Current for Multi245 version 30g
Here are a few potential astronomical applications for Multi245. As you become familiar with the functions that Multi245 provides, you will undoubtedly think of many more possibilities.
Shoot ultra-deep-sky images. This task is accomplished using the Track-and-Stack (TS) command. It can track and stack hundreds of exposures to reach the deepest possible magnitude with your telescope, even if its drive system is not perfect. Suppose that you have taken 81 integrations each 2 minutes long of Messier 51. Although most of the frames are well tracked, the galaxy moved around the frame during the imaging session and a few frames show trailing. First you check the images using the view list (VL) command and reject 6 with trailing, for a net of 75 good frames. After removing a master dark frame from each image, flat-fielding, and gammalog scaling, Multi245 registers each of the 75 images in perfect overlay to create a single image of M51 equivalent to an ultra-deep 5-hour exposure.
Show comet and asteroid motion as movies. Preparing the images is a job for the Register List (RL) command. Imagine that you have taken 150 60-second exposures of a comet uniformly spaced over a 4-hour period as the comet moved against the background stars. After removing a master dark frame and flat-fielding each image and brightness scaling, you register each of the images against to the background stars. When this set of registered frames is converted into an movie using the Make Movie (MM) command and viewed using the Show Movie (SM) command, you will see the 4-hour motion of the comet compressed to 15 seconds. Later, you make another movie registered on the moving comet, so the comet stands still while the stars appear to move across the screen behind it. In an active comet, you may see motion in the jets.
Search for a asteroids and supernova.Blink two or more images by making a "mini-movie." Suppose you have taken two frames of the same sky region one hour apart. You make a list of the two images and register the second against the first. The Show Movie (SM) command allows you to see the images in rapid succession. Asteroids stand out because it appears to hop back and forth. Supernovae appear to blink on and off.
Make master dark frames. Use the average list (AL) command. While shooting an ultra-deep-sky image, you took a total of 80 dark frames. First you use the view list (VL) command to inspect each dark frame, rejecting 3 frames with cosmic-ray hits. You then average the remaining 77 frames to form a nearly noiseless master dark frame.
Make a master flat-field frame. As dawn came, you shot a 20-frame sequence of 2-second twilight-sky flat bright frames and 20 flat dark frames of 2 seconds exposure. You make a list (ML) of the flats and the darks and inspect each image for defects. There are none. You average each list using the AL command, then subtract (SU) the master flat dark from the averaged raw flat to produce a high-precision master flat-field frame.
Multi245 requires a PC with 600KB of memory available for programs (at the DOS prompt, type MEM /C /P to see how much standard memory is available for programs) and a graphics card that supports standard VGA display. Any monitor capable of displaying VGA graphics will work with Multi245. Multi245 uses the 320x200x256-color display mode, so if you are processing on a portable with an LCD screen, and the screen should be able to support at least 64 levels of gray so that you can clearly see screen images.
For optimum operation, you need to set up a RAM drive, that is, to configure some of the machine's high memory to act as a very fast disk drive. To average and to track-and-stack, Multi245 creates a swap file, and RAM drive is faster than a hard drive.
To create a RAM drive, add the following line to your CONFIG.SYS file:
DEVICEHIGH=RAMDRIVE.SYS 512 /E
To get more information on RAM drive, type HELP RAMDRIVE.SYS from the DOS prompt. After adding this line, run MEMMAKER and follow its instructions to optimize the use of high memory. The swap file occupies approximately 380KB.
If for some reason you cannot set up a RAM drive on your computer, then you should put the swap file on a fast hard drive. If you run Multi245 in a DOS window under Win 95, Win 95's built-in I/O caching allows very fast action from a file that is on the hard disk.
For single images: To examine a single image, Load (LO) the image and then type the Edit (ED) command to view or edit it. The Set Display (SD) command allows you to customize the image display for viewing lists of similar images.
For just a few images: You can blink two, (or three, or more images) by making a two-, three-, or more-frame "mini-movie" of registered images. Blinking allows you to see subtle differences between frames.
For many images: To register or track-and-stack composite many files, follow these steps.
DI [Directory] allows you to see the files in your LoadPath directory. With proper naming conventions, you can set the file specification to view subsets of images, such as all dark frames. Careful conventions in naming your images can be extremely valuable.
LO [Load] retrieves a single image from disk. When you load an image, Multi245 creates a list containing just one image. Multi245 recognizes and loads following image formats:
Cookbook 211 images using the .PIX format
Cookbook 245 images using .PA/B and .P1/2/3;
Cookbook FITS images in the .FIT or .FTS formats.
SA [Save] Writes an image to a disk. The extension you use for the file name tells Multi245 how to store the image. Multi245 saves in the following image formats:
Standard FITS files using .FIT and .FTS.
Standard TIFF images using .TIF;
If you specify the FITS format, you will be prompted for header information. FITS is used by NASA for the exchange of scientific data and images; it is the lingua franca of the astronomical imaging world. For the TIFF format, the standard medium for sending images to publications, the TIF extension tells Multi245 to save the image using an aspect-ratio corrected format. For PIX images, the output is 192x192, for 252-wide images, the output is 320x240, and for 378-wide originals, the output file is 378x284.
SU [Subtract] Subtracts one image from another. This command enables you to create a master flat-field frame without leaving Multi245. To do this, first create a list of your flat brights and another list of your flat darks. Average each list, then load the average flat bright and subtract the averaged flat dark. The result is a master flat-field frame.
SD [Set Display] allows you to set Multi245 for the optimum display on your computer's monitor. Type SD and follow the screen prompts. The gamma value compensates for the nonlinear display of your computer's monitor. Monitors for PCs and PC clones usually have a gamma value between 1.6 and 2.2. Setting the display parameters does not change the image in any way, it only changes how the image is displayed on the monitor. The centroid threshold parameter allows you to change the sensitivity of the star detection routine in the star-tracking algorithm. It is best not to change this, but if Multi245 is having trouble locking on, lower this parameter for greater sensitivity or raise it for less. Stay within the range 1.000 to 1.200.
ED [Edit/Examine] displays the current image and the value of the "active pixel" under the cursor. The sample and line of the active pixel, as well as its pixel value (PV), are shown at the top of the screen. The pixel values range between 0 and 4095, and shows the value of the pixel regardless of the display parameters. The display value shows the 8-bit value that is sent to the display screen.
Examine allows you to alter single pixels to improve the cosmetic appearance of the image. Use the arrow keys to move the highlighted active pixel. The [pgup] and [pgdn] keys change the value of the active pixel in small steps, and the [home] and [end] keys change the value of the active pixel in large steps. Changes that you make to the image using the image editor are permanent.
The power of Multi245 lies in its ability to process large numbers of images, thereby making possible observational projects that might not otherwise be possible. It is useful to think of Multi245 as a semi-smart robot that automates compositing images—recognizing that it remains your responsibility to organize the work and tell the robot what to do.
Because you will use Multi245 on large sets of images, it is essential to organize your work space and file names so that you can keep track of which images are where and what has been done to them.
Start by creating a directory for a night's work. On the evening of December 3, 1996, you could make a directory on your D drive named D:\961203. If you name directories in this way, you can easily sort them into date order.
In multiple imaging, it is best to name images serially, starting with a 5-character prefix ("N5128") plus a serial number, such as N5128001.P1/2/3, N5128002.P1/2/3, N5128003.P1/2/3, and so forth, up to N5128999.P1/2/3. It is important to name your images properly as you take them. The serial naming capability built into 245PLUS software makes organized naming easy.
Use the same convention to designate groups of dark frames. For example, give your first batch of dark frames the DARK1 prefix, and they will be named DARK1001.P1/2/3, DARK1002.P1/2/3; prefix the next batch DARK2 and they will be called DARK2001.P1/2/3, DARK2002.P1/2/3, and so forth. Use a standard prefix such as FFBR3 for your raw flat bright frames and FFDK4 for your flat dark frames. Sticking to clear and consistent naming conventions greatly simplifies making images lists for averaging, calibrating, enhancing, and compositing.
Multi245 is structured to protect you against the loss of images that may have taken hours of observing to acquire because it does not save images in the .PA/B, and .P1/2/3 formats. Images that you create will have the .FTS or .FIT extension.
Because of this, you can store your master darks and master flats with the source images. There is no danger to your source images if, when you average your DARK3xxx.P1/2/3 images, you name the averaged output image AVGDARK3.FTS. After averaging your fifth group of flats and flat darks, you would make AVGFFRW5.FTS and AVGFFDK5.FTS, and after subtracting the dark, you could safely name your master flat AVGFLAT5.FTS. The naming convention clearly points to the ancestry of the file, and also allows you to delete DARK3*.P*, FFRW5*.P*, and FFDK5*.P* source files once the master files have been made and tested
After you have finished processing a set of images, make a backup floppy containing end products. (A 3.5-inch high-density floppy should hold 8 FITS images taken in the 378-wide mode. If you need the disk space, erase the source images, since it is unlikely that you will ever need to calibrate, scale, or stack-and-track them again. The ZIP 100 drive, with its 100MB "diskettes," stores about 600 images if you want to keep intermediate files for later reprocessing.
Lists are groups of files for Multi245 to process. They are stored in files with the extension .LST. (Multi245 does not recognize any other extension as a list.) There are three ways to create a list. You can type it in Multi245 using the Type List command, you can generate it from inside Multi245 using the Make List command, or you can load a previously created list using the Load command.
ML [Make List] Creates a list of files to process. You must supply a directory mask and a name for the list file. The Make List function then automatically creates the list file. To make a list of the dark frames in the third group of darks, use a mask such as DARK3*.P1 and put the images in a file named DARK3.LST.
TL [Type List] This command allows you to type filenames that you would like processed. If a list is already loaded, you will be able to edit the names in it. Type each name without extra spaces, and do not include any spaces after the file name. Enter a blank line to terminate the list. Don't forget to save your list after you have typed it. Use the Save (SA) command and give a name with the LST extension.
LO [Load] Retrieves from disk a list of files to view or process. If you've just made a list, Multi245 presents the list you just made as the default. Once you have entered a list file name, it loads the list and displays the image file names. If you have not entered the LoadPath correctly, you will see a message saying that Multi245 cannot find the file. Load List also tells you how many files are present in the list.
Using DOS: You can also generate list files using the DOS DIR command. To create a list of the third set of dark frames having the file extension .P1/2/3 and to direct that list to an output file with the name DARK3.LST, at the DOS prompt type:
DIR C:\961203\DARK3*.FTS | SORT >DARK3.LST
You can edit this file in any word processor or text editor to delete files you do not want to process.
Multi245 allows you to examine a list of files and to delete files from that list. After you have edited a list, you can save the edited list.
VL [View List] displays the files in the current list. You can move backward or forward in the list, and skip to the beginning, middle, or end of the list. In addition, you can place any image on the left side of the screen to serve as a comparison for subsequent frames. By pressing the X key you can delete a name from the list. To exit the View List function, press the [esc] key.
Use this utility to determine which are the best images from an evening's work. After you have edited the list down to the very best, don't forget to save the list so that you can continue your processing on the very best images.
AL [Average List] creates an image that is the average of as many as 255 images in a list. Use it to average dark frames and flat-field frames. By averaging files you obtain a better signal-to-noise ratio in your flat-field or dark-frame than you could from a single file.
To run the Average List function, Multi245 needs to create a swap file. The default name for the swap file is E:\XXX.XXX. If at all possible, set up your computer with a RAM drive. If you cannot put the swap file on a RAM drive, put it on a fast hard drive. You can place the swap file on any drive or directory, but a RAM drive is much faster.
As it operates, the Average List routine loads and displays each frame. If you are creating flats or darks, watch carefully to be sure that nothing pathological gets into your averaged files. When all of the images have been averaged, the swap file is erased and the averaged image is saved. However, the averaged image also remains in memory, so examine it carefully to ensure that it is satisfactory for calibrating other images.
The Register List (RL) and Track-and-Stack (TS) commands are the heart and core of Multi245. These functions are very similar; they differ only in how they output their product. Register List (RL) registered images suitable for making movies; Track-and-Stack (TS) creates an image that is a registered blend of the images in the list.
When you start the Register List or Track-and-Stack functions, you will see this menu:
Track and Stack ## Images LoadPath: This is the path to your files. The default is the current LoadPath, and you should not change this since it is where your files are. Trial File: This is always the first file in the list of files. Do not change this unless you are prepared to do the tracking manually. The other files will be registered to a star you select in this image.
Once you have entered this information, processing begins. The trial file is calibrated and then scaled, and you are asked to identify the tracking star. Select a star that is fairly bright and well away from other stars. Press the S key to select it. If everything looks okay, answer "Y" when Multi245 asks if it should continue. If you answer "N," you'll be back to the Main Menu.
As Multi245 registers or track-and-stacks a list of images, it can automatically remove a dark frame and divide through by a flat-field frame. You must place those files in the same directory as the source files that you are processing. Enter a blank line tell Multi245 to skip this step. If Multi245 cannot find the dark frame or the flat-field frame, it will also skip the step. Before the list is processed, therefore, Multi245 processes the trial file. If for any reason this file is not processed correctly, answer "N" when Multi245 asks if it should continue.
Multi245 uses a process called "dark matching" to subtract the dark frame. This allow you to use dark frames whose integration time and temperature do not match the images you are shooting; that is, you can match 300-sec dark frames to 60-second images. When you supply the name of a dark frame, it will be automatically dark-matched to your images.
When you shoot images, always set the Drift Subtract to ON. This eliminates zero-point drift allows Dark Matching to determine the best possible fit between your raw images and the master dark. Dark frames taken weeks or months earlier can be matched to last night's images, although the best results still come when you shoot dark frames the same night. To make a master dark from a set of dark frames, average a list of dark frames.
To make a master flat field, average your flat brights to make an averaged flat bright frame, and average your flat darks to make an averaged flat dark frame, and then subtract the averaged flat dark from the averaged flat bright. This is the master flat field frame. All of the functions necessary to do this are built into Multi245.
The first time it loads a new dark frame, the Dark Match function creates a special calibration file. (You will see a progress bar as the file is built.) Thereafter, dark matching is very fast. During dark matching, the scaling coefficient is printed on the screen. The dark matching coefficient differs from the ratio of the integration times because of temperature drift in the camera. Dark matching compensates for this drift and eliminates its effects.
Multi245 can scale your images according to linear, gamma, gammalog, and log scaling laws. The scaling is exactly the same scaling found in CB245. On the scaling law line you must enter the scaling type and parameters. The default scaling law is:
GLGS 0.01 0.9999 0.45
This tells Multi245 to allow 1% of the pixels to saturate pure black but only allow 0.01% of the pixels to saturate pure white. The 0.45 is a parameter that controls how bright the image becomes. Values below .25 are almost always too dark, and those above .75 are almost always too bright.
Scaling is important because when you average more than five or six 12-bit Cookbook images, digital quantization rather than thermal noise limits the quality of the image. Scaling expands the range of values especially at the low end of the brightness scale, so that a 12-bit image can represent the full dynamic range of image brightness without the loss of image information.
The table below lists several scaling types with appropriate scaling command lines.
These parameters have the same effect as they do when the same scaling law appears in a CB245 script. Leaving the scaling law line blank causes Multi245 to skip brightness scaling.
You can align images automatically, semi-automatically, or manually, and you can register them either by whole pixels or by fractional pixels. This creates a total of six possibilities. When you issue the Register List command, you will see these options for aligning your images. Which you pick depends on how good the alignment is between the frames, and how you intend to use the output.
Here is a breakdown of the tracking options:
Semi-automatic tracking is tricky to use because the centroid algorithm may lock onto another star or even a few random pixels rather than ask for manual input, so treat its use as an "experiment."
Before you register a list of images, it's a good idea to run through them using View List (VL) to check how much the objects in the image move. If the frame-to-frame distances are two or three pixels, then you can use automatic alignment. If the distances are larger than five or six pixels between any two frames in the list, you must use manual alignment, or experiment with semiautomatic tracking. If the image moves between three and six pixels, you might be able to align the images automatically, but you will need to make several tries and experiment with different values for the track radius.
Real alignment makes exceptionally sharp star images look slightly soft because Multi245 resamples the pixels in the original image to move the image; that is, each new pixel is made up from several pixels in the old image. If your star images are between one and two pixels across, then the star images will be enlarged and softened. If the stars in the original are two to three pixels across, you will see no significant loss of sharpness. Bear in mind that thes differences are slight.
The Register List (RL) and Track-and-Stack List (TS) commands are the heart and core of Multi245. These functions are very similar; they differ only in how they output their product. Register List creates a new set of registered images suitable for making movies; Track-and-Stack List creates a single image that is the average of all the images in the list. Use Register List to create movies or sequences that show a changing phenomenon.
You can register images automatically, semi-automatically, or manually, and you can register them either by whole pixels or by fractional pixels. This creates a total of six possibilities. When you issue the Register List command, you will see these options for aligning your images. Which you pick depends on how good the alignment is between the frames, and how you intend to use the output.
After you have registered a list, use View List (VL) to inspect the new images. If the images have been aligned using the real alignment option, stars will appear stationary from one frame to the next. If have used an integer alignment, the stars will move a little, but the motion will be less than ±½ of a pixel in either axis. However, even this much jitter tends to be annoying, so movies look better if they're made with real alignment. If you have aligned a list of images so that you can blink them efficiently, then integer alignment preserves the full sharpness of the originals and therefore reaches slightly fainter stars.
To view a registered list of images as a movie, use the Make Movie (MM) command. This will create a set of .MOV files. To view the movie, use the Show Movie (SM) command. You will see your images projected on the monitor in rapid succession. To stop a movie, press the [end]key. The [pgup] and [pgdn] keys make the movie run faster and slower, respectively.
The Track-and-Stack List (TS) and Register List (RL) commands are very similar. They differ only in how they output their product. Track-and-Stack List creates a single image that is the average of all the images in the list; Register List creates a new set of registered images suitable for making a movie. Use Track-and-Stack to create ultra-deep-sky images with extremely long total exposure times.
Making ultra-deep-sky images with requires careful planning from the start. Basically, you need to take a large number of well-matched images and dark frames, calibrate them accurately, and composite them using Track-and-Stack into a single image. With Multi245 you can composite as many as 255 images into a single image.
Here are some Track&Stack tips:
After you have registered an image list, check the registration and quality of the images with the View List (VL) command. If everything appears to be as good as it can be, you can make a movie using the Make Movie (MM) command. This command converts the current list of images into .MOV files that can be loaded and displayed very rapidly. From a RAM drive or a fast hard drive, movies run 15 frames per second or faster.
You will be prompted for the SavePath and a five-letter name for the movie. Each of the movie images will be given this name plus a three-digit number starting with 000. The conversion process automatically clips or resamples the image from the 320x200 on the screen. When you make a movie, you are aksed "Resample?" If you answer N, the frame is clipped; if you answer Y, it is resampled.
You will see each frame appear as the movie is created. Once the movie is written on your hard drive, you may want to ZIP the files into a tidy package and archive it. You can put 22 .MOV files on a 3.5-inch high density floppy; when they have been ZIPped, you might squeeze a 50-frame movie onto a single floppy. The Iomega ZIP 100 drive holds about movie 1600 frames, but you must store them in directories containing no more than 511 frames.
Two- and three-frame "mini-movies" are a good way to blink for asteroids and comets. Longer movies can show continuous motion. Think about it—there's no limit to what you can do!
To view a Multi245 movie, enter the Show Movie (SM) command, and supply the LoadPath and the five-letter name of the movie. Multi245 movies run as a continuous loop, so you see the movie over and over continuously.
Alternatively, you use the Movie245 utility program provided with Multi245. To run a movie with the file prefix movie (on your drive as MOVIE000.MOV, MOVIE001.MOV, MOVIE002.MOV, etc., type this command line:
MOVIE245 movie loops
The parameter movie is the file prefix and loops is the number of times the movie will loop through. To make movies run faster, press the [pgup] key; to make them run more slowly, press the [pgdn] key. The [home] key restores the default running speed. To end the movie, press the [end] key.
From a hard drive, movies may run quite smoothly or very jerkily, depending on the speed of the hard drive, its degree of fragmentation, and the data transfer speed of the computer. Although it is possible, it makes no sense to run movies from a floppy. Movies run fastest and most evenly if you put them on a RAM drive. To create RAM drive on your computer, add the DOS RAMDRIVE.SYS command to your computer's CONFIG.SYS file for installation when the computer boots.
Because Multi245 can perform so many different tasks, the best way to learn to use is to use it. The sample files included on the distribution diskette allow you to create a 4-frame track-and- image. Experiment with these files: blink them against each other, make registered and unregistered movies, and so on. As you do this, you will become familiar with multi-image processing.
When you start shooting your own movies and ultra-deep-sky images, start modestly. Shoot sequences of eight or ten images with a corresponding number of darks. Forget about shooting flats until you're ready for setting up a light box or shooting the twilight sky.
CB245 shares many features with Multi245, and they have been designed for use together. You will find CB245 a useful tool for scaling deep-sky images and enhancing planetary images. However, Multi245 has been optimized for doing types of image processing that CB245 cannot, and vice versa. They make a great team.
The following files are included on the distribution diskette. The set consists of five frames from a 20-frame sequence of 60-second exposures with his Cookbook 245 CCD camera on a 6-inch f/5 Newtonian reflector. They show the Horsehead as it slowly drifts in the image area. Tracking is better is some frames than in others; you may wish to experiment compositing all the frames or only the best frames. The dark frame is provided, as is a composite of all 20 frames in the sequence.
These images are well enough tracked that you can register or track-and-stack them using the automatic track feature. Individual images show noise, but the noise reduction in the composite is substantial. Enjoy the learning process and experiment—you'll soon be shooting your own sequences!