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John Isles, 11105 Tremont Lane,
Plymouth, MI 48170       e-mail: jisles@voyager.net

Program Setup and Observing Methods

Before I go any further, it is necessary to say that there are probably as many different variants of this basic theme as there are observers. This is merely my own set of methods that I have found successful over the past few years; no doubt many of you have your own tried and tested ways of coping with the observations of our erratic friends!

Like many AAVSO members, I tend to specialize; in my case, I observe mainly dwarf novae, obscure Miras and several nebular variables, and am also interested in producing charts for presently unobserved, or underobserved, variables. I use a 14" Newtonian on a Dobsonian mount, which is, in my opinion, far better suited to the observations of these stars than an equatorial would be. I have an intimate knowledge of the constellations and consequently waste little time on using finder charts, though for some stars (GQ Cyg for instance) one is necessary. I also observe the less-obscure Miras when near minimum, since this is when they are least followed by most observers. On a good, moonless night, sixteenth-magnitude stars are not difficult to see, though of course reliable estimates are less likely to be made. I hope one day to catch a star of the seventeenth magnitude - but this is just a personal target I have, and I will not lose any sleep if I can’t honestly measure up!

The Program
The size of my observing program is very extensive; currently there are 512 objects in the “pruned down” version, though of course this is over the whole northern sky. The observing list for January features 200 different stars, many of which are Miras and so need observing only once a month. The rest are stars that need to be observed on every clear night, such as CV’s, RR and CQ Tau, and so on, or those that demand frequent observation, like symbiotic stars, RCB types, etc.

The program itself is in database form using Microsoft Works. Nothing grander is necessary, and it is quite adequate for planning the monthly lists of stars to observe. A small screen-snippet from the database appears below.

The stars are arranged in standard order following the Harvard Designation and entered into the monthly notebook in the same order. The column after the name of the star contains notes about the star; thus “MDU” against 005427 W Psc shows that “More Data Urgently” applies to this star. The next two columns give months of Maximum and Minimum, respectively, for the star; the final column gives indications of frequency of observation. The default (no entry at all) is one observation per month. Many of the stars above are dwarf novae and carry asterisks in this column, which indicates nightly observation.

At the Telescope
It might be thought that printing out the information would be the most straightforward way of transferring the soft copy into hard results, but I have found that printer ink and the damp British climate make bad bedfellows, and so use instead a standard notebook for use at the eyepiece. This carries all the essential information that the database supplies, since a fresh list is made at the start of each month. The screen capture below shows a section of the January observing program:

If a star is at maximum or minimum that month, this is shown by an M or m as appropriate, and a circled asterisk indicates a star that needs urgent observation, such as S or RX Psc above. Needless to say, the AAVSO predictions are used extensively in setting up both the general and monthly observing programs. An underlined star indicates nightly observing is necessary (e.g. RX And or TY Psc above). Whilst on the subject of individual stars, some objects above may be unfamiliar to some observers; TY Persei is an interesting Mira star that I have produced a chart for, though it is not under regular AAVSO scrutiny. It is in the same field as V666 Cas (the artist formerly known as DHK-1), and closely south is another unobserved star, CF Per, a probable nebular object that I have already determined does not conform to the published GCVS data on it. V369 Per is a bright (tenth-magnitude) star, again, a probable nebular variable. These stars fascinate me, even though they are not always as spectacular as the U Gem objects.

At the eyepiece, the individual charts are kept in three large hinged folders, but this time arranged alphabetically by constellation for ease of finding; one folder carries constellations A to D, the other holds the rest, though within each constellation, stars are arranged (usually) in “Harvard Order”. The third folder holds all the charts for stars currently below the horizon. At the start of each month, when the program for that month is drawn up, the appropriate charts are consigned to, or taken from, this third folder. Like most observers, I begin in the west with the brighter stars, thus ensuring optimum dark-adaptation for the later faint objects, and move gradually eastward as the night wears on. It happens that my worst aspect is the western one in any case; I am about 8-9 km east of Norwich, even by our modest British standards a small city, but causing some light pollution just the same, though there are no street lights in my village.

Another of my interests is in the production of new charts, and these highly-provisional charts are filed with the ordinary AAVSO ones. I have written a BASIC program that produces photographic-quality output charts from accurate input data, obtained usually from the GSC or USNO Catalogs. The chart can then either be printed out or, better still, a chart of the area downloaded from the Digital Sky Survey and the chosen comparison stars simply added on-screen and then printed out to be commensurate with a standard AAVSO chart scale. The program gives offsets in mm for each comparison star at any chosen scale and corrected for declination. The final task is the sky-check, absolutely necessary if the chart is to be used for visual observation. The positions of hundreds of the more obscure variables in the GCVS are inaccurate to various degrees, and these positions are of course used by other referencing catalogues. My program has enabled me to correct some of these erroneous positions, as well as observe the now correctly-identified variables, a case in point being the Mira star BR Ori.

I hope this article has provided some sort of insight into the way an ordinary AAVSO observer works, and I invite any other observer to contact me via email at: m.poxon@virgin.net

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