How It's Done


Important Disclaimer: This is how "I" do my variable star observations. For any newer observers reading this, please keep in mind this is not THE way to do it. Though I'm highly productive, different observers using very different strategies are just as prolific! The golden rule to follow is use what works for YOU. Even if your methodology differs, there may be a tip or two that you can learn. A favorite inquiry for my fellow VSOers is what instrumentation and techniques they employ. I know a good idea when I steal it, and I still like to think I have a lot more to learn.



My Finding System


Click on the images for a larger view.


SS Cyg Finder 1 The finding system I utilize has been refined over the years, mainly as new atlases became available. With computer programs and the SAO and Guide Star Catalog (GSC) now common, I (and many other VSOers) create charts electronically. The GSC has many errors (the worst being missing stars) but I think it works well enough for FINDING. I live and die by an 8X50mm finder scope and this system was designed for it. However, Lance Shaw who used to strictly use a Telrad utilized my charts with great success. I produce these finder charts for nearly EVERY variable I have estimate charts for. The only exception is if two variables are extremely close. That is, they appear on the same 'D' scale chart. I create three different charts for each target field. There are two charts on the front side and only one on the back side.

The first chart (at the top) is what I call the naked-eye view. It is a very broad view of the sky showing the variable position. The field is so wide, in fact, that I haven't had to draw constellation lines on any of the charts! This is used for very rough pointing. I do this by simply sighting along the straight tube of my finder scope. (It goes without saying that a Telrad-type pointing device does this very well.)

The bottom chart is the finder view. The scale and limiting magnitude (7.8) has been set to mimic the Sky Atlas (SA) 2000.0. Years ago, I used photocopied sections of the Skalnate Pleso Atlas (the SA 2000.0 has replaced it) and pasted them directly to the charts. I find these atlases correspond very well to the view through an 8X50 finder scope. The goal here may seem simply to point the cross-hairs of the finder at the variable position, but more often I aim for a star (or group of close stars) which will allow me to star hop to the variable. I get away without a Telrad because I'm looking through the finder with my left eye while simultaneously looking at the sky with my right. The Telrad target used for the naked-eye and finder views are to scale. (I do in fact own a Telrad but it's never used.) I have a general complaint about the lack of straight-thru, right-side up finder scopes. Over the years I've simply become adept at doing the mental gymnastics of upside-down viewing, but right-side up would sure be nice. A few VSOers actually use monoculars to achieve this, but at the loss of cross-hairs.



SS Cyg Finder 2 The back side contains what is essentially a 'B' scale chart without magnitudes, designed to emulate the old 'B' charts that were drawn from the 1855 Bonner Atlas. (Limiting magnitude 10.0) I create one of these charts even when a 'B' chart is available. 1) It's effortless to do with the software, and 2) I find it's better for finding because often the listing of star magnitudes tend to clutter the chart. The only purpose of this chart is for finding! (Incidentally, if a 'B' chart is available, this is a convenient way to correct the obnoxious omissions in the GSC. I also have a copy of the original Bonner atlas which I will use if my "sky check" of the chart indicates major problems -- like a hard-to-find field!) The Telrad target used is obviously not to scale. It is merely there to indicate the position of the variable, which may or may not be visible. The real purpose of this chart is to show the brighter stars near the variable because I rarely go for the variable. It is much better to hit a nearby "asterism" and then star hop to the variable position. This is one of the tricks that allow for consistent finding. Choosing a bright enough "asterism" means you'll also have better luck when the moon is interfering, especially near the full moon. Observe during the full moon? Since DN are not reddish, moonlight doesn't present the problem that it does for the Miras. More importantly: these stars wait for no one!



The Nightly Run


Not walk, run! I currently have close to 150 variables (and growing) on my program which means on any given night 120 of them are theoretically observable. This means starting in the low western sky and then working to the east. The estimates done in the low west at nightfall (a big pain) will probably be some of the most valuable of the evening. All of these fields are basically memorized and I'll refer to the charts only occasionally. If a star is in outburst, I might need to reference a brighter comp star. I proceed in what I believe is a logical order. This means basically the west to east sweep, but I generally do all the variables in a given constellation at one time. Many variables are within the same finder field and there are some so close that I need only star hop in the main scope. At full speed I am doing one estimate per minute and even faster. This rate is hard to maintain, especially when a lot of stars turn out to be in outburst. But there are other distractions as well so the final rate is often 45-50 per hour. I find this rate to be very comfortable. (60 per hour is more of a fire drill.) This means the entire sky can be scanned in about 2 hours. If I'm willing to get up in the late evening or an hour before sunrise (an ability that has gotten every easier as I grow older), I can scan areas of the sky that weren't available earlier. A perfect night will end as I'm making estimates in the low eastern sky just before dawn. These estimates are probably THE most important of the entire night.

I normally employ just 3 eyepieces, but most observing is done with only two. (I have 12 eyepieces in the collection.) For basic finding, I use a 32mm Plossl (1.25 inch) which gives 64X. From there, I directly switch to high power. If the seeing is at least average, I use a 7mm (also 1.25 inch) Nagler which gives nearly 300X. If the seeing is poor, I will use a 9.7mm Plossl. However, if the seeing permits and I'm either trying to go particularly faint or trying to split the variable with a close companion, then I'll use a 4.8mm Nagler (428X). As you can imagine, I switch eyepieces very often and need to do it quickly. This is why I'm adverse to mixing 2 inch eyepieces with 1.25 inch when I'm in high speed mode. I usually use a shirt pocket or a jacket pocket to hold the unused eyepiece, but sometimes I simply hold it in my left hand. I get away with this if I don't need both hands to cup the eyepiece to block stray light when I'm going very faint. The 32 and 9.7 eyepieces are parfocal which translates to better efficiency.

An important note is that I am tremendously near-sighted. During the day I wear contact lenses, but I find them annoying at the eyepiece. I switch to glasses where I utilize a strap so I can quickly remove them for the critical observation. This has proven comical since I have on more than one occasion "thrown" them to the ground when I forgot I didn't have the strap attached!

I have no difficulty remembering the actual estimates of my nightly stars and the order that they were observed, even the next day. The problem I have is with the time. I can remember selected observations, but that's it. So I use two methods for recording the observations, which really means getting the times correct. I use a small voice-activated tape recorder, or simply do about 10 estimates at a time and basically interpolate the time.

Because I have very little free time, and what free time I have I'd rather spend at the telescope, I've developed my own specialized data-entry program. The program is written in C for a DOS based operating system. I have what is now an old Toshiba portable with an amber screen (pretty good for maintaining night vision) and a powerful 286 processor. ;)   But the program has no graphical overhead so speed of the machine is not an issue. The idea of the program is extremely simple: ability to enter the observations as quickly as possible. This means not only minimizing the keystrokes, but also never having to hit a shift key!


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