Astro Photo

Astro Photography Techniques

This article was written using the G7
Last Updated: 1 November 2007
Article written by: Mikael Fabrin

Are you amazed by the wonderful pictures of star trails that sometimes appears in magazines and on the internet? Would you like to take such photos? Maybe you think, "Well, of course, but that is only possible for people with big bucks." That is not true. Astrophotography is within your reach if you ’just’ own a G7.

It might be much easier to obtain price warding pictures with an expensive DSLR. But if you lower your expectations, astrophotography with the G7, can be a rewarding experience. Your friends and family will most certainly be impressed by your achievements. In this article I will only deal with star trail shooting, the easy kind of astrophotography. I will bring into focus a special technique that will allow you to take a lot pictures and merge them together in a special freeware program or in Photoshop.

The Technique

To take a picture like these (picture 1-3), you pretty much have to use all the creative functions of the G7. First you have to turn off the image stabilizer function. Paramount to a good result is using the manual mode to set a relatively short exposure time.

If you like to shoot right after sundown, then 6 sec will be sufficient, but if the sky is really dark then 8-10 sec. will give a more pleasing result. Try to use the largest aperture f2,8 and ISO 800 to take in as much light as possible. One drawback using the G7 is the noise reduction process which the camera applies when the shutter speed is 1.3 seconds or lower.

I have found that using a short exposure time and medium compression (I recommend M1 and Superfine), minimizes the noise reduction process. It is important that the exposure time is as short as possible. Even pauses of 10 seconds will be visible in the picture, as there will be gaps in the star trails. Another thing to remember is to use manual focus and set it to infinitely.

The advantage of using the manual focus is that the ’focus lock’ is still effective after the picture is taken. That allows you to capture a second image with the same focus.

Unfortunately continuous shooting is not possible due to the noise reduction process. This is another drawback using the G7. One has to take a roundabout. Set the camera to custom timer. Go to the rec. menu and set the delay time between each shot to 1 sec. and the number of shoots to 10 pictures. It is only recently I discovered this method, a true magic bullet. Before I had to press the shutter button more than 150 times when I wanted to shoot star trails, now I only do it 15 times. It really reduces the risk of accidentally pushing the camera.

Lastly, set the metering mode to evaluative and white balance to auto. All you have to do now is safe your settings to the custom mode. Go to the Rec. menu, find the ‘save setting’ option, and choose which custom mode (C1 og C2) you want to use, now the camera remembers all the settings. That is an impressive feature of the G7. But before you begin to shoot star trails, you have to select a good location.

On the Location

Choose a location with a nice view to the sky, and use the wide end of the lens. You want to cover as much of the sky as possible. Most astro photographers make sure that there is an interesting thing in the foreground as a contrast to the star trails. It could be a house, some trees or mountain peeks. I found that moderate light from the moon can create an interesting effect. (See picture 1). The period when the moon is waxing or on the wane could be an opportune time. Do not despair if you live in an area with moderate light pollution. (Se picture 2) Taking a lot of pictures with a short exposure time and merging them using a special program minimizes the effects of light pollution. An interesting subject for those who live in the northern hemisphere, could be stars revolving around the North Star. (See picture 3) Look for the Little Dipper in the constellation little bear. It is the star at the end of the handle of the Little Dipper. If you are lucky you might even capture a shooting star! Finally, place the camera on a tripod and set the custom mode to C1 or C2 according to your previous choice. To conserve battery power I recommend that you turn of the screen by pressing the display button twice. Now it is all about taking as many pictures as possible. For an impressive picture, you want to take at least 150-200 frames or pictures (covering about 1. hour). Picture nr. 3 consists of 264 frames.

The Post Processing




		When I return home, I upload the pictures from the camera and insert them in this freeware program at the following web address: http://www.startrails.de/html/software.html The program is very easy to use. If you use Photoshop you may find the following link interesting http://www.schursastrophotography.com/software/photoshop/startrails.html When the program have created the star trail picture, I occasionally remove some of the noise using Neat Image, (note that picture nr. 1-3 is unaltered due to the fact that the noise reduction would have blurred some of the faint star trails and details in the foreground) and afterward I do some adjustment using Photoshop elements 5.0. Mostly I ad some more contrast and lower the light intensity.

	Picture of the Moon The only celestial bodies I have been able to shoot beside stars, is the moon. I set the metering mode to ‘spot’ in Functions Menu. It is important, because you will only want to meter the light of the moon. In that way the highlight in the moon will not be blown out. Remember to set manual focus to infinity. I use ISO 80 to be able to control the noise. Finally I set the exposure compensation to –1 1/2, to draw out as much detail in the moon as possible. In post processing I have enlarged the photo 100 percent, and cropped it. Using the Zoombrowser I have adjusted the light to –19, saturation to – 0, contrast to +5. As the final touch I sharpened the image with USM: Amount: 123, Radius 0,2, Threshold: 1. A Step Further While you are sitting and gazing at the starry sky, a lot questions will properly pop up in your mind. Astrophotography has for many been a gateway to the intriguing world of astronomy. It is my hope that it will whet you appetite and arouse a wish to learn more about the stars and the universe.