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Algol minima problems

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#1 almaach

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Posted 05 October 2015 - 02:50 PM

Hello,

 

I would like to observe the minima of Beta Persei (Algol), and I have looking for a ephemerides generator for it.

 

First, I looked the Sky & Telescope generator:

 

http://www.skyandtel...inima-of-algol/

 

and this is the result:

 

nq7e6a.jpg

 

And then, I have seen the ephemerides in the AASVO page:

 

https://www.aavso.or...l.top&oid=26202

 

30bhfed.jpg

 

The data are not the same. Do you know which are the correct ephemerides? Do you know another site to see the correct ephemerides?

 

 

Thank you.

 

BR

 

Oscar

 



#2 Rutilus

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Posted 05 October 2015 - 03:26 PM

The British Astronomical Association , Variable star section have a PDF  that you can download

from their website with the minima of Beta Per.



#3 beggarly

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Posted 05 October 2015 - 03:35 PM

There was a discussion on the Stellarium forum:http://sourceforge.n...hread/05aae684/

 

http://calgary.rasc....lgol_minima.htm



#4 almaach

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Posted 06 October 2015 - 02:03 AM

Thank you Rutilus and Beggarly for your answers.

 

Reading the RASC page, I understand that the best predictions are the S&T ones, but I'm a little confused, because I have seen now that the ephemerides published in S&T magazine are not the same that their web generator:

 

358dqwk.jpg

 

 

 

nq7e6a.jpg

 

Someone have a personal observation experience with these ephemerides?

 

Thank you and BR



#5 NJScope

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Posted 06 October 2015 - 07:23 PM

Almaach:

 

I suspect that some of the minor differences in time are due to whether JD (Julian Date) or HJD (Heliocentric Julian Date) was used in the calculation of these ephemerides.  Also, slight changes in the orbital period do occur with time so this could account for small variations in the predicted times.



#6 almaach

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Posted 07 October 2015 - 02:04 AM

Almaach:

 

I suspect that some of the minor differences in time are due to whether JD (Julian Date) or HJD (Heliocentric Julian Date) was used in the calculation of these ephemerides.  Also, slight changes in the orbital period do occur with time so this could account for small variations in the predicted times.

 

Thank you NJScope for your comment. After reading the RASC page (http://calgary.rasc....lgol_minima.htm) I think this as well. My doubt is if the data reporting for the Sky & Telescope webpage generator (UT) is correct, or the correct ones are published in the column magazine.

 

I'm afraid I will have to use the method of trial and error  :)

 

I have sent an e-mail to S&T asking about this issue, but I don't have received an answer yet.

 

Thank you all for your help.

 

BR

 

Oscar



#7 raptor()

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Posted 21 October 2015 - 03:53 PM

Oscar, did you ever get an answer from S&T for your question?  I too am trying to find the best online resource to find the Algol minima but get conflicting times depending on where I look.



#8 almaach

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Posted 29 October 2015 - 04:37 AM

Hello Raptor(),

 

Sorry for the delay. No, I don't have an answer from S&T to my e-mail.

 

BR

 

Oscar


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#9 goodricke1

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Posted 29 October 2015 - 07:07 AM

I observed the Algol minimum on October 16th and it chimed with the info on this page -

 

http://freestarchart...or-october-2015

 

I presume they will update the page for November.


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#10 raptor()

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Posted 05 November 2015 - 10:40 AM

Looks like they haven't updated the freestarchart site for November yet.  However, I did find this site. 

 

Last night was supposed to be minima for Algol but of course, it was cloudy.  Looks like no more nighttime opportunities in November.



#11 almaach

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Posted 06 November 2015 - 02:52 AM

Thank you Raptor(), a very interesting link.

 

BR

 

Oscar



#12 goodricke1

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Posted 06 November 2015 - 06:35 AM

Freestarcharts is updated now:

 

http://freestarchart...r-november-2015


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#13 nicedoggie

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Posted 16 November 2015 - 05:22 AM

Freestarcharts is updated now:

 

http://freestarchart...r-november-2015

Very good source. In the past I've used the S+T site, but it requires subscription, which is seen as an obstacle for some of my students. This is also handy for the star chart access. Thanks much, goodricke1.




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