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  • alunhalsey
    Hi, Have uploaded a few results I got from a session with the C9.25 and Lhires III on the 21st Sept comprising of Capella,Beta Aurigae and Epsilon Aurigae.
    Message 1 of 17 , Sep 22, 2017

      Hi,


       Have uploaded a few results I got from a session with the C9.25 and Lhires III on the 21st Sept comprising of Capella,Beta Aurigae and Epsilon Aurigae. Single images,no darks nor flats subtracted and no instrument response correction,used the internal argon/neon lamp to calibrate the spectra.


       Capella...


      https://uk.groups.yahoo.com/neo/groups/astrobodger/photos/photostream/lightbox/1043469235?orderBy=mtime&sortOrder=desc&photoFilter=ALL#zax/1043469235


      Beta Aurigae...


      https://uk.groups.yahoo.com/neo/groups/astrobodger/photos/photostream/lightbox/1506918895?orderBy=mtime&sortOrder=desc&photoFilter=ALL#zax/1506918895


       Epsilon Aurigae....


      https://uk.groups.yahoo.com/neo/groups/astrobodger/photos/photostream/lightbox/1875553167?orderBy=mtime&sortOrder=desc&photoFilter=ALL#zax/1875553167


        Regards


          Alun


    • alunhalsey
      Had another session with my Lhires III and C9.25 last night using the 2400l/mm grating and 35um slit. A couple of stars revisited,28 Tau and Epsilon Aurigae,no
      Message 2 of 17 , Oct 16, 2017

        Had another session with my Lhires III and C9.25 last night using the 2400l/mm grating and 35um slit. A couple of stars revisited,28 Tau and Epsilon Aurigae,no flats darks nor instrument response calibration were used,

        28 Tau is a single image of 300 seconds and Epsilon Aurigae,again a single image was 120sec exposure both taken in the Ha region and used the internal neon lamp for calibration (three lines with 6506 just in the frame).


        Epsilon Aurigae....


           https://uk.groups.yahoo.com/neo/groups/astrobodger/photos/albums/2100753696/lightbox/1986844388?orderBy=ordinal&sortOrder=asc&photoFilter=ALL#zax/1986844388


        28 Tau......


           https://uk.groups.yahoo.com/neo/groups/astrobodger/photos/albums/2100753696/lightbox/673811041?orderBy=ordinal&sortOrder=asc&photoFilter=ALL#zax/673811041


          Regards


              Alun

         

      • John Paraskeva
        Hi Alun, Looks good, thanks for sharing. Knew it wouldn t take long to succumb to the 2400 line grating! I see you used the 35 micron slit. I guess the images
        Message 3 of 17 , Oct 16, 2017
          Hi Alun,

          Looks good, thanks for sharing. Knew it wouldn't take long to succumb to the 2400 line grating!

          I see you used the 35 micron slit. I guess the images would be relatively faint with the 2400 grating with a smaller slit. I had a go with my 3D spectrometer and struggled with the #1 slit, (about 20 microns I think).


          cheers
          John



          From: "ALUN@... [astrobodger]" <astrobodger@...>
          To: astrobodger@...
          Sent: Monday, 16 October 2017, 16:32
          Subject: [astrobodger] More results

           
          Had another session with my Lhires III and C9.25 last night using the 2400l/mm grating and 35um slit. A couple of stars revisited,28 Tau and Epsilon Aurigae,no flats darks nor instrument response calibration were used,
          28 Tau is a single image of 300 seconds and Epsilon Aurigae,again a single image was 120sec exposure both taken in the Ha region and used the internal neon lamp for calibration (three lines with 6506 just in the frame).

          Epsilon Aurigae....


          28 Tau......


            Regards

                Alun
           


        • alunhalsey
          Hi John, Thank you,I used the 35um slit as there was a lot of thin cloud drifting in and out otherwise I would have had a go with the 23um. Was hoping for
          Message 4 of 17 , Oct 16, 2017
            Hi John,

                 Thank you,I used the 35um slit as there was a lot of thin cloud drifting in and out otherwise I would have had a go with the 23um. Was hoping for another session tonight but the wind played havoc trying to keep the star on the slit so gave up! :(

                Regards

                  Alun
          • andyjwilson_uk
            Those are nice results Alun. Even just looking at H-alpha there are sufficient interesting targets and monitoring programs to keep us busy indefinitely.
            Message 5 of 17 , Oct 17, 2017
              Those are nice results Alun. Even just looking at H-alpha there are sufficient interesting targets and monitoring programs to keep us busy indefinitely.
              Cheers,
              Andy
            • alunhalsey
              Hi Andy, Thank you,once I get sorted with adding instrument response calibration I will begin adding more to your BAA spectroscopy database :) Would also help
              Message 6 of 17 , Oct 17, 2017
                Hi Andy,

                    Thank you,once I get sorted with adding instrument response calibration I will begin adding more to your BAA spectroscopy database :)  Would also help if this continual cloud cover would leave us alone to get more data! 

                    Regards

                       Alun
              • andyjwilson_uk
                Hi Alun, Once you get the hang of instrument response I think you will find it is quite straight forward. The initial learning step to work out what you are
                Message 7 of 17 , Oct 18, 2017
                  Hi Alun,

                  Once you get the hang of instrument response I think you will find it is quite straight forward. The initial learning step to work out what you are doing and how can be a little daunting, but it is not that bad.

                  It is also much easier at higher resolution. At low resolution you need to be careful to match the altitude of your target, but at high resolution you almost don't need to worry about this. Basically because you are only looking at a very small wavelength range, which does not vary too significantly with altitude (air mass).

                  Cheers,
                  Andy
                • alunhalsey
                  Hi Andy, Thank you for the tips,in regards instrument response which reference library works with Hi res spectra in BASS? I know the ISIS software uses the
                  Message 8 of 17 , Oct 18, 2017
                    Hi Andy,

                        Thank you for the tips,in regards instrument response which reference library works with Hi res spectra in BASS? I know the ISIS software uses the ELODIE files but don't really get on with the software. 

                        Regards

                           Alun
                  • Ken Harrison
                    I d do some comparison tests with both the Miles and Pickles library data. The Miles results should be OK. On 19 October 2017 at 07:46,
                    Message 9 of 17 , Oct 18, 2017
                      I'd do some comparison tests with both the Miles and Pickles library data. The Miles results should be OK.


                      On 19 October 2017 at 07:46, ALUN@... [astrobodger] <astrobodger@...> wrote:
                       

                      Hi Andy,


                          Thank you for the tips,in regards instrument response which reference library works with Hi res spectra in BASS? I know the ISIS software uses the ELODIE files but don't really get on with the software. 

                          Regards

                             Alun




                      --
                      "Astronomical Spectroscopy - The Final Frontier" - to boldly go where few amateurs have gone before....

                    • alunhalsey
                      Thank you Ken,I ll experiment and upload my results :) Regards Alun
                      Message 10 of 17 , Oct 18, 2017
                        Thank you Ken,I'll experiment and upload my results :)

                             Regards

                                Alun
                      • andyjwilson_uk
                        Hi Alun, To get the most science out of spectra I d rank the calibrations in the following order. 1 - Bias, needed to remove the offset in the camera readout 2
                        Message 11 of 17 , Oct 19, 2017
                          Hi Alun,

                          To get the most science out of spectra I'd rank the calibrations in the following order.

                          1 - Bias, needed to remove the offset in the camera readout
                          2 - Dark, though there have been discussions around whether with some modern cooled low noise ccds hot pixel removal does a sufficiently good job.
                          3 - Flat, needed to remove pixel to pixel variations as well as bulk variations like dust doughnuts
                          4 - Instrument response, corrects the shape of the continuum
                          5 - Flux calibration - Don't worry about this, I just include it for completeness

                          So I'd suggest working on getting good bias, dark and flat calibrations before working on instrument response.

                          To get a good instrument response, then ideally you want a professional response corrected spectrum for the star you are observe to create your instrument response curve. You can sometimes get away with using the Pickles library of spectra by spectral types. However, each star will have its own peculiarities, such as how much dust lies between us and the star causing extinction which changes the profile shape. So the Miles or ELODIE databases of actual stellar spectra are much better. You should also be able to load the ELODIE spectra from the ISIS database into BASS.

                          The miles spectra are good, but I don't remember if I ever used them at high resolution. From memory I think they may be around R~2000 which could be problematic for LHIRES III in high resolution mode. Though worth a try.

                          The ELODIE spectra are sufficiently high resolution to be good for LHIRES III. Also you just need to observe a bright star, ideally with a simple spectrum like an A or B type star. Vega is often used for this purpose, though I know there were doubts raised about the quality of the original ELODIE spectrum used in the ISIS database. I think there are better ones available now.

                          Best wishes,
                          Andy
                        • alunhalsey
                          Hi Andy, Once again thank you for your advice,got to get out of the habit of not using dark,flat and bias frames,something John also reminded me to do when I
                          Message 12 of 17 , Oct 19, 2017
                            Hi Andy,

                               Once again thank you for your advice,got to get out of the habit of not using dark,flat and bias frames,something John also reminded me to do when I worked on my ALPY spectra......Do I listen?? 

                              Managed to load the ISIS database into BASS and had a go at instrument response correction of my Vega spectra using the ELODIE profile,which looks to have a lot of Telluric lines,did read in a thread (in Spectro-Aras forum I think) that these need to be removed before use (another bit of the learning curve). Anyhow I used the profile as is and came up with a reasonable fit,result posted to my folder in the photos section....


                               Regards

                                  Alun


                                

                              

                          • andyjwilson_uk
                            Hi Alun, For good quality data, the bias, dark and flats are essential. You won t always notice much of a difference, but it is all about knowing that a bump
                            Message 13 of 17 , Oct 19, 2017
                              Hi Alun,

                              For good quality data, the bias, dark and flats are essential. You won't always notice much of a difference, but it is all about knowing that a bump or peak is genuine, and if measured will give a robust value without deviations introduced by your equipment.

                              That is looking good. There is a bit of deviation from the Vega spectrum, but that is an excellent start. With a really good response correction you will find an almost perfect fit to the star you use to work out the correction.

                              With the telluric lines you do not want them to interfere with fitting the atmospheric/instrument response curve. So in ISIS you can remove them from your spectrum and fit an ELODIE spectrum which already has them removed (sometimes there are 2 versions of the standard spectrum, with and without the telluric lines). BASS also has a tool which can allow you to remove them. Noting that telluric removal is never perfect. Also if you can fit the response curve avoiding the telluric lines then you may be able to get a good response correction curve without going through telluric removal (though I've not tried this).

                              The other important point to note is you would expect an excellent fit for the star that you used to work out your response correction curve, in this case Vega. However, this end result is not truly meaningful for Vega since you are matching your observation to someone else's observation. Where the power really comes in is when you apply this response curve for other stars and targets.

                              Cheers,
                              Andy
                            • John Paraskeva
                              Alun - as Andy says, great start. It can be difficult to prepare a response correction when the continuum has some noise. In this case I it easier to create a
                              Message 14 of 17 , Oct 19, 2017
                                Alun - as Andy says, great start. It can be difficult to prepare a response correction when the continuum has some noise. In this case I it easier to create a response on a profile that has had a low pass filter applied can help. See the filter tab of the Resample screen.

                                Andy - lots of great tips. Thanks for sharing.

                                cheers
                                John



                                From: "barnards.star12@... [astrobodger]" <astrobodger@...>
                                To: astrobodger@...
                                Sent: Thursday, 19 October 2017, 12:00
                                Subject: [astrobodger] Re:: Instrument Response and Other Calibrations

                                 
                                Hi Alun,

                                For good quality data, the bias, dark and flats are essential. You won't always notice much of a difference, but it is all about knowing that a bump or peak is genuine, and if measured will give a robust value without deviations introduced by your equipment.

                                That is looking good. There is a bit of deviation from the Vega spectrum, but that is an excellent start. With a really good response correction you will find an almost perfect fit to the star you use to work out the correction.

                                With the telluric lines you do not want them to interfere with fitting the atmospheric/instrument response curve. So in ISIS you can remove them from your spectrum and fit an ELODIE spectrum which already has them removed (sometimes there are 2 versions of the standard spectrum, with and without the telluric lines). BASS also has a tool which can allow you to remove them. Noting that telluric removal is never perfect. Also if you can fit the response curve avoiding the telluric lines then you may be able to get a good response correction curve without going through telluric removal (though I've not tried this).

                                The other important point to note is you would expect an excellent fit for the star that you used to work out your response correction curve, in this case Vega. However, this end result is not truly meaningful for Vega since you are matching your observation to someone else's observation. Where the power really comes in is when you apply this response curve for other stars and targets.

                                Cheers,
                                Andy


                              • alunhalsey
                                Hi Andy,John Thank you both for the great tips,plenty food for thought. Will collect a set of dark,bias and flat frames using the internal lamp unit in the
                                Message 15 of 17 , Oct 19, 2017
                                  Hi Andy,John

                                        Thank you both for the great tips,plenty food for thought. Will collect a set of dark,bias and flat frames using the internal lamp unit in the Lhires tomorrow (camera hasn't moved so flats should match up with the lights just for playing with) and using the Vega profile,and a few others I've collected,will concentrate on experimenting with instrument response and filter settings :)  No doubt I will have more questions! :)

                                         Regards

                                           Alun
                                • Ken Harrison
                                  Alun, Could you drop me an email. kenm.harrison@gmail.com (I can t seem to get through to your email address) Ken On 20 October 2017 at 09:21,
                                  Message 16 of 17 , Oct 19, 2017
                                    Alun,
                                    Could you drop me an email.
                                    (I can't seem to get through to your email address)
                                    Ken


                                    On 20 October 2017 at 09:21, ALUN@... [astrobodger] <astrobodger@...> wrote:
                                     

                                    Hi Andy,John


                                          Thank you both for the great tips,plenty food for thought. Will collect a set of dark,bias and flat frames using the internal lamp unit in the Lhires tomorrow (camera hasn't moved so flats should match up with the lights just for playing with) and using the Vega profile,and a few others I've collected,will concentrate on experimenting with instrument response and filter settings :)  No doubt I will have more questions! :)

                                           Regards

                                             Alun




                                    --
                                    "Astronomical Spectroscopy - The Final Frontier" - to boldly go where few amateurs have gone before....

                                  • alunhalsey
                                    Hi Ken, Email sent :) Regards Alun
                                    Message 17 of 17 , Oct 20, 2017
                                      Hi Ken,

                                           Email sent :)

                                          Regards

                                           Alun
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