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www.qhyccd.com
GENERAL INFORMATION
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.
2.
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 flat field 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.
To summarize, 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:
𝑀𝑎𝑥𝑖𝑚𝑢𝑚 𝑇𝑒𝑙𝑒𝑠𝑐𝑜𝑝𝑒 𝐵𝐹 ≤ 𝐶𝑎𝑚𝑒𝑟𝑎 𝐵𝐹 + 𝐹𝑖𝑙𝑡𝑒𝑟𝑤ℎ𝑒𝑒𝑙 𝐵𝐹 + 𝑂𝐴𝐺 𝐵𝐹 + 𝑎𝑑𝑎𝑝𝑡𝑒𝑟 𝐵𝐹
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
163、294*、550
10mm
(Not incl. adapter# 020085)
Medium sized
cooled camera
QHY128、168、247、367、268、600
18mm
(Not incl. 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
3.
The thread
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.
