Last weekend, I did some initial probing into amateur visual and imaging spectroscopy using the Ealing on Arcturus with a Rainbow Optics grating. Preliminary results and preliminary setups for visual and spectrograph imaging are shown in the following Utah Astro Gallery pics: I. Spectrum imaging: Arcturus Spectrograph - 1st attempt - image http://gallery.utahastronomy.com/main.php?g2_itemId=11453 Arcturus Spectrograph - raw Vspec plot http://gallery.utahastronomy.com/main.php?g2_itemId=11455 Ealing Spectrograph imaging setup - Rainbow Optics grating with targeting http://gallery.utahastronomy.com/main.php?g2_itemId=11445 Ealing Spectrograph - Rainbow Optics, extension tubes and Meade DSI http://gallery.utahastronomy.com/main.php?g2_itemId=11447 The imaging setup will be changed in future versions to aid in spectrograph calibration by the filter method. A filter wheel needs to be added in front of the flip mirror to accomodate a set of Johnson BVRI cut off filters. This allows taking a picture of the spectrum several times, using the JOhnson cut-off filters to mark the spectrograph with calibration lines. Buhl's filter method - order cut-off calibration http://astrosurf.com/buil/us/loris/loris.htm Another option that I am considering for light lamp calibration is simply a halogen hiker's headlamp flashed down the targeting e.p. tube. I understand that a halogen desk lamp also can be used on down the telescope down. Any experience comments on using an inexpensive halogen desklamp for making a calibration spectrum would be appreciated. How do you image both the faint target's spectrum and the desklamp spectrum in the same exposure? II. Visual spectrum observing: Ealing Visual Spectrometry - Rainbow Optics setup with parafocal targeting http://gallery.utahastronomy.com/main.php?g2_itemId=11449 Ealing Visual Spectrometry - Rainbow Optics grating and extension tubes http://gallery.utahastronomy.com/main.php?g2_itemId=11451 The visual spectral observing setup works but left me scratching my head about what visual spectrometery was all about. After rereading my Rainbow Optics Grating manual, I noticed that I missed a small comment that for visual observing, the grating had to be slightly defocused _infocus_ to bring out of the spectral lines visually. Otherwise, only the most prominent broad lines can be seen with no detail. Depending the results of the second visual observing test with infocus defocusing, I'll probably also use a lower focal lenght ep. A 20mm ep would only allow observing part of the spectrum at a time. I'll probably go to 32mm ep. The Forum for Amateur AstroSpectroscopy has a good set of recommendations for a beginning observing list for amateur visual spectroscopy with notes on what the most prominent visual lines are in each spectral class. FAAS Visual Observing Guide to Spectra http://users.erols.com/njastro/faas/pages/starcat.htm FAAS Spectroscopic Grating Visual Observing FOrm http://users.erols.com/njastro/faas/pages/workgrat.htm FAAS Spectroscopic Certification page with visual observing spectral forms http://users.erols.com/njastro/faas/pages/winter-g.htm FAAS website http://users.erols.com/njastro/faas/ III. Lessons learned As an initial imaging spectroscopy session, the weekend was more of a lesson learned experience than one of results. Part of the general outline of the Arcturus spectrum was imaged but could not be accurately calibrated and normalized. Some goofs, gafs and lessons learned included: 1) The Meade DSI was left with the autocontrast mode on. Autocontrast must be off. This meant that the multiple spectrum images (see above http://gallery.utahastronomy.com/main.php?g2_itemId=11453 ) could not be calibrated to each other. The spectrum turned into the graph above covers the green through red visual region. 2) To make a drift spectrum image, the grating has to be fixed to project a N-S spectrum before the session begins. Drift spectrum images help make the spectra lines easier to see. After the grating's position is fixed, the grating cannot be moved. During setup, a reticule is placed where the camera appears in the spectral imaging setup. A star is used to align grating along the meridian line in the eyepiece. Then the star's spectra is rotated into view and the grating is so it projects a N-S spectrum. The camera is reinstalled and the process is repeated, aligning the camera so the star moves N-S along the long-axis of the camera's frame. If the camera is inadvertently rotated during the session, it can be realigned at any time using a bright star. One expert amateur recommends imaging the single pencil line of the spectrum. The image is then cropped and stretched. This creates a "digital" drift scan in which it is easier to see the spectral lines. I tried it and it seems to work well. 3) A lot of time was lost getting the newest version of installed and learning VSpec. Vspec is the leading amateur software for spectroscopy. There is an option in the VSpec manual to "Import dat file" that did not appear in the software. I had a number of problems getting the software to run properly on Windows XP. The fix was to rename the current version from "vspec.exe" to "vspec3_51.exe". Leave the old version (3.30) under the executable name of "vspec.exe". Instead of using the raw pixel intensities, it was easier to identify element lines in Vspec if a reference copy of the raw image is first stretched to the full 65,000 pixel range of a 16-bit fits image. In the stretched reference copy, the corresponding x-axis pixel to be paired with a calibration line can be located and written down. The calibration is then actually performed on the unstretched image. 4) Calibration, Calibration, Calibration Initially, I was hoping to calibrate the spectrum image using a reference spectrum of Arcturus - something built-into Vspec. That proved more difficult than expected. Taking the time to make a calibration image using the light pencil or filter-cut off methods seems like it will be much more time efficient and will provide a higher confidence in the calibrated spectral plot. 5) For visual observing the grating can be placed considerably in focus. The Rainbow Optics manual and another expert amateur spectrum imager both noted that the grating, for maximum dispersion, can be placed as far infocus of a Newt or Cassegrain, e.g. 100mm, as is practical. Secondary mirror or tube interference is the practical limitation. I am not sure how that works in terms of diffraction theory (placing the grating at other than prime focus), but it seemed to work on the Ealing. 6) The Rainbow Optics grating needs to be defocused infocus for visual observing. As noted above. Please feel free to drop me a line if any other club member is interested in adding visual spectral observing to their observing program for this season. Peace - Kurt