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New Members: Welcome to the AAVSO

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Aaron Price
Aaron Price's picture
New Members: Welcome to the AAVSO

The AAVSO is over 100 years old. In that century we have expanded into lots of different areas and it can be daunting for a new person to find a home.

Please use this forum as a place to ask questions on any topic. Nothing is too simple. The questions can be about observing technique, variable star science, the web site or even about which AAVSO meetings are the best ones to attend. If you have a question, ask it.

Here are a few quick links to other resources that may help you as well:

Ask away!

LuisMartinez
LuisMartinez's picture
Newcomer

I am sitting at the SAS/AAVSO at Ontario, been working asteroid lightcurves since 2008, with CPC1100 and SBIG ST8XME. The discussion got me interested in variable star work as the next level. Do I need to have a filter set up? All my work has been with clear filters/V. What's a good primer? I have Brian Warner's book.

FJQ
FJQ's picture
Welcome to the AASVO

To:  Luis,

I was also at SAS/AASVO at Ontario!  I didn't see Brian, but I had dinner with his buddy, Bob Stephens; see: http://planetarysciences.org/warner.html (Thanks Bob for the Black Angus Dinner on Thurs!)

You can probably to mili-mag precission photometry with an ST8XME and a C-11.  Dr. Arne gave a talk the first day on the tools AASVO is providing to get your BVRI data transformed into a standard set of magnitudes; at the AASVO search key, enter "Transform" and your find the links to the downloadable software.

Here's another e-book from Bruce Gary on exoplanet photometry: http://brucegary.net/book_EOA/x.htm

Dr. Arne is going to anaylze our data of XZ Ceti when it comes up in the next 2-3 months; see: http://www.aavso.org/stellar-experiment-xz-cet  This would be the best time to submit and get critiques back from our director before he retires in the next 6-9 months.

Tons of resourses out there....just don't drown in them!

James Foster, Los Angeles, CA

My asteroid astrometry work: http://newton.dm.unipi.it/neodys2/index.php?pc=2.1.2&o=G72&ab=0

Last 2 seasons of variable stars: http://www.astroimage.info/images/AASVO-Jan12-Dec13-IMAGED-FIELDS2%2820Nov13%29.htm

LuisMartinez
LuisMartinez's picture
newcomer

Hi James,

Perhaps we can meet next year and hopefully by then I'll have a better idea to what I need to do to get started, I have, already drowned in my readings. I feel the same I felt in 2008 when I began asteroid lightcurves! Overwhelmed. my site www.lenomiyaobs.org 

 

luis

GFB
GFB's picture
variable star photometry...

Luis,

Welcome to the AAVSO!  I'm sorry I missed you at the SAS/AAVSO meeting, I see now you were there.  Looking at your web site, it seems you are already familiar with the detail of doing the photometry, now comes the challenge of deciding which aspect of variable star observing might be the most engaging for you, as there are many.  Some people enjoy observing long period variables, were a good observation once a week is a good strategy.  Others observe more rapid changing objects such as cepheid or catclysmic variable which are best monitored more closely. These types many be for familar to you as the time series photometry is similar to what you've done with asteriods.  Another favorite for many is the transitent object such as novae or supernovae.  Campaigns and interest is very high for these targets.  

 

Take some time to follow the forums and get a feel for the targets, it may help you decide where you want to jump in!

Bill

LuisMartinez
LuisMartinez's picture
thanks

thanks, Bill. I have been reading everything i get my hands on. It is overwhelming. How about a simple question: how many images does one generally take of the target. As you know for asteroids one can take hundreds through the night as the asteroid rises and sets. I know it is a question like how big is orange? but give me your best guess.

 

luis

GFB
GFB's picture
photometry cadence

Hi Luis,

Your experience for variables is good as most all the cataclysmic variables are studied at a fast cadence where the exposure time is determined by the brightness of the target and the desired signal to noise ratio.  30 and 60 second exposures are common and sometimes you might go shorter if the target is in outburst and you need to avoid saturation.   There are also occasions where fine detail like superhumping might be observed and exposures less than 30 seconds are used if the SNR can be maintained at a sufficient level.  Normally, these targets are observed for as long as possible at this cadence so you might end up with hundreds of images as a time series.

There are also targets that benefit from snap shot observing.  Here you would take one to three frames depending on SNR to make a single measurement of the target.  You might do several of these targets in an evening or even work them in before or after another time series.

To get a feel for the targets you might look at the Observing tab of the home page.  There you will find the Alerts and Special Notices item along with the Campaigns item.  These are a subscription service so you will be notified by email when targets are suggested for observing.  

 

You might also pick a well studied target such as SS Cyg and compare your results with other observers using the Light Curve Generator.  The LCG shows SS Cyg at minimum(~12.5) now and it's outburst should be due in a week or so.

Bill

 

clittlefield
I recommend cataclysmic variables

Hi Luis,

I like to observe cataclysmic variables with my CPC 1100 and ST-8XME. What's nice about CVs is that they often have short orbital periods (a few hours), so in one night, you can get a complete light curve. They can also show dramatic variability on a timescale of minutes. IP Peg and V1432 Aql are great first targets. Both systems are bright enough to be observed with an 11", and they undergo dramatic eclipses every few hours. (AAVSO has a nice page about IP Peg at http://www.aavso.org/vsots_ippeg .) I observed IP Peg for the first time in 2010, and I've been hooked on CVs ever since.

New CVs are discovered all the time, and it is especially rewarding to help characterize these CVs.

A final benefit of observing CVs is that it's OK to observe without a filter. You don't need to transform your data, which is very convenient.

I would be happy to provide more detailed advice about CVs if you're interested.

Best Regards,
Colin

LuisMartinez
LuisMartinez's picture
CVs

thanks for offering to help, Colin. I need a guiding hand to get started. my email: kd7gmk@gmail.com

 

LuisMartinez
LuisMartinez's picture
Approx. how many VS' are discovered in a year?

Mostly amateurs? Professionals?

Are there any automated surveys?

 

luis

lmk
lmk's picture
Surveys now rule

[quote=LuisMartinez]

Mostly amateurs? Professionals?

Are there any automated surveys?

[/quote]

Hi Luis, I cannot give you much hard numbers or names of surveys off hand, but these days, surveys find the majority of "new" variable stars, without a doubt. Amateurs probably find the same number as before, but they are just eclipsed in numbers by the methodical, and deep surveys!

In my 15 years of observing 18,000+ variables, I only really found one true new one, and it was by pure blind luck, I noticed a "new" star while star hopping to one of my regular program stars (HX Peg). At the time (2003), surveys had not really taken over yet, and this discovery raised some interesting initial possibilities (such as it being a fading Gamma ray burster!), but in the end it just turned out to be a half-day period RR Lyrae star.

Still, it was exciting! I haven't found any other new ones yet, but did catch some unexpected rare outbursting stars. ;)

If you made it a point to try searching for new variables, you may have some better luck, but the competition from automated surveys is going to be fierce!

Have fun!

Mike LMK

 

LuisMartinez
LuisMartinez's picture
Surveys now rule

Thanks for the reply Mike.

metham
Ferni relationship

I wonder if you can help me with this.

 

There is a database of cepheid variables called, The David Dunlap Observatory Database Of Galactic Classical Cepheids (DDOD)

http://www.astro.utoronto.ca/DDO/research/cepheids/cepheids.html#files

 

I have chosen a representative sample of cepheids.  I then looked these up in Stellarium, which as you know, is an awesome planetarium. I plotted the Stellarium Absolute Magnitude against the Stellarium Period of pulsation.  I attach the resulting graph.  My data points are the blue circles.

I was expecting to see data points form a pattern that corresponds with the Ferni relationship. But I cannot see any correlation at all.

 

I confirmed the validity of the Stellarium data as follows:

- Stellarium Apparent Mags data matches the data in the DDOD database.

- Stellarium Distance/parallax data matches the data in Simbad

- Stellarium Period  data matches the data in the DDOD database.

- To check Stellarium's Absolute Magnitude, I used the formula M = m + 5(log10(p)  and the results agreed with the data in Stellarium. (M=AbsoluteMag, m=ApparentMag, p=parallax)

 

Inline image 1

 

Incidentally, please note that the Stellarium Absolute Mags and distances do not match the DDOD data in any sense.

 

I would be grateful if you could explain why is there no correlation? Am I making false assumptions or doing something else wrong?

 

Here is the data.

 
STELLARIUM

STAR
Period
(d)
Abs Mag

FF Aql
4.4709
-3.08

Eta Aql
7.1767
-4.29

RY CMa
4.6783
-0.72

WW Car
4.6768
2.89

GZ Car
4.1590
0.92

l Car
35.5358
-4.75

SU Cas
1.9493
-2.08

V553 Cen
2.0605
-0.23

Del Cep
5.3663
-3.07

AD Cru
6.3979
4.67

BG Cru
3.3428
-2.71

DT Cyg
2.4992
-2.82

Beta Dor
9.8426
-3.70

Zeta Gem
10.1507
-4.13

V473 Lyr
1.4908
-2.01

S Mus
9.6600
-2.51

RT Mus
3.0861
-1.18

RS Ori
7.5669
-2.06

RS Pup
41.3876
-1.64

W Sgr
7.5950
-2.48

X Sgr
7.0128
-2.90

RY Sco
20.3132
3.26

SZ Tau
3.1487
-1.65

R TrA
3.3893
-3.46

Alp UMi
3.9696
-3.66

AP Vel
3.1278
-0.59

 

 

KristopherDennis
Help a Newbie

Hey all, I am new to this forum and new to observing variable stars. Right now I have a 90mm Meade Maksutov cassegrain. It that going be useable enough for this? I used to have an 11" Schmitt cassegrain, but had to sell it. I have a decent grasp on basics of telescopes, but as far as observing variable stars goes, I'm not really sure what the accepted minimum aperture should be if there is one. Anyone that could give me a good bit of newbie knowledge would be much appreciated.

CTX
CTX's picture
Newbie Help

Kristopher,

Congradulations, you have taken the fist steps to get you started towards making valuable scientific contributions through Variable Star Observing.  Yes, you can use your equipment!

There are several tools available to help you get started

One of the best to start with is the PP:  Introduction to AAVSO and How To Make a Visual Estimate

This can be found on the Online Resources For Beginning Observers page:

https://www.aavso.org/online-resources

Visual Manual for Observing Variable Stars (which can be found on the above page, also):

https://www.aavso.org/visual-observing-manual

The AAVSO 10 Star Tutorial:

https://www.aavso.org/10-star-training

and more specific, assuming you are in the NH:

https://www.aavso.org/sites/default/files/10startutorial-2013.pdf

Stars Easy To Observe List, although given your equipment you will probably want to limit yourself to stars with either a D or E scale Chart; D scale charts are 1 degree and E scale charts are ½ degree.  If you use the 26mm that probably came with your scope I would estimate your FOV at about .6 degree.

https://www.aavso.org/easy-stars

Lastly, the AAVSO Mentor Program would be a great place to get individual help... just remember that there is no such thing as a dumb question:

If you would like to "talk shop" with an experienced variable star observer, contact the AAVSO and we will put you in contact with the mentor program coordinator, Donn Starkey. Just send us an email (mentor@aavso.org) to let us know you are interested in this program.

 

KristopherDennis
Re: CTX

Thank you for giving me some links to check out! I did read through the ten star tutorial. Thanks for giving me a ballpark within which to work for the scales too. Yeah, I'm pretty limited right now, but hopefully I can learn this well before I get a bigger scope again. I will keep the mentor program in mind, I just may need it!

 

Thanks!

Kris

LKR
LKR's picture
All excellent advice!

Definitely go through these resources and please don't be shy about contacting Donn!

 

Welcome aboard!

 

KL

Roger Pieri
Aperture

Hello Kristopher,

Any aperture can be used for photometry, it's just a question of magnitude of the star. With 90 mm you can certainly target stars from mag 5 to about mag 12 using a DSLR. The issue with the Mak is its long focal lenght, its field of view is shorter than other optics ( F/D ~14  if I remember well ). You would have less choice of proper comparison stars, maybe also an issue of tracking ? But ok it should not be a stopper. The lenses of your DSLR are also certainly usable for bright stars, you could just attach it on the Mak (I did so in the past...).

To check that issue you can have a look at the AAVSO sequences charts, VSP:

https://www.aavso.org/apps/vsp/

Clear Skies !

Roger

KristopherDennis
Re: Robert

Thanks for the advice! I do have a Nikon DSLR, but no adapter yet. The mak does have a tracking motor. So after I pick up a t-adapter, is taking pictures part of recognizing magnitudes and reporting them? Also, thanks for the heads up on the limited field of view!

 

Update: I read through a few things and downloaded IRIS. Looks like I have some flat and dark frame work to do! It also seems that I need to learn the software, too. So, I guess what I am saying is that I get why DSLRs are used to measure magnitudes more accurately.

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