Part 3I: Preparing the Data
****NOTE: Again, there is an accessibility gap, so you may need an assistant to help you with this part.
The last thing you did in part H was to download the data from Afterglow Access by clicking on a button that said “Download Batch Photometry Data”.
Where did this data go and how do we see it, understand it, and use it?
As of this writing, the answers depend on the device you are using. The 3:23 video below goes through the steps for a device which has Excel spreadsheets as an application.
If you do not have Excel, skip down to option #2 below the video.
If the device you are using has the spreadsheet application called Excel, it will automatically open in that depending on your user preferences. Or you may need to go to the download folder and click on the afterglow_photometry file. (Or follow the instructions on the video above)
1. If Excel is not present, the photometry data is downloaded as both a csv file (csv = comma separated values) and an xlsx file if your device contains that extension. These can both be found in your “Downloads” folder. This may be an “Accessibility GAP!” for you. If so, please ask for help in finding the “Downloads” folder.
2. Next, simply click on the afterglow photometry csv file (or xlsx file) in your Downloads folder. It will automatically open up in xlsx, a google extension for Excel spreadsheets (assuming you are using the Chrome browser). If it does not open, first open a google sheet. Then upload the csv file to the google sheet.
**NOTE: We will look at the data in depth in the next part. For now, just ignore every column that starts with “pm”, which stands for “proper motion”. Most of the other columns have something that will look familiar to you.
Whatever platform you use for your spreadsheet, we still need to add an additional, calculated column. Follow the instructions below to add a formula immediately to the right of the last column of data.
a) Click on row one of the NEW column to add a title. Label it delta mag, which stands for change in magnitude.
- this will be the magnitude difference (when both objects are in the same image) between the standard star and the asteroid. Recall, this is called the Differential Magnitude.
b) In row 2 of the NEW column, you will type a formula to find this difference. You are finding the mag difference between the standard star, whose mag is in row 3, and the asteroid, whose mag is in row 2. Follow these instructions:
- First type “=”.
- Next, locate the magnitude column on the spreadsheet (it is labeled “mag”). Then type the cell number of the 3rd row, which is the standard star, of the magnitude column (or you can just click on the cell to choose it).
- Now type the subtraction sign, “-“.
- Next will be the cell number of the 2nd row, which is the asteroid, of the magnitude column (or just click on that cell).
Summary: the formula reads: “=J3-J2” (the letter reflects the column mag is in. Your’s may be different). When you hit enter, the difference between the instrumental magnitude of the standard star in the 3rd row of mag, and the instrumental magnitude of the asteroid in 2nd row of mag, is calculated and entered into the cell.
c) You can copy this formula for the rest of the column, but you must copy the calculated cell and the blank cell below it. Paste this into the rest of the column. Delta mag should show up in every other row for a total of 8 numbers.
d) Save the spreadsheet to a place you can easily retireve it from.
Use SAS Graphics Accelerator
Let’s import the data to a different, more accessible platform, called SAS Graphics Accelerator.
The SAS Graphics Accelerator allows those with BVI conditions to explore and sonify data and graphs (Look up the SAS Institute for more information on the company).
Follow the steps below: (even if you would like to stay with the Excel sheet, try the Graphics Accelerator first).
A. The SAS Graphics Accelerator extension only works on the Chrome Browser, so please open Chrome if you are using a different browser.
B. Once in Chrome, use this link to get the extension from the Chrome Web Store:
C. Install the extension. It will show up on the right side of the search bar at the top of the Chrome browser as a symbol that looks like a script “S”..
** The 0:51 video shows how to import the data to the Graphics Accelerator. Or you may skip to the instructions below the video.
Instructions from VIdeo:
D. Click on this symbol on your chrome browser. A drop down menu shows up. Click on the second button down, “Laboratory”.
E. On the new Laboratory page, click on the word “Tables”. The next page has four buttons. Click on “Import Table”.
- the table you are importing will be the spreadsheet you saved that contains the downloaded photometry data – the one where you added the new column with the formula.
Once you find the table and select open, it shows up immediately on a page titled: “Prepare Table”.
The first button available is “Save to Laboratory”, with “Cancel” next to that. If you are happy with the name that is listed below the “Save to Laboratory” button, click that button. It will take you to a page called “Table:with the name you choose.
There are 5-7 buttons at the top of this page. We will ignore those for now. Move down the page to the table. Notice you can move across the columns easily.
The meaning of some of this data is explained in the next part.