comet neowise

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BurnsideBob
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Re: comet neowise

Post by BurnsideBob » July 26th, 2020, 9:54 am

ChromaKey,

I don't have the patience to do the post processing you are doing. Maybe you could get clearer, less grainy images with that kind of effort. I'm not blending images, as the one shot with both crescent moon and the comet sure shows.

My approach is quick and dirty. On my computer's default photo viewer for raw files, I increase color and brightness, then save as a .jpg. I then open the .jpg in the Photo Viewer bundled with Microsoft Office. In that I adjust contrast and color focusing on midpoint value.

Years ago I had Photoshop 5, which I found rather time consuming to use. I suppose you could set some parameter so that if the brightness value of a pixel was below a threshold, it would be rewritten as no brightness. This would be contrast on steroids, but would preserve relative brightness between pixels above the threshold and would suppress graininess.

You are orbiting above us ground pounders. :lol:

BurnsideBob
I keep making protein shakes but they always turn out like margaritas.

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markesc
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Re: comet neowise

Post by markesc » July 27th, 2020, 9:37 am

FWIW, If you have a tripod + mirror lockup + 2 second shutter delay, I had decent results @ 400mm F5.6, 5 seconds, ISO 800, this using a Canon 80d. A newer camera may allow a higher ISO and maybe 2-3 seconds with better results. This comet was just really dim, so any light pollution = even bigger challenge. If you can shoot the file in a raw format, then you have a little more information to work with later on vs. in camera .jpg compression which is all over the map depending upon the camera model/settings/sensor.

Either way, it was neat to see using the Binoculars and enjoy time sharing with friends n family :mrgreen:

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BurnsideBob
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Re: comet neowise

Post by BurnsideBob » July 27th, 2020, 4:31 pm

markesc wrote:
July 27th, 2020, 9:37 am
Either way, it was neat to see :mrgreen:
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.

IMG_5091 (4).jpg

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!

IMG_5091 (5).jpg

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.

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markesc
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Re: comet neowise

Post by markesc » July 31st, 2020, 10:59 am

I think you did great here!

It's a tough challenge because the comet is just really really dim.

As far as the calculations for star trails / avoiding them, you're lightyears beyond me! As far as focus goes, that's tough, one work around is if your camera has a live view option, you can try that, set the focal length where you plan to shoot, and then like you mentioned, find a bright distant light, and try manually focusing. Annoyingly you may have to boost the ISO temporarily really high during this process, then drop it back down once you're done with live view and ready to shoot the actual photo sequence. It's tedious and can be annoying at night, so I've found lenses that have a dial that shows the infinity symbol as nice to have for a starting point.

There are some cheap lenses some use that yield great results for galaxy photos:

https://theplanets.org/best-lens-for-astrophotography/ (some of them are manual focus only, so it's one of those live view pre-focus/get there early routines, then tape down the focus wheel before it gets too dark). I don't have any personal experience with any of them.

This page breaks them down for crop vs. full frame:

https://www.slrlounge.com/best-lens-for-milky-way/

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Re: comet neowise

Post by justpeachy » July 31st, 2020, 3:05 pm

Saw the comet from the Up Up Lookout in the Lolo National Forest on July 17, 18, and 19. Totally lucked out with the timing. I obviously had no idea about the comet when I booked the lookout back in January!

Image

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BurnsideBob
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Re: comet neowise

Post by BurnsideBob » July 31st, 2020, 8:51 pm

justpeachy, that is a peach of a photo! The splits in the comet tail are very visible in your image. Looks like you had less light pollution at the look out and I'm envious you caught the tail splits.


Chris, thanks for the articles on good glass. Can't really afford good new stuff, but I could spring for a Canon FD mount to Canon EOS mount adapter. Then I could use my old Canon FD lenses on the Rebel T4i body.

The Perseid meteor shower is coming up. Here's a Nikon oriented article that explains how to set up exposure.

https://www.nikonusa.com/en/learn-and-e ... owers.html

BurnsideBob
I keep making protein shakes but they always turn out like margaritas.

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