English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

The photon transfer curve (PTC, variance vs. signal level) is a commonly usedand effective tool in characterizing CCD performance. It is theoreticallylinear in the range where photon shot noise dominates, and its slope isutilized to derive the gain of the CCD. However, recent researches on differentCCDs have revealed that the variance progressively drops at high signal levels,while the linearity shown by signal versus exposure time is still excellent andunaffected. On the other hand, bright stars are found to exhibit fatter pointspread function (PSF). Both nonlinear PTC and the brighter-fatter effect areregarded as the result of spreading of charges between pixels, an interactionprogress increasing with signal level. In this work we investigate thenonlinear PTC based on the images with a STA1600FT CCD camera, whose PTC startsto become nonlinear at about 1/3 full well. To explain the phenomenon, wepresent a model to characterize the charge-sharing PSF. This signal-dependentPSF can be derived from flat-field frames, and allow us to quantify the effectson photometry and measured shape of stars. This effect is essentially criticalfor projects requiring accurate photometry and shape parameters.

The nonlinear photon transfer curve of CCDs and its effects on photometry