Firecapture is a feature-rich astronomy program, designed by Torsten Edelmann. Its purpose is to control the operation of cameras used in high speed digital video imaging of the planets and other solar system objects.
This page attempts to help those less familiar with the program to find out how to get the most out of it, by explaining what some of the most important features do and how to set them.
This page is not intended to be a comprehensive user manual for Firecapture and not all features are explained. Torsten has several very good tutorials which you can find on his website. By necessity some of the screenshots shown will be of older versions of Firecapture but where the functionality of the feature changes I will try and update the image and description.
- Defining an ROI – L Click and Drag method
- ROI – Control Panel Method 1
- ROI – Control Panel Method 2
- Defining an ROI via Preview Pane
- ROI/Max size Toggle
- ROI Resize
- Manually Moving the ROI
- Centre ROI
- Centre Planet in ROI
- Auto-center Planet in ROI during Capture
- Lock CofG in ROI during Capture
- Speeding up the responsiveness of automatic movement of ROI
- Defining the size of the CutOut box
- Histogram Sounding
ROI- Controlling the ROI Size
The Region of Interest (ROI) is a feature where you reduce the area of the chip used. Only the data in a user-selected region of the chip is then sent to the computer. Reducing the area of the chip like this can allow faster frame rates (if not exposure time limited) and will also mean less storage space being required per run.
There are various ways in Firecapture to define the size of the region of interest as described below.
Defining an ROI – L Click and Drag method
I prefer the Left click and Drag method. This is the easiest method to define an ROI as you can easily tailor it to contain the features you want to record and you know just where the ROI will be located.
To use this method just hold the left mouse button down and drag the cursor to form a rectangle around the object; then hit the OK button.
Defining an ROI – Control Panel Method 1
There are a whole range of other methods to define the ROI but these will locate the ROI at the same position it was last used which many not be where you want it.
At the top of the Control Panel in the Image box, click the arrow on the right hand side to implement the current ROI displayed. If you want, you can type in alternative values for height and length of ROI before then hitting the arrow to action it.
Defining an ROI – Control Panel Method 2
At the top of the Image section of the Control Panel, click the down arrow on the right hand side and select one of the displayed ROIs.
Defining an ROI via Preview Pane
ROIs can also be set by right clicking on the preview screen and selecting one of the ROI choices that are then displayed.
ROI/Max size Toggle
You can easily switch between full chip and ROI by clicking either on ROI or on Max in the Image box at the top of the Control Panel. Alternatively you can add the toolbar button for this action to the preview screen and click on that.
My preferred method is to set up a keyboard hotkey (Settings/Shortcuts) and assign a keyboard letter such as ‘m’ to ‘Toggle Max image size/ROI’. Then when you hit ‘m’ on the keyboard it switch between ROI and full frame or back again.
Your ROI can be proportionally enlarged or reduced by the default keyboard shortcut of holding the shift key down and using the up/down cursor arrows.
ROI- Controlling the ROI Position
You can control the position of the ROI relative to the borders of the full frame or relative to a planet as described below.
For the ROI to be automatically positioned relative to a planet, Firecapture has to compute the centre of the planet and it can only do this if the profile selected has ‘Planet’ selected under the AutoAlign option. If set to ‘Surface’ or ‘None’ then Firecapture will not be able to automatically move the ROI relative to the object.
Manually Moving the ROI
You can manually move the position of the ROI within the full frame by the default keyboard shortcut of holding down the control key and using the cursor arrows. Each click of the cursor will move the ROI by a set number of pixels. You can alter the size of this step at the bottom of the ROI dialog box – see the figure for the section above entitled ‘Defining an ROI – Control Panel Method 2’.
You can centre the ROI in the middle of the frame by clicking on the ‘Centre ROI’ toolbar button – provided you have added it to the toolbar listing. Alternatively you can set up a keyboard shortcut and click on a preselected key on the keyboard.
Centre Planet in ROI
You can reposition the ROI so that the planet sits in the middle of it, by clicking on the ‘Centre planet in ROI’ toolbar button – provided you have previously added it to your toolbar listing.
Alternatively you can set up a keyboard shortcut for this feature and click on a preselected key on the keyboard. I like to assign the space-bar to this very useful feature.
Auto-center Planet in ROI during Capture
Although you can manually trigger the repositioning of the ROI so the planet you are imaging is relocated to the centre of the ROI it is useful to have this happen automatically, especially if the tracking on your telescope is not so accurate. If enabled, then during recording, the ROI will peridically move to bring the planet back to the centre of the ROI. If the planet keeps drifting, the ROI will move in a stepwise fashion across the full frame following the planet as it moves, until the ROI hits the edge of the full frame. Then it can track it no longer and the target drifts off the edge of the CMOS/CCD chip.
Activation of the feature occurs when you click on the feature’s toolbar button or when you click on any keyboard shortcut for the feature, that you may have previously set up for yourself. A tick alonside indicates that this feature is active.
This excellent feature only operates during capture, so if the planet is about to go off the edge of the ROI during preview use the manual recentring method described in ‘Centre Planet in ROI’ above.
The Auto-centre function has a very useful feature built-in to it, which allows you to visualise where the ROI currently is within the full frame. Is it near the middle of the chip or is it close to one edge, in which case you might you lose the planet off the edge of the chip shorlty. The feature comes into play when the ROI is triggered to reposition itself. At the moment the ROI moves to recentre the planet and for a second or so afterwards a red box appears within the ROI. This red box represents where the ROI is within the full chip – indicating its position relative to the edges. Of course your dispayed ROI might be a different shape than the full frame but to understand where it is this way is extremely useful.
Auto-centring of the ROI can be triggered when the centre of the planet moves a little way off centre or when it is close to the edge of the ROI. To change the setting click on the toolbar down arrow to see the border distance options. The value you pick is the % distance of the length or width for the trigger border – if the planet’s centre wanders into this border recentring is triggered.
Lock CofG in ROI during Capture
The ‘Lock Cof G in ROI during Capture’ feature is similar to the ‘Auto-centre Planet in ROI during Capture’ feature except that instead of the planet being recentred in the ROI it allows you to maintain an off-centre location for the planet. Such a feature allows you, for example, to capture the planet and a moon with the planet on one side of the ROI and the moon on the other side of the ROI. You could achieve this with the planet at the centre of the ROI but you would need a much wider ROI. The feature is much more efficient.
As the ‘Lock Cof G in ROI during Capture’ feature tries to do something quite different than ‘Auto-centre Planet in ROI during Capture’ the latter is disabled when you select it, to stop them ‘fighting’ each other.
The offset location within the ROI is defined when you apply the feature and is indicated with a cross. Activation of the feature occurs when you click on its toolbar button or when you click on any keyboard shortcut for the feature that you may previously have set up for yourself. A tick alonside indicates that the feature is active. With the feature active, when the planet wanders more than a certain distance from the intial start position the ROI repositioning is triggered. The ROI then moves to bring the planet back to the original offset position.
As with Auto-centre planet the feature is only active during recording and only applies when the object profile is defined as a planet.
You can decrease or increase the amount it can drift before activation by clicking on the down arrow associated with the toolbar button. The dialog box which then comes up is shown below.
Speeding up the responsiveness of automatic movement of ROI
The default rate at which the ROI is repositioned to keep a planet in a central position (for ‘Auto-centre Planet in ROI during Capture’) or in an offset position (for ‘Lock CofG in ROI during capture’) is once every 3 seconds.
If your telescope tracking is not great, or you experience windy conditions, then an adjustment of the ROI once every 3 secs may not be enough to prevent the planet occasionally moving outside the ROI. In this case more frequent shifts in position of the ROI would be beneficial. You can speed up the responsiveness of the ROI movement by editing the Firecpature ini file on you C:drive. Search for the LongTasksEverySeconds or LongTasksEveryMilli and try reducing it to 1second or 1000 milliseconds. Save the file and reopen Firecapture
Auto-align is a feature which stabilises the planet’s image in the preview screen. The data downloaded from the ROI is shifted in X and Y to keep the centre of gravity in a central position on the screen. The feature is especially useful to aid in achieving accurate focussing, as it removes movement due to mechanical movement due to the focus motor as well as any movement due to the atmosphere, both of which help achieve the best focus.
Auto-align can be activated by clicking on the toolbar button or by associating it with a keyboard shortcut and clicking that key. I assign the keystroke ‘a’ to the feature. A tick alonside indicates that the feature is active.
When auto-align is activated the planet looks as if it is staying central within the ROI defined on the chip- but that is an illusion, the planet may actually be close to drifting out of the ROI. To know where the planet is within the ROI the feature uses 4 small red boxes to mark the true position of the planet within the ROI. In the figure above these squares are close to hitting the edge of the preview frame. If they do then the planet will start to go off the edge of the ROI and the planet will appear cut-off on one side although it will still be central on the screen. To bring the planet back into the middle of the ROI the latest versions of Firecapture allow you to use the ‘Centre in ROI’ feature in conjunction with Auto-align. I recommend associating a keyboard stroke such as the space-bar with the ‘Centre in ROI’ feature, then, when the 4 red boxes are close to the edge of the preview screen, you can just hit the space-bar to bring the planet back to the central position.
Auto-align can be used during preview and also enabled during recording in which case the planet will be kept central within the recorded area. So that the planet stays approximately central in the ROI during recording so eliminating the danger of a chopped-down planet you could enable ‘Auto-centre Planet in ROI during Capture’.
CutOut (Crop Video)
CutOut is a very useful feature which can save you loads of hard-drive space by just recording the part of the ROI frame with the planet in it. Smaller videos area also much quicker to process in AutoStakkert! CutOut is also call Crop Video and the toolbar button is a pair of scissors but I find this alternative name could be rather confusing, as it seems to imply a truncated video rather than a reduced size for each stored frame.
CutOut can be activated by clicking on the toolbar button or by associating it with a keyboard shortcut and clicking that key. I assign the keystroke ‘c’ to the feature. A tick alonside the toolbar button indicates that this feature is active.
When CutOut is active a yellow box surrounds the planet and follows it closely – above the box it will say ‘CutOut’ and give the size of the CutOut box in pixels. CutOut again only makes sense for profiles defined as planets so won’t work for things like lunar landscape videos.
CutOut usually used in combination with a suitable ROI. The ROI is defined at the camera end and the data within the ROI is transmitted to the computer during capture. However, when the CutOut feature is active, Firecapture analyses the ROI and just saves the data within the smaller CutOut box – anything in the ROI outside the CutOut is not recorded. The yellow box tracks the planet closely and can respond to movements of the planet much more quickly than the ROI so the recording that you end up with has the planet pretty stationary within it. This is the fundamental benefit of CutOut over ROI – its much greater speed of response to changes in position of the planet, which then allows a much tighter box to be defined.
CutOut will work without using an ROI but if you operate in that way the whole full frame will be downloaded to the computer before the CutOut is applied and this may severly limit the maximum frame rate. Better is to use a smaller ROI to improve the frame rate, but which is still quite a bit larger than the planet, then use a significantly smaller CutOut tailored much more closely to the size of the planet. Having said this, with some older cameras you are not able to define an ROI on the chip. In this case CutOut becomes a very valuable way of reducing storage space and speeding up post-processing.
Using the ‘Auto-centre Planet within ROI during capture’ feature with the ROI and the CutOut feature active will mean that if the planet drifts the ROI will reposition itself from time to time to keep the planet in the ROI. If you don’t use this feature or don’t manually move the ROI to keep in view the planet may drift out of the ROI and the CutOut will lose the planet – as a result you will then be recording an empty CutOut box.
Defining the size of the CutOut box
When the feature is active the CutOut box can be redrawn to a different size or shape by holding the Alt key down whilst left clicking and dragging. Forgetting to hold the Alt key down will just mean you redraw the outline of the ROI- which you can then cancel. If you define your CutOut box then apply an ROI where the ROI is smaller than the CutOut then the CutOut size matches the ROI size which is rather pointless as all the benefits of using a CutOut are lost.
You can increase or decrease the size of the CutOut by holding the Cntrl key down and using the Page Up/Down buttons. The buffer resets after each resize step. The pixel step size for this increase or decrease in the size of the CutOut box is set in the feature dialog box which can be accessed using the down arrow on the toolbar button (see below).
Enabling the debayer function by ticking the toolbar button converts the data being sent from a one-shot colour camera into a correctly displayed colour image on the screen.
A one-shot colour camera has a pattern of colour filters over all the sensor elements and typically they are arranged in repeating blocks of 2×2 pixels containing 2 greens, 1 red and 1 blue. This means half of the sensor elements on the chip are green, whilst a quarter are blue and a quarter red. To decode the data read from the chip and to correctly display the colour image Firecapture has to know what the particular pattern of filters is in the block of 2×2. With the proviso that no green elements are adjacent, then four possible arrangements are possible for the colours: RGGB, GBRG, GRBG, and BGGR – known in abbreviated form as RG, GB, GR, and BG.
The correct bayer pattern is programmed in to Firecapture for some cameras and colour displays correctly when used for the first time. For others though you will need to click on the down arrow at the RH end of the Debayer toolbar button and select the debayer pattern it from the listing. Often it is trial and error to pick the right one and something best done on a daylit colour scene.
Debayering creates a potentially much larger file size as a 640×480 colour chip will, for each frame, produce a red image of 640×480, a blue image of 640×480 and a green image of 640×480. Consequently the file size will be 3x larger and the data generation rate will be 3x higher, possibly leading to a reduction maximum frame rate. It is for this reason that Torsten has, by default, arranged to preview the video on screen in colour, but record the frames in RAW undebayered mono, as this minimises storage requirements and maximises the fps.
Storage and fps considerations aside, the choice of debayer algorithm has a bearing on the quality and resolution of the final colour image. It is much better to debayer later with a good algorithm than use a fast debayer method and end up with permanently degraded colour data. The best method for debayering is the default method used in Autostakkert which builds up the ‘missing’ coloured pixels not by interpolation but by a ‘drizzle’ method using real data. In this case no mathematical predictions are required and the colour data is reassembled at the full chip resolution. Another very good reason to leave the data undebayered (mono) for a colour camera when recording.
Until quite recently the preview would be in mono during capture reverting to debayered colour when the recording stopped. From FC version 2.7.03, however, when debayer is ticked the preview is in colour regardless of whether or not you are recording. You can force Firecapture revert to the older action of the preview being in mono during capture by ticking the option ‘Disable debayer while recording’ (this phrasing is slightly misleading, as it may lead you to think that this applies to the recording being debayered if you don’t tick it. I have asked Torsten to change it to ‘disable debayering of preview whilst recording’). Ticking this setting gives you an extra visual clue that you are recording but removes the a key benefit that colour preview brings during capture, which is an improved ability to refocus during your recording.
Although not recommended, for the speed and data storage limitations described above, you can force Firecapture to record in colour if you wish by ticking the ‘Force record in colour’ option under the debayer selection list (see figure above). This might be useful for test purposes or for single frame generation where you might want to view the debayered result right away.
The other option seen in the debayer dialog box above is the interpolation algorithm. As I said earlier debayering takes a mono 640×480 image and from it produces a red image a blue image and a green image each of which is 640×480. Firecapture has to create these from incomplete data, as the green data has only half this number of picture elements whilst the red and the blue have only a quarter. To populate all 640×480 picture elements, an interpolation algorithm has to be selected to, for example, to meaningfully fill in the blank 3 red picture elements surrounding each single real red pixel. The debayer dialog box is where this is selected. Unless you are following the not-recommended route of saving in colour, the exact choice of debayer interpolation algorithm is of little importance as the data is saved undebayered ie without applying any debayer algorithm. The choice will however subtley affect the appearance of the colour preview. The choices are ordered in terms of processing power and complexity. The later ones in the listing, SmoothHue, AdaptiveSmoothHue, and VNG, require a lot of CPU power and should be avoided. NearestNeighborFast is the multi-core version of NearestNeighbor. By default NearestNeighborFast is chosen and should be more than adequate for the preview screen colour rendition.
The histogram feature in Firecapture allows you to see the brightness distribution of the pixels that are in the ROI and indicates what the pixel brightness distribution will be in the captured data. This information will help you adjust the gain and exposure appropriately – ensuring the image is sufficiently bright to prevent quantisation errors but not so bright that areas of the frame are saturated.
Anything that affects the pixel brightness in the recorded data (eg pre-processing functions like contrast or gamma adjustment) will affect the data displayed in the histogram. Some features such as ‘Screen Adjustment’ affect the view on the preview screen but have no effect on the data – these settings will have no impact on the historgram data displayed.
Ticking the histogram toolbar button will display the histogram in the control panel on the LHS of the screen but you can also have further histogram plots displayed at the bottom of the preview screen by enabling the options appropriately. Clicking on the down arrow on the histogram toolbar button brings up an options box which if you click on will bring up the histogram settings box (see below). This then allows you to control the display of the histogram feature.
The ‘Show histogram in preview screen’ option allows you display pixel data either as a simple Horizontal bar or as a Full log-scaled histogram at the bottom of the preview screen.
The Horizontal bar mode is shown in the figure directly below at the bottom of the preview screen and shows the range of brightnesses of the different colours for a colour camera. For a mono camera there would be just a single bar rather than three parallel ones. Horizontal Bar mode is a simple display mode with no indication of the number of pixels of a particular brightness. Insted the right hand end of the bar indicates the brightness of the brightest pixels of that colour as a % of the maximum before saturation (100% is saturated). This is the mode I generally use as I like its simplicity – it just tells me how close to saturation I am for the different colours and allows me to easily set my gain/exposure/colour balance so that the highest value in the bars is about 80% to 85%
Clicking on the ‘Full log-scaled’ option instead displays a fuller histogram at the bottom of the preview screen with information about the number of pixels of each brightness. I find this a little over-complicated and the different colours block each other as the three sets overlap for a one-shot colour camera, although this would not be an issue for a mono camera with only one graph. The histogram rather blocks too much of the preview screen.
At the bottom of the histogram dialog box there are options for the way in which the histogram is displayed in the control panel on the left-hand side. The histogram can be displayed in one of two formats for one-shot colour cameras. If ‘stacked’ is ticked then the three colours are shown as in the top image below with bars representing the current maximum peak for each colour and a distrbution plot for each colour overlayed on one another below the set of bars.
If you tick ‘Separated’ then the three colours are separated out with red at the top and blue at the bottom allowing you to get a much better feel for the separate distribution for each colour. A vertical line at the right hand end of each plot shows the maximum current brightness for that colour – a bit like the RH end of the bars in the mode described above.
For both the Separated mode and the Horizontal bar mode the maximum brightness is dispayed numerically on the left hand side as a brightness count and also as a percentage of the 100% saturation level. The brightness count is shown as the maximum brightness for that colour but also the minimum brightness. For example 0/173 means that the dimmest pixel is brightness 0 and the brightest is 173. The minium brightness is usually 0 in normal night-time imaging, but this may not not the case with imaging the Sun or Moon or if imaging in the daytime – in such a case the minimum brightness might be well above 0.
Another nice feature Torsten has built in, is the pixel brightness reading for the current cursor position. The RAW brightness of the pixel, at the location where the cursor stops, is posted at the top LH corner of the histogram as seen below (where the brightness is 93). The value is displayed close to the red max/min values but is nothing to do with just the red – it will read the RAW data value regardless of the colour filter on top of the pixel. Note that the value only updates when you move the cursor again.
In case you wondered what the histogram looks like for a mono camera this is shown below – nice and simple and a combination of the Stacked and Separated types shown above with one bar and one distribution plot. For mono cameras there is only this combined mode and ticking the different Horizontal bar/Stacked options makes no difference.
Another option in the histogram settings box is the ‘Show colour histogram in RAW mode’ setting. Ticking this gives you histogram information for all three colours for one-shot colour cameras, even if the display switches to monochrome during capture as a result of selecting that older functionality in the debayer settings (by having ‘Disable debayer while recording’ ticked in the debayer settings – see user Debayer section here). With the more modern functionality when the preview screen remains in colour during capture ticking this has no effect the plots continue display as separate R/G/B.
Histogram calculates the pixel brightness distribution at a default rate of 2Hz although this can be changed at the top of the dialog box. Another available setting is the pixel block mode which by default is 4×4 pixels but can be set from 1×1 to 10×10. The default 4×4 means that Firecapture using brightness data from every 4th column and every 4th row down. This reduces the processing load on the CPU
The ‘calculate histogram in separate thread’ option is best explained by Torsten himself: By default the histogram will be calculated in the cam worker thread which also reads the images from the camera. If the image has been read the histogram will be calculated. Depending on how much time the system needs this may add some latency resulting into a lower effective framerates. ‘Calculate histogram in separate thread’ will force running the histogram calculation in a separate thread so calling it inside the cam worker will return immediately removing any sort of latency.
‘Show Emil Kraaikamp Noise estimator (mono cameras only)’ to understand this just click on the ? button alongside. Warning it’s quite advanced stuff!
A value useful but rarely used feature of Firecapture is the Histogram Sounding button which you can add to your toolbar set or set a keyboard shortcut for – I use the keyboard letter ‘v’ to activate.
Enabling this feature gives an audible tone whose repetition frequency is brightness dependent. With this enabled you can tell your planet or other object has entered the ROI without even looking at the screen. This is useful for attempting to locate objects whilst looking through the finder. The feature comes into its own as instant feedback when tracking the ISS whilst following it through the finder giving encouragement to stay on target!
Print Timestamp into Data
Here is another useful Firecapture feature. This one prints a timestamp into the frame, for recordings where the timings are important. When the feature is enabled, the time in UT is printed into the top left hand corner of each frame as in the figure below. The timestamp appears in the preview frame too when not recording.
For highly accurate timings, such as occultations, even when the clock has recently been synchronised, there are complex reasons that the recorded frame times may be not be as accurate as you may at first think, with sub-second errors creeping in. In those cases it is better to rely on other methods that are more accurate and advice needs to be sought from occultation observers such as the BAA asteroids and remote planets section.
Reset Capture Counter
When referring to your files during recording sessions in any note taking, or later when processing, it is really handy to have a shortened name to describe each of the videos, rather than writing down the time that it was taken. This is where the Firecapture Capture Counter comes in.
Under Capture Settings if you tick the ‘Capture counter’ option in filename properties then Firecapture will add an ID number, starting at 1, to the filename in the order specified in the Filename properties area of the dialog box. The index number will increase by 1 each time you record a file.
If you start a session within 8hrs of the previous one, then the index numbering will continue where the previous session ended and won’t reset to 1. If you want it to reset to 1 just click on the Reset Capture Counter toolbar button
Screen adjustment feature allows you to alter the appearance of the preview screen without affecting the recorded data. This is particularly useful to boost the contrast to help with focusing on inherently low contrast objects.
To activate this feature you can click on the toolbar icon or set up a keyboard shortcut to quickly access the ‘Screen Adjustment’ settings screen shown below.
The long button at the top of the dialog box is what you need to click on to activate the feature. Clicking on it will change it from inactive (it will say ‘Enable screen adjustment’ and have a green tick in front of it) to active in which case it will have a red cross in front and say ‘Disable screen adjustment’. Like all these things that are a command rather than an indication of state they can be a bit counterinuitive, but if you see the yellow warning triangle overlying the toolbar button you know it is currently active. This warning triangle is present even if you click away to remove the dialog box as a useful reminder that what you see on the preview screen will not necessarily look the same as your captured data.
The screen settings available are for adjustment are gamma, brightness and image inversion. You can click on these and immediatley see the impact on the preview sceen and see whether they help with things like focussing.
A new addition since 2.7.06 is the ability to show the red, green or blue channel individually as this may be of some benefit. To do this click on ‘Channel’ and then pick your colour. The raw data is shown in monochrome and interestingly the green is the least noisy. This is because as there are twice as many green pixels as red or blue in the bayer matrix.
Do be aware that the histogram plot is blind to these new settings and gives a proper indication of what the brightness distribution is like in the data that will be captured. The image can be burnt out on screen and the histogram look okay and the captured data be fine. If the histogram and the captured data are over-exposed there are no preview settings that will allow the image to look okay. You will then see fully-saturated patches – just that they may not be at 100% brightness.
These sections are still to be completed but give you an idea of what sections are waiting patiently in line to be written!
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ADC Tuning (colour cams only)
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Zoom and Scroll for Preview Screen
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