Widefield rig for QSI

[JohnC64]

Well back in 2014, I said that I wanted to put together a wide-field rig for my QSI 683WSG and I have eventually managed to get started on it. :-)

The WSG variant of the QSI 683 has an inbuilt back focus such that canon lenses just don't quite work. (They fit OK on the WS variant with an adapter)  To get over this problem I have used a Pentax 6x7 medium  format lens that has an back focus register of  84.9mm.  QSI used to do a 6x7 lens adapter for the camera but it was about £225!!! but have since stopped making them.

I have taken a Canon - 6x7 Lens adapter, bought on eBay 3 years ago, and machined off the canon adapter at the back to give the correct back focus distance.  Then drilled 4x 3.2mm holes straight through the back of the adapter into the central lens area.  From the other side , I then drilled 5.6mm holes back until about 3mm from the camera end to give a shoulder for the screws used to fix it to the camera.  I also needed to cut a step off the top of the adapter so that it didn't foul on the guiding head.

This then made it look like the QSI adapter.  To attach the adapter, I removed the T Mount-attachmenton the camera and then fitted my custom adapter in its place.  To mount it all together and to give some support, I bought a Gemstone Lens support and Attached it to a Mini Dovetail bar.
 

Original QSI Adapter: https://www.optcorp.com/qs-ad5-p67-wsg-pentax-6x7-lens-adapter.html
Gemtune Lens Support: https://www.amazon.co.uk/dp/B00VE0KH2Q/ref=pe_385721_51767431_TE_dp_1

Now it is assembled, I still need to check the measurements to ensure that the register distance is spot on and to do a test run (Awaiting a clear(ish) night).  I will probably fit a velcro strap to just secure the lens in place and need to get a Teleskop-express micro-focuser large enough for the 6x7 Lens

But for now here are some pictures of it all together

Cheers John

 

 

 

 

 

[happy-kat]

That lens support adaptor looks clever. Roll on a clear night so you can test.