About this product
Part Number: STAR100
Since its launch in 2005, the Star Analyser 100 has introduced thousands of amateur astronomers worldwide to the fascinating field of spectroscopy.
Features Paton Hawksley high efficiency blazed diffraction grating. For most users the SA100 continues to be the model of choice, particularly for those using cameras with smaller sensors. When used with these cameras optimum performance can, for example, be achieved with the SA100 mounted on the camera nosepiece.
The video below is our best explanation of how to best use the Star Analyser grating and includes lots of hints and suggestions.
Are you using a DSLR? If so please watch this video
How to mount your Star Analyser grating
Note: Using a Star Analyser grating requires that you already be somewhat proficient at capturing images of stars. You need to be able to locate specific stars in the sky. And you will need to be able to capture images of them that are properly exposed, well-focused, and not smeared from their movement through the sky.
Don't worry about getting your setup exactly right. The tolerances in spectroscopy with the Star Analyser are very forgiving. Use the calculator here to come up with approximate settings, and then go out and have fun capturing spectra!
Are you using a standalone DSLR? You don't need to use the calculator on this page. Just read this paragraph and skip everything else on this page! First, thread the AD-58 adapter: onto your camera's lens cap threads. A variable (zoom) lens is strongly recommended. Then, for the 18 - 55 mm standard kit lens, use a Star Analyser 200. Or, for a 70 - 200 mm lens, get a Star Analyser 100. It can be difficult to capture spectra without tracking, so for best results, your camera should be on a tracking mount. (Note to non-Canon camera owners: if your lens cap threads aren't 58 mm, you'll need a thread adapter).
Are you using a DSLR with your telescope optics? Use the AD-T2 adapter: on your camera's T-Ring. You'll most likely want to use the Star Analyser 100. The AD-T2 puts the grating 60 mm from the camera sensor. Plug your camera specs into the calculator below to see the entire configuration.
Are you using an astronomical video or FITS camera on your telescope? For almost all telescope and camera combinations (unless you're using a filter wheel) the calculator above will probably recommend our Star Analyser 100. Use the calculator to confirm the distance to the camera sensor with the Star Analyser 100.
The Calculator's Output
If the Calculator shows three green flags, you can ignore the details in Output section. It simply shows some technical details that aren't critical. The key Output fields show you how the grating performs with your Input values:
A red message warns you if the Dispersion value is outside limits. Useful values are typically in the range of 7-20 Angstroms/pixel, but the optimum value depends on your particular setup.
Dispersion (field 10) describes how spread out the spectrum is. The lower the Dispersion value, the more spread out the spectrum. This value needs to be high enough to maximize the detail visible in your spectra, but not so high that your spectra become too dim.
Spectrum Coverage (field 11) describes how much of the spectrum fits on your camera sensor. To calibrate your spectra easily, you should be able to see from 0 to at least 7,800 Angstroms. A red message warns you if this value is outside limits.
Should I use the Star Analyser 200 instead of the 100?
In some applications it can be difficult to get three green flags when using the SA100. In these cases the Star Analyser 200 (SA200) is often helpful. The SA200 generates the same spectrum length at half the spacing.
Where optimum spacing is feasible with the SA100, it should be chosen for best performance. However, there are three cases where the SA200 is particularly useful:
In applications with close-coupled filter wheels, the distance from the camera to the Star Analyser is generally too short for the SA100 to perform well. This close to the sensor, the additional dispersion of the SA200 makes it more likely to yield the dispersion necessary for satisfactory results. The SA200 also has a low-profile design, plus an optional mounting kit, making it fit on a wider range of filter wheels than the SA100.
On telescopes with a larger aperture and a longer focal length, the dispersion of the SA100 can be insufficient to achieve the best results. The SA200 produces longer spectra, making it easier to find settings which give satisfactory results with a larger camera sensor.
When using the Star Analyser as an "objective grating" on the front of a DSLR camera lens, the SA200 is optimised for the typical short focal length zoom lenses found as standard on most DSLRs. The SA100 however needs a zoom lens to take full advantage of the additional resolution.
Note that where the optimum spacing can be achieved with SA100, it should be chosen for best performance.
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