[Buddha Jones]

This is the result of a test shot using K10D with the Tamron 70-300mm @ 300mm paired up with the Tamron 1.4x TC and the Vivitar Auto 2x TC for a focal length of 840mm. I shot it in manual at f/4 for 1.5sec but accidentally shot it at ISO 800. This is a full frame resized to 25%. I think it did pretty well considering all the glass it had to go through. I will try it again another night at a better ISO and in a darker setting, some of my neighbors had some outside lights on.



Here is the same shot full crop of the moon.

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Last edited by Buddha Jones; 03-12-2008 at 09:41 PM.

[christinelandon]

That is a lot of glass to shoot through, Buddha. Considering that the moon is a moving object being shot from another moving object (the Earth), I suspect that you'll want to keep your ISO up and your exposure times down to the extent possible. Losing the light pollution will help some, as you indicate.

Let us see what you get; I love trying to "shoot the moon," myself! I've yet to have more than about 450mm FL to work with, and I'm far from satisfied with my attempts so far.

[falconeye]

Here is the same shot full crop of the moon.

Nice try! Good experiment.

However, your moon only has a pixel resolution of about 100 pixels. The moon has a diameter of 30' (0.5 degree), your resolution therefore is 20''.

The earth rotates by 15''/s or one of your effective pixels/ 1.5s

Any good lens with a FoV narrower than 2500 x 20'' or 14 degrees (about 135mm) would give the same resolution.


To get better pictures (a $1000+ telescope resolves at about 0.5''), say with 4'' resolution, your exposure time must be 1/4s or smaller (on a tripod), focal length about 500mm, and you should stack many pictures together in post processing. Underexposing is ok, cranking ISO up doesn't really help.

[m8o]

Buddha, with that magnification, with all due respect to what falconeye said, try it again either bumping up the ISO (but you were already @ ISO800, so maybe not higher then that for cleanliness) or open the shutter if you can, whatever you have to, to keep shutter speed at 1/10 second or faster. What you're seeing is 'blur' of the moving subject. The thing to consider is, the moon moves one full diameter in 2 minutes. The ideal, is to use a shutter speed as fast or faster then the moon will move in one pixel per photograph exposure time. What do I mean...

Ignoring that at this time and at our latitude of year (I'm on LI so near you) the moon travels at what, maybe about a 70 degree angel off a perpendicular line to the horizon, so the vertical pixel size the moon moves in the two minutes is really SIN(70) * "vertical pixels", not 1 * "vertical pixels"... But for ease of explaining...

The K10D has a vertical rez of 2592 pixels. 2592 pixels / 120 seconds = 21.6 pixels per second IF/when you use enough magnification to fill the entire frame top to bottom with the moon. Thus, a shutter speed of 1/25s will be fast enough so that the moon does not move 1 entire pixel during exposure. Faster is alway better ....

Now, in your image at that magnification, if the moon were full, it would be about 1/2 the frame height. So, how many pixels does the moon move in one second at that magnification? 1296/120 = 10.8 ... So a shutter speed of 1/15s will allow for an exposure where the moon moves less than 1 pixel within the exposure time. Any shutter speed slower will "shmear". Sin(70) * 10.8 = 10.15, so 1/10th will work to give you a "sharp enough" image. Even 1/4s as falconeye said will work, but the moon will move about 2.5 pixels during the exposure. That'll serve to actually "thicken-up" the shadows some.

I recently did the same, stacking my TCs and even adding a 1.7x, and had great results my 2nd time, and that's with having to press the shutter manually thus invoke shake. There was "shmear" here too but with the "almost fast enough" shutter, it was pretty "ok": https://www.pentaxforums.com/forums/post-your-photos/22470-waxing-crecent-lun...tml#post193964 With that shot @ f/3.2, 1/15s and ISO 800, I had a very good exposure. I didn't do any EV comp, and bumped brightness ever so slightly in post in Lightroom; even left contrast pretty much alone. I was surprised. I'll have to commit that to memory.

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Last edited by m8o; 03-13-2008 at 01:05 PM.

[Buddha Jones]

Man, I feel like I just got schooled, that is some killer information from both you guys, and although I kinda understood what you were saying falcon, m8o helped put it into layman terms for me, thanks a lot! I will give it a few more tries this weekend for sure.

[m8o]

Man, I feel like I just got schooled, that is some killer information from both you guys, and although I kinda understood what you were saying falcon, m8o helped put it into layman terms for me, thanks a lot! I will give it a few more tries this weekend for sure.

My pleasure.

BTW, Oh! You're in NC?! For some reason I thought you were in Brooklyn. Ok, so we're not at the same latitude.

[ftpaddict]

Sin(70) * 10.8 = 10.15

Headache headache headache!!

[falconeye]

and although I kinda understood what you were saying falcon, m8o helped put it into layman terms for me

I am glad you got some stuff to consider.

As for laymen's speech ... m80 only addressed one topic of my post: motion blur. And I thought you wanted to do the math yourself anyway to be convinced

Two other issues addressed were the limited resolution power you get from a lens and focal lenght longer than necessary.

I thought an improvement by a factor of five would be good enough to get you going. For this I recommended 1/4s. To exploit the K10D's resolution you need less than this, correct.

But with the glass you have available you will have trouble getting there anyway.

And do stack images! Underexpose and stack. Don't try make it all in one shot.


And remember: $1000+ telescopes (2000mm f/10) have diffraction-bounded resolution at maximum aperture which is 8 inch... So, use good glass not requiring you to step down too much. Without a telescope you won't be able to max out K10D's sensor resolution.

[m8o]

falconeye, so if I understand correctly, you are saying using say my voigtlander 125mm with its extremely high resolution, well focused, and image cropped, will yield the same/similar resolution if not more, as our stacked TCs and longer lenses filling up the sensor frame with more of the moon...?

[falconeye]

falconeye, so if I understand correctly, you are saying using say my voigtlander 125mm with its extremely high resolution, well focused, and image cropped, will yield the same/similar resolution if not more, as our stacked TCs and longer lenses filling up the sensor frame with more of the moon...?

That example is too extreme. In my first posting I said a crop from a 135mm would indeed have delivered the same (bad!) quality. I recommended to go for a 500mm lens and my figures were made to exploit this length. Teleconverters are ok to reach this length. They wouldn't help anymore to fill the frame with the moon.


The minimum you would need to fill the sensor is about a 2000mm f/10 lens with 8 inch diameter. Those are diffraction-bound at FULL aperture!! And resolve 0.5 arc seconds. One of 2500 pixels filling 30 arc minutes (the moon) is 0.7 arc seconds wide!!


And did I say that the atmospheric turbulences will destroy those top-notch resolutions anyway (called "bad seeing" conditions which are the normal)? And that you would have to use special tripods, and...


What I say then is this:
Give up in trying to shot the moon with full sensor resolution -- only astro-optical equipment can do so! I recommend to go to 1/4 of sensor resolution. And in this case I recommended to stack many 1/4s shots.

[Buddha Jones]

Ahhh.... ok, now I get your point.

[m8o]

and I. thanx for the follow-up.

[pixelsaurus]

This is a page from my incomplete geocities page, On it is a table for minimum exposure time, for use on a non driven mount, for keeping the moon sharp. ExposureTables
As for the exposure itself,the moon is essentially a daylight object ( it is,after all,almost entirely lit by sunlight). The sunny f16 rule does work, My preference is to use as long a lens as possible,low ISO and the highest shutter speed possible (sacrifice f/ratio for this one). Always use a tripod and self delay timer (2 secs ok),the latter helps minimise vibration. A cable switch will help minimze vibration as you don't get to touch the camera. If vibration becomes an issue,hang a plastic bag containg plastic bottles of water or sand from the leg braces.
To cure the neighbours light habits,all you need to do is make a long lens hood (black cardboard will suffice). Many excellent moon shots are made from city locations, Good hunting.
PS Full moon is the worst time to shoot,it is a low contrast object.

[falconeye]

ExposureTables

What a work! Thanks for drawing my attention to it. Excellent.

[jnorth]

To cure the neighbours light habits,all you need to do is make a long lens hood (black cardboard will suffice). Many excellent moon shots are made from city locations, Good hunting.
PS Full moon is the worst time to shoot,it is a low contrast object.

Or you could use a bb gun and say it was the 'other' neighbor.