Starguide - A Practical Guide to Astro-Photography

With the technical means of digital photography available today, there are basically two approaches to astrophotography:

1. the use of special electronic equipment for image control and automatic tracking (hereafter referred to as EAA) to which this guide refers.

2. minimal technical effort using a DSLR camera. See the astrophotography for beginners section below.

1. Electronically Assisted Astronomy (EAA) 
refers to the possibility of observing celestial objects not through eyepieces, but with electronic cameras (today mostly CMOS-based digital single-lens reflex cameras (DSLR) or special astro cameras with additional tracking support by control programs (electronic guides), in order to compensate for design disadvantages of the mounts and thus to achieve very long exposure times that would not be possible without these electronic aids.

Please start with the Equipment Tips to get into the topic.

2. Astrophotography for Beginners

Astrophotography is the art of capturing the night sky and its objects with a camera. There are different types of astrophotography, such as 

• panoramic astrophotography
• solar system photography,  
• astro-videography (1)
• and deep-sky photography (this will be discussed in later chapters)  

2.1 Panoramic Astrophotography

Beginners should consider the panoramic astrophotography, as it is relatively easy to realize and provides fascinating results.

To get started with panoramic astrophotography, you will need the following equipment: (2)

• A digital camera that allows manual settings for exposure time, aperture and ISO. An SLR or system camera is ideal, but a compact camera or smartphone can also work if you use a suitable app.
• A wide-angle lens that covers as much of the sky as possible. The focal length should be between 10 and 35 mm, depending on the sensor size of your camera.
• A tripod that keeps your camera stable and compensates for unevenness in the ground. A remote shutter release or self-timer is also helpful to avoid camera shake.
• A file format with the least compression, such as RAW or TIFF, to preserve image quality and make post-processing easier.

You can use this equipment to photograph various subjects, such as constellations, the Milky Way, line trails or encounters between celestial bodies. You should observe the following steps (3):

• Plan your astrophotography ahead of time. Choose a suitable location that is as dark as possible and free of light pollution. Check the weather, moon phase, constellations, and the best times for your shots. There are several apps and websites that can help you with this, such as Stellarium, SkySafari, or Clear Outside. (see chapter Astro Photography Session Planning for more information)
• Point your camera at something interesting. Use a compass or app to find the points of the compass. Make sure you have a good composition that includes both the sky and the landscape. Use the rule of thirds to position your subject and keep an eye on the horizon, which should be as straight as possible.
• Manually focus on your subject. Turn off autofocus and set your lens to infinity. Check the sharpness of your image on your camera's display or viewfinder. If necessary, use a flashlight or laser pointer to illuminate and focus on a distant object.
• Set your camera settings for astrophotography. The optimal exposure depends on several factors:
• the brightness of the sky, 
• the size of your subject, 
• the focal length of your lens, 
• and the sensitivity of your sensor. 
• As a rule of thumb, keep the exposure time as short as possible to compensate for the Earth's rotation and to capture the stars as dots rather than lines. A common formula for this is the 500 rule of thumb: 
• divide 500 by the effective focal length of your lens to get the maximum exposure time in seconds. 
• For example: If you are using an 18 mm lens on an APS-C sensor camera, the effective focal length is 18 x 1.5 = 27 mm. 
• The maximum exposure time is then 500 / 27 = 18.5 seconds. 
• You should open the aperture as wide as possible to capture more light. The aperture should be between f/2.8 and f/4, depending on the quality of your lens. 
• The ISO setting should be as high as necessary, but as low as possible to reduce image noise. The ISO number should be between 800 and 3200, depending on the performance of your sensor. 
• White balance should be set to daylight or auto to preserve the natural colors of the sky.
• Take your images. Use the remote shutter release or self-timer to avoid camera shake. 
• Take several shots of your subject to get the best results. Check the exposure, focus, and composition of your image on your camera's display or viewfinder. Adjust your camera settings if necessary. Experiment with different perspectives, focal lengths, and exposure times to achieve different effects.
• Edit your images. Download your images to your computer or smartphone and use software to enhance them. For example, you can adjust the brightness, contrast, colors, sharpness, and noise filter to improve the detail and quality of your image. You can also stitch multiple images together to create a panorama or time-lapse to create a larger or more dynamic image.

If you want to find out more or get inspired, you can check out some of the following websites (these also served as the basis for this chapter):

1. In 8 Schritten vom Astrofotografie-Anfänger zum Profi - Anleitung & Tipps (hobbeasy.de)
2. Astrophotography for beginners (astroshop.eu)
3. Astrofotografie 1: Die Grundlagen - Online-Fotokurs der fotocommunity Fotoschule
4. Astrophotography for beginners - Adobe

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