10/11/2012 07:28:00 AM
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The above picture was captured by Mr. Brian Drourr, and you really should click on it to see it larger. Brian is one of the moderators at our super popular and very active Facebook Group. If you are not a member, you should be. This was an absolutely fantastic shot. Now I will get into what he did to capture it, but I have to explain to you that he never could have got this done without the very detailed tutorial written out and explained by another PhotoTips member. Mr. Steve Jones.
Steve is our resident Night Photography Expert. Seriously. That is his official title. Steve is usually up designing, creating, and planning his next set of shots while most of the rest of us are all snuggled up in our beds. I have taken his very detailed tutorial, and virtually copied and pasted it below. Many people have read it and followed it on the forums, but by officially moving it to the website, it will make it easier for new people to find by linking it in the Tutorials section.
But back to Brian's shot above. What you are seeing is not one photo, but over 160 images stacked together. Each shot was 30 seconds long. He took about 190, but as he went through them one by one, he would remove the shots that had planes flying over, or satellites passing by. The remaining 160 shots were each processed the exact same way in photoshop. The purple tint comes from bumping the temperature slider in Lightroom to warm up the white balance. The orange and yellow lights in the horizon, was the color shifted Aurora Borealis that was visible in the night sky above Lake Champlain located in northern Vermont.
Those 160 shots were then converted to jpeg from RAW. The next step was to use a special program and an action created by Steve to stack those photos together.
Again, awesome shot.
So what is the process, what is that program, and where can you get that action that I referred too? In the very detailed tutorial by Mr. Steve Jones. Click on the "read more" link below to be taken to page 2 of this article.
BEWARE Star trails are ADDICTIVE oh, and this tutorial is long... 
(Copy-written by Steve jones. Duplication is forbidden without permission)
This tutorial was created so that I didn't have to continually tell people on the Facebook Phototips page where to look for actions and programs and how to's. I decided to just put it all in one tutorial and provide a link to it. Hopefully sometime in the future JEB will do a video tutorial on the subject and a link can be added here as well.
This tutorial is not exhaustive...yep, 7 pages typed, single space, without pictures, and it is still not exhaustive. 
(Hey, shooting star trails IS easy...explaining how to do it from beginning to end, is not) However, in the tutorial, I have links to several web sites including Star Trail Academy (http://www.startrailacademy.com). The Academy has a blog (It's a tab marked “Journal”) that is bordering on exhaustive, so if you want more information than this, I suggest that you start there...they also have classes and workshops on stellar photography and the like if you want to go further than that. This is not an advertisement for them, I am just saying that I learned a lot from their site, and they deserve the credit.
(Hey, shooting star trails IS easy...explaining how to do it from beginning to end, is not) However, in the tutorial, I have links to several web sites including Star Trail Academy (http://www.startrailacademy.com). The Academy has a blog (It's a tab marked “Journal”) that is bordering on exhaustive, so if you want more information than this, I suggest that you start there...they also have classes and workshops on stellar photography and the like if you want to go further than that. This is not an advertisement for them, I am just saying that I learned a lot from their site, and they deserve the credit.
To make it easy, I have divided it into sections: Introduction & Equipment, Planning The Shot, Taking The Shot, and Post Processing the Shot. It is also written so that anyone from the novice to the expert can hopefully understand. I have also provided links to websites that can explain it better than I can. But I have also made assumptions that you already know how to operate your camera in manual mode, know how to work your way through RAW editors, and know how to change a blend mode in the editing program of your choice. So without further ado:
Creating Star Trails
Introduction & Equipment:
Taking star trail pictures is fun, and easier than you may think. During the film era, star trails required you to leave your shutter open for hours and to be located in near complete darkness to reduce light pollution. Thanks to modern digital cameras and programs like Photoshop, star trails are now a matter of taking multiple consecutive images and blending together.
Here is what you will need:
Essential Equipment:
-Computer
-DSLR Camera with Bulb mode
-Off Camera shutter remote, preferably one equipped with an Intervalometer.
-A sturdy tripod...you could also use something like a rock or a sandbag. The only requirements is that neither it nor the camera move during the shoot.
Other nonessential equipment:
-extra batteries, if you plan on going for longer than an hour. There are also ways to make modified batteries that will extend the life all night so that you don't have to change them at all, but I am all thumbs at that, so I will let you explore on your own, ;-D
-Hand warmers wrapped in a rag, homemade lens heater, or a battery operated fan for frost/dew control.
-Battery Grip to allow for easy exchange of batteries
-Compass to find North
-Flashlight(s) (if possible. 1 with red LED(s) to aid in night vision)
-Star Charts
-Chair
-Book on CD/mp3 player, or old fashioned paper
-Coffee...lots of coffee
-Friend or Spouse
Planning The Shot:
Planning is as always most important. There are several questions that you must ask. For example :
Where is the moon?
Do I want my star trails to be circular or linear in nature?
What's in the foreground?
Do I need to light the foreground object?
Is it windy? Humid? Cloudy?
Nearest town or city?
Solar storms and meteor showers?
It could go on and on, but these are the basics. It's just like taking a picture in the daytime. Where is the light? What is going on in the FG/BG? Etc.
Let's take this image as an example:
This picture was taken during the day, which in a way, is the start of the process. Does it look good in the day? If it doesn't look good in the day, adding a star trail around it will not help it at all. So make sure it looks good to begin with. In this picture, the barn is the foreground object. Always have a foreground object, as it grounds the viewer. Remember that star trails are just one element to the whole picture.
The barn is facing east so a head on shot like this would render straight lines overhead. If it were facing north (or south in the southern hemisphere), the lines would be more circular. This is due to the rotation of the Earth.
It is off the road several feet, so traffic safety isn't an issue, but headlights might cause unwanted light pollution. It does not mean that an image will be bad, but it just means that you may have to do more post processing.
At this time of the month, the moon is full, and it will set behind the barn. So if you want to use the moon to light it, you need to take it as it is rising, or is straight overhead. However, the moon will have light pollution issues with the stars, so you will have to deal with that as well. Generally In the northern hemisphere when dealing with the moon in regards to star trails, it is best to shoot to the north, so that the moon will be behind you.
The nearest town is around 20 miles away, so light pollution from town may still be an issue, but not a big one because of the size of the town and the shorter shutter speeds. Light pollution from towns and cities will appear as orange domes on your images. Although in some cases it may enhance the image, it is generally considered a detractor from an image with star trails. For assistance in finding dark sky areas in the USA, go to http://www.jshine.net/astronomy/dark_sky/ . They have a map of most of North America that shows the effects of light pollution. The closer to black that your area is in the better. My part of the country is yellow and green, which is not the best, but it is also not the worst. For the rest of the world, search “dark sky map” and the country that you are interested in. There are light pollution filters out there, but I have not dealt with them, so I cannot give an opinion on how they work.
Another light polluter is the Sun. You generally do not want to start a star trail picture till at least an hour after sunset. This is usually the beginning of “astronomical twilight” where everything turns from a rich “nautical twilight” blue to a deep, dark, almost black, blue. This of course is also dependent on the Moon effect on the sky...more moonlight=lighter blues, new or no moon=near black. I generally do them after midnight, but that is because I work second shift and am not home till then.
Make sure there are clear skies and no dew or frost in the forecast so there are no star blocking clouds or dew/frost on lens issues. A dryer, less humid night will ensure that the trails to be clear and sharp. If dew or frost could be an issue, prepare for it by bringing hand warmers or other some other method of frost removal. If you want a possible shooting star, pay attention to that forecast as well.
I wanted to have more of a circular trail in my image, to get the your camera needs to be pointed in a northerly direction, preferably at the North Star. A full on shot like the one above is out because it faces a more easterly direction. However, I can take more of a side view shot and get a shot closer to what I want. Finding the North Star in the night sky is fairly easy. Here is a link to a video made by Robert Massey from the Royal Astronomical Society to explain how to find it.:
Of course this is for people in the northern hemisphere. For all the southern hemisphere folks, Sigma Octantis is the closest star to the southern pole, but it is a faint star even on clear moonless nights. So finding and using the Southern Cross (Crux) and the Southern Pointers constellations to align your camera will give the same approximate results in the final image. For directions on that, sadly a Wiki article is the best online explanation.:
Taking The Shot:
My camera for this shot was a Nikon D300. I shoot RAW, because JPG doesn't really allow for good post processing if it is needed later. My lens of choice is a 16-35mm f4, but any Digital SLR with a bulb mode, and landscape lens (15-70mm) will work. White Balance is anything other than Automatic...I generally use Daylight, then do minor corrections in ACR. Switch to manual everything because you don't want the camera to make any guesses as to where the focal point is. It will not choose correctly. If your camera has long exposure noise reduction, turn it off, if you don't there will be star dashes instead of star trails. Another setting to turn off is the mirror up function. Although you would think that you would need it, the amount of vibration in relation to the amount of light entering the camera the shutter speed is negligible, plus the amount of time that the mirror is up creates that much of a gap in your trail.
With my camera and lens selection; 16mm and f4 and a cropped sensor, anything 10 feet and out will be in the hyperfocal distance of the lens. That is, the point at which everything from that point to infinity will be in focus at a given aperture and focal distance. Therefore all I will need to do is make sure that what I want in focus is at least 10 feet out, my focal distance is 16mm, my aperture is at least f4, and my focus is set to infinity.
(Note: http://www.dofmaster.com/ is an online depth of field (DOF) calculator website to aid in finding the hyperfocal distance of a given lens)
Before continuing, you will need to become familiar with the Rule of 600...”OH GREAT, more rules!” you say. Don't worry. It's easy, but important for both sharp stars and star trails.
For 35mm DSLR/SLR cameras, the rule of 600 is a formula used to determine the point at which the stars will start leaving noticeable trails. It is mostly used when you want sharp stars, but is also helpful for finding out what your minimum shutter speed needs to be for trails..
The formula states that dividing 600 by the EFFECTIVE focal length(fl) of your lens equals the maximum shutter speed(s) for sharp stars, or: s=600/efl.
An easy example is a lens with a 10mm fl will allow for 60 seconds before a star trail will begin to form; 600/10=60s a 50 mm lens will be 12 seconds. So for my 16mm focal length, and 1.6 crop factor, it will be 600/(16x1.5)= 25sec, so my shutter speed will need to be above 25 sec to start seeing star trails....I usually start at 30 sec. So lens selection is important. A fisheye type lens will not be a good lens to use for star trails because to even get a star trail to begin forming, you will need to have shutter speeds over 60 sec. However, any lens from 15-50mm should produce satisfactory results. When you go beyond that, you have to watch out for noticeable gaps between the shots..and long enough exposure time.
The general work flow for setting up the shots is as follows:
-Set camera to a high ISO, like 1600, and a “fast” shutter speed of 20 sec or so. Set on tripod and take a picture, is it straight, in focus? Now is the time to correct it.
-Reduce ISO to 200-400 and increase shutter to expose foreground to your liking. I have gone anywhere from 30sec to 1 minute on a full moon night to 5 minutes on a dark night. The sole purpose of this is to get good detail in the foreground, kind of like HDR photography. Your sky will have a lot of light pollution, but your FG will be properly exposed. You may not need it, but you will be mad if you do need it. You can also do some creative light painting here as well if the night is too dark.
(Example of exposing for foreground objects)
-Increase your shutter to a speed slower that your 600 rule speed. Take a couple of test shots...you should see the stars and near underexposed silhouettes of foreground objects. If sky is too dark then slow the shutter speed to bring out the stars, but beware light pollution, some is okay, but a lot is not. How much light pollution is a lot, I don't know, it's up to you. ;-D It should be around 30-45 seconds on most lenses, but don't be surprised if you have to go a minute or so. If you are dealing with a full moon, you may have to drop the ISO further, but I never have had to. Again, If you can get the foreground lit, and get the star trails, and very little light pollution, then go for it; it will save steps later in the process. Every shot is different, so make sure to both experiment and cover all the bases.
-Now here is where there is a split in how to proceed. It all depends on equipment and camera functions.
What you need to do is to get your camera to take at least an hours worth of 30-45 sec. exposures. Most cameras only go to 30 before going into bulb mode, although I did hear of a camera that can go up to 60 seconds before going to bulb mode.
If you are going to need to go over 30 sec., and you do not have the afore-mentioned camera, then you are going to need an intervalometer...unless the thought of holding the remote button down for 45 seconds 85-240 times seems fun to you. Every intervalometer is different, but you basically want it to shoot a specified shutter speed, with the least amount in between shots (generally 1 sec), for as many shots as you want. Mine has a shoot until you want to stop setting, so that is what I use. I start it then let it go for an hour. So set it up how you want, and click away.
I have also found that if the shutter speed is within the confines of the camera's settings that, for mine at least, I can set the shutter speed and take my camera off of single shot mode and setting it to one of the multi-shot, continuous shooting modes and lock the shutter button down on the remote, and it will go for 100 shots...HOWEVER since it's limit is 100 shots, your final image will be under an hour long...unless of course you camera goes over 30 sec. Since you are not taking 5 exposures a second, it will not tax your buffer. There is less time between shutter clicks, so gaps in the star trail are also reduced. I have also discovered that you can go back to the camera every half hour or so, release the shutter, and then immediately lock the shutter back down again, it will reset the counter. Also some newer cameras do not have this limit of 100 shots...so it may be worth a little experimenting on your part to see what works for you.
-However way you go, after you start the shooting, don't stop it until you are ready to call it a shoot. One,two, four or more hours, it is up to you. But if you stop the shooting for more than a second or two, you will start to see gaps in your final image. So basically set it and forget it and only come back to it to change batteries and the like. This is the time to read that book, talk to the friend, go kissing in the dark with your spouse...keep it G!, catch up on your Phototips podcasts, take a nap, go back to camp and get a bite to eat, or do some light painting, whip out your telescope and a Nikon J1 and do other stellar photography...or just set there and star gaze. The point is that your camera can get along fine without you, and will only need a change of batteries. If you have a battery grip that allows you to have a battery in the body as well as in the grip, you can go all night, or as long as you have batteries. If you do not, then you may need to do more post processing in the end.
(Example of 30 exposing for stars.)
-After you get all of your shots, go home and download them to your computer, and then go to sleep. Get some rest, and we will deal with the photo blending in the morning.
Post Processing the Shot:
Ahh! It's morning. (Or in my case afternoon, I generally get to sleep till noon.) The computer screen is warming up, there is a pot of coffee that your loving spouse has started brewing and you are ready to see the product of your sleepless night. Great -- just fire up the ol' photo blending program and begin blending the images. “But which one do you use?” you ask. Good question. The answer again, “Depends on you.”...don't you hate that? But really, I don't know how much you have to spend, or what you have already. So I am going to go into a few options and I am sure there are more out there. This is just what I use.
Photoshop CSx:
Before continuing, I am assuming that you have loaded all of your RAW files into ACR and done all of the color correcting, noise reducing, exposure modifications etc. that will need to be done. Which is real easy by doing it to one, and then using the synchronize button for the rest. The blending in all of the techniques is the same technique for all programs. You take the lighter pixels from the one layer and blend them so that they show in the final image. This is a pill...doing all of that masking or erasing...oh wait! Of course, the lighten blend mode, that's what it's for!!! I'm kidding of course, all of the programs listed below have some way of using a lighten blending mode technique to get the end result required.
The basic method of blending the files is this: open first picture then open the next picture and copy it onto the first one and change it's blend mode to lighten. Quick, easy, took less than a minute, you are done, right? Yeah, with the first two, but you have at least 60 or so, in some cases, you may have 120shotsx4hours that's...wait I have run out of fingers and toes..it's a lot, believe me (480 shots, I know.) So at the very least, doing it this way will take FOREVER, and you will never want to do it again. So, here is what to do:
From Bridge, select all of the files except the ones that you took for foreground detail (that's for later.) Then up in the command bar, select Tools>Photoshop>Load Files into Photoshop Layers. Then when they all open up, you start with the top and change its blend mode to lighten and just work your way down....Hey, this sounds like the perfect time for you to create one of “them there actions to do this”, that way all you have to do is click play a couple of hundred times.
***Lighten Mode Action***
Select a layer in the stack
press create new action
select layer above by using the command key (alt+] Mac users; use Option instead of alt.)
set blend mode to lighten.
Stop recording.
Now just start at the bottom of the stack, and start running the action, then repeat running the action till done. This will work on any version of Photoshop that has actions, layers and lighten blending mode, so don't worry. If you don't have the latest version, you don't need it. You could probably add more “select layer above” and “set blending mode to lighten”, and there is probably a way to do it in a more automatic way, but this is the basic action for every version of Photoshop...you need to learn how to go beyond the basic action on your own. You may also want to do just 60 or so at a time because of memory issues. In the end you just merge the layers, and copy and paste the resulting layers into one file and change the blend mode to lighten. After all of the blending changes are complete, merge the layers down to one layer and save it.
(Note: Make sure and use the command keys, when creating the action, because not all your layers will be named layer 1 and 2. Alternatively, you can start at the top of the stack, and do the action using the select layer below command keys, which is alt+[ )
Photoshop CS5
There is an automated way of doing it! YAY!!! which works fine and dandy unless you have a airplane or helicopter that is blinking through an image that you want to get rid of. More on that later.
Go to http://blog.starcircleacademy.com/2011/ ... -in-ps-cs5 : “Automated Stacking of Star Trails in PS CS5”. At that blog entry, there is an action set that will do everything automatically. It's faster than the Manual lighten action described above, and it can be used with RAW files. The only bad thing about it is that it flattens document, but you will have to do it anyways: the file will be too big otherwise. This is just a pain when you have to get rid of an airplane or helicopter strobe, more on that later. The blog entry has everything that you need to know on how to run it. I would just add to it that you need to add all of the files that you want to blend in a separate folder from your lighter foreground shots, because it will cause problems later. I did ask if it works for other versions of Photoshop, but the creator of the action didn't know, so it might work in other versions. I imagine if you have the batch command in your version of Photoshop, you can get it to work.
I did not go into GIMP or Elements or any other photo editing program here because quite frankly, I have never used those programs. I'm sure that there is a way to do it in there, I just don't know how.
Okay so what if you don't have a Photoshop program or GIMP or some other editing program? Are you out of luck? Did you spend hours on end taking useless pictures and wasting shutter clicks? Of course not. There are a couple of programs out there that are free and do pretty much the same thing and more in some cases.
Two programs are out there. One is Startrails (http://www.startrails.de/html/software.html)
The Good: Faster than Manual, Do not NEED Photoshop, can save as TIFF and JPG, has options to remove hot pixels if you have that problem
Bad: No RAW support, so you will have to convert to JPG which takes time, and the JPG is a lower resolution than original. However, the overall pixel size is larger, so if you brought into an editing program, you can up the resolution to original ppi, and the picture's dimensions will return to original dimensions.
StarStax (http://www.markus-enzweiler.de/software/software.html) is pretty much the same as Startrails, but is more user friendly in my opinion:
Good: Fastest, save as TIFF and JPG, has options to remove hot pixels if you have that problem.
Bad: No RAW support, so you will have to convert to JPG which takes time, and the JPG is a lower resolution than original. However, the overall pixel size is larger, so if you brought into an editing program, you can up the resolution to original ppi, and the picture's dimensions will return to original dimensions.
I like Star Circle Academy's action better because it works with RAW files, is semi automatic, and can be left alone...unless there is movement or unwanted plane lights in picture.
With Starstax and Startrails, and the action from Star Circle Academy, you can create time lapse video image stills of the process so that you can later use Picasa to record a video of the star circle coming together.
There is also a method of using smart objects and the stack modes, but the amount of time it it takes is 3 minutes past forever, so I am not going to go into how to do it.
How to get rid of plane and helicopter trails:
If you have issues with airplanes and other IFOs with the strobes blinking and the landing lights on, don't despair. There are ways of removing them. If you have UFO's and shooting stars and such, Great! Leave them in. It will add interest and might find its way into a magazine if the UFO was from the planet Zoltar...
If you are using the Academy action, what you do is isolate the offending images from the rest in a different folder so that the action doesn't reopen them later, and open them all in a layer stack through Bridge as mentioned before, with the first one being an image that doesn't have the offending lights. Change the blending modes to lighten and then use the history brush to paint away the lights on each layer, being mindful of not accidentally removing a star (which you can just undo if you do ;-D)
Easier way, Since in the end, you will be blending with the lighten mode, you can just paint over the area with black, again being mindful of the stars, and the other layers when blended will remove the black from the final image. Whichever way you go, in the end make sure that all of the blend modes are set to lighten and merge down. Finally use the resulting blended picture as the first picture that the rest of the shoot will be blended onto. Then run the action as described on the blog, leaving out the “Do this FIRST” part of the action since you already have a file to add layers on to. As you can probably guess, you can use the same procedure when using the manual lighten blend mode procedure mentioned above. The only thing you do not want to happen is that somehow part of it is lighter than the other layers, because it will show through in the final image.
If the foreground is too dark, then use the longer exposure shots to bring out the details. Just use layer masks, adjustment layers, blending modes, and opacity sliders to get it where you want -- you know, typical Photoshop stuff.
(Finished star trail; lightened barn, removed green cast given off by security light, city light pollution from the BG and surgical removal of house.)
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