In The Beginning
Have you ever wondered how or if you could capture Star Images? Well Fighting For Rights and I have spent the last couple of weeks doing just that exploring the capabilities of her new camera. Pictured to the right is my old simple Point and Shoot Sony and below is an image that I was able to capture with it.
I chose to provide links as opposed to showing those images in this article for 2 reasons. First the small format here does not do the image justice and second to save space. The original image is not much to look at but here is the Exposure Data which is important.
- Exposure Time - 2 seconds
- ISO Speed - ISO-100
- F-Number - f/2.8
- Date Picture Taken - 10/3/2014 12:01 AM
What is important about these settings is that this is the longest shutter speed, the fastest ISO and the widest lens opening that my camera will provide and was achieved by choosing a Night time Scene setting. This is not much compared to what the newer cameras offer as options. It is important to note that a tripod and the camera's delay timer were used to avoid camera movement during the exposure. This is how one gets to know their camera with the attention given most to a long exposure time. The longer the better to a point and the key is experimenting and the conditions of the site where the images are taken.
Bottom line here is to illustrate that with just a minimal 2 second exposure I was able to capture more stars than I could see by eye under very good conditions. What comes next is the simple processing of the image that will show the collected data on our screens for the best view.
Leb's Digital Darkroom
Now this is where Part II of Astrophotography takes place and the purpose here is to keep it simple. I want to provide an introduction to image adjustment and to point to the tool that allows one to make the primary adjustment in all astro images. To do this there are many videos available on YouTube. I have one in mind from Cyanogen.com the makers of Maxim DL which is observatory grade astrophotography software and I happen to be very familiar with a mini version that was supplied with one of my CCD cameras. I do want to make it very clear at this point that if one has image processing software; one already has the tools needed. What we will learn here is how to Stretch the image.
As in all new things there will be new vocabulary and here possible mention of unheard of before image formats. What I hope the viewer comes away with is the simplicity of the actual image adjustment and that the amount of adjustment is not set in stone. Then we will look at various presentations of the same tool as it appears in other software.
After viewing the video the Screen Stretch examples to the right should look familiar. In the first 2 examples notice that they are the actual settings produced by the Astro Image above. The third example is the histogram of the Sony camera image above and is shown to demonstrate a normal properly exposed image.
The adjustments shown in the second example have created an image on the screen that has brought a lot more stars out of the dark and at the same time removed noise and graininess to maintain a dark almost black background, enough for my liking. The actual "Stretch" comes from when I make these changes permanent by saving the new JPEG image. The portion of the histogram between the red and green carets becomes the new histogram with a range of 0 to 255. Note here that I always preserve the original.
Now this set up in Maxim DL was created for primarily one purpose, quickly adjusting astro images and this Screen Stretch window to the right is actually just a portion of what would be found in standard image editing software like Paint Shop Pro or Photo Shop and there it is called the Histogram Adjustment window.
Pictured to the right is the Histogram Adjustment window from Paint Shop Pro. The 2 carets or sliders of importance there are colored dark grey and white. Notice that the numbers entered into the Low and High boxes match the numbers in the Minimum and Maximum boxes of the second example Screen Stretch window. Both programs produce the same image with the same results and clicking OK does the Stretch so the image is ready to save. There are more Buzzers and Bells on that window to play with but we are just dealing with the basics here. Feel free to experiment. This window will be very similar in the other image editors.
To the right here is the Histogram adjustment window in Photo Shop and it is called Levels.
That's it, that is how to Stretch the image. Basically if you think of it like a Dimmer switch for a light. We use it to turn up the lights and at the same time a second Dimmer to turn off the darker noise.
Two steps, that's enough to get started. Take the picture and then adjust it, the results will be amazing and of course it gets easier with practice. Certainly this can be taken to much higher levels but every journey starts with the first steps. A Sky Chart is handy and then of course labeling the images is a nice extra and a great way to learn the names of the visible stars and constellations.
One thing of interest about that image up there that I have displayed is that the Andromeda Galaxy is in that image although not visible. It is located just to the left and above where I labeled the Constellation Andromeda. With a few more seconds of exposure it will be visible and I'm willing to bet that Fighting For Rights will be the one to show it :o)