Every one of these happened on a real night. What it looked like, why it happened, and what fixed it.
What happened. The settings screen showed Duo-Band. Every saved frame said Astro, and the sky colour in them was the full spectrum, not the hydrogen and oxygen glow.
Why. The screen and the filter wheel do not always agree.
The fix. Look at the filter by eye before you press shoot. Another run of M31 went the other way and was shot on Duo-Band by mistake.
What happened. With the cloud due back in an hour, the run was set for over four hours.
Why. Auto Parameters sets the count to 999 by default. At 15 seconds that is 4 hours 10 minutes.
The fix. Set the count to finish before the cloud or the Moon arrives, and let it end by itself. Every frame is saved as it goes, so stopping early loses nothing.
What happened. The Heart Nebula ran for 4 hours in Alt-Az mode. The finished stack was cropped to about two thirds of the frame.
Why. In Alt-Az the picture turns through the night. Here it turned 75 degrees, and only the sky every frame covered survives.
The fix. Set up EQ mode first, then pick the target. See Improver.
What happened. In EQ mode the Dwarf stopped with "something obstructing" or "cloudy, redo". The sky was clear and the target 67 to 76 degrees up.
Why. It is the Dwarf's EQ limit: two runs stopped at exactly an hour and a half before the target was due south.
The fix. Start the target within an hour and a half of due south, or after it has passed. See Expert.
What happened. After the target crossed due south, the stacker threw away every later frame: 370 of them.
Why. In EQ mode the Dwarf flips at due south, so later frames are turned about 180 degrees. The stacker only looked for small turns.
The fix. Use a stacker that checks the full circle, or stack the two halves separately and join them.
What happened. On one target at 60 seconds, many frames were rejected and the stars in the rest were smeared.
Why. They all smeared the same way across the whole frame, which is tracking, not the lens.
The fix. Do not give up 60 seconds over one target: others the same night were fine. Check the level and the polar alignment, and use 15 seconds on that one if it keeps happening.
What happened. Darks taken at the start of the night did not clean up frames taken hours later.
Why. Darks only work when exposure, gain and sensor temperature all match, and the sensor cools through the night. The Dwarf's own darks only clean the picture on its screen, not the saved files.
The fix. Take ten darks at the end of the night, at the same exposure and gain.
What happened. Frames taken before full dark were added to a stack, and the picture got noisier.
Why. The 36 twilight frames added 4 percent more light and 73 percent more noise.
The fix. Start at full dark. Tonight's plan gives the time.
What happened. Pointed at a folder of hundreds of frames, AutoStakkert loaded one or two, or stacked the small thumbnails.
Why. It wants a numbered sequence, and the Dwarf names its files by time.
The fix. Copy the frames into a fresh folder with numbered names. It changes nothing in the originals.
What happened. After a few long nights there was no room left for the next run.
Why. Every saved frame is about 16.6 MB, and there is no memory card. About 110 GB is free, which is about four long winter nights.
The fix. Copy each night to a PC and an external drive, check the copy, then delete from the Dwarf. Never let the computer format it. The steps.
What happened. Nights in the garden kept failing on faint targets.
Why. Neighbours' security lights kept coming on.
The fix. Save faint targets for a dark site, and keep the garden for the Moon, clusters and Duo-Band nebulae.
What happened. The finished picture showed less nebula than the Dwarf's own live stack had.
Why. The processing fitted its idea of the background right through the faint nebula, and took the nebula away with it.
The fix. Take away only a flat level and a slight tilt for the background. When it looked better on the scope, it is a processing fault, not your eyes.
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