distance of a telescope is not fixed and covers a range of distance. This is due to the differences of optical structure and focusing system. Alternatively, if a flatfield generator(flattener) is used in an Astro-Imaging chain, the back-focus system of the flattener is used for determining the correct back focus distance. In this document all listed back focus consumption is de facto consumption measurement rather than the measurement of the adapter.
To summarized, the correct telescope back focus distance (BF, and this is the distance behind focuser, flattener and or other optical correctors) should be calculated per follow:

The following table includes the back-focused system consumed by respective the QHYCCD camera.
Name Model Back focus Consumed
Small sized cooled Camera QHY183、178、224、290、174
10+8 mm
10mm: Camera body
8mm: adapter# 020085 (standard top)
Medium sized cooled camera QHY128、168、247、367、268、600 18+6 mm
18mm: Camera body
8mm: adapter# 020002
* The QHY294 used a bigger housing body only and the adapter remain the same of small sized camera.
Name Model Back focus consumed
OAG S/M/L 10mm
QHYCFW3 S 15.5mm/20mm
M 17mm/20.5mm
L 21.5mm
XL 21.5mm

The table below listed all the adapters available in QHYCCD. Follows the table, there are few sample solutions.

Customized screws: Screws are required to mount the adapter otherwise the adapter is mount with threads. In certain cases, tailored screws are required to fit the specific thickness of the system.  
  • M represent external thread, for example, M42 represents external thread of a radius of 42mm.
  • F represent internal thread, for example, M54 represents internal thread of a radius of 54mm.

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