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Friday March 24th 2017

Posts Tagged ‘point-and-shoot camera’

Astrophotography – Without a Telescope

Milky Way, Credit: Ralph Clements

By Ralph O. Clements

When I was invited to write about this subject for Astronomysource.com, I must say I was flattered and a bit flabbergasted too, as I do not consider myself an expert on the subject, nor a writer by any means, but just a guy who likes to go out at night and take pictures of the sky. I stumbled into this hobby when my wife brought home an old 4” Meade reflector telescope with a manual equatorial mount from a yard sale that she paid $60 for.

I took that thing out in the country and set it up (completely wrong, I now understand) and as darkness approached, held my point-and-shoot camera up to the eyepiece and took a picture of Venus. Well, now that was very interesting…it was certainly not a very good photo and I have learned it is hard to get a good one of Venus, but I could tell it was not a star, it was not round but had a semi-circular shape. Wow! I took a picture of another planet! That got the gears turning in my head and I just had to do more….I mean who would think I could take a picture of another planet, with a point-n-shoot camera and an old yard sale telescope?

“Camera Only” Images

I do take images with newer telescopes and a decent equatorial mount which I have acquired since. Imaging galaxies and nebulae is an ongoing goal and interest, but I have learned that it is time consuming, tedious and has a fairly steep learning curve. My view of the sky at home is very limited. So for the time it takes to drive out to the country and get all that gear set up and working, I am limited to weekends and then only weekends when the sky is clear. Since clarity of skies does not always happen on Friday or Saturday night, I often image without the telescopes at all. All the tips and advice offered here is just what I have learned and I expect others may have better ways of doing things.

Equipment

My research indicated that Canon cameras are preferred for astrophotography and the T1i is what I use for everything. I also have an older Nikon DLSR with two lenses, a 180mm fixed focal length and a 75-300mm zoom, for which I bought a Canon adaptor, but the 18-55mm “kit lens” that came with the Canon is what I use most often.

If you read up on astronomy and astrophotography equipment you will note it is often said that the mount is every bit as important as the telescope. My camera tripod is my mount and I fully agree that a sturdy tripod is a must. I am fortunate to use a tall Berlebach tripod with hardwood legs. The cheap aluminum department store tripods are not stable enough.

Figure 1: Orion at Peaks of Otter, Credit: Ralph Clements

Widefield & Star Trails

Camera only astrophotos with a static tripod fall into these three general categories:

Widefield – Single Shot

These include what would be considered “scenic” or “landscapes” in daytime photography, that is, including some portion of the Earth, as well as constellations and shot of the Moon (See Figure 1). I try to shoot as long as possible without having oblong or streaked stars. A high ISO setting helps with this and I often use 3200 ISO unless it is twilight or too much man made light is around. Figure 1, Orion and the Peaks of Otter, is a 10 second exposure and the stars are a bit oblong but not too bad.

Widefield – Stacked Images

Images that are composed of multiple single exposures, stacked and aligned in the computer to reveal much more of the faint light features than what is visible to the naked eye. Sagittarius (Figure 2) was taken as series of short, 6 second shots and stacked in the computer using Deep Sky Stacker. The exposure time for shot like this can vary depending on the target, its location in the sky and ambient light conditions. I find that targets nearer the poles may allow a little longer exposure than those on or near the celestial equator, which appear to move more due to their location.

Figure 2: Sagittarius, Credit: Ralph Clements

Star Trails Shots

Long Exposures or combined multiple exposures that show the apparent rotation of the stars above the Earth. Of course, the stars just appear to rotate because we are riding on the Earth which is really doing the rotating (Figure 3).

Taking star trails images is fun, easy and I like the look of them. Although a star trails image of say 40 minutes can be done on the “bulb” setting with a single exposure, this requires a remote timer and more importantly, a very, very dark site as the least ambient light will over expose the shot during that time. So I just take a series of 30 second shots and combine them using “Startrails” software, another useful and free program. This software is definitely easy to use and produces good results, although I do not notice much improvement when I use dark frames with it. For noise reduction I use “Noiseware Community Edition” in the final images instead. I recently became aware of another free software to do this, “Starstax”, and will be trying it soon as it offers more features.

On these star trails shots, sometimes it is good to have some moonlight on the subject and I will go out under a quarter to half moon and shoot them. I find a full moon makes it too much like daylight for my taste and if I lower the ISO under a full moon the stars don’t show up much. So depending on the amount of moonlight, artificial light and desire ground detail, I take these star trails shots at ISO setting of 800, 1600 or 3200. Generally, I try to get 40 to 60 minutes total exposure. Less than that and the trails are too short, more than that and chances are airplane will mess it up.

Figure 3: Startrails, Credit: Ralph Clements

Foreground and Framing

I try to pick a good site with some interesting foreground , although “fore-ground” in this case doesn’t mean close to the camera, rather, it means the part of the Earth that is shown.  I try to frame the shots so that the sky covers roughly ¾ of the frame, since the sky is the real subject and the foreground is really just a reference or point of interest.

Focusing

To get crisp focus on the stars and the ground, anything in the image needs to be as far away as your camera’s “infinity” focus distance, which varies with the lens. So I try to take scenes that I would focus to infinity on if I were shooting them in daylight, such as the farm you see in Figure 3.  For all my images I use the camera’s “live view “. This feature lets me zoom in on a bright star, or the moon and focus. If your target is too dim, aim at a brighter one or an artificial light a long way off and focus on it and re-aim at your target. Make sure your camera is not set to “auto-focus”, use “manual”. The Nikon I was using did not have “live view” but I used the same method, only I looked through the view finder at a bright star or light. Sometimes a few test shots were needed to get it right.   

Getting Started

As for general advice for other beginners, I offer the following

  • Read your camera’s instructions, particularly the section on manual control.
  • Learn to work your camera’s controls in the dark, the corollary of which is….
  • Don’t be afraid to experiment. I use the trial and error method, with lots of trial and plenty of errors. That’s okay though as I am having fun and try to learn from my mistakes, and I don’t have to buy film for a digital camera, so I don’t mind deleting the ones that didn’t come out. 

….just do it! Have fun with it.

 

Further Reading

 

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Startrails – Software

Star trails, image credit: Ralph Clements
Star trails, image credit: Ralph Clements

Star trail images are beautiful to look at and they are captivating because they make time visible. These images can be made either by exposing one single image over a very long period or by taking many shorter exposures and combine them afterwards. Digital cameras deliver images as electronic files, making combining very easy – particularly with software that does all the combining work automatically. One of these software tools is the program Startrails. This software has been developed by Achim Schaller, and he did an outstanding job. Not only is his software really easy to handle, but it comes with powerful features – and it is free. Startrails can be downloaded at Achim’s website.  

The Program

Startrails is designed to automate star trail image processing by combining a series of input files into one final image. It is Microsoft Windows based and runs on Windows XP and later versions. Microsoft .NET framework has to be installed on the computer. Simplicity is a key attribute that sticks out immediately. Only 6 buttons maneuver through all functions of this software. It processes input files in JPEG, TIFF and BMP format and stores results also in these formats.
 

Processing Images with Startrails

Processing star trail images consist of the following steps:
  • Selecting images
    Select all star trail images at your HD or memory card. It is recommended to go through every single image and unselect the ones that have flaws. Air traffic or blinding lights of a passing car can sometimes spoil a good series. Taking out one or two sequential images is virtually not noticeable in the final star trail image but improves the overall appearance considerably. Sometimes however, “disturbances” are wanted; the firework of a meteor or the bright reflection trail by the International Space Station (ISS) are usually considered an upgrade to most images.
  • Dark frames
    Startrails software handles dark frames, or Darks for short. Darks are taken with the lid on the camera lens. This way only noise that is caused by the CCD chip is recorded. Noise in the actual images is random, but each CCD has a particular noise pattern which, can be subtracted from the final image pixels. This step improves the image quality significantly. If more than one Dark is available, Startrails averages them. Using Darks is highly recommended when images are taken with high ISO speeds.
  • Averaging
    Averaging images improves the signal to noise ratio. As a result it reduces (random) noise of the images and increases brightness (luminosity) of the stars. The averaged image becomes brighter and is blended into the resulting image.
  • Run process
    No interaction is required during the run. After it finished, results can be saved in JPG, TIFF or BMP file format.

Startrails Software by Achim Schaller

Note: Images can often be improved by post processing. Stars can be made brighter, background sky can be darkened. Good image processing software is available from many companies or organizations. Photoshop is probably the most common software for astrophotography, but freeware like GIMP performs also quite well.

Time Lapse Movies

Startrails has another powerful feature: it can create time lapse movies. Of course, it can create any kind of time lapse movies, not just astronomy movies. The output format is AVI with the following possible compressions:
Full Frames (uncompressed), Microsoft RLE, Microsoft Video1, Microsoft H.263 Video Codec, Microsoft H.261 Video Codec, Indeo® 5.10, Cinepack codec by Radius, Logitech Video (I420), Intel Indeo Video R3.2, Intel Indeo Video 4.5, Intel IYUV Codec.
Startrails converts the image input resolution during compilation into the wanted AVI screen size. The same is the case with the desired frame rate (fps) and some compression settings to set the streaming speed (kbps).
 

Equipment

I’m often asked the question:  What do I need to take star trail photos? Well, the answer is: not much. A camera with remote capability and a solid tripod is basically all that is needed. The camera should make JPEG, TIFF or BMP images. The tripod has to hold the camera steady, even when light wind gusts occur.

Camera

DLSR cameras are perfect, but simple point-and shoot cameras may work as well. Even smart phone cameras may be suited. There are no real strong demands on camera optics; it simply depends on what image quality level you desire. The better the optics the better the resulting images will be. The faster the lens (1/f) the less ISO speed is needed and with that, lesser noise is introduced. Other things to consider:
 
  • Memory Size
    The memory card must offer sufficient space to hold the truly huge amount of data that will be stored during the shooting session.
  • Remote Control Capability
    Some cameras offer image-series capability, these cameras can work on their own. Most other cameras need to be remote controlled. Whether continuous shooting mode is used or a remote control with multiple timer capability (intervalometer) is connected to the camera, depends on the preferences of the photographer. I prefer remote controls with timers because they give me most flexibility and I can choose any delay between two images. This allows setting longer intervals for time laps movies.
  • Wide Angle Lens
    Star trail photos look better with many stars on the image. Foreground objects are improving visual image balance. Most photographers use their widest angle lens (or zoom setting) for these photos to capture as many stars as possible for best effects.
  • Manual Focus
    Most digital cameras have great difficulties focusing on stars when the rest of the image is extremely dark. Manual focus capability is required for star trail photography; any auto focus feature on camera or lens has to be off.

Conclusion

Startrails is a powerful, yet easy to use all-in-one program for star trail imaging. It allows to create time laps movies in AVI format. Startrails is great freeware and well suited for beginners and advanced amateur photographers.

Send us your star trail photos. Tell us where and how you made them.

 Further Reading

  • Star Trails and Night Photography
    Great website by Steven Christenson – highly recommended. Steven provides a wealth of information on star trail photography. His gallery shows breathtakingly beautiful star trail images.
  • Star Trail Photography
    Harald Eden’s website offers also good information on star trail imaging. Additional information is provided on Lighting and Clouds photography.
  • Astrophotography for $100
    Another Astronomy Source article that offers tips on astro-imaging with basic cameras.

 

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Solar Dynamics Observatory

Solar Dynamics Observatory 2017-03-24T10:11:58Z
Observatory: SDO
Instrument: AIA
Detector: AIA
Measurement: 171

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