Click the left mouse button to start

AAVSOVariable Star Telescope Simulator

Learn how to have funmaking variable star observations!

To change to the To change to the next slide, click next slide, click on the left mouse on the left mouse button.button.

Some of the Some of the detailed photos detailed photos may take a may take a moment to load-- moment to load-- please wait.please wait.

How to operate the How to operate the telescope simulatortelescope simulator

AAVSO member Lew Cook’s 44-cm newtonian telescope

In case of difficulty...In case of difficulty...

If you have any If you have any problems with this problems with this system or in system or in understanding the understanding the material, please material, please stop and ask a stop and ask a helper for helper for assistance.assistance.

And now, let’s And now, let’s begin!begin!

Variable Star Observers Wear Many Hats!

Welcome to the AAVSO Welcome to the AAVSO telescope simulator!telescope simulator!

Today, you will learn Today, you will learn how to perform a how to perform a valuable scientific valuable scientific measurement--star measurement--star brightness.brightness.

You’ll also learn how You’ll also learn how much fun it can be much fun it can be to do real science to do real science from your own from your own backyard.backyard.

What you’ll learnWhat you’ll learn

This learning This learning experience will experience will take about 15 take about 15 minutes.minutes.

In addition to In addition to estimating estimating brightness, you’ll brightness, you’ll learn how to find learn how to find variable stars with variable stars with AAVSO charts.AAVSO charts.

Supernovae are Variable Stars too!

What you’ll learnWhat you’ll learn

We’ll also cover how We’ll also cover how scientific data can be scientific data can be useful even when it useful even when it contains “noise”.contains “noise”.

You’ll learn that your You’ll learn that your observations can be observations can be very valuable, even very valuable, even while you’re learning while you’re learning to make better and to make better and better estimates.better estimates.

CCD brightness data from long time AAVSO Member Lew Cook

Constant (comparison) star

Variable star

Astronomy needs data!Astronomy needs data!

The sky is full of The sky is full of wonderful things wonderful things to see.to see.

But, just looking But, just looking at its beauty often at its beauty often doesn’t provide doesn’t provide answers to the answers to the riddles of the riddles of the universe. universe.

Hubble Space Telescope

Astronomy theories need Astronomy theories need data!data!

Most of the Most of the discoveries discoveries astronomers astronomers have made have made about the about the universe needed universe needed light light measurements measurements to confirm or to confirm or suggest suggest theories.theories.

(Time)

Data is information from Data is information from instrumentsinstruments

There are all kinds of There are all kinds of instruments instruments astronomers use to astronomers use to make measurements make measurements of star brightness.of star brightness.

We call these We call these measurements measurements photometric photometric data.data.

Photometric means Photometric means light-measuring.light-measuring.

Your eyes are your Your eyes are your instrumentsinstruments

You are going to You are going to use your own eyes use your own eyes and a special and a special technique for technique for making photometric making photometric measurements.measurements.

The technique is The technique is called: called: Interpolation of Magnitude.

What is interpolation?What is interpolation?

Interpolation is is a word scientists a word scientists use when a use when a measurement is measurement is estimated estimated between two between two known values.known values.

People interpolate People interpolate all the time!all the time!

InterpolationInterpolation

Your car’s gas Your car’s gas gauge needle is gauge needle is half way between half way between empty and 1/4 empty and 1/4 tank.tank.

You You interpolateinterpolate you have 1/8 of a you have 1/8 of a tank left--time to tank left--time to get gas!get gas!

E F

1/21/4 3/4

Interpolating star Interpolating star magnitudemagnitude

Making a Making a brightness brightness estimate is easy in estimate is easy in theory but theory but requires some requires some practice.practice.

We call the We call the measurement of measurement of brightness the brightness the star’s star’s magnitude.magnitude.

Interpolation of magnitudeInterpolation of magnitude

We estimate the We estimate the brightness of the brightness of the variable star by variable star by using at least two using at least two stars of known stars of known brightness; one brightness; one brighter than the brighter than the variable, one variable, one fainter.fainter.

Andromeda Galaxy (C. Pullen)

Interpolation of magnitudeInterpolation of magnitude

Just like the gas tank Just like the gas tank example, if a star’s example, if a star’s brightness seemed brightness seemed about half way about half way between two stars between two stars that were known to that were known to be magnitudes 5.0 be magnitudes 5.0 and 6.0, what is the and 6.0, what is the magnitude of the magnitude of the variable star?variable star?

Crab Nebula (C. Pullen)

Interpolation of magnitudeInterpolation of magnitude

That’s right -- half That’s right -- half way between 6.0 way between 6.0 and 5.0 is and 5.0 is

5.5!

How to find a variable starHow to find a variable star The AAVSO makes The AAVSO makes

thousands of star thousands of star charts (sky maps, like charts (sky maps, like road maps) used to road maps) used to find and estimate the find and estimate the magnitude of variable magnitude of variable stars.stars.

Because all AAVSO Because all AAVSO observers use the observers use the same charts, our same charts, our results can very good, results can very good, and can be compared and can be compared with each other’s.with each other’s.

How to find a variable starHow to find a variable star

A copy of a chart you A copy of a chart you will use is next to the will use is next to the monitor. It is for W monitor. It is for W Cygni, a star you can Cygni, a star you can find with binoculars find with binoculars from you own yard.from you own yard.

But, first let’s try a But, first let’s try a simple lesson in simple lesson in interpolation and using interpolation and using star charts.star charts.

Variable and comparison Variable and comparison starsstars

Look at the example below. The variable is shown between the four focus lines. The magnitudes of the comparison (“comp”) stars are shown on the chart next to the stars (64,51,91, etc.).

Variable

Decimal points can be Decimal points can be confusingconfusing

Note that the star magnitudes are actually decimals but wedon’t show the decimal point because it could be confused as a star. So, the magnitudes below are really 6.4, 5.1, 9.1, etc.

Variable

A big magnitude number A big magnitude number is faint, a big dot is bright!is faint, a big dot is bright!

The brighter the star is, the smaller its magnitude number. 5.1 is brighter than 6.4.On the chart, notice that the dot is bigger (brighter) for the 5.1 star than the 6.4 star to its left.

Variable

Making your first estimateMaking your first estimateIs the variable brighter or fainter than the brightest (5.1) star?

Making your first estimateMaking your first estimateIs the variable brighter or fainter than the brightest (5.1) star?Fainter!

Making your first estimateMaking your first estimateIs the variable brighter or fainter than the next brighteststar (6.1)?

Variable

Making your first estimateMaking your first estimateIs the variable brighter or fainter than the next brighteststar (6.1)? Fainter!

Variable

Making your first estimateMaking your first estimateIs the variable brighter or fainter than the next brighteststar (6.4)?

Variable

Making your first estimateMaking your first estimateIs the variable brighter or fainter than the next brighteststar (6.4)? Brighter!

Variable

Here comes the gas Here comes the gas gauge!gauge!

So, the variable is brighter than 6.4 but not as brightas 6.1. What are you going to do with those numbers? Interpolate!Interpolate!

Variable

Interpolation is an Interpolation is an educated guesseducated guess

Is it about half way between 6.4 and 6.1?Then, your estimate would be 6.2 or 6.3. But, which one?

Variable

Use your feelingsUse your feelingsMaybe you think it is just a little brighter than midway.Your estimate would be 6.2! A little fainter, your estimate would be 6.3.

Don’t try to think what it should be, just go with the flow.

Your ability to feel the best answer will get betterwith practice.

Making your first estimateMaking your first estimate

But, whatever your But, whatever your estimate, estimate, congratulations on congratulations on your first variable star your first variable star observation!observation!

Write your result on Write your result on the observation form the observation form you were given.you were given.

Why do we call it anWhy do we call it an

Different people will make different Different people will make different estimates of brightness using this estimates of brightness using this method. We all see the world method. We all see the world differently.differently.

Yet, all the estimates are “right”! Yet, all the estimates are “right”! There is no one correct answer.There is no one correct answer.

All scientific measurements have All scientific measurements have variation. We call it variation. We call it errorerror or or noisenoise..

I thought scientists only I thought scientists only used exact numbers!used exact numbers!

Well, a number can Well, a number can never be never be tootoo exact in exact in science, especially science, especially astronomy. But, all astronomy. But, all measurements are measurements are really estimates to a really estimates to a certain certain precisionprecision. The . The trick is understanding trick is understanding what that precision is.what that precision is.

Precision in Precision in datadata The graph on the The graph on the

right is a portion of right is a portion of the AAVSO data that the AAVSO data that show the change in show the change in brightness over time brightness over time of a star called SS of a star called SS Cygni.Cygni.

We call this a We call this a lightlight curvecurve..

SS Cygni is located SS Cygni is located in the constellation in the constellation of Cygnus the Swan.of Cygnus the Swan.

2449402 11.92449403 11.62449403 11.72449403 122449403 11.72449403 11.92449403 11.92449403 11.62449405 11.82449405 11.92449406 11.62449406 12.0:2449406 11.92449408 122449409 122449409 11.82449409 11.82449410 122449410 11.92449410 11.92449411 122449411 11.82449411 12.12449411 12.22449412 122449412 11.92449413 11.82449413 11.52449414 122449414 11.82449415 12.12449415 11.92449415 12.12449415 11.92449415 11.92449415 12.22449416 12.12449416 12.12449416 12.12449416 11.82449416 11.6:2449417 11.82449417 11.82449417 122449418 122449418 11.62449418 11.72449418 12.12449418 11.92449418 122449419 122449419 11.62449420 11.52449420 11.82449420 11.72449420 11.72449421 11.82449421 11.82449421 122449421 11.82449421 11.72449421 11.62449421 11.62449422 11.52449422 11.92449422 11.92449422 12.22449422 11.82449422 12.12449422 11.82449422 11.92449423 11.9

SS Cygni Partial Light Curve(90 Day Interval)

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Precision in Precision in datadata SS Cygni brightens SS Cygni brightens

dramatically every few dramatically every few months.months.

Each dot represents a Each dot represents a measurement made by measurement made by an AAVSO observer an AAVSO observer somewhere in the somewhere in the world. We have world. We have records on some stars records on some stars back to 1911!back to 1911!

You can make You can make measurements too like measurements too like these too!these too!

2449402 11.92449403 11.62449403 11.72449403 122449403 11.72449403 11.92449403 11.92449403 11.62449405 11.82449405 11.92449406 11.62449406 12.0:2449406 11.92449408 122449409 122449409 11.82449409 11.82449410 122449410 11.92449410 11.92449411 122449411 11.82449411 12.12449411 12.22449412 122449412 11.92449413 11.82449413 11.52449414 122449414 11.82449415 12.12449415 11.92449415 12.12449415 11.92449415 11.92449415 12.22449416 12.12449416 12.12449416 12.12449416 11.82449416 11.6:2449417 11.82449417 11.82449417 122449418 122449418 11.62449418 11.72449418 12.12449418 11.92449418 122449419 122449419 11.62449420 11.52449420 11.82449420 11.72449420 11.72449421 11.82449421 11.82449421 122449421 11.82449421 11.72449421 11.62449421 11.62449422 11.52449422 11.92449422 11.92449422 12.22449422 11.82449422 12.12449422 11.82449422 11.92449423 11.9

SS Cygni Partial Light Curve(90 Day Interval)

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Precision in Precision in datadata

The magnitude is The magnitude is plotted on the Y plotted on the Y axis (up and down)axis (up and down)

The day and time The day and time of the observation of the observation is plotted on the X is plotted on the X axis (left and right)axis (left and right)

2449402 11.92449403 11.62449403 11.72449403 122449403 11.72449403 11.92449403 11.92449403 11.62449405 11.82449405 11.92449406 11.62449406 12.0:2449406 11.92449408 122449409 122449409 11.82449409 11.82449410 122449410 11.92449410 11.92449411 122449411 11.82449411 12.12449411 12.22449412 122449412 11.92449413 11.82449413 11.52449414 122449414 11.82449415 12.12449415 11.92449415 12.12449415 11.92449415 11.92449415 12.22449416 12.12449416 12.12449416 12.12449416 11.82449416 11.6:2449417 11.82449417 11.82449417 122449418 122449418 11.62449418 11.72449418 12.12449418 11.92449418 122449419 122449419 11.62449420 11.52449420 11.82449420 11.72449420 11.72449421 11.82449421 11.82449421 122449421 11.82449421 11.72449421 11.62449421 11.62449422 11.52449422 11.92449422 11.92449422 12.22449422 11.82449422 12.12449422 11.82449422 11.92449423 11.9

SS Cygni Partial Light Curve(90 Day Interval)

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Precision in Precision in datadata

You can see the You can see the noise in the data.noise in the data.

Note that the Note that the curve is not a nice curve is not a nice straight line.straight line.

Rather, it is a Rather, it is a wide band of wide band of individual individual observations.observations.

2449402 11.92449403 11.62449403 11.72449403 122449403 11.72449403 11.92449403 11.92449403 11.62449405 11.82449405 11.92449406 11.62449406 12.0:2449406 11.92449408 122449409 122449409 11.82449409 11.82449410 122449410 11.92449410 11.92449411 122449411 11.82449411 12.12449411 12.22449412 122449412 11.92449413 11.82449413 11.52449414 122449414 11.82449415 12.12449415 11.92449415 12.12449415 11.92449415 11.92449415 12.22449416 12.12449416 12.12449416 12.12449416 11.82449416 11.6:2449417 11.82449417 11.82449417 122449418 122449418 11.62449418 11.72449418 12.12449418 11.92449418 122449419 122449419 11.62449420 11.52449420 11.82449420 11.72449420 11.72449421 11.82449421 11.82449421 122449421 11.82449421 11.72449421 11.62449421 11.62449422 11.52449422 11.92449422 11.92449422 12.22449422 11.82449422 12.12449422 11.82449422 11.92449423 11.9

SS Cygni Partial Light Curve(90 Day Interval)

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Every estimate is neededEvery estimate is needed Astronomers and Astronomers and

physicists can use physicists can use even noisy data to even noisy data to learn many things learn many things about how stars work.about how stars work.

With practice, AAVSO With practice, AAVSO visual observers can visual observers can estimate brightness estimate brightness to a to a precisionprecision near near 0.1 magnitude.0.1 magnitude.

Artist’s Conception - SS Cygni (AAVSO)

There is no perfect There is no perfect estimateestimate

Your observations Your observations are estimates are estimates because everyone because everyone gets a little different gets a little different result.result.

You don’t have to be You don’t have to be perfect--just do the perfect--just do the best job you can.best job you can.

Practice will help a Practice will help a lot!lot!

Want to try again?Want to try again?

Cat’s Eye Nebula (Hubble Space Telescope)

Let’s Do It!

More practiceMore practiceThis time, estimate the same variable but in frames B and C. These frames could be the variable star at different times in its light curve.Write your answers on the form.

How did it go?How did it go?

Was it easier the second and third time?

I bet you are ready for a real star.

Let’s try one!

W CygniW Cygni We are now going We are now going

to make two to make two estimates of a estimates of a semi- regular star semi- regular star called W Cygni (W called W Cygni (W Cyg). You should Cyg). You should have its chart in have its chart in front of you.front of you.

Click and it will be Click and it will be the next picture.the next picture.

Are you able to find it?(Click for a little help!)

You’re kidding!You’re kidding!

OK, there OK, there areare lots lots of stars in the of stars in the picture...picture...

You will need to You will need to learn to “star learn to “star hop” to the star hop” to the star you want. But it’s you want. But it’s easy.easy.

Here’s how!Here’s how!

W Cyg first estimationW Cyg first estimation

Take a look at the Take a look at the AAVSO W Cyg (size AAVSO W Cyg (size aa) chart.aa) chart.

Hold it so that it is Hold it so that it is tilted about 45 tilted about 45 degrees clockwise degrees clockwise (to the right). It (to the right). It will better match will better match the picture if tilted the picture if tilted a little.a little.

Why tilt the chart?Why tilt the chart?

The way a group The way a group of stars looks in a of stars looks in a telescope can telescope can vary because of vary because of the type of the type of telescope, how telescope, how you look into it, you look into it, and the season or and the season or time of night.time of night.

?

Why tilt the chart?Why tilt the chart?

Learning how to Learning how to match the match the telescope view to telescope view to the chart is the chart is something you’ll something you’ll learn when learn when actually observing.actually observing.

But, back to our But, back to our estimate!estimate!

Finding landmarksFinding landmarks Find the following things Find the following things

on your chart in this on your chart in this order:order:

1) M39 (star cluster)1) M39 (star cluster)

2) Comp star 53 and a line 2) Comp star 53 and a line of stars pointing from it to of stars pointing from it to the south the south

3) Rho (pronounced “row”) 3) Rho (pronounced “row”) Cyg, a Greek letter that Cyg, a Greek letter that looks like a “p”looks like a “p”

4) W Cyg4) W Cyg

M39

5.3 Comp star withline to the south

Rho Cyg

I’ll give you some help.

W Cyg

Finding landmarksFinding landmarks

This is how you star This is how you star hop--from the easiest hop--from the easiest thing to see to the thing to see to the variable star.variable star.

Now, let’s try it on the Now, let’s try it on the photo!photo!

We’ll go full screen We’ll go full screen and I’ll show you the and I’ll show you the landmarks we just landmarks we just found on our chart.found on our chart.

M39

53 comp with line of stars

Rho Cyg

W Cyg

Can you findthe landmarkson your own?

See if you canfind the compstars as well.

Did you find them?

Here are someof the compstars.

Can you findany more?

5559

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67

Now that you have found the comp stars, try toestimate W Cyg.

Write your estimate on the form.

We’ll keep a pointer on W in case you get lost.

How did you do?How did you do?

Were you able to Were you able to do it? do it?

If not, or if you If not, or if you had a lot of had a lot of trouble finding trouble finding things, ask the things, ask the helper before the helper before the next (and last) next (and last) estimate.estimate.

Here is a photo of W Cyg taken 82 days later.Try anotherestimate.

Write the result on your form.

If you need help finding it, click to the next slide.

Does that help?

Note that thephoto doesn’tlook like the one in April. This is because the sky changes appearance from season to season and even nightto night. This change is one of the challenges of variable star observing!

How did you do?How did you do?

Is it getting easier Is it getting easier to make the to make the estimates?estimates?

Did you have less Did you have less trouble finding W trouble finding W Cyg and the Cyg and the comparison stars?comparison stars?

Practice really Practice really helps, doesn’t it!helps, doesn’t it!

Is that your final Is that your final answer…?answer…?

On the right is a On the right is a section of the light section of the light curve of W Cyg curve of W Cyg from the AAVSO from the AAVSO data base.data base.

The two dates on The two dates on which you made which you made estimates are estimates are shown with dashed shown with dashed lines.lines.

April 28

July 19

Is that your final Is that your final answer…?answer…?

On April 28 the On April 28 the observations were observations were between about 6.3 between about 6.3 and 5.7 and 5.7 magnitude.magnitude.

On July 19, the On July 19, the observations were observations were between about 7.3 between about 7.3 and 6.4 and 6.4 magnitude.magnitude.

April 28

July 19

Is that your final Is that your final answer…?answer…?

How did you do How did you do compared to compared to other AAVSO other AAVSO observers?observers?

If one or more of If one or more of your estimates your estimates are outside of the are outside of the band of results, band of results, why?why?

April 28

July 19

If your results were If your results were different from AAVSO different from AAVSO

observers’...observers’...

Practice helps. Practice helps. Some AAVSO Some AAVSO observers have observers have made thousands of made thousands of measurements.measurements.

You were looking at You were looking at a computer, not the a computer, not the sky.sky.

You are still You are still learning!learning!

Variable star observing can be very

challenging sometimes!

You are teaching your You are teaching your eyes to see the world eyes to see the world

differently!differently!

Many new observers Many new observers need time before need time before they can see fine they can see fine differences in differences in brightness. This brightness. This takes practice but is takes practice but is a skill that can help a skill that can help you enjoy all the you enjoy all the beauty in the night beauty in the night sky.sky.

You are a winner!You are a winner!

The helper will plot The helper will plot your results today your results today along with along with everybody else’s.everybody else’s.

I bet you did pretty I bet you did pretty well!well!

While it’s not a While it’s not a contest, look at the contest, look at the curve and see how curve and see how you did.you did.

I learned how to measure the brightness of avariable star!

Be it Known thaton This Day...

So what did you learn?So what did you learn?

You learned how You learned how to find variable to find variable and comparison and comparison stars using stars using AAVSO charts and AAVSO charts and a technique called a technique called star hopping.star hopping.

So what did you learn?So what did you learn?

You then learned You then learned how to estimate how to estimate the brightness of the brightness of a star using a a star using a technique called technique called interpolation of interpolation of magnitude.magnitude.

So what did you learn?So what did you learn?

You learned that You learned that your data is valuable your data is valuable even as you are even as you are perfecting your perfecting your technique because technique because everybody gives everybody gives their best estimate their best estimate and astronomers and astronomers really use even really use even noisy data.noisy data.

Where do I go from here?Where do I go from here? Variable star Variable star

observing can be observing can be rewarding and fun!rewarding and fun!

Ask your helper for Ask your helper for more information.more information.

Included in the Included in the information package information package are some actual are some actual charts and projects charts and projects you can do starting you can do starting tonight!tonight!

Variable star observing is Variable star observing is fun!fun!

The changing night sky The changing night sky is something that can is something that can fascinate you for years fascinate you for years to come.to come.

You can expand into You can expand into new and exciting new and exciting measurement measurement technologies such as technologies such as CCD photometry or CCD photometry or analyze your data and analyze your data and other people’s just like other people’s just like scientists do!scientists do!

Comp stars around a new variable star(US Naval Observatory Photo)

Help Professional Help Professional AstronomersAstronomers

AAVSO members AAVSO members participate with NASA participate with NASA an other professional an other professional astronomers in their astronomers in their research.research.

One day, the Hubble One day, the Hubble Space Telescope may Space Telescope may even move to look at even move to look at a star because of your a star because of your observations!observations!

The AAVSO can help you The AAVSO can help you grow as a variable star grow as a variable star

observerobserver

AAVSO offers a AAVSO offers a number of free number of free services, including services, including charts, from its charts, from its web site--web site--www.AAVSO.orgwww.AAVSO.org

AAVSO AAVSO membership membership provides a number provides a number of other benefits:of other benefits:

Mentor ProgramMentor Program

Member benefits Member benefits include a mentor include a mentor program to team program to team you up with an you up with an experienced experienced variable star variable star observer in your observer in your area. You can area. You can learn a lot in just learn a lot in just one night!one night!

Publications, meetings, Publications, meetings, and more!and more!

AAVSO also offers a AAVSO also offers a newsletter, twice-newsletter, twice-yearly meetings, a yearly meetings, a Journal, an internet Journal, an internet discussion group, discussion group, special project groups, special project groups, and many more ways and many more ways to increase your to increase your enjoyment of enjoyment of astronomy.astronomy.

Ask you helper...Ask you helper...

Your helper can Your helper can answer all of your answer all of your questions about questions about the AAVSO and the AAVSO and variable star variable star observing. observing.

Please ask!Please ask!

Thank you for learning how Thank you for learning how to estimate brightness!to estimate brightness!

We hope variable stars bring you years of enjoyment!

Estimating star magnitude: First steps in Estimating star magnitude: First steps in

variable star astronomyvariable star astronomy

Adapted from Adapted from Hands-On Hands-On Astrophysics: Variable Astrophysics: Variable Stars in Science, Math, Stars in Science, Math, and Computer Education and Computer Education by Janet A. Mattei et al, by Janet A. Mattei et al, 19971997

PowerPoint Presentation PowerPoint Presentation developed by developed by

Chuck Pullen, AAVSO Chuck Pullen, AAVSO

Credits and Credits and AcknowledgementsAcknowledgements

Janet A. Mattei, Janet A. Mattei, Director, AAVSODirector, AAVSO

Kerriann Malatesta, Kerriann Malatesta, Technical Assistant Technical Assistant AAVSOAAVSO

Lew Cook, AAVSOLew Cook, AAVSO Lance Shaw, AAVSOLance Shaw, AAVSO Dan Kaiser, AAVSODan Kaiser, AAVSO Victor, Nancy, and Victor, Nancy, and

Kyle JewhurstKyle Jewhurst

Christine Miller, Christine Miller, California State California State University University SacramentoSacramento

And all those who And all those who helped test the helped test the early versions of early versions of this presentation!this presentation!