Observational Mishaps - All Compiled Images

List of all images in the database:

seeing, focusing, guiding, astigmatism, ...

fringing: small scale, wave-like structure across whole image.

dust rings: dark, doughnut features of various sizes.

cosmic rays: very small, bright streaks or points of light in images.

reflections: bright streaks of light in images. Can have different shapes.

diffraction spikes: spikes in a radial direction around bright stellar images

guider jumping: stars appear as double images.

earthquakes: stars appear with trails due to motion of telescope from earthquakes.

occulting dome: a distorted stellar image plus a bright partial doughnut-like feature around the star.

occulting dropout: occultation by dropout caused illumination of image to differ from flats and from previous images.

deflated airbags - loss of support of primary mirror: stars appear very non-circular, but rather triangular in shape (due to the 3 hard support points of the primary mirror).

readout error: saturated strips across image.

CCD zero-level ramping: zero-level (bias) varies across image.

CCD bias frame banding due to electronic interference in the system: dark or bright bands along rows or columns on CCD.

shutter failure: bright stars have trails in the direction of the readout of the CCD.

significant dark current: image has a background structure which cannot be corrected for with the bias or flats.

meteors, asteroids, satellites, etc.: thin trails across image.

vignetting by the guider probe or the finder camera: lightpath blocked in portions of the image, i.e., mostly round, light-deficient feature in some part of the image.

condensation on the dewar window: bright filamentary structure or dark doughnuts towards the center of the image.

frost/ice on the dewar window (inside or outside): filamentary stucture similar to water condensation symptoms, or dark "fingers" on the outside of the field; dust doughnuts can appear especially dark. For some cameras (particularly electronically cooled ones), a bright ring can be seen which increases in radius as the condensation evaporates (if frost is on the inside of the camera window).

dead lady bug on the filter: dark, circular region in some part of the image which tends to move around due to motion of the telescope, the filter wheel, etc.

ghost images of bright objects in the image: strangely shaped (ghost) images of stars in the field due to internal reflection; frequently encountered with Schmidt telescopes.

image with a number of problems: clearly visible in the image are astigmatism, reflection features, vignetting of the filter, and a significant dark current.

"squiggle": satellite trail with wavy pattern perpendicular to the direction of motion.

mysteriously persistent reflection streak: reflection-like feature which did not go away when telescope was moved.

focus frame taken during twilight: thin, bright, vertical streaks across image; stellar images only visible in a thin strip on one side of the field.

airplane in the field of view: broad, bright, tire track-like features in the field of view.

"intergalactic battle": infrared, stellar image with bright loop features all around it.

smoky chip: smoke-like, bright feature on the image.

image melting: the stars in one part of the image appear to melt, i.e., have elongated and streaky appearance; feature of the new chip 1 of the BTC.

light leak in setup: brightness gradient across the field of view caused by external light source.

light leak in filter wheel: large scale, bright scattered light features all over the image.

misalignment of filter wheel: light deficient, large scale features (plus bright ones in processed images) in the outer parts of the field of view due to vignetting by the filter wheel.

internal reflections: multiple, well-defined, offset rings (doughnuts) around bright stars.

IR problems: infrared image with multiple problems: circle shaped ghost images of bright star (small and large size), wavy interference patterns, stripe across image, and dark blotches.

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