Hi Jeff,
I don't know if you saw it, but back at post #52 of this thread, I added a pdf file of some emails I got from Robin Leadbetter on how to process a spectra to get an instrument response from an image.
I've added it to this post as well.
If you follow the steps from Robin, it should work fine. I have avoided Vspec errors by doing it his way
The curves / spectra you're collecting look pretty good to me...
cheers
Mark
Yes I saw it, did I pay attention to it -no. I am printing as I type. Thanks Mark.
Quote:
Originally Posted by sheeny
I got a heap of those for a while too, Jeff. I found I got on top of them when I started cropping the spectrum before doing the division. Are you doing that?
Onward and upward!!!
I can smell success in the air!
What about Betelgeuse? Some nice bands in the spectra.
Beta Gem (KO) should show also the K-H bands.
I'm still struggling with the wet and snow/ weather over here!!!!
I'd be interested to see you camera correction curve.
I found when I did a couple for the Canon 350 the curve varied from lens to lens ie the Canon std lens were VERY much different from the Ol' Zuiko lenses....
Jeff,
what about the stars of Crux? Gamma Crux is a M class, Epsilon Crux is K class, the other's B class. Al (Sheeny) did a fantastic shot showing the colours by a de-focussing technique.
Grabbing their spectra would show what the colour differences represent in terms of star temp + chemical makeup...
It's a project I've been meaning to do, but have had to wait till the stars cleared a tree in my yard
What about Betelgeuse? Some nice bands in the spectra.
Beta Gem (KO) should show also the K-H bands.
I'm still struggling with the wet and snow/ weather over here!!!!
I feel I'm about to have a week of foul weather here to.
Quote:
Originally Posted by Heian
what about the stars of Crux? Gamma Crux is a M class, Epsilon Crux is K class, the other's B class. Al (Sheeny) did a fantastic shot showing the colours by a de-focussing technique.
Grabbing their spectra would show what the colour differences represent in terms of star temp + chemical makeup...
The Crux stars does sound like an interesting project. The wind, cloud and spitting rain has put paid to any imaging for the last few days and will continue for a while yet.
What traps could be expected moving the SA further away from the camera to increase dispersion?
I know the spectrum will get dimmer. Is focusing likely to get more difficult or critical? Seeing would also become more critical wouldn't it?
With my current setup, I'm achieving about 11.64A/pixel with the DMK 21. I was think about replacing the lens in my 2x barlow with the SA. That should roughly double the distance between the SA and the CCD... which would work well if I had a DMK 41 I think! Shame about the exchange rate at the moment...
Al,
Would it move the zero image and the spec to far apart? Wouldn't matter if you dont need the zero image in callibration.
I think there must be a point where resolution of the spectrum would not be improved due to the resolution of the grating (lines/").
I moved my grating out to about 35mm and focus is a real issue, but I just get the full spec and zero image in the frame of the ST7.
The other hassle with a more spread out spectrum is interference from background stars. It is tricky to make the spectrum miss the background stars if it is longer.
I wouldn't know at present as I've had cloud since 9th Feb.
Now, if someone knows how to resample different spectra in Vspec, they could grab my image from post #71, adjust it to the same ang/px as your spectra, and we could see if Eta has changed over the last 4 weeks or so!!
Mark/ Jeff
If you can post your .spc files for the Eta Car spectra I'd love to have a go at combining etc.
At the moment I'm scanning some old (like 1880!) spectra to see if they can be converted and used for current comparisons. A little difficult as they were taken with prisms and are "artistic engravings"....
Mark/ Jeff
If you can post your .spc files for the Eta Car spectra I'd love to have a go at combining etc.
At the moment I'm scanning some old (like 1880!) spectra to see if they can be converted and used for current comparisons. A little difficult as they were taken with prisms and are "artistic engravings"....
Done. I have been reluctant as I still have little confidence in my processing. Getting there 'though. The more processed spectra I get from you "experts" the better I can check my processing. I have included my raw data for all to fiddle.
Quote:
Originally Posted by sheeny
OK guys, here's my etacar spectrum to play with.
C8, SA, DMK21AU.AS
Corrected for camera response and normalised.
Al.
Al,
Nice set of spectra. Looking Good.
I have used your calibrated eta to calibrate mine from 20/2/09. The results are below. (Croped to simalar spec range). Hope you don't mind.
I'm happy that our two spec look similar as it seems I'm on the right track.
Al,
Would it move the zero image and the spec to far apart? Wouldn't matter if you dont need the zero image in callibration.
Yes, I realised that would be an issue with a 1/4" sensor. For some stars with distinct lines that wouldn't be a problem, but it's a real limitation for others. When I get a chance I'll do a trial with the DMK on either etacar or Betelgeuse and see how I go.
Quote:
Originally Posted by Terry B
The other hassle with a more spread out spectrum is interference from background stars. It is tricky to make the spectrum miss the background stars if it is longer.
Yeah, especially on dim stars... the long exposures make any background stars brighter...
. I am printing as I type. Thanks Mark.
. Cheers Al.
.
I've got one spectrum from it so far, but it should change quite a bit.
I think! Shame about the exchange rate at the moment...
