Hi folks:
I'm struggling with a strange issue that has just cropped up after a few years of astrophotography with the same DSLR.
I've been using 360s (6-minute) exposures with my Canon 600D and the L-eXtreme filter @ ISO800. When I load the RAW files in RawDigger, I see minimal underexposed pixels in the red channel (blue and green are always adequately exposed). We're talking 5% or less underexposed.
I did a quick spot-check while imaging the veil nebula a few weeks back, and noticed that the red channel was now 20-30% underexposed. I figured that perhaps it was my first time imaging a target so close to zenith, and perhaps the level of atmosphere/LP had diminished to the point where I should start pushing my exposure lengths. I tried 7, 8, 10, 12 minutes. I managed to get it down to 7-8% underexposed at 10 minutes. 52% moon.
Tonight I'm shooting again, 28% moon, and exposure levels are dropping again! I had 20% underexposed at 10 minutes.
I checked my camera settings, I know I haven't doubled up on filters. What could be happening here? I'm concerned that my camera sensor is rapidly losing sensitivity, but perhaps this is par for the course when imaging closer to zenith, or with better conditions than the horrible hazy weather I've had this past spring? Has this ever happened to anyone before?
After I take flats tonight I'll take the camera off and check the filter to see if it's smudged or darkened. Any input would be appreciated! I've never heard of anyone having to expose for 12+ minutes @ ISO800 in Bortle 8.
CS,
Mark
I'm struggling with a strange issue that has just cropped up after a few years of astrophotography with the same DSLR.
I've been using 360s (6-minute) exposures with my Canon 600D and the L-eXtreme filter @ ISO800. When I load the RAW files in RawDigger, I see minimal underexposed pixels in the red channel (blue and green are always adequately exposed). We're talking 5% or less underexposed.
I did a quick spot-check while imaging the veil nebula a few weeks back, and noticed that the red channel was now 20-30% underexposed. I figured that perhaps it was my first time imaging a target so close to zenith, and perhaps the level of atmosphere/LP had diminished to the point where I should start pushing my exposure lengths. I tried 7, 8, 10, 12 minutes. I managed to get it down to 7-8% underexposed at 10 minutes. 52% moon.
Tonight I'm shooting again, 28% moon, and exposure levels are dropping again! I had 20% underexposed at 10 minutes.
I checked my camera settings, I know I haven't doubled up on filters. What could be happening here? I'm concerned that my camera sensor is rapidly losing sensitivity, but perhaps this is par for the course when imaging closer to zenith, or with better conditions than the horrible hazy weather I've had this past spring? Has this ever happened to anyone before?
After I take flats tonight I'll take the camera off and check the filter to see if it's smudged or darkened. Any input would be appreciated! I've never heard of anyone having to expose for 12+ minutes @ ISO800 in Bortle 8.
CS,
Mark
.