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2012 TC4: A request for astrometry

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  • Lance Benner
    Greeetings MPML, 2012 TC4 is a potential radar target later this week, but the plane-of-sky pointing uncertainties around the closest approach are too large
    Message 1 of 14 , Oct 8, 2012
      Greeetings MPML,

      2012 TC4 is a potential radar target later this week, but the plane-of-sky
      pointing uncertainties around the closest approach are too large for us,
      so we are requesting astrometry. Please report it to the minor planet
      center as usual.

      The nominal close approach will be at 0.000635 AU (0.25 Earth-Moon distances)
      on October 12. With an absolute magnitude of 26.5, this object could be roughly
      16 meters in diameter.

      Regards,

      Lance Benner, on behalf of the radar team
    • Alan W Harris
      For anyone doing photometry on this object, the spin period is almost certain to be under 1 hour, possibly much under an hour, so short exposures will be
      Message 2 of 14 , Oct 8, 2012
        For anyone doing photometry on this object, the spin period is almost
        certain to be under 1 hour, possibly much under an hour, so short exposures
        will be necessary to do a lightcurve.

        Alan

        At 09:59 AM 10/8/2012, Lance Benner wrote:
        >Greeetings MPML,
        >
        >2012 TC4 is a potential radar target later this week, but the plane-of-sky
        >pointing uncertainties around the closest approach are too large for us,
        >so we are requesting astrometry. Please report it to the minor planet
        >center as usual.
        >
        >The nominal close approach will be at 0.000635 AU (0.25 Earth-Moon distances)
        >on October 12. With an absolute magnitude of 26.5, this object could be
        >roughly
        >16 meters in diameter.
        >
        >Regards,
        >
        >Lance Benner, on behalf of the radar team
        >
        >
        >
        >------------------------------------
        >
        >~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        >
        >Posts to this list or information found within may be freely used, with
        >the stipulation that MPML and the originating author are cited as the
        >source of the information.Yahoo! Groups Links
        >
        >
        >
        *****************************************************************************
        Alan Harris Phone: 818-790-8291
        4603 Orange Knoll Ave.
        La Cañada, CA 91011-3364
        email: harrisaw@...
        *****************************************************************************
      • Wiggins Patrick
        I sat on 2012 TC4 for about 3 hours tonight. I started out taking 1 minute exposures with two minutes between exposures but after an hour changed that to 1
        Message 3 of 14 , Oct 8, 2012
          I sat on 2012 TC4 for about 3 hours tonight. I started out taking 1 minute exposures with two minutes between exposures but after an hour changed that to 1 minute exposures with one minute between exposures.

          In the end I had to cobble together 3 sets of data into a single LC. I've never tried putting pieces together like that meaning I've no idea how close my curve comes to reality so I've posted it at the following URL so it can be compared to others' work:

          http://users.wirelessbeehive.com/~paw/temp/2012TC4-01.jpg

          Details: C-14 @ f/5.5, ST-10XME binned 3x3, -10C, no filter.

          patrick
          718


          On 08 Oct 2012, at 11:44, Alan W Harris wrote:

          > For anyone doing photometry on this object, the spin period is almost
          > certain to be under 1 hour, possibly much under an hour, so short exposures
          > will be necessary to do a lightcurve.
          >
          > Alan
        • Leonid Elenin
          I think what now, this asteroid too faint for acceptable photometry with 14-16 telescopes. Errors too large. Regards, Leonid Elenin ISON-NM Observatory (H15)
          Message 4 of 14 , Oct 9, 2012
            I think what now, this asteroid too faint for acceptable photometry with 14-16" telescopes. Errors too large.


            Regards,
            Leonid Elenin
            ISON-NM Observatory (H15)
          • John W Briggs
            I am still running on 2012 TC4, having switched to 1-minute exposures as friends on this list suggested earlier tonight. I m using no delay between the
            Message 5 of 14 , Oct 9, 2012
              I am still running on 2012 TC4, having switched to 1-minute exposures as
              friends on this list suggested earlier tonight. I'm using no delay between
              the exposures beyond the short read-out time of my 2x2 binned images. I
              suggest using no delay between exposures, because the object is changing so
              clearly in my exposure-to-exposure sequence. If were using a larger
              telescope than our 16-inch, I'm sure an even faster cadence would be
              justified.

              --John.

              John W. Briggs
              HUT Observatory, H16
              Eagle, Colorado, USA


              On Tue, Oct 9, 2012 at 12:48 AM, Wiggins Patrick <paw@...>wrote:

              > **
              >
              >
              > I sat on 2012 TC4 for about 3 hours tonight. I started out taking 1 minute
              > exposures with two minutes between exposures but after an hour changed that
              > to 1 minute exposures with one minute between exposures.
              >
              > In the end I had to cobble together 3 sets of data into a single LC. I've
              > never tried putting pieces together like that meaning I've no idea how
              > close my curve comes to reality so I've posted it at the following URL so
              > it can be compared to others' work:
              >
              > http://users.wirelessbeehive.com/~paw/temp/2012TC4-01.jpg
              >
              > Details: C-14 @ f/5.5, ST-10XME binned 3x3, -10C, no filter.
              >
              > patrick
              > 718
              >
              > On 08 Oct 2012, at 11:44, Alan W Harris wrote:
              >
              > > For anyone doing photometry on this object, the spin period is almost
              > > certain to be under 1 hour, possibly much under an hour, so short
              > exposures
              > > will be necessary to do a lightcurve.
              > >
              > > Alan
              >
              >


              [Non-text portions of this message have been removed]
            • walcom77
              Dear Lance & All We just observed 2012 TC4 and sent the astrometry to the MPC as usual (Lance, you were in cc). Hope this can help you! We wrote about this
              Message 6 of 14 , Oct 9, 2012
                Dear Lance & All

                We just observed 2012 TC4 and sent the astrometry to the MPC as usual
                (Lance, you were in cc). Hope this can help you!

                We wrote about this close approach on our blog too:

                http://bit.ly/QQv6q4

                Ciao,
                Ernesto Guido, Giovanni Sostero & Nick Howes
                http://remanzacco.blogspot.com
                http://twitter.com/comets77
              • Brian Warner
                It depends on the amplitude. I ve worked objects this faint with 14 and gotten very usable results because the amplitude was about 0.8 mag. More Data! Clear
                Message 7 of 14 , Oct 9, 2012
                  It depends on the amplitude. I've worked objects this faint with 14" and gotten
                  very usable results because the amplitude was about 0.8 mag.

                  More Data!


                  Clear Skies,
                  Brian D. Warner
                  Palmer Divide Observatory

                  On 10/09/2012 01:16, Leonid Elenin wrote:
                  > I think what now, this asteroid too faint for acceptable photometry with 14-16" telescopes. Errors too large.
                  >
                  >
                  > Regards,
                  > Leonid Elenin
                  > ISON-NM Observatory (H15)
                  >
                • John W Briggs
                  The amplitude is certainly large with 2012 TC4. I kept on it for 330 1-minute exposures last night, and when I blink these frames, the changing brightness of
                  Message 8 of 14 , Oct 9, 2012
                    The amplitude is certainly large with 2012 TC4. I kept on it for 330
                    1-minute exposures last night, and when I blink these frames, the changing
                    brightness of the object is delightfully obvious.

                    --John W. Briggs,
                    HUT Observatory, H16
                    Eagle, Colorado

                    On Tue, Oct 9, 2012 at 6:55 AM, Brian Warner
                    <Brian@...>wrote:

                    > **
                    >
                    >
                    > It depends on the amplitude. I've worked objects this faint with 14" and
                    > gotten
                    > very usable results because the amplitude was about 0.8 mag.
                    >
                    > More Data!
                    >
                    > Clear Skies,
                    > Brian D. Warner
                    > Palmer Divide Observatory
                    >
                    >
                    > On 10/09/2012 01:16, Leonid Elenin wrote:
                    > > I think what now, this asteroid too faint for acceptable photometry with
                    > 14-16" telescopes. Errors too large.
                    > >
                    > >
                    > > Regards,
                    > > Leonid Elenin
                    > > ISON-NM Observatory (H15)
                    > >
                    >
                    >
                    >


                    [Non-text portions of this message have been removed]
                  • Alan W Harris
                    ... As Brian Warner notes, you should not let photons fall on the floor when you are struggling for enough signal. Take frames successively as fast as you
                    Message 9 of 14 , Oct 9, 2012
                      At 11:48 PM 10/8/2012, Wiggins Patrick wrote:
                      >I sat on 2012 TC4 for about 3 hours tonight. I started out taking 1
                      >minute exposures with two minutes between exposures but after an hour
                      >changed that to 1 minute exposures with one minute between exposures.

                      As Brian Warner notes, you should not let photons fall on the floor when
                      you are struggling for enough signal. Take frames successively as fast as
                      you can. In cases like this object which appears to have a very short
                      rotation period, cut exposures as short as possible, which will be either
                      when the exposure time is about equal to the readout time, or when the
                      individual images don't show the object clearly (say S/N of only ten or
                      less). In the extreme, there may also be problems with scintillation and
                      such, but exposures of one minute or even less should not be a problem.

                      I would further note that this may be a complex rotator (tumbler) rather
                      than a simple periodic variation. Patrick's lightcurve, if it is more than
                      noise, looks like a typical lightcurve of a tumbler, with two beating
                      frequency components. But there can be another beat too, with the exposure
                      frequency, so it is good to vary the exposure timings a bit too, so that a
                      set cadence doesn't create additional aliases.

                      MoreData!

                      Alan

                      *****************************************************************************
                      Alan Harris Phone: 818-790-8291
                      4603 Orange Knoll Ave.
                      La Cañada, CA 91011-3364
                      email: harrisaw@...
                      *****************************************************************************
                    • Richard Miles
                      Have reported 19 astrometric positions to the MPC (also copied to Lance Benner) based on a short 22-minute observing run using the Faulkes Telescope South this
                      Message 10 of 14 , Oct 9, 2012
                        Have reported 19 astrometric positions to the MPC (also copied to Lance
                        Benner) based on a short 22-minute observing run using the Faulkes Telescope
                        South this afternoon.

                        10-sec exposures were used to exclude the possibility of rotation periods of
                        the order of 1 min. Folding the lightcurve data appears to show a period of
                        0.0084+/-0.0002 days (726+/-18 sec) and an amplitude of 1.2+/-0.2 mag.
                        However, as Alan has pointed out, this object may be a tumbler. Certainly
                        the data show one or two small discrepancies, so a multi-period solution may
                        ultimately yield a better fit to the data.

                        Richard Miles
                        BAA

                        ----- Original Message -----
                        From: "John W Briggs" <john.w.briggs@...>
                        To: <brian@...>
                        Cc: "Leonid Elenin" <l.elenin@...>; <mpml@yahoogroups.com>
                        Sent: Tuesday, October 09, 2012 1:12 PM
                        Subject: Re: {MPML} Attempt at 3 hour LC for 2012 TC4


                        > The amplitude is certainly large with 2012 TC4. I kept on it for 330
                        > 1-minute exposures last night, and when I blink these frames, the changing
                        > brightness of the object is delightfully obvious.
                        >
                        > --John W. Briggs,
                        > HUT Observatory, H16
                        > Eagle, Colorado
                        >
                        > On Tue, Oct 9, 2012 at 6:55 AM, Brian Warner
                        > <Brian@...>wrote:
                        >
                        >> It depends on the amplitude. I've worked objects this faint with 14" and
                        >> gotten
                        >> very usable results because the amplitude was about 0.8 mag.
                        >>
                        >> More Data!
                        >>
                        >> Clear Skies,
                        >> Brian D. Warner
                        >> Palmer Divide Observatory
                      • John W Briggs
                        I m going to try it again tonight if the weather holds here in Colorado, perhaps using 30- or 45-second exposures, in a long series. --John. John W. Briggs
                        Message 11 of 14 , Oct 9, 2012
                          I'm going to try it again tonight if the weather holds here in Colorado,
                          perhaps using 30- or 45-second exposures, in a long series. --John.

                          John W. Briggs
                          HUT Observatory, H16
                          Eagle, Colorado

                          On Tue, Oct 9, 2012 at 12:35 PM, Richard Miles
                          <rmiles.btee@...>wrote:

                          > **
                          >
                          >
                          > Have reported 19 astrometric positions to the MPC (also copied to Lance
                          > Benner) based on a short 22-minute observing run using the Faulkes
                          > Telescope
                          > South this afternoon.
                          >
                          > 10-sec exposures were used to exclude the possibility of rotation periods
                          > of
                          > the order of 1 min. Folding the lightcurve data appears to show a period
                          > of
                          > 0.0084+/-0.0002 days (726+/-18 sec) and an amplitude of 1.2+/-0.2 mag.
                          > However, as Alan has pointed out, this object may be a tumbler. Certainly
                          > the data show one or two small discrepancies, so a multi-period solution
                          > may
                          > ultimately yield a better fit to the data.
                          >
                          > Richard Miles
                          > BAA
                          >
                          > ----- Original Message -----
                          > From: "John W Briggs" <john.w.briggs@...>
                          > To: <brian@...>
                          > Cc: "Leonid Elenin" <l.elenin@...>; <mpml@yahoogroups.com>
                          > Sent: Tuesday, October 09, 2012 1:12 PM
                          > Subject: Re: {MPML} Attempt at 3 hour LC for 2012 TC4
                          >
                          > > The amplitude is certainly large with 2012 TC4. I kept on it for 330
                          > > 1-minute exposures last night, and when I blink these frames, the
                          > changing
                          > > brightness of the object is delightfully obvious.
                          > >
                          > > --John W. Briggs,
                          > > HUT Observatory, H16
                          > > Eagle, Colorado
                          > >
                          > > On Tue, Oct 9, 2012 at 6:55 AM, Brian Warner
                          > > <Brian@...>wrote:
                          > >
                          > >> It depends on the amplitude. I've worked objects this faint with 14" and
                          > >> gotten
                          > >> very usable results because the amplitude was about 0.8 mag.
                          > >>
                          > >> More Data!
                          > >>
                          > >> Clear Skies,
                          > >> Brian D. Warner
                          > >> Palmer Divide Observatory
                          >
                          >
                          >


                          [Non-text portions of this message have been removed]
                        • Alan W Harris
                          If Richard s period is about right, you should hold to exposures no longer than 30 sec to avoid losing detail of the curve. Since your readout is only a few
                          Message 12 of 14 , Oct 9, 2012
                            If Richard's period is about right, you should hold to exposures no longer
                            than 30 sec to avoid losing detail of the curve. Since your readout is
                            only a few seconds, that should still be quite minimal dead-time loss. And
                            a long series is good, I expect complex structure.

                            Alan

                            At 12:14 PM 10/9/2012, John W Briggs wrote:
                            >I'm going to try it again tonight if the weather holds here in Colorado,
                            >perhaps using 30- or 45-second exposures, in a long series. --John.
                            >
                            >John W. Briggs
                            >HUT Observatory, H16
                            >Eagle, Colorado
                            >
                            >On Tue, Oct 9, 2012 at 12:35 PM, Richard Miles
                            ><rmiles.btee@...>wrote:
                            >
                            > > **
                            > >
                            > >
                            > > Have reported 19 astrometric positions to the MPC (also copied to Lance
                            > > Benner) based on a short 22-minute observing run using the Faulkes
                            > > Telescope
                            > > South this afternoon.
                            > >
                            > > 10-sec exposures were used to exclude the possibility of rotation periods
                            > > of
                            > > the order of 1 min. Folding the lightcurve data appears to show a period
                            > > of
                            > > 0.0084+/-0.0002 days (726+/-18 sec) and an amplitude of 1.2+/-0.2 mag.
                            > > However, as Alan has pointed out, this object may be a tumbler. Certainly
                            > > the data show one or two small discrepancies, so a multi-period solution
                            > > may
                            > > ultimately yield a better fit to the data.
                            > >
                            > > Richard Miles
                            > > BAA
                            > >
                            > > ----- Original Message -----
                            > > From: "John W Briggs" <john.w.briggs@...>
                            > > To: <brian@...>
                            > > Cc: "Leonid Elenin" <l.elenin@...>; <mpml@yahoogroups.com>
                            > > Sent: Tuesday, October 09, 2012 1:12 PM
                            > > Subject: Re: {MPML} Attempt at 3 hour LC for 2012 TC4
                            > >
                            > > > The amplitude is certainly large with 2012 TC4. I kept on it for 330
                            > > > 1-minute exposures last night, and when I blink these frames, the
                            > > changing
                            > > > brightness of the object is delightfully obvious.
                            > > >
                            > > > --John W. Briggs,
                            > > > HUT Observatory, H16
                            > > > Eagle, Colorado
                            > > >
                            > > > On Tue, Oct 9, 2012 at 6:55 AM, Brian Warner
                            > > > <Brian@...>wrote:
                            > > >
                            > > >> It depends on the amplitude. I've worked objects this faint with 14" and
                            > > >> gotten
                            > > >> very usable results because the amplitude was about 0.8 mag.
                            > > >>
                            > > >> More Data!
                            > > >>
                            > > >> Clear Skies,
                            > > >> Brian D. Warner
                            > > >> Palmer Divide Observatory
                            > >
                            > >
                            > >
                            >
                            >
                            >[Non-text portions of this message have been removed]
                            >
                            >
                            >
                            >------------------------------------
                            >
                            >~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
                            >
                            >Posts to this list or information found within may be freely used, with
                            >the stipulation that MPML and the originating author are cited as the
                            >source of the information.Yahoo! Groups Links
                            >
                            >
                            >
                            *****************************************************************************
                            Alan Harris Phone: 818-790-8291
                            4603 Orange Knoll Ave.
                            La Cañada, CA 91011-3364
                            email: harrisaw@...
                            *****************************************************************************
                          • John W Briggs
                            Alan, do you recommend that I bag the R filter that I used last night, and instead shoot clear tonight? It continues to look like good weather here, and I
                            Message 13 of 14 , Oct 9, 2012
                              Alan, do you recommend that I bag the R filter that I used last night, and
                              instead shoot clear tonight? It continues to look like good weather here,
                              and I should be able to ride it for over seven hours with 30-second
                              exposures. Fun stuff!

                              Details: 16-inch DFM reflector, f/8; Apogee U47 camera, back-illuminated
                              1024x1024 CCD, 13-micron pixels, normally binned 2x2 for an effective
                              512x512 array.

                              --John.
                              HUT Observatory, H16
                              Eagle, Colorado

                              On Tue, Oct 9, 2012 at 2:52 PM, Alan W Harris <harrisaw@...> wrote:

                              > If Richard's period is about right, you should hold to exposures no longer
                              > than 30 sec to avoid losing detail of the curve. Since your readout is
                              > only a few seconds, that should still be quite minimal dead-time loss. And
                              > a long series is good, I expect complex structure.
                              >
                              > Alan
                              >
                              >
                              > At 12:14 PM 10/9/2012, John W Briggs wrote:
                              >
                              >> I'm going to try it again tonight if the weather holds here in Colorado,
                              >> perhaps using 30- or 45-second exposures, in a long series. --John.
                              >>
                              >> John W. Briggs
                              >> HUT Observatory, H16
                              >> Eagle, Colorado
                              >>
                              >> On Tue, Oct 9, 2012 at 12:35 PM, Richard Miles
                              >> <rmiles.btee@...>**wrote:
                              >>
                              >> > **
                              >>
                              >> >
                              >> >
                              >> > Have reported 19 astrometric positions to the MPC (also copied to Lance
                              >> > Benner) based on a short 22-minute observing run using the Faulkes
                              >> > Telescope
                              >> > South this afternoon.
                              >> >
                              >> > 10-sec exposures were used to exclude the possibility of rotation
                              >> periods
                              >> > of
                              >> > the order of 1 min. Folding the lightcurve data appears to show a period
                              >> > of
                              >> > 0.0084+/-0.0002 days (726+/-18 sec) and an amplitude of 1.2+/-0.2 mag.
                              >> > However, as Alan has pointed out, this object may be a tumbler.
                              >> Certainly
                              >> > the data show one or two small discrepancies, so a multi-period solution
                              >> > may
                              >> > ultimately yield a better fit to the data.
                              >> >
                              >> > Richard Miles
                              >> > BAA
                              >> >
                              >> > ----- Original Message -----
                              >> > From: "John W Briggs" <john.w.briggs@...>
                              >> > To: <brian@...**>
                              >> > Cc: "Leonid Elenin" <l.elenin@...>; <mpml@yahoogroups.com>
                              >> > Sent: Tuesday, October 09, 2012 1:12 PM
                              >> > Subject: Re: {MPML} Attempt at 3 hour LC for 2012 TC4
                              >> >
                              >> > > The amplitude is certainly large with 2012 TC4. I kept on it for 330
                              >> > > 1-minute exposures last night, and when I blink these frames, the
                              >> > changing
                              >> > > brightness of the object is delightfully obvious.
                              >> > >
                              >> > > --John W. Briggs,
                              >> > > HUT Observatory, H16
                              >> > > Eagle, Colorado
                              >> > >
                              >> > > On Tue, Oct 9, 2012 at 6:55 AM, Brian Warner
                              >> > > <Brian@...**>wrote:
                              >> > >
                              >> > >> It depends on the amplitude. I've worked objects this faint with 14"
                              >> and
                              >> > >> gotten
                              >> > >> very usable results because the amplitude was about 0.8 mag.
                              >> > >>
                              >> > >> More Data!
                              >> > >>
                              >> > >> Clear Skies,
                              >> > >> Brian D. Warner
                              >> > >> Palmer Divide Observatory
                              >> >
                              >> >
                              >> >
                              >>
                              >>
                              >> [Non-text portions of this message have been removed]
                              >>
                              >>
                              >>
                              >> ------------------------------**------
                              >>
                              >> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~**~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~**~~~~~~~~
                              >>
                              >> Posts to this list or information found within may be freely used, with
                              >> the stipulation that MPML and the originating author are cited as the
                              >> source of the information.Yahoo! Groups Links
                              >>
                              >>
                              >>
                              >
                              > ****************************************************************
                              > *****************
                              > Alan Harris Phone: 818-790-8291
                              > 4603 Orange Knoll Ave.
                              > La Cañada, CA 91011-3364
                              > email: harrisaw@...
                              > *********************************************************************************
                              >
                              >


                              [Non-text portions of this message have been removed]
                            • Alan W Harris
                              Depends a bit on your sky and such. If you get a better S/N shooting clear, then yes, do it. I think absolute color-calibrated photometry will be of marginal
                              Message 14 of 14 , Oct 9, 2012
                                Depends a bit on your sky and such. If you get a better S/N shooting
                                clear, then yes, do it. I think absolute color-calibrated photometry will
                                be of marginal value, especially with some bigger guns (Richard Miles with
                                the Faulkes 2-m) doing the filter photometry.

                                At 02:10 PM 10/9/2012, John W Briggs wrote:
                                >Alan, do you recommend that I bag the R filter that I used last night, and
                                >instead shoot clear tonight? It continues to look like good weather here,
                                >and I should be able to ride it for over seven hours with 30-second
                                >exposures. Fun stuff!
                                >
                                >Details: 16-inch DFM reflector, f/8; Apogee U47 camera, back-illuminated
                                >1024x1024 CCD, 13-micron pixels, normally binned 2x2 for an effective
                                >512x512 array.
                                >
                                >--John.
                                >HUT Observatory, H16
                                >Eagle, Colorado

                                *****************************************************************************
                                Alan Harris Phone: 818-790-8291
                                4603 Orange Knoll Ave.
                                La Cañada, CA 91011-3364
                                email: harrisaw@...
                                *****************************************************************************
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