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Ursa Astronomical Association
Kopernikuksentie 1
00130 Helsinki

Ursa Astronomical Association

Telescopic comet NEOWISE - 18.3.2021 at 21.31 - 18.3.2021 at 23.45 Helsinki, Maunula Observation number 96924

Visibility I / V

Jorma Ryske, Etelä-Suomen kosmol. seura

Comet C/2021 A2 (NEOWISE) is now much dimmer than I last observed it at February 16th. In this 115min exposure using 387nm narrowband filter cyanogen CN 3883Å radical gas coma diameter is 0,6'/40.000km and wide fan-shaped cyanogen gas tail length 1'/60.000km towards PA 330° is visible. Comet current distance from sun is 1,62au and from earth 1,43au. I took also R channel photometric image and although the image had poor S/N I measured comet R channel brightness as 16,3mag. CN channel brightness measurement is difficult because lack of 3883Å reference stars, not very scientific but when using B channel reference stars I measured comet CN coma roughly brightness as 15,1mag.

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Additional information
  • Observation target
    • Comet
  • Name of the observation target
    • C/2021 A2 (NEOWISE)
    • Erittäin heikosti näkyvä
  • Brightness in magnitudes
    • 16,3
  • Tail length
  • 1 arc minutes
  • Coma diameter
  • 0,6 kaariminuuttia
  • Weather
    • SQM-L 22:30 17,63 Zenit (snow on ground) -5C
  • Title for the comet
    • Telescopic comet
Technical information

TS 305/1200mm Newton, TS KomakorrF4, QSI690, Semrock CN 387nm/15nm, CEM60. FoV 25' x 20'. North up, east left.

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