[ASI2600 Guide] 4 Connection methods to get 55mm back focus length

People are asking the connect methods of ASI2600MM Pro: How to use it with the new 36mm EFW? How to reach the 55mm back focus distance? What accessories I need and can I add the original OAG or OAG-L into my imaging train?

To get all of the answers of these questions, you need to read this instruction.

1. The Basic Connection Solution:

No filter wheel or filter drawer in this solution, only adapters or the original OAG.

Suitable for telescope up to f/4.8

You can change the T2-M48 16.5mm into the original OAG. But please note that the OAG will block the sensor in a bit if the thread of the end side of your telescope is M42.

2. Using 36mm EFW:

This solution can be divided into 3 cases: with the original OAG and adapters, or with the OAG-L, or with adapter only.

1) With the original OAG or adapters:

Suitable for telescopes up to f/5.4

In this case, the connection method can be very convenient with the use of threads. You can take the full advantage of the accessories you have. A few notes:

– The original OAG can be replaced to T2-M48 16.5mm extender;

– The original 36mm EFW and new 36mm EFW will both work;

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

– The back focus distance in this case is 56mm;

– Like we mentioned above, the original OAG will block the sensor in a bit if the thread of the end side of your telescope is M42.

2）With OAG-L:

Suitable for telescopes up to f/4.2

You can leave the adapters aside and directly connect the new 36mm EFW to the camera via screws in this case, the distance from the sensor and the filter will also be much closer. A few notes:

– The M42 sensor tilt adapter attached to the camera need to be taken off;

– The original OAG can not be replace 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.

– M48/54/68 sensor tilt adapter can be bought separately.

3）No OAG, with adapter only:

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. Using 2”EFW:

Being the same as Solution #2, this solution can be divided into 2 cases: with the original OAG and adapters, or with the OAG-L.

1) With the original OAG or adapters:

– The back focus distance in this case is 56mm;

2）With OAG-L:

This method is quite similar to Solution #2 → 2), so we do not go into details here.

4. Using 2” Filter Drawer:

Above the 4 solutions for the ASI2600MM Pro APS-C camera to reach the 55mm back focus length. Indeed there are more than 4 solutions in total, but these are what we most recommend. If you have any questions about this guide, please do contact us, we are glad to help!