Hmmm
Now working at R=4040....
Could have done with more exposure time....
The Hb region is the first processed...showing the now "standard P-Cyg" in both the Hb and Fe lines.
I've run a velocity graph based on the Hb (4861A) showing the larger absorption is still around the 1600Km/s
Feedback/ comments welcome.
Nice.
As Malc will vouch for, I've been quite strident in another place about how the SA100 spectra are far too low-resolution to be used for velocity calculations, given that a single pixel makes a difference of +/- 300 km/s. Nevertheless (don't the ll anyone) I ran the velocity calculation on a nice P Cygni profile that was present on the Na D line in my spectrum of a few days ago, and got ... 1600 km/s :-)
Jon,
We have all got to make the best use of the equipment we have...
I'd never knock the gratings...my ol' Baader 207 l/mm has paid for itself over and over.
Things just get a little more complicated when you move to slit spectroscopy....and working with reference lamps/ calibration etc. (As Mark is about to find out )
Don't get me wrong - my SA100 is easily the best $150-odd I've spent in astronomy. If you'd told me six months ago that I'd be observing the emergence of forbidden [OI] lines in the thinning ejecta of a nova in Centaurus, as it happens in real time, using a tiny bit of kit I ordered from Bintel on a whim, I'd have laughed at you.
Don't you get the feeling that there's this enormous, cataclysmic cosmic event going on in our celestial backyard (I mean, it's almost on our bloomin' FLAG, for heaven's sake) and the five of us have got a ringside seat to watching astrophysical history in the making!
Here is tonight's spectrum. The [OI] and [NII] lines keep growing.
The continuum seems to slope towards the blue. I've noticed it doing that during the maxima of its rebrightenings. I wonder what's causing that effect?
Looking good Ken. I wonder if that's another lower velocity absorption feature starting to show? Time will tell.
Are you confident with the wavelength calibration? The zero point in your velocity plot is way off the centre of the curve, whereas it is quite central in your Hb plot.
Hmmmm
That didn't go well!!
I upped the exposure to 40 x 30s to get better SNR, and "re-adjusted" the grating and slit assembly to get more consistent positioning on the CCD. The results: Rubbish!
Almost three hours of wasted time - I honestly should have recognised the symptoms - problems with PHD (which I very rarely have) and abnormal low subs signal....
Bumma.
Hmmmm
That didn't go well!!
I upped the exposure to 40 x 30s to get better SNR, and "re-adjusted" the grating and slit assembly to get more consistent positioning on the CCD. The results: Rubbish!
Almost three hours of wasted time - I honestly should have recognised the symptoms - problems with PHD (which I very rarely have) and abnormal low subs signal....
Bumma.
Ken
Why use short exposures. If the S/N is low then try 5 min exposures. You will see straight away if the signal is low and not waste as much time.
Here;s this morning's spectrum. Only change is an increase in intensity of the "nebular" lines - HII, OI etc. - that seem to become more pronounced as the magnitude drops - and then fade a little as the thing rebrightens.
I'm trying to get an hour or so timeseries in V of it this morning.
Wall to wall cloud last night - hopefully better tonight.....
Has any else got some data?
Yes I did
Data from last night
V= 4.937
B = 5.028
This is a slight drom in V and less of a drop in B since my last measurement on 5/1/14
The spectra shows an identical relative Ha emission but an increas in the blue continuum.
When I graph the flux calibrated data, there has been a drop in the absolute height of Ha but an increas in the blue continuum. This fits with the reduction of B-V my photometry displays.
Cheers
Terry
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