Glossary

Calibration Frames

updated: 2025-03-10

Calibration Frames are required to reduce effects resulting from your optical equipment (like vignetting), electronic noise like read out noise or pixel errors.


Depending on the equipment or SW used there are different ways how calibration frames can be obtained.


So called Master Calibration Frames are stacked images of a number of single calibration frames. 


Characteristics of master calibration frames:



Calibration frames are required during the Calibration Process as shown below:


Master Frame Organization

Organize your master frame folders e.g. like:


  • On a USB Drive or CF-Card
    • Master
      • Config A, B, C
        • Bias
          • by Gain and temperature
        • Dark
          • by Gain, exposure time, filter and temperature
        • Flat
          • by Gain and Filter A, B, C


If you are using PixInsight for image calibration and integration, then please use the master file naming convention described in this article:


How WBPP retrieves the information of files in the session | PixInsight Forum

 

Calibration File Naming Convention in this project:

New since ASI2600MC AIR:

{IMAGETYPE}_Stack{COUNT} _{EXPOSURE}_{BINNING}_{CAMERA}_gain{GAIN}_FILTER{Filter}_{Config}_{Date}_{Temperature}


Old:

{ImageType}_Binning_Count_Filter_Exposure_Config_CamTemperature_Date

Sections are separated by a underscore sign "_"


  • IMAGETYPE (recognized by PI): must be one of: {Masterbias | Masterdark | Masterflat | Masterlight}
  • COUNT (not recognized  by PI): number of used subframes, e.g. COUNT-20, COUNT-100
  • EXPOSURE (recognized  by PI): exposure time in seconds, e.g. EXPOSURE-0.001 or EXPOSURE-200 
  • BINNING (recognized  by PI):  one of {BIN1 | BIN2 | BIN3 | BIN4}
  • CAMERA: automatically set by AI camera, e.g. 6200MM
  • GAIN (recognized by PI): e.g. gain100
  • FILTER (recognized  by PI): examples: FILTER-NoFilter, FILTER-OLeN, FILTER-UHC2. Must be set manually if no filter wheel is used.
  • CONFIG (not recognized  by PI): optical configuration used, e.g. TS600ASI194, TS1624ASI294 etc. Must be set manually.
  • DATE (not recognized  by PI): a date string like 20231116
  • TEMP (not recognized  by PI): camera temperature during subframe capture, e.g. TEMP-10, TEMP20



Master file name example:


New File Naming example since ASI2600MC AIR:

MasterFlat_Stack20_50.0ms_Bin1_2600MC_filter-NoFilter_gain100_20250221_1.6C.xisf


Old:

masterflat_BIN-1_COUNT-20_FILTER-OleN_EXPOSURE-0.001_CONFIG-TS600AS294_TEMP-10_20231111


 The master file names must at least contain the word "master" in order to be accepted by PixInsight.


IMPORTANT: Flat Frames should also contain the correct filter name in the in the filename. Because color light frames from an ASIAIR OSC camera never contain any filter information, even if a filter has been used. The Master Flat Frames must therefore be renamed and the string _filter-NoFilter must be added somewhere in the filename. They also need to be converted from a .fit to a .xisf file in order to be accepted by the WBPP or FBPP batch pre-processing scripts in PixInsight.

Dark Frames

Bias Frames

Flat Frames

Environment

Cover your camera: your camera or scope must be covered to block all light off the sensor

Cover your camera: your camera or scope must be covered to block all light off the sensor

Use a evenly-lit light source, e.g. twilight sky, laptop screen, light panel, light box, TV screen, a white T-shirt to cover your telescope  or similar.

Re-Usability

yes

yes

Should be taken during every imaging session because they depend on the alignment of the entire imaging train

Gain or ISO

same as light frames

same as light frames

same as light frames

No. of exposures

minimum of 20 frames

50 to 100 frames

same no. as light frames

Exposure time

same as light frames

as short as possible (e.g. 0.001s for CMOS cameras)

optimal exposure time, no over or under exposure (different form light frames)

Capturing Calibration frames


Hint: Master calibration frames can be automatically captured and stacked with the Preview function of  ASiair, see Live Stacking for more detail.

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