+- Skyhound Forums (https://skyhound.com/forums)
+-- Forum: Imaging & Astrophotography (https://skyhound.com/forums/forumdisplay.php?fid=24)
+--- Forum: Solar, Lunar and Planetary Imaging (https://skyhound.com/forums/forumdisplay.php?fid=33)
+--- Thread: Iapetus transit of Saturn in 2022 – 30th April 4:00am Australia (/showthread.php?tid=2509)
Iapetus transit of Saturn in 2022 – 30th April 4:00am Australia - Dennis - 2022-04-23
On the Australian Astronomy Forum “Ice In Space” a forum member has posted that Iapetus will transit Saturn for the first time in 15 years. The event will start at around 4am (EST) on April 30 and continue until dawn, as viewed from Australia. (UT 29-04-2022 1800)
However, when I look at this event in SkyTools 4, location Brisbane, the transit is shown in daylight at around 11:40am on April 30th (EST) (UT 30-04-2022 0140)?
Some replies to the post appear to confirm the 4:00am time using other planetarium programs?
Can anyone suggest a method of how I can verify the “truth”?
Thanks
Dennis
RE: Iapetus transit of Saturn in 2022 – 30th April 4:00am Australia - theskyhound - 2022-04-24
Hello Dennis,
Give me a day or so on this to look into how accurate SkyTools is plotting Iapetus.
I know that in the past SkyTools has always been rock solid on these things, and I would usually suggest an error, perhaps having to do with time zones. That said, Iapetus is one of the satellites that uses an older mathematical model, and it may be that it has lost accuracy in the last few years. I did test all of the satellites in ST4 against JPL horizons in ST4, but that was several years ago now. Maybe its time to check all of the ones that use the older methods.
Man, I really need to fix Saturn's rings too. I spent so much time on that, and had it working perfectly, and then one day they were suddenly broken. I suspect a change or bug in the (Windows) graphics library. I've been loathe to go back into that code because I might not come out for weeks!
RE: Iapetus transit of Saturn in 2022 – 30th April 4:00am Australia - Dennis - 2022-04-24
Thanks Greg, I appreciate your quick reply and attention, although sadly, the long range weather forecast for Brisbane for the event does not look promising.
Cheers
Dennis
RE: Iapetus transit of Saturn in 2022 – 30th April 4:00am Australia - PMSchu - 2022-04-24
Hi Greg,
Where does one go to find the latest position formulae for planetary satellites these days? I have the old 'Explanatory Supplement to the Astronomical Almanac' from ~1992, but that's sadly way out of date. I think they've stopped publishing The Astronomical Almanac in any case with all of the computer programs that are available now.
Phil S.
RE: Iapetus transit of Saturn in 2022 – 30th April 4:00am Australia - theskyhound - 2022-04-24
Phil,
JPL HORIZONS. It takes some work to get a transit prediction of that though.
RE: Iapetus transit of Saturn in 2022 – 30th April 4:00am Australia - PMSchu - 2022-04-25
Thanks Greg. HORIZONS isn't very easy to use IMHO.
Phil S.
RE: Iapetus transit of Saturn in 2022 – 30th April 4:00am Australia - theskyhound - 2022-04-25
Partial good news. I couldn't bear to look at Saturns rings while I was investigating the moon positions, so I fell deep into the rabbit hole... and finally fixed the rings!
I'll let you guys know tomorrow what I find out about the moons. Fixes coming soon.
RE: Iapetus transit of Saturn in 2022 – 30th April 4:00am Australia - Dennis - 2022-04-25
(2022-04-25, 03:41 AM)theskyhound Wrote: Partial good news. I couldn't bear to look at Saturns rings while I was investigating the moon positions, so I fell deep into the rabbit hole... and finally fixed the rings!
I'll let you guys know tomorrow what I find out about the moons. Fixes coming soon.
Thanks Greg, the sign of of true professional, your support is world class, not to mention SkyTools itself.
Please don't sweat this one, if the skies clear over Brisbane (almost no chance...
) I will still be able to have a peek at this event without your investigation being completed.Cheers
Dennis
RE: Iapetus transit of Saturn in 2022 – 30th April 4:00am Australia - theskyhound - 2022-04-25
Dennis,
My software has to be 100% reliable for these things. I will not accept anything else. I haven't taken the time to check the calculations for the main satellites of Saturn beyond eyeballing them in the telescope for maybe a decade, so its time to do a full review. Some of the moons use a polynomial algorithm to predict their position, and this was created twenty years ago. These things are created to fit past observations, but that doesn't mean they will be accurate into the future. Now, I don't know for sure yet that there is a problem with Iapetus, but it there is I'm going to fix it by adopting a different method.
RE: Iapetus transit of Saturn in 2022 – 30th April 4:00am Australia - Dennis - 2022-04-26
Thanks Greg, I do know that the position of Iapetus was correct in ST3 Pro on 29th April 2014, as I managed to grab a 30 sec exposure with my Canon 5D Mk III with a C9.25 and Tak x1.6 Extender.
Cheers
Dennis