In the spring of 1997 I aquired a used, Vietnam era, aerial camera lens from Peter Ceravolo, well known as a builder of high quaility telescopes. The lens itself is a 300mm F4 Hycon. Peter had the year before built a large astrograph for use with medium format film, and this instrument was used to produce his famous comet video. On 4x5 film, 300mm is equivalent to a 100mm lens for 35mm cameras - or in other terms, two power. So what you have is a very wide angle, fast instrument that behaves more like a schmidt camera than photography through a telescope.

Seeing advantages of a larger film format (medium format is approx 4 times the size of a 35mm negative), Peter set out to experiment with large format film, specifically 4x5 inch sheet film (10.2 x 12.7 cm). The first experiment was with the Hycon lens. The rear element was in rough shape, so Peter disassembled the lens, repolished the rear element, and built from scratch a focusing ring, 7" tube and a custom made vacunm film back. The film tends to shift over long exposures, so the vacumn is needed to hold it in place.

However a major probelm was soon discovered. While the lens displayed overall excellent optical qualities, in Peter's words, "it can't focus blue to save your life". Much of Peter's experimental work centres around optics that he can use to produce exceptionaly high quaility images, to later be used in vidoe and computer CD productions, thus a lens unable to image colour was of little use to his business. Had Peter been aware of the history of areial photography, he would of realized the lens would have been uselss fromt he start. (But then, I would have been out foa good opportunity).

Taking pictures from the air is almost as old as photography itself. A principle well know to users of large format camera called the "Scheimpflug Rule" is named after a Prussian army officer who first set out to tackle the problems with focusing a view camera from observation ballons over some 100 years ago.

The history of the Hycon lens I am using traces it roots to World War 2. During the war many new developments in photography were made, along with many failures. The first use of lens coatings, rare earth glasses, and the development of infra-red film all came into thier forte during this period. Not all the advancements were good. Some lenses used radioactive glass, or materials in the glass that had poor longevitity. The purpose was to build a lens that got the job doen now, and if the glass deteriorated within 5 years, it did not matter.

Part of the problem is the even during clear weather, the blue light int he atmosphere scatters about widly, "clouding" out picutres of the ground. To overcome this, usually a yellow or red filter was used to cut out the haze. As a result, areial camera lenses were designed from the start to be used with a filter in place, and therefore to focus the red end of the spcrum the best. In some cases, these lenses were even made to provide a sharp focus into the infra-red. You can still today buy surplus military infra-red filters and in some cases infra-red only lenses.

Older astronmy books from the 1950's refer to the use of these lenses for astro-photgraphy, but right up into the 1970's, black and white photgraphy was the norm over colour photography. Another problem was older B&W films, especially the higher speed ones such as Kodak's Royal pan (rated at 1000 ASA) were increadibly grainy films by today's standards, and as such covered up a multitude of sins. Newer, sharp films such as Tech Pan, T-Max and Delta are extremely fine grained and very unforgiving of any lens abberations. You might also read on occasion a good review of these lenses from some large format photographers. As both an astro-photographer and a large format shooter, I can tell you there is a world of difference between the two. Most daylight or land based LF photography is shot with the lens stopped down to F16, F22 or greater, were just about any lens can look good. Astro-photography is often doen with the lens wide open.

About the time of the Vietnam War, the optical quality of Areial camera lenses skyrocketed compared to WW2 and Korean War vintage. There were several factors for this, including the use of computers in optical design, the use of new rare earth lenses, improved maching techniques, and so on. However these lenses were still balanced for use with ayellow or red filter to cut through the haze. In fact, for infra-red aerial photography, B&W is to this very day still superior to colour infra-red photography form some commercial and law enforcelment applications. Under IR light, green plants turn white in B&W film. AS an example, a sod farmer looking for signs of a grub infestation can easily sopt the affected areas in B&W IR film but the darker areas. You can go to my B&W photo gallery for some land based examples of B&W IR photos.

The problem then is not hte film used, or even the type of CCD ships used in some military applications, but the fact that you need to cut out the blue light to get through the haze of the atmosphere. Thus, possibly to this day, aerial camera lenses will be balanced for use outside of the blue spectrum.

Upon hearing of Peter's problems witht he lens, and his moving onto different custom made lenses for hsi 4x5 projects, I was able to contact him and aquire the lens. My forte is B&W photography, and Peter agreed that it should serve fine as a lens for hypered tech pan film, readily available in 4x5 size. From Peter's point of view, commercially colour photographs of anything outsell black & white on a 1000:1 ratio, but from a hobbist point of view with a small darkroom, tech pan is the way to go, so it was a win-win situation for both of us.

A custom made film back had to be designed, so I apporached my long time friend Dave Rubenhagen, a local pattern maker who spends spare time with his milling machine in his shed. His other hobbies iclude playing ont he computer, and he is an expert at both Deathmatch Duke Nukem 3D and Autocad 13 (yeah, I know - a weird combination). Genius he is though. Dave possess the ability to hear a description of what you need, image that item almost instantly in his head, bang it out on Autocad, and then produce the item on his mill. Based on my dscriptions and a spare 4x5 sheet film holder that he disassembled, Dave created a beautiful, all aluminum vacmun film back sheet film holder. In the darkroom, it loads just like a standard Lisco or Fidelity film holder. The vacumn is created using a Gerber Breast pump. This may sound weird, but we testd several vacmun pumps. Aquarium pumps are not designed to be used backwards, and have a tendency to fail after some time. Gast pumps on electric motoers pull to hard a vacumn, and you can see the film virtually ripple ablove where the holes for the vacumn are.

It was actually Peter who came upon the idea of the breast pump. It provides a steady, soft and consitant vacumn - absolutely perfect. And if you are like Peter or myself, with young children still in the nursing stage or just past it, the breast pump serves duble duty. :)

To focus, a ground glass screen is placed on the back of the astrograph, just like a "normal" 4x5 camera, then removed and replaced with the film holder. A sharp focus can be made by focusing on a bright object such as the moon or Jupiter, then locking the focusing ring in place. Perhaps the most critical aspect of the entire astrograph is the placement of the focusing plane of the ground glass, which has to be at exactly the same plane as the film in the holder. To achive this a sheet of flim is placed in the film holder, a micrometer is used to measure the dpth to the film plane, and then Dave built and assembled the ground glass holder at exactly the same depth. To make the ground glass, I purchased from a local glass store two pieces of 4x5 " glass, then with some #500 grit used in mirror grinding, simply used a good ole "W" stroke and ground away. Took little more then 10 minutes to get the glass to the right surface.

August 6th, 1997, at StarFest, Canada's largest amature astronomy convention of approx a 1000 people held every year north of Mt. Forest, Ontario. Since tech pan costs me almost $3.00 CDN per sheet ($1.00 CDN = 0.60 US), I used T-Max 400, with cost me a more reasonable $1.00 per sheet. I shot two pictures at 15 and 20 min guided exposure.

The astrograph is mounted on top of my 5" F12 refractor, mounted on my Losmandy CP-100 mount, with a Byers 7.5" gear drive. Murphy however was alive and well

First lession I learned - make sure you do not develop film in a developing tank with a light leak! Second lession - always have a backup motor in case of failure. This motor has not failed since October of 1986, but it failed that night and the three nights following it. :(

One of the great problems of large format astro-photography is field rotation shows up a lot quicker than on smaller formats. Why I do not know, but I ahve seen it with my own eyes. You have to be just exactly right on. In fact, from my experience I would suggest that a permenant pier anchored in concrete is the way to go. Even with a heavy steel tripod, the ground settlesand you have to re-polar-align each night. Doing this with a motor drive that work only intermittantly is a real bear of a job. That, and having a power supply burn out on yu is not fun either (but I did have a backup of one of those).

Good news - well, I found out that with the F4 lens and 400 ISO film, skyfog is reached at 20 to 25 min exposure here in southern Ontario. I was also amazed that some of the nebulosity of the Scutum star cloud actually showed up on the negative.

I will end here now...a lot of construction and refinements still going on. With a new baby expected in October of 97, I will not have tiem to build my small observatory untill the spring of 98. I hope to make a few more runs witht he astrograph, time permitting, before then, and I will post results here. I think it will take me a good year to irion out 99% of the bugs, but it is somethign I look forward to.

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