Geoptik Canon CCD Adapter

I have done astrophotography with a modified Olympus E-PL5 for quite a while now. With the acquisition of the mono cooled ZWO ASI178MM-cool camera, it has opened up huge possibilities for me. One of the methods of imaging that I have been looking to get into, is with narrowband imaging, i.e. using 12nm narrow bandwidth filters to image in H-alpha, S-II and O-III. But this would require a fast imaging system. I had bought the Samyang 135mm F2.0 lens for this, and finally the missing piece of the puzzle has arrived – the Geoptik Canon CCD adapter.

I managed to buy this used on Astrobuysell for a very good price (saving over 1/3), and it came with the Finder scope adapter included which would allow me to use a guider for longer exposures.

Geoptik Canon CCD adapter with finder adapter (fitted the wrong way)
Geoptik Canon CCD adapter with finder adapter (it came fitted the wrong way)

I had to buy a finder shoe to fit this, as that is not included. I bought the Skywatcher finder shoe as that will fit onto the finder adapter, albeit via only one screw. But it does feel secure as one edge of the finder shoe base is pressed tight against the Geoptik finder adapter.

Skywatcher Finder shoe
Skywatcher Finder shoe
Fitted with finder shoe
Fitted with finder shoe

Now the orange ring in front is used to tighten and secure the lens onto the mount. The reasons I chose the Canon version were  because Nikon F-mount lenses can be adapted to fit on this using an F-mount to EOS adapter (but not the other way around), and the Canon version of the Samyang 135mm F2.0 lens was much cheaper than the Nikon F-mount version.

This adapter is 19mm thick, and my ZWO ASI178MM-cooled has a backfocus distance of 17.5mm. Canon EOS lenses have a flange focal distance of 44mm, which means that this leaves me 44-19-17.5mm = 7.5mm of extension to play with. There is enough space for me to use the TS T2 360 degree rotation and quick changer adapter, to make filter changes a lot easier (measures 5.5mm).

The current version of this adapter allows for the mounting of filters which are 1.25″ (fit in the back of the adapter just before the camera) and 2″ (fit in the front of the adapter just behind the lens) in size. The adapter I bought, however, is the older model and only takes 1.25″ filters, which is fine by me as using 2″ filters would require removing the lens to change filters – not as easy as my adapted way for changing 1.25″ filters.

Mounted on iOPtron ZEQ25 with guide scope
Mounted on iOPtron ZEQ25 with guide scope

I have adapted this setup to mount onto the iOptron ZEQ25, using a long Celestron Losmandy plate to make adjusting balance easier.

Setup fully balanced in RA and DEC
Setup fully balanced in RA and DEC

Here I show where the 1.25″ filter fits – just before the camera. I have used the TS T2 360 degree rotation and quick change adapter here, mounting one half of this adapter onto the Geoptik camera end, and the other half of this adapter to the camera’s T2 mount.

Takes 1.25" filters - Astronomik 12nm H-alpha filter used here
Takes 1.25″ filters – Astronomik 12nm H-alpha filter used here
Quick decoupling and rotating T2 adapter (5.5mm thick)
TS T2 360 degree rotation  and quick changer adapter mounted on the camera to facilitate easy change of filters (5.5mm thick)

The pieces then fit together and secured via the two long screws; these two screws can also be used as reference to realign the camera after each filter change.

Camera mounted back onto the Geoptik Canon CCD adapter
Camera mounted back onto the Geoptik Canon CCD adapter

Now the final piece of the jigsaw has arrived, all I have to do is wait for clear skies and then I can start imaging in narrowband @ F2. How exciting.

Boon