- Nova Aql'99 [2] page 2 latest 2000 May 30 - 2000 July
- Nova Aql'99 [1]
- Nova 1917 = CI Aql
- main spectroscopy page.
- my homepage
2000 Jan 4: Clear at dusk and more spectra @ 4nm. The spectrum appears to show continued changes since Jan 1 - although Ha still dominates.
2000 Jan 1: My first observations of the Millennium and 15th evening of spectra of the nova in a clear slot at dusk @ 4nm/pixel plus a wide-angle shot.
1999 Dec 29: First clear early evening for 10 days to catch the nova at 4nm and 2nm. Some changes on the overall spectrum noted. Ha remains as strong as ever with bold lines at 572nm emerging and another in near-IR mimicking Nova Aql'99[1] in late summer'99.
1999 Dec 20: In very poor transparency with adjacent Altair only just visible to the naked-eye, the fading nova's Ha line just detectable @1A.
1999 Dec 19: Very clear evening and repeat Ha spectra @ 1A. Surprisingly the maximum of the twin peaks has swapped from a blueshift to a redshift over 72 hours.
1999 Dec 16: Clear at dusk so better SN ratio with nova at reasonable altitude. Ha profile repeated but essentially the same as previous evening although the 'slope' better defined. Hb region and near-IR sampled at 3A/pixel.
1999 Dec 15: More colour spectra @ 16A plus reinstated SBIG spectrometer @ 1A. From Ha spectra this seems to indicate the fireball is becoming transparent. The outer brightest regions are also the areas of maximum velocity.
1999 Dec 14: Nineth evening of spectra - nova has faded noticeably to ~mag 8 [VSNet quotes mv 6.4] as judged by K-type stars in the field. More spectra via MX5c at very low [40A/pixel] resolution - low in the west. Note the real image of the Nova seems orange and the blue end of the spectrum is curved upwards - due to low altitude and atmospheric refraction. Grey portion of spectrum is in infra-red and contains three emission lines.
1999 Dec 11: Nova fading - evidence of slight defocusing via 'finder' camera images [using 135mm fl f/2.8 lens] rather like stars with IR excess.
1999 Dec 10: Nova now fading, according to reports and probably ~mv6 currently. Swapped the mono Starlight Xpress MX9 for the MX5c. The Nova is quite stunning via this one-shot colour camera and covers from 374nm [UV] to 958nm [IR] at 1.6nm[16A]/pixel. Care needed so as not to overexposure the spectrum due to brilliance of the Ha line. Half the spectrum to the right in 'colourless' IR shows emission lines too. The earlier sequence via the SBIG spectrometer of Ha at hi-res [1A] extended and annotated.
1999 Dec 9: More spectra of Nova @ 40A/pixel. This earlier unique amateur hi-res [1A] sequence shows changes in Ha 48 hours after discovery. Doppler broadening indicates high velocities of explosive outflowing gas directed both towards [blueshift] and away [redshift] from Earth but biased towards a redshift. Approximate values indicated - a trip round the sun in Earth orbit at 2000km/s would only take 5.5days ! Initially strong absorption line from hydrogen gas seen against the star's photosphere [P-Cyg profile] fades in the glare of the expanding fireball.
1999 Dec 8: MX9 camera in use @ 40A/pixel. Nova captured in short 30s exposures through small cloudbreaks to within 10o of the horizon - the spectrum curved due to atmospheric refraction.
1999 Dec 7: Clearest evening for some days. Amazingly in full twilight at 4.30pm [16.30UT] the Nova could be captured in 1s exposure [including the spectrum] via the 30cm LX200 with only Vega and Altair visible to the naked-eye. The Ha line in skylight weakly superimposed across the very broad [Doppler broadened] Ha emission line - acting a static reference.
1999 Dec 4/5: More spectra obtained during short clear slots at dusk on both evenings. All the spectral lines recorded appear in emission and all are very wide partially due Doppler broadening from high expansion velocities. This is very obvious in the most prominent emission line of Ha at 656.3nm - the line has expanded in the first 24hrs of observation now grossing ~4000km/s but biased towards a redshift.
The initial strong blueshifted dark line [line-of-sight absorption against the star's photosphere ie classic P Cyg profile] has been overtaken by emission and the absorption line, by comparison, has got progressively weaker over 48hrs - see spectra below. Other identified emission lines include Hb which mimics Ha but is much weaker.
1999 Dec 3: I learnt of the nova late this afternoon via the Internet and immediately got the scope ready in slightly hazy skies at dusk - Aquila being low in the WSW. Nova easily visible in binocular below Altair and glimpsed with naked-eye. A widefield shot [digital copy of the electronic finder screen !] and spectra obtained via 30cm SCT+SBIG spectrometer at both 1A and 4A resolution. Arrived late at my Ewell Astro Soc monthly meeting to advise of 'the new star'.
