Diagnose 12 of 29 Acquisition mechanics

Unwanted diffraction spikes

Bright stars carry spikes where the telescope should not make them: any spike from a refractor, or extra spikes at an odd angle.

Drawing, not a photo. A refractor's stars, with a spike through each bright star at an odd angle. A refractor makes no spikes of its own.

At 100 %: The brightest stars. Note the angle of each spike and compare it with the spider vanes, if the scope has any.
Causes, most likely first: Dew strap or clip in the light path
A strap edge or a loose clip over the aperture puts a spike on every bright star.
FixCheck that each dew strap and its clip sit clear of the light path.
Session Checklist
Loose wire across the light path
A cable hanging across the front of the scope diffracts light the same way.
FixRoute every wire away from the aperture and tie it down.
Aperture clip
A clip at the edge of the aperture that intrudes into the light path makes its own spike.
FixFind what projects into the aperture, then move or cover it.
Looks like, but isn't: The atlas lists no look-alike for this one.
One frame can't tell you: One frame shows the spikes. Finding what makes them means looking down the front of the scope with a light.
How to confirm the fix: Bright stars with only the spikes the telescope's design makes, and none on a refractor.
Sources: No outside source is cited here. The signature, the causes and their order are the atlas’s own, from imaging experience. The order is a judgment of likelihood; no measured frequency is behind it.

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