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FORUMS Photo Sharing & Discussion Astronomy & Celestial 
Thread started 16 Jan 2013 (Wednesday) 00:52
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New member with a couple questions.

 
NavyDiver911
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Location: Kaneohe, HI
     
Jan 16, 2013 00:52 |  #1

Hello everyone!
I have a few questions regarding shooting the Milky Way. I hate to ask the age old question, but I feel I've exercised all my resources and have read 5+ hours every night for the past week and have yet to find a definitive answer. I have a Canon SX40 HS w/CHDK and can't find a great combination between exposure, f/stop and ISO to capture the Milky Way. My exposures have been anywhere from 15"-30" with an f/2.7-3.5 and varying ISO settings ranging from 600-6400 with a 10 second timer, but I'm getting a lot of noise every time and can't manage to get rid of it when I edit my photos in Lightroom.
I'm not achieving the deep rich colors I see in a lot of pictures, for instance: http://crdesignlab.com​/2010/08/23/the-milky-way/ (external link) <---This guy only used a gorilla pod. I've read all about equatorial trackers and barn doors, but if this guy can do it with a gorilla pod I should be able to do it with my Manfrotto tripod. I know I know his camera is far superior than mine...
Has anyone been able to capture the Milky Way using the SX40 HS w/CHDK successfully with only a tripod? I've read all over this forum and have used the search feature numerous times trying to find an answer. If I left out any important information I apologize. Thanks in advance for anyone who offers any advice! By the way, I drove two hours away from San Diego to Anza-Borrego State Park to capture these photos. Both are unedited and single captures.

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Gripped Canon 6D | 24-105mm f4L| Samyang 14mm f2.8 | Canon SX40 HS w/CHDK.
http://www.youtube.com …NavyDiver911?fe​ature=mhee (external link)
http://www.flickr.com/​photos/92695584@N07/ (external link)

  
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spoonofmilk
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Jan 16, 2013 03:48 |  #2

It looks like your issue, at least with the second photo, is still light pollution. Bear in mind the guy in your link was at 10,000ft and miles from built-up civilisation. In your shot you can clearly see the glow from a nearby city. That'll knock any detail from the milky way into a cocked hat!

There's also the time of year to consider - did you take these just recently? If so, the milky way is less vivid in the winter months, so I would imagine that with your gear you're better off trying again from March/April when it'll be a lot brighter in the night sky.

As for your settings... trial and error is always the best way, but generally as high an ISO you can get without going into crazy noise and a shutter speed compatible with your focal length would be good. The SX40 has a minimum focal length of about 24mm if I remember rightly, so you'd have to shoot at around 15 to 20 seconds to avoid star trailing.

Also... with your gear you might get better results from some stacking, but others can probably comment better on that... I've not tried stacking yet myself, so that'd be the blind leading the blind! :-)


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stickman513
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Jan 16, 2013 11:00 |  #3

Have you looked at Deep Sky Stacker (DSS)?
check out this link and see OP's website for Tutorial on using it.
This will help with signal / noise and bring more of the milky way out.


Doug
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430 EX II | Yongnuo Triggers | Manfrotto Legs | Lee & Marumi Filters

  
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NavyDiver911
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Jan 16, 2013 12:19 |  #4

spoonofmilk,
I knew he had an advantage because of his elevation. I was anywhere from 2,000-3000' above sea level and yes these photos were taken recently. You're right on about the minimum focal length of 24mm. I've calculated the longest I can leave my aperture open is roughly 20.8 seconds without star trailing. It's a basic formula I found online. 500 ISO/24mm (SX40 HS focal length). As far as the accuracy of this equation, I'm not sure, but I'd rather play it safe and take shorter exposures and stack my photos in DSS.
Stickman,
Yes I actually found out about DSS a couple days ago and tried merging a few pictures together to try it out. This was my first attempt at shooting the Milky Way and second time shooting stars so I didn't expect to "nail" it the first time. I think what I'll do next time is shorter exposures (15-20 seconds) with an ISO around 500-800 with an f/3.5 and make minor adjustments. From there, I'll set my intervelometer and take at least 8 photos and then stack them in DSS to see if that yields me better results. The pictures above were taken an hour or two after the sun went down, maybe 7-8pm. Thanks for both of your replys! I am very new to shooting at night and have a lot to learn so I appreciate everyone's patience with me.


Gripped Canon 6D | 24-105mm f4L| Samyang 14mm f2.8 | Canon SX40 HS w/CHDK.
http://www.youtube.com …NavyDiver911?fe​ature=mhee (external link)
http://www.flickr.com/​photos/92695584@N07/ (external link)

  
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SteveInNZ
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Jan 16, 2013 13:50 |  #5

There's no escaping it - He has a camera with a big sensor, low noise electronics and a fast lens. You have a little iddy-biddy sensor and that makes all the difference in these types of shots.
Also, the milky way is a bit of a difficult target without dark skies as the contrast between it and the background is quite low.
But with a bit of effort, there are things that you can do to get the most out of what you have.

Since you mention CHDK, I assume that you are shooting in RAW. If not, you should be.
To find your optimum camera settings, do some test shots, have a close look at the results and adjust accordingly.
Start with the ISO turned up to the top, aperture wide open and the highlight blinkies on. Take a shot of somewhere in the sky that has plenty of bright stars, but isn't directly north. Your exposure should be long enough to just get some blinking on the brightest stars.
Look at the resulting image and zoom right in to the middle and then each of the corners. You are looking for blue or purple rings around the stars or odd shaped stars (look like seagulls or comets) in the corners. If either are present, you have the option to close the aperture down one stop to fix them. You'll have to decide if they are acceptable to you or not. (Your 5D comparison guy doesn't seem to mind).
Now point the camera to the area of sky you want to photograph and leaving the other settings the same, vary the shutter speed until you have the amount of trailing that you are happy with. Check each corner as they'll be different. Don't worry about any over exposure, you just want to know the maximum shutter open time.
Now using the aperture and shutter speed you've found, turn down the ISO until just the brightest stars are blinking if you are in a dark sky. If you have some background light pollution, then watch the histogram and turn down the ISO until the left side of the main peak is just separated from the left axis.
Now take multiple shots at those settings. DSS calls these "light frames". When you are done, put the lens cap on and take lots more shots with exactly the same settings. These are "dark frames". Take at least 20.
Stack these shots in DSS. I haven't used CHDK for a long time, but you used to need to convert the CHDK RAWs to TIFFs for DSS. If that's still the case, you want a "Linear Tiff".

If you are going to use DSS, you are probably better to shoot your milky way without a foreground object (and maybe photoshop in your tree afterwards if you like). Sometimes it works and sometimes it doesn't.

Steve.


"Treat every photon with respect" - David Malin.

  
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