Red ring around moon


Link Posted 02/11/2009 - 23:11

Why do I have a red ring around the moon ???This was taken just before it got dark...It is untouched...
This one here I shadow with some ligh same shot...

rosolution 3872x2592
orientantion normal
flash not used
focal lenght 200.0mm
35mm 300mm
exp time 0.011s (1/9)
aperture f/4.0
ISO 800
expsure aperture priorty
metering mode matrix
used Takumar -A zoom 1:4 70-200mm
tryed out my tripod.


Link Posted 02/11/2009 - 23:21
It's a lens abberation possibly made worse by atmospheric pollution.

The lens you are using was not designed for digital imaging and although a respectable performer it may show its heritage under extreme conditions such as the one presented here.
Best regards, John


Link Posted 02/11/2009 - 23:36
Thanks...pollution you might know the lens was give to me by one of our members... Don...maybe I should just used it under good condition...I think it better then having no zoom 200 lens...Its old, yes? So when would I get the most use out of this lens or how??

Still learning darlene


Link Posted 02/11/2009 - 23:41
Hey Darlene....can you take another picture with your 50mm lenses...and compare them...Oh ya, did you use a flash???


Link Posted 02/11/2009 - 23:59
Ok I will try that...Will put them on tomorow I use up my gallery shots...No I did not use my is there under 2 shot


Link Posted 03/11/2009 - 00:07
Yes, it's an old lens, but perfectly useable for general subjects.
Best regards, John


Link Posted 03/11/2009 - 06:54
Perhaps another reason the aberration appears to be very pronounced is that the moon itself is very overexposed in your image. That would certainly make it appear worse than normal.

The moon never appears as just a white dish, as it does here.

Start with the sunny 16 rule and set aperture to f16, shutter speed to 1/125, ISO to 100 and adjust from there.
Peter E Smith

My flickr Photostream


Link Posted 03/11/2009 - 08:06
Don't let the apparent failure of shooting the moon with this lens put you off using it.

I still haven't got a decent moon shot despite dozens of attempts using various lenses.

You may find the lens more suited to mid-distance shots, bird shots, in fact anything else, but not the moon. Unless you can sort out exposure etc!
Cheers, HG

K110+DA40, K200+DA35, K3 and a bag of lenses, bodies and other bits.

Mustn't forget the Zenits, or folders, or...

I've some gallerieshere CLICKY LINK! and my PPG entries.


Link Posted 03/11/2009 - 11:42
I've had no luck with taking pictures of the moon with a digital camera, but had some decent shots with my old ME Super. I can't explain this, but have a sort of theory.

The problem seems to be that, in order to get a clear image, a small aperture is required, but that means a longer exposure and the moon moves a bit during this time. Using a higher ISO with a faster exposure creates a very noisy pic, which effect is not seen on film. the longer the focal length of the lens, the worse the problem.

I've seen some fabulous shots of the moon by other photographers, and I wish I could afford their kit.
Pentax K10 + Pentax 18-55 + Sigma 28-135 + 50-500 + a large bagful of accessories.

I'm not young enough to know everything (Oscar Wilde)


Link Posted 03/11/2009 - 11:53
The moon moves quite quickly, so a shutter speed maybe of 1/125 sec could be needed. However, the moon is also very bright, which shouldn't be a problem.

Unless the moon almost fills the frame then some exposure compensation will be needed as the camera will try to lighten all the black sky that surrounds it. This will over-expose the moon.

Alternatively, a spot measurement of the moon may help, adding 1 stop to make sure it doesn't end up grey!

Other than that a very sturdy tripod will be essential. And a very long lens!
Best regards, John


Link Posted 03/11/2009 - 13:01
johnriley wrote:
The moon moves quite quickly, so a shutter speed maybe of 1/125 sec could be needed.

It doesn't have to be this short.

There are 86,400 seconds in a day, during which the Earth rotates 360 degrees.

So the moon moves across the sky at 360/86400 = 0.0042 degrees per second.

Now, the angle of view of a 400mm lens on a K10D is 3.44 degrees, measuring horizontally across the sensor.

So in a second, assuming the camera is set up to have the moon track horizontally across camera's field of view, the moon moves 0.0042 degrees, which corresponds to:

(0.0042/3.44) x 3872 = 4.7 pixels, let's call that 5.

So for movement blur to be less than half a pixel (a tenth of 5), you need an exposure of a tenth of a second or shorter. I usually go no slower than 1/15s to be on the safe side. (I think you'd be hard pushed to distinguish a 1/3 pixel movement blur from other effects in the image, such as lens aberration, imperfect focusing, camera shake, and atmospheric distortion, to name but a few!!)

For shorter focal lengths than 400mm, you can get away with exposures a bit longer than this.

1/125 however, is a lot shorter than you need.
Pentax K-3, DA18-135, DA35 F2.4, DA17-70, DA55-300, FA28-200, A50 F1.7, A100 F4 Macro, A400 F5.6, Sigma 10-20 EXDC, 50-500 F4.5-6.3 APO DG OS Samsung flash SEF-54PZF(x2)


Link Posted 03/11/2009 - 13:56
At 200mm you can go as long as 1 second for critical work, 4 seconds if some blur is acceptable.
Full moon, start with f16 and 1/125, and make adjustments as needed.
The red ring is chromatic aberration caused by the design of the lens.
Try stopping down when shooting very bright subjects.


Link Posted 03/11/2009 - 14:36
Those are JPG images - what are the original PEFs like?

Being reduced in size means that the software needs to calculate what the transition pixels are and having overexposed white and underexposed black could easily result in that type of effect.

As it is all round it is unlikely to be caused by the moon's transition which is also proven by the maths in an earlier post.

Is there a way that Darlene could post the original unprocessed file - maybe a board member with a website could provide space?
K20D, *istD, MZ-S, Super-A, ME Super, MX
DA* 16-50, DA* 50-135, DA* 300,
DA 50-200, FA 24-90, FA 20-35,
M 400-600, A 50 f1.4, A 28 f2.8, A 70-210, M 35-80, M 50 f1.7
A x2S teleconverter and a few others ...


Link Posted 03/11/2009 - 14:40
greyhoundman wrote:
At 200mm you can go as long as 1 second for critical work

At 200mm on a K10D, the angle of view is 6.87 degrees. A one second exposure is therefore 2.4 pixels of movement blur.

If this is really good enough for 'critical work', then presumably 2.4 pixels is not significantly greater than the other factors that lead to loss of sharpness, such as the ones I listed above.

Is this really true?

I recall using exposures of several seconds when attempting to shoot the total lunar eclipse a couple of years back, and sadly, I failed to 'do the math' ahead of time, and the movement blur was well into the range of "totally unacceptable".

This, for instance, had an exposure of 3s, and I'd say it's awful:

So I must confess to being a little sceptical that as long as a second (or half a second at 400mm) would give really good results.
Pentax K-3, DA18-135, DA35 F2.4, DA17-70, DA55-300, FA28-200, A50 F1.7, A100 F4 Macro, A400 F5.6, Sigma 10-20 EXDC, 50-500 F4.5-6.3 APO DG OS Samsung flash SEF-54PZF(x2)


Link Posted 03/11/2009 - 14:47
I've been using Michael Covington's figures for years with no problems. His Astrophotography for the Amateur book is a solid read for budding astro shooters.

BTW. It makes a huge difference where the moon is in relationship to the celestial equator. The closer an object is to the celestial equator, the shorter your exposure has to be. A 28mm lens can be pointed at the pole star, which is 90 degrees from the celestial equator, for as long as 90 seconds with no apparent star trailing.
Last Edited by greyhoundman on 03/11/2009 - 15:01
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