Since the first light of my Celestron C9.25 telescope, it became apparent that I would have to take the plunge and learn how to guide using an Off Axis Guider (OAG). I also do most of my imagine in Narrowband so I needed an OAG so that I could guide in front of my filters. My mentor, Michael Caligiuri, told me that learning how to guide with an Off Axis Guider was a must with a larger focal length telescope but would not be easy so I set out on a quest to learn how to use this critical piece of equipment.
Step 1: Sourcing an OAG
There are many OAG’s out on the market and depending on your needs, there are a few that would be right for you. Selecting the right OAG depends on how much distance your focal train can take. With the OAG 5, the light path was 36mm, which is a fair amount of distance to take up in a focal train but I did some research and found that this OAG was used quite a bit with my camera combination (the SBIG ST-10XME). Knowing which OAG I needed, I starting searching Astromart daily to see if anyone was getting rid of theirs and it did not take too long before I found one at a killer price.
Step 2: Putting the pieces together
Admittedly, this step took much longer than I anticipated. Since the CCD and the OAG are connected to the same light path, the most important aspect to figure out is that the imaging chip and the guider chip need to be the same distance from the pick off mirror that sits inside the OAG...Read More >