One Shot Color (OSC) and DSLR Cameras
Getting Started with Sequence Generator Pro and a One Shot Color Camera (or DSLR)
Sequence Generator Pro is an extremely powerful image capture suite. It can perform many complex tasks in order to meet your imaging needs. That said, SGPro is also extremely intuitive and easy to use for beginners. In short, SGPro can be as powerful as you want it to be.
This tutorial will cover the basics to start up, create a sequence and run it. We assume that you will be using only a one shot color (OSC) or DSLR camera. In addition, we cover some important in-sequence topics like dithering and histogram stretching. While we recommend using other equipment to automate your imaging sessions, we will reserve those tutorials for later.
In order to run through this tutorial in the comfort of your home, we will be using the ASCOM camera and color filter wheel simulators. These are installed when you install ASCOM. When connecting your own gear, you will need to ensure that all required ASCOM drivers are installed prior to starting SGPro.
If you are not familiar with ASCOM, it is an acronym for “Astronomy Common Object Model” and, with it, we are able to provide support for a broad spectrum of gear in a very short period of time. It’s not critical that you understand the details of ASCOM, just that you are able to install it and that you can find ASCOM drivers (like any other driver) for your specific gear (QSI, FLI and SBIG being the exception to this rule).
One note about this tutorial: This is a combined lesson on both One Shot Color (OSC) CCDs and DSLRs. The primary difference between these is that CCDs support "binning" (convincing to camera to consider a larger group as pixels as a single pixel) and DSLRs support ISO (sensitivity) values. We do our best to call these differences out, but you must keep in mind that there is no DSLR simulator. This means that even if you are using a DSLR camera, you will need to use the OSC simulator for this tutorial.
Let’s get started...
Installing prerequisites: Sequence Generator Pro is dependent on:
- ASCOM 6 or better. If you have not done so already please install ASCOM (http://ascom-standards.org/Downloads/Index.htm)
- Microsoft .NET 4 Framework (http://www.microsoft.com/en-us/download/details.aspx?id=17851). This should be installed automatically when SGPro is installed.
- While SGPro is not technically dependent on an auto guider, you will almost certainly use one. PHD2 is a free, open source, and community supported auto-guider: http://openphdguiding.org/
Open Sequence Generator Pro: When you start, you will see a large window that contains several configurable modules on the left hand side. We will not discuss all of these modules in this tutorial, but will cover some that are essential to the image capture process. In the middle of the main window, you will see the “Sequencer” (pictured below). It is here that you will do most of the work when defining a sequence. The sequence window can be closed without fear of losing any of your sequence data. When you close it, you can think of it more as “hiding”. If you close it and need to find it again you can either click the sequencer icon (to the right of the save icon) or hit Ctrl+W.
Understanding the user interface: Before we dive into things, we should take a moment to discuss the SGPro interface. The “main” window is where we display “modules” and image data. Modules are small windows that allow you to perform some type of common action. Examples of modules are the histogram module, image pan and zoom module and the frame and focus module. When you start SGPro for the first time, these modules will be docked to the left side of the screen. You can re-arrange modules to appear in any order you want (they can also be floating). To move a module, simply drag on its title bar and you will see positional arrows appear that will allow for placement above or under other modules. Modules can be docked on either the left or right side of SGPro. Lastly, you can “nest” modules with each other (on top of each other). This will help save some space and is a good option for modules you don’t use as much. To do this, drag a module and drop it on top of another existing module.
Your images will occupy the majority of the screen. Initially, when they appear, they will occupy the all remaining area on the screen (not occupied by modules). Performing actions that result in multiple images being open simultaneously will create a series of tabs across the top of the images (one for each image). By default, images taken with a camera will replace each other in the same image window. As with modules, you can float windows, nest them or place them side-by-side for comparison.
This is what docking a module to the left or right side looks like... The module will turn into a grey rectangle, just drop it onto the icon and it will snap into place:
This is what rearranging a module looks like... To place this module above Frame and Focus, drop it on the "up icon", to place it below, drop it on the "down icon". Lastly, to "nest" it with Frame and Focus", drop it on the middle "tab" icon.
Connecting your gear: Before we start we need to select and connect to the ASCOM simulators...
To use these devices, you will need to select them from the upper right hand corner of the sequencer. Go ahead and select the camera simulator and attempt to connect (using the red connect button).
Note: While we are using simulators, you can check now if your gear shows up on these drop down lists. If your gear does not appear here, you will need to install the appropriate ASCOM drivers and then restart SGPro. If you are using a Canon or Nikon camera, there is no need to install ASCOM drivers.
Creating the sequence: When a new sequence is created (a new one was automatically created when you opened SGPro), it will contain a default target in the upper left hand corner named “Target Set 1”. It is named “Target Set”, because it contains a “set” of events to execute (more on this in a moment). Most people will rename this to something more intuitive like “M42”. To modify properties for your target, simply right click on it and select “Target Properties”. There are many fields on this dialog but they are representative of more advanced topics. For this tutorial we will focus only on the “Name” field. Go ahead and enter the name of the target you would like to capture and click “OK” (any name is OK here). You will see now that the target name (in the sequencer’s target list) has been updated to reflect the name of the target you chose.
Click the gear icon next to "Target Set 1" to open the settings dialog:
So now you have a target… you’re not ready to go yet. First we need to decide on and create events and frames for each target (in this case, just one). Occupying the entire bottom area of the sequencer you will find the event table. This is where you will apply all of the minutia that defines your sequence. For example, lets say you want to capture 3 hours of data for your target. In addition, you would like to limit the exposure time of individual exposures to 10 minutes each. By default SGPro provides five empty events. You can add more by using the button in the lower left hand corner. In addition, SGPro will only execute events that have the “Run” option checked.
So... to get what we want here, go to event 1 (Run will already be checked). In the “Type” column, keep the event type as “Light”. In the “Filter” column, leave this a "None". The “Suffix” field can be anything you want (including blank). The suffix simply allows you to optionally provide some text that you would like to appear in file names for all images created by this event (described below). Next, set the “Exposure” time. You can use the drop down for a set of common intervals or you can enter the value in by hand. If you enter just a number by itself, this will be interpreted as seconds. The values 5, 600, and 0.01 all represent exposure times in seconds. Alternatively, you can use “m” after any number to force SGPro to interpret your entry as minutes. The value 10m is simply 10 minutes or 600 seconds. Go ahead and enter 10m or 600 here (for this simulation go ahead and substitute seconds for minutes… enter 10s instead of 10m or you will be watching the simulators do nothing all night).
For OSC CCDs:
Next, choose your “Binning”. SGPro, for most cameras, supports binning from 1x1 to 4x4 and values in-between. For our event, go ahead and keep 1x1 selected. Lastly, fill in the value for repeat. We are after 3 hours of data so we will enter 18 here. That’s the gist of creating an event (this one has 18 frames).
Here is what your event table should look like:
Next, choose your “ISO”. SGPro, when it connects to your camera, will query it for available ISO values. For our event, go ahead and select an ISO value of 800. Lastly, fill in the value for repeat. We are after 3 hours of data so we will enter 18 here. That’s the gist of creating an event (this one has 18 frames). Note, that there is currently no DSLR simulator, so you will need to proceed as though you are using an OSC CCD.
Here is what your event table should look like (use the one above for the rest of this tutorial though):
A few notes about the event table:
- You can move events by using the up and down arrows on the far left
- You can delete an event by clicking the “X” icon on the far left
- You can uncheck the “Run” option to prevent further execution of the event
Specifying the location of your images: Now that your camera is connected, we will specify where and how to save your captured image files. To do so, we will set a few parameters in the upper middle area of the sequencer (the section labeled “Target Data”). First, locate the “Directory” field and then click “Browse”. This will allow you to select the base directory for all images taken by SGPro. Now you may be saying to yourself “That’s silly… I don’t want to save all of my SGPro images to the same directory”. You’re right. We don’t want to do that either. Because of this we have introduced a very powerful file naming system. In the “File Name” field directly below “Directory”, you can specify a custom file naming pattern using quite a few options. For instance, if you want your file names to be named using the target name (the one you specified above), then the type (light, dark, etc…), then the binning, then the exposure length, then its frame (series) number, you would enter “%tn_%ft_%bi_%el_%fn” into the “File Name” field. Pretty easy… But what about the single directory issue, you mentioned above? This is also pretty easy… most folks simply modify their existing patterns by prepending “%tn\” to it. This will create a sub-directory under the base directory named after the target.
As an example, suppose you named your target “M42”. The full entry in the “File Name” field is: “%tn\%tn_%ft_%bi_%el_%fn”. Using the LUM event as the basis for this example, the first frame will produce a file named “M42_Light_1x1_600sec_frame1.fit”. Where will it be created? Let’s assume directory you chose is “C:\AstroImages\” (in the directory field). In this case, because you specified “%tn\” as a prefix to your file name, the full path to your new images will be “C:\AstroImages\M42\”. You can also use this method to separate images by type. Instead, if you used “%tn\%ft\%tn_%ft_%bi_%el_%fn”, the path to your “Light” images would be “C:\AstroImages\M42\Light\”.
In SGPro, the example described above, would look like this:
Clicking the "magnifying glass" preview icon, yiu can see an example of how your data will be saved (using event 1):
Of course, you can create sub-directories using any of the provided pattern tokens. If you forget what options are available to you, just click the “Key” button next to the “File Name” field.
Note: DSLR cameras that use ISO can insert this value into the file name using the "%is" token.
Note: To avoid setting these values every time you create a new sequence, you can set them in the Options dialog and they will be auto-populated for new sequences (Tools->Options menu item).
Setting up the auto guider: SGPro currently supports three different autoguiders (PHD2, AstroArt and MetaGuide). As of now, SGPro does not have its own auto guider so when we say “supports” we mean that we are able to request that the external autoguider perform a dither operation between frames. Dithering is an important part of astrophotography and can help to remove unwanted artifacts when your sub-frames are stacked to form a master frame.
For the purposes of this tutorial, we will be using a special, non-functional auto guider called “Practice Guider”. Please remember not to use this guider outside of simulations like this one… its only purpose in life is to help you learn how to setup and run an autoguider up while indoors (PHD2 is not able to do this very well).
Note: Most folks using SGPro use PHD2 so, despite using the “Practice Guider”, we will discuss guiding like we are actually using PHD2.
To set your auto guider, open the Control Panel again and navigate to the “Auto Guide” tab. Use the Guiding Interface drop down to select “Practice Guider” (note that using this when not practicing, this is where you will pick your actual auto guider). Check the “Dither” option and then choose the dither amount. We use “PHD2 speak” for these terms, but in general, use “Very High Dither” or “Extreme Dither” for shorter focal lengths and the smaller dither options as you increase focal length. Finally you need to define the settling options. Settling options allow for the mount to settle after some kind of disturbance. Typically this disturbance is invoked by SGPro in the form of a dither. This means that if PHD2 is not reporting that both RA and DEC values are below the settling value for a particular amount of time, SGPro will temporarily pause the sequence until guiding has recovered. The settling value is a whole number that defines the maximum allowable deviation (in pixels) from the center of your guide star. Short focal length scopes can generally get away with settle values of a half-pixel or more. Longer focal length scopes will sometimes require more precise guiding and use settle values of 0.2 pixels or lower. The “Practice Guider” will always return a value of 0 for distance from center so you will not get to see any real deviation while going through this tutorial.
At this point, go ahead and save your sequence. Sequence files in SGPro are saved as “.sgf” files. Click the “disk” icon in the upper left or go to “File->Save Sequence”.
Note: Dithering will not work in PHD2 unless you enable the PHD2 server. To do this, open PHD2, go to the “Tools” menu and check “Enable Server”.
Note: SGpro contains a PHD2 module that will allow you to view the quality of your guiding without switching applications. To open the PHD2 module simply click the PHD2 icon. Furthermore, you can customize the color or scale of the graph to your taste. To adjust the colors, simply left click on the RA or DEC labels. To adjust the scale (zoom) simply right click on the graph. This module requires you to enable PHD2 logging or it will not function. To do so, open PHD2, go to the “Tools” menu and check “Enable Logging”.
Setting the camera’s temperature: Most CCD cameras allow for controllable temperatures. As of now, there are no DSLR cameras will controllable coolers, so if you intend to use this type of camera, you can skip to next section. You will obviously want to set your camera’s temperature to the desired value before you start capturing. Failure to do so will introduce large amounts of thermal noise and make your images very difficult to process. The easiest way to do this is to open the “TEC Module” by clicking the thermometer icon. This will open a small window named “Temperature”. In it, you can turn your camera’s cooler on or off and easily set the temperature. Go ahead and do this for the simulator camera now. Click the “On” option to turn the cooler on and then enter the temperature you want to set. For instance, if you want to set the cooler to -10C, enter “-10” and click “Set”. There is a field next to the “Set to” field that will allow you to set the temperature of the CCD over time. Using this feature can help to reduce thermal shock to your camera’s sensitive parts. If you want to set your camera’s temperature to -10 C over a 5 minute period, simply change the “0m” to “5m” and click “Set”.
This is what the camera temperature module looks like:
Note: You can have SGPro automatically cool and warm your camera for you. This is not discussed as part of this tutorial, but, if you are interested, more info can be found here.
Focusing your images: This tutorial does not use a motorized focuser, and, as such, we cannot walk through how SGPro accomplishes “on-target” auto focus (it’s actually quite easy and very powerful). Instead we will focus on two different methods that are available with a normal manual focuser. Both methods depend on use of the “Frame and Focus” module (click the gold star icon to open and position).
Method 1: This method will use a Bahtinov mask and a nearby (to your target) bright star. The object here is to obtain a uniform diffraction pattern (more on this here: http://en.wikipedia.org/wiki/Bahtinov_mask). While not unheard of, it is unlikely that your target will contain a star bright enough to produce this pattern in a reasonable amount of time (a few seconds). This means that you will have to perform off-target focus (moving the mount back and forth between the target and a bright star every time you want to focus). When performing initial focus, you will be using the “Frame and Focus” module. This can be opened by clicking the “Gold Star” icon. This will allow you to place the camera into state where it continually captures images for display purposes only. None of these images are saved to the disk. So… to get started, place the Bahtinov mask over the aperture of your scope (or pretend to since we are simulating… you get the point). Next, specify binning for these frames. In general, for frame and focus with a Bahtinov mask, you should specify the highest binning available (in most cases, this will be 4x4; for DSLRs you will want to use a higher ISO... 800 or 1600 should be fine). This will help with both download times and sensitivity. For this simulation, leave binning at 1x1 because the simulator image is quite small already. Asking the simulator for a 4x4 image will work, but the image will be very tiny. Next, specify the exposure time… for this, a value between 1 and 5 seconds should be appropriate (depending on brightness of the star and binning). Finally, open the Histogram module (Colored Bars icon) and ensure that “Auto Stretch” is checked. If you don’t do this, all of your images will just appear as empty black squares. That’s it! Click “Start” and the camera will begin taking a continuous stream of images you can use to adjust your focuser. When you have achieved proper focus, click “Stop”.
Method 2: This method will use the built-in “Image History” module. This is arguably simpler, but may be a bit less precise depending on the star field you choose (typically the same as the target). The primary advantage of this method is that you don’t need to move off your target to focus (huge time saver). To use this method, click the “Graph” icon to open the “Image History” module. Optionally, go to “Tools->Image History” to open a larger and more detailed representation of the module. Once this is done, start Frame and Focus (same as method 1). This time, in the Image History module, you will need to ensure that the “Enable image history” option is checked. Once enabled, the image history graphs will begin to plot “whole image half-flux radius (HFR)” (a focus metric) and star counts. A binning of 2x2 will normally work best here (again DSLRs can use an ISO value of 800 or 1600 here). Now adjust your focuser to get the lowest possible HFR value. Before you start paying attention to any numbers, make sure to obtain a rough focus (seeing any semblance of stars should be sufficient). The objective here is to spot a “V” pattern on the graph. The closer you move to focus, the lower your HFR value will be. As you move the focuser toward focus, the HFR value will decrease and then, at some point, start to increase. This is an indication that you have passed focus and should go back one increment. When you are done, click “Stop”.
Note: Before starting frame and focus, ensure that you open the “Histograms” module and check the “Auto Stretch” option. If you don’t do this, all of your images will just appear as empty black squares. See the image below...
Framing your target: Pointing the scope in the exact center of your (intended) target can be a daunting task. In this tutorial, we did not connect an ASCOM compatible mount so our framing options are quite limited. Though it is beyond the scope of this tutorial, SGPro offers several, easy-to-use, automatic centering options that can get you within a few pixels of your target in under two minutes. Definitely worth checking out, but we want to stick to basics here…
In this example, we might use a spotting scope, finder or external planetary program to slew the mount near our target. Unless your mount’s alignment (sync), polar alignment and gears are perfect, you will likely not be pointing where you want. To correct this, you will use the “Frame and Focus” module (as described in the “Focusing” section) to start streaming a series of temporary images. A binning of 4x4 is best for the framing process (again, higher ISO values for a DSLR will be better here). Exposure time will vary depending on target brightness. To complete framing, click “Start” on frame and focus and then, using the hand controller for your mount, slowly move the telescope to the desired position and you’re done. You may also be required to rotate the orientation of the camera (most CCD chips are not square). When you are done, click “Stop” on frame and focus.
Note: This process is pretty simple if you are imaging at short focal lengths, but grows increasingly more difficult as your focal length increases. At long focal lengths you will almost certainly need to move to more advanced framing methods.
Note: Before starting the framing process, ensure that you open the “Histograms” module and check the “Auto Stretch” option. If you don’t do this, all of your images will just appear as empty black squares.
Running the sequence: OK… we’ve done a lot and it’s time to review. So far we have found and connected the camera, created a target, defined events for that target, specified where and how to save images, set up your auto guider, learned a few methods for manual focus and finally and learned how to manually frame your target. That’s a lot of stuff and, at the end of this tutorial, we will talk briefly about how to minimize the setup time for future sequences.
Next up, we need to consider the order of the sequence. On the sequencer window, below the equipment area, you will find several options that dictate the order in which the events you defined will be executed. For this tutorial, we will focus only on the “Finish event first” and “Rotate” options. Even though we created only one event here, there are many scenarios in which you would create more. If we had created multiple events, choosing "Finish entire events first" will result in the capture of all frames for the first event (event 1), then each of the other events will be captured as discrete events. A rotating capture is exactly what it seems. SGPro will capture one frame (from event 1) and then move onto the next next event and then onto the next and so on… This is a good option if you would like to get an even distribution of data over a given period of time.
For this tutorial, yours should look like this:
Lastly, you will be responsible for starting PHD2 guiding before you start the sequence. This means you need to connect your gear to PHD2, calibrate and start guiding while you are pointed at your target (obviously not necessary with the “Practice Guider”).
We’re ready! Don’t forget to save your sequence (sequences are saved as “.sgf” files). Click the big “Run Sequence” button in the lower right hand corner.
Checking your images: So now you are cranking out images and life is good. Many folks like to inspect their handiwork as the sequence progresses. First off, ensure that, using the “Histogram” module, you have the auto-stretch option checked so that you can actually see details in your images. You have several options for inspecting images…
In the currently displayed image you can zoom or pan to any location on the image. To zoom, right click on the image and then select the zoom factor. By default all images will be resized (for display purposes only) to fit in the image display area. You may want to zoom to 100% in order to check out the quality of your stars. Other ways to zoom an image include the “magnifying glass icons” on the image toolbar (located directly above each image) and the zoom drop down box to the right of the image toolbar buttons. Finally, you can use the “Pan and Zoom” module. On this module you will find a zoom slider that will let you adjust zoom up to 400%.
Here is a portion of the context menu (right click):
When an image is larger than the display area you can easily move to other areas of the image by dragging on the image and “pushing” it in the desired direction. Alternatively, you can use the “Pan and Zoom” module to drag the small red box to the area of interest. The main image display area will now be representative of this part of the image. Here is what the Pan and Zoom module looks like for images that are larger than the display area:
Lastly, SGPro, will by default, replace the current camera image window data with the latest data from the camera. This means that if you are taking 10 frames as part of an event and you are on event 9, only frame 8 will be shown. All other frames are on disk, but not displayed. If you haven’t been out to check on your images for a while you may be interested in inspecting images that are no longer displayed. To help alleviate the user from having to go open older images through a file selection dialog, we use an “image browser”. The browser uses forward and back arrows just like an Internet browser. If you have frame 8 shown and want to see frame 6, simply click the back arrow twice. Alternatively, you can right-click on either the back or forward arrows and get a menu that shows the last 25 images.
Pausing and aborting: During the course of the sequence you may have need to pause or abort the sequence. There are any number of reasons to do this… you’re done for the night, clouds roll in, pausing for emergency focus, hurricane, etc.
To pause the sequence, you simply click the same button you used to start it (located in the lower right hand corner). When the sequence is running, this button actually changes to read “Pause Sequence”. When you click it, you will be presented with another small dialog that allows you to choose how you want to pause the sequence. You can pause after the current frame is completed and downloaded or you can choose to abort immediately. If you choose to abort immediately, SGPro will not download data from the camera (it will be lost).
Here, you can see that the "Run Sequence" button has changed into a "Pause Sequence" button:
Clicking it presents you with these choices (as described above):
Final thoughts: This tutorial does not cover many of the most powerful aspects of SGPro. It is intended as a primer to get you up and going quickly with just the basics. Below are some notes and thoughts that will help you figure out where to go from here (when you are comfortable moving on):
Save as profile: You just spent a lot of time setting your gear up and tweaking settings. Almost any setting you make in a sequence can be saved to any number of custom equipment profiles. Once you have a profile, you can create new sequences using them and all of your settings will be applied and ready to go with the click of a few buttons. All you need to do at this point is define your events and you’ll be ready to go. More details on profiles can be found here.
Focusing reminders: This tutorial discusses a couple of options for manual focusing. If you are interested in pausing the sequence based on user defined triggers like time, temperature, frame count, etc, you can find more here. Once this is set, and a trigger is hit, SGPro will automatically pause the sequence and inform you that it’s time to focus. When you are done, simply resume the sequence.
Playing around: Almost all equipment types have simulators. Hook them up and play around! You can try to use almost any feature in SGPro just with simulators (Auto meridian flips are one exception to this).
Auto Focus: SGPro can provide you with ability to stay in focus all night. Temperature and gravity will try to destroy your images, but SGPro, simply by connecting an ASCOM compatible (absolute) focuser will be able to automatically focus based on a number of user defined triggers (time, frames, temperature, etc). More information on this can be found here.
Easier framing: In this tutorial we discussed a very manual and time intensive method for framing. One of the most powerful features found in SGPro is the ability to find your target and start imaging in minutes. In order to do this, you must install one of three plate solvers (Pinpoint, Elbrus or Astrometry.NET). Once this is done SGPro will interface with your plate solver in order to move the mount, with high accuracy, to your intended target. In addition to this, you can easily recenter on one of your images from a previous night or find an image on astrobin.com or flickr.com that you would like to use for framing your own image. More on this can be found here.
Getting more help: SGPro contains a fairly extensive help file (this document is also included in there). When in SGPro, you can get to the help file by going to “Help->Help File”. SGPro also offers tooltips on almost every single button and control available. To access these, just ensure that you click on a control and then hover over it with the mouse. Finally, feel free to post on our Yahoo! group (http://groups.yahoo.com/group/mainsequencesoftware)… we will be happy to see if we can help.