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Ursa Astronomical Association

Telescopic comet Helin-Roman-Alu - 11.4.2021 at 00.51 - 11.4.2021 at 01.12 Orimattila, Artjärvi, Tähtikallio Observation number 97991

Visibility I / V


117P / (Helin-Roman-Alu) A comet from the Jupiter family was filmed on the second night of the April 2021 campaign. Quote from GARY W.KRONK'S COMETOGRAPHY: Eleanor F.Helin, Brian P. Roman, and Jeff Alu (Palomar Observatory, California, USA) found this comet in images obtained with a 0.46 m Schmidt telescope in 1989, October 2.42 and 2.44 . They described some condensation as diffuse and estimated the brightness to be 17.5. They confirmed the comet on October 5 and 6. source http://cometography.com/pcomets/117p.html . Gary W. Kronk's great cometography site also has a lot of historical information, definitely worth a look! http://cometography.com/ . Eleanor Key Francis Glo Helin was an American astronomer, he was e.g. Principal Investigator of NASA's Jet Propulsion Laboratory's Near Earth Asteroid Tracking Program.
American astronomer Brian Roman has found comets 111P / Helin-Roman-Crockett, 117P / Helin-Roman-Alu, 132P / Helin-Roman-Alu and 11 asteroids, source Wikipedia https://en.wikipedia.org/wiki/Brian_P. _Roman . American amateur astronomer Jeffrey (Jeff) Thomas Alu is
found a total of 2 comets and 24 asteroids, source Wikipedia https://en.wikipedia.org/wiki/Jeff_T._Alu . When photographing the comet was 2.6903au away, the closest it is 2.6819au on April 18, 2021. The core of the comet is about 9km in size.

1Picture. stacked summary image according to the stars, the movement is shown. Asteroid (83027) 2001 QB180 18.111mag, motion shown. Asteroid (34454) 2000 SB86 18.339mag, motion shown. Asteroid (56833) 2000 QN33 18.725mag, motion shown. Asteroid (127536) 2002 XO26 18.952mag, motion shown. Asteroid (94044) 2000 XW53 19.653mag, motion shown. Asteroid (186672) 2003 YX98 19,815mag, motion shown. No other asteroids below 20.0 mag are shown.

2Picture. Stacked by Averace (average) comet, stretched with MaximDL Histogram Specification Gaussian filter, comma 26 "and tail at 17" 84 ". The near star interferes badly because it is in the direction of the tail.
3Picture. first picture measured, 2021-04-10T 21: 51: 22UT 2459315.41067JDUT 13h24m05.56s -00d44'37.8 "N16.577mag Std Dev 205.630 SNR51.593 FWHM5.643", JPL Horizon 21: 51: 22UT 13h24m05.60s -00d44 '37 .7 "T16.314 / N16.444mag.
4Picture. last image measured, 2021-04-10UT 22: 12: 17UT 2459315.42519JDUT 13h24m04.93s -00d44'35.0 "N16.543mag Std Dev 169.293 SNR54.305 FWHM7.180", JPL Horizon 22: 12: 17UT 13h24m05.01s -00d44 '35 .3 "T16.314 / N16.444mag. TYC 4959-507-1 used for brightness measurement calibration
12.44mag stars.



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Additional information
  • Observation target
    • Comet
  • Title for the comet
    • Telescopic comet
  • Name of the observation target
    • 117P/Helin-Roman-Alu
  • Tail length
  • 84 arc seconds
  • Coma diameter
  • 26 kaarisekuntia
  • Weather
    • Erittäin hyvä säätila.

Technical information

Alluna RC16, C415 / 3320, Moravian G4-16000EC MkII, filter L, bin3 11 x 120s

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