The nova continues to evolve.
Attached is an image from last night 2/9/13 compared to 30/8/13.
The hydrogen lines are now very strong and continue to strengthen.
I have also attached a comparison of the first image I took on 15/8/13 compared to last night. You would almost think they are different stars as the spectrum has completely changed with the evolution of the nova.
I have expanded the y axis to show the earlier spectra more clearly but the Ha intensity goes up to 45 for last night spectra.
Cheers
My DSLR has been off for repairs, and I'm patiently waiting for the arrival of my L200 (not for a few months as JTW Astronomy is moving, it seems). Then a rather nice tax return cheque arrived, so I managed to pick up an Atik 383 L+.
Last night was the first chance I have had to put the SA100 in the filter wheel. The distance from the sensor was on the small side - only got 17 A/pix. I'll sort something out to get it closer to 8-9. But nice to see the O I lines up in the IR part of the spectrum for the first time.
My new Atik has a fault and has had to go back ... Grrr ... so it's back to the DSLR. Nevertheless, mazing how much detail you can get with the SA100 and a DSLR. Apart from the H lines (hard to miss!) there's He I, NIII, and the forbidden [NII] and [OI] lines.
Here's a spectrum of Nova Del 2013 which I took with a SA100, 10" SCT, and a Cannon EOS 60Da. c.6 A/Pix dispersion, with the grating about 50-60mm in front of the sensor. I was pleased how many emission lines were detectable with this setup - not to mention how easy the spectrum was to annotate with RSpec :-)
Well done!
Good results from what is now a faint object!
(I think the peak at 5000A may be due to the increasing [OIII] @ 5007A - shows well on Terry's LISA spectrum of the same date.)
Well done!
Good results from what is now a faint object!
(I think the peak at 5000A may be due to the increasing [OIII] @ 5007A - shows well on Terry's LISA spectrum of the same date.)
Thanks Ken. I've corrected that annotation. I've been reading Steve Shore's notes on this with great interest, but I'm still in need of a "Nova spectroscopy primer" - a blow-by-blow account of the stages in the evolution of a nova and the spectroscopic features you'd expect to observe. I understand some of the evolution of the Hydrogen lines, the P Cygni profile, and the He flash, but as to why we are seeing OIII not N now, what is supposed to be happening soon with Fe, and so on - I'd love a dummies' guide!
I'm having fun with the SA100. Can't wait for my L200 to roll off the production line in Holland, though :-)
Here's a spectrum of Nova Del 2013 which I took with a SA100, 10" SCT, and a Cannon EOS 60Da. c.6 A/Pix dispersion, with the grating about 50-60mm in front of the sensor. I was pleased how many emission lines were detectable with this setup - not to mention how easy the spectrum was to annotate with RSpec :-)
Very good.
For comparison is my spectra taken on the same night. It has been flux corrected hence the very small numbers on the vertical axis.
The features you describe are present.
Terry
Nice one Terry. I've been finding your spectra of the Nova over on the Astronomical Spectroscopy forum incredibly useful for understanding what's going on.
Forgive a newbie's question but it seems to me that getting all of the continuum from 4000-7200 into one image on a 314+ sensor at R=1200 is really impressive. Other spectra seem to capture far less at that resolution. How do you do it?
One of the reasons I'm asking is because I've been trying to work out which gratings to order with my L200. I want at least one to capture as much of the continuum as possible but think I have to go down to R=300 or even R=150 to do so. Am I missing something?
Jon,
The answer lies in SimSpecV4 (in the astronomical spectroscopy files area + explanatory notes)
It all comes down to collimator/ imaging focal lengths, the l/mm of the grating and the camera pixel/ chip width
Terry uses a LISA which has a 130mm collimator, a fixed 300 l/mm grating and a 88mm imaging lens.
( I use an 80mm collimator/ 300 l/mm/ 50mm imager in the MG80 concept - full spectrum coverage lo res)
EDIT: The spreadsheet for the Spectra-L200 attached - a 150 l/mm grating will give a coverage of 4000- 7000A at R=500.
Nice one Terry. I've been finding your spectra of the Nova over on the Astronomical Spectroscopy forum incredibly useful for understanding what's going on.
Forgive a newbie's question but it seems to me that getting all of the continuum from 4000-7200 into one image on a 314+ sensor at R=1200 is really impressive. Other spectra seem to capture far less at that resolution. How do you do it?
One of the reasons I'm asking is because I've been trying to work out which gratings to order with my L200. I want at least one to capture as much of the continuum as possible but think I have to go down to R=300 or even R=150 to do so. Am I missing something?
Cheers
Jonathan
The R figure is worked out by the processing software based on the FWHM of the neon lines in the calibration spectra as well as pixel size etc. It varies between 800 and 1500 depending on how I do the neon calibration. The actual range on the CCD is determined by the magnification of the spectra and the size of the pixels. I think it is 2.3A/pixel (Im at work so don't have the software infront of me).
For the Atik camera and the LISA this allows a spectra to range from 3800-7300 across the frame. It was much larger when I used my SBIG ST8 as it has a bigger chip but lower resolution due to it having bigger pixels.
The L200 is a different design and suffers more with field curvature making the ends of the spectra out of focus. This limits the practical width of the spectra. I think the L200 is better for medium resolution spectra and not to worry about trying to use it for full width spectra. Regularly changing the grating would be a pest to do and a but risky due to possible damage to the gratings. Drop it once and it is useless.
Jon,
Terry has made some good points.
With the Littrow design (both the Spectra-L200 and LhiresIII) the collimating/ imaging achromat is a longer focal length (200mm) and has a "sweet spot" of about 10mm diameter.
In other designs - MG80/ FC120/ Classical etc you can alter the collimator ( even use a mirror!) and use photographic quality imaging lenses which give better wide field coverage.
The latest design of the Spectra-L200 only requires loosening three thumbscrews to remove and replace the grating assembly, but as Terry says, if you drop it you're toast.
Jon,
Terry has made some good points.
With the Littrow design (both the Spectra-L200 and LhiresIII) the collimating/ imaging achromat is a longer focal length (200mm) and has a "sweet spot" of about 10mm diameter.
In other designs - MG80/ FC120/ Classical etc you can alter the collimator ( even use a mirror!) and use photographic quality imaging lenses which give better wide field coverage.
Good - I think I'm following all that, which means my understanding of spectroscope design is improving.
Quote:
Originally Posted by Merlin66
The latest design of the Spectra-L200 only requires loosening three thumbscrews to remove and replace the grating assembly, but as Terry says, if you drop it you're toast.
That I didn't know. I thought the exchangeable gratings were a interesting feature of the L200. But I guess that's just another of a fairly long list of astronomical equipment in the "drop it and you're toast" category. I'm not thinking of playing basketball with my CCD camera, my focal reducer, my eyepieces or my laptop, either
But seriously, I wasn't aware that gratings were particularly more sensitive than other optical components. Good to know.
I wonder if there's any news on how the L200 run is going at JTW Astronomy?
