Reply to thread

Message

<blockquote data-quote="RobHD" data-source="post: 547339" data-attributes="member: 41534">Well after spending time on my bum doing little to nothing , ive finally got round to reading some of my bookmarks on <a href="http://www.astronomyforum.net/wiki/Astrophotography" target="_blank">astrophotography</a> as well as my photography course <img src="http://img.astronomyforum.net/images/smilies/smile.png" alt="" class="fr-fic fr-dii fr-draggable " style="" />&nbsp;most know about the 500 rule for working out exposure times to help eliminiate star trails&nbsp;500 divided by the <a href="http://www.astronomyforum.net/wiki/Focal-length" target="_blank">focal length</a> of the lens.&nbsp;Well reading up found some rather interesting issues, which may explain&nbsp; why i get trails, or the odd spike were its starting to trail.&nbsp;ive been working with a 35mm lens and using the 500 rule &nbsp;So 500/35 = 14.25 so 14 seconds &nbsp;my nikon d5200 doesnt have 14 seconds so ive been using 15 or 10 and getting better results at 10.&nbsp;Now ive just finished reading on my break an article from Grant Collier,&nbsp; great wide field and mosaic photography of the night sky.&nbsp;the 500 rule works great for full frame cameras, but most i know of have cropped sensors, me included.&nbsp;His article suggests that we multiply the focal length by the amount the sensor is cropped.&nbsp;So for the Nikon on the fast 35mm lens it would work out as.&nbsp;500 / (35x1.5)&nbsp;giving 500 / 52.5 = 9.52 &nbsp;hence my better shots at 10secs.&nbsp;So in theory with my kit lens at 18mm i should be able to get 18 second shots before star trails.&nbsp;something else for me to try when i next get clear sky</blockquote>

[QUOTE="RobHD, post: 547339, member: 41534"] Well after spending time on my bum doing little to nothing , ive finally got round to reading some of my bookmarks on [URL="http://www.astronomyforum.net/wiki/Astrophotography"]astrophotography[/URL] as well as my photography course [IMG]http://img.astronomyforum.net/images/smilies/smile.png[/IMG] most know about the 500 rule for working out exposure times to help eliminiate star trails 500 divided by the [URL="http://www.astronomyforum.net/wiki/Focal-length"]focal length[/URL] of the lens. Well reading up found some rather interesting issues, which may explain why i get trails, or the odd spike were its starting to trail. ive been working with a 35mm lens and using the 500 rule So 500/35 = 14.25 so 14 seconds my nikon d5200 doesnt have 14 seconds so ive been using 15 or 10 and getting better results at 10. Now ive just finished reading on my break an article from Grant Collier, great wide field and mosaic photography of the night sky. the 500 rule works great for full frame cameras, but most i know of have cropped sensors, me included. His article suggests that we multiply the focal length by the amount the sensor is cropped. So for the Nikon on the fast 35mm lens it would work out as. 500 / (35x1.5) giving 500 / 52.5 = 9.52 hence my better shots at 10secs. So in theory with my kit lens at 18mm i should be able to get 18 second shots before star trails. something else for me to try when i next get clear sky [/QUOTE]

Verification