Astrometry with Canopus

Video Tutorials

We have made these instructions available as video tutorials. If you would rather watch a video tutorial rather than read these instructions, sequentially follow the video links below.

Setup Procedure

This page contains the written instructions for asteroid astrometry using MPC Canopus.

Step 1. Verify that you have and are using a configuration for the LONEOS telescope.

Procedure Sub-steps Expected Result
This step assumes MPO Canopus has been invoked and is currently running on your computer.

Many of the steps described in this web page are extremely brief and un-enlightening. I suggest you keep a copy of the MPO Canopus Reference Guide handy so you can see the larger picture.

From the "File" drop down menu, select "Configuration".
The "Configuration Settings" dialog box appears.
Under the "General" tab, verify the the "Profile" name corresponds to the LONEOS telescope. There are three possibilities here.

The LONEOS profile may already be selected. If so, go immediately to Step 3.

If you already have a profile for the LONEOS telescope, select it and depress the "OK" button. Then go to Step 3.

If you do not have a profile for the LONEOS telescope you must create it. The instructions for creation are presented in Step 2.
All the of possibilities simply lead to another procedure so there are no expected results.

Step 2. If you do not have a LONEOS telescope profile in "Configuration Settings", you must create it. If you have a LONEOS profile, you should have already picked it, so you may skip this step.

Procedure Sub-steps Expected Result
Starting with the "General" tab of the "Configuration Settings" dialogue box, make each of the tabs look like the images to the right. When all the tabs have been matched, depress the "OK" button.

Notice that the "OBS" and "MEA" fields are empty in the MPC tab. You will supply those names in the next step.

The "CON1" field of the "MPC" tab is not completely visible in the picture. It should be "Bruce Koehn, Lowell Observatory, 1400 West Mars Hill Road,".

Step 3. Modify the profile so that it contins correct names for the measurer and observer.

Procedure Sub-steps Expected Result
Select the "MPC" tab of the "Configuration Settings" dialog box. The "MPC" tab appear in the dialog box.
Then Modify the "OBS" and "MEA" fields in the "MPC" tab so they contain the observer's name and your name respectively. You can find the observers name in the header of any of the FITS images you are using. The associated FITS keyword is OBSERVER. Use the MPC nameing convention of initial of first name, initial of second name, and last name. There are periods after each initial and one space between them. There is a space between the period of the second initial and the last name. When you have entered both names, depress the "OK" button at the bottom of the window. You have set the proper observer and measurer in the LONEOS profile and the "Configuration Settings" dialog box should disappear.

Step 4. Load the first image, set the measuring aperture, and calulate the astrometric solution for the image.

Procedure Sub-steps Expected Result
From the "Image" drop down menu at the top of the Canopus window, select "Open". An "Open Image File" dialog box appears.
Select the first of the four images that you are to examine. Depress the open button. The dialog box disappears and the selected image appears in the Canopus window.
Invoke the "magnifier" by simultaneously depressing the Ctrl, Shift, and 4 keys. The magnifier appears. As you run the mouse pointer over the image, the area near the mouse pointer appears in the magnifier window but displayed in a magnified format. Also you will see three rings in the magnifier. These rings represent the photometric/astrometric aperture used to measure the stars.
Depress the "Aperature" button on the button bar near the top of the Canopus window. The "Aperture Settings" window appears.
For LONEOS images, we find that a photometric aperture of 7 pixels, a dead space of 9 pixels and a sky annulus of 11 pixels width works well. The same is true for comparison and astrometry apertures. More simply, make your Aperture Settings match those in the image to the right. Then depress the OK button.

Canopus records all the aperture settings are recorded and then removes the "Aperture Setting" window.
From the "Image" drop down menu at the top of the Canopus window, select "Auto Match/Measure".

If Canopus does not behave as described in the "Expected Results", go back to the File -> Configuration dialog box and select the "Charting" tab. Verify that "Reverse E/W" has been selected. If not, select it and then try "Auto Match/Measure" again. If you still have problems, you can try to "Generate Manual Chart" found just below "Auto Match/Measure". Get the instructions for this procedure from the Canopus manual. If you still have problems, seek advice.
Your computer should spend several seconds calculating and then it should display a star map on the left side of the window that generally matches the image on the right side of the window. Then it should draw circles around about 50 of the stars in the image and put numbers beside corresponding stars on the star map. Finally it should put up a small window, "Photometry Residuals", which lists various paramaters associated with each of the circled stars and tells how well the stars' positions match the stars' calculated positions.
Get rid of the "Photometry Residuals" window by clicking on the red "X" in the upper right corner of the "Photometry Residual" window. The window disappears.
Select the "Show Reductions Page" icon, fourth from the left at the top of the Canopus window. The "Reductions" page appears.
In order to improve the quality of the astrometric "fit" you must remove all the selected stars that do not fit well. These stars typically have a large "proper motion" and their position in the image is considerably different than when the star catalog was made (or some other type of error). I suggest that you look at the values in the "RARes" and "DCRes" columns. (These columns are the RA residuals and the DEC residuals.) Omit all the stars that have a green, blue, or red background. Canopus has identified the colored residuals as unusually large. If any of the remaining values exceeds |0.20| arcsec, then it should be omited from consideration. You can omit a star by removing the "X" in the "U" column of the table.

Canopus will automatically recalculate the residuals each time you remove a star. Therefore, as you remove stars, some stars that were within error tolerance earlier will now be out of tolerance. You will have to go through the list several times to get a good set of stars. You should generally omit the stars with the largest residuals first.
All the selected stars will have residual values (absolute value) for both RA and Dec less than 0.20 arcsec. You should have at least 30 to 40 stars left. If not, you may have to start all over and use a value slightly larger than 0.20 arcsec as your limiting error.

If you would rather watch a video tutorial of the information below (most of step 5) follow this link. You can find a video tutorial of the rest of step 5 at this link.

Step 5. Identify the asteroids on the picture and save the data. Canopus will allow the user to identify and save data for only a single asteroid at a time so you will have to repeat this step for each asteroid on each frame. Toward the end of this procedure, you can gather all the saved data together and make a single larger report containing the data for all the asteroids.

Procedure Sub-steps Expected Result
From DS9, select the first image in the set of four. Identify an asteroid you want to include in your report. (Eventually, you will put all the asteroids in your report so pick them in some memorable sequence.) Select the "Show Measurements Page" icon in the icon button bar at the top of the Canopus page. The image should re-appear. Identify the same asteroid in the Canopus image. Left click the asteroid. HINT: The DS9 and Canopus images might not have the same orientation. I have found that by selecting the DS9 "Zoom" drop down menu and selecting the "Invert Y" menu item generally puts things in the same orientation.

Others have found that "Invert X" works.

The orientation options are a little non-intuitive, at least to me. Once you catch the paradigm, the options work as expected. Spend a little time here so you are not confused.
A "bulls eye" icon surrounds the asteroid on the Canopus window.
Right click the asteroid on the Canopus window. A menu appears.
From the magic window, select "Set Asteroid Centroid". The menu disappears and some other magic occurs which you will see in the next step.
Select the "Show Reductions Page" icon from the icon button bar at the top of the Canopus page. You will again see all the stars you picked for the astrometric solution. More importantly, in the lower left part of the page, you will see the coordinates of the asteroid you just identified.
If you know the name of the asteroid, (it should be circled with a green circle in the DS9 window) go to the right side of the Canopus page and under "Calculations" and "Table", select MPC. If the asteroid is numbered, enter its number in the "Number" field and ignore the "Name" field. If it is not numbered, ignore the "Number" field and put its name in the "Name" field. Then depress the "Recompute" button below.

If you don't know the asteroid name, (it should be circled with a red circle in the DS9 window) skip this step. There will, of course, be no expected results.
If you entered the number and/or the name of the asteroid in Canopus, its name will appear in the Object fields in the lower left part of the window. What you really want to see are the values in the Calc fields and the M-C fields. The M-C fields show the difference between your measured positions and the calculated position in both RA and Dec. These values should be small for numbered asteroids, i.e., less than 0.5 arcsec.
Depress the "Save" button at the bottom of the Canopus page. The "Save Astrometry File" dialog box appears.
Devise a file name that will serve to identify all the asteroid photometry files you have found on this set of images and insert that name as a prefix to the File name: shown at the bottom of the dialog box. You should also increment the file name index as necessary. The file names should probably all be the same except for the index. Then depress the "Save" button. The astrometric information you just generated is now saved in the file whose name you just specified.
Repeat the preceeding steps for each asteroid on the image (that is, perform all the appropriate parts of Step 5.) and then repeat the preceeding steps for each of the remaining images (that is, go back to Step 4 and repeat all the appropriate parts for each of the other images). This is getting tedious. If you have 10 asteroids on each of four images, you will have saved 40 files with astrometric information. Be careful. This is not for the faint of heart.
Now you are ready to generate the MPC report. At the bottom of the Canopus page, depress the "MPC" button. A warning message will appear. It indicates that there is an error in the catalog specified in the report.
Depress the ignore button. We will fix the problem later. The warning message disappears and the "Save E-Mail File" dialog box appears.
Create a new file name. The file name will point to a file containing an MPC report suitable for emailing to the Minor Planet Center. Be careful not to overwrite an existing report. Then depress the "Save" button. (I always use the default directories for these things. It saves a lot of hassle because Canoups already knows what the default directores are named.) The "Select AST Files" dialog box appears.
From the "Select AST Files" dialog box, select all the AST files that you just created. If there were 10 asteroids on each of 4 frames, there will be 40 of them. Use one the standard MS Windows standard selection methods. Then depress the "OK" button. The "Select AST Files" dialog box disappears and an edit window appears where you can make changes to the MPC report. Normally you will not have to make any changes. The MPC report file should now exist exist and you can simply close the editor. HOORAY. You are done with the astrometry!