Imaging with ASI and Nikkor lenses

It would be nice to image through some of the Nikkor lenses with the ASI183mm Pro. In some cases you reach telescope fields and resolution.

As an example: the 300mm F2.8 Nikkor, attached to the ASI 183mm, delivers a field of 151′ on 100′ with 1,65″ pixelsize.

The Nikon FF D750, combined with the Esprit 120mm, delivers a field of 146′ on 98′ with 1,46″ pixelsize.

Comparing the combinations Esprit/D750 and ASI/300mm: the fields are almost overlapping

Actually the Nikkor 300mm can be seen as an 110mm F 2.8 Apo? The ASI will also use only the center field of the image circle, which avoids all image issues that might occur towards the edges of the field.

The next issue is connectivity! how to connect an ASI body to the Nikkor lenses? The Nikon F-mount backfocus is 46,5mm. The setup that works for me is the following:

  • Nikkor lens with F-mount
  • SI Nikon lens adapter. But ONLY the first ring that attaches to the lens. That ring has 11mm optical length and uses M57x0,75mm male thread. Link to TS.
  • TS Optics M57 to T2 adapter Link
  • Filter manual wheel ATIK Optical length 20mm (could be replaced by a motorized ZWO ASI FW)
  • ASI 183mm camera without the T2 F/F/ connector.

The total optical length of this setup is close to 46,5mm and gets me sharp images. The 1 “1/4 filters that are used might still stretch the focus further out.

Further possibilities to explore:

  • autofocus using a belt and a Pegasus FocusCube 2 or a ZWO MotoFocus
  • simultaneously imaging with ASI 300mm H-Alfa on F 2.8 and Esprit/Nikon RGB: given the faster optics of the Nikkor, all H-Alfa and O-III imaging can be done in the same timeframe as the Esprit/Nikon RGB.

Waiting for a clear night!!!!