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Archive 2016 · Dumb a7R astro questions

  
 
Schlotkins
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p.1 #1 · p.1 #1 · Dumb a7R astro questions


For the first time, I am going to try to shoot the Milky Way at the end of the month with the new moon. Of course, given i've never done this before, I'd read around the Interwebs to get tips (500 rule, etc.) but I have a few A7R specific questions.

1) I usually shoot with LENR turned off so I get 14 bit RAWs rather than 12 bit. Is this still OK? Per usual my exposures untracked will probably be ISO3200, 30sec (w/ my 14 2.8) Should I turn it on? Take a black frame? (I don't know how to best do this either...)

2) Similar to #1, if I get a tracker and do say 5 minute exposures (ISO 800, 5 min) what changes should I make to the camera settings? I know i have to use bulb mode and time myself.

(On an aside I have no idea if I still shoot at 2.8 to get more light or not with a tracker ....)

3) Should I have AWB on?

If you have any other tips of course I'd love to hear them. I will either shoot with a Samyang 14 2.8 or a Nikon 14-24 2.8. I may bring the Samyang 24 1.4 if I can find a good copy. Not sure if the Sigma 20mm 1.4 is good or not. I also have a 35mm 1.4 to bring but that is probably too tight.

Thanks,
Chris



Aug 08, 2016 at 02:45 PM
klasGelinder
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p.1 #2 · p.1 #2 · Dumb a7R astro questions


Sony a7 series are very bad at astro photography whenever bulb mode is used due the star eater algorithm applied to the images and that cannot be turned off.

See
https://www.dpreview.com/forums/post/55841466/
or
http://www.cloudynights.com/topic/498339-sony-a7s-star-eater-algorithm/



Aug 08, 2016 at 03:13 PM
pizdets17
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p.1 #3 · p.1 #3 · Dumb a7R astro questions


all the data on this is a year and a half old, im guessing the 3 firmware updates might have fixed this issue as I do not notice any difference on my a7r2 and I shoot 2 min exposures on my iOptron tracker all the time.
Lake McGregor by dmitri voyevoda, on Flickr



Aug 08, 2016 at 03:47 PM
dgdg
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p.1 #4 · p.1 #4 · Dumb a7R astro questions


klasGelinder wrote:
Sony a7 series are very bad at astro photography whenever bulb mode is used due the star eater algorithm applied to the images and that cannot be turned off.

See
https://www.dpreview.com/forums/post/55841466/
or
http://www.cloudynights.com/topic/498339-sony-a7s-star-eater-algorithm/


That's an odd exaggerated comment.
Looking at a couple of my A7r1 images, I now regret ever using it.
I'll reply to Chris's questions in a separate post.
http://davidsphotography.zenfolio.com//img/s7/v169/p1102015759-5.jpg

http://davidsphotography.zenfolio.com//img/s12/v172/p1404630115-5.jpg



Aug 08, 2016 at 04:27 PM
pizdets17
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p.1 #5 · p.1 #5 · Dumb a7R astro questions


couple great images there, but you should prob throw the camera out as it might have eaten some stars...By the way, what is involved compositing the meteors? Want to to this on the 11th for the Perseids..


Aug 08, 2016 at 04:42 PM
Vcize
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p.1 #6 · p.1 #6 · Dumb a7R astro questions


Regarding #1, to take a dark frame you just put the lens cap on and shoot a shot with the same exposure settings (you don't have to do this with every shot, just every few dozen minutes or so as the sensor temperature changes). Then in photoshop you can put that frame on top as a layer and change the blend mode to subtract.

This time of year I would recommend either taking a dark frame (preferred) or shooting with LENR on (if you want to save time in post in exchange for more time in the field and 12 bit shooting). With some cameras or if it is cold out it often is not an issue, but with the A7x bodies in warm temperatures long high ISO exposures will start to show serious thermal noise issues quite quickly as the sensor heats up.

Here is a dark frame from one of my recent shoots with the A7r. Note that it is actually even worse in the raw file as the jpg conversion compresses some of it.

https://dl.dropboxusercontent.com/u/4716025/a7r/huntsville-cow-barn-02433.jpg



Aug 08, 2016 at 05:09 PM
WestTexas Sky
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p.1 #7 · p.1 #7 · Dumb a7R astro questions


I use my A7R for nights all the time.

Keep it simple to start and skip the tracker, just use your camera.
Camera, tripod, remote release and flashlight are the basic tools.

I find that I need to use the flashlight to focus with the A7R as it lacks the night sensitivity of the A7S. Find infinity and you should be good. Make sure AF is off.

I go with neither High ISO Noise Reduction nor Long Exposure Noise Reduction.

My basic formula for a 14mm is:

ISO 6400
30 seconds
F/2.8

If your exposure is too bright then drop the exposure to 20 or 25 seconds to limit any star trails.

If you think the exposure is too dark on the stars you can push that up 1-2 stops in Lightroom. I usually use the brush and just bump the sky if needed.

I also add clarity, vibrance, and a little saturation.

I also shoot RAW and auto WB. I tend use around 4000 but can vary depending on any light pollution.

In PS the main thing to do is select just the sky. Feather 200px along the edge. Do a Curve which really makes it pop.

You should get some nice results.

Now if you have a second camera, tripod and lens for night, set that one up with an intervolometer. Program in your settings and let it run for 2-3 hours. That will give you images for a time lapse or to combine into a star trail.

Finally check out Lonely Speck for more tips. Ian Norman runs a great site dedicated to night photography.

Have fun and good luck.



Aug 08, 2016 at 06:06 PM
dgdg
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p.1 #8 · p.1 #8 · Dumb a7R astro questions


1) I usually shoot with LENR turned off so I get 14 bit RAWs rather than 12 bit. Is this still OK? Per usual my exposures untracked will probably be ISO3200, 30sec (w/ my 14 2.8) Should I turn it on? Take a black frame? (I don't know how to best do this either...)

Don't fret over 14bit vs 12bit. You have a couple main options. One, if you are taking just a single image, then LENR can be a time saver for a nice image. I prefer to take half a dozen images in RAW (LENR off) and stack them in Deep Sky Stacker. Then I use PS to process the image. I can apply noise reduction to the deep sky and avoid extra contrast. For the milky way I can increase detail and use less noise reduction.

2) Similar to #1, if I get a tracker and do say 5 minute exposures (ISO 800, 5 min) what changes should I make to the camera settings? I know i have to use bulb mode and time myself.

You don't change much other than bulb mode. Buy a cheap intervalometer on Ebay to count for you. Enjoy observing the night sky instead of staring at a the time.
In a dark sky these are my typical settings - ISO 800, f/2.8, exposure time ~4.5 minutes, RAW, LENR off, High ISO NR off.

(On an aside I have no idea if I still shoot at 2.8 to get more light or not with a tracker ....)

Stay at f/2.8 so you get as many photons on your sensor as possible.
Usually you keep a good lens wide open unless you are forced to stop down for sharpness or coma. That is the beauty of the Samyang 14mm - it's great wide open. Once you take your first exposure, look at your histogram. You want the luminence peak to be at about 30% from the left. It will look too bright, but ignore this and simply adjust your black point in post. This tip helps greatly with noise.

3) Should I have AWB on?

You are shooting in RAW right?

If you have any other tips of course I'd love to hear them.

The Samyang 14mm is a great astro lens.

The A7r1 does not heat up appreciably in the summer with repeated long exposures. I've shot 4-5 minute subs for a couple hours and my last image is as good as my first. My Virginia Perseids meteor radiant shows a clean file. It was a hot day. The A7r2 is a different story and not as good in this area.

Focus on a bright star or planet with magnified live view, manual focus, then tape down the focus ring with gaffer's tape. Don't trust any other method of focusing on your milky way.

If you are out for a long time tracking, you may develop dew on the front element. You can use a thin ski sock, shove in a couple small hand warmer packs, then tie it around the distal part of the lens barrel. Or get yourself a dew heater controller and strap from Thousand Oaks. http://www.thousandoaksoptical.com/dew.html
Once your lens develops dew, it is too late to heat it up. You have to apply the hand warmer packs or dew strap after you have taped down your focus ring.

Enjoy!
Looks like clouds and rain for me this year.

David


Edited on Aug 08, 2016 at 06:57 PM · View previous versions



Aug 08, 2016 at 06:10 PM
dgdg
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p.1 #9 · p.1 #9 · Dumb a7R astro questions


WestTexas Sky wrote:
I use my A7R for nights all the time.

Keep it simple to start and skip the tracker, just use your camera.
Camera, tripod, remote release and flashlight are the basic tools.

I find that I need to use the flashlight to focus with the A7R as it lacks the night sensitivity of the A7S. Find infinity and you should be good. Make sure AF is off.

I go with neither High ISO Noise Reduction nor Long Exposure Noise Reduction.

My basic formula for a 14mm is:

ISO 6400
30 seconds
F/2.8

If your exposure is too bright then drop the exposure to
...Show more

The A7r1 is a great astro camera.
Keep it simple is good.
Everything is harder alone in the dark with animals making various noises.

I have no problems repeatedly focusing on a bright star at night with the A7r1 in magnified live view. It is very easy. Turn the camera to Bulb, aperture open, and ISO 6400. Then make sure you turn the focus ring close to infinity or you wont' see anything on your screen. Out of focus stars disappear. Fine tune the focus for the smallest star possible. I am envious that I cannot see the milky way on my screen like the A7s.

I would strongly suggest a different exposure method using the following sequence to optimize your signal to noise ratio. Open the aperture as wide as IQ permits. Use the ~500 rule to set your maximum shutter speed. Then ADJUST your ISO to produce a luminence peak at approx 30% from the left. Don't change your shutter speed or aperture for exposure. Adjust the ISO.
If you are tracking, set the ISO to 800 and adjust the shutter speed to achieve the desired luminence peak of 30%.

A properly exposed night sky without any additional light source (city glow, moon, street lights, etc) should result in bright stars that are not overexposed and deep sky that needs a little adjustment in the black point to darken. If you push your exposure brighter anywhere, you worsen noise unnecessarily. Aim for the peak at ~30%.

+1 to Lonely Speck.

Here is a jpeg from RAW straight out of camera with the only vignetting correction. A7r1, Samyang 14mm, f/2.8.
This is pretty good detail for the stars. There is even a supernova in Sagittarius. Anyway, this is how bright the image should appear to optimize your noise. With black point adjustment your stars will remain bright but the deep sky will get cleaner instead of noisier.

http://davidsphotography.zenfolio.com/img/s/v-2/p1776311306-5.jpg



Edited on Aug 08, 2016 at 06:52 PM · View previous versions



Aug 08, 2016 at 06:29 PM
dgdg
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p.1 #10 · p.1 #10 · Dumb a7R astro questions


pizdets17 wrote:
couple great images there, but you should prob throw the camera out as it might have eaten some stars...By the way, what is involved compositing the meteors? Want to to this on the 11th for the Perseids..


Thanks. Hope you have some nice skies this week.
There is more than one way to make a radiant composite. I took advantage of my tracker.

1. Foreground, low iso, high f-stop, twilight, 14mm
2. Background sky: ISO 800, f/2.8, ~4.5 minutes, 14mm, Astrotrac. At ISO 800, f/2.8, you will not capture any meteors!
3. Meteors: Continue tracking, ISO 5000, f/2.8, ~30 seconds, 14mm, Astrotrac. The meteors are brief, hence your exposure for them is independent of shutter speed.

In PS I blend 1 & 2 for color and overall luminence.
Then I sort all my Meteor exposures flagging any with a meteor.
Use a color picker on the deep sky and Info tab to make sure the meteor exposures match the Blend.
For each meteor image I create a mask and paint the meteor onto the blend. You could also create a luminence mask and paint out everything but the meteor. The former seemed a little faster for me.
Since I'm using a tracker the whole time, all my images are already aligned relative to the radiant. Painting the meteors onto the background blend is fairly easy.
If you are not tracking, you can align each image with the difference mode. Pleiades and Adromeda should get you aligned well enough. If you are off the radiant, just pick a couple prominent stars to align.

Clear skies!
David




Aug 08, 2016 at 06:42 PM
pizdets17
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p.1 #11 · p.1 #11 · Dumb a7R astro questions


Thanks for this! How do you get past the confetti problem with such long exposures? I find anything over a minute has blue/red pixels without LENR


Aug 08, 2016 at 07:51 PM
JimUe
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p.1 #12 · p.1 #12 · Dumb a7R astro questions


there's no dumb questions, but experience is education.

i did this 4 years ago on my a900 + samyang 14/2.8. 42 seconds @ ISO-6400
https://c2.staticflickr.com/8/7215/7253896496_15b93378a7_o.jpg


i don't know bout a7 but for DSLRs, a tip on the samyang, know exactly where infinity is on your focusing ring in case you can't focus using liveview in the dark and bring a stopwatch for bulb exposures.



Aug 08, 2016 at 07:52 PM
smpetty
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p.1 #13 · p.1 #13 · Dumb a7R astro questions


Great thread!


Aug 08, 2016 at 08:00 PM
dgdg
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p.1 #14 · p.1 #14 · Dumb a7R astro questions



pizdets17 wrote:
Thanks for this! How do you get past the confetti problem with such long exposures? I find anything over a minute has blue/red pixels without LENR


At iso 800 for 4 minutes, I import to lightroom and it isnt there on the a7r1.
See my 4min exposure above exported from LR to jpeg with only vignetting corrected.
Same thing with my 5d3.
Of course stacking helps further.



Aug 08, 2016 at 09:04 PM
Schlotkins
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p.1 #15 · p.1 #15 · Dumb a7R astro questions


Amazing information. Thank you all got taking the time to post!! I'm going to hit a few different spots in 3 or 4 nights so hopefully by the end I can get some pictures at least half as good as the ones posted!


Aug 08, 2016 at 09:27 PM
Landscapist
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p.1 #16 · p.1 #16 · Dumb a7R astro questions


I suggest you stick with ISO 3200 and pull the exposure by 1 to 2 stops in Lightroom instead. Google A7R ISO invariance.


Aug 09, 2016 at 12:47 AM
dgdg
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p.1 #17 · p.1 #17 · Dumb a7R astro questions


Landscapist wrote:
I suggest you stick with ISO 3200 and pull the exposure by 1 to 2 stops in Lightroom instead. Google A7R ISO invariance.


I did and for the A7r1 (first google page) I don't see it listed where one can shoot at 800 ISO, 30 secs, then push it to 3200 ISO and have nearly equivalent detail and noise.
At 100 ISO, I certainly enjoy pushing landscape shadows liberally even though bracketing still provides a little more detail. At higher ISOs?
Although I already have tried and true advice for our OP, I'm interested in learning more. Since you have researched this already, could you provide your link or post relevant examples? It would open new doors for me with astro.

David




Aug 09, 2016 at 06:28 AM
Schlotkins
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p.1 #18 · p.1 #18 · Dumb a7R astro questions


I actually have 2 A7r... maybe I'll set one up with star trails while I try to shoot non-star trails with the other.

OK a few more dumb questions:

1) For the foreground, do you usually take a super long exposure to blend in when it's completely dark or take one at dusk and then use that shot for the foreground? I guess you could use a spotlight or flashlight to try to light it up as well...

2) I'm using Stellarium with the GPS of where I am going to be to get times/compass direction for the MW. So for example at 10:30 it will run from 170 to 190 (i.e due south) and then on the equatorial grid stretch from about -30 to 0. it should be pitch black so hopefully I can see the milky way with the naked eye but is there something I can use to see where the camera is pointing on the equatorial grid?

3) Any suggestions on lanterns/head lights? I ordered a Intervalometer as suggested.

Thanks again for all your super helpful comments!
Chris




Aug 09, 2016 at 08:15 AM
Vcize
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p.1 #19 · p.1 #19 · Dumb a7R astro questions


dgdg wrote:
The A7r1 does not heat up appreciably in the summer with repeated long exposures. I've shot 4-5 minute subs for a couple hours and my last image is as good as my first. My Virginia Perseids meteor radiant shows a clean file. It was a hot day. The A7r2 is a different story and not as good in this area.



I would disagree with this. The A7r may handle lower ISO long exposures on a tracker fine, but when you're not on a tracker and need to shoot at higher ISOs the sensor starts showing problems with thermal noise due to heat very quickly on a warm summer's evening. Note the dark frame I posted further up in the thread which was maybe 30-60 minutes into a shoot with exposures typically around 15s ISO6400.



Aug 09, 2016 at 08:37 AM
dgdg
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p.1 #20 · p.1 #20 · Dumb a7R astro questions


OK a few more dumb questions:

1) For the foreground, do you usually take a super long exposure to blend in when it's completely dark or take one at dusk and then use that shot for the foreground? I guess you could use a spotlight or flashlight to try to light it up as well...

Super long night time foreground shots usually don't look that good IMO. I avoid them.
Some people are very good at light painting. I'm not one of them. It's a skill and the better shots I see involve multiple static lights, not flash lights or car lights. I like to take a foreground shot during the brighter part of shadowless twilight with a low iso, high f-stop.
My twilight foreground shots are generally under 30 secs, ISO <800, f-stop 8 or greater depending on my dof.
You can take advantage of the setting or rising moon for a nice shadowless foreground too.

2) I'm using Stellarium with the GPS of where I am going to be to get times/compass direction for the MW. So for example at 10:30 it will run from 170 to 190 (i.e due south) and then on the equatorial grid stretch from about -30 to 0. it should be pitch black so hopefully I can see the milky way with the naked eye but is there something I can use to see where the camera is pointing on the equatorial grid?

A 'dark sky' is actually quite bright. You may not see the walking trail well but the milky way will be readily seen by the naked eye and easy to frame in your camera after a couple test shots. No fancy equipment needed. Certainly it is nice to look at a map and stellarium so you know how you will frame your comp in advance.

3) Any suggestions on lanterns/head lights? I ordered a Intervalometer as suggested.

It's easy to get lost a night even on small trails.
Get a super super bright headlamp and a spare charged battery.
Make sure you can get back to your car.
It gets cold at night, colder than you think.
Also get a red light for your work onsite. White light blows your night vision and it takes a while for it to return.







Aug 09, 2016 at 08:51 AM
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