Milky Way in a city with a tracker?

Hi!

While browsing the Milky Way images on flickr, I've came across this image.


Basically he took many images of the Milky Way then somehow stacked them together to make the faint Milky Way visible.

Now..that makes me think if I can do the same with a tracker.

Is it possible to photograph the Milky Way over a city by using a tracker for long exposure? I'm sure the city light will be over-exposed, but that can be fixed by composition.

It certainly is possible to capture the Milky Way above a city as the image on flickr shows, although that was generated by using software, rather than tracking. The camera is capable of picking up the faint detail that the eye can not see, although the image will require processing to get the best out of it.

Stacking certainly helps capture more detail but it doesn't add to the exposure, so 2x10 minute exposures does not equal 1x20 minute exposure. It helps to boost the signal to noise ratio, how much depends on how many frames you have. The more the better.

It would help greatly to use an Olll filter to cut out a fair bit of typical LP, but it would still require the moon to be out of the way for best results.

I'll just add that light pollution is a real challenge. If you turn up the ISO too high, then the sky turns brown. Getting a decent shot of something faint from an urban location is difficult and frustrating. A lot depends on how much LP you have as some cities have more LP than others. LA is extremely light polluted, as are any major metro areas with a million people or more. I've read that it takes 12 to 15 times as long in a brightly lit urban location to achieve the same exposure you would get in dark skies. That extra time is going to cost you in noise level. I should also note that the image you referenced was NOT taken inside LA itself but was taken nearby and at a higher altitude on a mountain. Altitude should help and so does distance from the LP.

Moon0326 said:

Hi!

While browsing the Milky Way images on flickr, I've came across this image.

https://flic.kr/p/a44t5A

Basically he took many images of the Milky Way then somehow stacked them together to make the faint Milky Way visible.

Click to expand...

I think it was key that he was up on a mountain, and not in the middle of LA, but a fair distance away. He did not have to shoot from below the blanket of air pollution that reflects the light right back at you, but got above that layer.

There is a time lapse video that shows Milky Way over Mount Tamalpais – very close to San Francisco. It starts at 4:02 here. So it's definitely visible even in a fairly light-polluted area even without stacking, but again, it was some distance away and high up on a mountain.

Vlad

Using a tracker is the wrong way to go. Increasing your exposure time is only going to make the LP that much worse drowning all light from the MW. You might be able to achieve similar results by stacking several 1000 5-10" exposures taken in RAW, but the computer time to stack them and the HD space to store them all, makes it futile.

Likewise, as has been pointed out, this photo was taken a long ways from LA. Sky glow carrys for 60-100 miles from large cities, so while it might look the photo was taken 'in town" it was taken from nearly 30 miles away.

Gas is still cheap, but I don't know for how much longer, but even then, it's still worth a drive later this summer, if just for one night, to get to a true dark site to be able to see the MY with your own eyes while your shooting.

I live dead center in a "larger" city and have never even seen a hint of the Milky Way from my backyard, but this photo was taken 20 min before the start of true astronomical darkness after a "short" 50 mi / 1 hr drive out of town.

Nikon D7100, 17-55mm @ 24mm, F4, 30 sec. ISO 1600.



And this is with a tracker, 1 hr later. 1 single, 3min sub @ ISO 800. All other camera details same as above





Skies like that sure make it hard to drag out my gear in the heart of the city for awhile !

That 2nd image is nice... what tracking equipment are you using? I'm literally on the edge of buying a tracking mount, I just don't know which one to get for my DSLR. (not a telescope)

Thank you for the detail explanation. I will research on OLLL filter and see if I can even try that up in a mountain. I will report back if possible.

Thank you!

I will probably test it out on the same location. I really don't expect to get the same or similar result. I just want to test it out of curiosity It's fun!

Thank you!

That means I need to find a spot in a mountain. I will look into that!

I already know a few places where I can take a good Milky Way photo. I just wanted to experiment it out of curiosity. I mean...it's new idea I probably will try two things if I ever get a chance.

1. stacking a few hundreds of photos. I don't think it's possible at this time since the center of the Milky Way is only visible for a few hours.

2. Just take a shot in a moon less night and try processing it. Who knows !

Just for information I've just watched this video on youtube. He calls it ETTR. I'm not sure if that helps me or not, but I will give it a shot.

Don't bother with an O III ! That's exclusively a nebula filter. While it cut's out a fair amount LP, it will also cut out a lot starlight. There is no substitute, for a true dark sky site, if you want to take MW photos.

This video might help a bit:

How to Photograph the Milky Way in Really Heavy Light Pollution Using ETTR (Expose to the Right)

Moon0326 said:

I already know a few places where I can take a good Milky Way photo. I just wanted to experiment it out of curiosity. I mean...it's new idea I probably will try two things if I ever get a chance.

Just for information I've just watched this video on youtube. He calls it ETTR. I'm not sure if that helps me or not, but I will give it a shot.

Click to expand...

Forget ETTR, and that video, it's an old terrestrial method of dragging up details in shadows. The HUGE problem with trying to use it for AP, is that at high ISO's, you're going to start clipping all of your star colors in just a second or less. Your dynamic range is extremely small at ISO 6400.

But first and foremost, I didn't see a single photo in the video, taken from "The City", or even a heavily light polluted area ! All of them were taken at well chosen locations that kept the city lights behind the camera and many miles away. Sure there was a "little" LP to contend with, but a camera can't magically make the Milky Way appear from nowhere in a single shot ! If you can't see the MW with your naked eye above the LP, a single WA frame shot can't capture it either and only makes things worse !

You are far better off just stacking "normal" exposures. Stack 4 "normal " exposures, and you'll have less than 1/2 the noise of a single "ETTR" frame. You don't even need a tracker.

All of the comparisons between the noise in the ETTR photos vs a "normal" is also to be expected. You can't "stretch up" a single normal photo without radically increasing the noise, but try it with just a stack of 5-10 photos at a "normal exposure/ ISO" and it will leave ETTR in the dust. Try stacking 30-40 "normal" exposures, and you'll see why all astrophotgraphers use stacking. I don't know of a single one using "ETTR".

FWIW, this is what I was able to do, stacking 4 hrs worth of short subs @ ISO 400, using my iOptron Skytracker and a 70mm lens @ f5.6 from the heart of town last fall. I had to wait until 11PM to even get started, when many of the city lights start shutting off. I've NEVER even seen the MW from my yard, but this is what I was able to do with a few hundred shorter exposures and 4 hrs of time on the intervalometer.



I can get the same image in only 20 minutes, using just slightly longer subs, unimpeded by LP from my dark site. Hummm, 4 hrs/ 20 minutes.....4 hours/ 20 minutes. Extrapolate the either way, 4 hrs at a dark site ??

In any event ETTR is a lose/ lose proposition for AP.

Thank you for the information and image.

Even if ETTR won't make a clean and beautiful image, I think it's fun to try if I don't want to drive 3 hours from where I live. At least for me, it would be fun since I'm just 20 or less minutes away from the locations in that ETTR video (I'm in L.A).

Ha..I think I really need to try with a tracker (not for milky way..but for other things in general) and see how things work by failing..

Thank you for the write up again. I will report back whenever I get a chance.

That is awesome!