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The usefulness of visual observations

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Matthew Templeton
The usefulness of visual observations

Hello everyone,

I'm hoping to write some informal posts to this forum addressing the value of visual observations in LPV research, and the need for continued visual monitoring of LPVs and other long-observed targets in the AAVSO observing program. In March of 2010 we started a conversation on historical trends in visual observing on aavso-discussion, particularly on the declining numbers of visual observations submitted to the AAVSO and the reasons for the decline. A number of different issues were raised in that discussion, and I hope to address many of them with posts to this forum. Today I want to preface that discussion by very briefly talking about two basic uses for long-term visual light curves in variable star research.

The longest and most homogeneous data sets for variable stars come from visual observers. Some stars have visual light curves spanning multiple centuries, but the majority of AAVSO visual light curves span from 50 to 100 years in length. In general, visual data sets for stars with good sequences are capable of tracking long-term changes of a few tenths of a magnitude over time, and are capable of detecting periodic behavior with amplitudes as low as 0.05 magnitudes. Both of these are important and valuable measurements in studying astrophysical processes that occur on long timescales.

First, LPV stars are "rapidly evolving" in the cosmic sense; changes can occur on timescales measurable in less than a human lifetime -- years or decades. These changes may include changes in mean light, period, amplitude, or light curve shape, and the appearance or disappearance of different pulsation modes. Such changes can and often do involve photometric variations of more than a few tenths of a magnitude which visual observers are more than capable of following. Any star that is correctly classified as a Mira or semi-regular variable can be followed by visual observers, and those observations will have use both in the present and in the long term. More importantly, the longer these data sets become, the more valuable they are. As the length of all of our LPV light curves grow, the more likely it is that we will detect stars undergoing long-term changes in behavior. It's impossible to predict which stars will show this, but we can predict that it will happen to some of them, if we keep watching. And LPVs aren't the only stars where this matters. Several classes of variables can show long-term changes including the R CrB stars, dwarf novae and other cataclysmic variables, symbiotic stars, and many classes of young stellar objects like T Tauri stars.

Second, when stars are strictly periodic, one can extract signals from data with large scatter, sometimes even when the scatter of individual points is larger than the signal itself. If a sufficient amount of data exist with homogeneous statistical properties, you can often use straightforward statistical techniques to extract a signal. The reason is that true "noise" will introduce random changes in a measurement, while a true signal will always push the measurement in one direction or another. Given enough measurements collected over time, the signal will begin to dominate the noise. The resulting values for periods, amplitudes, and phases will be limited by the amount of scatter in the data and the amount of data available. Instrumental data are currently the preferred means for measuring precise timings of individual maxmima (Cepheids, RR Lyrae, and delta Scuti stars) and minima (EBs). However, in the absence of instrumental data, visual data can also certainly fill in gaps in instrumental coverage over long periods of time if the precision of the derived timings is sufficient to constrain trends in maxima and minima timings.

One of the things that constrains the usefulness of visual data is that they have to be homogeneous in a statistical sense: either the data have to come from one observer who makes a consistent and unbiased measurement over long periods of time, or they have to come from a collection of observers whose statistical properties don't change over time. The latter is a reasonable assumption to make for a large number of observers all working from similar sequences and observing in a similar fashion. Most visual observers use one of a small number of techniques to measure the brightness of variables, and most visual observers have ocular acuity and sensitivity within a range typical of human eyesight. Given a sufficiently large number of observers and a sufficiently long span of observations, visual light curves have well-understood statistical properties and can be analyzed using normal statistical methods just like any instrumental data set.

For each of the years 2000 to 2009, the AAVSO received observations of between 4000 and 4800 individual stars, including LPVs, cataclysmic variables, and others; about 25 percent of these stars received more than 50 observations in a given year, averaging about one observation every week. That's just about the bare minimum coverage to adequately cover something like a Mira variable with a period less than a year.  Some stars have excellent coverage, while some are quite poorly observed.  For many stars in the AAVSO program, the number of visual observers and observations remains sufficient to allow researchers to treat them like any other data set; there remains good astrophysics to be done using these long-term light curves.

However, this will only remain true if a sufficient number of people continue to observe them; in 2010 we received visual observations for 3712 stars, of which only 760 were observed more than 50 times. The total number of visual observations submitted in 2010 (163400) is just over 1/3 of the number submitted in 1995 (385500), our peak year for visual observing. We are seeing a clear decline in the number of visual observations submitted to the AAVSO per year, along with a measurable but less dramatic decline in the number of visual observers and the amount they observe. Interestingly, the total number of visual observers is not dramatically lower, although the number of observers who contribute more than 100 visual observations per year is about 2/3 of what it was in 1995.

We hope to turn these numbers around in 2011 by providing better guidance to visual observers on what targets to select, as well as better justification of why your visual observations matter. But to summarize all of this discussion as succinctly as possible:

If you're a visual observer, please keep observing! It matters!

sfra's picture
Visual Observations

I'm working on a project looking at some specific behavior of a set of LPVs.  As part of this project, I have been getting almost daily BVRIc observations of star S ORI for the last 10 or so months.

In the past S ORI was heavily observered by Visual Observers but I've noticed that the visual observations have tapered off to a trickle particularly during the time I've been doing my intense CCD work.  I'm guessing there can many reasons for this (weather, etc) but I was curious if some Visual Observers decide to stop observing a star if they notice that there is a lot of CCD observations of the star going on.

Like a lot of projects like mine, the intense study of the star will likely end at some point.  I wonder if there is a danger that S ORI might drop off of peoples observing lists never to return.

Could this be what is happening in some cases where visual observations have tapered off?

What I use to do was only do CCD work on LPVs during the dimmer parts of their light curves but my focus of my observing has changed.

Frank Schorr


PKV's picture
Visual observations...

Perhaps there needs to be annual AAVSO awards for the top five LPV observers each year to spur LPV observation.  I have started to observe LPV's again, but was frustrated at first with my personal "error bars" on my observations.  Perhaps LPV observations can be part of a comprehensive AAVSO survey.  Kevin Paxson - PKV

Matthew Templeton
It's an interesting idea. 

It's an interesting idea.  I'd like to find a way to acknowledge people who make the greatest contributions.  The thing is the total number of visual observations you submit isn't necessarily the most important quantity.  What I'd like to see visual observers doing is covering the greatest number of LPVs with good sequences and existing long-term light curves.  That's one of the motivations of the Legacy list -- we wanted to highlight stars where we already had decades of good visual data and wanted to keep those light curves growing.  Likewise the Bulletin, since we had enough historical data to create mean curves in the past we should be able to keep them going.  What we don't want is people observing stars that are so poorly or infrequently observed that their observations won't be used for anything.  That's where the observers have to get feedback from headquarters and from the broader research community as to what's interesting.  If we can give that kind of advice to the observers and the observers turn around and hand us more and better data, I'd love to give some formal recognition of that effort.

BBI's picture
Maybe observers can be

Maybe observers can be motivated if there is more personal info about their visual observations (a page with statistics and "rankings" (by country, per number, your 10 most observed stars, ...)). That's missing now...

Matthew Templeton
Visual observations

I think it's hard to generalize why visual observations have dropped off -- as the discussion back in March 2010 showed, there are a number of reasons.  I think some people are put off by CCD coverage, yes.  That's unfortunate, since as you indicate in your note, yours isn't intended to be a long-term project that will continue on forever.  ASAS coverage has also been cited as a reason many people don't observe LPVs, but again, there's no guarantee that ASAS data will be available in perpetuity, and there's also no guarantee that you can easily merge instrumental data with visual data since they're not the same.

On a related topic, I'm working out the final formatting details for the new edition of the LPV Bulletin that we're releasing at the end of February.  One of the extra pieces of new information I want to include with each star in the bulletin is the number of visual observations that the star received in 2010 along with the largest gap in coverage in 2010.  This will replace the "needs more observations" tags we used to have.  That might motivate people to concentrate more on stars that are poorly observed.

MDAV's picture
Visual Observations


Here is my experience. Although not strictly on this particular topic I think they are related.

1. I do not "drop" but various effects may make it appear so.

2. There are only about three stars that I do religiously- R Leo, R CrB, and R Com. 

3. I prefer to "reset" my eyes after each estimate-then redo the estimate several times. This eats up time -especially when working near my instrumental limit. So I am not and never will be a particularly prolific observer.    

4. I will very often find that more southerly stars I had intended to re-visit have gotten too low in the sky while I have been doing others. 

5. I have a rule of thumb that I do not report "Fainter Than" observations when the limiting magnitude e is brighter than 14.1 (I use the R CrB sequence stars for this). While I don't bother to try observing stars I know I will not see there are some with minima around mag 14 that I will try anyway. And I am careful to NOT check what other observers have seen until I submit my observations so I don't always know that I should probably omit these stars. I recognize that this is probably not the most efficient use of time-but I am a firm believer that we should go for the tougher objects. 

5. As is probably true for many observers my day job prevents me from observing from a set schedule. I do mostly LPVs but I cannot keep to the weekly schedule the Visual Observing Manual recommends. Although not a LPV, I made 4 times as many observations of Eps Aur in the 1982 eclipse than the paltry few I was able to get this time.

6. Interests do change over time. I did a lot of variable star estimates in the 80's  then got into some photography and DSO observations. i have only gotten back into doing variables the last four years or so.

As for background: I have only had an AAVSO observer code for a couple of years but have been an amateur astronomer for thirty years. So I  do not consider myself green or inexperienced and do not need the level of support that a new observer would need. I did notice on the recent general bulletin board discussion some condescension toward visual observers - or at least they read that way to me- from some posters I noticed that this was not from AAVSO staff.

I hope this explains a little about at least one observers' traits.


MDAV's picture
Visual Observations

I would not rule out the increasing use of automation as a factor in the decline of visual observation. The bulletin stars may be in the computerized databases of many telescope controllers but my experience is that that does not make it useable as such for visual observations. Unlike DSOs the target star is rarely immediately apparent. It still takes the use of charts. And since many people went to a computerized scope to make finding easier...

puj's picture
Has any future visual observations?

I read in Sky&Telecope, october 2011 issue, some interesting statement made by Arne Henden, present AAVSO Director. These opinions  are in clear opposition to what is being stated in this forum and in the AAVSO manuals:

"Visual observers, explains Mr Henden,  will still be needed but for the highest ciectific value they wil need to perform specific observations-watching for an outburst of a rare class of star, making time-critical observations when robotic facilities might be clouded out, measuring brightness of close optical doubles (¿¿) and so on."Just as professional surveys have nearly eliminated amateurs discoveries and digital techniques have supplanted visual discoveries of novae and supernovae, amateurs need to be flexible and undertand that as some doors close, others open up. Demand for visual observations will transition to new directions".

After reading this I think you should clearly clarify the future, because it does not make sense to promote in this page  visual estimations of LPV stars at lest for AVSO legacy stars, and on the other hand to state in the most important magazine that visual observers should change completely the way they observe.

By the way , If possible I would like to know what is the accuracy of our competitors (All sky robotic

telescopes), making observations of LPV, and who will do the job to supply tones of observations from this appreciated equipments to the official databases, perhaps far away fro AAVSO archives.

Best regards


HQA's picture
future visual observations

Hi Francisco,

The key phrase here is "for the highest scientific value", along with the understanding that this article was discussing the future.  My basic premise is that there will be automated surveys in the future that cover the entire sky every night, and that such surveys will either continue indefinitely or will be replaced by other surveys that accomplish the same thing.

However, I have a fair amount of experience dealing with surveys and automation, and I am fully aware that no survey is perfect - they all have their limitations.  You can see the potential accuracy of the competitors by looking at some of their LPV light curves; check out S Ori or the current light curve of the week, U Tuc, on the ASAS web site: and then look at the same stars using LCG light curves with only visual data enabled.  There are lots of other cases, though, where there are offsets between visual and CCD, or where those offsets differ depending on the position in the light curve (perhaps blended stars so that the minimum is wrong), or whether the star is too bright or too faint for the survey limits.

That is one reason why the AAVSO will be initiating an exciting new campaign over the next few months.  We want to get dense visual coverage on a subset of stars at the same time as we get modern CCD photometry from the AAVSO's own 2GSS survey, so that we can find the pathological stars that a CCD survey can't measure properly, and also see if we can transform between visual and electronic systems so that the statistical properties can be extended between past visual observations and future electronic measures.  That means all visual observers are going to be plenty busy for the next few years, helping us find the answers to those questions.  The key word there is "busy": we need your observations!

Beyond that?  If you want your observations to be scientifically useful *today*, then you have to participate in today's hot topics, which are primarily transient objects.  Next week or next month, there may be another hot topic. If you don't feel the urge to get your name into the spotlights, then continuing to observe your old favorites, or helping monitor the pathological LPV cases, will always result in scientific contributions, just not instant fame. Visual observing has many other uses too, such as an entry into variable-star observing, a low-cost method of measuring stellar brightness, or just enjoying the night sky.

I know visual observations will continue to be needed into the forseeable future.  I just don't think that you can put blinders on and assume that how you observed yesterday will be just as useful tomorrow.


SMIK's picture
Visual observations

I am starting my visual observing program and have been studying a lot of the AAVSO charts to find variables that I think I can find.

But given all the discussion on this topic in the earlier posts above, I want to be sure that the stars I report on will be useful. Any suggestions?

(I live at 37.17N and 113.66W in southwestern Utah - approx Bortle 4 skies suburban/rural transition - use a 10" SCT - and am a novice)


Matthew Templeton
Visual observations

Hi Mike,

It is hard to summarize "what's useful" in a forum post, and this topic continually under discussion both public and private.  We've established a number of formal lists of stars that we strongly encourage observations for.  These lists are made up of stars for which all of the following are true: (a) the AAVSO already has long-term visual light curves for them, (b) they are easily observable by visual observers through some or all of their range, and (c) they are objects of current interest as gauged by the number of publications for them in the scientific literature.  You can find these lists at the LPV Section website (on Google):  You can either browse the site or go directly to the download page with lists (PDF, CSV, and XLS) that you can grab and review for yourself.  If you use a spreadsheet program, you can easily sort a CSV/XLS file by Declination to find those best suited to your site. [EDIT: I realized that at least one of the lists does not include RA/Dec, but that can be easily remedied.  I will work with the Section leaders to replace those files with ones that include RA/Dec within the next day or so.  For now, you can go by the Constellation name to gauge whether it's visible to you at your location right now.]

I should make a comment that doesn't often get stated, but it's true of all observations be they visual, CCD, or PEP, and even robotic data too: we can not guarantee that anyone will ever use your observations.  That's as true for the most observed variable as for the least.  However, we think it's likely that your observation will be used if you concentrate on stars in the LPV lists (or the CV lists for that matter) simply because there's a proven history of these data being used by the research community.  It's not out of the question that someone will use or want observations of other stars, and we sometimes get requests for data on stars for which we have no observations in the AID.  To some extent we have to guess what will be useful, and we're biased toward objects that we already know are well observed. 

We also bias the lists toward stars for which we already have long-term light curves in part because there is a good chance (but not a guarantee) that future researchers might be able to explore long-term changes in variations if we have a continuous record.  For that reason we continue to encourage visual observations: the existing time span and statistical homogeneity of long-term visual light curves make them ideally suited for studying long-term changes.  The longest CCD light curves today are about 20 years long.  The longest visual light curves are over 200 years long.  There's a lot of interesting astrophysics to be explored in that gap, and there's no reason to discontinue the collection of visual data that have proven adequate for studying these phenomena.

When we point observers toward a fixed list, there's some risk that (a) we've either guessed incorrectly that researchers will be interested in data for that star, or (b) we're pointing people away from something that might be interesting in the future.  But given that we see significant declines in coverage of many variables with long-term light curves, the LPV Program, Legacy, and Binocular list are a way of focusing peoples' attention on these stars and lightcurves that we know have good potential for scientific use.

If you have any specific questions about stars in the LPV Program, Legacy, and/or Binocular lists, feel free to contact me personally via email.


puj's picture
Your reply to Sky and Telescope. March issue

I enjoyed very much reading your reply to the article about AAVSO's Centennial published in january issue, related to the importance of visual observations for the AAVSO. The letter is signed by Matthew R. Templeton, Mario Motta and Arne A. Henden.

I would like to emphasize one of the topics that I think it was not covered in previous discussions. I copy the whole paragrapgh, because it is very important;

"Visual observing also remains a low-cost and low-technology means for all astronomers to participate in meningful scientific data collection; it provides this opportunity to a far larger global community than digital observing alone possibly could. It has also been proven as a gateway for young people to become involved in astronomy"

In the same march issue  a summary of AAVSO observations, mostly visual, carried out monitoring Epsilon Aurigae eclipse, are presented by Aaron  Price.

I appreciate all this info that clarifies the future of visual observations.

Visual Observing is not only do observations for science...


"Visual observing also remains a low-cost and low-technology means for all astronomers to participate in meningful scientific data collection; it provides this opportunity to a far larger global community than digital observing alone possibly could. It has also been proven as a gateway for young people to become involved in astronomy"


I cannot agree on this viewpoint more. In China, there are few amateurs know variables, especially visual obseration of variables; even in the most active high-school-astronomy-societies, student-amateurs know little about variables. Most of amateurs in China cannot believe, that they could contribute to science by such a simple means; it is quite similar to the most embarrassing thing, that people think the cost of a telescope must be incredible huge. (It is ludicrous that someone may consider a ordinary 6 inch Newt expensive as a car, but really I meet these persons everyday.)

I have to admit, that some of amateurs have the capacity to afford high-technology equipment, and doubtlessly they can do a lot with its help; But we should not therefore ignore the majority. Especially in developing countries, the majority and the most active part of amateurs are the workers, students, etc. who cannot afford expensive equipment. Nevertheless, they have a lot to do contributing to science, which are simultaneously most joyful.

I just benefit from these, such as visual observing of variables and meteors; without the experiences doing observation myself, I would not know and love astronomy. I always remember and enjoy the storys of those great astronomers, professional and non-professional, which telling how a ordinary boy or girl be excited by the sky and fell in love with astronomy. So there is a firm faith in my mind, that it is my duty to spread the idea to let more amateurs be aware of their potential, in both contribution to science and their own joy, or, in other words, the dignity of being amateurs.

Now I am in great glee, for many of my friends have become one of the TRUE OBSERVERS of variables. It is a door giving a totaly new world to them, as it was to me several years ago, and they really enjoy it. Enthusiasm; It is always the most motive power among all, and astronomy doubtlessly has the gifted advantage of inspiring humans' enthusiasm. Stars are generous, regardless of how much money you have. This is what I have learned from visual observing.

CQS, China

puj's picture
The limitations of the automatic surveys (update)

I read in Sky and Telscope magazine, May 2012 issue, that the variable stars automatic surveys have important limitations leaving to amateurs, both visual or with CCD, an important niche to keep observing. It seems that both: the present catalina Sky Survey and the Catalina Real-Time Sky survey, and the future one dubbed as Large Synoptic Survey Telescope, keep important areas unattended. The Catalina survey can't measure stars brighter than 12th magnitude, as they can saturate the pixels. Furthermore, the surveys avoid the broad band of the Milky way because the number of stars is too numerous.

The next Survey  called Large Synoptic survey, to be initated by the end of this decade will measure stars between 16 and 24,5, while the present ones concentrate between 12,5 magnitude and 20.

The article points out that amateurs in the coming decades will have plenty of work monitoring the new real variable stars discovered by these surveys

lmk's picture
Visual observing issues

Well, Its quite likely the main culprit for the steady decline in visual observations since the mid-90's is the simultaneous rise in availability of "turn-key" CCD systems and telescopes! Former visual observers have gone CCD, and new observers tend to jump right into CCD and skip visual. Thats just the way things changed and the result of natural human reactions. And this natural human impression is that CCD is more accurate, goes fainter, and is a permanent record vs. "old fashioned" visual.

This is certainly true to a degree, but the typical CCD accuracy is highly variable depending on many factors, including the experience and knowledge of the observer in proper techniques and operation of the equipment and reduction of the data. Looking at the CCD data in the AID, you can see much spread between different observers, just as you see spread in the visual data. This is likely due to equipment, techniques, error handling and comp star selections being different between observers. So, the practical accuracy of CCD data is not overwhelmingly better than visual data, over a number of different observers.

I feel this latter point is something many observers overlook. To really make accurate CCD observations (to milli-magnitudes which it is theoretically capable) consistently requires a large investment of resources - equipment, education, practice and experience. On the other hand, visual observing is far, far easier! And with some practice and good techniques (far less work than CCD!) it can be accurate enough for many, if not most scientific studies.

One of the things that strikes me as so skewed, is the unequal worldwide distribution of VSO observers. Areas such as the far east (China,etc.), Southeast asia, Indonesia, Africa, India which have the majority of human population, have practically no VSO observers! I think our Chinese friend who posted earlier makes some interesting points about why this may be so. But why is the impression of these people so skewed against observing? Certainly, if the economic conditions are difficult, that would preclude acquiring the basic equipment or even the free time to observe. But many of these areas, China in particular, are devloping rapidly, and it would seem that many people would have the resources and time to devote to VSO!

Maybe AAVSO needs to make a specific Chinese language version of its website (like we already have a Spanish version) that can be easily searched by the population over there? I specifically mention China due to its economic growth and huge population, as being a key expansion into this untapped resource of potential observers!

Mike LMK

BSJ's picture
Chinese version of the Visual Observing Manual

I don't know that we have the resources to produce and maintain a full-up Chinese language version of our website, but a step in the right direction was the fine translation of the Manual for Visual Observing of Variable Stars done by CQS and available through our website here:

That should certainly help people get started.


On the reason of the lack in VSO in China


One of the things that strikes me as so skewed, is the unequal worldwide distribution of VSO observers. Areas such as the far east (China,etc.), Southeast asia, Indonesia, Africa, India which have the majority of human population, have practically no VSO observers! I think our Chinese friend who posted earlier makes some interesting points about why this may be so. But why is the impression of these people so skewed against observing? Certainly, if the economic conditions are difficult, that would preclude acquiring the basic equipment or even the free time to observe. But many of these areas, China in particular, are devloping rapidly, and it would seem that many people would have the resources and time to devote to VSO!

Mike LMK


Ignorance; I answer, when you ask why people in China do not observe, despite the free time and the clear dark sky.

Just as you say, the main stream in China is to grow rapidly in economy. The authority of education hold some competition in order to encourage high-school-students to contribute to science, but from my point of view, the means is not suitable at all. The result is somewhat a farce that students do not think by themselves but go to institute to beg for experts' help. They are obsesses in pretending doing some "science" about which they know nothing;- They even want not to learn something at all! They do not care about the history of astronomy, the arduous but joyful work astronomers do; they just want the result, to win the competition. Adding to the judge who we even never know before, it is no wonder that a "research" on the Alien should win the first award. 

Innovation. What a beautiful pretext to be lazy on thinking! This is the reason why they do not like observing. "It is too hard," they say,"and stupid." But, without arduous observing, I ask, how could we know the nature?

Students in China spend too much time on some strange, difficult, but useless excercises. Most of them indeed have little free time. They are hardworking, but not in correct directions. Unfortunately, when they are aware of the misfortune, they attribute these all to "hardworking". They are therefore loath to work hard in science, as they have been defeated by the ferocious useless exercises. They have confounded diligence with vain repeated work. Unfortunately, again, the award of the science competition is a useful to be admitted to better university, so they think of ask "professors" to help.

Most parents are always worried about their children's future, from primary school to job. I wonder what they are worried about. Maybe, they fear that they would be left behind the rapid growth of economy. The condition of life become doubtless better, but the worries increase at the same time. The stream is terrible, it corrupt our children's candor and enthusiasm.

The education damages the majority, it makes them not to be aware of who they are, what they want, what science is, and how they are linked with science. (For instance, most Chinese students think science is always right...) Nevertheless, some minority survive, in which stand some of my friends. 

There must be some who get the secret to enjoy felicity, while others not. It depends on oneself. Felicitous persons will be happy in any situations, rich or poor. They always have free time and enough money to enjoy life. But the others will always be sad even if they are rich. I am sorry that in China, the former are minority.

Come back to ignorance. In China there is only one magazine popularizing astronomy called Amateur Astronomer. But it is embarrassing that many articles telling some same things repeatedly occupy the magazine. I am very sad about that, but it is said that most readers like to read them most! (I wonder who these readers are!) Attracting news, tedious report on astronomical education, with no a thread of genuine and profound thought. In this forum, we have got lots of good ideas on Chinese astronomical education, but there should be not any like this in the magazine! -The readers like that. -Alas! Is our magazine aimed to feed people by useless gossips (of course some of them will be fond of this), or to enhance their knowledge and understanding to astronomy and inspire them to contribute to it? It is a truth, that when we enhance ourselves, we have to pay sweats and suffer toil. 

Cheng Simiao, CQS

SET's picture
Thanks for thew input

I'd like to thank Cheng from China for bringing up a good discussion here. I am a Earth/Space science teacher at Avon Park High School in Florida. For the past 15 years or so, at middle grades (which I just moved out of) to high school, Florida went to Integrated Science, which I hated. Very little astronomy and other earth/space sciences. Now that we have a true Earth/Space course back, I plan on introducing my students to varialbe stars. I am even planning to show Chuck Pullen's ppt on variable star observing.

I can definitely understand where Cheng is coming from. Perhaps China's schools need to introduce a more hands-on approach. Perhaps even taking the students out at night with telescopes. I plan on doing this.

I'm pleased Cheng has caught the thrill of variable stars. Keep up the good work.


Chris Stephan   SET

Robert Clyde Observatory

Sebring, Florida  USA

douglasfowler's picture
Visual observation.

I would like to thank both Cheng and Chris Stephan for their comments. (I was an MVAS member once, a little after your time, Chris, but I'd heard much about you from my collegue John Beaver and our late mutual friend Roy Mimna).

It is fully conceivable that someday much of the sky will be surveyed automatically for every kind of object. But what does this mean for us? What will it mean to know anything? What does it even mean "to know" something? I just throw out these rhetorical questions to generate conversation.

I observe variables in the same careful way that I look at wildflowers (or the way I used to ramble around in the mountains, the way I even climbed a few), or the same way I do carpentry. I want the experience of nature. I am not after awards, certificates, etc. I just like the chance to sit outside at night and do some careful observations of this one part of the wilderness overhead.

This season, I like hearing the katydids, the gray tree frogs, the changes in wind. I like the quiet of night (what little remains of it). I like the time to slow down. I like the time to reflect. And sitting with the charts, a cup of coffee, maybe some jazz or classical music (Peter Van De Graff late into the night), I get to experience a little of what the Chinese poets described as the life of the immortals (Go back and read your Burnham's for some translations). Without this, none of it would be worthwhile for me. What was all that stuff that Peltier wrote about? Or H. A. Rey? Or that Raymo captured in his 1985 "The Soul of the Night"? Does any of this mean anything anymore? 

Observing also gives me ongoing practice in the visual and manual navigation of the sky. This is a skill that certainly helps in teaching my evening astronomy labs.  And I hope to pass on a little of that skill to my astronomy students.  All of our opportunities for direct experiences with nature are threatened. I want my students to have a sampling of some of that kind of experience.    

SET's picture
nice comments

Hi Doug,

Thanks for the nice comments about Roy and John. I trained them both in variable stars. I was sorry to hear of Roy's passing a few months ago. John was a real go getter. I thought very highly of both.

Those are good comments you made. My goal is to contribute observations for the betterment of science. But, I do not ever want to loose out on just enjoying the beauty of the night sky.

Chgris Stephan  SET

Robert Clyde Observatory

Sebring, Florida  USA

SET's picture
please email me


Please email me seperate at

I'd like to discuss MVAS stuff with you. Thanks.


Chris Stephan  SET

MOR's picture
Return of experience with LPV sky survey.

You can follow Mira Stars with CCD and DSLR cameras. Now if you do that, you have to solve many problems.

You can’t use an all sky survey, because the light variations are about three magnitudes to six for some of them.  You must adapt each integration time for each star. For the brighter stars, time is very short (3 seconds), you must make many pictures of the same field to reduce the scintillation. For some of them, it's necessary to adapt the integration time at maximum light and minimum. The dynamic of CCD camera can give a good measure for maximum of five magnitudes not more. In field with many stars, at the minimum, the quality of measure depends of seeing and focal length that you use. For the same reasons, It's very difficult to follow more than one star in a field of stars with good quality (RMS = 0.01 magnitude). It’s a good news, an expensive wide field camera is not solution. Even if some Mira are very bright, a good sky and good weather conditions are the best way.

With CCD, You have better result; if you make daily observation, a weekly follow is not a solution. If star is target of my sky survey, it’s no problem if the visual observation is reduced. The visual observations don’t give a better result if you add this one on Fourier analysis for example.  We can use it only to verify, if there is trouble at minimum light or other trouble with our filter. Now, for any reason, if I stop my sky survey of LPV, I think it’s possible to inform the AAVSO community that target will be not follow by me in the future.

To know that, it's necessary to experiment, if you see my first measures and the last one, perhaps you have noted that the quality is increases. Now, for return of experience, it takes time, one period of Mira or two for some of them.

With specific sky survey, a small goto telescope with DSLR or CCD camera is very efficient, certainly more than big Dobson for the same price.

Etienne Morelle

Sirene Observatory


lmk's picture
The many advantages of visual

No doubt, the proliferation of amazingly complex featured electronics these days leads many folks to believe that they are necessary to function in the present world. Certainly, one the greatest insights of Steve Jobs was his ability to envision exactly those products which would be attractive to the masses.

Yet, one needs only look at 20th century history to realize that the greatest human scientific and technical achievements, were accomplished well before the iPhones, PC's or internet even existed! Eg. Nuclear bombs/energy, men on the moon, 5meter class optical telescope, heart/lung transplants, vaccines, DNA structure/function, quantum mechanics, general relativity, etc. One can ask what similarly classed discoveries have occured since the iPhone came out? (Well maybe the Higgs boson, but its not a sure thing yet ;)

Maybe this started out a wee bit OT, but I am just relating the "big picture" of how things can get skewed out of proportion. Do you NEED a CCD to do worthwhile astronomy? Obviously we know the answer! One of my other pursuits is scientific meteor observations. I can do that with nothing more than a lounge chair, pen and paper, and my naked eyes. Its still the primary mode of studying the distributions of the remnants of our solar systems creation in the vicinity of our planet.

Similarly, visual VSO can be done with the simplest of equipment too. Even basic binoculars allow following a wide range of important objects. A moderate size telescope allows useful visual observing of almost anything. And, a large dobsonian type operates close to the realm of the CCD. Whats your pleasure?

As most die hard CCD operators are well aware, the MTTF system failure equation shows how the more complex a system, the higher the probability of it failing overall, unless each component of the complex system is made more reliable. As the number of components increases, the difficulty of maintaining overall reliability increases rapidly. There have been multiple examples in these forums of anomalous CCD measurements which have required extensive troubleshooting to resolve. As well as surprising failures of components due to overestimating their reliability (eg. Tom Krajic's lightning strike).

On the other hand, the human visual system has been optimized to a very predictable system availability level, as a result of evolution and natural selection over millions of years of time. With a modest amount of training a visual observer can be accurate to 0.05 - 0.1 magnitudes, and do it reliably and repeatably. For a CCD operator to achieve the same level of accuracy and reliability takes a substantial investment of capital and experience time and education.

Also, visual observers can observe things on short notice with minimal setup time, and while travelling away from home, and under adverse conditions which would shut down automated scopes.

Given how effective and easy visual observing is, I remain surprised why the trend is still so heavily in favor of the "tough road" of CCD for new observers.

Mike LMK

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