Astrophotography Resources

[Msteelio91]

Does anyone know of any sites or resources for finding forecast information about atmospheric conditions? Such as air clarity/visibility, clouds, and moon/milky way positioning.

 

[WayneF]

try astronomy atmospheric conditions - Google Search

 

[shefjr]

Pgriz told me about spaceweather.com that is where I would look for all things space.

 

[KmH]

Stellarium

Weather is local, so 1st go to weather.com look at their maps, and 2nd - go out side and look up.

 

[Msteelio91]

Thanks guys, I had already done some searching but didn't come across space weather.com or the stellarium site, I'll have to check those out. I did find one that gives a visual representation in graph form for cloud coverage, humidity, temp etc. all things that are good to know. I'll post it up here when I'm not on mobile.

 

[TCampbell]

For conditions, use ClearDarkSky.com: Clear Sky Chart Homepage (You'll need to learn how to read that... they give a row for cloud cover, "transparency" of the atmosphere (excluding clouds), "seeing" (atmospheric stability... poor seeing not only causes the stars to "twinkle" (atmospheric scintillation) but it also causes us to get less detail than we can get when the seeing is improved) and then of course "darkness".

To have good "seeing" (atmospheric stability) you generally want to be at least 200 miles away from any warm front, cold front, or the jet stream. You tend to get better seeing when you're in an area that is good for "smooth laminar flow" of air... such as over a large body of water. Land tends to create lots of thermals and turbulence disrupting the airflow and degrading the seeing conditions. For many (most) of us, excellent seeing is a rare thing.

I recently made a video showing how to use the "Model" data at Wunderground.com to do this as well. The video is here:

As for knowing where the Milky Way will be positioned.... you'll want to use some computer planetarium software. I use Sky Safari on my phone and iPad and I use Starry Night Pro Plus on my computer. These are both commercial (non-free) apps (although editions of Sky Safari can be pretty inexpensive) -- but Stellarium is open-source and free. You can find it here: Stellarium

If you plan to take Milky Way shots, then you ALSO want to know the phase of the moon. Basically this works best when there is no moon (shoot during the new-moon or shoot before moon-rise or moon-set if it's not near new-moon.) The moon will put a lot of light pollution on the atmosphere and ask you take long exposures the background sky which should be near black will expose as a muddy brown instead.

You'll also want to know the "Rule of 600" (or if you use an APS-C camera, just modify it and use the "Rule of 400" (600 ÷ 1.5 crop factor = 400)). The rule was originally invented for 35mm film (so it also works with "full frame" DSLR cameras). It says you can divide 600 by the focal length of your lens and this will tell you how long you can leave the shutter open (in full seconds) without getting any blur caused by moving stars (stars will not start to grow "tails" due to the Earth's rotation).

Example (with an APS-C size sensor DSLR):

If you have a 10mm (e.g. 10-20mm ultra-wide zoom set to 10mm) then 400 ÷ 10 = 40. You can leave the shutter open 40 seconds.
If you have a 20mm lens... then you can only leave the shutter open 20 seconds because 400 ÷ 20 = 20.

This assumes the camera is mounted on a solid tripod which is not tracking the movement of the sky. If you ARE tracking the movement of the sky, you can go much much longer depending on the accuracy of your polar alignment. To do that you need a tracking rig such as a Losmandy StarLapse, an AstroTrac, an iOptron SkyTracker, or a Vixen Polarie Sky Tracker. The "tracker" is mounted on a tripod and aligned so that it's major axis of rotation is pointed at the celestial north pole (very close to Polaris, the north star). Once aligned, you can point the camera anywhere and the tracking head compensates for the rotation of the Earth.