ASTRONOMY Tests the NGC-MAX
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
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
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 360º 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.
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 45º 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 1/2º of the target. Swinging to other areas of the
sky introduced greater errors, up to 2º or 3º. 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
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 1/2º 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 3º in RA and 1º 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 0.8º out in
RA and 0.5º out in declination, showing that even the "dec.=0"
setting is somewhat forgiving. But with the dec. axis set to -40º at the start,
the scope ended up 13º away from the Ring — not surpassingly, the MAX had
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
10º 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
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