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Aline occultations 5 Mar 8 PM EST
#1
Hi.

I heard about an occultation of a 10.4 mag star in Taurus by asteroid (266) Aline for my 'hood on Fri 5 Mar at 8:00 PM ish. Flying right over my backyard so I'm very tempted (weather gods permitting).

Found some odd stuff.

Asteroid not near target star TYC 00678-0196 1. No change after updating Current data. 

Star looked a little dim in Interactive Atlas chart compared to other mag 10-ish stars.

Hovering over star: no magnitude shows in Status Bar.

Obj Info box shows mag 99.9. Really?!

Asteroid data OK? Bad data on the star?

Update: Still bad star data in ST4VI. But the asteroid path is correct!


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cheers,
Blake

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#2
Hi Blake,

Lots to unpack here:

1. There are over 500 million stars in the database. Errors are inevitable. In this case, there seems to have been a unique issue in selecting the correct V magnitude for this star (from the variety of sources used). Internally a place holder value of 99.9 is used to denote "unknown magnitude." The dialog failed to mark it as such, because by definition there aren't supposed to be any Tycho 2 stars with unknown magnitudes. I am making a note to root these out (if there are indeed more) when I redo the database in the future using Gaia data.

2. Doing anything more than just looking at the few bright asteroids that are included in the Current Minor Planets list each month requires some extra effort, and some knowledge of minor planets, their orbits, and how to download these in SkyTools. Minor planet orbits are only accurate for a period of time, so they must be updated with the current orbital elements to be accurate at all. For something like an occultation, the orbital elements are often updated based on new observations in the days and weeks ahead of the event. This is how essential accuracy is for these events. It is basically a specialty field.

The current minor planet database includes minor planets that are near opposition and brighter than 12.5 magnitude only. So updating that alone would not update this particular asteroid, which is magnitude 13.5. To see the elements for this asteroid and determine how recent they are, look it up in your minor planet database. To obtain recent elements, you will need to download elements manually from the MPC. Please note, however, that the MPC is struggling right now to keep their elements up to date. This is something that is deeply concerning, but there is little that I can do about it.

3. You are asking about SkyTools 3. As you know, SkyTools 4 Visual was released almost a year ago and I put a great deal of effort into updating how the minor planets work. Support for SkyTools 3 is planned to end on March 31, so I can focus on SkyTools 4. I am limited in what I can do with SkyTools 3 anyhow, and many issues people discover have already been addressed by creating SkyTools 4.

I am moving this thread to the discussion section to make it more visible to others.
Clear skies,
Greg
Head Dude at Skyhound
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#3
Thanks for all the info.

There's lots of good news in all this.

The star is in the right location.

SkyTools 4 Visual is showing a good path.

I have a good field of view prediction for my telescopes.

I've got a predicted time for my location, so I'm happy.

I am trying to ween off ST3P... It's not easy.

Blake
cheers,
Blake

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#4
Awesome
Clear skies,
Greg
Head Dude at Skyhound
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