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Astrophotography with fixed camera
Photographing the Total Eclipse of the Moon

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Astrophotography with fixed camera

When writing on this subject, our intention is to encourage astrophotography, un-mythicizing and presenting classic and basic concepts in a simple and direct manner. Our E-mail should be used for deeper discussion of the subjects dealt with here, and also for criticism and information exchange.
Astrophotography renders possible to make a permanent record of the sky phenomena and later comparison, both in terms of productive observational astronomy, by recording variable stars, meteors, eclipses etc. and of the record of beautiful images , which are a source of fascination and may be obtained in a simple way.
To start photographing the sky you will need a camera, a tripod and a shooting cable.
The camera must have the following characteristics:
1- It must be manual, never one of those automatic ones which depend on batteries to work, or do not allow you to control focus, diaphragm and speed.
2- It must have position B (exposure) on their speed scale, that is, you must be able to keep the shutter open for as long as you wish, using the shooting cable for this purpose.
It is desirable, although not absolutely necessary, that the lenses could be changed (the use of large angulars and tele-objectives expand the limits of astrophotography), the mirror lifted and locked and the focal screen changed.
It is unacceptable not to have a precise focalization and strong vibrations when operated.
Armed with our camera, tripod, shooter and a film of average sensitivity ( 400 ISO), let’s go someplace far from the city lights, preferably in a night without, or with very little moonlight, and start working.
We will start with a type of photography called fixed camera, which will grant us gratifying experiments – but first some important data:
1- Earth movement makes the stars move 15º/ h within our field of vision. There is a limit of exposure, beyond which the apparent movement of the stars will make them look like a line forming trails on the negative; a practical rule is to divide 1000 through the focal distance of our objective, thus obtaining exposure time in seconds. Thus, with a 50 mm objective we will find 1000/50= 20 seg. ; for a 135 mm teleobjective, 1000/135= +/- 8 seg. etc. etc.
2- WRITE DOWN ! We easily forget such data as time of exposure, opening etc. . Make a rule of always writing down the photo number, time of exposure, diaphragm, photographed object, date, hour, place where the photo was made and any interference at all.
Our first experiment will be to direct our camera to a known constellation ( Orion, for example) and, maintaining the 50 mm objective fully open, set the shutter in B e make a 20 seconds exposures, using the shooting cable with lock. I am sure you will be surprised by the number of stars that will appear in the field, certainly 1 or 2 magnitudes beyond what you may see with the naked eye. Let us make further exposures of the same constellation for 30, and 40 seconds and 1 minute to compare results.
Now point the camera to another known area and leave it on B, close the diaphragm 2 points and leave a 20 minute exposure. We will see the trails, light lines formed by the movement of the stars. You will be able to have a better view of the colors of the stars, thus recognizing the constellations.
Repeat the same photo, with the camera objective being focalized for 30 meters; you will then notice that the unfocused stars will be larger and will show their colors in a better way. Repeat the process for different distances and compare the results.
Direct your camera to the South Pole, focusing infinite, close the diaphragm 3 to 4 points (if you have a 1.4 objective, go to 4 or 5,6 ), set on B, use the shooter as a lock and leave the film exposed from 30 minutes to 1 hour. We will see the trails left by the stars moving around the South Pole of the sky, the star colors will be very distinct and in dark and open places we will notice the big and the small Magellanic clouds as light flecks amidst the trails.
Much more may be made with a fixed camera, for example, photographing artificial satellites, meteors, comets, eclipses , hidden spots and beautiful compositions, such as the light plumes and cones obtained by the famous astrophotographer David Malin. Artificial back lights (trees, houses or other fixed objects contrasting with the sky) are frequently used to compose beautiful scenes – let your imagination fly !
I hope these hints will make you start working - but you must know that, by starting, you will be running the risk of falling desperately in love with this marvelous art - astrophotography.

José Carlos Diniz
dinizfam@uninet.com.br

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Photographing the Total Eclipse of the Moon
( paper presented at the Museum of Astronomy and Related Sciences)

You can and should photograph the eclipse of the moon. You needn’t by an expert to do it. You will try to present you some simple and basic rules for your success.

Nowadays there are tiny cameras available, equipped with the highest technology. Unfortunately, they hold full power on the manner in which you photograph: they determine the focus, time of exposure and diaphragm opening; therefore they are not suited to quality photographs of this kind of phenomenon.

We will need a manual camera, reflex if possible, with control of the parameters focus, time of exposure and opening (or diaphragm). In case the camera allows the lenses to be changed, excellent; a tele-objective would be rather welcome. Although not essential, a tripod and a shooting cable help the machine to remain stable during exposures at lower speeds.

Those who have a lunette or small telescope will have to provide the coupling between the camera and the instrument, so as to have it set as if the instrument were the camera tele-objective. The adaptation will depend on the type of instrument and must be explained on a case by case basis.

Another important point is the choice of the film. Nowadays there are several quality brands available in the market, and we have no preference. Some technical aspects to be pointed out: 100 and 400 ISO for negative films and 50 to 64 or 100 ISO for positive films (slides). The choice will depend on the camera we have: the more light (larger lens opening), the less sensitive may be the film, and vice-versa.

The Moon is a very large and luminous object; however, sometimes we are frustrated by the photographic results. This is due to the disappointing size of the image we obtain. Let us check the size of the Moon image on a 35 mm film for the different focal distances of lenses:

Focal distance of the objective in mm Size of the Moon image on a 35 mm film
28mm 0,25mm
50mm 0,45mm
100mm 0,91mm
300mm 2,7mm
500mm 4,5mm
1000mm 9,1mm
2000mm 18,2mm


Now that we know which is the appropriate camera, the estimate image size, now that we have a tripod (or a sound support and a shooting cable) and a film of suitable sensitivity for our lens, we may start the procedures to photograph the eclipse.

During the eclipse, the Moon first plunges into the dim cone and then into the cone formed by the shadow of the Earth, going from intense brightness to a faded brightness (penumbra) and then to total darkness (umbra). It is desirable to record each phase; they are long and give us time to prepare the camera and set parameters (focus on the infinite, diaphragm and speed in accordance with the tables below, which may be used as reference). For better results, we should have different exposures, above and below the levels recommended in the tables, and close the diaphragm by one point. We prepared three tables, one for each film sensitivity, allying opening and time of exposure to be used in each phase of the eclipse.

400 ISO Film

  F/16 F/11 F/8 F/5,6 F/4 F/2,8
Full Moon 1/250 s 1/500 s 1/1000 s 1/2000 s 1/4000 s -
Penumbra 1/15 s 1/30 s 1/60 s 1/125 s 1/250 s 1/500 s
Partial 2 s 1 s 1/2 s 1/4 s 1/8 s 1/15 s
Total 8 s 4 s 2 s 1 s 1/2 s 1/4 s

100 ISSO Film

  F/8 F/5,6 F/4 F/2,8 F/2 F/1,4
Full Moon 1/250 s 1/500 s 1/1000 s 1/2000 s 1/4000 s -
Penumbra 1/15 s 1/30 s 1/60 s 1/125 s 1/250 s 1/500 s
Partial 2 s 1 s 1/2 s 1/4 s 1/8 s 1/15 s
Total 8 s 4 s 2 s 1 s 1/2 s 1/4 s

50-64 ISSO Film

  F/5,6 F/4 F/2,8 F/2 F/1,4
Full Moon 1/250 s 1/500 s 1/1000 s 1/2000 s 1/4000 s
Penumbra 1/15 s 1/30 s 1/60 s 1/125 s 1/250 s
Partial 2 s 1 s 1/2 s 1/4 s 1/8 s
Total 8 s 4 s 2 s 1 s 1/2 s


Some suggestions:

A distant place will allow better results, as there will be no interference from the public illumination of the big cities;
Write everything down (hour, camera, diaphragm, time of exposure, weather conditions etc.) to be able to make a better appraisal of the results, and to provide a sounder basis to be applied to other opportunities.
Beautiful results may be obtained by photographing the Moon and composing a first plane with trees, buildings, houses, mountains, etc. Let your imagination fly and build photo-compositions of extreme beauty;
It is possible to have all of the eclipse phases in one sole photo. We only need to know the precise moments of its different stages. By placing the Moon on the bottom right corner of the photographic field, the image of the Moon will move in the photogram as the eclipse progresses.
After we prepare the composition, we position the focus in the infinite and determine the correct diaphragm for the stage we want to record. With the camera set in B and using the shooting cable, we proceed to exposure with a COVERED objective, using a black cardboard cover, which we remove at regular time intervals (5 to 10 minutes), being careful to change the time of exposure in accordance with the brightness conditions of the Moon.
In this case, we suggest the use of a large angular lens (24 to 28 mm) to cover the whole trajectory of the Moon during the eclipse, and a film as slow as possible. The disadvantage is the fact that we will get a very small image of the Moon (see table).

I hope these hints will help you to record this beautiful and rare phenomenon.


References :
1- Covington, Michael – Astrophotography for the amateur , Cambridge University
2- Gordon, Barry, Astrophotography, 2ed., Willmann-Bell, Inc."

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