BAA Comet Section : 1995 comets

Updated 2000 August 20

  • 1995 O1 Hale-Bopp
    • When observing a comet please try to forget how bright you think the comet should be, what it was when you last viewed it, what other observers think it is or what the ephemeris says it should be.

    The equations for the light curves of comets that are currently visible use only the raw observations and should give a reasonable prediction for the current brightness. If the comet has not yet been observed or has gone from view a correction for aperture is included, so that telescopic observers should expect the comet to be fainter than given by the equation. The correction is about 0.033 per centimetre. Values for the r parameter given in square brackets [ ] are assumed. The form of the light curve is either the standard m = H0 + 5 log d + K0 log r or the linear brightening m = H0 + 5 log d + L0 abs(t - T + D0) where T is the date of perihelion, t the present and D0 an offset, if L0 is +ve the comet brightens towards perihelion and if D0 is +ve the comet is brightest prior to perihelion.

    Comet 1995 O1 Hale-Bopp , the great comet of 1997, is fading slowly past 14m. It is only observable from Southern Hemisphere locations as it loops round Mensa.
    Comet 1995 O1 Hale-Bopp , the great comet of 1997, is fading slowly and will still be 11m at the beginning of the year, fading to 13m by the year's end. It is only observable from Southern Hemisphere locations as it loops round the Large Magellanic Cloud.

    Observations by Albert Jones in mid 1998, using a large reflector put it at 10th mag, whilst those by Jose Aguiar give around 9.5 in a 0.23-m reflector. Jonathan Shanklin observing from the Falkland Islands in November 1998 made in 10.5 in 20x80B.

    An observation by Andrew Pearce in late August 1999 made it 12.5. Andrew reported another nuclear outburst in mid October: Oct 20.84UT: m1=12.8, Dia=0.8', DC=7/...41cm reflector (90x)...Andrew Pearce, Nedlands, Western Australia The comet seems to undergone some form of nuclear outburst again! Very prominent central condensation visible which is in stark contrast to the fairly diffuse appearance 2 nights ago. I checked the DSS image of this field to ensure that the comet wasn't sitting over the top of a field star given it the appearnce of a bright central condensation, however the DSS image does not show any star brighter than about 16-17th mag. Outer coma very difficult to detect due to the brightness of the central condensation. There is no real increase in the overall total brightness of the coma, just a very evident change in it's morphology. Amazing that this comet is still displaying this activity at nearly 10 AU from the Sun.

    This analysis of the comet's light curve, coma diameter and tail length was made for the TA special supplement on the comet which was published in the autumn of 1997. Over the entire apparition (717 days with observations, spread over 1336 days) the comet has the corrected lightcurve :
    -0.71 + 5 log d + 7.74 log r
    There are significant variations from this, and the comet is currently nearly a little brighter than indicated by this equation.

    For more information on the comet see the CBAT or ESO pages.

    1995 observations (9kb) / 1996 observations (118kb) / 1997 observations (Jan - April) (133kb) / 1997 observations (May - December) (42kb) / 1998 - 2000 observations (18kb) in ICQ format, last observation 2000 July 4, updated 2000 August 16.

    More information on LINEAR.
    The Northumberland refractor is the telescope that was used in the search for Neptune. It now has a 0.30-m f20 doublet lens which gives a stellar limiting magnitude of around 15 at the zenith on good nights. The Thorrowgood refractor was built in 1864 and has a 0.20-m f14 doublet lens.
    Published by Jonathan Shanklin. Jon Shanklin - jds@ast.cam.ac.uk