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I decided to take the plunge and try out Occult4. This is mainly out of curiosity to see what OWC misses (Steve Conard says OWC captures most of it pretty well).

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When searching through "all" asteroids, I get a small list of events that does not match what I see on OWC. Keeping all of the same settings and the searching for only one asteroid ID shown as a predicted event on OWC, I am able to see that event for that particular listed in OWC (when it wasn't in the "all" asteroid search).

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I don't understand what I am doing wrong here. All settings are kept the same (at least by my direct user input) between the two searches besides searching "all" asteroids or for a particular asteroid ID.

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Here's an example screenshot of the "all" asteroid settings and list of generated events. Notably, the event for (164167) 2004 BE46

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But then if I select that specific asteroid (164176) and rerun the search then I do see the event listed in Occult4:

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The answer may be obvious to some of you experienced users, so I would appreciate any pointers. If the answer is not obvious as to why this is happening, I can post in the general IOTA chat and see if Dave Herald responds.

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Best,

Garrett

Occult4 likes to select "Use Horizon elements" when doing searches of single asteroids. Perhaps try unselecting/selecting that on one of your runs, and then see if that changes anything?

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I also find that when doing searches of "all asteroids", it is useful (time-saving!) to unselect "Use Horizon ephemeris" for a first pass, then to select "Save events as User .csv" from the List and Display page, before re-running through the now much smaller list of potential hits. Saves a lot of time by tossing out exceptionally unlikely events early on.

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-Teddy

Garrett:

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I see this "question" in several forms and usually the "solution" is that the asteroid was not in your Occult4 database to begin with. That is, even if you do a Search and you specify that you want to use JPL elements, your search will be based only on the asteroids that Occult4 currently has in its (MPC-based) database.

(164176) shows that it is a 4.2km rock. If when you "built" your Occult4 database you specified that you wanted all rocks that are, say, over 10km to be in the database, then any Occult4 search will not include a rock that is 4.2km in diameter(!!).

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See this past post of mine:

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See the image at the end of this post and see what you have listed for "Include minor planets larger than ______" What do you see here?

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George

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Thank you for the feedback, Teddy and George.

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Rebuilding to include 1+ km objects and following the order of conversion you suggested in the post seemed to work, George. I thought I had configured that to be 1 km but maybe it was set to 10 km. The part that still confuses me is that I was able to get a hit on the 4.2 km asteroid if I singled it out in the search before rebuilding the database. Shouldn't it have not been a part of my database if I built with only 10+ km objects? Anyways, that issue seems to be resolved now.

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I did as Teddy suggested and did the cheap scan and then refined the UserAsteroid list.

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However, the hits (~50) that I got still didn't seem to match what OWC produces and still didn't include that particular asteroid I mentioned before. Probably something else misconfigured by me.

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I'll keep playing around with Occult and will let y'all know if I have a solid question to ask.

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Best,

Garrett

Garrett:

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Your wrote:

"The part that still confuses me is that I was able to get a hit on the 4.2 km asteroid if I singled it out in the search before rebuilding the database. Shouldn't it have not been a part of my database if I built with only 10+ km objects?"

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There are a couple ways you can "bypass" Occult4's database (based on MPC elements):

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1) From the Search page you click on the blue box that says "Select asteroid or Set a comet".

When you do this, since this calls for a single (usually), or a small(er) set of asteroids, Occult4 obtains the elements used directly from JPL Horizons. This is done even if an asteroid you want is not in Occult4's MPC-based database. In this way you can obtain a prediction for (164176) even if it was not included in Occult4's database (as the rock would have been "under the specified size").

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2) You can also search for occultations for rocks that are not in Occult4's database by directly editing what is in the "USER file".

You do this by going to Occult4's Main Menu page and selecting "Edit the User file of minor planets". Click on "Add elements from JPL-Horizons". This allows you to enter in a single or multiple list of desired rocks (or comets!), and obtain elements directly from JPL Horizons. You then save the list (User file) you created and go to the Search page and tell Occult4 to run a search and "use USER file of elements".

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In both cases you essentially "bypass" what is in Occult4's database, and it runs a Search based on elements obtained directly from JPL.

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Yes, for a normal ("all asteroids") search, you first run a search which will be based on MPC elements. Then you tell Occult4 to get JPL-based elements for what you see in your initial "List & Display". The JPL-based elements then get stored in the "User file". Then you do a search for the rocks you have in that User file. This creates a revised List & Display, but the events are now based on the "more accurate" JPL elements.

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In "most" situations, the paths you get from an Occult4 search (based on JPL-Horizon elements) should match or be very similar to what you see on OW(C) --- since Occult4 is the SOURCE for "most" events published on OW(C) [Exceptions being if it was a "custom" prediction, such as made by Luck Star, etc.].

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George