This image is a combination of photo-mechanical and digital compositing.
The sky background was a 35min time exposure accomplished by 'piggy-backing' the camera on an astronomical German Equatorial telescope mount which was precisley polar aligned and employed an electronic drive corrector to fine tune the tracking rate to match the rate of the Earth's rotation under the specific conditions. A 12.5mm illuminated cross-hair eyepiece was used in a 110mm/f 7.3 Newtonian telescope for a magnification of 90X to manually guide the tracking to the ultimate level. A Canon 24mm/f 2.8 SSC lens was used for the background shot.
The foreground image was shot in evening twilight with the camera pointed due *east*... away from the setting sun. From tripod, bracketing widely to achieve a slide with the sky background completly 'washed out'... and the tree line as near-black silhouettes.
This cannot be metered very well, and is basically hit or miss... twilight lighting conditions change rapidly... shoot a little too early, you record the familiar daytime sky-blue... shoot too late and the Earth shadow can induce pinks, reds, blues and violets when facing east at sunset. I checked the meter constantly and bracketed widely... keeping in mind I planned to push-process the film to bring out all the details in the subsequent night time shot.
I rattled off some 24 shots during the white sky 'sweet spot'... and had maybe 3 or 4 suitable for overlays in a composite. To force the perspective and maximize the depth of field effect, I shot my foreground with a 50mm lens... Canon SSC f 1.4 to be specific.
Both background and foreground were from the same roll of Kodak Elite II 100 (ISO) slide film... as mentioned, pushed two stops during development. After development, the tree silhouette image was physically overlayed on top of the starry background picture. A glass slide mount was chosen to contain the composite... this held the films as flat as possible to minimize edge abberations during the duplication process.
A zoom slide duplicator has a very narrow depth of field... even the thickness of a piece of film can effect focus... focusing this type of composite is critical. I used a 300 watt incadesent photo flood to illuminate the very dense composite for this critical focusing... with camera and duplicator mounted on tripod for the entire procedure... about 6" away from the photo flood during focusing.
The slide duplicator I used has a fixed focal ratio... f 16. I used Kodak Royal Gold 25 (ISO) color print film to produce the inter-negatives. This film had the finest grain structure of any color print film ever made, but with such slow film speed and lazy focal ratio I chose to illuminate the slide composite with a flash.
I used an AC powered # 72 DIN slave flash mounted in a flex arm desk lamp to position it in front of the duplicator. Of course, a camera mounted flash was used to trigger the slave unit.
With such a bright light source necessary to expose the duplication film, it was also necessary to employ a translucent diffusion filter with the slide duplicator to insure even illumination across the field. Since the duplicator's focal ratio was fixed, the only way to control exposure 'stops' was to alter the distance of the slave bulb from the diffusion filter. I 'bracketed' my shots by carefully measuring the distance between the two elements and changing this distance by 1/2 inch between exposures.
I bracketed widely, going from 1/2 inch apart out to 6 inches... in 1/2 inch increments. With my set up, exposures between 1/2 to 2 1/2 inches yield satisfactory results... depending on the density of the original composite image.
After the duplication film was developed, the four best resulting inter-negatives were selected, scanned and composited digitally using Picture Window Pro 3.1.h with adjustments in Curves dialog and a slight Un-sharp Mask to max faint details without making brighter objects too harsh.
It should also be noted that both films used in this process are now discontinued... but suitable films are currently available. Also, the contrast boost created by using daylight films for slide duplication is undesirable, in most instances. The boost in contrast is welcome in deep-sky astro however.
With the power of the digital darkroom, this type of photo-mechanical composite is rarely done these days... but my inter-negatives from this work print incredibly well... I've sold several 20" X 30" poster prints of these shots... and if hung in the right room, 30" X40" is realistic! A 30" X 40" print suitable for hanging from 35mm... that's too cool!
Some of the fainter stars and nebula in the image above lie at distances of 15,000 to 25,000 light years... :::ONE::: light year is equal to 5.88 trillion miles... now how's *that* for 'Depth Of Field' ?!?
To see a larger version of this image, and others go to my web-site: http://home.att.net/~astropix/Milky_Way_Setting.html
(Yo 'Z'... no secerets - I shared every little thing... *no one* makes a living doin' astro... it's all about pride and integrity!) GP
(Hee-Hee)... LOL... I didn't want to write it, either! The subject is Alternative Process... and since inquiring minds (may) want to know... I felt I should let the cat out of the bag on this one! HeH... if astro stuff was easy... everyone would do it! Thanks for the ratings!
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