Originally posted by Weevil Thnks, that's clear explanation...
just curious, did you get that comet NEOWISE pic from a single long exposure shot ? is so, you must have been in a pretty dark sky isn't ?
Single 80 seconds shot. I was ~15 miles (24km) or so away from the populated area. So it was much darker than e.g. my backyard, yes.
Originally posted by cuiv So now I'm thinking this won't work as well as standard Astrotracer for multiple exposures, because then you need to also track the object.
You're correct in that you need calibration each time you adjust the tripod. However, you don't have to think about calibration because it's automatic, pain free and accurate. Calibration of GPS-based one is none of these.
Type I/II (GPS-based) work flow: Manually calibrate compass by contorting your body and hands/arms in a funny way, which may or may not work perfectly (see below). Set up the tripod and the camera. Press shutter button to take multiple shots. Reposition your camera. Press shutter button to take another series. Reposition. Rinse, repeat.
Type III (GPS-less) work flow: Set up the tripod and the camera. Press shutter button to take multiple shots. Reposition your camera. Press shutter button to take another series. Reposition. Rinse, repeat.
In addition, tracking performance of Type III is actually better than Type I/II in my very limited experience (I've only tried Type III in 3 very short evenings, all on weekdays, mostly with 300mm focal length).
For one thing, you don't have to worry about iron, steel, permanent magnets and DC current around the camera for Type III. OTOH, to get the most out of Type I/II, I have to pay attention to everything nearby, like if quick release clamp has too much iron/steel, what about tripod, am I too close to building and/or fence and/or car and/or motor-driven equatorial mount for another camera and/or whatever, if there might be rebars and remesh underground, that kind of stuff. I'm not joking, these things do make a difference.
Maybe related to the above, but Type III is more accurate than Type I/II. No trailing whatsoever for 60 sec exposure with a 300mm lens pointing at Orion (which is close-ish to the celestial equator where the stars move the fastest), the slightest hint of trailing for 90 sec if you pixel peep. Maybe it's just me but I haven't achieved that with GPS-based one.
Anyway that's my observation so far.
Last edited by kwb; 12-19-2021 at 10:13 PM.