Jeff,
What was the star being measured?
4.2A/pixel - That's interesting
I was getting 6.58A/pixel with the Baader 207lpm grating about 25mm infront of the T ring; about 60mm from the Canon 300 CDD.
Jeff,
What was the star being measured?
4.2A/pixel - That's interesting
I was getting 6.58A/pixel with the Baader 207lpm grating about 25mm infront of the T ring; about 60mm from the Canon 300 CDD.
The star is etacar. The grating, 300l/mm, is possibly 50-60mm from the CCD.
I used both Ha and Hb for a calibration with 2 lines. The images included are full width frames from the ST7.
As these were taken through the 4" the star images were large at focus.
I could not move to capture more of the spectra as the star would move off the gtating.
I also imaged betcru and used similar lines from an alpori for line calibration and obtained similar figures (+/- 0.1l/p). I think the SA is a better system.
Last edited by theodog; 08-03-2009 at 08:18 AM.
Reason: Image added
Hi everybody, I've been following this thread and others very intently because I'm becoming very interested in practical amateur spectroscopy.
However there's an aspect which is confusing me, and that's the ionic notation which is often used by some people.
A very long time ago, I studied chemistry - A VERY long time ago, so my memory is not to be relied upon!
But as I recall, 'I' (as in HI, OI, etc) signified the Unionised or Ground state, II signifies the (singly) ionized state, III signifies the doubly ionized state, IV the triply ionized state, and so on.
The '[]' (as in [OIII]) indicated a forbidden transition, commonly seen in low density gaseous nebulae, etc.
Yet I've seen, say, the 'II' notation (whether forbidden or not) referred to here and elsewhere as double ionization, rather than single, and 'III' as triple ionization.
Am I missing something, or is the latter use of the notation erroneous?
Using II as doubly ionised (of anything) is erroneous. Doubly ionised gases are denoted as such.."III". Same applies for all other ionisation states...IV (triply ionised), II (singly ionised) etc.
Using II as doubly ionised (of anything) is erroneous. Doubly ionised gases are denoted as such.."III". Same applies for all other ionisation states...IV (triply ionised), II (singly ionised) etc.
Okay, that's reassuring. Ironically, one of your posts caused some of my confusion and uncertainty:
"That's what I would expect.....FeII being the doubly ionised form, occurs at much higher temps than FeI and in the bluer/UV region of the spectrum."
Yet I've seen, say, the 'II' notation (whether forbidden or not) referred to here and elsewhere as double ionization, rather than single, and 'III' as triple ionization.
Zaps.
Where have you read this in IIS Spectroscopy? I see it now -no further comment from me on checking posts.
As for elsewhere -that's their mistake.
single = II
double = III
triple = IV
Yes forbidden lines are possible in highly rarified gas.
I like the concept!
Another idea that came to mind while looking at your images...
What if we had a diaphragm say about 5mm diameter over the grating, centred on the star under observation. The OOF star size obviously will depend on the focal ratio and the distance between the grating and the CCD.
This would stop any of the nearby stars showing up in the spectra????
Yes-No???
Ken,
I had thought of something like that myself. An adjustable slit in the system will basically reduce the light source, and I'd always thought a mask would do a similar job, but it would be easier to locate and not worry about the focus issue.
It would be worth some experiments if nothing else...
I thought about a slit also but maybe just a straight mask on the SA. You only need to block the stars on the side that the spectrum is projected.
Maybe a piece of aluminium foil on the SA and then position the target star just of the edge of the foil.
There is an archive of old spectra of eta carinae. I haven't done it yet but if we can open these in VSpec then there's a ready made source of spectra to practice with and learn our way around VSpec.
Al.
PS. Guys... might not be as simple as I thought. The spectra fits files are .tar files. It sounds like you need a program called tar to uncompress... I'll see what I can find...
Last edited by sheeny; 09-03-2009 at 08:28 PM.
Reason: Problem uncompressing fits files
There is an archive of old spectra of eta carinae. I haven't done it yet but if we can open these in VSpec then there's a ready made source of spectra to practice with and learn our way around VSpec.
Al.
PS. Guys... might not be as simple as I thought. The spectra fits files are .tar files. It sounds like you need a program called tar to uncompress... I'll see what I can find...
tar files are just linux compressed files. There should be a windows program to untar them otherwise it is very easy to do in linux.
The knife edge idea would work.... I rather like the diaphragm idea though..It effectively hides everything other than the star image going through the SA. You can quickly estimate the size of the hole required from the distance between the grating and the CCD and the focal ratio.
Think about it; no "extra" star images to contaminate the spectra and no additional spectra of other stars.........
The knife edge idea would work.... I rather like the diaphragm idea though..It effectively hides everything other than the star image going through the SA. You can quickly estimate the size of the hole required from the distance between the grating and the CCD and the focal ratio.
Think about it; no "extra" star images to contaminate the spectra and no additional spectra of other stars.........
I'm looking into 2 possibilities.
When I get hold of some 2" aluminium bar I will make a 2" "mask into which the 1 1/4 SA will slide into, similar to a 2" adapter, with a small hole to allow a small field through.
Also I have come across an old microscope slide mover that is used to move microscope slides around the stage. I am looking into how this may be used to move an adjustable slit around under the SA, major engineering.
I'm looking into 2 possibilities.
When I get hold of some 2" aluminium bar I will make a 2" "mask into which the 1 1/4 SA will slide into, similar to a 2" adapter, with a small hole to allow a small field through.
You don't want to hole in the centre though do you? You want the star image near the edge of the FOV of your camera, so don't forget to offset the hole by a smidgin less than half the width of your camera sensor corrected for the focal ratio of your scope.
You don't want to hole in the centre though do you? You want the star image near the edge of the FOV of your camera, so don't forget to offset the hole by a smidgin less than half the width of your camera sensor corrected for the focal ratio of your scope.
Al.
Yep, working through these issues, if only things were simple. Terry's idea of aluminium foil would help to develop measurements.
Working through the micro-slide idea, maybe easier to make a full spectroscope.
You can open .tar and .gz files in Windows with WinZip, so long as you have it configured correctly. Otherwise you can use 7-zip, gzip, WinAce, WinRAR, or TAR for Windows, plus a few others.
Working through the micro-slide idea, maybe easier to make a full spectroscope.
Glad it's not just me that's having trouble opening the .tar files.
Quote:
Originally Posted by Zaps
You can open .tar and .gz files in Windows with WinZip, so long as you have it configured correctly. Otherwise you can use 7-zip, gzip, WinAce, WinRAR, or TAR for Windows, plus a few others.
I didn't think there was any configuration to do in Winzip... I've just had another look and can't see anything obviously useful. If you can be more specific, that would be appreciated!
I keep getting an "invalid archive directory" error., which may be the result of:
The archive file does not exist or is in use by another program.
The specified folder does not exist.
The file is not an archive.
The archive has been damaged or corrupted.
There were disk errors or insufficient memory while reading the archive.
The archive contains invalid or illegal filenames.
If anyone has success opening the .tar files of the spectra I'd appreciate some tips on what you did....
I see it now -no further comment from me on checking posts.
