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dgdg
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Re: 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 count time downer.
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



Aug 08, 2016 at 07:10 PM





  Previous versions of dgdg's message #13673580 « Dumb a7R astro questions »

 




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