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Hi Janet,
Valerie Desnoux has a video on how to calculate the instrument response and use it to correct another spectrum on the Vspec website here
and the tutorial here covers the same ground though it uses an earlier version of vspec
There are many other tutorials on the same page
You can also find information about the functions used in the help document (page 90 under continuum)
Cheers
Robin
----- Original Message -----
From: janet simpson
To: staranalyser
Sent: Thursday, July 16, 2009 11:14 PM
Subject: RE: [staranalyser] Re: gamma Cas spectra
I have downloaded the latest VSpec, and have divided Altair intensity by library A7V (in Files, User folders, Janet Simpson). I have forgotten how to smooth it!
Janet
To: staranalyser@yahoogroups.com
From: robin@...
Date: Tue, 14 Jul 2009 15:42:49 +0100
Subject: Re: [staranalyser] Re: gamma Cas spectra [1 Attachment]
[Attachment(s) from Robin Leadbeater included below]
--
"Very funny Scotty... now beam down our clothes!"
http://tech.groups.yahoo.com/group/astronomical_spectroscopy/?yguid=322612425
Hi Ken/Janet,
I have not used my 350D much for spectroscopy but I have not noticed that with my Canon EF zoom lenses ( pre digital, early 90's I think but still with a plastic barrel). Here are a couple of examples. I checked back and Janet's results back in Oct 2007 also showed a red bias so perhaps I am the odd one out. I will have to try with the lens which came with the camera. I guess the main thing though is repeatability for a given setup. Incidentally, rereading Buils analysis of the effect of atmospheric extinction, the effect appears larger than I anticipated across the full spectrum which may mean a rethink in terms of the best way to correct low resolution spectra for instrument response and
atmospheric effects, particularly if the standard star and target are at significantly different elevations.
Robin
----- Original Message -----
From: Ken Harrison
Sent: Tuesday, July 14, 2009 9:31 AM
Subject: Re: [staranalyser] Re: gamma Cas spectra
Robin/ Janet
The camera responce curve looks very similar to the one I found last year ( Remember the discussion, Robin?) for a combination of the Std Canon lenses and the 350D.
Janet: which type of lens were you using? can I assume a "plastic" Canon lens, if so then the responce curve - Hii red, low UV looks typical. I did similar exposures with an old Zuiko lens with the 350D and got a completely different camera/lens responce.
My 2c
On 14/07/2009, Robin Leadbeater <robin@leadbeaterhome.fsnet.co.uk > wrote:
[Attachment(s) from Robin Leadbeater included below]
----- Original Message -----From: janet simpsonTo: staranalyserSent: Monday, July 13, 2009 4:03 PMSubject: RE: [staranalyser] Re: gamma Cas spectra [2 Attachments]
> The version of VSpec which I use is 3.3, from the Sky at Night CD.Ah.. that might be the problem. There have been several revisions to VSpec and many bug fixes since then. I suggest doing a clean install of the current version (3.6) from the Visual Spec website. Hopefully this will solve some of your problems.Your gamma Cas spectrum looks fine. It processed OK. I have attached an image showing the results of the processing steps (I cheated a bit and used the fact that gamma Cas is known to be a B0v star to calculate an instrument response)The calculated instrument response is interesting. It looks like the red channel is set too high on your camera. Are you using a fixed daylight white balance setting? This should give a more balanced response. Also check that you have selected the right model of camera in IRIS if that is the program you are using to convert from colour to greyscale.My broadband is down again but when it is back up I will look into your membership settings to see if I can figure out what is going wrong.CheersRobin
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