Flats Calibration Wizard
Description: The Flats Calibration Wizard is used to automatically find the exposure time needed when taking flats. In general this wizard only needs to be ran once for each equipment configuration. Once the Flats Calibration Wizard is complete the exposure lengths are stored in the "Flats" section of the Filter Setup.
Running The Flats Calibration Wizard:
Before you run the Flats Calibration Wizard you should ensure that:
- Your Flat Box or flat source is setup and ready to use
- Your camera is connected
- If needed your filter wheel is connected.
- If using a Flat Box with controllable brightness you have setup the brightness values to be used for the filters using the Filter Setup dialog.
Once the above are ready you can begin the wizard by selecting the profile that you would like to run calibration for by clicking the Choose button. The following dialog will appear:
If you select "Current Sequence" the equipment and data from the current sequence will be use. However if you fail to save the sequence or you do not save the sequence as a profile then all the flats data will be lost. The preferred method is to run the Flats Calibration Wizard against a profile so that the profile gets updated with the flat exposure information.
Select the Profile you would like to use and click "OK".
After choosing an Equipment Profile (or the current sequence), the Wizard will show the equipment required for the calibration run. Required equipment will always include a camera, but may also contain a filter wheel and flats box. All three will always be displayed and if your profile does not need a connection to certain gear, it will show as a checkmark (implying not required). Upon choosing the profile, the Wizard will attemp to acquire connections to the required gear. If it fails, it will show an error message. Correct the issue and then click the "Refresh" button below the number "1" to retry the connections.
Understanding How Flat Box Brightness is Set
If your flat box does not have variable brightness controls, you can skip this section. If it does, there are a couple concepts to understand about how the Flats Calibration Wizard will set brightness during calibration. Specifically, you can opt to use the default brightness values for the current filter or you can choose to override those values with a manual brightness setting.
- Default Brightness Values: Ensure that the checkbox to Override filter brightness values with the manual value is not checked. This behavior will use the brightness values that you currently have stored with the filter. See here for more information on setting default brightness values for a filter. If a request binning or ISO mode has defined a brightness level of 0, the Flat Cal Wizard will emit a warning, but will still allow the run to continue if desired. This option will not change the brightness values you currently have defined for the filter.
- Manual Brightness Values: Ensure that the checkbox to Override filter brightness values with the manual value is checked. This behavior will override and overwrite any brightness values that you currently have stored with the filter. Using this option, the Flats Cal Wizard will find the required exposure length for the calibration mode using the current brightness of the flat box. This option will change the brightness values you currently have defined for the filter.
Note: Using the manual brightness value for the calibration run will use the same brightness level for all filter / binning / ISO modes. If you want to use different brightness values for different modes, you can define them using the normal Default Brightness Values mode (described above) or you can perform multiple calibration runs (one run per brightness level).
If you're using a filter wheel then your "Modes" window should look something like the following:
However if you're using a DSLR the binning values will be replaced with ISO Values. Also if you're not using a filter wheel then you will just see the options to set the binning or ISO values.
Select the Binning or ISO values for which you would like to run the calibration.
Next you'll need to enter some parameters to characterize your flats in the Parameter Selection.
- Target mean: This indicates the ADU that you would like to obtain for your flats. For CCDs this value is generally between 20,000 and 40,000. Ideally you want to your flat data to fall in the area where your CCD behaves in a linear manner. You man need to consult your CCD manufacturer to obtain this information, but typically CCDs behave linearly under 40,000 ADU.
- Tolerance: How close must the Flats Calibration Wizard come to your Target mean ADU value before calling the exposure time good. Generally for CCDs this value can be a couple hundred ADU. However for DSLRs this value generally needs to be higher because they are not temperature regulated and don't have as linear as a response as a CCD.
- Minimum exposure: The minimum exposure time that is acceptable for your flats. Again this will depend on your camera. If you have a non-uniform shutter (Qhy9) this value will likely need to be higher than if you have a uniform shutter (SBIG 8300).
- Maximum exposure: The maximum exposure time that is acceptable for your flats. This will depend on your light source and the filter you're using. This is mainly just to give Sequence Generator Pro a stopping point when finding the exposure time so that it doesn't continuously adjust the exposure. Setting this to 0 does indicate no maximum, so use accordingly.
Once you have the above values filled in with reasonable values click the "Start" button to run the wizard. The "Modes" will then display what binning/ISO is currently being calibrated and the status of any previously attempted runs. Refer to the "Key" section of the Filter and Mode Selection for information about what specific symbols mean.
Saving and Using the Calibration Data
When the calibration routine completes, you will need to save the data for future use. If your calibration source (step 1) was a profile, this data will be saved to the profile. If your source data was the current sequence, this data will be saved as part of the sequence.
Once saved, this data can be used in one of two ways:
- From the flats wizard: Using this tool, you can use existing light sequences to automatically create a variety of flats events (that use this data).
- By selecting an event type of "flat": Selecting this type will automatically populate events with the appropriate exposure length (as determined by the calibration routine) and count.