February 20, 2008 Lunar Eclipse
It has been a long time since I photographed the night skies using a telescope, having done so in the past with the venerable Olympus OM-1. Maybe this has a bit to do with middle age as I seem to prefer winter evenings with my companion in front of a fireplace where it’s warm.
Pleiades Star Cluster – Kodak Gold 1600 film (30 minutes at f/8.0); Olympus OM-1 coupled to Takahashi FC-60, piggybacked on Meade 2080 LX3; © Copyright Reserved, Richard Lovison; 1991-2008
But February’s total lunar eclipse was going to be the last one viewable in my area until 2010, so I thought I’d attempt to photograph it using the Olympus E-1 and the Takahashi FC-60 despite the fact that it was only 10oF that evening.
Olympus E-1 coupled to the Takahashi FC-60; © Copyright Reserved, Richard Lovison; 2008
In hindsight, there are two things I would have done differently and I mention them so those new to astrophotography can learn from my mistakes.
Firstly I decided to mount the Takahashi FC-60, a 500mm refractor telescope, on a camera tripod instead of piggybacking on my Meade 2080 LX3. Mounted on the Meade, I could have used the built-in clock drive to compensate for the earth’s rotation as well as the moon’s motion.
The earth’s motion does not create a problem unless the exposures are longer than .5 second with a 1000mm lens and in this case since I chose not to go higher than ISO 200 to avoid high noise levels, many exposures were longer than this.
Secondly I changed the focus during the total eclipse after initially setting it while the moon was bright. This was a big mistake as the moon was too dark during the latter part of the eclipse to achieve accurate focus while viewing through the E-1’s viewfinder.
I then had to try and focus on a bright star, which was still difficult, before bringing the moon back into the field of view. This error led to many failed images.
Lunar Eclipse 1; © Copyright Reserved, Richard Lovison; 2008
In spite of my errors, I came up with a few images that were usable. The one above was taken at 8:58 pm EST, shortly after the moon entered the Umbra. I took a spot meter reading off the brightest part of the moon, snapped a test image, checked the histogram and made the appropriate corrections. The resulting exposure was 1/100, f/8.0 at ISO 100. This exposure resulted in the brightest part of the moon being properly exposed and the eclipsed section going black.
Lunar Eclipse 2; © Copyright Reserved, Richard Lovison; 2008
This second image was taken at 9:56 pm EST, very near totality. The exposure was at 1 sec, f/8.0 at ISO 200. This photograph was slightly less sharp than the first and about 1/2 stop underexposed. The underexposure resulted in a bit of noise when I tried to recover the shadows (corrected using Noise Ninja) and a bit more sharpening was hence applied to produce a degree of sharpness closer to the first image.
I chose to compromise and expose for the eclipsed part of the moon and thus the red-orange hues were visible though I didn’t push the brightness too far as to severely overexpose the part that remained out of shadow.
Lunar Eclipse 3; © Copyright Reserved, Richard Lovison; 2008
This last image was taken at 10:27 pm EST, at a time nearing mid-eclipse. The exposure was at 3.2 sec, f/8.0 at ISO 200. Due to the long exposure without tracking and most likely inaccurate focusing including possibly atmospheric turbulence, this image was much softer than the first two thus requiring more aggressive post-processing sharpening.
The exposures I used were largely determined by trial and error, chimping – a process of taking an exposure, checking the histogram and making corrections if needed – and from drawing on experiences gained from previous eclipses.
It is always a guessing game because the amount of light refracted by the earth’s atmosphere – the light that illuminates the moon during eclipse – varies from one eclipse to another and is dependent on the amount of water and solid particles in the atmosphere at the time. A useful table of exposure times can be found here.
Another rule of thumb to pay attention to is the maximum exposure time as it relates to lens focal length to minimize image blur owing to the earth’s rotation and the motion of the moon.
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Focal Length of Lens
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Maximum Exposure Time
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1000mm
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0.5 seconds
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500mm
|
1 second
|
|
300mm
|
1.6 seconds
|
|
200mm
|
2.5 seconds
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|
100mm
|
5 seconds
|
|
50mm
|
10 seconds
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24mm
|
20 seconds
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For a 1000mm focal length lens (the Takahashi FC-60 has a 1000mm effective focal length with the E-1), the maximum exposure should be approximately 0.5 second, which would partially explain the slightly soft second and third photos.
To minimize any vibration while taking the images, the camera had an anti-shock setting of 2 seconds and the Olympus remote cable, RM-CB1 was used. Proper balancing of the scope and camera on the mount is crucial as well.
I’m looking forward to experimenting further with the E-1 in astrophotography and I encourage others to try though I think most will encounter many obstacles in an attempt to do deep sky photography. CCD-based digital cameras specifically designed for this type of work are a better alternative as they have built-in cooling systems to reduce the heat generated in their CCD chips and thus keep the noise level down to enable longer exposures of very dim objects.
But you don’t need to photograph the night sky to enjoy it. There are many beautiful sights to behold, such as globular star clusters, nebula or just the sweeping vista of the Milky Way (the view of our own galaxy edge-on as we look toward the center) with a good pair of binoculars and a planisphere.
An excellent alternative to a planisphere is the open source software ‘Stellarium’, a desktop planetarium that is freely available for the Linux, Mac and Windows platforms.
Just try to get out on a clear night, find a dark location if you can and look up. The wonders await you.
Until next time—here’s wishing you dark skies!
