After starting oaCapture you should see a screen like this:
The main controls are at the top and there’s a status bar at the bottom with a scrolling area for previewing the image from the camera in between.
Program control and configuration
Menus for controlling and configuring the application itself appear at the top. First is the “File” menu:
At the moment the “Save” and “Reload” configuration options do nothing, so “Quit” is the only useful choice here. The current configuration is saved when the program exits unless configured otherwise.
Next is the “Devices” menu:
This shows any currently recognised cameras and the interface used to connect to them. “Disconnect” disconnects the camera and “Rescan” rescans to update the camera choices after cameras have been added or removed, so it is possible to connect a camera and use it after the application has started.
In this case a ZWO ASI120MC has been found via the ZWO ASI SDK, and a TIS DFK21.AU618 using the Linux V4L2 kernel interface.
The “Options” menu enables various components of the application:
“Histogram” opens a new window to display a histogram for the captured data.
“Reticle” displays a reticle over the captured image in the preview window.
“Flip X” and “Flip Y” flip the image about the vertical and horizontal axes respectively. If the camera supports this in hardware then the flipping will be done that way, otherwise in software. Flipping raw colour images may result in unexpected behaviour as the original colour mask may no longer be suitable.
“Demosiac” enables conversion of raw colour data from monochrome to full colour. This can be just for the preview image or for both the preview image and the frame written to an output file.
The “Settings” menu control configuration of the application behaviour:
All these options open the same configuration window at a different tab.
If the “Load and Save Settings Automatically” option is selected then any saved program configuration will be loaded when the program starts and similarly saved when it exits. Hopefully most of the other settings should be self-explanatory. “Write capture settings to file” enables writing a file of the same name as the file of captured data, but with a “.txt” extension. This contains the camera settings used when the data was captured.
Adding a profile saves the current camera settings for later use. A meaningful name for the saved settings can be entered in the left-hand panel. These are then available to chose from the “Profile” menu in the capture settings panel.
Sets the names of the filters that can be selected in the “Filter” menu in the capture panel.
Autorun enables a sequence of capture runs to be completed one after the other. The number of runs and the delay between them can be configured, then click “Enable Autorun” to set oaCapture start next time the capture button is clicked in the capture pane.
When the image is RGB, the histogram can be displayed either as one histogram with the three colour graphs laid on top of each other, or as three separate graphs.
Normally the histogram will stay on top of all other windows, but the second option here allows that behaviour to be turned off.
The first two options here set the handling of raw colour data when the “Demosiac” selection is made from the “Options” menu. Either just the preview window can be converted to RGB, in which case data written to files will remain in raw form, or both can be converted to RGB, or just the data written out. The last choice is probably not very useful.
The second group of options select the CFA pattern to use. If you’re not sure it may be helpful to set up during the day and change options until the colours look correct. It is usually fairly obvious when they aren’t. Note that at one time the software TIS provided with their cameras cropped off the first line of the image so the pattern they document may not be the correct one to use here. GBRG is the correct pattern for the TIS cameras that I have tested.
The final set of options used allow the algorithm for the raw to RGB conversion to be selected. “Nearest neighbour” is fast but low quality. Bilinear is slightly slower, but does a far better job and should be preferred. Smooth Hue and VNG (Variable Number of Gradients) may well be too computationally intensive for many machines.
Controlling the camera and capture
The Camera pane allows the preview to be turned on and off (this should not affect capture to files), to set the application to a dark red colour for nighttime use and for enabling 16-bit mode, 2×2 binning and raw mode for cameras supporting those features.
16-bit mode is currently only enabled for mono cameras, as is 2×2 binning. Raw mode is only available for colour cameras supporting both RGB and raw data transfers.
The image pane allows the size of the captured image to be set. Where a range of resolutions is offered by a camera driver however, these appear in the drop-down beneath the “Max Size” option and can be selected that way. The ROI selection supports selection of arbitrary size regions if the camera supports it. To select an ROI click on the ROI selector and then enter the size required. oaCapture may adjust the size if the camera enforces other constraints (eg. the ASI120 cameras require the ROI to be a multiple of 1024 pixels). To apply the new resolution click on the “square” button.
“Max Size” chooses the largest resolution supported by the camera.
Preview Zoom Size
The Zoom panel allows the size of the preview image to be changed. This does not affect captured data written to a file, just the on-screen view. The three buttons allow direct selection of a fixed scaling of image whereas the slider beneath them allows arbitrary scaling from 25% to 300%. The actual values for the three buttons can be changed by selecting them from a menu by clicking on the arrow at the right of each button:
Camera Exposure Controls
The Control menu enables setting of gain, gamma, brightness, frames per second and exposure time where the camera driver offers those options. The values can be set by moving the sliders, by clicking on the up and down arrows in the boxes at the ends of the sliders or by directly typing values into the boxes.
The gain, exposure time and frame rate sliders are always present if the camera supports those controls. The two other sliders are user-selectable from the entire range supported by the camera. Just pick the ones required from the drop-down whenever they’re needed:
Some cameras allow a specific exposure time to be set which oaCapture will show as milliseconds. Others use an arbitrary scale.
Where the range of exposure times is large, a drop-down menu is shown with varying ranges available for the current range of the exposure time slider:
This pane controls functions relating to the capture process.
The “Profile” menu allows selection of preset values for the camera settings from those previously configured in the settings configuration. The button to the right of the menu restores the settings associated with the profile currently in use in the event that they have been changed.
The “Filter” menu selects the name of the filter in use. For the moment the only effect of this option is to change the name used in the substitutions for the filename on the next row.
“Filename” sets a template for the names of the files saved by the capture process. Substitutions are made in this name from the following set:
|%D or %DATE
|the date, in the form YYYYMMDD
|%T or %TIME
|the time of day, in the form HHMMSS
|both of the above: YYYYMMDD-HHMMSS
|%P or %PROFILE
|the profile name
|%F or %FILTER
|the filter name
|%Y or %YEAR
|the current year, YYYY
|%M or %MONTH
|the current month, MM
|%d or %DAY
|the day of the month, DD
|%h or %HOUR
|the current hour, HH
|%m or %MINUTE
|the current minute, MM
|%s or %SECOND
|the current second, SS
|%E or %EPOCH
|seconds since the epoch (1/1/1970 00:00:00)
|%I or %INDEX
|the number of frames captured since the application was started
The three buttons to the right of the Filename box allow the current directory for saving captures to be changed, the last capture to be deleted and viewing of the contents of the capture directory.
The “type” menu selects the file type for saving data. Only AVI, SER (v3) and TIFF are supported in v0.0.4 where the capture format allows them. TIFF is not available for raw capture for instance because it cannot store raw frames. When using TIFF separate files are created for each of the captured frames. To prevent the files all having the same name the “%INDEX” substitution can be used in the filename.
The Limit checkbox, when checked, allows setting a limit on the number of frames in or the length in seconds of each capture file. Checking the box opens up options for selecting the number and type (see the image below).
The first two of the final row of buttons start and stop the capture run. The final button is used when “autorun” is enabled:
Once an autorun is complete (progress is displayed alongside this last button), clicking this button resets the autorun values to those chosen in the “Settings” window. This allows another autorun to be started without having to open the settings window again.
FInally, the status bar from left to right contains:
- An area for status messages
- The current camera temperature, should it be available
- The theoretical maximum number of frames per second based on the frame rate or FPS setting
- The actual number of frames per second
- A count of the number of frames captured in this run, and following that
- A progress meter