Real Light Curves

The light curves published on web pages are usually very carefully selected

because they look impressive.

In reality, not all light curves look so good. Here are some of mine ...

TW Dra has a

range of over 2 mags

… but in 2009, I never

managed to catch it in eclipse

TW Dra in 2009

6.7

7

7.3

7.6

7.9

8.2

8.5

8.8

9.1

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Phase

Mag

nit

ud

e

Sometimes you miss seeing the primary eclipse,

… but do catch the secondary

eclipse

Here,, the maximum near phase 0.1 and the

eclipses near phases 0.35 & 0.8

can be seen,

but the maximum near phase

0.6 was almost

missed !

W UMa in 2009

7.9

8

8.1

8.2

8.3

8.4

8.5

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Phase

Ma

gn

itu

de

Sometimes you can’t see mid eclipse

because the EB

becomes too faint for you to see.

At mid eclipse,

RW Tau is around mag

11.0

The start of this eclipse of TV Cas (7.3-8.1) started in daylight.

Cloud then intervened before the

eclipse was over

TV Cas : 2010 Feb 5

7.7

7.75

7.8

7.85

7.9

7.95

8

8.05

8.1

18:00 19:12 20:24 21:36

Mag

nit

ud

e

If you observe low amplitude

EBs, scatter will be a problem.

However, the general pattern of

variation can still be seen

GK Cep in 2009

7.10

7.15

7.20

7.25

7.30

7.35

7.40

7.45

7.50

7.55

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Phase

Ma

gn

itu

de

When you first start

observing, you expect

that eclipses will be

symmetrical.

Not all are, as is shown by this RZ Cas light

curve

Whenever possible, its best to observe

the whole eclipse in one night.

Otherwise different

sky conditions or changes in the light

curve shape will

lead to scatter

Beta Lyrae, however,

has eclipses that last

more than a day

… so you have to

observe on many

different nights

LY Aur has a period very close to 4

days.

This means that you keep catching it at

the same phases for

months on end.

In 2009, this wasn’t too bad

because eclipses were occurring at

night.

LY Aur in 2009

6.9

7

7.1

7.2

7.3

7.4

7.5

7.6

7.7

7.8

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Phase

Mag

nit

ud

e

In 2007, however, eclipses

were occurring

during daylight.

Hence the light curve

was less impressive

LY Aur in 2007

6.8

6.9

7

7.1

7.2

7.3

7.4

7.5

7.6

7.7

7.8

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

Phase

Mag

nit

ud

e

The lesson is to not be put off if your some of your light curves are

disappointing

It happens to everyone – but every so often, you will have more luck

The secondary eclipse of RZ Cas is

usually said to be too

small to be seen

visually.

But it does show up

near phase 0.5 in this light curve from 2009

RZ Cas in 2009 (SAC elements)

6.0

6.2

6.4

6.6

6.8

7.0

7.2

7.4

7.6

7.8

8.0

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Phase

Mag

nit

ud

e