1999 June - reworked spectra of SN1999by clearly shows type 1a absorption lines from the initial spectrum of 1999 May 2 - the higher background signal for that date due to relative brightness of the host galaxy within the field. 759nm marks the 'A' absorption line from the Earth's atmosphere.
1999 May 28: SN1999by (designated type 1a pec i.e. sub-luminous by ~2 mags) is noticeably fading in this 5m auto co-added exposure (5x1m).
1999 May 17 - some experimental spectrograms via relay lens projection onto the CCD for ultra-low spectral dispersion. Exposures times for very faint objects become reasonably short but must be balanced against value of data recorded.
1999 May 10/11 - brief spell between heavy showers this evening permitted a few 5min exposures - here three co-added for a 'quick'15min exposure - no darks or flats. SI II @ 612nm prominent even in 60sec exposure! The SN continues to brighten - now ten days 'old'.
1999 May 10 - a pro spectrum of 1999by and my uncalibrated version of 1999 May 6 rescaled to match - vertical lines link compatible features. There is general agreement in the boxed portion - the Starlight chip's sensitivity is best between 450nm - 650nm for faint targets.
1999 May 7 : SN1999by has brightened considerably since the last observation on 1999 May 2 with improved spectra probably due to a better SN ratio.
SN1999by appears to be a type 1a from data supplied by Prof Yamaoka of Kyushu University - Japan. The absorption line wavelengths supplied in his email are added to my spectrum below and correlated quite well. Apparently the absorption line at 575nm is not typical of type 1a whilst the very strong Si II at 612nm is. The low recessional velocity of this host galaxy (~+650km/s) is just below the detection level of the particular spectroscope used and may be regarded as 'static' as comparison star beta Leo.
1999 May 2: pictures below of the new supernova discovered by Ron Arbour (South Wonston - Hants - UK) on 1999 April 30 including its faint spectra at ~m14 in poor conditions [lvm ~ 3.0] in 30 minutes exposure (6x5m co-added). Insufficient data to allocated to either SN type 1a (absorption bands) or type II (emission lines). The undispersed (direct) image of the SN could be snapped in 10s during dusk ! This is a 4 min exposure.....
