User manual SBIG DSS-7

[. . . ] OPERATING INSTRUCTIONS FOR THE SANTA BARBARA INSTRUMENT GROUP DEEP SPACE SPECTROGRAPH (DSS-7) AND DSS-7 SPECTRAL CALIBRATION PROGRAM (SCP) Alan Holmes 4/27/2005 Overview: SBIG's DSS-7 spectrograph will provide a powerful spectral measurement capability to the amateur. Spectra of nebular, stellar, and galactic objects can now be obtained with modest amateur telescopes as small as 4 inch aperture (but bigger is better). While the SBIG Self Guided Spectrograph is optimized for high resolution stellar measurements, the DSS-7 is more for spectral measurements of extended objects like nebula and galaxies. The SGS has the ability to guide on a star while acquiring its spectra, but the DSS-7 does not. [. . . ] Figure 15 below illustrates a 20 minute exposure from a fairly dark site near Atascadero, California, and my polluted backyard. The prominent lines are labeled, and the longer wavelengths are on the right. When capturing skyglow lines (or any diffuse object) you should use vertical binning of 4:1 or 8:1. Airglow data is very easy to collect ­ you don't need a lens at all, or tracking. Just point the entrance slit aperture straight up!Figure 15: Skyglow Spectra from Two Sites 8000 7000 6000 High Pressure Sodium 5000 Counts Natural Lines 4000 Mercury Light Pollution 3000 2000 1000 Dark Site 0 4000 4500 5000 5500 6000 6500 7000 7500 Wavelength in Angstroms The prominent lines in the airglow you can use for calibration are tabulated in Table 1 Table 1: Prominent Skyglow and Airglow Lines. Source Street Lighting Street Lighting Atmospheric Oxygen Street Lighting Atmospheric Oxygen Element Mercury (Hg) Mercury (Hg) (O) Sodium Vapor (Na) (O) Wavelength in Angstroms 4358. 337 5460. 753 5577. 339 5686. 5- aggregate (blend) 6300. 304 The fact that some of these lines are blended combinations of multiple lines makes them less desirable for calibration. The sodium vapor line wavelength quoted is the centroid wavelength of the three lines that comprise this feature. Operation at the Telescope: I always recommend that one practice with new equipment in the back yard on one of those beautifully clear full moon nights that seem to be so common, so as to not waste time on dark nights. Below I list a step-by-step guide to getting started. 1) Attach the DSS-7/camera combination to the telescope. ­ attach either a nosepiece or a Visual Back attachment to the T-threads above the entrance slit on the DSS7. If you are using a 1. 25 inch eyepiece tube with a simple setscrew holding all that weight, put a safety strap between camera and telescope to keep the assembly from hitting the ground if the setscrew lets go (which they often do as the temperature drops). Align the telescope on a very bright star. 2) Using CCDOPS, select DSS-7, make sure the DSS-7 is enabled, and Select POSITION MODE. The slit will rotate out of the way, and the grating will go the mirror position. The DSS-7/camera combination will now work like a camera, except that the small box exists on the screen to mark the slit position. Focus the bright star, and move it over into the small box. 3) When the star is positioned, stop the POSITION MODE, and immediately select GRAB SPECTRA from the DSS-7 menu, with a 10 second exposure. The slit will rotate in, the grating will go to the first order position, and the spectrum of the bright star will be collected. You should see a bright streak across the center of the image when it downloads. Save it, and take any dark frames you might need. 4) The next target to try is an emission nebula like the Orion Nebula or the Lagoon nebula, something easy to find and bright. [. . . ] Novae and Supernovae are also fairly easy. Supernova down to about 14th magnitude can be captured with an 8 inch (20 cm) aperture telescope. Calibration Lamps ­ I've used the Edmund H71559 Power Supply ($175) and some spectral tubes (Mercury = H60908, and Neon = H60910, each around $30) as calibration sources ­ they work well and the price is reasonable. They also have hydrogen tubes available. [. . . ]