The Star Analyser 100 is a high efficiency 100 lines/mm transmission diffraction grating, blazed in the first order. It is mounted in a standard 1.25 inch diameter threaded cell, to be compatible with most telescopes and accessories. It has been designed to make the production of low resolution spectrum images of a wide range of point like astronomical objects as easy as possible. It complements a wide range of types of camera used in astro-imaging. It can however also be adapted for visual use. A locking ring is also supplied to lock the grating in the desired orientation.
A simple webcam is enough to record bright star spectra. Above spectra have been recorded with a 8'' f/9 telescope and a Philips ToUCam Pro webcam. Star image (zero order) is on the left while the spectra spread from violet to infra-red. Some absorption lines are visible.
Spectrum can the be processed and wavelength calibrated with a computer. A more detailed analysis (shape, spectral lines...) can then be done.
The bright emission lines in the fleeting flash spectrum of the sun’s thin outer layer, the chromosphere, appear briefly for a few seconds during the 2006 solar eclipse, at the end of totality before the blindingly bright photosphere reappears.
The bright yellow line is caused by the element Helium which was discovered in the chromosphere using spectroscopy before it was found on earth. This image was recorded using a Star Analyser 100 mounted in front of a Philips ToUcam Pro webcam fitted with a 29mm FL camera lens.
This spectrum of a bright Perseid meteor streaking upwards away from Cassiopeia was captured using a monochrome long exposure modified webcam with its standard wide angle lens. The Star Analyser 100 was mounted in front of the lens.
The zero order meteor trail can be seen to the left with the spectrum spread out to the right of the trail. A single green emission line can be seen initially, produced by oxygen in the upper atmosphere heated by the meteor. As the meteor flares and burns up, several emission lines become obvious.
Birth and Death of the stars...
Thanks to its design, Star Analyser 100 allow you to take spectra of deep sky objects. for exemple, diffuse nebulae (where gaz gives birth to stars) and planetary nebulae (remains of dead stars).
Those spectra first show how usefull Halpha or [OIII] filters can be as most of the light coming from those nebulae is from those elements - viewing contrast is then improved. But also, those [OIII] lines - called forbidden lines - demonstrates the very low density environment of those gaz.
Within other galaxies, you can also take spectra of supernovae. Those very violent explosion occure at the end of massive star lives.
With small telescope, you open wide the doors of Astrophysics!
At the far end of our universe: quasars
Although they are the most luminous objects in the universe, Quasars are found at vast distances and so appear rather faint. Even at mag +13 though, QSO 3C273 is within range of the Star Analyser 100 and a 200mm aperture. This image was taken using a webcam fitted with a monochrome CCD and modified for long exposures.
The graph of the spectrum reveals Hydrogen emission lines, but shifted approximately 16% to the red from where they would normally be expected. This is because the universe has expanded since the light left this distant object. This figure can be used to estimate the distance to the Quasar (approximately 2 thousand million light years!)
High quality manufacturing
Star Analyser has been designed for astronomical use. Maximum flux in first order (ie: blaze) and transmissivity have been very carefully studied.
The Star Analyser has been designed and built to give many years of trouble free service. It cannot be dismantled by the user. To protect the delicate diffraction grating surface, it has been sealed between anti-reflection coated glass cover discs. The sealed unit is fixed in the cell in the correct alignment.
A threaded locking ring is supplied which can be used to lock the Star Analyser in the desired orientation. The ring is screwed into the internal thread of the camera nosepiece and the Star Analyser screwed in until it locks against it. By adjusting how far the locking ring is screwed in, the Star Analyser can be locked in the required orientation.
The Star Analyser 100 has been designed to work with the smallest commonly used sensor chips and the range of camera nosepiece designs commonly encountered. Some cameras have larger chips and/ or shorter nosepieces and so would benefit from an increase in distance of the device from the sensor.
The minimum recommended distance (in mm from the sensor to the tip of the nosepiece where the Star Analyser 100 screws in) is 4x the camera pixel size in microns. For example, for the ToUcam webcam, the distance would be 5.6x4=22.4mm. If you find that the distance for your setup is less than the minimum value, we recommend purchasing sufficient spacers to bring the distance above the minimum.
Each spacer adds an adjustable 7-10mm. To date, the following cameras are known to benefit from the use of spacers.
||Nbre of spacers
|Meade DSI pro||no need
If you are not sure if your particular setup requires spacers, please e-mail us with details of your camera and the sensor to 1.25" nosepiece tip distance and we can advise you.
Use your Star Analyser in front of a lens ?
With minimum home work, you can attach the Star Analyser 100 in front of your camera lens. Simple exposures will show spectra of bright stars!
Mars & Aldebaran spectra (reduced size image)
|Name||Shelyak Instruments - Star Analyser 100|