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Nikon DSLR Cameras
D3400
Newbie's (blackstar) Moon Shot questions and helps
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<blockquote data-quote="WayneF" data-source="post: 719158" data-attributes="member: 12496"><p>You probably will want a wide view for like the Milky way, so 18 mm is likely appropriate. </p><p></p><p> Stars will require a long exposure (perhaps ISO 3200 wide open at f/3.5 for maybe 30 seconds. Experiment...</p><p></p><p>So a problem is that such long exposures show the Earths rotation, leaving star trails instead of dots, but the wide 18 mm minimizes this, not to the very sharpest dot, but possibly very acceptable in a normal size viewing image. </p><p></p><p>The longer lens would greatly magnify this rotation movement. The longest lens could be useful for zooming on a small object, like for example the Andromeda galaxy, but then rotation blur will be a huge problem. Then that motion really needs a tracking polar mount, like for telescopes.</p><p></p><p>My site has a calculator for this rotation blur, at <a href="https://www.scantips.com/lights/stars.html" target="_blank">https://www.scantips.com/lights/stars.html</a></p><p></p><p>The infinity mark on the lens is probably not precisely at infinity, lenses today often have a little intentional overshoot. You could focus it at infinity on some land object in the daylight, and leave it there for the night work, however any little touch would move it (so it does seem doomed). </p><p></p><p>What I do is to use live view on the stars at the site. At first, you see nothing (too dim) but as you zoom in greatly (zoom in on the live view preview, definitely NOT meaning to zoom the wide lens), and as you move focus to be at infinity, the brightest stars begin to show, and of course, the moon is a good target too. You can find some bright star to focus on. All the stars are at infinity, there will be no focus difference. The smallest brightest focused star dot image seen in live view is the correct focus. Then of course put the camera in Manual focus mode so it won't change, but be careful not to touch it again.</p></blockquote><p></p>
[QUOTE="WayneF, post: 719158, member: 12496"] You probably will want a wide view for like the Milky way, so 18 mm is likely appropriate. Stars will require a long exposure (perhaps ISO 3200 wide open at f/3.5 for maybe 30 seconds. Experiment... So a problem is that such long exposures show the Earths rotation, leaving star trails instead of dots, but the wide 18 mm minimizes this, not to the very sharpest dot, but possibly very acceptable in a normal size viewing image. The longer lens would greatly magnify this rotation movement. The longest lens could be useful for zooming on a small object, like for example the Andromeda galaxy, but then rotation blur will be a huge problem. Then that motion really needs a tracking polar mount, like for telescopes. My site has a calculator for this rotation blur, at [URL]https://www.scantips.com/lights/stars.html[/URL] The infinity mark on the lens is probably not precisely at infinity, lenses today often have a little intentional overshoot. You could focus it at infinity on some land object in the daylight, and leave it there for the night work, however any little touch would move it (so it does seem doomed). What I do is to use live view on the stars at the site. At first, you see nothing (too dim) but as you zoom in greatly (zoom in on the live view preview, definitely NOT meaning to zoom the wide lens), and as you move focus to be at infinity, the brightest stars begin to show, and of course, the moon is a good target too. You can find some bright star to focus on. All the stars are at infinity, there will be no focus difference. The smallest brightest focused star dot image seen in live view is the correct focus. Then of course put the camera in Manual focus mode so it won't change, but be careful not to touch it again. [/QUOTE]
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D3400
Newbie's (blackstar) Moon Shot questions and helps
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