CHAPTER 13: Digital Astrophotography — What’s NEW?Chapter_13__Digital_Astrophotography.htmlChapter_13__Digital_Astrophotography.htmlshapeimage_2_link_0
New Autoguiding Options (updated April 2012)

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 are designed specifically to serve as an autoguider camera. The Orion unit is shown at left with a fixed Borg 50mm guidescope; the QHY5 unit is below with its optional 50mm guidescope. 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. 
The nearly identical QHY5 guider camera from CCDLabs’ (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 QHY5 drivers are only for Windows. But the Orion Starshoot Autoguider now comes with a version of PHD Guiding that will run the Starshoot on both Windows and Mac OS computers. Download it from the Orion website.
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 “KWIQ Guider” package (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 centring 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. 
These are 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. Like KWTelescope, Orion also now offers the Starshoot packaged with a custom-fitted 50mm guidescope, a great and compact combo for $350.
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 (a small netbook serves the purpose well). 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. 
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 (shown above), 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 hundreds of images, it has never failed to find and lock onto a guide star without any need to get some isolated bright star in the field. It essentially requires no work to use 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.
Another guiding solution from SBIG is their new ST-i, available in both color and monochrome versions for $600. Both versions feature 648x484 pixel sensors sensitive enough to guide on any star in a random field. Both can be used as high-frame-rate (5 to 21 frames per second) planetary imaging cameras, but can also serve as autoguiders. 
The ST-i is not a stand-alone system but must be operated with a PC running SBIG’s CCDOPS software or other imaging/camera control programs that can control an autoguider. The ST-i needs to be coupled with a suitable guidescope or off-axis guider, making this a fairly costly option but perhaps suitable for anyone also looking for a high-quality planetary imaging camera.
Orion StarShoot Solitaire (now discontinued)
A lower-cost alternative from Orion (but still $500) was their StarShoot Solitaire Autoguider, another stand-alone unit that had 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, still sells an identical unit under their own SmartGuider brand name.
Like the SBIG SG-4, the Solitaire required a user-supplied guidescope, though it did need not to be anything large — a 66mm to 80mm refractor was fine. For the Solitaire, the guidescope has 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. 
In our tests we found that the Solitaire was not very sensitive and so required 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. An accessory X-Y Axis Finder ($230) was available from Orion to aid in this.
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 could not recommend the Solitaire. Indeed, it has since been discontinued.
Celestron NexGuide / Sky-Watcher SynGuide
Now available, and nearly identical to the SynGuider offered in some markets by Synta/SkyWatcher, Celestron’s little NexGuide camera is another stand-alone autoguider that draws little power (it runs off 4 D cells, or an external 6-12 volt supply). Unlike the SG-4, the NexGuide offers 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?
Not at all — it really works! Our tests prove that it guides very accurately and sets up and calibrates quickly and with no errors or bugs. The key downside is sensitivity. You do have to give it a fairly bright (7th magnitude or better) guide star, well-placed on the small chip. That requires some fussing to physically position a suitable lone bright star into the centre of a parfocalized eyepiece. You then swap in the guider. Initial set up requires reaching focus on the guider by aiming at a bright star, and shifting focus in increments so the star “image” on the screen is as small as possible and the brightness numbers as large as possible. Then swap in an eyepiece and use the included barrel ring to set up the eyepiece so it focuses at the same point as the NexGuide. You do that once, then lock down the focuser of your guidescope, which should be a solid 60 to 80mm refractor, mounted in rings that allow you to shift the guidescope around to locate and centre a suitable star near your target. (Celestron now offers the required mounting hardware — or mounting plates and rings are available from Losmandy or ADM.) Centring a guide star can take a bit of work every time you move to a new target. In initial tests rarely, if ever, did a bright enough star show up in the field to begin with, even at the NexGuide’s maximum exposure of 4 seconds. Hunting for one nearby was always required. The NexGuide and SynGuide units did both work well with Celestron’s CGEM mount, a mount some people have had problems with when trying to guide with PHD Guider software and another CCD autoguider.
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 combination with the StarShoot. But for true-stand-alone computer-less autoguiding, the SBIG SG-4 beats all. The Celestron NexGuide is a great lower-cost alternative, but you pay the price in increased work at the scope, manually centring a bright guide star for every object, and in the need for a larger and more costly guidescope and mounting hardware. For my review of the NexGuide see the April 2011 issue of Sky and Telescope.
Meade’s LX800 Star-Lock System
Announced in late 2011, Meade’s LX800 system features a hefty Go To mount with the proven Autostar II hand controller, but with the unique addition of an 80mm refractor dedicated to autoguiding. The refractor has a small finder and a autoguider camera that automatically selects a guidestar and controls the mount under autoguiding without any need for an outboard computer. The ability to guide on stars as faint as 11th magnitude is promised which should certainly mean that the system can guide on any field without any need for hunting for and centring a bright guidestar, unlike the Celestron NexGuide system. 
However, you do have to buy the complete LX800 mount ($6,000) to get the benefit of this integrated autoguiding. The mount is available on its own or packaged with a 130mm f/7 apo refractor ($9,000), or 10- to 14-inch f/8 ACF catadioptric scopes ($8,000 to $10,000). 
As of this writing (January 2012), LX800 product line was not yet available for delivery. While this sounds like a fine integrated system and a very capable Go To mount for someone looking for a high-end system, we would advise waiting until after the early adopters and Meade fans test their first units, and the inevitable bugs are worked out of the software. Autoguiding can be a black art at best, with some combinations of hardware and software prone to runaways or oscillations for no obvious reason. 
Right now, the market offers three options for autoguiding that we can recommend:
For its sheer one-button, hands-off ease of use, SBIG’s SG-4 is our pick for stand-alone guiding with any high-quality mount. When used with the eFinder lens it makes a wonderfully compact self-contained system. But it is costly. 
The Celestron NexGuide or Sky-Watcher SynGuider are much cheaper stand-alone choices but require more work to set up and find a suitable guidestar. It does work well with Celestron’s CGEM mount. 
The Orion StarShoot/PHD Guider combo can guide on anything in the field so doesn’t need much fussing to centre a guide star (we use it with guidescopes that are fixed). The similar QHY5 also works well but tends to be fussier about the software “drivers” required - they come from a third party. Both are best combined with their 50mm guidescope options, and are good picks for easy guiders to use. But they do require a laptop in the field (Mac fans can run the Orion Starshoot). The SBIG ST-i is a more costly option requiring an outboard PC. It might be suitable if you are also looking for a high-quality planetary camera or a guider to integrate with one of SBIG’s other CCD cameras.
The Meade LX800 system is still unproven; it will be suitable only if you are in the market for an entire high-end mount and only after any initial software bugs are eliminated.
— Alan Dyer