Welcome to iraf.net Thursday, March 28 2024 @ 09:55 PM GMT


 Forum Index > Help Desk > Applications New Topic Post Reply
 Deleting points in the wavelength calibration step
   
cosmologist
 09/12/2011 04:42AM (Read 2586 times)  
++++-
Regular Member

Status: offline


Registered: 03/30/2009
Posts: 117
In the data reduction manuals when talking about the wavelength calibration step, it is mentioned that when doing the fit, if some points are really far away from the horizontal line one should simply delete them... but I don't understand what that means in terms of the reduction and fitting, how can we delete points from the fitting? Isn't that kind of "cheating"? When I read it in the manual I tried to understand it but it doesn't explain it. That way I can delete so many points to get a perfect fit but how "honest" my solution will be? Do you know what I mean?Thanks
Smile

 
Profile Email
 Quote
favilac
 09/12/2011 04:42AM  
+----
Newbie

Status: offline


Registered: 12/16/2005
Posts: 10
Having been recently in that position, I can tell you that we must remember that the whole data chain aquisition is not perfect. From cosmic rays to hardware issues, sometimes you get data points that are not related to the object. This type of points are usually really far from the ideal line fit, so it's easy to spot them. To confirm, you can display the spectra in DS9 and see if there is a hotspot in that place.Another problem that may arise when fitting spectra, is the case of really close double lines. When this happens sometimes the IRAF routines are not able to assign the wavelenght in an accurate way, so its better to not include them in the fit.

 
Profile Email Website
 Quote
   
Content generated in: 0.06 seconds
New Topic Post Reply

Normal Topic Normal Topic
Sticky Topic Sticky Topic
Locked Topic Locked Topic
New Post New Post
Sticky Topic W/ New Post Sticky Topic W/ New Post
Locked Topic W/ New Post Locked Topic W/ New Post
View Anonymous Posts 
Anonymous users can post 
Filtered HTML Allowed 
Censored Content 
dog allergies remedies cialis 20 mg chilblain remedies


Privacy Policy
Terms of Use

User Functions

Login