I've been working on that today as it was cloudy out.
Here's a wide field looking photo from my wide field image (purple tinted) which I'm hoping to include and have in this months newsletter.
This was simple the wide field image cropped to look longer, more like a panoramic photo of the sunset.
The image was overly processed perhaps a bit, with a kind of experimental hit and miss setting using Nebulosity. I was trying to use Nebulosity (a program on the Macintosh) to get rid of hot spots that might be on the exposure, hot spots on the sensor or hot pixels can be removed with a "dark frame" processing or with "noise reduction" set to on for many digital cameras. I didn't have my noise reduction set to on when I took the photo, so I needed to get a dark frame. That dark frame, is supposed to be "at the same setting and temperature that the photo was taken at". I forgot to take dark frames when I took photos at Island Lake, so I was missing dark frames.
Dark frames are only good for the same camera, you can't use dark frames from one camera and process them with photos from a different camera. A dark frame is a frame of a dark image, like a photo taken with the lens cover on the camera, totally dark. Pixel dots on the image that are "hot" will show up in a dark frame. They are defective image sensors that glow hot due to defects that are in the camera sensor or develop as the sensor degrades over time. Some spots may permanently glow and look like they are white or red dots, usually they seem to be most noticed when they are red. They will always be on the same location. So a dark frame is a mapping of the bad parts of your camera sensor. You can take those dark frames and subtract the bad spots and fill those in with information from the area right next to the glowing pixels. This may be done automatically using programs that are designed primarily for astronomers, they do "dark frame" processing in the software and will remove the glowing hot pixels which may look like a red star, but are false stars or spots on the image.
Well that should be enough of an explanation. In Nebulosity I can remove dark frame noise. I tried to do this, but I'm not familiar with the Nebulosity interface, because I rarely use that program. I've used it in the past. So I took a RAW camera image and brought it into Nebulosity. I wanted to process the dark frame. I used dark frame subtraction from a dark frame that I took afterwards. I knew the frame would be fairly good, because I was able to look at the Metadata using a viewer called EXIF viewer off the internet. And I used this viewer to determine the temperature of the camera when Ken and I were out taking the photos of the comet. The camera was 2 degrees C. Or just above freezing. I tried to take dark frames by putting the camera outside this week but I couldn't get the camera chilled enough to get a dark frame photo that was cold enough. So I wrapped the camera in a clean, used bread bag and put the camera in my freezer in the kitchen. I set the camera to take time lapsed stills at the same frame rate and ISO setting inside my freezer. it was sitting inside with the ice cream and other stuff in my freezer. I reviewed the images, and found some 2 degree dark frames.
In Nebulosity I tried to apply a dark frame. I'm only working with one still "light frame" or exposure, so I only used one dark frame. I applied it, I really didn't check the results to carefully, maybe it worked, maybe it didn't totally work. I may review it later and try it again.
The RAW image looked really dark in nebulosity. So I tried to bring up the brightness using DDL features in Nebulosity. I like the power of Nebulosity, but the sliders and ways to vary the few settings inside it seem difficult to learn and at times are just a long frustrating trial and error. The image looked better, but still quite dark, and when I exported it, the image looked really dark. So I took the TIFF image exported from Nebulosity and opened it in Photoshop CS6. I tweaked the image some. I overexposed it a bit using curves and this caused some of the high levels of the image to be clipped. An over-exposure. It gave it a grainy glowing kind of look. I liked the look. It almost looked like a painting for a light box or something. With the light from the sunset being behind it.
I decided to use that and not try to look for a perfect rendition of the sky color. Nebulosity had colored the object and changed the tint to give it a purple cast or tint. I didn't mind that change, it was probably something I did with the DDL setting. I left that and exported that as a TIFF from photoshop. It almost looked a bit like a painting. I liked the detail of the clouds.
I tried to see if I could remove some of any noise it might have and clear up a bit of the grain. A bit of glowing grain, likely bright over saturated pixels existed in the image. I wanted to see if I could remove some of this grain using Neat Image Pro. I have the "stand alone version" because I bought it before I purchased Photoshop. So I played with Neat Image Pro, but the photo almost looked as good with the grain as with some of the changes I did with the noise reduction filter. The noise reduction filters didn't seem to do much, but when you zoomed in they gave it a painted fractal feel, almost like a surrealistic fractal pattern in some areas. It still looked good when at normal wide views, without a lot of zooming into details.
I could use either image. The Neat Image reduced version at normal wide views looks just as good. It might look really nice like some kind of art piece if it was blown up big and printed.
I cropped this a bit and had a closer version of the image. I played a bit with a label.
I also took one of the two images, and cropped it chopping off the top and bottom giving it a panoramic like feel. This might look good as some kind of long header or footer. This was what I eventually used as a footer on page one of my submission to Star Stuff. It probably won't print very well, but it will look great on a high resolution PDF for online viewing.
In any event, here is a copy of that cropped photo, after being processed with Nebulosity, Photoshop, Preview and possibly Neat Image. If you zoom in and see no fractal patterns it's the photoshop version before Neat Image "reduced" the noise. I can't remember which one I'm using in this post.
(click on the image below to see a larger version.) (c) Greg Knekleian
It's a lot of fun to play around with images you've taken. There's a lot to learn from imagers and astronomy imagers have a lot of information and spend a ton of time processing their photos.
I'm really just a moderately new beginner with astrophotography. Many in the group have better equipment skills and knowledge. There's a lot to learn out there.
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