Hi,
my setup with Star Adventurer is:
1) image scope: refractor 80 mm / 384mm FL, f/4.8, with Asi 294Mc Pro (pixel scale: 2.48");
2) guiding scope: 30 mm / 120mm FL, f/4, with Asi 120MM-S (pixel scale: 6,44").
With both, SharpCap get a super fast Plate Solving. Of course, if I Polar ALign with the image scope, the process of moving azimuth and altitude is much longer because a very little movement can move too much in the opposite direction, so I have to go back.
While when Polar ALign with the guiding scope, everything is smooth, super easy and fast.
Anyway, with both the scopes, I can get the 'excellent' in short time. I'm super happy of this feature.
So my question is: how much more accurate is the PA at the longer focal lenght? The extra time it pays off, or it's the same?
Any advice would be appreciated.
Thanks.
Polar Alignment scope
Re: Polar Alignment scope
Just a bit OT here but...
Any PA error introduces field rotation of consecutive images. When you view consecutive images you'll see the image rotate around the center. The rate of rotation is totally independent of the focal length. The amount of rotation depends on where in the sky the camera is aimed and the duration of the exposure -- but not the focal length (or f-ratio or ISO/gain).
The only symptom of PA error is field rotation. However, there's a shockingly broad tendency for people to assign PA error is the source of every other problem that shows up in images. Man-centuries have been spent trying to eliminate polar alignment error as a cure for whatever anomaly shows up in a subframe. That's the equivalent of changing your car's oil because a tire is flat.
The most common misattribution is blaming obvious PE on PA error. As mentioned, PA error shows up (if at all) as concentric arcs around the center of the image (with lengths proportional to the distance from center). PE error usually shows up as equal-length parallel lines/arcs.
Any PA error introduces field rotation of consecutive images. When you view consecutive images you'll see the image rotate around the center. The rate of rotation is totally independent of the focal length. The amount of rotation depends on where in the sky the camera is aimed and the duration of the exposure -- but not the focal length (or f-ratio or ISO/gain).
The only symptom of PA error is field rotation. However, there's a shockingly broad tendency for people to assign PA error is the source of every other problem that shows up in images. Man-centuries have been spent trying to eliminate polar alignment error as a cure for whatever anomaly shows up in a subframe. That's the equivalent of changing your car's oil because a tire is flat.
The most common misattribution is blaming obvious PE on PA error. As mentioned, PA error shows up (if at all) as concentric arcs around the center of the image (with lengths proportional to the distance from center). PE error usually shows up as equal-length parallel lines/arcs.