The soon-to-be-installed 0.70m telescope will not have provision for eyepice viewing. Instead, telescopes of this size usually have an imaging system for collecting image data, among other instruments attached. This telescope will have tow primary instruments attached at its two focal points: an imaging CCD and a fiver-fed spectrograph.
The imaging CCD will be a Finger Lakes Instruments (FLI) PL16803 4096×4096 9μm pixel array (16.8 megapixel array) with an attached 10-place filter wheel system. The CCD is a non-antiblooming gate (NABG) system and is linear for most of its efficiency range. Below is a plot of its quantum efficiency. Given that it cooler can get 55ºC below ambient temperatures, we’ll be operating well below freezing every night, even in the summer. This means less thermal noise and clearer images with better data.
FLI CCD Imager right out of the box.
The filter wheel is a ten-place system, holding 10x50mm square filters for astronomical imaging. In this installation we’ll be using the system mostly for photometric and astrometric work, so the following filters have been installed:
- Luminance: a clear filter.
- Hα: Narrow band Hydrogen filter.
- OIII: Oxygen narrow band filter.
- SII: Sulfur narrowband filter.
- g’2: The Sloan (SDSS) g photometric filter.
- r’2: The Sloan r photometric filter.
- B: Johnson/Cousins B photometric filter (Blue).
- V: Johnson/Cousins V photometric filter (Green/Visual).
- Rc: Johnson/Cousins Rc photometric filter (Red).
- One empty filter position just in case 🙂
The FLI CFW-3-10 filter wheel ready to accept filters and the CCD imager.
The CCD bolts right onto the filter wheel, then the whole assembly is attached to the focal plane of the telescope. All of this is controlled remotely using imaging software, in this case MaxIm DL and ASCOM.
Installing all this requires good lighting, a relatively dust free environment, small tools and some time.
The color filters in their packaging, ready to be installed.
Equipment at the ready: it’s time to install the filters.
With clean-room gloves on, each filter is removed from its packaging, then placed into the correct slot with the filter wheel. Two small plastic retainers are then screwed into place to hold the filter wheel in place. The lovely part of this system’s design is that the filters can be installed without removing the filter wheel’s cover. Many others on the market require complete disassembly – not fun.
Should you be interested, some external Links:
ExeterAstro 