Discovery Astrophotography with ZWO ASTRO

The best solution of 55mm back focal length

The back focal length is advised by telescope manufacturers. Since most telescopes have a 55mm back focal length, we are here to provide detailed instructions for all ASI cooled cameras.
Please be noted that this tutorial only applies to 55mm back focal length.  And some adapters are not included in your camera box, thus you might need to purchase them separately.


1. 4/3”, 1” and small format cooled cameras:

ASI1600/294/183/533/991/990

1) Without filter drawers or filter wheels:

small frame cooled camera -1
small frame cooled camera + OAG

2) With 1.25”/36mm/31mm EFW:

small frame cooled camera + 1.25inch 31mm 36mm EFW
small frame cooled camera + 1.25inch 31mm 36mm EFW + OAG

3) With 2” EFW:

small frame cooled camera + 2inch EFW

Note: The total back focal length of this solution is 56mm; The two adapters T2-M48 16.5mm and M48-M42 could be replaced by the M48-M48 16.5mm extender.

small frame cooled camera + 2inch EFW + OAG

Note: The total back focal length of this solution is 56mm; The T2-tilter needs to be bought separately.

4) With 2” filter drawer:

small frame cooled camera + M42 filter drawer

Note: The two adapters T2-M48 16.5mm and M48-M42 could be replaced by the M48-M48 16.5mm extender.

small frame cooled camera + M42 filter drawer + OAG

5) With OAG-L and 2” filter:

If you have an OAG-L, but do not have a filter wheel to reach 55mm back focal length. Then you can use the M54 adapter instead. It also allows you to add a 2” filter into the image train.

55mm back focal length-small format cooled cameras

2. APS-C cooled cameras:

ASI2600/071

1) Without filter drawers or filter wheels:

APS-C format cooled camera - 55mm back focus length solution
APS-C format cooled camera + OAG

2) With 36mm EFW:

连接普通OAG或者接环-英文

Note: T2-T2 2mm adapter can be found in the package of 36mm EFW;

连接OAG-L和新36mm-EFW-英文

Note: The M42 sensor tilt plate attached to the camera needs to be taken off. You may need to re-adjust the tilt when re-installing the plate; The original OAG can not be replaced with OAG-L, but if you have the M68 OAG, you can use the M68 OAG instead; This method does not support the telescopes with M42 threads at the end side.

连接M42M-M48F-22.5L和36mm EFW-英文

Note: This method only supports the telescopes with M42 or M48 threads at the end side. The M42M-M48F 22.5mm extender needs to be bought separately.

3) With 2” EFW:

APS-C format cooled camera + 2inch EFW

Note: The total back focal length of this solution is 56mm; The two adapters T2-M48 16.5mm and M48-M42 could be replaced by one adapter M48-M48 16.5mm.

APS-C format cooled camera + 2inch EFW + OAG

Note: The total back focal length of this solution is 56mm.

连接OAG-L和2寸EFW-英文

Note: The M42 sensor tilt plate attached to the camera needs to be taken off, and you may need to re-adjust the tilt when re-installing the plate back; The original OAG can not be replaced to OAG-L, but if you have the M68 OAG, you can also use the M68 OAG instead; This method does not support the telescopes with M42 threads at the end side.

4) With 2” filter drawer:

APS-C format cooled camera + M42 filter drawer

The two adapters T2-M48 16.5mm and M48-M42 could be replaced by one adapter M48-M48 16.5mm.

APS-C format cooled camera + M42 filter drawer + OAG

5) With OAG-L and 2” filter:

If you have an OAG-L, but do not have any filter wheel to reach 55mm back focal length. Then you can use the M54 adapter instead. It would also allow you to add a 2” filter into the image train.

55mm back focal length-APS-C cooled cameras

3. Full frame cooled cameras:

ASI6200/2400

1) Without filter drawers or filter wheels:

full frame cooled camera - 55mm back focus length solution
full frame cooled camera + OAG

Note: The above two solutions will both block the sensor a little bit.

2) With 2” EFW:

6200-55mm-backfocus-solution-2-2
全画幅冷冻相机加OAGL连接方案-英文(1)

Note: The M42 sensor tilt plate attached to the camera needs to be taken off, and you may need to re-adjust the tilt when re-installing the plate; The original OAG can not be replaced to OAG-L, but if you have the M68 OAG, you can also use the M68 OAG instead; This method does not support the telescopes with M42 threads at the end side.

3) With 2” filter drawer:

full frame cooled camera + M54 filter drawer

Note: The back focal length of this solution is 56mm.

full frame cooled camera + M54 filter drawer + M68 OAG

Note: This solution only applies to telescopes with M68 interface threads. If the threads of your telescope is M42 or M48, then we recommend you DIY the relative adapters or choose the 2” EFW.

4) With OAG-L and 2” filter:

If you have an OAG-L, but do not have & want to use any filter wheel to reach 55mm back focal length. Then you can use the M54 adapter instead. It would also allow you to add a 2” filter into the image train.

55mm back focal length-full frame cooled cameras

 

 ASI camera connecting with OAG diagram:

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