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field_rotation [2024/12/19 09:52] – tailspinfield_rotation [2025/02/23 16:55] (current) – tailspin
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 Note that field rotation is most pronounced when an object is near your meridian((An imaginary line you are on that extends from the North Pole to the South Pole)), as the object's altitude changes rapidly, leading to longer streaks. And it’s gets worse the closer you live to the equator. ((There's an [[https://kelly.flanagan.io/astronomy/astrophotography/field-rotation-and-alt-azimuth-mounted-telescopes/|excellent post]] by Kelly Flanagan the spells out the details with some excellent illustrations.)) Note that field rotation is most pronounced when an object is near your meridian((An imaginary line you are on that extends from the North Pole to the South Pole)), as the object's altitude changes rapidly, leading to longer streaks. And it’s gets worse the closer you live to the equator. ((There's an [[https://kelly.flanagan.io/astronomy/astrophotography/field-rotation-and-alt-azimuth-mounted-telescopes/|excellent post]] by Kelly Flanagan the spells out the details with some excellent illustrations.))
  
-To minimize field rotation you can use a couple of strategies. Short exposure times helps, but the best solution is to limit your data collection ((Astrophotography uses a telescope as a funnel to direct light into a camera sensor that detects photons, converts their intensity into a number, which is stored as data for later processing)) to times when your target isn’t close to the meridian.+To minimize field rotation you can use a couple of strategies. Short exposure times helps, but the best solution is to limit your data collection ((Astrophotography uses a telescope as a funnel to direct light into a camera sensor that detects photons, and converts their intensity into a number, which is stored as data for later processing)) to times when your target isn’t close to the meridian.
    
-Visibility plots can help you predict how an object's path changes throughout the night, offering a slick way to estimate field rotation. By drawing imaginary tangent lines on the visibility curve, you see how much field rotation will occur. The tangent line for a  target at 2000 (8PM) and 0000 (midnight) basically overlap, so there will be very little problem.+Visibility plots can help you predict how an object's path changes throughout the night, offering a slick way to estimate field rotation. By drawing imaginary tangent lines on the visibility curve, you see how much field rotation will occur. The tangent line for a target at 2000 (8PM) and 0000 (midnight) basically overlap, so there will be very little problem.
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 {{ :screenshot_2024-05-31_at_10.03.25 am.png?nolink&400|}}As a rule of thumb try to capture targets that are close to east (90º) and west (270º), not north (0º) or south (180º), above 30º from the horizon and below 80º.  Obviously, that’s not a firm rule. In other words, YMMV. {{ :screenshot_2024-05-31_at_10.03.25 am.png?nolink&400|}}As a rule of thumb try to capture targets that are close to east (90º) and west (270º), not north (0º) or south (180º), above 30º from the horizon and below 80º.  Obviously, that’s not a firm rule. In other words, YMMV.
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 +{{:480232120_9395784527127098_7672157940864184496_n.jpg?nolink&350 |}}An excellent web tool that lets you calculate the safe exposure times //for your latitude// is at [[https://apximhd.github.io/field-rotation/field_rotation.html]]. 
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 By the way, many post-processing software packages can help correct field rotation, but it's not always a perfect solution. Just sayin’. By the way, many post-processing software packages can help correct field rotation, but it's not always a perfect solution. Just sayin’.
field_rotation.txt · Last modified: 2025/02/23 16:55 by tailspin

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