The SA-200 (also referred to as the SA-200-F) is for applications where it is difficult to achieve the optimum spacing using the SA-100.
The SA-200 gives the same length of spectrum at half the spacing compared with the SA-100 (link).
For most users, our SA-100 will be the grating of choice. If you are able to mount our SA-100 in a way that our calculator (link) shows you will be able achieve optimum spacing, the SA-100 should be chosen for best performance.
When mounted at half the distance from the camera, the SA-200 grating gives almost the same performance as an SA-100. We offer the Star Analyser 200 for special situations where the grating has to be mounted inside a filter wheel or closer than the calculator shows is ideal for the Star Analyser 100.
In some telescope configurations, the SA-200 has several important advantages over the SA-100:
1. In applications with close-coupled filter wheels, the distance from the camera to the Star Analyser is generally too short for the SA-100 to perform well. When mounted very near to the sensor, the additional dispersion of the SA-200 is more likely to yield the dispersion necessary for good results.
2. There is an optional mounting kit (see below) for the SA-200, making it fit on a wider range of filter wheels than the SA-100.
3. The SA-200 has a significantly lower profile (7.7 mm total height compared with 11.2 mm for the SA-100) which allows it to be mounted in filter wheels designed for 1.25 inch filters without risk of fouling the wheel housing. (Note that the low profile design means that, unlike the SA-100, there is no thread available above the grating to screw on other accessories.) The SA-200 can be aligned with the camera sensor and held in the correct orientation for example with plumber’s Teflon tape (PTFE) on the thread or a spot of hot melt adhesive.
4. On telescopes with a larger aperture and a longer focal length, the dispersion of the SA-100 can be insufficient to achieve optimal results. The SA-200 produces longer spectra, making it easier to find settings which give satisfactory results with a larger camera sensor.
5. When using the Star Analyser as an objective grating on the front of a DSLR camera lens, the SA-200 is optimized for the typical short focal length zoom lenses found as standard on most DSLRs. The SA-100 will give excellent results too, however it needs a telephoto lens to take full advantage of the additional resolution of a DSLR.
To determine whether the SA-100 or the SA-200 would be a better fit for your setup, see our on-line calculator: link.
You can order the SA-200 grating from our store:
Mounting Kit – for use with the Star Analyser 200 only, not the SA-100
Provided there is sufficient clearance, the Star Analyser 200 grating can also be mounted in filter wheels that are designed to take un-mounted drop-in filters. This optional mounting kit consists of a carrier plate, 2 additional plates that can be used as spacers, and an internally threaded collar to fix the SA200 in position in the carrier plate. The mounting kit is available from our store: link
Before ordering the Mounting Kit, please check your particular model of filter wheel to ensure there is sufficient clearance to accommodate the 7.7 mm height of the SA200.
Using the Mounting Kit in a filter wheel
1. Trim the pre-punched, 1 mm thick black styrene carrier plate to size using a craft knife (score and snap) or scissors to match the filter size used in your wheel (eg 50 mm square, 2 inches round etc.)
2. Mount the SA200 through the pre-punched hole. Rotate it in-place until your spectrum is horizontal on your sensor with the blue end of the spectrum to the left.
3. Fix the grating in position using the supplied threaded collar.
4. The mounting kit comes with two additional plates that can be used as spacers. They’re made of the same material as the carrier plate and are supplied pre-punched with over-sized holes. You can mount these above or below the carrier plate as required to increase the total thickness and place the SA200 at the optimum height to clear the housing on your filter wheel.
Tip: To ensure a good fit when trimming the plates to size, first make a template using a (weak) adhesive-backed label paper and check that it fits correctly in the filter wheel. Then stick the label centrally onto the plate and trim around it.
If necessary for the clearances in your particular filter wheel, it is also feasible for you to fabricate a carrier which lowers the position of the SA200 below that shown in the above schematic. You can build up your material to the desired thickness using polystyrene and cement. Remember that you need 7.7 mm free space in your filter wheel to accommodate the height of the SA200.
Alternate method for using the Mounting Kit — in an empty 2″ filter cell
Because you can easily trim the mounting plate, our kit can be adapted for use in a variety of mechanical configurations. For example, if you have a blank 2″ filter cell, trim our kit’s mounting plate to the size of a 2″ filter as shown on the right below. Then secure the SA200 in the mounting plate using the mounting kit’s collar. Finally, install the assembly in your empty filter cell.
Below shows the final assembly with the SA200 and trimmed mounting plate installed in the 2″ filter cell
Questions? Use our contact form to discuss them with our Help Desk experts: link.