markesc wrote: ↑July 27th, 2020, 9:37 am
Either way, it was neat to see
I agree Chris! The comet was a wonderful surprise.
Chris, I wasn't sure you were referring to my post applauding ChromaKey for his tenacity in manipulating his image.
I'm guessing folks reading this thread have an interest in comet photography and have wondered how they could shoot their own photos--so I'm going to dither on in the hopes that what I say may help them the next time a comet comes calling. I don't want to represent I really know anything--Comet Neowise was my first somewhat successful night sky photography foray.
At the hardware level, I was using a Canon Rebel T4i DSLR with the kit 18-135 mm zoom, which has an aperture range of 3.5 to 5.6. This camera does not have a full frame sensor, so you multiply the focal length by 1.6 to get the effective focal length. If you divide the effective focal length into 500mm, you get the maximum time exposure before star trailing becomes uber noticeable. So for my lense the effective focal length varied from approx 20 mm to 200 mm, and the max time exposure before star trailing was 25 seconds to 2.5 seconds at max zoom.
I also tried a fixed focus ("Prime") f 2.8 100 mm macro lense, but most of the time I wanted to capture more of the star field or to really zoom in, so the 100 mm macro only got outside a couple nights.
Like you, I used a tripod and shot in raw (.CR2) at iso 800 using a 2 second shutter delay. I was going to experiment with 1600 and 3200 iso, but somehow, with all the excitement, never got around to playing with that variable. In part because higher iso would probably mean more grain, which was already a problem in post processing.
I varied exposure time from 3 seconds to 30 seconds at all different focal lengths. The focal length was a nightmare, as the lense manual focus ring no longer works--too many hiking trips. So whenever I changed focal length I had to set autofocus to "on", focus on a distant illuminated target, switch autofocus to "off", and then reset on my target.
I also tried an older camera, a Canon PowerShot SX30 IS. I took better photos of the 2017 Eclipse with this camera so wanted to see if I could get a good comet image. I could, but I found the inability to shoot in raw limiting, and had more trouble getting the little camera to focus (auto focus only) in the dark.
To conclude the hardware bit, I took a lot of images but the vast majority were out of focus, star trailed, or had other operator errors.
Now for post image capture processing. Again, I'm a rank amateur, but post processing is where an image really comes to life.
This capture was at 20 seconds at, maybe 50 mm focal length. The changes to this version are 1) file type has been converted from .CR2 to .jpg (file compressed from 20.6 MP to 5.74 MP) and 2) .jpg image size has been changed to approx 1600 x 900 pixels.
This is the same image with different post processing steps. In my computer's default editor for .CR2 (raw) images, I've generously enhanced brightness and color. I then selected "Save Copy", which auto saves a .jpg version without erasing the original .CR2 file. I then opened the .jpg with Microsoft Office 2010 where I've made additional adjustments to color, brightness, and contrast before changing the image size to approx 1600 x 900. After reducing the size I hit the "auto correct" button, with the result you see here. While the image is grainy, it is colorful!
I'm all excited about capturing the milky way over some awesome scene. Gonna have to hike somewhere soon. Hope you all are excited about shooting the night sky, too.
BurnsideBob
I keep making protein shakes but they always turn out like margaritas.
