Astrophotography – The Tracking Telescope Mount

This is the second part of the series on Astrophotography.

In my earlier introduction article, I briefly outlined the baseline equipment required for doing Deep Sky Object, (DSO), imaging.   In the next few articles, I am going to cover specific technologies in more detail with the idea that there are challenges and benefits to mastering each one of these tightly integrated components of hardware and software that make it possible for a motivated person to image distant galaxies, nebulas, and other spectacular DSO.  It took me considerable time to gain all the knowledge and skills and it is hard to condense even a single topic in one overarching document, so again this segment is more of a primer and will cover the basics of a tracking telescope mount.

The mount is the bedrock of your imaging sessions.  I tend to encourage anyone interested to make a significant investment in this one critical component.  In my case, I was thinking more of the budget and all the items I needed.  I was definitely underestimating the mounts role. But, before I could go cheap, my wife knew I was looking at the Orion Atlas as my top end spend, (I was considering the lesser Orion Sirius), so she bought one for Christmas 6 years ago as a surprise.  It sat in its box for a year before I got going while I did more research as I still had no idea what I was doing.  It has turned out to be more than adequate, even though I installed some modifications. More on that later in the article.

For now, a few key definitions to help with following this section:

It would be nice if you could see the CNP from your polar scope view, but you cannot.  However, Polaris which is a few degrees from CNP and orbits around it from a telescope perspective.  Therefore, in polar alignment, you are actually aligning your mount using the offset position of CNP from Polaris.  The examples below visualize this situation.

Celestial North Pole and Polaris relationship as seen in the free program Stellarium:

Polaris and Celestial North Pole
Click for an enlargement