About this product
Part Number: STAR200-F
The new Star Analyser 200 features the same Paton Hawksley high efficiency blazed diffraction grating technology as the SA100, but with double the line density.
Since the Star 100 was introduced equipment used by amateurs has evolved with larger aperture telescopes, bigger camera sensors and close coupled filter wheels becoming more common. The new Star Analyser 200 model has been developed with these users in mind.
Designed for applications where it is difficult to achieve the optimum spacing needed for the SA100. The SA200 gives the same length of spectrum at half the spacing compared with the SA100.
The Star Analyser 200 Features:
High quality transmission diffraction grating mounted in a custom low profile 1.25 inch filter cell
Low profile (5.2mm above the thread) filter suitable for use in close coupled filter wheels
Anti-reflection coated glass protects the grating surface
High efficiency 200 lines/mm blazed design
Spectrum direction marked on the filter cell
Optimised for the larger aperture longer focal length telescope with larger camera sensors
Star and spectrum can be recorded in the same image, which aids identification and calibration
Can be used with filter wheels designed for unmounted filters using the optional mounting kit
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.
Please view this "must see" video. It is our best explanation of how to best use the Star Analyser grating and has 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.
The first thing is: don't worry about getting your setup exactly right. The tolerances in spectroscopy with the Star Analyser are very forgiving. Use the calculator to determine 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.
When 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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