untitled

The Search for Nova by John Fletcher F.R.A.S.

Occasional naked eye Novae can be spotted around magnitude 3 to 5. To find these one must study the skies and memorise the star fields and constellations. Norton's Star Atlas is a very good reference for naked eye stars and naked eye Nova hunting as it shows stars to 6th magnitude which is the upper limit seen without optical aid. It is advisable to check that no bright planets are in the area as even Uranus in a good sky can be glimpsed at magnitude 5.8 when at opposition.

Using binoculars of say 10 x 50 stars to magnitude 8 are easily viewed on clear nights. This means that many thousands more stars can be viewed than with the naked eye. Binoculars around this size give fields of around 6.5° but differ according to their magnifications, (eg 10 X ) and their lens size, (eg 50mm). With my 10 X 50 binoculars I can just fit Dubhe and Merak, (The Pointers) in Ursa Major within the field so therefore the field is about 6° in diameter. When doing a Nova patrol you must be methodical and view fixed areas regularly within your field of view. Do not sweep at random across the skies as you may well do when comet hunting. So many stars will be glimpsed and things will only become confusing for you. By viewing your chosen areas regularly you should be able to memorise them and be able to recognise a new star if it should appear. To help locate the same search areas each time, try and place a known star or recognisable star pattern of asterism within each field. Once learned it becomes a very easy thing to locate the same field in the future. A few minutes per night over several nights is all that is needed to build up a mental picture and so you could then move onto a new field. Perhaps the first year you could concentrate on 2 areas per one hour of right ascension, ie 4 areas a month. With dedication you could know all 48 areas by the end of your first year.

Below is some information based on the observations recorded in the British Astronomical Associations archives to the year 1979.
(Full acknowledgements to the BAA)
Found 5 Novae at max; Magnitude 3 - 4.
Found 12 Novae at max; Magnitude 4 - 5.
so to be expected from statistics based on star numbers in each magnitude range.
Novae at maximum magnitude Expected Found
5 - 6 30 10
6 - 7 80 16
7 - 8 300 30

Possible missed total.
300 Novae; 4 per year at least brighter than 8th magnitude.

The star atlas I recommend for the binocular searcher is the Uranometria 2000 by Tirion, Rappaport, Lovi. The atlas covers all stars to 8th magnitude and covers the 9th magnitude range as well. It is a good idea to circle the stars you see with a soft pencil on the atlas, or if you don't like that idea trace the fields of stars off the atlas. A job for one of those cloudy nights.
It is interesting to note that all the planets except Pluto and some of the minor planets such as Ceres and Pallas can be seen in binoculars. Do be aware of these as many false alarms have been made due to the presence of these Solar System bodies.

Photographic Nova Patrol

Unguided standard 50mm lens.

Using an S.L.R. cameral and a standard 50mm lens at full aperture of say F2 - F2.8 one can open the shutter for between 15 and 25 seconds before the stars start to trail on the negatives. An effect due to the diurnal motion of the Earth. The camera should have a manual B setting and a cable release should be used. Also a very firm tripod should be used so as to avoid displacements of the star images from vibrations, (eg wind). The area of sky recorded on a 35mm film frame is some 27° by 38° which is some 1000 square degrees of sky. Using 400asa film or faster one can record stars to 9 mpg ( photographic magnitude = mpg) on a good night when transparency is at its best and with no Moon in the sky.

Driven 50mm lens and 300mm lens
Firstly I do not advise to drive a 50mm lens for more than one minute. The most productive Novae areas are towards the main plain of the Milky Way. On longer exposures due to poor separation the stars become so crowded that checking for Nova becomes a very hard and sometimes an impossible task. It is better to have a shorter exposure recording stars to say 10th magnitude. Also more areas can be covered in the time you have available.
With my own 300mm F5.6 lens I am able to record stars to 12 mpg in a 4 minute exposure using TriX 400 film. The focal length of this lens is 6 times greater than the standard 50mm lens so the star drift is some 6 times greater in the same given time exposure. To overcome this I piggyback mount the 300mm lens on my driven equatorial mounted reflector. If the equatorial mounting is well aligned with the true Pole and the right ascension drive is running at the correct rate to compensate for the Earth's rotation, one should be able to open the shutter for 20 minutes without making any drive corrections using this lens. However, stick to recording stars to 12 mpg and the 4 minute exposures. The separation of the stars using the 300mm lens will be much greater than the 50mm lens and will give a smaller field of 7° by 4.5° on 35mm format negatives. This is a similar field to the 10 X 50 binoculars so perhaps you may wish to produce your own masters for both visual and photographic checking for Nova.

With a photographic Nova patrol it is most important that all films are developed the same day. To delay your results could mean that you could end up with a pre discovery shot and not be named as the actual discoverer. To develop TriX 400 film all you need is a small developing tank and the chemicals. These can be purchased for around £25 and the chemicals will develop many films. I am sure that every local astronomical society has a member who would be willing to show you how to develop your films. With practice it becomes a very easy job to do. A lot of people are tempted to use 1000asa colour slide film. Remember sending these colour films away for developing may take many days before you are able to check your results on their return. The answer is to do your own E6 processing. Using a small developing tank and chemicals this is relatively easy but is far more expensive than black and white films. Finally a most important thing to do is always take two shots, one straight after the other of each area being covered. Photographic flaws and minute dust specks may appear as a suspect new star or may even hide one.

Finally those of you who have not as yet wanted to discover something, here is your chance. Nobody knows when a very faint star of say 15th magnitude will turn Nova, increase many 1000s of times in brilliancy and show itself within one of your chosen areas.

BE THE FIRST TO SEE IT..........BE THE DISCOVERER.

Good Nova hunting and Clear Skies.

John R Fletcher.
Mount Tuffley Observatory. UK ( C ).