M101 in LRGB
Posted: Thu Mar 28, 2019 1:34 am
I have mixed feelings about the quality of this image since I always strive to improve myself. What it's come down to is this: I've reached a plateau. I know what to do to make marginal improvements but the cost in time is high. So I present to you my last deep-sky image before retiring this camera from deep-sky duties: M101, a grand-design spiral galaxy.
My chief complaint is the noise level. In order to ensure correct star color rendering affected by saturation I reduced my normal exposure by half. As I've said many times in the past, this lowers your signal-to-noise ratio which you must make up with more stacking. Also, this time I did not go crazy capturing 50+ dark frames per half-degree Fahrenheit like I did with my landmark Bubble Nebula image seen here: viewtopic.php?f=16&t=1090
If I may, I want to address my critics who might say: Brian you talk a big game but you can't deliver. My reply to you is that this is a $250 uncooled camera that has served me well as a learning platform. Due to its inherent limitations I've learned what levers to pull to make positive things happen. In my opinion it is valuable. A lot of my knowledge comes from the friendships I've developed here in this forum and my membership to the American Association of Variable Star Observers (AAVSO) -- highly recommend. I await the delivery of my new camera with excitement.
Captured over two nights: 2019-03-13 and 2019-03-27
William Optics 71mm f/5.9
Altair 290M camera (uncooled)
Optolong LRGB Filters
Unitron Model 142 GEM
The Flatinator
Passive tracking with PEC
No active guiding
Gain 200 (1.74 e-/ADU, FWD: 7100e-, Read Noise: 1.55e-)
Offset: 25 ADU
Exposure: Multiple
Camera rotation: 1.8 deg E of N
Lum: 47x 25s
Red: 82x 30s
Green: 90x 30s
Blue: 76x 36s
Flats: 50x per channel
Darks: 20x per channel
Bias: 50x all channels
Total integration time: 151 minutes
Total time at telescope: 300 minutes
SharpCap 3.1.5219
APP 1.072
StarTools
EDIT: I updated the image here: viewtopic.php?f=16&t=1533&p=8053#p8053
My chief complaint is the noise level. In order to ensure correct star color rendering affected by saturation I reduced my normal exposure by half. As I've said many times in the past, this lowers your signal-to-noise ratio which you must make up with more stacking. Also, this time I did not go crazy capturing 50+ dark frames per half-degree Fahrenheit like I did with my landmark Bubble Nebula image seen here: viewtopic.php?f=16&t=1090
If I may, I want to address my critics who might say: Brian you talk a big game but you can't deliver. My reply to you is that this is a $250 uncooled camera that has served me well as a learning platform. Due to its inherent limitations I've learned what levers to pull to make positive things happen. In my opinion it is valuable. A lot of my knowledge comes from the friendships I've developed here in this forum and my membership to the American Association of Variable Star Observers (AAVSO) -- highly recommend. I await the delivery of my new camera with excitement.
Captured over two nights: 2019-03-13 and 2019-03-27
William Optics 71mm f/5.9
Altair 290M camera (uncooled)
Optolong LRGB Filters
Unitron Model 142 GEM
The Flatinator
Passive tracking with PEC
No active guiding
Gain 200 (1.74 e-/ADU, FWD: 7100e-, Read Noise: 1.55e-)
Offset: 25 ADU
Exposure: Multiple
Camera rotation: 1.8 deg E of N
Lum: 47x 25s
Red: 82x 30s
Green: 90x 30s
Blue: 76x 36s
Flats: 50x per channel
Darks: 20x per channel
Bias: 50x all channels
Total integration time: 151 minutes
Total time at telescope: 300 minutes
SharpCap 3.1.5219
APP 1.072
StarTools
EDIT: I updated the image here: viewtopic.php?f=16&t=1533&p=8053#p8053