Since there are currently no commercial adapter solutions available to connect Canon lenses to Atik cameras and people frequently ask how I was able to connect my Atik 16HR to a Canon lens, I decicded to write a small how-to describing how I built an adapter for it and to discuss some of the problems on using Canon lenses for widefield astrophotography.

Use this information at your own risk. Some of the procedures could possibly harm your Canon camera or even damange your lens (especially setting the f-stop of the lens).

In short: don't blame me if anything bad happens, enjoy building your own adapter and send any design suggestions or feedback to  

  Atik 1.25" Adapter (Usually shipped with your Atik Camera)
  Canon Lens Dust Cap E (Rear Lens Cap)
  an about 5mm thick metal ring as placeholder
  tools, glue, etc

While thinking about how to build and design this adapter I soon realized that the easiest way to accomplish this was to re-use a dust cap of one of my lenses. The 1.25" adapter which was shipped with my Atik 16HR and Atik 16IC has the advantace that you can screw a 1.25" filter on it even on both sides. The metal ring functions as a place holder, so you should find one that is about 5mm thick and fits between the lens cap and the 1.25" adapter. Without it I was not able to focus on infinity. 5mm seems to do the job but I guess a few mm more will also work.

First I drilled a hole exactly in the center of the Lens Cap with the right size for the 1.25" adapter to fit through. I used the largest drill bit I could find in my toolbox and painfully extended the hole with a file.

Keep in mind that the adapter afterwards should be in the exact center of the lens-cap!

I used a saw to shorten the 1.25" adapter to about 16mm starting from its socket. Differnt sizes should be okay too because it depends on the size of the metal ring you use and you may have to play a little around to find a good lenght for your lens to reach focus.

Then I just put the metal ring as placeholder onto the 1.25" adapter, put the lens cap on it and used glue to tie everything together.

The beautiful thing about the 1.25" adapter is that you can screw a filter on it from both sides. This has proven to be extremely helpful because there is no room inside the lenscap to use a filter anyway. Besides that, I now have the choice between putting 1.25" filters onto my adapter or use 2" filters in front of the lens.

Before I could connect a lens to it, I had to make sure that I did not damage it, so I had to continue fine-tuning the lenght of the 1.25" adapter with a metal file.

This is how the a Canon 50mm f1.8 lens looks like while beeing connected to my Atik 16 HR ;-)

Most camera lenses need to be slowed down in order to be used for astrophotography. A wide open lens will likely cause distorted star shapes and/or blurred images. Modern lenses use electronics to adjust the diaphragm in the lens to adjust the f-stop. Canon cameras only adjust the f-stop just before taking a picture and revert it to its default (open) position after the shutter closes.

So in my oppinion there are only two ways to overcome this problem: building a manual diaphragm or finding a away to trick the camera to let the diaphragm in its position.

I decided to go with the second quicker but dangerous option:

Trick the camera into letting the f-stop at its position by disconnecting the lens while the camera is powered on and pressing the aperture preview button at the same time.

If you are really sure you want to do this, set the camera to manual mode, set the aperture (f-stop) you wish to use for your astro-images.

Now, press the aperture preview button (red arrow at the bottom) and the lens-disconnect (red arrow at the right) button on your camera at the same time while slowly turning the lens counter-clockwise until the aperture display shows a value of zero.

Now turn off your camera to complete removing the lens.

If everything worked as expected you should be able to see the diaphragm in the lens.