I have a couple of questions relating to achieving precise (well precise enough for 60-90 second exposures with my AT72) polar alignment with my EXOS-2GT mount. I have been doing astrophotography with my Canon T2i for about a year just fine (mostly with my 85mm and 135mm lenses). Just recently I bought a 200mm lens and also started using an AT72. But, my alignment skills don't seem to be up to the job with the longer lenses with exposures past 30 seconds. After checking my polar scope alignment with my mount and making some small adjustments, I was still getting small star trails at my test exposures of 60 seconds of maybe 4 or 5 star diameters.
Unfortunately, unlike the Celestron Nexstar +, the EXOS hand controller has no polar alignment function so I am limited to using the polar scope for alignment. So, I have a couple questions that I hope you forum members can help me with.
My EXOS-2GT reticule looks exactly like the one at the bottom of this post which I found in a Vixen manual.
First question: As you can see, the reticule pattern on the EXOS polar scope is ancient. With Polaris being at about 89d21m I first tried placing it at the intersection of the 40' mark. This shortened the trail a little, but they were still about 3 star diameters in 60 second exposures. Even though this picture is from a Vixen manual, a couple days ago I decided to try and estimate what the offset illustrated would be for 2019 and applied it for some 60 second test images. I have seen a slight improvement, down to maybe 2 star diameters, after applying the offset, so I am unsure if I should apply the offset or not, or try to tweek the positioning to find the exact right position. Any thoughts?
Second question: The other problem with using this reticule is that there is no precise way to align the reticle pattern with the position of Polaris as shown in PolarFinder or PolarScope, so I am wondering if I might be able to use a different polar scope with the mount that may have a "better" reticule pattern, say like the Takashai pattern, that would allow for more precise alignment.
Thanks in advance for any help.
Edited by jstrandberg, 21 March 2019 - 10:42 AM.