Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

Normal uncertainty in asteroid positions?

  • Please log in to reply
13 replies to this topic

#1 nforrester

nforrester

    Sputnik

  • -----
  • topic starter
  • Posts: 33
  • Joined: 07 Sep 2021

Posted 27 January 2022 - 06:05 AM

So I took these two pictures tonight, about an hour apart, using a C8 at f/6.3. Based on the Stellarium mobile app I expected to find the asteroid 7 Iris in the middle of the frame. I did not find it there. However, I found a moving point of light near the top of the frame with approximately the right velocity (estimated visually, I haven't done any math yet). It's about 20+/-5 arcminutes from the expected position. Could that be it? What's the typical uncertainty in asteroid orbits? What's the preferred tool for identifying moving dots like this?

 

7 iris maybe
 
The images are about 1° wide by 40' tall, and are centered at approximately 07h 25m 30s / 15° 38' 00".

Edited by nforrester, 27 January 2022 - 06:08 AM.


#2 happylimpet

happylimpet

    Fly Me to the Moon

  • *****
  • Posts: 6,427
  • Joined: 29 Sep 2013
  • Loc: Southampton, UK

Posted 27 January 2022 - 06:33 AM

For a major asteroid like this, the uncertainty would be much less than an arcsecond. Have you confused epochs for coordinates (ie 2000,2050,epoch of date etc)?


  • S.Boerner likes this

#3 nforrester

nforrester

    Sputnik

  • -----
  • topic starter
  • Posts: 33
  • Joined: 07 Sep 2021

Posted 27 January 2022 - 06:45 AM

Given that I haven't done any math, I find it improbable that I did the math incorrectly grin.gif. My expected position and velocity are based purely on comparing the star fields in my pictures with those in the Stellarium mobile app. I can't vouch for the correctness of the app of course.



#4 Tapio

Tapio

    Fly Me to the Moon

  • -----
  • Posts: 6,081
  • Joined: 24 Sep 2006
  • Loc: Tampere, Finland

Posted 27 January 2022 - 07:54 AM

I don't use Stellarium mobile app but does it have real time ephemerides for asteroids or do you have to manually update them ?

 

I just use CdC where update is needed and in my images asteroids and comets are dead center.



#5 nforrester

nforrester

    Sputnik

  • -----
  • topic starter
  • Posts: 33
  • Joined: 07 Sep 2021

Posted 27 January 2022 - 08:06 AM

No manual update should be necessary - it claims to download ephemerides as needed. The most probable cause seems to be a bug in the app.

 

I'll check out CdC, thanks for the tip. This is what you mean, right? https://www.ap-i.net/skychart/en/start



#6 Tapio

Tapio

    Fly Me to the Moon

  • -----
  • Posts: 6,081
  • Joined: 24 Sep 2006
  • Loc: Tampere, Finland

Posted 27 January 2022 - 08:17 AM

No manual update should be necessary - it claims to download ephemerides as needed. The most probable cause seems to be a bug in the app.

 

I'll check out CdC, thanks for the tip. This is what you mean, right? https://www.ap-i.net/skychart/en/start

Yes.



#7 happylimpet

happylimpet

    Fly Me to the Moon

  • *****
  • Posts: 6,427
  • Joined: 29 Sep 2013
  • Loc: Southampton, UK

Posted 27 January 2022 - 08:37 AM

Yeah, CdC is the berries.



#8 StupendousMan

StupendousMan

    Mariner 2

  • -----
  • Posts: 247
  • Joined: 21 Aug 2005

Posted 27 January 2022 - 10:05 AM

The JPL Horizons ephemeris system, at

 

     https://ssd.jpl.nasa...zons/app.html#/

 

will allow you to make tables of the position of any body in the Solar System.  The results are accurate.  For 7 Iris, it lists the following positions for the period between UT Jan 26 and UT Jan 28:

 

 

**********************************************************************************************************
Date__(UT)__HR:MN     R.A._____(ICRF)_____DEC  dRA*cosD d(DEC)/dt  Azi____(a-app)___Elev    APmag   S-brt
**********************************************************************************************************

2022-Jan-26 00:00     07 23 57.35 +15 44 25.4  -34.1691  1.682815   96.193492  29.756126    8.095   4.718
2022-Jan-26 01:00     07 23 54.97 +15 44 26.9  -34.4510  1.628477  108.136490  40.491625    8.097   4.719
2022-Jan-26 02:00     07 23 52.58 +15 44 28.5  -34.6662  1.553754  123.302483  50.398018    8.098   4.720
2022-Jan-26 03:00     07 23 50.17 +15 44 29.9  -34.7975  1.464021  144.266361  58.370788    8.100   4.721
2022-Jan-26 04:00     07 23 47.76 +15 44 31.2  -34.8335  1.365684  172.699142  62.459854    8.101   4.722
2022-Jan-26 05:00     07 23 45.35 +15 44 32.5  -34.7692  1.265732  203.352206  60.898172    8.103   4.723
2022-Jan-26 06:00     07 23 42.94 +15 44 33.6  -34.6064  1.171266  227.848897  54.444867    8.104   4.724
2022-Jan-26 07:00  m  07 23 40.56 +15 44 34.7  -34.3539  1.089004  245.351156  45.252598    8.106   4.725
2022-Jan-26 08:00  m  07 23 38.19 +15 44 35.7  -34.0266  1.024826  258.530387  34.808173    8.107   4.726
2022-Jan-26 09:00  m  07 23 35.84 +15 44 36.6  -33.6442  0.983366  269.487747  23.888674    8.109   4.728
2022-Jan-26 10:00  m  07 23 33.53 +15 44 37.5  -33.2306  0.967696  279.511034  12.943419    8.110   4.729
2022-Jan-26 11:00 Am  07 23 31.24 +15 44 38.4  -32.8116  0.979119  289.453078   2.311421    8.112   4.730
2022-Jan-26 12:00 Nm  07 23 28.98 +15 44 39.3  -32.4134  1.017075  299.979187  -7.666814    8.113   4.731
2022-Jan-26 13:00 *m  07 23 26.75 +15 44 40.3  -32.0606  1.079187  311.674439 -16.578045    8.115   4.732
2022-Jan-26 14:00 *m  07 23 24.54 +15 44 41.4  -31.7750  1.161420  325.018289 -23.889545    8.116   4.733
2022-Jan-26 15:00 *m  07 23 22.34 +15 44 42.5  -31.5734  1.258362  340.188754 -28.957773    8.118   4.734
2022-Jan-26 16:00 *m  07 23 20.16 +15 44 43.7  -31.4672  1.363592  356.746916 -31.161983    8.119   4.735
2022-Jan-26 17:00 *   07 23 17.98 +15 44 45.1  -31.4609  1.470124   13.564144 -30.170459    8.121   4.736
2022-Jan-26 18:00 *   07 23 15.80 +15 44 46.6  -31.5524  1.570885   29.361170 -26.137748    8.122   4.737
2022-Jan-26 19:00 *   07 23 13.61 +15 44 48.1  -31.7327  1.659199   43.411887 -19.608094    8.123   4.738
2022-Jan-26 20:00 *   07 23 11.40 +15 44 49.7  -31.9869  1.729245   55.693254 -11.240927    8.125   4.739
2022-Jan-26 21:00 *   07 23 09.18 +15 44 51.4  -32.2949  1.776456   66.602206  -1.617680    8.126   4.740
2022-Jan-26 22:00 *   07 23 06.93 +15 44 53.1  -32.6329  1.797831   76.694568   8.806281    8.128   4.741
2022-Jan-26 23:00 N   07 23 04.66 +15 44 54.9  -32.9751  1.792142   86.598803  19.669775    8.129   4.742

2022-Jan-27 00:00     07 23 02.36 +15 44 56.6  -33.2954  1.760017   97.074815  30.643444    8.131   4.743
2022-Jan-27 01:00     07 23 00.04 +15 44 58.2  -33.5693  1.703895  109.203355  41.338385    8.132   4.744
2022-Jan-27 02:00     07 22 57.71 +15 44 59.8  -33.7753  1.627863  124.730338  51.140281    8.134   4.745
2022-Jan-27 03:00     07 22 55.37 +15 45 01.4  -33.8966  1.537371  146.283099  58.884206    8.135   4.746
2022-Jan-27 04:00     07 22 53.02 +15 45 02.8  -33.9225  1.438859  175.220891  62.562317    8.137   4.747
2022-Jan-27 05:00     07 22 50.67 +15 45 04.1  -33.8484  1.339315  205.625374  60.539493    8.138   4.748
2022-Jan-27 06:00     07 22 48.33 +15 45 05.3  -33.6768  1.245793  229.495308  53.787002    8.140   4.749
2022-Jan-27 07:00     07 22 46.01 +15 45 06.4  -33.4169  1.164933  246.547769  44.450243    8.141   4.750
2022-Jan-27 08:00  m  07 22 43.70 +15 45 07.5  -33.0840  1.102501  259.482499  33.944880    8.143   4.751
2022-Jan-27 09:00  m  07 22 41.42 +15 45 08.5  -32.6981  1.062995  270.324067  23.009194    8.144   4.752
2022-Jan-27 10:00  m  07 22 39.17 +15 45 09.5  -32.2832  1.049338  280.312169  12.077487    8.146   4.753
2022-Jan-27 11:00 Am  07 22 36.95 +15 45 10.5  -31.8650  1.062678  290.277405   1.485497    8.147   4.754
2022-Jan-27 12:00 Nm  07 22 34.76 +15 45 11.5  -31.4696  1.102309  300.876162  -8.422789    8.149   4.755
2022-Jan-27 13:00 *m  07 22 32.59 +15 45 12.6  -31.1212  1.165722  312.687734 -17.225902    8.150   4.756
2022-Jan-27 14:00 *m  07 22 30.44 +15 45 13.7  -30.8412  1.248779  326.176794 -24.380815    8.152   4.757
2022-Jan-27 15:00 *m  07 22 28.31 +15 45 14.9  -30.6461  1.345994  341.483255 -29.238943    8.153   4.758
2022-Jan-27 16:00 *m  07 22 26.20 +15 45 16.3  -30.5463  1.450914  358.108449 -31.192204    8.155   4.759
2022-Jan-27 17:00 *m  07 22 24.08 +15 45 17.7  -30.5461  1.556559   14.884482 -29.943921    8.156   4.759
2022-Jan-27 18:00 *   07 22 21.96 +15 45 19.3  -30.6427  1.655900   30.555519 -25.687605    8.158   4.760
2022-Jan-27 19:00 *   07 22 19.83 +15 45 20.9  -30.8267  1.742346   44.455533 -18.986927    8.159   4.761
2022-Jan-27 20:00 *   07 22 17.69 +15 45 22.6  -31.0828  1.810187   56.607597 -10.499842    8.160   4.762
2022-Jan-27 21:00 *   07 22 15.52 +15 45 24.4  -31.3906  1.854993   67.428587  -0.797739    8.162   4.763
2022-Jan-27 22:00 *   07 22 13.34 +15 45 26.2  -31.7262  1.873913   77.480899   9.673426    8.163   4.764
2022-Jan-27 23:00 N   07 22 11.13 +15 45 28.0  -32.0639  1.865872   87.399559  20.557663    8.165   4.765

 

Note that the Dec listed here is always considerably to the North of the value you observed (+15 38).  It appears that your source for the position was at fault.



#9 *skyguy*

*skyguy*

    Skylab

  • *****
  • Posts: 4,252
  • Joined: 31 Dec 2008
  • Loc: Western New York

Posted 27 January 2022 - 10:32 AM

Yes, the object moving across the top of your image is 7 Iris. Nice catch!

 

However, you should change the date on the image from 2022-01-27 to 2022-01-26 .... wink.gif

 

7-Iris.jpg



#10 nforrester

nforrester

    Sputnik

  • -----
  • topic starter
  • Posts: 33
  • Joined: 07 Sep 2021

Posted 27 January 2022 - 03:22 PM

Due to all of your advice I've been able to reproduce the images in CdC. Thank you!

 

7-iris-chart.png

 

 

Yes, the object moving across the top of your image is 7 Iris. Nice catch!

 

However, you should change the date on the image from 2022-01-27 to 2022-01-26 .... wink.gif

I'm pretty sure I got the date correct. I converted to UTC, which advanced it past midnight.


  • happylimpet and Stu Todd like this

#11 RedLionNJ

RedLionNJ

    Fly Me to the Moon

  • *****
  • Moderators
  • Posts: 5,220
  • Joined: 29 Dec 2009
  • Loc: Red Lion, NJ, USA

Posted 04 February 2022 - 10:57 AM

 

So I took these two pictures tonight, about an hour apart, using a C8 at f/6.3. Based on the Stellarium mobile app I expected to find the asteroid 7 Iris in the middle of the frame. I did not find it there. However, I found a moving point of light near the top of the frame with approximately the right velocity (estimated visually, I haven't done any math yet). It's about 20+/-5 arcminutes from the expected position. Could that be it? What's the typical uncertainty in asteroid orbits? What's the preferred tool for identifying moving dots like this?

 

 
 
The images are about 1° wide by 40' tall, and are centered at approximately 07h 25m 30s / 15° 38' 00".

 

Once I have an image, there are two tools I use for this. They're both free and extremely accurate:

 

MPChecker (https://minorplanetc...bin/checkmp.cgi) from the MPC

 

and 

 

xParallax (from Valencian International University).  I particularly like the visual representation afforded by xParallax.

 

 

"Normal uncertainty", at least for the first few tens of thousands of numbered minor planets, is usually less than 0.1 arcsec.



#12 RazvanUnderStars

RazvanUnderStars

    Surveyor 1

  • *****
  • Posts: 1,569
  • Joined: 15 Jul 2014
  • Loc: Ontario, Canada

Posted 04 February 2022 - 08:22 PM

ASTAP, free as well, marks asteroids on images as well, a demo at https://www.youtube....h?v=oTRzlNlpY7w



#13 jgraham

jgraham

    ISS

  • *****
  • Posts: 22,946
  • Joined: 02 Dec 2004
  • Loc: Miami Valley Astronomical Society

Posted 04 February 2022 - 08:38 PM

I’ve had quite a bit of mixed luck with Sky Safari and Starry Night Pro giving accurate positions of minor planets. Sometimes they are fairly close, other times they are way off. I’ve started using JPL Horizons to get accurate ephemerides.



#14 gmiller123456

gmiller123456

    Ranger 4

  • -----
  • Posts: 331
  • Joined: 25 Dec 2020

Posted 07 February 2022 - 08:24 PM

No manual update should be necessary - it claims to download ephemerides as needed. The most probable cause seems to be a bug in the app.

 

I'll check out CdC, thanks for the tip. This is what you mean, right? https://www.ap-i.net/skychart/en/start

I haven't seen Stellarium claim to update minor planets automatically.  I just did a test in a different thread for Ceres, got an error of many arcmin before updating and just a few arcsec after updating.

 

The updater is pretty buried in the settings, go to: Configuration -> Plugins -> Solar System Editor -> Configure -> Solar System -> Import ....




CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics