PDA

View Full Version : What type of effect would a train passing 2 miles away have on a astrophoto?



robert christ
2013-Feb-17, 07:56 AM
If your view (of the train) is obstructed (blocked with some type of wall or a building or your inside a dome) would the light from a train passing 2 miles away affect your photo?
That is my situation, I live 14 miles east of T or C, nm so the skies are pretty good otherwise. It's desert so the trains that come by are plainly visible and cast pretty vivid shadows on my buildings as they pass by. (from their headlights three very bright ones)
robert christ

RickJ
2013-Feb-18, 07:58 PM
None of any significance. If imaging through a ton of humidity (unlikely from your location) or thick dust then it might raise the background level slightly but again not enough to be significant. I have a problem with this but the light comes from fishermen using lights only 100 yards away pointed directly at the observatory trying to figure out that crazy building. Those light up the inside of the house like daylight, nothing like a train 2 miles away.

I'd be more worried about vibration. Again rather unlikely at 2 miles but given the right ground conditions vibration can travel amazing distances. I used to work from a site a quarter mile from tracks without an issue but then LP became a problem when a small town put in a super well lit sewage system by the tracks. I moved to a different location about a mile from a different train track only to find the train's vibration greatly increased star size and fuzzed detail unless I blocked the scope during a passage. The ground transferred the vibration at this location but not the first. A third move with no tracks that were used for high speed coal trains or other high speed heavy loads solved the problem. At two miles I doubt this would be an issue but I'd rate it a far higher concern than the light if they are fast moving heavy freight carrying trains and ground conditions transmit vibration well.

Rick

robert christ
2013-Feb-19, 07:15 PM
None of any significance

That's good to know! I never thought of vibration, the trains do carry coal but generally at low speeds cause they tend to stop over in Engle 6 miles north to switch drivers and don't seem to have built up significant speed by the time they pass by me.
Sonic booms from training jet's in white sands that's a different issue I still jump out of my socks when I hear those, fortunately they are usually during the day or early evening. The percussion rattles every panel in my metal buildings.
Thanks Rick
Robert