Your first session will go wrong somewhere. That's normal — every imager's first M31 has egg stars or a gradient like a sunrise. The goal of night one isn't a portfolio image; it's to run the whole pipeline once, end to end, so night two has fewer unknowns. This checklist is the order of operations that experienced imagers run on autopilot.
Do the daylight work in daylight. Balance the mount in both axes with everything attached — camera, guide scope, dew straps, every cable. Route cables so nothing dangles (a swinging USB cable is the most common cause of mysterious guiding spikes). Rough-focus on a distant treetop so you're near focus before dark. Update your capture software while you still have patience.
- Balance slightly east-heavy on a German equatorial — the gears stay loaded on one flank and guiding is calmer.
- Bring a red headlamp AND set your phone to red-shift. One glance at a white screen costs you twenty minutes of dark adaptation.
At dusk: align, focus, calibrate — in that order
Polar-align first, before anything else depends on the pole. Modern tools (SharpCap's routine, N.I.N.A.'s Three Point Polar Alignment, the polar scope if you must) get you to a couple of arcminutes in ten minutes. You do not need perfection: under 5′ of error is fine for guided imaging at short focal lengths.
Then focus, properly. A Bahtinov mask makes it foolproof: center a bright star, adjust until the middle diffraction spike sits dead-center, remove the mask. If your software reports HFR, watch the number instead — lower is better, and the minimum is sharper than your eye's judgment through a screen.
Then calibrate guiding on a star near the celestial equator and meridian (where motion per correction is largest). Let PHD2 run its calibration; don't skip its Guiding Assistant on your first night — its backlash and polar-alignment measurements are a free health report on your mount.
- Focusing before the optics cool. A telescope that came from a warm house shifts focus for 30–60 minutes. Focus at dusk, then RE-check an hour in.
- Calibrating guiding while pointed at the pole — calibration needs apparent motion; near Polaris there is almost none.
The capture block
Pick one bright, forgiving target that is rising, not setting — you want hours of runway, and rising targets climb away from the horizon murk. Set your gain to the camera's documented sweet spot (unity gain or the HCG switch point; the manufacturer's chart tells you), pick a defensible sub length (see the sub-exposure article — 60–120 s guided broadband is a safe first-night answer), and enable dithering every 1–3 frames. Dithering costs a few seconds and saves your stack from walking noise — it is not optional.
Then the hard part: leave it alone. Resist re-framing at 1 a.m. because the composition could be 5% better. A hundred subs of one framing beats fifty subs of two framings every time, because integration is the only currency that buys signal-to-noise.
Do it in AstryxTonight's Picks ranks targets that fit your field of view, clear your horizon, and dodge the moon — with a one-click 6-hour project so the plan survives past midnight.Before you touch ANYTHING: flats
When the sequence ends — before you rotate the camera, refocus, or even think about packing up — shoot your flat frames. Flats are photographs of your optical train's fingerprint (dust motes, vignetting), and that fingerprint changes the moment anything moves. A flat panel, a white T-shirt over the objective at dawn sky, or a tablet screen all work: aim for a histogram peak near half of full scale, and take 20–30.
Darks and bias can wait for a cloudy night — they don't depend on the optical train, only on the camera at a given gain, temperature and exposure. Build that library once and refresh it every few months.
- Packing up first and shooting flats 'next weekend'. The dust will have moved. Every hour of last night's data is now harder to calibrate.