Connecting to Nikon Lens

Alicja

What are all the interfaces I need to account for when connecting:
ASI2600MM Duo + 7position Filter Wheel + Sigma Lens (Nikon Lens)

What spacers/adapters do I need?

Alicja

Tech@ZWO

1.Camera to Filter Wheel:

If your filter wheel has an M54 thread, connect it directly to the ASI2600MM Duo.
If the filter wheel has an M42 thread, use an M42 to M54 adapter.

2.Filter Wheel to Lens:

Use an M54 to Nikon F-mount adapter to attach your Sigma lens to the filter wheel.

3.Spacers/Backfocus:

Add a spacer or backfocus adjustment ring between the filter wheel and the lens if necessary to achieve the correct backfocus distance (typically 55mm for most DSLR lenses, or adjust according to the lens specs).

4.Checking Backfocus:

Ensure that the overall backfocus distance from the lens to the camera sensor is correct. This includes the filter wheel and any spacers. For the ASI2600MM Duo, the backfocus distance is 17.5mm, and the Sigma lens typically requires 55mm. If the filter wheel adds additional length, ensure the total backfocus adds up to 55mm.

Alicja

I was unable to obtain focus.

Filter Wheel has M54 thread and is directly connected to ASI2600MM Duo.
Sigma 24-70mm F2.8 DG OS HSM | A

Per above recommendation, I have tried the following to obtain 55mm backfocus:

Filter Wheel = 20mm
Nikon F-mount adapter = 12.5mm
Spacer between Filter Wheel and lens adapter = 5mm
ASI2600MM Duo backfocus is 17.5mmm
Total back focus = 55mm ⇒ focus could not be obtained

Using the instructions provided in the documentation that came with ASI2600MM Duo:

Filter Wheel = 20mm
Nikon F-mount adapter = 12.5mm
ASI2600MM Duo backfocus is 17.5mmm
Total back focus = 50mm ⇒ focus could not be obtained
Note: This appeared to be the closest to focus

Other spacers tried:

Spacer between Filter Wheel and lens adapter = 4mm
Total back focus = 54mm ⇒ focus could not be obtained

Spacer between Filter Wheel and lens adapter = 9mm
Total back focus = 59mm ⇒ focus could not be obtained

Spacer between Filter Wheel and lens adapter = 16.5mm
Total back focus = 66.5mm ⇒ focus could not be obtained

Spacer between Filter Wheel and lens adapter = 21mm
Total back focus = 71mm ⇒ focus could not be obtained

Spacer between Filter Wheel and lens adapter = 37.5mm
Total back focus = 87.5mm ⇒ focus could not be obtained

None of the above combinations worked. Please advise next steps

Alicja

I was unable to obtain focus.

Filter Wheel has M54 thread and is directly connected to ASI2600MM Duo.
Sigma 24-70mm F2.8 DG OS HSM | A

Per above recommendation, I have tried the following to obtain 55mm backfocus:

Filter Wheel = 20mm
Nikon F-mount adapter = 12.5mm
Spacer between Filter Wheel and lens adapter = 5mm
ASI2600MM Duo backfocus is 17.5mmm
Total back focus = 55mm ⇒ focus could not be obtained

Using the instructions provided in the documentation that came with ASI2600MM Duo:

Filter Wheel = 20mm
Nikon F-mount adapter = 12.5mm
ASI2600MM Duo backfocus is 17.5mmm
Total back focus = 50mm ⇒ focus could not be obtained
Note: This appeared to be the closest to focus

Other spacers tried:

Spacer between Filter Wheel and lens adapter = 4mm
Total back focus = 54mm ⇒ focus could not be obtained

Spacer between Filter Wheel and lens adapter = 9mm
Total back focus = 59mm ⇒ focus could not be obtained

Spacer between Filter Wheel and lens adapter = 16.5mm
Total back focus = 66.5mm ⇒ focus could not be obtained

Spacer between Filter Wheel and lens adapter = 21mm
Total back focus = 71mm ⇒ focus could not be obtained

Spacer between Filter Wheel and lens adapter = 37.5mm
Total back focus = 87.5mm ⇒ focus could not be obtained

None of the above combinations worked. Please advise next steps

retman

Alicja Hello, the correct spacing for Nikon lenses is a total of 46.5mm (not 55mm). I note that the closest to focus you achieved is with 50mm. In all cases you have TOO much space between the flange and the sensor.

Alicja

What is the thickness of the Nikon F-mount adapter? I do not think I have it correct of 12.5 mm. I am using ZWO Nikon Lens Adapter for ZWO 2" Electronic Filter Wheel # EFW2-Nikon
https://agenaastro.com/zwo-nikon-lens-adapter-for-2-electronic-filter-wheel-efw2-nikon.html

Alicja

I removed the the sensor tilt adapter, what is the new backfocus of the ASI2600MM Duo?

Alicja

retman

Alicja The optical length of the Nikon F-mount adapter is 14mm (total length/thickness is 18mm, optical length is 14mm). With the 5mm tilt adapter removed from the camera (per the ZWO procedure) the camera optical length becomes 12.5mm (i.e., 17.5mm - 5mm). From the ZWO drawings, the EFW2 appears to be 20mm. So, 20mm + 14mm + 12.5mm =46.5mm (which is the required Nikon/Sigma for Nikon back spacing)