In August 2011, I decided to upgrade my optical train. The initial upgrade was to be the FW8-STL, an 8-position computer-controlled filter wheel which replaces the internal 5-position filter wheel in the STL-11000M camera; this would allow me to move to full narrowband images - Ha, OIII, SII as well as the normal L, R, G, and B (so 7 filters are required in total). However, with narrowband filters (very narrow at 3nm bandwidth), not much light from stars gets through the filters, so guiding with the normal guidechip (a second, smaller CCD in the SBIG cameras) is usually not practical - it is nearly impossible to find a bright enough guide star ... and then the framing of the image may become non-optimum. So, an off-axis guider and remote guide head is needed, which can pick off some light from the scope before the light passes through the narrowband filters - such light being focused (by a Borg helical focuser) onto the chip of a small CCD guide camera - in my case, the SBIG "remote guide head" (RGH) which is an accessory to the STL-series SBIG cameras. The SBIG remote guide head provides a second TC-237 guide chip that can be mounted (using the MOAG) ahead of the narrowband filters. The RGH uses the TC-237, which is the same guide chip as used in the STL-11000M camera, incorporates thermoelectric (TEC) cooling and a shutter for taking dark frames. The resolution of the TC-237 is 657x495 with 7.4 micron pixels. Instructions for the SBIG remote guide head can be found here. |
At right, you can see the bottom of the RGH, which includes a 1/4-20 tripod mounting thread. Attached to the nosepiece of the RGH is an Astrodon Luminance (NIR blocked) filter, so that stars are not unnecessarily bloated.
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 | Another view of the RGH - from the front - shows the Luminance filter attached to the nosepiece. There were two bodies of the RGH made - one silver to match the STL-series cameras, and one anodized to match the ST-series cameras; however, they both incorporate the TC-237 chip, and either can be operated with either series of camera. |
At right is the back of the RGH, showing the connector (top) that attaches via special cable to the STL or ST series cameras, and the dessicant plug, which must be unscrewed to bake or replace the internal dessicant. |  |
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Mechanical specs of the remote guide head are shown at left. |
And at right are the Electronic specifications of the remote guide head. |  |
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The image at left, from the SBIG online catalog, shows the RGH connected to an STL-series camera via special cable provided by SBIG. |
At right, you can see the remote guide head connected to the Borg helical focuser, which is part of the Astrodon MOAG off-axis guider (between the AO-L and the FW8 filter wheel). As noted elsewhere, this image shows the AO-L/MOAG/RGH oriented 180 degrees from what is conventionally used - a 'neater' package, but not consistent with mount bump directions calculated by CCDAutoPilot. |
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