Mars close to Earth right now

Discussion in 'Casual Photo Conversations' started by sjmurray, Aug 3, 2018.

  1. Just check the headlines. Mars is as big and bright as can be right now. Here in Minnesota it is hanging in the Southern sky at midnight glowing red and looking much bigger than any star. I first looked at it with binoculars, then grabbed my Nikon D7100 and used my 18-105 lens, manual settings and focus. It resulted in this photo. I'll bet some of you with longer lenses could get some really nice images right now! 20180803_3551.jpg
     
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  2. I am not to far from Grover's Mill, NJ, that might be a fitting site to try to capture some images of Mars. Link
     
  3. Thanks for the heads up SJ. Well, I got the photo. This is as good as I could get with 840mm and a 42 megapixel sensor.
    Mars 2018-08-05.JPG
    While outside of the car setting up the tripod, I thought I could hear the radio announcer say we interrupt our program with this special bulletin from the Intercontinental Radio News. At twenty minutes before eight, central time, Professor Farrell of the Mount Jennings Observatory, Chicago, Illinois, reports observing several explosions of incandescent gas, occurring at regular intervals on the planet Mars. The spectroscope indicates the gas to be hydrogen and moving towards the earth with enormous velocity. Professor Pierson of the Observatory at Princeton confirms Farrell's observation and describes the phenomenon as (quote) like a jet of blue flame shot from a gun (unquote). ;)
     
    Last edited: Aug 5, 2018
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  4. Um, no. There is no way you got that photo with that equipment, whatever the EXIF says. Obvious Photoshop is obvious.

    Thanks for the laugh!
     
  5. chulkim: I did lighten the sky surrounding Mars to make the stars more visible. Otherwise it was a straight shot with minor adjustment in acr. Here's what it looked like with no photshop. I shot in RAW, iso 1250, 125 sec, f8, hand held with image stabilization on. I'm interested in knowing why you think it was not a straight shot. Mars is very close to Earth right now and very large in the sky. 20180803_3551b.jpg
     
  6. sjmurray, simply because that lens and sensor could not possibly resolve Mars so well as the photo shows.

    Let's compare your image with one that I took a few days ago with a 70-300mm lens on my D810 at 300mm and f/8. This is the newest, AF-P FX lens, which is known for being very sharp at 300mm. Below are cropped screenshots of both your photo and mine at 800% magnification:

    Your photo:
    Screen Shot 1.png

    My photo:

    Screen Shot 2.png

    Your Mars is both larger and more detailed than mine. Count the pixels: your Mars is about 17 pixels across, while mine is only about 12 across. Your D7100 has a pixel pitch of 3.9 µm vs my D810's 4.87 µm, which means that, given the same focal length, a detail (such as Mars) on my sensor will cover 25% fewer pixels in any dimension than the same detail on your sensor. But that's if the focal lengths are the same. In actuality, the focal length I used is almost three times the focal length you used. Thus, by all rights, my Mars should have 2.25 times as many pixels in a given dimension as yours, not 30% fewer!

    The only way I can figure your picture came from your camera/lens combo is if you enlarged just the part of the photo containing Mars (which would have originally been a few pixels across) using one of Photoshop's interpolating scaling algorithms (such as Bicubic Smoother) and pasted that back on top of the original photo, which was not enlarged. But that is nothing like the image your camera captured.
     
  7. Interesting! I think you're calculations are off. I did not do anything except crop the image and like I said, brighten the stars around Mars. That's it. I guarantee there was no cutting and pasting. I sharpened a little. You should get a D7100 and the 18x105 kit lens like mine and do a similar shot. My particular lens is a sharp one as far as kit lenses go. I tried it with my manual pre AI 105 and it wasn't as sharp. Maybe some other folks will try it with different set ups. I'm surprised there hasn't been much interest in Mars being so close and easy to photograph right now.
     
    Last edited: Aug 6, 2018
  8. Looking at the image taken one minute later, it is much smaller! Maybe my first posted image was less in focus and thus appears bigger.
    Check out this one taken with the same settings as the first one but just a minute later and perhaps with slightly different manual focus. 20180803_3553.jpg
     
  9. I'd be interested to know what others think, but I doubt anybody else is paying attention! Oh well. I do enjoy a friendly argument.
     
  10. chulkim, what does your Mars look like at 100 %
     
  11. Watching......
     
  12. Oops, that did sound kind of weird! I'm still wondering why nobody seems to be wanting to try a shot at photographing Mars. Its right out there every night for a while.
     
  13. With the limited equipment I have a picture of the sky without all of the magnification with an interesting horizon would be the best I could do.
    It would look more or less like a star.
     
  14. Granted, Mars is near opposition and appears bigger than it usually does, but it's still mighty small at only 24 arcseconds. With a 105 mm lens, it would make an image about 12 micrometers across, or about 3 pixels on the D7100 sensor. Being orange, it should also show some color. In Minnesota, Mars is only going to get 20 degrees or so above the southern horizon, so there may be some atmospheric degradation of the image.

    I suspect we are seeing either a focusing problem, or an object that is not Mars.
     
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  15. I saw it through my telescope! I didn't open a window, though, because I didn't want the 'skeeters to get in. It was big even without the telescope.
     
  16. This is a 200px crop from the center of my photo at 100%:

    DSC_2774.jpg

    Quick! Someone call NASA!
     
  17. "I suspect we are seeing either a focusing problem, or an object that is not Mars." It was Mars, since Jupiter was already too low to see from where I was at that late an hour. chulkim's image is a little bigger than mine on my second shot posted, which you would expect. I think my first example probably was a little out of focus and made the planet look bigger.
     
  18. FWIW, I believe you entirely. As you say it could be oof a little. Change focussing ring from infinity to 58 million km!
     
  19. Most lenses focus past infinity in order to accommodate manufacturing tolerances. aperture focus shift and temperature effects. It is especially true for AF lenses, which work best if there is some overshoot in the mechanism. It also occurs in prime lenses, even some very good ones. Perhaps it wasn't important before, but when resolution extends down to the pixel level, even small errors become significant (in the statistical sense, distinguishable from normality).

    I don't have an astronomical telescope, but I do have a good, 40x spotting scope. The disk of Mars, bands of Jupiter and the rings of Saturn are visible, but poorly. That would be equivalent to a 2000 mm lens. That doesn't begin to address atmospheric conditions.
     
  20. As stated, the atmosphere is the killer.
    Dirty hot air is the enemy.
    High in the sky late on a cold clear night after a rain is best.
    A simple pair of 50x binos with large objective glass on a tripod makes for excellent night viewing.
    Sarurn’s rings, Jupiter’s moons, Orion’s nebula with a little averted vision, all make for great bino viewing.
     
    Last edited: Aug 7, 2018

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