I have not been able to use my L200 spectrograph due to a mechanical failure along with very crappy weather.
I have now fixed the spectrograph and installed the neon reference lamp. This makes measurement of the lines much easier.
I took 2 sets of exposures of eta Car a few nights ago. I calibrated the spectrum using about 10 lines of neon emission lines.
The result is interesting with very obvious emission lines.
I processed the 2 different areas of the spectrum and joined them together to create the spectrum below.
The very strong H alpha line is obvious but I'm not sure what the other 2 strong lines are.
If you look at the raw spectrum there are lots of fainit lines above and below the star spectrum. These are from the surrounding nebula.
If I ever get a clear night again I will have another go and use longer exposures. The total for this spectrum was 4x5 mins for the green end and 5x1 min for the red end.
Last edited by Terry B; 31-03-2011 at 11:11 PM.
Reason: typo
Hi Terry,
I am so excited you are doing this on E.Carinae!!!
I regularly search the web for updates on this star, and just so exciting that someone here on the forum is keeping track of it.
Keep up the good work, it is appreciated.
I'm glad you're back in action!
Question:
is the 3A red shift a reasonable figure for eta car???
Will be interesting to compare your data gong forward.
I'm glad you're back in action!
Question:
is the 3A red shift a reasonable figure for eta car???
Will be interesting to compare your data gong forward.
I'm not sure about the redshift. I searched for other spectra of eta car but only found UV and IR areas. I will have to read some more papers.
Terry,
I'm assuming the section of the spctrum image is around the 5869 region? Interesting that you've recorded some of the nebula spectrum with such a short exposure and long slit.
If we can identify some of these lines -maybe they can be used for calibration??
I used the join function in vspec to blend the 2 images.
The calibration for both image sets was 5 sec exposures x 5 stacked of the neon spectrum so I don't need to use any star lines for calibration. I used all the neon lines to calibrate but it is pretty linear anyway.
The only problem is that the silt seems to be tilted. The zero order slit is vertical but it becomes progressively more tilted as you get into the IR. It has a 6deg tilt in the IR range. The tilt in the spectrum however is the oposite way of only about 1 deg. I opted not to correct the tilt and just used the same crop of the calibration lines and the image lines.
I was also amazed that there were lines from the nebula. I thought that they might be ghost images left over from the neon lines but they don't line up at all with the neon lines. I will try again when the cloud goes away.
The Littrow spectroscope has two "distortions" - Slant and tilt.
The spectrum should always be set up horizontal.
When this is done the lines will appear tilted in the spectrum by about 4 degrees (caused by the pick off mirror positioning in the Littrow) and is very constant.
The slant of the spectrum band across the CCD chip does change with increasing wavelength.
When the 600 l/mm grating is used in the 2nd order, for instance, the spectrum may appear well down in the CCD frame.
The testing I'm doing with the 1800 l/mm grating show it will be difficult to get the zero order and the far IR on small chips! (without changing the tilt of the grating holder!!) IRIS can correct for both.
(I'm assuming the image you published was just the 5000A section...)
Another attempt.
I took this spectrum last night between the clouds from ~2300hrs. The clouds rolled in after I had taken exposures of 2 regions of the spectrum so I could not take any images of a known star to calibrate the instrument response.
The exposures were 300 sec x 5 combined with Iris using the composit command.
the 2 regions were then joined in Vspec after calibrating using about 20 neon lines.
This time there are some obvious He lines as well as the Ha line.
I'm still not sure what the lines are at 5753A and 5873A.
I've just seen this thread and can confirm the [NeII] and HeI lines at the left of your spectra. I've been monitoring both these lines for the last few months (at around R=18,000) as part of an RV study of the eta Car ejecta "cloud". The Sodium D1 and D2 ISM lines are also present, just to the right of the HeI line, but don't really show up at your resolution.
I've just seen this thread and can confirm the [NeII] and HeI lines at the left of your spectra. I've been monitoring both these lines for the last few months (at around R=18,000) as part of an RV study of the eta Car ejecta "cloud". The Sodium D1 and D2 ISM lines are also present, just to the right of the HeI line, but don't really show up at your resolution.
Bernard
Thanks Bernard. Good to see I found the correct lines.
How are you monitoring the star?
My spectrum was only taken with a 200mm scope so getting a good S/N isn't very easy.
I monitor that particular window with my Lhires III+ST-8XE+C8 using a 2400 l/mm grating and a 19um slit.
Getting a decent SNR on a bright object should not be a real problem if (a) you make a long exposure and (b) you guide/autoguide well. Attached is an image of a fairly recent spectra made with my 200mm (C8) scope with a total exposure time of 50 min. I'm not allowed to show a spectra of that same region made with a +3m professional telescope but I can assure you the pro resolution and SNR was not that much better.
