20 April 2019 at 11:21 pm #574316
When trying to select stars to measure for my Eclipsing Binary Star project I could not find a calculator that could predict transits. It is possible to search through stars individually for predicted eclipses in the AAVSO VSX database. However this searches queries cannot take into account eclipse timing and visibility from the observers location.
To fill this gap I have create a website https://eclipsingstars.org/ that based on the information in the GCVS predicting transits of variable stars.
It is a simple application based on your latitude and longitude will predict which eclipses are visible that night. Eclipses can limited by their star altitude, time of the eclipse, and the star magnitude.
There are a few things to note:
- Only the information in the GCVS catalog is used. There may be further information about epoch, period change, eclipse length; however this isn’t in the catalog so will not be used by the site.
- Where the eclipse time is given start and end times of the eclipse are used to calculate visibility, otherwise it is only the mid eclipse time that is used.
- All times are local to the observer and are in 24 hour clock.
- Latitude and Longitude are in decimal degrees (the site is only a guide so rounding to 0.5 degree should be fine for most users).
My first language is Java, my second is C++, and a distant 3 is English so if anyone want to writing a user guide is more than welcome, and I will create a page for it on the site.
Any bugs or feature requests please post here.
It has already been suggested that it might used for other variable stars types, but I don’t have knowledge in variable stars to know which.21 April 2019 at 7:38 am #580992Paul LeylandParticipant
A quick kick of the tyres left me impressed but there is something I spotted. Is the longitude positive going east or west? For instance, La Palma is roughly 17W. Is that longitude 17 or 343?21 April 2019 at 8:01 am #580993
Applications are available for this, I wrote one myself a few years ago. I would be careful using the GCVS data as I found it was not very accurate. I used the Krakow University’s list as it is more up to date.
James21 April 2019 at 9:00 am #580994
Yes sorry should have said that Longitude is positive going East so La Palma will be 343. I was thinking of implementing -17 or 17W, but at a minimum I’ll add a note to the site.21 April 2019 at 9:19 am #580996
Do you have any links to those other applications it would be good to compare and contrast?
Looking at the Krakow University’s site there appears to be to files:
They both look like they contain the same data. The EPHEM.TXT looks easier to read. There isn’t a field for the percentage of the period the eclipse takes part for. It might be nice merge this with the GCVS, but that does raise questions of how to show where data originated from.21 April 2019 at 9:20 am #580997Andy WilsonKeymaster
That is a good looking, easy to use website. It is the kind of thing that should be very useful.
James, do you have any links to the other applications? Then we could add them to the VSS links.
Andy22 April 2019 at 8:55 am #580999
I didn’t put them on the web, I wrote an feature in VSS circular about it and some other apps I had written. If you want a copy I can email it to you.
James23 April 2019 at 10:08 pm #581001
I have merged Krakow University’s catalog (TIDAK?) with GCVS. The website uses the TIDAK epoch and period where possible to calculate the eclipse timings. All bar about 10 stars in the TIDAK catalog are matched to GCVS, however there are almost twice as many eclipsing binaries in the GCVS than in TIDAK. I have also included GCVS stars with a non-eclipsing type that are listed in TIDAK. There has been some additional data sanitisation to remove stars with incomplete data. Hopefully this shouldn’t affect most observers, but please comment here if you are.
I thought it might be useful to add the spectral types, and links to the catalogs where the data was obtained. I would have liked to added links to VSX as well, but there is no easy way to build the link from the star name. An obvious omission is a link to SIMBAD, which I will put in a future release.
Briefly scanning the GCVS data file the other variables that look as if they fit this format are Pulsating Variable Stars, although given the long periods knowing the time of the maxima or minima might not be as much use.27 April 2019 at 6:16 pm #581014Mark RadiceParticipant
Eliot, thank you for this programme. I have saved it as a bookmark and look forward to using it. Is there a way to sort by change in magnitude? I am using my binoculars while the days are so long and find spotting a change of a few tenths of mag somewhat of a challenge. Knowing which will be easiest to spot would be most useful.
Thanks once again!
Marl28 April 2019 at 10:23 pm #581015
I’ve updated the website with a sort by magnitude difference option. It calculate the difference in magnitude between the faintest and brightest, and then re-orders the list with the greatest difference in magnitude first.
The sort was fairly trivial; however I noticed that the GCVS magnitude data was more complex than I originally thought (I should have learnt this by now). I’ve updated my catalog of eclipsing stars accordingly.
A few things to note:
- GVCS uses Min1 and Min2 magnitudes this site just uses the faintest of these.
- If the Minimum or Maximum magnitude GCVS is not in V or is missing then the star is omitted.
- GVCS list magnitudes with a “<” or “>” indicating the limiting magnitudes I treat both these cases as the faintest magnitude.
- GVCS also lists magnitudes in brackets i.e. “()” here I add this value to the maximum value to get the sites faintest value.
The intent of this site is to provide observers with just enough information to quickly decide which stars might be of interested that night. As such compromises have to be made to simplify the catalog data available. The links to the source catalog(s) can be used to get more detailed information.29 April 2019 at 7:40 am #581016
This should give access to my apps.
James29 April 2019 at 11:48 am #581017Andy WilsonKeymaster
Thanks for the link James.
Andy1 May 2019 at 9:20 pm #581022Mark RadiceParticipant
Thanks, Eliot. I’m looking forward to watching a star in real time – once the clouds clear anyway! Fascinating stuff.
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