nikonians

Even though we ARE Nikon lovers,we are NOT affiliated with Nikon Corp. in any way.


Sign up Login
Home Forums Articles Galleries News Workshops Shop Recommended
members
All members Wiki Contests Vouchers Apps Newsletter THE NIKONIAN™ Magazines Podcasts Fundraising

Shooting the upcoming lunar eclipse Dec 20-21, 2010

nrothschild

US
10916 posts

Click to send email to this author Click to send private message to this author
nrothschild Neil is an expert in several areas, including camera support Registered since 25th Jul 2004
Thu 25-Nov-10 08:48 PM | edited Fri 26-Nov-10 10:18 AM by nrothschild

We will have a lunar eclipse on the evening of December 20-21, 2010. Members in North America and the western side of South America will have the opportunity to photograph this total lunar eclipse in it's entirely.

The eclipse is visible at the same moment in time world-wide over the area of visibility. The only difference is your time zone and the altitude of the moon. In the Eastern time zone the moon will enter the umbral shadow (first contact-U1) at 1:33am on Dec 21, reach totality at 2:41am (2nd contact-U2), leave totality at 3:53am (3rd contact-U3) and will fully exit the umbral shadow at 5:01am (4th contact-U4). Subtract one hour from these times if you are in the central time zone, 2 hours in the mountain time zone and 3 hours in the Pacific time zone. Those on the west coast will experience this eclipse at a much more civilized time, and the moon will be generally higher in the sky during the entire eclipse. Indeed, the West Coast is within an hour of perfect timing for a lunar eclipse- it doesn't get any better than that! On the east coast the moon will be fairly low at the end of the eclipse, around 38 degrees altitude at mid-latitudes.

The best information for all eclipses will be found on Fred Espanak's eclipse site. Fred prepares Nasa's eclipse publications and chases all the eclipses world-wide. What a great job . I had the pleasure of joining Fred on a tour to view the February 26,1998 solar eclipse in Aruba. He provides some photographic advice on his page, including wide angle landscape type views that I won't address here.

I've shot the 3 lunar eclipses visible to me since mid-2004 on DSLR cameras so I thought I would offer some additional advice based on my experience.

Most people are most interested in the total eclipse phase, which lasts 72 minutes for this eclipse. That is plenty of time to figure out an exposure, and if you shoot this eclipse at home, enough time to run indoors a few times to view images on your computer, or you can bring a laptop into the field.

The most dificult obstacle to overcome is the movement of the moon. You can read my blog entry here for a comprehensive discussion about the rates of movement of the moon in the context of pixels of blur when shot from a fixed tripod. The short story is that with a 12mpx DX sensor (D300, D90, etc) the moon moves at a rate of about 1.3 pixels per second per hundred millimeters focal length. If you shoot this at 1000mm the moon will move 13 pixels per second of exposure time. At 500mm it moves about 6.5 pixels per second. For a D200 the moon moves about 1.2 pixels/100mm FL/second. For a D3X, figure the same as a D300 sensor - the sensor density is very close.

These rates are for zero degrees declination, or the mid-point of the moon's monthly travel across the celestial sphere. This being a winter solstice eclipse, the full moon, and therefore the eclipsed moon, is near the highest elevation in the sky possible for Northern hemisphere observers. That's the good news. The bad news is that even at this extreme from the ecliptic (about 23 degrees) the rate of motion only slows about 12 8%, insignificant for our purposes.

The celestial rate of motion for a 12mpx FX sensor is about 0.87 pixels per second per hundred millimeters focal length. The trade-off here is fewer pixels across the moon and for a given lunar image size in pixels, the results are the same. The FX benefits from a stop or more of improved high ISO performance but that is at least somewhat negated if a 1.4x TC is added to the optical configuration to bring the image scale back in line with the results from a DX sensor with the same pixel count. I still think the 12 mpx FX sensors have an overall advantage, given the obstacles, as I discuss below.

For most lunar photography this lunar movement is not a problem and my blog discusses how I shoot normal moons, even dimmer crescents, at 1000mm with 1/30s exposures with excellent results- from a very stable tripod and using good technique. This will also be generally true of exposures of the partial eclipse phases, where the illuminated portion of the moon will be very close to an equivalent normal partial phase of the moon. In theory, the moon enters the penumbral shadow about an hour before first contact with the umbral shadow. The penumbral shadow is a very low density shadow surrounding the main umbral shadow. In practice, my full moon shots within the umbral shadow are about the same exposure as I experience with other full moons, or somewhere between a "sunny 16" exposure and a "luney 11".

The total eclipse is different because it is very dim. The brightness of the eclipse varies based on exactly where the moon traverses the Earth's shadow and the amount of dust and debris in the atmosphere. Eclipses are particularly sensitive to volcanic dust. This eclipse is predicted to be fairly dim.

The following image of the February 20, 2008 eclipse was shot from a motorized astronomical mount that tracks the movement of the stars. I shot it with a D200 and 500 f/4 Ai-P lens, without a converter. The exposure is ISO 100 F/4 4s.

Click on image to view larger version


On a fixed tripod at 500mm that 4s exposure would have resulted in about 24 pixels of blur!

The Dec 2010 eclipse should be somewhat dimmer than the last eclipse in Feb 2008 so the exposure above would likely be on the high side of what we will experience this time around.

Having the luxury of a motorized mount, in principle I could have shot any reasonable shutter speed, even 30s or more. However, I did not want to press my luck and did not feel the need to stop down- the 500P is a very sharp lens wide open. We had a bout 3" of snow earlier that day, the result of a "clipper" system that moved out very quickly. It was snowing only an hour or so before the start of the eclipse! The attendant winds were a concern, as well as the fact that I had no high power guide scope attached in which I could verify the mount was tracking properly, nor was I able to properly align the mount due to the press of time. It was also uncomfortably cold . You can see some pictures of my backyard eclipse observatory here.

I chose ISO 100 because that was the base ISO of that camera (D200). Having shot several prior eclipses with DSLRs, my experience is that the eclipsed moon is quite delicate and subject to noise. I was not totally happy with prior eclipse images shot at ISO 800 or so. This is compounded by the fact that the focal lengths are often in the range where the final image is near 100% pixels just for a decent web sized image. That is a recipe for noise. On a fixed tripod I would have been forced to shoot ISO 800 to keep the shutter speed down to about 1/2s and the blur down to about 3 pixels.

The following image is a composite of the above total eclipse image and the major partial phases. I was fortunate to have been able to get a fairly complete set of images illustrating the partial phases as well as the total phase.

Click on image to view larger version


The partial eclipse images, exposed for the illuminated portion of the moon, were generally around 1/320s f/5.6 ISO 100. In reviewing my NEFs I see that I should have exposed the thin crescents more richly, by a stop or so.

For all lunar exposures, I use the histogram, exposing to the right such that the brightest portions of the moon fall at or slightly beyond the right side of the 3rd quadrant, resulting in a luminosity of 200 or more, but never allowing the highlights to burn (no blinkies).

The image below, shot at 1/1.3s f/4 ISO 100, exposed for the eclipsed portion of the moon and as you can see the exposure is only a stop or two less than the total eclipse exposure. I underexposed this image about one stop, probably due to concerns about the haze and optical aberrations caused by the overexposed sunlit portion. The image here was raised by 1 stop when rendering the NEF in CaptureNX 2.2. The sunlit portion of the moon is drastically overexposed by at least 10 stops and is quite a test of your optics . Any haze or thin high clouds will create unsolvable problems here.

Click on image to view larger version


The image above is un-cropped. You will note some haze from the less than perfectly clear air. It's unclear to me that the air could have been much better - there is almost always some thin haze in the air, even under optimal conditions. The higher the moon in the sky the less haze. You will also note a crescent shaped ghost from the illuminated portion, inverted. This is an artifact of that 500/4 Aip-P lens and I've seen this same artifact when shooting Earthshine as I discuss below. I have since upgraded to a 500/4 AFS (V1). That lens has the same aberration but appears to be significantly attenuated.

This particular ghost appears opposite the subject, relative to the precise optical center of the image, and equidistant from the frame center. The image above was shot just slightly offset to the upper left, resulting in the aberration colliding with the main image. I will address this issue in further detail below.

For all lunar imaging, I use Auto or Sunlight white balance, shoot raw and correct as necessary when rendering the NEFs. The sunlight preset is probably the most accurate.

The next composite image of two different shots below were shot from a fixed tripod during the March 3, 2007 total lunar eclipse, one at 300mm with the 300 f/2.8 AFSII, the other at 500mm with the 500/4 Ai-P. Exposures as indicated on the image. The bright dot at about 4 o'clock on the 300mm lunar limb is the star 59 Leonis, within a half second before it disappeared during a near grazing occultation. The bright dot at about 3 o'clock on the 500mm image is, unfortunately, a hot pixel that appeared in between the two images, and then disappeared after a number of subsequent frames. Both images were downsized to 65% of original pixels and then composited in one image file.

I include these two images to illustrate what is doable from a fixed tripod and D200, with a fast lens. Any image can be improved but I think I was at least near the limits of what that camera could do with those lenses.

Click on image to view larger version


When I switched to the 500mm lens I decreased the shutter speed to 1/2 second from 1 second, allowing for the larger apparent drift of the moon. My aperture also decreased from f/2.8 to f/4. I increased ISO from 400 to 800 to partially compensate. Interestingly, the exposures are closer than I would have thought given they are a full stop apart in EV. I did shoot a few frames at 1s but decided the blur was more than I wanted. If I were shooting this now on a D300 I would boost the ISO to 1600 to get a richer exposure. That might actually reduce the apparent noise . With a D700 I might try ISO 3200 and maybe 1/4s, but that would have to be determined while shooting and reviewing the images and histograms on the LCD.



Exposure Suggestions

If you have the luxury of a motorized astronomical mount, I would shoot at the base ISO of your camera. I would try shooting wide open and then down one stop, adjusting shutter speed for the desired richness of exposure over the eclipsed portion of the moon.

If, like most people, you are shooting from a fixed tripod then you have some difficult decisions to make in order to optimize the image. As mentioned above, the motion of the moon across the sky is your enemy. You will get some blur or you will get a lot of noise- pick the lesser evil. Here are some specific suggestions:

1. Determine how many pixels of blur you can deal with. My advice would be a shutter speed that results in 2-4 pixels of blur, depending on your expectations. You will want to bracket that shutter speed to see what delivers the best overall results.

2. DO NOT use a TC. A TC will cost you at least 1 stop, and maybe two depending on your lens. I think you are better off with a smaller image, with less noise and/or less blur.

3. If at all possible, shoot wide open. Any increase in sharpness by stopping down 1 stop will almost certainly be negated by a doubling of the blur resulting from cutting the shutter speed in half, given the same ISO.

4. If you have a choice of lenses, consider a shorter focal length but faster lens over a longer, slower lens. In my case I have a 300/2.8 and a 500/4. The 300/2.8 has a lot going for it. Or try both. You have 72 minutes to get your totality "money shot". Experiment with all the exposure settings as well as the optics. If you insist on using a TC, try some shots with and without.

5. Dress warm .

6. Bracket the total EV level of the exposure (altering shutter speed while leaving ISO and aperture fixed). A darker image may be a bit sharper.

7. Similar to the issue of the TC, if you have a choice of 12 mpx FX and DX, either try both or consider the FX. Again, the image will be smaller, but cleaner.

8. Use Mirror Up if you have it, or exposure delay if you do not have a Mirror Up option on your camera. Allow a 5s delay or longer, depending on your support.

9. If you have it, use LiveView to focus. You will not be able to focus on the fully eclipsed moon. You will be able to focus on the partial phases so the best strategy is to focus, switch into manual focus mode, and don't change it. If you lose focus you may be able to focus on a bright star or planet. Both Gemini above the moon and the belt and shoulder stars of Orion below the moon should be suitable focusing stars. My cameras and lenses will autofocus on those stars. After focusing with LiveView, change to Mirror Up. Liveview initiates not one but two mirror slaps with each exposure.

10. Use a remote release, of course. Short of that, use the self timer combined with exposure delay mode if possible.

11. Always fully retract the center column. If your tripod is not the sturdiest, hang weight from the mount and extend the legs as little as possible. My motorized mount has very short legs so I got very intimate with the cold Earth, as my web site images suggest . I used a patio lounge cushion to make the best of that problem.

12. Consider creative landscape images. For North America the moon will be very high in the sky, requiring very short focal lengths to get the moon and a landscape in the frame unless your landscape extends high in the sky (close buildings, mountains, etc.). But there is no law that says you cannot create a surreal image. I saw a very dramatic landscape image of the March 2008 eclipse, where the eclipsed moon was cut and pasted into a gorgeous scene of urban Chicago. Reality? No. Beautiful image? Yes!

How To Practice a Total Lunar Eclipse

Visible total lunar eclipses are as infrequent as every 2 or 3 years, and only last an hour or so. How do you practice for this very unusual subject and exposure? In an interesting coincidence (and it is sheer coincidence) the exposure of "Earthshine" of a crescent moon, up to about 4 days old for a new moon, and the last 4 days of the old moon, is very close if not identical to the eclipsed moon. Earthshine of a crescent moon is sunlight reflected off the surface of the Earth, to the moon and back, dimly illuminating the unlit portion. There is no significant sunlight hitting the moon during a total lunar eclipse, so no Earthshine . The faint illumination of the moon is due to a small portion of sunlight refracting around the edges of the Earth's atmosphere.

I have never bothered to try to shoot Earthshine for moons outside that 4 day range but it may be possible for a day or two beyond that. If weather or schedule does not work out, try it.

I don't often get a chance to shoot Earthshine because my home is ringed with trees and in general the topography my area has rather poor accessible views of the horizon. Early and late moons are always rather low in the sky except during very favorable seasons of the year (Spring for the new moon and Fall for the old moon). I have never had the chance to shoot it with my motorized astro mount, which is not very portable in practice and uncomfortable to use without a very sturdy table.

The following image illustrates Earthshine of a 2 day 21 hour old moon, which I consider about optimum for Earthshine. A day old moon has very weak Earthshine while a 4 day old moon has a very strong sunlit portion with decreasing relative brightness of the Earthshine . I would try to shoot the 2-4 day old moon (an evening event, just after sundown), or the moon 2-4 days from new on the old side (always an early morning event just before sunrise)

The exposure of this image, shot from a fixed tripod with a D300 and 500/4 AF-S working 500mm, was F/4 1/2s ISO 800. That is the identical EV level as the total eclipse shot above, at f/4 4s ISO 100 . And both un-illuminated portions of the moon have very similar, very delicate muted lighting although the color is very different. Earthshine is very blue while total eclipses are usually red or reddish.

This image is also un-cropped, and does not show the same aberration as the total eclipse image. This is partially due to the better optics, in this regard, of the AFS version, but also because the moon is almost perfectly centered. That aberration was probably overlaid directly on the image.

Click on image to view larger version


The image below was shot with the D700 and 500/4 AFS, but with an exposure of F/4 1/2s ISO 1600. This moon was 3 days 13 hours old and was shot during a close approach of the Pleiades cluster, an annual favorite of mine. It is a better image due to the increased richness of exposure, but with about the same or less noise level, commensurate with the D700's better ISO performance and slightly less movement as measured in pixels of blur.

You will note a very faint ghost, but well separated from the moon. The moral of this story is that if your lens has this sort of aberration, you want to either perfectly center the moon (difficult and tedious from a fixed tripod) or make sure it is well off center because the aberration appears the same distance from the center of the frame as the moon itself, but on the opposite side. If you center the image and have a bad enough ghost then it could effect the main image.

Click on image to view larger version


For the coming month, the new moon will occur on December 5, 12:35pm EST. The pre-dawn morning of December 1st and 2nd will probably have the best Earthshine. On the other side of the new moon, the evening of December 8th and 9th will likely have the best Earthine of the new moon. In all cases this is not a favorable time of the year to shoot these crescents (actually about the worst). As mentioned previously, Spring is the best time to shoot crescent new moons and early fall the best time to shoot old crescent moons. December 3rd and 7th will likely have the moon too low on the horizon this time of year. December 1st and 9th are at or near 4 days from new but I have shot good Earthshine at those ages (see above) and may be the best dates. You will need a very clear view of the horizon and a fully cloudless sky. The moon will be 10-20 degrees above the horizon at mid-latitudes at the optimum time to shoot Earthshine on the 2nd and 8th, a bit higher on the 1st and 9th.

Attachment #1, (jpg file)
Attachment #2, (jpg file)
Attachment #3, (jpg file)
Attachment #4, (jpg file)
Attachment #5, (jpg file)
Attachment #6, (jpg file)

_________________________________
Neil


my Nikonians gallery.

Subject
ID
Reply message RE: Shooting the upcoming lunar eclipse Dec 20-21, 2010
1
Reply message RE: Shooting the upcoming lunar eclipse Dec 20-21, 2010
2
Reply message RE: Shooting the upcoming lunar eclipse Dec 20-21, 2010
3
Reply message RE: Shooting the upcoming lunar eclipse Dec 20-21, 2010
4
Reply message RE: Shooting the upcoming lunar eclipse Dec 20-21, 2010
5
     Reply message RE: Shooting the upcoming lunar eclipse Dec 20-21, 2010
6
          Reply message RE: Shooting the upcoming lunar eclipse Dec 20-21, 2010
7
               Reply message RE: Shooting the upcoming lunar eclipse Dec 20-21, 2010
8
Reply message RE: Shooting the upcoming lunar eclipse Dec 20-21, 2010
9
Reply message RE: Shooting the upcoming lunar eclipse Dec 20-21, 2010
10
     Reply message RE: Shooting the upcoming lunar eclipse Dec 20-21, 2010
11
          Reply message RE: Shooting the upcoming lunar eclipse Dec 20-21, 2010
12
Reply message RE: Shooting the upcoming lunar eclipse Dec 20-21, 2010
13
Reply message RE: Shooting the upcoming lunar eclipse Dec 20-21, 2010
14
Reply message RE: Shooting the upcoming lunar eclipse Dec 20-21, 2010
15
Reply message RE: Shooting the upcoming lunar eclipse Dec 20-21, 2010
16
     Reply message RE: Shooting the upcoming lunar eclipse Dec 20-21, 2010
17
Reply message RE: Shooting the upcoming lunar eclipse Dec 20-21, 2010
18
Reply message RE: Shooting the upcoming lunar eclipse Dec 20-21, 2010
21
Reply message RE: Shooting the upcoming lunar eclipse Dec 20-21, 2010
22
Reply message RE: Shooting the upcoming lunar eclipse Dec 20-21, 2010
23
Reply message RE: Shooting the upcoming lunar eclipse Dec 20-21, 2010
24
Reply message RE: Shooting the upcoming lunar eclipse Dec 20-21, 2010
27
     Reply message RE: Shooting the upcoming lunar eclipse Dec 20-21, 2010
29
Reply message RE: Shooting the upcoming lunar eclipse Dec 20-21, 2010
19
Reply message RE: Shooting the upcoming lunar eclipse Dec 20-21, 2010
20
Reply message RE: Shooting the upcoming lunar eclipse Dec 20-21, 2010
25
Reply message RE: Shooting the upcoming lunar eclipse Dec 20-21, 2010
26
     Reply message RE: Shooting the upcoming lunar eclipse Dec 20-21, 2010
28
     Reply message RE: Shooting the upcoming lunar eclipse Dec 20-21, 2010
30
Reply message RE: Shooting the upcoming lunar eclipse Dec 20-21, 2010
31
Reply message RE: Shooting the upcoming lunar eclipse Dec 20-21, 2010
32

G