Sun, 07/07/2024 - 18:54
Hi all,
I was wondering if the SPP ephemeris (https://www.aavso.org/aavso-spp-program) and CV ephemeris were available anywhere via a web service or perhaps available in a parsable format.
Assuming I can also start with one of the published times and use the period to meet my needs, but thought I'd also check on the API in case there is more nuance I'm not aware of
I assume you are trying to predict the times when maxima will occur. There isn't a totally easy way to do that from the files. At one time there were a number of website that did the predictions, but those are all gone as far as I know. The only place you might want to start is https://www.aavso.org/times-minimum-databases . Otherwise, you might need to write your own.
Eric
VSX has ephemeris for stars that you find with the search tab.
I throw that into a spreadsheet and add a half-period to make my own ephemeris that has eclipses and secondary eclipses.
Ray
Thanks, Eric and Ray!!!
To provide a little more context, I’ve been writing an Android app (for fun and for helping my AAVSO planning). I’m essentially duplicating some of the AAVSO target tool functionality, but also adding a little more specificity in getting candidates for a particular time of night (or early morning). Essentially combining the data on rise and set times (logic I already have) with the time of minimum and maximum (depending upon target) to give myself easy-to-access recommendations (e.g. I’m going to be up at 3:00 AM local time, what should I shoot).
Ray, I didn’t see the ephemeris link in the VSX results before, so that is a great help, and actually gives me a different path I might follow. Ideally, I’d like to generate that table myself (as opposed to trying to parse the HTML programmatically, which would be vulnerable to how that page changes over time).
Today, I pull most of the data for a target through Vizier (e.g. catalog=["B/vsx/vsx"]]). This allows me to programmatically get the OID, ra, dec, and period, among other things. What it appears I’m missing is a starting time of min/max, which shows up on the AAVSO VSX page as Epoch.
I currently don’t see how to retrieve this value, but if I could, then I think I’d have my solution.
Any thoughts?
Thanks again for the responses and help!
I believe that the Rolling Hills Observatory ephemeris calculator is also still online.
https://www.rollinghillsobs.org/perl/calcRRephem.pl
Once a target is chosen you could check VSTAR since JD 2430000 or so ( when CCDs became commonplace ) and do a phase plot. Pick a min or max and call it your start point or epoch. Better yet for the benefit of researchers that might like to see the entire light curve, observe it often and all the time. One or two seasons will generally make a light curve magically appear. Very satisfying too. ; ) Average many images so that a clean curve emerges rather than reporting a 1000 data points for an hour run.
Ray
First, thanks Horace (SHA) for pointing me to Rolling Hills Observatory. This is exactly the application I've built (currently to run on my Android phone). The missing piece was really how to get the epoch, from which to derive the time of minimum (or time of maximum, depending upon the target) using the period.
After playing around with vsx more, I found out that I can make an HTTP request to: https://www.aavso.org/vsx/index.php?view=api.object&ident={displayName}&format=json, and retrieve the star properties (including epoch and period which I need to calculate the ephemeris). Currently working up a script to pull this data to include in my application.
Appreciate the help all!