Originally posted by dcshooter Beware that with the O-GPS1, extreme wide angle lenses will still exhibit trailing around the images, since the sensor can only move in a flat plane, rather than sidereally.
Yes, good point. With planar (sensor) shift tracking there are two side effects that are pronounced with extreme wide angle lenses with long exposures. Planar tracking cannot fully track both the celestial equator and poles simultaneously. This is inherent to the system. A second weakness becomes apparent with lenses that have a lot of distortion. It is geometrically impossible for the sensor shift to accommodate for lens distortion across the entire field in a single exposure. Blurs/trails result as the sensor moves through zones of greater and lesser distortion.
For these reasons, you'll get the very best Astrotracer results with flat field lenses that don't have extreme wide FOV.
Here are tracking devices in order of convenience and results:
1- O-GPS1 Astrotracer: The ultimate in convenience. Super small and easy, but with the weaknesses mentioned above.
2- Mini-barndoor trackers and Micro-mounts such as the Vixen Polarie: Still small, pretty convenient. Require you to align them accurately. Most have limited payload.
3- Alt-Az computerized mounts. Larger, pretty convenient and moderate time to set up. Bigger payload. Good precision. You'll have field rotation with these unless you have a model capable of working in a wedge configuration.
4- Computerized German equatorial mounts. Not convenient. Highest accuracy and payload. Most set up time for best accuracy.
I own and use all of these. It's all about budget and effort. Will I be taking a big mount on my upcoming road trip to Las Vegas? No way! I'm totally throwing the O-GPS1 in the bag. Will I be taking the O-GPS1 for my next serious astro-imaging session? Nope!
Hope this helps.