QHYCCD Astronomy Camera Adapter Solution

Adapter & BFL Solution

Kit A1	USD40
Kit A2	USD42
Kit A3	USD35
Kit D1	USD40
Kit D2	USD58
Kit D3	USD58
Kit E1	USD35

QHY offers a very comprehensive and flexible adapter system that allows our cameras to achieve focus to meet mainstream needs of most users (e.g., Multi-Purpose Coma Corrector, Canon lens adapter, Nikon lens adapter, etc.). Users can choose the corresponding adapter set according to their needs to ensure focus.

Adapter System Introduction

QHYCCD has adhered to the adapter system of 6-screw + spacers for years. Compared to the typical threaded connection, this method is more robust, ensuring a stable relative position between various components (threads often have errors, leading to the final position after fixation being inaccurate). At the same time, it facilitates fine-tuning of the back focus length.

QHYCCD has consistently aimed to enhance the stability and user-friendliness of its hardware products. In terms of adapter systems, we have been continuously optimizing to adapt to the evolving needs of users, striving to improve the user experience.

Adapter System V1.0:

For the Adapter System V1.0 (before 2020), we provided various thicknesses of spacers for users to choose and purchase freely. However, for users, especially beginners, calculating the back focus and selecting the appropriate spacer can be challenging, and the tuning process is complex. Therefore, we introduced the 2.0 version.

Adapter Syatem V2.0:

In the Adapter System V2.0 (from 2021 onwards), we adopted standardized adapter kits. Various adapter kits can meet the needs of most mainstream requirements (such as correctors for 55mm/56mm back focus M48/M54 interfaces, Canon/Nikon DSLR lenses, etc.), with the adapter kit of 55mm M48 output serving as the standard accessory for most cooled cameras. Users can choose the corresponding adapter kits according to their needs, and install them following the adapter kit instruction, without the need for self-measurement and matching.

Adapter System V2.5:

Building upon the V2.0, the current V2.5 (since 2023) further enhances the compatibility and expandability of the adapters.

a. The standard adapter kits B1/C1/G1 for mainstream products have been expanded. While the V2.0 only supported adaptation to the 55mm/M48 specifications, the V2.5 offers cross-compatibility for both 55mm/56mm back focus length and M48/M54 threads. This allows coverage for back focus length and interface diameter requirements of most optical components such as correctors and telescopes.

b. By widening compatibility between different specifications, the current standard items can now facilitate connections and back focus length adaptations for some unofficially recommended combinations, such as achieving a connection between OAGL-Pro and CFW3M using the adapters.

c. Besides, 0.5mm/1mm spacers have been added as independent products to meet the needs of a few users with extremely high requirements for back focus length.

Back Focal Length Defined

Back Focal Length (BFL), in the commercial camera field, refers to the design distance from the center of the rear lens element to the surface of the sensor. Generally, the lens will only focus correctly at infinity if the camera’s back focal length meets the standard requirements provided by the lens manufacturer. This is also true for many Multi-Purpose Coma Correctors designed to be used on telescopes before the camera.

Optical system	Specifications
Typical Multi-Purpose Coma Corrector	55mm, M48 Threads
Takahashi Epsilon Reflector Series	56mm, M54 Threads
Canon 35mm lens	44.1mm
Nikon 35mm lens	46.5mm
…	…

In addition, there are also some other special specifications, such as the refractor/reflector telescopes from Takahashi, which have different back focus standards based on their respective models.

Note: Not all astrophotography gears have specific BFL requests, for example, some refractor scopes with internal flat correctors. In such cases, you needn’t use the following adapter kits. Instead, you can use a T ring or any adapter that can help connect your camera and scope.

"Back Focus Consumed" Defined

When an optical system requires the sensor of the camera to be located at a specific distance from the last optical element, mechanical spacer adapters are used to position the camera at the right location. If the camera system also includes a filter wheel and an OAG, for example, between the camera and the telescope, the space required for these items must be taken into account. As a simplified explanation, for example, if a telescope’s field flattener requires the camera focal plane to be 55mm behind the last optical element, and the filter wheel is 20mm thick, and the OAG is 10mm thick and the sensor is set 10mm inside the camera then these items all take up 20+10+10=40mm of the back focal distance. Still, the camera needs to be 55mm away so we need to add spacers that take up this remaining 15mm. This also means that if you have an optical system that requires 55mm of backfocus distance and your filter wheel is 25mm thick and the OAG is 20mm thick and the sensor in the camera is 17mm from the front plate, then these items take up 25+20+17=62mm of backfocus. Too much! In this case something has to go to reduce the total back focus distance of the camera to 55mm or a different optical configuration must be found.

For the convenience of calculation, all the data displayed are the increase in the back focal length taken up by using the adapter, which is not necessarily equal to the thickness of the component itself. All the adapter data provided by QHYCCD are based on the focal length increment.

Recommended Combinations

At present, our adapter combinations are based on the focal length of the following combinations, which are also our recommended combinations. If you use combinations other than those recommended, the adapter set may not achieve its purpose.

Recommended Combinations for Mono Cameras

The full-frame mono camera is available in two models: QHY600M-PH (Standard Version) and QHY600M-PH SBFL (Shorter Back Focal Length Version). It is recommended to use them with CFW3L+OAGM. If you have specific requirements for the back focal length of your optical system, such as 55mm/56mm or when using a DSLR lens, it is advised to choose the QHY600M-PH SBFL (Shorter Back Focal Length Version). Additionally, some users have reported possible vignetting when using QHY600 with M48 MPCC. For better optical performance, it is suggested to connect full-frame cameras like QHY600 to telescopes using M54 or larger openings.

The APS-C mono camera QHY268M supports two types of filters: a 2-inch mounted filter using CFW3L, or a 36mm unmounted filter using CFW3M-SR 7*36mm version. According to our estimation, the 36mm filter can be used when the focal ratio of the main scope is greater than f/4. If you are using a telescope with a small focal ratio, such as f/2.8, it is recommended to use the 2-inch mounted filter. Additionally, if you choose to use unmounted filters with filter masks, it is recommended to use the thicker SR version to provide more space inside the filter wheel.

For cameras with a 3/4-inch sensor, like QHY294, it is recommended to use CFW3M-SR+OAGM. For cameras with a 1-inch or smaller sensor, like QHY533, it is recommended to use CFW3S-SR+OAGS.

Camera	CFW	OAG	Adapter Kits	Filter Size
QHY461M-PH	QHYCFW3-XL	QHYOAGL-Pro	–	50mm Square
QHY600M-PH-SBFL	QHYCFW3-L	QHYOAGM-Pro	B1	2” Mounted or 50mm Round
QHY600M-PH-SBFL	QHYCFW3-XL	QHYOAGL-Pro	B1	2” Mounted or 50mm Round
QHY600M-PH	QHYCFW3-L	QHYOAGM-Pro	C1	2” Mounted or 50mm Round
QHY600M-PH	QHYCFW3-XL	QHYOAGL-Pro	C1	2” Mounted or 50mm Round
QHY268M	QHYCFW3L QHYCFW3M-SR QHYCFW3M-US	QHYOAGM-Pro	B1	2” Mounted or 36mm Round
QHY294M	QHYCFW3M-SR QHYCFW3M-US	QHYOAGM	A1	36mm Round
QHY533M	QHYCFW3S-SR	QHYOAGS	F1	1.25” Mounted

Recommended Combinations for Color Cameras

Color cameras usually do not need to be paired with a filter wheel. There is no need to switch filters, or only a few filter changes are necessary using a filter drawer. If a filter wheel is required for special reasons, refer to the combination recommendations for the corresponding mono model of the camera.

Camera	CFW	OAG	Adapter Kits	Filter Size
QHY600C-PH QHY600C-PH-SBFL	–	QHYOAGM-Pro	G1	2” Mounted (IR-Cut or Duo Band)
QHY268C	–	QHYOAGM-Pro	G1	2” Mounted (IR-Cut or Duo Band)
QHY533C	–	–	E1	2” Mounted (IR-Cut or Duo Band)

Adapter Kits Introduction

Note: if you do not want to use an OAG in the above combinations, we provide an additional 10mm spacer adapter in some kits to replace it.

B1 (QHY268M, QHY600M-PH SBFL)

The New Combo B1 is designed to be more flexible to achieve multiple output specifications. Since June 2023, we are adding a 5mm spacer with M54 threads into Adapter kit B1. This addition gives the user a choice of terminating the output in either M48 or M54 threads. You can get 55/56mm BFL with M48/M54 threads according to your needs. Since are standard accessories included with the camera, this addition has no affect on the price. 55mm M48/M54 are suitable for standard flatteners and multiple purpose coma correctors (MPCC), while 56mm M54 threads are common for Takahashi reflectors.

Note: Please position the OAG as far forward as possible (for example, placing it under the M48 thread), and extend the OAG prism slightly outward to ensure simultaneous focus for both the main camera and the guiding camera.

In 2023, we launched the new version of the QHYOAGM-Pro with a larger prism. Its thickness is 12mm, so it is necessary to reduce the spacer thickness by 2mm in the COMBO above while keeping the rest part unchanged.

The QHY600M-PH SBFL and QHY268M with CFW3L filter wheel can fit an optional Canon EF or Nikon F Lens Adapter without additional spacers. Smaller filter wheels may require additional spacers.

C1 (QHY600M-PH/L)

Since June 2023, we are adding a 5mm spacer with M54 threads into Adapter kit C1. This addition gives the user a choice of terminating the output in either M48 or M54 threads. Since C1 are standard accessories included with the camera, this addition has no affect on the price list.

Note:

Combo C1 is the solution without OAG. The QHY600M-PH or QHY600M-L with CFW3L and OAG result in a backfocus greater than 55mm. Therefore, if you must limit this BF distance to 55mm due to a corrector lens or DSLR lens, we recommend the QHY600M-PH SBFL.

If you need more than 7 x 50mm filter positions for the QHY600, you can use the CFW3XL filter wheel with 9 x 50mm filter carousel.

E1 (QHY533C, QHY294C, etc.)

Adapter Kit E1 can be directly connected to the 55mm BFL M48 interface MPCC, or Nikon / Canon DSLR lens (need to purchase another DSLR lens adapter).

E1 is designed for QHY533C, 294C, 163C, 183C, 174C. Of course, if you use 163M/294M/183M/174M while a filter wheel or OAG is not needed, you can use E1 as well.

F1 （QHY533M）

QHY533M external use of threaded interface can be directly connected to the small filter wheel. This time we will launch a special standard small filter wheel version together with the 533M, which can be assembled directly by the user externally without removing the disc. When the QHY533M + filter wheel combination is connected to a DSLR lens, only an additional DSLR lens adapter ring (sold separately) is required to complete the focus.

A1-A3 (QHY163M, QHY294M)

A1: Connecting MPCC that requires 55mm BFL and M48 interface to Camera with Filter Wheel and OAG.

Note:

If you only own CFW3M-SR whose BFL is 20.5mm rather than 17.5mm, this adapter combination can still be used, just remove the 3mm and 0.5mm adapters.
If your MPCC requires a BFL different from 55mm, this adjustment can be made by selecting the appropriate spacer between the MPCC and the OAG. For example, an MPCC that requires 57.5mm can be used instead by adding a spacer ring or rings that add 2.5mm of BFL. to the diagram above.
If you don’t use an OAG, you can use a 10mm spacer adapter in the adapter kits to replace the original position of OAG.
Put OAG at the position next to the M48 Output to make both main cam and guiding cam focused.

A2: Connect Canon lens with filter Wheel. You need to remove the filter wheel and the original connection interface of the camera and replace it with a new adapter.

A3: Connect Nikon F Lens to Camera with Filter Wheel

D1-D3 (QHY600C-PH,QHY247C,367C,168C,128C,410C, etc.)

Generally speaking, there’s no need for an OSC (one shot colored) camera to match filter wheel. If there’s any special needs, please refer to mono cam combos and choose the corresponding filter wheel. All OSC cams use OAG M if needed.

Model	BFL Consumed
QHY600C/410C/367C/128C/247C/168C	17.5mm+6mm (CAA)
QHY268C (Version before 2022)	17.5mm+6mm (CAA)
OAGM	10mm

*About IR-Cut filter：

The sealing glass of QHY OSC cameras whose format are above APS-C is AR glass instead of IR/Cut filter. That’s because when the sensor size is bigger, if IR/Cut is closed to sensor, it’s easy to cause haloing effect on image. We use IR/Cut filter as sealing glass on 4/3 format cameras or below, like 163C, 183C; as for big sensor OSC cams, such as 268C, 367C, we provide a special adapter for fixing 2-inch IR/Cut filter at a farther position from the sensor, or users can fix the filter inside the default T mount.

D1: Connecting MPCC with 55mm BFL and M48 interface

D2: Connecting Canon EF Lens

D3: Connecting Nikon F Lens

0.5mm/1mm M54 Spacer

0.5mm/1mm Spacer is designed for those who have vary strict requirments of back focal length of the optical system, or the default 55/56mm solutions are not suitable (for example, some correctors require 57.5mm BFL). Combined with our Adapter Kits, the spacer can be used for precise adjustment.

M54/M42 All-in-one Accessory Packages

First please confirm whether there are specific requirements of BFL on your equipment. If not, just use a standard T-ring to connect the telescope.

If you do have strict requirements of BFL, since 7/23 we have provided 0.5mm and 1mm spacers as purchasable items for a precise adjustment.

If all the existing combo kits cannot meet your demand, such as special back focus requirements, we also offer M42 and M54 all-in-one adapter packages that contains nearly all of the adapters we provide in the kits: 0.5, 1, 2, 3, 7 and 14mm spacers can be combined to make any back focus needed from 0.5mm to 27.5mm.

In most cases, we recommend the M54 All-in-one Kit. The M42 All-in-one Kit is only suitable for use with the QHY183M and QHYCFW3S.

Specifications

Model	Product No.	Compatible with	To Connect	Kit Includes	Note
Combo A1	020100	QHY294M/163M + CFW3M-US + (OAGM)*	55mm BFL M48 Threads	5mm M54-M48 Threads Adapter13mm Spacer1 0.5mm Spacer1 10mm Spacer1 22mm M3 Screws*8	This Combo A1 is included as a standard accessory with the QHY294M
Combo A2	020101	QHY294M/163M +CFW3M-US	Canon EF Lens	10mm M54 Canon EF Adapter14mm M54 Screwed Adapter1 3mm Spacer1 1mm Spacer1 Cam Top Adapter (originally 020063) 10mm M3 Screws*8	_
Combo A3 (Nik Adapter1)	020102	QHY294M/163M +CFW3M-US	Nikon F Lens	10mm M54 Nikon F Adapter*1	_
Combo B1	020103	QHY268M+CFW3L/CFW3M-US + (OAGM)orQHY600M-PH SBFL +CFW3L + (OAGM)	55mm/56mm BFL M48 Threads 55mm/56mm BFL M54 Threads	5mm M54-M48 Threads Adapter15mm M54-M54 Threads Adapter1 3mm Spacer3 1mm Spacer1 10mm Spacer1 24mm M3 Screws8 28mm M3 Screws*8	This Combo B1 is included as a standard accessory with (a) QHY268M and (b) QHY600M-PH SBFL version

Model	Product No.	Compatible with	To Connect	Kit Includes	Note
Combo C1	020106	QHY600M-PH+CFW3L	55mm/56mm BFL M48 Threads 55mm/56mm BFL M54 Threads	5mm M54-M48 Threads Adapter1 5mm M54-M54 Threads Adapter1 1mm Spacer1 7mm Spacer1 14mm M3 Screws*8	C1 is supplied as a standard accessory with QHY600M-PH
Combo D1	020107	QHY268C (Version before 2023)/ QHY600C-PH/QHY168C/ QHY247C/QHY128C/QHY410C/ QHY367C	55mm M48 Threads	5mm M54 to M48 Adapter12.5mm 2inch Filter Fixer (Original Name 020055) 10mm Spacer1 14mm Spacer1 36mm M3 Screws8	D1 is supplied as a standard accessory with QHY600CQHY268C (Version Before 2023)
Combo D2	020108	QHY268C (Version before 2023)/ QHY600C-PH/QHY168C/ QHY247C/QHY128C/QHY410C/ QHY367C	Canon EF Lens	10mm M54 Canon EF Adapter14mm M54 Screwed Adapter1 2.5mm 2inch Filter Fixer (Original Name 020055) 3mm Spacer1 1mm Spacer1 14mm M3 Screws*8	_
Combo D3	020109	QHY268C (Version before 2023)/ QHY600C-PH/QHY168C/ QHY247C/QHY128C/QHY410C/ QHY367C	Nikon F Lens	12mm M54 Nikon F Adapter14mm M54 Screwed Adapter1 2.5mm 2inch Filter Fixer (Original Name 020055) 3mm Spacer1 1mm Spacer1 0.5mm Spacer1 14mm M3 Screws8	_
Combo E1	020110	QHY294C / QHY163C QHY183C/ QHY533C	55mm M48 Threads	Three Customized adapters and a 0.5mm spacer	This Combo E1 is included as a standard accessory with the QHY533C
Combo F1	020120	QHY533M	55mm M48 Threads	8mm M42-M48 Threads Adapter1 3mm Spacer3 10mm Spacer1 23mm M3 Screws8	This Combo F1 is included as a standard accessory with the QHY533M
M54 All-in-one Kit	020111	All Cooling CMOS Cameras CFW3M-SR CFW3M-US CFWL OAGM		5mm M54 to M48 Adapter1 3mm M54 to M42 Adapter1 2.5mm 2inch Filter Fixer (Original Name 020055)1 4mm M54 Screwed Adapter (Original Name 020070)1 Cam Top Adapter (Original Name 020063)1 0.5mm/1mm/2mm/3mm/7mm/10mm/14mm/ Spacer1 8mm M3 Screws8 10mm M3 Screws8 12mm M3 Screws8 14mm M3 Screws8 16mm M3 Screws8 21mm M3 Screws8 24mm M3 Screws8 28mm M3 Screws8 36mm M3 Screws8 50mm M3 Screws8
M42 All-in-one Kit	020112	QHY183MCMOS CFW3S-SR CFW3S-US OAGS		8mm M42 to M48 Adapter1 3mm M42 to Screwed Adapter1 Cam Top Adapter (Original Name 020063)1 0.5mm/1mm/2mm/3mm/7mm/10mm/ Spacer1 10mm M3 Screws8 12mm M3 Screws8 21mm M3 Screws*8

M57, The Ring Nebula

Astrobin IOTD 2025 Jul 31

Astrophotographer
Nico Carver

Adapter & BFL Solution

Topic DOWNLOAD PDF

Recommended Combinations for Mono Cameras

Recommended Combinations for Color Cameras

QHYCCD

M57, The Ring Nebula Astrobin IOTD 2025 Jul 31

Astrophotographer Nico Carver

Adapter & BFL Solution

Related Products

Topic DOWNLOAD PDF

Recommended Combinations for Mono Cameras

Recommended Combinations for Color Cameras

QHYCCD

M57, The Ring Nebula

Astrobin IOTD 2025 Jul 31

Astrophotographer
Nico Carver