Skywatcher 0.77 Field flattener / reducer back focus confusion?

[bluesilver]

Hi,  I have a Skywatcher Esprit 150 and it came with the Skywatcher 0.77 flied flattener / reducer,

Now i may be over reading the instructions on the box, but to me it appears to be a tad complicated in what they are trying to say.

It says: 

> 75mm back focus* 

but then under this is says:

*>75mm with custom made adaptor, 55mm with standard adaptor

Below is a image if what is written on the box

So basically I am just trying to find out what is the correct back focus,  Is it 55mm?

As it seams a bit odd saying 75mm with a custom made adaptor as a custom made adaptor could be anything.

So below is what i have assembled,  it is the 0.77 flattener/reducer straight out of the box,  a 37.5mm spacer ( ZWO 16.5mm and 21mm ) and my camera asi2600 with 17.5mm distance to the sensor.

All up from the flattener to the sensor is 55mm

Is this the correct back focus?  below is a photo of what i have.

Any advice would be appreciated.

Cheers.

 

[tomato]

I set the camera spacing  on the basis that the standard adapter with the Esprit 150 FR gave 55 mm backfocus, and had no issues.

[bluesilver]

Cheers,

I will give the 55mm spacers a go next time it is a clear night.

Not sure why Skywatcher made a the main note that it is 75mm back focus,  then when you read the fine print under it all ,  they say *>75mm with custom made adaptor, 55mm with standard adaptor.

Makes it a tad confusing,  or at least to me it did.

Cheers.