1. Image is extremely out of focus. 2. Image is brought closer to focus. 3. Image is almost focused. 4. Image is now focused. 5. The image has now been gone past perfect focus and will have to be brought back in focus by adjusting the focuser in the opposite direction. 6. The image is back in focus. At this stage the image needs to be zoomed in to to check this is really the best focus you can get. The star points should be small and have the small peaks of the triangle just appearing at the dots three corners
The Photographer's Ephemeris Welcome! The Photographer's Ephemeris (TPE) is a tool to help you plan outdoor photography in natural light, especially landscape and urban scenes. It is a map-centric sun and moon calculator: see how the light will fall on the land, day or night, for any location on earth. TPE desktop
On Sunday 28/12/2014 I finally managed to photograph the ISS crossing the moon. The timing and location must be very accurate. The moon is only half a degree in the sky and the time it takes the ISS to pass over the moon is less than a second. Here is the video. The details and explanation will follow. Make sure to watch the video in full screen mode with 1080HD resolution...
500 Divided By the Focal Length of Your Lens = The Longest Exposure (in Seconds) Before Stars Start to “Trail”
For example; let’s say you’re taking a shot with a 24mm lens on a full frame camera. 500 / 24 = 21 seconds, which you can round to 20 seconds.
Here are two shots taken with a 14mm lens on a full frame camera. At 90 seconds you can see the blur of the stars, but at 30 seconds the stars are nice sharp points of light ...
1st constant is earth rotation, 0.0042 arc degrees per second
or 1degree rotation per 238 seconds
Rule of 600
Finally, in order to avoid the star trail (that is avoiding capturing
the movement of the stars as the earth rotates) you have to use the RULE
of 600 which is very easy:
Divide 600 by the focal length of the lens you are using. In my case I
divided 600/28 = 21.42 ( I can leave the shutter open for 21 seconds and
avoid capturing the star trail)
Bristlecone Pine Star Circle *Explored* Steven Christenson
Steven's Tree and Star Circle (19 exposures, 8 minutes each ISO 100 so a total of 2 hours and 32 minutes). First exposure was at 10:53 pm, the last at 1:18 am. Long exposure noise reduction OFF. f/4, 23mm.
