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AstroClock

David Benn
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Joined: 2010-07-29

Hi John

I just grabbed your AstroClock app from the iTunes App Store. First, thanks! This is awesome. Second, I'm jealous; I was planning to write this kind of app as a first foray into iPhone development before moving onto a light curve viewer. ;)

Regards,

David

JD calculation code
David Benn
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Joined: 2010-07-29

John, I meant to ask: what JD calculation method do you use? VStar uses Jean Meeus's:

http://vstar.svn.sourceforge.net/viewvc/vstar/trunk/src/org/aavso/tools/...

I wrote a number of unit tests after finding problems with other JD calc algorithms:

http://vstar.svn.sourceforge.net/viewvc/vstar/trunk/test/org/aavso/tools...

Regards,

David

JD calculation code - gulp!
RJB
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Joined: 2010-09-09

You just had me nervously rechecking the current JD! I used Peter Duffett-Smith, Practical Astronomy with Your calculator, 2nd ed. I checked (and rechecked) the calculation against AAVSO's own JD calculator http://www.aavso.org/jd-calculator, other online JD coverters, as well as a couple of other JD apps that are available. If there are problems with the Duffett-Smith algorithm for *past* dates, I'm less concerned since the app only shows the current time. (Is Duffett-Smith accurate for negative years? - Don't care). But if there are *future* date problems, say within the next 20 years, please let me know!! Wait - make that 5 years. :-)

Thanks
RJB
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Joined: 2010-09-09

David -

Thanks for the kind note. We're really proud of the simplicity of the AstroClock interface. Like idiots we tackled Variable Stars (which is really pretty complex) as our first app - it took months - but when we then sat down to do AstroClock, I think we completed everything in ~ 1 week. FYI, we're already thinking about extensions: I've created a poll for suggested enhancements here: http://www.diatomsoftware.com/?q=astroclock_poll.

I'd really welcome suggestions from this group about desired enhancements that would make these apps more useful to a broad audience.

Didn't mean to alarm you
David Benn
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Joined: 2010-07-29

Hi John

I didn't mean to be alarmist. I just know that I've seen problems in some JD routines, e.g. from an old (mid 80s) magazine article that gave incorrect results in software I have used recently for particular corner cases, especially around the end/start of the year. Some of the unit test cases in that code I pointed to cover those cases. I hear what you are saying about time into the future and past and agree with the sentiment. :)

Regards,

David

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