Diagnose 11 of 29 Acquisition quality
Halos around bright stars
Bright stars have a ring or a soft glow around them, larger than the star itself. Faint stars look normal.
- At 100 %
The brightest star in the frame. A bright ring or disk sits around it, and it is there from the first sub of the night.
- Causes, most likely first
Filter reflection
Light from a bright star bounces between the filter and another surface and lands out of focus around the star. A halo that shows with one filter and not the others points at that filter.
FixCompare the same star through a different filter. If the halo goes, a filter with better coatings is the fix.
Uncoated surface
An uncoated glass surface in the light path reflects far more than a coated one, and the reflection comes back as a halo.
FixFind the uncoated glass in the train and replace it with a coated part.
Sensor-window reflection
Light reflects off the sensor and back from the glass window in front of it.
FixIf the halo stays with every filter and every other surface is ruled out, ask the camera's maker about its window.
- Looks like, but isn't
A sharpening halo is a dark ring that appears after processing. An optical halo is bright and is in the raw sub.
Dew halos grow through the session. A reflection halo is the same size from the first sub.
- One frame can't tell you
One frame shows the halo. Which surface makes it needs the same star shot through different filters.
- How to confirm the fix
The same bright star with no ring, in a raw sub, through each filter.
- 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.
In the symptom picker
- Bright stars have a ring or a glow around themweight 3
- The same in every frame, including the first of the nightweight 1
Last updated All 29 failure modes, and the symptom picker