I attach two images. One is a raw integration and the other is calibrated (bias, dark flat). The I-flat was 120 seconds and looks OK (ca, 24000 ADU). The dark is 120 seconds scaled to the image. The image integration is 90 seconds. Airmass was OK (ca 1.2). Note the broad streaks. This streaking seems to be integration-dependent. 15 second integrations -- hardly noted. 10 second integrations almost absent. Observatory is in the suburbs in ca. 4th mag skies. Both B and V looked fine.
I am new to I-filters. Can someone on the forum give me some advice on this streaking? I am assuming that the photometry will be off, so I am not reporting any data with I-filters until I figure this out.