User manual SBIG ST-8E

[. . . ] Operating Manual CCD Camera Models ST-7E, ST-8E, ST-9E, ST-10E and ST-1001E Santa Barbara Instrument Group 147A Castilian Drive Santa Barbara, CA 93117 Phone (805) 571-7244 · Fax (805) 571-1147 Web:<www. sbig. com> · Email:<sbig@sbig. com> Note: This equipment has been tested and found to comply with the limits for a Class B digital device pursuant to Part 15 of the FCC Rules. These limits are designed to provide reasonable protection against harmful interference in a residential installation. This equipment generates, uses, and can radiate radio frequency energy and if not installed and used in accordance with the instructions, may cause harmful interference to radio communications. However, there is no guarantee that interference will not occur in a particular installation. [. . . ] This is identical to what is typically sold at Radio Shack stores as an extension cable. 4. 4. 1 Using Mechanical Relays Older telescopes generally require modifying the hand controller to accept input from the camera's Telescope port. The difficulty of this task varies with the drive corrector model and may require adding external relays if your drive corrector will not accept TTL level signals. We maintain a database of instructions for the more popular telescopes that we will gladly share with you. For a minimal charge will also modify your hand controllers if you feel you do not have the skills necessary to accomplish such a task. We sell a mechanical relay box that interfaces to the ST-7E/8E/9E/10E/1001E, and will interface to the older drives. In general, the camera has four signals that are used in tracking applications. There is one 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 with the proliferation of TTL input telescopes the relays were removed in the ST-7 and ST-8 (we do offer an external relay adapter accessory). The following paragraphs describe the generalpurpose interface to the telescope which involves using external relays. Page 24 Section 4 - Camera Hardware In our older camera models and in the optional relay adapter accessory, each of the relays has a Common, a Normally Open, and a Normally Closed contact. For example, when the relay is inactivated there is a connection between the Common and the Normally Closed contact. When the relay is activated (trying to correct the telescope) the contact is between the Common and the Normally Open contacts. If your hand controller is from a relatively recent model telescope it probably has four buttons that have a "push to make" configuration. By "push to make" we mean that the switches have two contacts that are shorted together when the button is pressed. If that's the case then it is a simple matter of soldering the Common and Normally Open leads of the appropriate relay to the corresponding switch, without having to cut any traces, as shown in Figure 4. 1 below. A: Unmodified Push to Make Switch B: Modified Push to Make Switch c common switch switch relay nc no normally open Figure 4. 1 - Push to Make Switch Modification Another less common type of switch configuration (although it seems to have been used more often in older hand controllers) involve hand controller buttons that use both a push to make contact in conjunction with a push to break contact. The modification required for these switches involves cutting traces or wires in the hand controller. Essentially the relay's Normally Open is wired in parallel with the switch (activating the relay or pushing the hand controller button closes the Normally Open or Push to Make contact) while at the same time the Normally Closed contact is wired in series with the switch (activating the relay or pushing the hand controller button opens the Normally Closed or the Push to Break contact). This type of switch modification is shown in Figure 4. 2 below. A: Unmodified Push to Make/Break Switch c common B: Modified Push to Make/Break Switch c common c nc switch nc no normally open normally closed nc no relay no normally open normally closed Figure 4. 2- Push to Make/Break Modification The last type of hand controller that is moderately common is the resistor joystick. In this joystick each axis of the joystick is connected to a potentiometer or variable resistor. Moving the joystick handle left or right rotates a potentiometer, varying the resistance between a central "wiper" contact and the two ends of a fixed resistor. The relays can be interfaced to the joystick as shown in Figure 4. 3 below. Essentially the relays are used to connect the wire that Page 25 Section 4 - Camera Hardware used to attach to the wiper to either end of the potentiometer when the opposing relays are activated. A + relay wiper B A C - relay c c no C nc no nc B potentiometer A: Unmodified Joystick B: Modified Joystick Figure 4. 3 - Joystick Modification A slight variation on the joystick modification is to build a complete joystick eliminator as shown in Figure 4. 4 below. The only difference between this and the previous modification is that two fixed resistors per axis are used to simulate the potentiometer at its mid position. [. . . ] The desiccant is contained in a small cylindrical plug that screws into the chamber from the rear. In normal operation the useful life of the desiccant is over a year. If the CCD chamber is opened often, the desiccant should be regenerated when frosting is noticed. Follow the procedure below to regenerate the desiccant: 1. [. . . ]