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This straightens me out on the formula and how it works. Pretty neat. Also, thanks for the chart. It will be handy in my set-up.
Boy, all I can say is that this astronomy stuff is complicated, and people have done the math to analyze it.
From: Jerry Hubbell - Explore Scientific VP Engineering <jrh@...>
Sent: Thu, Jan 14, 2021 1:59 pm
Subject: Re: [ESPMC-Eight] 3-4" RA wiggling while PHD2 guiding with EXOS2-GT PMC-eight #EXOS2 #astrophotography
There are 206265 arc-seconds per radian so the formula is the conversion between an angular value to a linear scale at the image plane. The value is 206.3 (rounded 206.265) because of the FL being in mm and the pixel size being in um (microns) a 1000:1 ratio.
I hope that makes sense.
Vice President of Engineering
Explore Scientific, LLC.
jrh at explorescientific.com
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Author: Scientific Astrophotography: How Amateurs Can Generate and Use Professional Imaging Data
Remote Observatories for Amateur Astronomers: Using High-Powered Telescopes From Home
Mark Slade Remote Observatory (MSRO) IAU MPC W54 Equipment
Mounts: ES PMC-Eight G11 + Telescope Drive Master (TDM)
Scopes: ES 165 FPL-53 ED APO CF, ES 102 FCD100 ED APO CF
Cameras: QHY174M-GPS + FW, QHY163C
Misc: 3-inch 0.7x Focal Reducer Field Flattener, Filters: Luminance,
Red, V-band Photometric, Diffuser, 200 lpmm Spectral Grating
Software: MaxIm DL 6, Cartes du Ciel, Astrometrica, AstroImageJ, AutoStakkert!
HomeBru 6 inch Reflector f 6.6
HomeBru 85 mm Refractor f 5.6
PMC-8, EXOS 2
Long retired EE.