Santa Barbara Instrument Group CCD Camera Operating Manual

Contents

Santa Barbara Instrument Group CCD Camera Operating Manual Manual pdf 28 page image

Section 4 - Camera HardwarePage 24Typically you would take ten 1 minute "snapshots" to produce an image that is comparable to asingle 10 minute exposure except that no guiding is required. The reason no guiding isrequired is that with most modern telescope mounts the drift over the relatively short 1 minuteinterval is small enough to preserve round star images, a feat that even the best telescopemounts will not maintain over the longer ten minute interval. The Track and Accumulatesoftware does allow correction of the telescope position in the interval between snapshots tokeep the guide star grossly positioned within the field of view, but it is the precise co-registration of images that accounts for the streakless images.The host software and the CCD camera control the telescope through the 9-pinTelescope port on the camera. This port provides active low open collector signals to theoutside world. By interfacing the camera to the telescope's controller the CPU is able to movethe telescope as you would: by effectively closing one of the four switches that slews thetelescope.Note: You only need to interface the camera's Telescope port to your telescope if you areplanning on using the camera system as an autoguider or selfguider, or feel you need tohave the Track and Accumulate command make telescope corrections between imagesbecause your drive has a large amount of long term drift.Some recent model telescopes (like the Celestron Ultima and the Meade LX200) haveconnectors on the drive controller that interface directly to the camera's TTL level Telescopeport. All that's required is a simple cable to attach the 9 pin Telescope port to the telescope'stelephone jack type CCD connector. SBIG includes its TIC-78 (Tracking Interface CableAdapter) for this express purpose although it is easy to modify a standard 6-pin telephonecable for interface to the Telescope port (see Appendix A for specific pin outs, etc.). The TIC-78plugs into the 9-pin port on the ST-7E/8E/9E/10E/1001E, and a standard phone cable, whichwe supply, connects the adapter to the telescope drive. Note: phone cables come in a fewvariations. We use the six-pin cable, and the pin order is reversed left to right relative to theconnector from one end to the other. This is identical to what is typically sold at Radio Shackstores as an extension cable.4.4.1 Using Mechanical RelaysOlder telescopes generally require modifying the hand controller to accept input from thecamera's Telescope port. The difficulty of this task varies with the drive corrector model andmay require adding external relays if your drive corrector will not accept TTL level signals. Wemaintain a database of instructions for the more popular telescopes that we will gladly sharewith you. For a minimal charge will also modify your hand controllers if you feel you do nothave the skills necessary to accomplish such a task. We sell a mechanical relay box thatinterfaces to the ST-7E/8E/9E/10E/1001E, and will interface to the older drives. Contact SBIGfor more information.In general, the camera has four signals that are used in tracking applications. There isone output line for each of the four correction directions on the hand controller (North, South,East and West). Our previous cameras had internal relays for the telescope interface, but withthe proliferation of TTL input telescopes the relays were removed in the ST-7 and ST-8 (we dooffer an external relay adapter accessory). The following paragraphs describe the general-purpose interface to the telescope which involves using external relays.