Courtesy of
November 1990



It's a black box that helps you find thousands of deep-sky objects.
It's not cheap, but it works. And all without polar alignment.

by Alan Dyer

     If you're like me you've been suspicious of all the electronic gizmos on the market that promise to do just about everything but look through the eyepiece for you. As an "old guard" observer, I considered the use of any computerized gadget to track down celestial objects as somehow cheating. Or at the very least they were a technological short-cut that prevented you from learning the sky. Digital setting circles (heck, even real setting circles!), CATs, and the like were for wimps, right? Real observers didn't use them; real observers didn't need to use them!
     Well, count me in as a convert. I've used the NGC-MAX and I like it. It works as promised and takes much of the drudgery out of tracking down deep-sky objects, especially the ones that are tough destinations for a star-hop. In fact, on my first night out I forgot I was supposed to be critically reviewing the product and just got carried away effortlessly moving from one object to another. With the NGC-MAX guiding the way, I found I could quickly follow any observing whim.

The Facts about the MAX

     The NGC-MAX unit itself is a compact 4.5- by 3-inch black box that can help you find thousands of deep-sky objects. The installation kit comes with two encoders. These little devices attach to the axes of the telescope and send pulses to the computer to tell it how far the scope has moved. You still do the moving, however; this product does not have motors to move the telescope for you. The $829 NGC-MAX is essentially a very smart set of digital setting circles; it can tell you where your telescope is pointed and where your telescope should be pointed. But you do the pointing. As such, it is similar to the CAT (Computer Aided Telescope) accessory we reviewed in the December 1987 issue.
     The MAX's control box contains the LED readouts and the microprocessor electronics, including the ROM (Read Only Memory) chip that contains all the data about the objects. Burned into the ROM chip are data on the 110 Messier objects, 7,840 NGC objects (with data taken from the Revised New General Catalogue), and 363 stars, including many double stars. The latest models also contain information on planetary positions, allowing you to track down Uranus, Neptune, and Pluto or bright planets in the daytime. To find planets you must enter the current date. A special non-volatile memory also allows you to enter coordinates for up to 25 objects of your own. These remain in memory even after the power is turned off. The unit operates on a single 9-volt battery.
     The NGC-MAX is sold by JMI, a small company that many readers will know as Jim's Mobile Industries. JMI doesn't make the MAX; it is actually made by Tangent Instruments of Mountain View, California. Tangent sells the same electronics package to Celestron (who markets a product almost identical to the NGC-MAX called the Advanced AstroMaster) and to Lumicon (their unit is the NGC Sky Vector). JMI's product is available for Celestron and Meade telescopes (except for Celestron scopes on the small Polaris mount) as well as for many other brands of telescopes such as Astro-Physics, Coulter, Questar, Takahashi, and TeleVue.

Installing the MAX

     The prospect of installing precision encoders sounds like a daunting chore. However, I'm happy to report that the installation of the NGC-MAX was quite easy.
     All the necessary hex wrenches were supplied. Total installation time was about 30 minutes. I encountered only a couple of minor problems: the bolt through the center of the large RA gear was not as depicted in the instructions and it was also not clear from the diagram which two screws you use to attach the RA encoder to the base of the fork arms. As luck would have it, I used the wrong two, which then caused the encoder gear to slip as it hit the screw heads. After figuring out which were the right screws the rest of the installation went well. The only other quibble I had with the instructions was that some screws were shown that weren't needed or were already attached. For those of us who can't tell a 6/32 screw from a 10/32, a clearer diagram and labeling of kit parts would be nice. This would also ease the worry you have at the end when you find you have a bunch of little screws left over.
     For the Schmidt-Cassegrain scope we used, no drilling, filing, tapping, or any other intrusive modifications were needed. Everything fit as it should. However, I thought the plastic covers, while making for a cleaner appearance, were flimsy and didn't match the metal construction of the rest of the telescope. They looked like cheap add-on components.
     On the vintage Meade 2080 we used, the cover over the RA encoder stuck up enough that the telescope tube would no longer swing down through the forks. The end of the tube hit the cover, making it impossible to fold up the telescope to fit in the carrying case. However, JMI told us that on all other Schmidt-Cassegrain scopes, including newer models of 2080, this does not happen.
     My pet peeve with electronic add-ons is the tangle of cables that go along with such products. In the case of the NGC-MAX a cable runs from each of the two encoders into the computer box. Both cables use phone-jack connectors on the ends to ensure firm connections to the encoders. To help prevent the tangle, adhesive cable clips are supplied to keep the wires tucked along the fork arms and base. As a result, in actual use, the wires weren't bothersome. A couple of times in moving the scope from target to target, I forgot about the wires and rotated the scope 360 in RA, promptly wrapping the cables around the mount. It's a minor problem you have to watch.
     I also put the cables in a freezer for a day to see how they would fare in cold weather. They did stiffen up a little but remained pliable enough that they shouldn't cause a problem in winter. Batteries, however, would be a different story. In warm weather, I found the 9-volt battery lasted for five observing sessions of two hours each. This was with the display on full brightness, a worst case. With the display switched to the dimmest setting (suitable for a dark site), battery life would be extended. But in cold weather, battery life would be shortened considerably.

Observing, Robo-Style

     The best thing about the NGC-MAX is its ease of calibration. The first models of digital setting circles required you to spend half an hour each night inputting sidereal time, latitude and longitude, and then precisely polar aligning. So much for convenience! But the NGC-MAX and the other similar products on the market, as well as plain digital circles like the DSC-MAX, require only a simple sighting of two stars to get you going. You don't even need to polar align.
     Here's how it works. You set up the telescope, preferably with the polar axis pointed north. After turning on the NGC-MAX, you set the declination axis to 0, in other words pointed at the celestial equator. You use your regular setting circles for this. You do this and hit ENTER. It then asks you to align on a star. You can scroll the display through a selection of thirty 1st- and 2nd- magnitude stars. After selecting a suitable star, you center it in the field and again hit ENTER. The MAX responds with a "warp factor" essentially a measure of how far off the star is from where the MAX thinks it should be.
     After aligning on the first star you swing the telescope to a second alignment star at least 45 away from the fist and punch it in. That's all there is to it. I found that as long as I was searching for objects in the area of the sky around and between those two stars, the MAX always brought me to within 1/2 of the target. Swinging to other areas of the sky introduced greater errors, up to 2 or 3. The answer here was to recalibrate on another star in that section of the sky (there was always one available from the list). This dramatically increased the accuracy for that area.
     To test just how smart the NGC-MAX was, on one night I purposely pointed the polar axis toward the Big Dipper in the northwest. I then did the two-star alignment on Arcturus and Altair. The MAX still brought me to within 1/2 of the Ring Nebula (overhead) and M4 in Scorpius (due South). M13 (also nearly overhead) was dead center, but M81 and M82 in Ursa Major to the north were substantially off by 3 in RA and 1 in declination. Recalibrating on a new star in the north fixed this. In fact, the NGC-MAX will work even on altazimuth-mounted telescopes like Dobsonians. (But beware: You may be shunned at star parties by the observers who despise setting circles!)
     While polar alignment is not required, getting the telescope reasonably close to the Pole does help the MAX's accuracy around the sky. The critical calibration, however, is the initial calibration. After aligning on Arcturus and Vega, the Ring Nebula still ended up only 0.8 out in RA and 0.5 out in declination, showing that even the "dec.=0" setting is somewhat forgiving. But with the dec. axis set to -40 at the start, the scope ended up 13 away from the Ring not surpassingly, the MAX had been fooled.

The Many Modes of MAX

     Finding objects is the NGC-MAX's forte. You can use it in the straight "RA and Dec." mode where it will tell you the telescope's position as you move it around the sky. This is the extent of the capabilities of "dumb" digital setting circles. To find an object with them you must look up the coordinates in a reference book and move the scope so the digital readouts match the position. With the NGC-MAX, however, you can go one step further. You can switch to the "Catalog" mode and select one of the 8,000 objects programmed in its memory. When you then switch to the "Guide" mode, the display changes to an indication of how far away in degrees you are in RA and declination. You move the scope until the displays read 0 in both directions. When you get within 10 of the target the displays switch to an accuracy of 1/10th of a degree, making it easy to do the final aiming.
     One idiosyncrasy I found was that the magnitudes for objects in the Messier list were quite different than the magnitudes for the same objects in the NGC list. It looks like the Messier data came from the Sky Catalogue 2000.0 and the NGC data from the RNGC. A quick sampling through the MAX's lists turned up a few errors, such as NGC 281's being listed as an open cluster (it's a nebula) and NGC 1049's being listed as "unverified" (it's a globular cluster). Some bright planetary nebulae, such as NGC 1535, did not have any magnitudes listed, despite the fact the magnitudes are well known. These minor errors and omissions are present in the original Revised New General Catalog, and the NGC-MAX simply repeats them. In future editions of the MAX and other similar products, it would be nice to see them use the computerized NGC 2000.0 database it's more complete than the RNGC.
     Another neat feature is the "Identify" mode. Aim the telescope at a mystery object and it will tell you what it is. On command, the LED display can scroll from right to left with a message telling you the current object's name, magnitude, type, constellation (for some objects), and Sky Atlas 2000 chart number.
     You can also use the NGC-MAX to help polar align. After aligning on a star, it will then guide you over to Polaris. You then adjust the altitude and azimuth of the mount to get Polaris in view. This procedure compensates for the offset of Polaris from the true celestial pole and actually aims the scope at the pole. However, when I followed this process I found that although the MAX brought the scope close to the poles it was not close enough for critical applications. Checking the drift of a guidestar at high power, I found that after 10 minutes, the star had drifted off about 30 arcseconds in declination. Astrophotographers may still need to use their time-tested star-drift methods for accurate polar alignment.
     However, astrophotographers will appreciate the built-in timer. It counts up in seconds from zero, and keeps counting in the background even if you switch the MAX over to other modes.
     Deep-sky observers will also appreciate the user-definable objects. You can enter the coordinates (but not the names or catalog numbers) of up to 25 objects. In this way you can use the NGC-MAX to find deep-sky targets not in the RNGC or Messier catalog. For example, one night I entered that night's coordinates for Comet Levy, and the MAX located it precisely. Since the NGC-MAX control box can detach easily from the encoders and telescope, you can use it during the day at your desk to conveniently enter a selection of objects for the night's viewing.
     Finally, you may well wonder how all these functions are possible with only four buttons. The MODE button allows you to select various functions. The ENTER button executes a command. The UP and DOWN buttons scroll from one mode to another and from one object to another or increment the numerals from 0 to 9 when choosing an NGC or Messier object or a star from one of the catalogs. Since each button performs various functions depending on which mode you're in, the operation does take a little getting used to. But after a couple of nights, I found myself quite at home with the controls. The reason for the simple controls is for the ease of operation in the dark with gloves on, a design you soon come to appreciate. While units like the CAT look much more impressive, their complex array of buttons are more difficult to operate.
     However, the NGC-MAX, unlike the CAT, does not allow you to sort out deep-sky objects by search criteria. For example, you can't instruct the MAX to show you just Messier globular clusters brighter than 10th magnitude (or some other sorting). To devise a program of objects for a night's viewing, you still have to do a little homework selecting objects.

Do You Need One?

     At $829 the NGC-MAX is an expensive accessory. You certainly expect it to work well; in our case it did. Should you buy one? If you don't know the constellations or the identities of bright stars and don't have any idea of what objects are worth looking at, then even with the power of digital setting circles at your command you'll still be lost in the stars. And out $829.
     I feel that an accessory like the NGC-MAX is most useful for people with a solid understanding of the layout of the sky and some experience with deep-sky observing. If you've had a telescope for several years and finding that you're not using it much anymore, a unit like the NGC-MAX could be just the thing to rekindle your interest in observing. Perhaps tracking down the sky's "top ten" deep-sky targets is as far as you ever got; the NGC-MAX will take you much further into the deep-sky realm.
     Plus, there is a way to save money. You can now get most of the NGC-MAX's capabilities but with a more limited selection of objects in a new unit called the NGC MiniMAX. For about $200 less, it has 1,000 objects in its database, enough to include most deep-sky objects brighter than 12th magnitude. (Lumicon's Sky Vector II is a similar product.)
     Either in the Max or Mini forms, these smart digital setting circles can open up vast new stretches of the sky for a lot of observers. They're an expensive luxury, but using them can be a great deal of fun.