My suggestion with the alp Gru image is to perform a 2 line calibration making the first line the star image at 0. Then pick that deep line and call it Ha, Hb or Hg at 6563,4861, 4340.
Then overlay a b5 spectra and see which one lines up with the iter lines the best. You should have absorptions at 6869 for O2 and 7605 for H2O as well.
If the first one doesn't work then call it Hb etc until it seems right. I think it is likely to be Hg at 4340.
I think the results we're seeing are great!
Who would have thought that a bunch of amateurs with a small transmission grating costing less that an eyepiece could do so much.
I think we owe Robin Leadbeater a round of congratulations!! - you've been vindicated.
For those who don't know about him, Robin is a dedicated amateur from NW England who championed the idea of commercialising the Star Analyser grating with Paton-Hawksley. I'm sure if it wasn't for his strenuous efforts the SA would not have become a reality.
Keep up the good work!
There are any number of ways you can use the SA. Check out the performance of any filters you may have! Put a filter in front of the SA, check out the before and after shots, how good is that sky glow filter?...
Measure the spectra of street lights, a backyard bug zapper (not much to see, mainly in the UV)!
Make a holder, put it in front of a std lens on a 350D DSLR and you can measure star spectra with 6 secs non tracked exposures...
I've used a 135mm lens + a 2x teleconverter and achieved approx 2.5 ang/px. Measure the sun spectra by using a reflection of a needle or polished ball bearing...
Jeff,
According to VSpec, Alpha Grus is a B7iv.
If I work on your spectra, the deepest absorption feature appears to be Hbeta, this then gives the series of Hgama, delta, epsilon towards the UV.
The "dip" around the 4500A, between Hbeta/Hgama I think may be a CIII feature(?) This calibration then shows the slight dip of Ha.
What do the others think???
If we agree, it would be good to post a data file with the graph(s); this allows others to run the actual spectra through VSpec.....what do you think??
Jeff,
According to VSpec, Alpha Grus is a B7iv.
If I work on your spectra, the deepest absorption feature appears to be Hbeta,......
If we agree, it would be good to post a data file with the graph(s); this allows others to run the actual spectra through VSpec.....what do you think??
Great idea. I'll have a go.
I have hopefully attached a zipped file containing two data files from VSpec.
One has the uncalibrated spec. the other calibrated with H-Beta as the deep dip in spectra. Both are of Aph Grus.
Others are welcome to view and decipher.
Please let me know what you find.
Theodog,
I tried for a couple of hours to get your spectra to register with a reference B6v spectra; then played with H emission data.....
I wasn't able to get a good match. Even with, what I still think are H beta, H gama etc absorption features I can't seem to get a good scale to give them an acceptable registration.....
Hmmmm. Let me sleep on it.
Anyone else have any success??
Theodog,
I tried for a couple of hours to get your spectra to register with a reference B6v spectra; then played with H emission data.....
I wasn't able to get a good match. Even with, what I still think are H beta, H gama etc absorption features I can't seem to get a good scale to give them an acceptable registration.....
Hmmmm. Let me sleep on it.
Anyone else have any success??
I had a quick play and had the same problem.
May I suggest taking an image of beta Car (Miaplacidus) that is an A2 star that has easier absorption lines to identify. It is the only bright star between the false cross and the SCP so is easy to find. This will then give the A/pixel for your set up and from that the other spectra can be calibrated.
I had a quick try at them as well. Didn't go too well either.
I found a spectra of alpha grus I took some time ago, and it seems the deep absorption line is H beta (4830A if I remember). I do recall sort of giving up trying to process the spectra as it seemed "a bit odd".
I am happy to be proven wrong, but I always thought ccd's couldn't capture UV wavelengths.
Hi All,
Beta Carinae Spec.
Due to poor weather it is only one exposure of 3 seconds, possibly with cloud.
This set-up is different to other s taken, but hopefully is the final set-up.
Looks strange to me.
Dark subtracted but no flat or bias.
12" f5 scope.
Last edited by theodog; 04-02-2009 at 10:05 PM.
Reason: more info
I think I have worked it out. The camera is pretty insensitive in the blue.
See the attached image.
I have attached an image I took of Beta Car with the shutter open. This produced long streaks that highlight the hydrogen absorption lines.
Good analysis Terry!
An extraordinary outcome; 24.1 A/pixel is pretty low resolution even for a SA grating... the distance to the chip could be increased i.e. almost doubled. The severe drop off in the blue-UV is not unusual, but the deep absorption threw me- it just looked to much like a H beta point! Moral of the story? - the info's in the spectra - somewhere!
Looks like Terry's curve has at least been corrected for CCD response and fitted to the Planck curve. ( Tutorial #5)
I've got to ask... Jeff - what was the issue with your first betcar spectra?
Are you doing some pre-processing??
I've got to ask... Jeff - what was the issue with your first betcar spectra?
I just thought I'd have another go at it. When I did the lines seemed much better defined.
Quote:
Originally Posted by Merlin66
Are you doing some pre-processing??
No, no preprocessing except for dark and bias. I'm flat-out getting my head around just displaying the graph with scale.
I agree with the distance to CCD/scale problem 'though. I have my grating practically at the front of the ST in a filter wheel. I will have to move the mirror forward to allow for further seperation due to focus issues.
I do appreciate the help everyone has supplied so far, its been great. At the moment I sit here in 30+ temps trying to better my data.
The shape of the spectral curve indicates that the camera/ CCD responce curve has been calculated and the spectra corrected. Knowing the spectral "shape" of a reference star, you can also correct the curve to match the Planck temperature curve. This is pretty well covered in VSpec's #5 tutorial which you should download. There are 10 tutorials in all.
Hope this helps.
. My last B Car WAS rubbish.
