New Autoguiding Options

$New Autoguiding Options (updated September 10) While the latest revised edition of the book (printed in 2010) provides updated info, autoguiders change rapidly. Here are our latest recommendations: Orion StarShoot Autoguider & CCDLabs’ QHY5 Autoguider These two little CMOS-based digital cameras (the Orion unit is shown at left, the QHY5 unit below) are designed specifically to serve as an autoguider camera. The Orion StarShoot comes packaged with an installation CD with guiding software from Stark Labs, PHD Guiding, and the driver software needed for your computer to recognize the camera as a USB device. A nearly identical camera, CCDLabs’ QHY5 guider (we tested one on loan from the Canadian dealer, KWTelescope) requires the buyer to download operating software (PHD Guiding works fine) and drivers in a bit more of a do-it-yourself affair. The drivers for either camera run only on Windows, so Mac users are out of luck. These little cameras (they weigh no more than a small eyepiece) work great. They connect directly to a mount’s ST-4-compatible autoguider jack (the phone-style RJ-11 jack). So unlike some low-cost CCD or webcam cameras pressed into service for autoguiding (like a Meade DSI) the Orion and QHY units do not need a “USB-to-autoguider port” translator box like Shoestring Astronomy’s GPUSB box. As shown here, the only other connection is a USB cable from the camera to the Windows laptop computer of your choice. Note: You’ll also need a solidly-mounted guidescope, such as a small refractor — the Orion StarShoot and QHY5 are just camera heads and have no optics. However, the QHY5 is offered by KWTelescope in a nifty package (shown at left) with modified 50mm finder as a guidescope. Even with a 50mm guidescope, either camera picked up enough stars in random fields that there was little need to fuss with centering a bright guide star. The PHD Guiding software (shown at left) is a pleasure to use, with simple pushes of a few large screen buttons (thus the name: Push Here Dummy Guiding) all that’s needed to get the guider calibrated and guiding. Right now, these are the units we’d recommend for anyone getting into autoguiding, a required step for taking the best deep-sky images through any telescope. Of the two, the Orion StarShoot is more widely available and comes better packaged with all the required software in a documented Install disk. Orion also now offers a unit, the Planetary Imager/Autoguider ($350) that can shoot 50 fps movies as well as exposures up to 5 seconds long for guiding. The StarShoot is available from Orion Telescopes and Binoculars for $280. The QHY5 is available from KWTelescope for $300 for just the camera, or $400 for the KWIQ Guider camera/guidescope combo package. With autoguiding cameras now available at such low cost there’s little reason not to autoguide. However — the principle drawback of low-cost autoguiders (like the Orion StarShoot, QHY5, or using a Meade DSI as an autoguider) is that they must be operated with a computer. In the field this can cause issues with providing sufficient power. And the laptop can be a fuss to set up and operate, especially in cold weather. SBIG SG-4 Up to now the few stand-alone autoguiders (i.e. ones not requiring a computer) such as SBIG’s pioneering ST-4 and later STV (both now discontinued) worked great but were costly and drew quite a bit of power, up to 3 amps at 12 volts, making them tough to power in the field. SBIG (Santa Barbara Instruments Group) offers a new stand-alone “smart” autoguider, the SG-4, that comes in a solid box with minimal controls and displays. It draws only 200 milliamps and can operate from several nights from a typical jump-start battery, making it great for field use. Initial setup and focusing does require the use of a laptop at the telescope and the SG-4 software (Windows only) that comes with the guider. After that, this unit is truly stand-alone. However, for each subsequent use the SG-4 does require that the guider be attached to the guidescope in the same orientation as it was when first calibrated. And without a laptop to view an image from the SG-4 there is no way to focus the camera should the guidescope slip out of focus. Scribe the drawtube with the correct focus position. An alternative is to couple the SG-4 with SBIG’s little eFinder ($245) lens, for a compact guidescope. We’ve tested the SG-4/eFinder combo and it works great. Using the guider could not be simpler. Just bolt it to the side of the telescope (it has a 1/4-20 bolt hole in the base), press a button, and the unit starts guiding in seconds. As long as it was properly calibrated initially (on a star near the celestial equator) no further calibration is necessary — only flipping an E-W switch when you flip an equatorial mount from one side of the pier to the other. The SG-4 simply provides a flashing green light to indicate proper guiding. There are no numeric readouts, no graphs of guiding errors, nothing to tell you how well it is guiding. But it does guide very well! In dozens of images, it has never failed to find and lock onto a guidestar without any need to get some isolated bright star in the field. Because of its quick one-button operation and accurate guiding, it has become the guider of choice for Dyer! The downside of the SG-4 is its cost: $995. While the SG-4 is clearly aimed at entry-level users with cameras, such as DSLRs, that lack any internal guiding chips, beginners are likely to balk at an accessory that costs as much as they are often willing to pay for the imaging camera itself. But this is certainly the best stand-alone autoguider on the market. Orion StarShoot Solitaire A lower-cost alternative from Orion (but still $500) is their StarShoot Solitaire Autoguider, another stand-alone unit that has a small controller with an LED display to crudely show: where in the field the guide star is located (it automatically selects the brightest star in the field); a numeric indication of guide star focus; and a running graph of guiding corrections. The original manufacturer in Italy, LVI, also sells an identical unit under their own SmartGuider brand name. Like the SBIG SG-4, the Solitaire requires a user-supplied guidescope, though it need not be anything large — a 66mm to 80mm refractor will do. For the Solitaire, the guidescope should be mounted solidly but have the ability, through adjustable rings, to shift its position relative to the main scope in order to find and frame a suitable guide star. Here we come to the principle disadvantage of the Solitaire (a process we went through on many a night with the original ST-4): the Solitaire needs a lone bright star in its small field, one it can lock onto and not be confused by any other star of similar brightness. Finding and focusing such a guide star can require swapping back and forth from an eyepiece to the guider, while fussing with shifting the guidescope a little this way, a little that way. And to focus you adjust the guidescope while watching a numeric readout peak in value, with each iteration taking several seconds to complete, a slow and tedious process. Nevertheless, if you dedicate a small scope for use with the Solitaire, focusing need be done only once. However, in our tests we found that the Solitaire was not terribly sensitive and so requires a fairly bright (5th magnitude or better) guide star, making the task of getting a suitable star on the tiny chip a chore of trial and error, requiring shifting the guidescope around to make sure the brightest star is centred in the field. Orion’s X-Y Axis Guidestar Finder for precisely shifting the eyepiece and camera laterally around the field of the guidescope helps, but it adds another $230 to the package cost. In some of our tests, we found that the Solitaire also refused to complete the calibration process, or would mistakenly guide on hot pixels. Because of its lack of sensitivity and unreliability and, with accessories, high cost (you might as well get an SG-4 that really works and is so much easier to use!) we cannot recommend the Solitaire. Celestron NexGuide Announced in summer 2010, and similar to a unit offered in some markets by Synta/SkyWatcher, Celestron’s little NexGuide camera is another stand-alone autoguider that draws little power and offer display readouts to aid in focusing and calibrating. The appeal here is cost: about $300, much less than an SG-4 or Solitaire, and comparable to a StarShoot, but not requiring a computer. Too good to be true? As of this writing we have yet to test a NexGuide. The key concern would be sensitivity. If one has to fuss to physically position a suitable lone bright star onto the small sensor, then setup and use could be a nuisance, more than we’re prepared to bother with. But we’ll see once we try one. By contrast, with computer-operated cameras like Orion’s StarShoot, and using free software like PHD Guiding, you can select any star you like to be your guide star simply by clicking the mouse on the displayed image on the laptop’s screen. The little StarShoot is sensitive enough that, even using a 50mm guidescope, we’ve found there’s almost always a star bright enough to guide on in any field, and it need not be the brightest. And you know that the star you pick is a good one, and not a double star to confuse the guider, nor too close to the edge where it could drift off and be lost. This makes guide star selection a no-fuss process. But you had to set up and power a computer. For field use away from AC power, a little Windows netbook (typically $300 on up) with a long-life 7- or 8-hour battery might be a great choice. But for true-stand-alone computer-less autoguiding, the SBIG SG-4 beats all. Until the NexGuide proves itself, the SG-4 is our pick for stand-alone guiding, and the Orion Starshoot/PHD Guider combo our pick for computer-aided guiding.$ shapeimage_3_link_0