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New to variables

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New to variables


I have been observing for a few years but mainly looking for galaxies, nebula etc. I've decided to have a go at variables, with last night being my first night.

I have a whole load of charts but wan to keep it simple to start and concentrate on some of the easier to spot stars. Last night I just stuck to S and T Ursae Majoris as they were fairly easy to find. I believe that they have periods in execss of 200 days, so assume will only need to estimate these every 2 weeks or so? I'm not sure how accurate my estimates are - is there anywhere to see what more experienced observers have estimated to tell how accurate I am? Obviously I'm just getting started so will be looking for more suitable stars to begin with on every clear night. Any advice would be welcome.


MDAV's picture
New to Variables

Hi Bish- Welcome aboard.

S and T UMa are currently at the bright end of the cycle. As a general rule stars like these are checked once a week . Try following them throughout their cycle. 

There are lots of tools here to help you. I would suggest you try the Visual Observing Manual at ""  and the 10-star tutorial at  ""

In addition there are two key tools to check your observation against others. Look on the right of the main page under the Star Finder. Enter your star name and then click on either the "Plot a Light Curve" or "Check Recent Observations". The caveat here is to be a bit cautious. One of the pitfalls for new observers is to see what they think they should be seeing. So while they can be used for your planning and as a quality check make sure they don't bias your estimates. Initially you may find yourself with a lot of outliers. Thats normal. You will improve with practice.

 Red stars like those you tried are particularly susceptible to subtle errors. Last week my estimate of S UMa appeared to be bright relative to other observers. I suspect either the Purkinje effect or the color difference between the variable and the Comp stars- or both - affected my estimate. The Purkinje effect is a natural tendency of the eye- the longer you look at red stats the brighter they appear.


Clear Skies and Dark,


lmk's picture
Starting out

Welcome to VSO'ing Jack. I think you will find it more rewarding than just hunting down faint fuzzies!

While many recommend Miras to begin with, I am not so sure they are the best. The main issues with them is (1) Red color causes estimation problems, due to Purkinje effect, instrumental effects (magnification, aperture), differences in color between the variable and "white" comp stars, for example. (2) Their regular, cyclical behavior invites bias (you get to expect it will be a certain brightness).

So, I recommend brighter CV, recurrent novae, nova-like, BLLAC/QSO to start out. They tend to be less predictable and even random, and they are generally of solar or "white" color. Some recommendations:

T Crb

RS Oph

HL Cma

TT Ari

SS Cyg

MRK 421

EX Hya

V426 Oph

Thank you both for your

Thank you both for your replies, some very helpful tips there. I hadn't taken into account the red star effect. I had got a little tired of going back to the same faint and fuzzies all the time, so it was either by a bigger scope (not an option) or take on a new challenge. It almost feels like starting a new hobby within a hobby. Look forward to the challenge and hopefully with your advice will be able to contribute something worth while with some practise.

I've checked my estimates against other peoples for 19th April. I made S Uma 8.3 and T 8.5. A bit on the faint side compared to the average, but probably not as far out as I thought I might be.



gianluca.paone's picture


i am a beginner to variabilies like you. I estimated on JD 2456401 S Uma to magnitude 8.0. I know the problems you have, are the same as I do. I suggest for your estimemate to apply the Argelander method, also I suggest you observer even R Leo, a star easy and it was my first variable. Welcome to the AAVSO!

PS. Excuse me for my bad English

Thanks for the advice. Good

Thanks for the advice. Good luck with your observing too!

pox's picture
Hi and welcome! If you are

Hi and welcome!

If you are going to observe bright red stars then it's not a bad idea to use as many comparison stars as you can when you make your estimate. What size of telescope do you have, since (say) S UMa at max is easier to estimate accurately with (again, say) a 6" telescope than with a 12".

Another idea, if you're not too confident, is to observe and estimate your stars but simply don't report them yet. Also, there are several bright non-red eruptive stars around at the moment (record the times accurately for these) among which are:

T CrB, YZ Cnc, U Gem, SS Aur, Z Cam, SU UMa, AG Dra, VX Cas, BO Cep

Though not bright all the time, YZ Cnc, U Gem, SS Aur and SU UMa are dwarf novae of which the maxima are bright enough for small telescopes. Z Cam is currently in one of its 'standstills' around magnitude 11-12. VX Cas and BO Cep are both newly-formed stars which are usually around magnitude 11 but can fade without warning to magnitude 13 on occasion.

Thanks for that. I am getting

Thanks for that. I am getting loads of useful information on here! I have a 10" scope, but used my 15x70 bins to make my first observations. The light pollution here is very bad, but I've not worked out the faintest star visible with my scope. I think I will make a number of observations  and check them against other peoples after I have made them.

KRS's picture
New to observing

Please contact me at .  Let's chat and see how I can be of help to you.  I have been a vser for over 50 years and might be able to help you.  I am also a member of the Mentoring Program.

Roger Kolman

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