1. NEW BACKGROUND SUBTRACTION METHOD
Problem: How to subtract stars and the Milky Way from All-Sky Images

2. NEW BACKGROUND SUBTRACTION METHOD CONT.
Stars can be filtered out using a median filter or similar kernel based algorithms
Large saturated areas are not handled well by these methods
The Milky Way can not be removed by these kernel filters
Simultaneous off-band images are usually not available

3. NEW BACKGROUND SUBTRACTION METHOD CONT.
New procedure constructs an appropriate background image by remapping the off-band image to the desired time
Build up a data base of background images free of clouds and sunrise/sunset effects

4. NEW BACKGROUND SUBTRACTION METHOD CONT.

5. NEW BACKGROUND SUBTRACTION METHOD CONT.

6. NEW BACKGROUND SUBTRACTION METHOD CONT.
6300A image from El Leoncito

7. NEW BACKGROUND SUBTRACTION METHOD CONT.
Off-band (6444A) image

8. NEW BACKGROUND SUBTRACTION METHOD CONT.
Difference of two off-band images taken ~10 minutes apart

9. NEW BACKGROUND SUBTRACTION METHOD CONT.
Difference of 6300A image and time shifted (600 sec.) background image

10. NEW BACKGROUND SUBTRACTION METHOD CONT.
Median smoothed to reduce stars residuals

11. NEW BACKGROUND SUBTRACTION METHOD CONT.