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Tommohawk

Comet 289P/Blanpain Stellarium

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I updated Stellarium comets today just to be sure I have the latest on 2017 T2 Panstarrs… and now I have 289P/Blanpain showing as an improbably Mag -1.67 approx. South West.

I've deleted it and then updated again, and same thing. I spent a few minutes searching on the net... and then hit on the novel idea of looking in the sky. It was passably clear for a change, and nothing obvious.

My method is: F2 Configuration/PLugins tab/Solar Sys editor/configure button/Solar Sys tab/Import elements in MPC format/Select Comets/Select Bookmark: MPC list observable Comets/Get orbital elemsnts button/Select Mark all and Add objects button.

Anyone have ideas whats going on??

 

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Hi Tom my Stellarium v0.18.1 says mag'14.82.

Dave

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Just now, Davey-T said:

Hi Tom my Stellarium v0.18.1 says mag'14.82.

Dave

Hi Dave - funny I'm on v18.2 and cant see why its different. I did see a post on CN I think where someone else had it showing at an impossible Mag - that was on another software product thoughI think.

BTW I haven't forgotten I still owe you for that Varilock!

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3 minutes ago, Tommohawk said:

BTW I haven't forgotten I still owe you for that Varilock!

No worries mate, won't be going  to DSC until March at the earliest

Dave

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Well I've tried deleting the Config file and resetting defaults reimporting Comet data and I still have it as Mag -1.68.

Anyone else on v18.2?

 

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20 minutes ago, jam1e1 said:

skysafari has as -1.8mag!

Yeh I thought I saw that somewhere else online! Some dud data out there I guess. Not sure how come other Stellarium users aren't seeing it. I'm guessing the problem only arises if you update.

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I blame MPC. Here is a block from their current Comets file https://www.minorplanetcenter.net/iau/MPCORB/CometEls.txt

I've cut and pasted the line for Blanpain, where you can see it's been given an absolute magnitude of 2.5 

0289P         2019 12 20.9900  0.958886  0.685294    9.8466   68.9238    5.8975  20191223   2.5  4.0  289P/Blanpain

I guess the various planetarium packages apply their own visual estimates based on that.

 

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1 minute ago, Tommohawk said:

I found what looks like NOV data for 289P here, but couldn't make head or tail of it!

 

 

 

They usually publish what are called TLEs, two line ephemeris which can be entered into most mounts to track its orbit rather than keep entering new RA / Dec co-ords every time you want to find it.

I generally just do the latter for non permanent stuff like comets.

Dave

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1 minute ago, Davey-T said:

They usually publish what are called TLEs, two line ephemeris which can be entered into most mounts to track its orbit rather than keep entering new RA / Dec co-ords every time you want to find it.

I generally just do the latter for non permanent stuff like comets.

Dave

Thanks Dave, that usefull to know.

On a related note, does anyone know if Stellarium comet data needs updating monthly, or does it work on data such as TLEs?

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4 hours ago, Tommohawk said:

I found what looks like NOV data for 289P here, but couldn't make head or tail of it!

 

 

 

From the above link I got these ephemerides. Clearly showing a realistic magnitude 18 to 15  (the "m1" column). This is MPC data too but doesn't convey the same magnitude value as the general comet file I linked to earlier. 

Date    TT    R. A. (2000) Decl.     Delta      r    Elong.  Phase   m1    m2
2019 10 31    22 25 48.8 -24 26 11   0.3989  1.1982   111.5    50.4  18.8
...
2019 11 15    22 21 59.5 -21 41 05   0.3462  1.0883    97.2    64.4  18.1
...
2019 11 23    22 24 47.7 -19 15 01   0.3128  1.0401    90.8    71.7  17.6
...
2019 11 29    22 28 48.7 -16 52 44   0.2851  1.0101    86.5    77.1  17.3
2019 11 30    22 29 37.7 -16 25 45   0.2802  1.0058    85.9    78.0  17.3
2019 12 01    22 30 29.0 -15 57 42   0.2753  1.0015    85.2    78.9  17.2
...
2019 12 07    22 36 25.3 -12 43 55   0.2446  0.9801    81.7    84.0  16.9
...
2019 12 15    22 46 29.3 -06 51 54   0.2013  0.9628    78.0    90.2  16.4
...
2019 12 30    23 17 52.7 +14 42 50   0.1232  0.9678    79.2    93.7  15.3

I think that "TLE's" specifically relate to Earth orbiting bodies, i.e. satellites. 

Comet/minor body orbits are still generally distributed in MPC format and are just called Orbital Elements. For recently discovered comets the orbit might be unrefined and element sets can be rapidly outdated by further observation.  Asteroids can be perturbed in complex and chaotic ways (three body problem) but over quite long periods. Their elements don't need too much updating unless it's one of those crazy interloper rocks that come to light now and again. Some of the astro packages have re-written their orbital engine code in recent years to better handle these rare animals. SKySafari did.

I think many if not most packages can be set to update minor body and comet data on start-up.

The Planets orbits are stable over much, much longer periods. Their orbits are calculated for many years ahead based on a point in time at which the parameters were observed, the "epoch" and are usually "hard coded" in software packages.

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