Re: Astrophotography, Soup to Nuts (long post) in Digital Imaging

Re: Astrophotography, Soup to Nuts (long post) in Digital Imaging http://www.dslreports.com/forum/r13160682 en Sun, 29 Nov 2009 03:09:02 EDT Sun, 29 Nov 2009 03:09:02 EDT Re: Astrophotography, Soup to Nuts (long post) http://www.dslreports.com/forum/remark,13185193 PlagueX1 : I myself also do some astrophotography. Although I currently just have a Meade DS2130, Im planning to get a Meade 8" LX200GPS w/UHTC next week. Hope I can do some photos that are half as decent as yours.:) Im planning to get PhotoShop CS too, currently I just have Paint Shop Pro 7 which I used for my gaming clans and websites. I'm also planning to get a wedge since im going to be doing alot of photographs. ]]> http://www.dslreports.com/forum/remark,13185193 Sat, 16 Apr 2005 11:13:28 EDT Re: Astrophotography, Soup to Nuts (long post) http://www.dslreports.com/forum/remark,13180433 b10010011 :

said by robar

:

thanks noel.
one place i'm surprised you haven't shot is M57, in lyra, the ring nebula. i know this is more or less a winter sight but do you have one?

Actually Lyra and M57 are summer objects. Vega (the bright star in Lyra is even part of the summer triangle.]]> http://www.dslreports.com/forum/remark,13180433 Fri, 15 Apr 2005 18:20:51 EDT Re: Astrophotography, Soup to Nuts (long post) http://www.dslreports.com/forum/remark,13176492 n8crwlr : My wife and I had made plans to go to the Natural History Museum today. Tomorrow they have the National Astronomy Day, Saturday April 16th, 2005. For more info, Also To view locations, there will also
be a grand door prize of a Meade 10" LX200GPS telescope valued at $5300.

I have to work Saturday and will not attend, this is just my luck...... I just got the email from Meade today.....]]> http://www.dslreports.com/forum/remark,13176492 Fri, 15 Apr 2005 09:19:52 EDT Re: Astrophotography, Soup to Nuts (long post) http://www.dslreports.com/forum/remark,13174931 US_1st_Cav : Thanks for sharing Noel!I didn't think it was this complicated!I thought all you had to do is find the star, and take a picture!:o
But all your space pictures are amazing, so keep up the good work Noel!:)
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quote:
At a distance of about 8500 light-years from Earth, Eta Carinae is one of the largest stars in our Galaxy. Eta Car probably contains as much mass as 100 suns, and puts out more energy each second than 1 million suns. Such stars are extremely rare in the cosmos. They have very short lives, punctuated by episodes of stellar "eruptions", mass ejections, and other violent instabilities, until they finally end their lives as huge, violent explosions called "supernovae" in which the energy of the blast eclipses the combined energy output of all the stars in the Milky Way.

Eta Car underwent a huge eruption in the mid-1800's, and recently it's showed signs of renewed activity.

Thanks, ryszt. I shall seek it out when next I'm outside.

-Noel]]> http://www.dslreports.com/forum/remark,13174280 Thu, 14 Apr 2005 22:49:31 EDT Re: Astrophotography, Soup to Nuts (long post) http://www.dslreports.com/forum/remark,13173515 ryzst : Glad to see you're getting some use out of your investment. Nice write-up too. I only own an ETX-90 (pre-goto), which I won at a Christmas raffle many years ago when I was still one of their machinists. It makes a nice terrestrial spotting scope, but is pretty useless for stargazing.

Thanks for the tutorial, especially on subtracting light pollution. Have you checked out Eta Carinae yet? That's the most fascinating object in the heavens to me. When it blows, it'll turn night into day.

Hubble Image of Eta Carinae

]]> http://www.dslreports.com/forum/remark,13173515 Thu, 14 Apr 2005 21:30:06 EDT Re: Astrophotography, Soup to Nuts (long post) http://www.dslreports.com/forum/remark,13173472 simpfan742 : much appreciated, noel!]]> http://www.dslreports.com/forum/remark,13173472 Thu, 14 Apr 2005 21:25:18 EDT Re: Astrophotography, Soup to Nuts (long post) http://www.dslreports.com/forum/remark,13171035 NoelC : Thanks everyone.

Jtmo, it looks about like the second image I posted. The light pollution is visible through the eyepiece, but it's not all that bright. Most deep sky objects (i.e., nebulas, galaxies) are very dim and not particularly impressive when viewed directly by eye, even with a 10" scope. It would probably be better with REALLY dark skies, and even with light pollution the various clusters do provide some eye candy. Basically, stars are beautiful.

jig, I bought the 10" Meade because the 12" is a BIG step up in weight - basically it crosses the "portable" vs. "not really" boundary. My scope does have the UHTC coatings.

Any dSLR that can do up to a several minute exposure without the noise running away would be a good choice. I think the Nikons do this quite well, as do the Canons. The D60 is now two generations old, and does produce quite a bit of noise, though I'm sure it could be made to work.

Robar, no, I haven't photographed the Ring Nebula yet. It's on my list of things to do. :)

-Noel]]> http://www.dslreports.com/forum/remark,13171035 Thu, 14 Apr 2005 17:03:39 EDT Re: Astrophotography, Soup to Nuts (long post) http://www.dslreports.com/forum/remark,13170603 robar : thanks noel.
one place i'm surprised you haven't shot is M57, in lyra, the ring nebula. i know this is more or less a winter sight but do you have one?]]> http://www.dslreports.com/forum/remark,13170603 Thu, 14 Apr 2005 16:07:41 EDT Re: Astrophotography, Soup to Nuts (long post) http://www.dslreports.com/forum/remark,13169886 jig : question about hardware:

i've read that the canon D60 was a great camera to use for long exposure night photography. it obviously looks like you've gotten some good results with the 20d..

i've been looking hard at the nikon D70, mainly because i have some investment in nikon lenses.

do you have any idea how comparative the d70 is to your 20d when taking nighttime long exposure captures?

my future telescope will be meade and similar in make, though probably one or two steps up in size and with the chromatic correction coatings (been saving for a long time).

thanks much for the lesson in photoshop noise reduction..

-jig]]> http://www.dslreports.com/forum/remark,13169886 Thu, 14 Apr 2005 14:33:20 EDT Re: Astrophotography, Soup to Nuts (long post) http://www.dslreports.com/forum/remark,13169812 samburgers : Wow! That is amazing Noel! I know that requires a LOT of patience and lots of warm clothes ;)

The post-processing is VERY involved and amazing too. I never thought that pollution in the sky looks like that when you take long exposures! And it's interesting how you get rid of that too. :)

The detail that you can capture is overwhelming! You are becoming a pro at this fast! :)
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When you look at the Crab nebula, does the light pollution wash it out? Or does it look closer to your final picture?
Your lesson here may be why I am often disappointed with what I look at in the sky.
Of course, the 4.5 inch vs. 10 inch thing makes a difference in most things in life ;) ]]> http://www.dslreports.com/forum/remark,13169229 Thu, 14 Apr 2005 13:17:56 EDT Re: Astrophotography, Soup to Nuts (long post) http://www.dslreports.com/forum/remark,13168693 NoelC :

said by Mauricio9

:

I thought Cuban coffee was illegal in the US... ;)

I work near Miami, and the office receptionist makes it. Always wakes me up at 3 AM. 'Course Miami isn't really IN the U.S. by most accounts... :D

One thing I forgot to mention above... When I do get motion blur or "star trailing" because of imperfect tracking, or out-of-focus images, one tool that comes in really handy is Focus Magic (»www.focusmagic.com). It's a nice package.

-Noel]]> http://www.dslreports.com/forum/remark,13168693 Thu, 14 Apr 2005 12:12:43 EDT Re: Astrophotography, Soup to Nuts (long post) http://www.dslreports.com/forum/remark,13167102 timcuth : Noel, to put it simply, you are the man!

Tim]]> http://www.dslreports.com/forum/remark,13167102 Thu, 14 Apr 2005 08:18:43 EDT Re: Astrophotography, Soup to Nuts (long post) http://www.dslreports.com/forum/remark,13167097 n8crwlr : Excellent explanation of how to take the pictures. And I am sure most will agree, I am grateful you take the time to set it all up and take the pictures, they are spectacular.....]]> http://www.dslreports.com/forum/remark,13167097 Thu, 14 Apr 2005 08:17:31 EDT Re: Astrophotography, Soup to Nuts (long post) http://www.dslreports.com/forum/remark,13166367 Catman : A definite sitemark here....

Your work has been closely followed by my eyes. It is awesome and awe inspiring to see some of your images, they keep getting better. Thanks so much for the walkthrough of what it takes. One day I strive to get into this myself, just gotta save up for a suitable scope.]]> http://www.dslreports.com/forum/remark,13166367 Thu, 14 Apr 2005 02:19:26 EDT Re: Astrophotography, Soup to Nuts (long post) http://www.dslreports.com/forum/remark,13165012 Edit This : A profound thank you Noel. The information you have provided is worth it's weight in gold. Superb work and explanation.
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I post therefore I am.]]> http://www.dslreports.com/forum/remark,13165012 Wed, 13 Apr 2005 22:48:54 EDT Re: Sow's Ear to Silk Purse http://www.dslreports.com/forum/remark,13164954 NoelC :

said by Bruschi

:

Does the telescope automatically track the objects as they move through the sky?

Yep, and it doesn't do just one speed either. It will track the moon and even selected satellites. There's even a place on the Meade web site to get the International Space Station orbital numbers, though I haven't tried to track it yet.

-Noel]]> http://www.dslreports.com/forum/remark,13164954 Wed, 13 Apr 2005 22:43:00 EDT Re: Astrophotography, Soup to Nuts (long post) http://www.dslreports.com/forum/remark,13164386 overhill : You have shown us some amazing shots over the last few months Noel.

I am very impressed by your work with your new telescope and the resulting images. Thank you for the nice post and all the details. Keep the great stuff coming!]]> http://www.dslreports.com/forum/remark,13164386 Wed, 13 Apr 2005 21:42:24 EDT Re: Sow's Ear to Silk Purse http://www.dslreports.com/forum/remark,13163332 Bruschi : Thank you for the info Noel! Does the telescope automatically track the objects as they move through the sky?
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Fantastic job, Noel!]]> http://www.dslreports.com/forum/remark,13161979 Wed, 13 Apr 2005 17:11:14 EDT Re: Astrophotography, Soup to Nuts (long post) http://www.dslreports.com/forum/remark,13160787 JRSlater8 : I never truly understood what light pollution was before. Your example has made it quite clear (no pun intended). It's obvious that it takes some work and dedication to do this. Thank you for sharing.
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Be still when you have nothing to say; when genuine passion moves you, say what you've got to say, and say it hot. D. H. Lawrence (1885 - 1930) ]]> http://www.dslreports.com/forum/remark,13160787 Wed, 13 Apr 2005 14:59:44 EDT Sow's Ear to Silk Purse http://www.dslreports.com/forum/remark,13160700 NoelC : Just to illustrate some stages of image processing, and how much can be accomplished...

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-Noel

As out of camera
Light Pollution and Noise Reduction
Level Stretch, Color Enhancement
Final Polish

]]> http://www.dslreports.com/forum/remark,13160700 Wed, 13 Apr 2005 14:45:54 EDT Re: Astrophotography, Soup to Nuts (long post) http://www.dslreports.com/forum/remark,13160692 B52GUNR : I'd be interested in learning diffraction spikes, I'm guessing I could use it in night shots.

Gorgeous write up, Noel!]]> http://www.dslreports.com/forum/remark,13160692 Wed, 13 Apr 2005 14:45:18 EDT Re: Astrophotography, Soup to Nuts (long post) http://www.dslreports.com/forum/remark,13160682 Wass : Big Thanks Noel for the detailed and interesting instructions.
The diffraction spikes might be something good to learn too :D]]> http://www.dslreports.com/forum/remark,13160682 Wed, 13 Apr 2005 14:44:13 EDT Astrophotography, Soup to Nuts (long post) http://www.dslreports.com/forum/remark,13160240 NoelC : For the past 5 months I have been learning astrophotography, from soup to nuts. I invested in a good telescope this past Christmas - a Meade 10 inch LX200 GPS UHTC Schmidt-Cassegrain telescope with computer control and "goto" capability - fulfilling a lifelong dream to own such a fine piece of gear. As with daytime photography, there's always more equipment that can be bought, but with my Canon EOS-20D, some accessories, and the above telescope, so far I have been able to create some reasonably decent astrophotos.

In a recent gallery thread it was suggested (thanks Dan) that I write up a bit of a tutorial on what's involved in creating an astrophoto - it's really quite different from daytime shooting. Okay, here goes...

The Challenges

•Long exposures - well, it's night and things in the sky are pretty dim, so the BIGGEST challenge is in accumulating enough light to actually make a photo. Even more is required to make a good photo. Thus, one has to be prepared to take very loooong exposures with a camera that produces as little noise as possible. Dedicated astroimagers do this best, followed by the modern crop of digital SLRs.

•Light pollution - unfortunately, unless you're in a really rural, dark place, you probably have a good bit of light pollution in the sky. This tends to limit the length of exposures you can make, though interestingly it doesn't really mask out dim objects - indeed, sky light adds to the light coming from extraterrestrial objects, so it can be subtracted out digitally. However, having to combine more exposures of shorter duration causes extra work at the computer.

•Size does matter - a good telescope both magnifies objects and gathers as much light as possible. The larger the telescope, the more light it brings in, generally speaking. The challenge is in affording the largest telescope possible, not to mention carrying it around, setting it up, etc. I saved for years for my LX200. This is just like camera lenses - large aperture lenses are more expensive.

•Tracking moving targets - Things in the sky move relative to a point on the ground. The Earth is turning, and so things rise in the east, transit the sky, and set in the west. Thus, to make a long exposure, a telescope has to track an object across the sky. To make a sharp photo, this has to be done EXTREMELY well!

•Good seeing - obviously the sky has to be clear of clouds, and beyond that the clarity of the air, movement of the air, heat layers, humidity, dew... All these things can affect an image. Clear nights where the seeing is very good and the telescope stays clear of dew for long exposures are rare in most parts of the country. Not to mention mosquitos.

•Staying awake - one has to be prepared to stay up really laaaaate. I find Cuban coffee best for this. :) Obviously good seeing on Friday and Saturday nights is best.

Putting It All Together

Probably the best thing I can describe next is how it all actually happens. It takes a bit of planning, setup, and a fair bit of post processing to get good astrophotos.

A typical night of observing/shooting goes something like this:

1. Carry telescope in hard case and tripod in soft case outside. This stuff is quite heavy - the whole thing weighs in at upwards of 100 lb when it's together.

2. Carry camera bag outside, along with two different adapters to hook the camera to the scope.

3. Unpack everything, and set telescope up on its tripod in a place with a decent view of the sky. There are a fair number of pieces that have to go together (tripod, scope, control panel, spotter, microfocuser, star diagonal, eyepiece, power cord, etc.). I also have a little 12V rechargeable power tank that sports two car cigarette-lighter adapters, which powers everything.

4. Turn on the 'scope and start the alignment process. It finds magnetic north, level, and your location on the planet and exact time (via GPS), then slews (points) skyward at two different stars and asks you to fine-center them in the eyepiece. After that, you can punch in the location of what you want to see, or simply use the arrows on the controller to point the 'scope, and it slews under computer control. It tracks whatever you have it pointed at.

5. Remove the lens from the camera and connect the T-adapter (sometimes with f/6.3 focal length reducer screwed-in) to the 20D dSLR camera body. Also, plug in the TC80N3 remote shutter into the camera body.

6. Connect the camera assembly to the telescope in place of an eyepiece. Set the camera to Manual mode, and enable Mirror lockup.

7. Slew the 'scope to point at something bright, adjust main mirror telescope focus while looking through the camera's viewfinder, take some test shots. Tighten the main focus tension, then adjust fine focus with the electric "zero shift microfocuser" on the telescope. Repeat until stars are pinpoint sharp, or as sharp as viewing conditions permit (they don't look like pinpoints in long exposures if the atmosphere is making them twinkle).

8. Punch in the object you want to photograph and slew the telescope. You have to be careful to use the star diagonal (basically a right angle prism) if you're going to be shooting objects that are straight up or nearly so, because otherwise the camera would hit the telescope mount.

9. Check through the camera's viewfinder (if possible; very dim objects like galaxies simply don't show) to see if the object you're trying to photograph is properly centered, adjust as needed. If the object is dim, I take test shots and look at the review on the camera, then do fine positioning via the telescope controller for best composition.

10. Take multiple exposures of the same object, for later combination into the final image. I have enough light pollution here where I live that the longest exposure I can reasonably take on a clear night is 30 to 60 seconds at ISO 1600. I take a LOT of exopsures - from 10 to 100 - of the same object, for later combination in the computer. Some astrophotographers spend one or even several whole nights photographing one object!

11. Take the whole thing apart and bring it in at the end of the viewing session.

Post Processing

At the computer, combining multiple exposures digitally has the effect of averaging out the noise, which yields cleaner images. Some objects, such as the moon, can be taken with short exposures and low ISO, but most need looong exposures to get enough light for a good image.

There is software out there to help, but a lot of it is just careful manipulation in Photoshop. Adept removal of a base level of light pollution in the image makes a washed-out photo look dark and contrasty. Most people are surprised that long time exposures out of the camera look like this, because of the light pollution in the sky:

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There are quite a few ways to correct light pollution to make the image on the right; I prefer starting with a second layer set to "Difference" mixing, and the Dust and Scratches filter to create a color to subtract that matches the light pollution. The Threshold parameter can be set to help cancel out noise as well. Here's the sequence in more detail:

1. Duplicate image as second layer.
2. Go to 16 bit color (Photoshop CS only).
3. Dust and scratches filter, large radius, 8 or so pixels threshold.
4. Duplicate that result as a third layer.
5. Image-Adjust-Curves, set black point so that just a blob where the galaxy should be remains. You may have to click several times to get it as dark as possible.
6. Filter-Noise-Median 3 pixels.
7. Filter-Blur-Gaussian Blur 5 pixels.
8. Set top layer to "Difference" mixing.
9. Adjust top layer opacity so the field looks pretty flat.
10. Merge down.
11. Set top layer to "Difference" mixing.
12. Select lower layer.
13. Image Adjust Curves, increase black point of RGB to 5, B (blue) to 2. This makes the sky deep bluish-black.
14. Layer - Flatten.
15. Image-Adjust-Curves to brighten things up.

Given the dynamic range limitations of video displays, there are some techniques for making bright stars look brighter, and for bringing out color (stars are very colorful). I can write more on these techniques if you'd like. I sometimes also add diffraction spikes (the points on really bright stars) digitally in Photoshop via an action I've written. I think they just look good.

As you can see, astrophotography - or even just good old astronomy - is a pretty involved process.

Please, by all means, ask questions about parts of this that interest you or for which I wasn't clear.

-Noel


Before and After Light Pollution Removal

]]> http://www.dslreports.com/forum/remark,13160240 Wed, 13 Apr 2005 13:46:53 EDT