What I want to do: Understand why a generated target list of minor planets between mag 14 and 16 using Database Power Search produced 53 results but only 5 are between RA 13h – 22h (basically the current summer sky). Seems an unlikely distribution. The “bright” MPC list was the source file and only filters were an observing date of July 10, 2025, mag 14 – 16, and main/outer belt asteroids. Other sources (CdC, C2A) reveal dozens of asteroids meeting those criteria and about the same density in Scorpius, Sagittarius, and Libra as Orion and Taurus. What am I missing? Thanks in advance.
I performed the DBPS on the main and outer belt MPs between 14 and 16 magnitude using the full MPCORB data file for 2025 Jul 10 and the search returned 902 objects. I also saved a subset of the search results from 13h to 22h with 472 objects. Both files are attached below.
I don't know why there were only 5 MPs between 13h and 22h in your search. I don't know what the magnitude cutoff is for the MPC's bright objects. That might have something to do with what you observed.
If you only use the Current bright minor planets download as a source for the minor planets in your database, these are biased. They are selected as the ones that are at opposition that month. This is because the main belt asteroids are at their brightest when they are opposite the sun (opposition). So each month this list makes a very good selection of minor planets to view, because they are at their brightest and higher in the sky at midnight. Because they are all near opposition to the sun, they are naturally in a range of RA in that direction. Right now, Sagittarius is too close to the sun to be highlighted for observation. But as each month passes you will get a set of minor planets in a different direction (RA range).
So lets talk about minor planets. There are far too many of them, so if we were to download all of them automatically, your charts and other functions would slow to a crawl. That, and they need to have their orbits refreshed every 6 months at the most (if you want accurate positions then it should refreshed every every 90 days or so). Given that most people aren't interested in all of those minor planets anyhow, it makes more sense to allow the people who are interested to download a subset of minor planets that meet their interests. For example, Phil downloads near earth asteroids. I tend to get the ones far out in the solar system.
So the first step in your search for minor planets is to download more of them to complete your database. After that, you will be able to use the search function more reliably. To download minor planets, select Minor Planets from the top level Data menu. Click the Download/Import button. There are a variety of ways to limit the number of minor planets that you download, so you should come up with a plan which meets your needs without downloading all of them. Keep in mind that selecting by limiting by magnitude is tricky because the magnitudes change with time.
Thanks, Phil, for the lists. They'll keep me busy for a few nights indeed.
Thanks, Greg. The "bright" list has enough MPs in my target mag range for my project -- but I did forget that it favors object at opposition and that would tilt the distribution.
So there are two "Bright Minor Planets," the one I curate every month, and the one you can download from the Minor Planet Center (top selection on the downloads dialog.) If you want a wider set of minor planets to work with, I suggest downloading the MPC list. I recommend to download it again every month or so to keep the orbits fresh.
2025-07-15, 05:19 PM (This post was last modified: 2025-07-15, 05:29 PM by PMSchu.)
Hi Greg,
The current epoch of osculation for the MPCORB data file is 2025 May 5 0000 UT, so it's already over 60 days old. Does the ASTORB data file offer the same option for 'Bright' MPs? I tend to stick with the MPCORB file because I use the MPC file for NEOs at Today's Epoch all the time.
PDC Skies,
Have you tried to observe any of the close approaching NEOs? The large NEO (35107) 1991 VH is currently 15.1 magnitude in Cepheus traveling at 4"/minute.
The current epoch of osculation for the MPCORB data file is 2025 May 5 0000 UT, so it's already over 60 days old. Does the ASTORB data file offer the same option for 'Bright' MPs? I tend to stick with the MPCORB file because I use the MPC file for NEOs at Today's Epoch all the time.
PDC Skies,
Have you tried to observe any of the close approaching NEOs? The large NEO (35107) 1991 VH is currently 15.1 magnitude in Cepheus traveling at 4"/minute.
Phil S.
The options are right there on the dialog
ASTORB is preferred for everything except NEOs, because the MPC only bothers to update the orbits for most regular asteroids every 6 months. After six months many of these plot so far from their actual position that its obvious in the eyepiece. Its a sad state of affairs.
ASTORB used to update the epoch daily, which was awesome, but the time between updates keeps getting longer. Its not nearly as bad as every six months though.
2025-07-23, 05:26 PM (This post was last modified: 2025-07-23, 05:27 PM by PDC Skies.)
(2025-07-15, 05:52 PM)theskyhound Wrote:
(2025-07-15, 05:19 PM)PMSchu Wrote: Hi Greg,
The current epoch of osculation for the MPCORB data file is 2025 May 5 0000 UT, so it's already over 60 days old. Does the ASTORB data file offer the same option for 'Bright' MPs? I tend to stick with the MPCORB file because I use the MPC file for NEOs at Today's Epoch all the time.
PDC Skies,
Have you tried to observe any of the close approaching NEOs? The large NEO (35107) 1991 VH is currently 15.1 magnitude in Cepheus traveling at 4"/minute.
Phil S.
The options are right there on the dialog
ASTORB is preferred for everything except NEOs, because the MPC only bothers to update the orbits for most regular asteroids every 6 months. After six months many of these plot so far from their actual position that its obvious in the eyepiece. Its a sad state of affairs.
ASTORB used to update the epoch daily, which was awesome, but the time between updates keeps getting longer. Its not nearly as bad as every six months though.
