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INTES MICRO ALTER M500 vs. ORION ED80: Clash of the Bantamweight Scopes

Posted by ANJAL SHARMA   06/12/2006 12:00AM

INTES MICRO ALTER M500 vs. ORION ED80: Clash of the Bantamweight Scopes
Disclaimer: I have no vested interest in any of the scope or equipment manufacturers discussed in this article. All equipment described in this article was obtained through normal commercial channels.

Through a set of rather fortunate circumstances, I came into possession of examples of optically fine specimens of these two scopes. Having had a chance to look at, through and photograph the heavens using these two scopes, I was able to compare these scopes and draw some conclusions, which appeared to be worthy of sharing with the amateur astronomy community.
There is no other reason for comparing these two scopes, except that I owned both of these. This is a subjective, purely non-scientific review and in large part reflects my own biases. Since I had only one mount, the technique employed was that I’d mount a scope, observe an object, dismount that scope, replace with the other scope and compare my observations before moving on to the next object. I just observed and took rudimentary notes. A final point to note is that in many cases planetary and deepsky imaging comparison sessions were not done on the same night.

In this corner, wearing gunmetal grey tights, weighing in at 5.69 lbs., the undisputed crowd-pleasing bantamweight that packs a heavyweight punch, the reigning small apo price to performance ratio champ….. ORION “THE APO” ED80!! In the far corner, wearing pebble white tights, weighing in at 7.26 lbs., the lean-mean-fighting machine from Russia, the contender with a ferocious high-power (pun-intended) uppercut……. INTES ALTER “THE MAK” M500!! And so it begins…yet another small scope shootout. Step right up folks, and place your bets.

Let me just say that the optical quality of both these scopes is outstanding, with the M500’s being just slightly better numbers-wise. In practice, during visual and photographic use I can’t tell the difference in optical quality. Another thing that I have noted is that the highest rated magnification of both these scopes is a bit of an underestimate. I’ve been able to push the M500 to about 75X per inch on nights of super steady seeing (we sometimes get those here in southeast Texas, but not as frequently as I would like) before the image began to break down. The ED80 on the other hand is slightly less tolerant of stupid powers, and tops out at around 70X per inch.

Winner: M500 by a slim margin.

Both scopes are incredibly lightweight, and compact. While weight-wise the ED80 is about a couple pounds lighter, the M500 is more compact lengthwise. I like the M500’s carrying handle, because mounting and dismounting in the dark is a snap. Now even though the ED80 doesn’t come equipped with a carrying handle, the approximately 100 mm diameter of the ED80 tube allows it be easily held with a single hand, making it equally easy to mount and dismount in the dark. Both scopes would fit in a small carry on bag and so are essentially equal in terms of their airline portability.

Result: Tie.

Neither the ED80 nor the M500 are likely to win any beauty contests in terms of appearance. I like the paint job and overall fit and finish of both scopes about equally, as it is about what you can expect for the money. The M500 has a real solid look and feel, and it’s truly built like a tank…..typical Russian over-engineering. If you’re out observing in the dark woods, and a hungry wolf tries to eat you, use this scope to save yourself. A gentle tap on the wolf’s head with this scope, and he’s down for the count. The M500 walks away from the encounter unscathed. The ED80 in my opinion just doesn’t seem to be as solidly built as the M500. I’m constantly worried about its fate were I to drop it.

Winner: M500.

The ED80 wins hands down in the focusing department, because I absolutely love its smooth Crayford focuser. It has that definite snap-to-focus quality and zero image shift that refractors are renowned for. No rocking back and forth to know if you’re at best focus. You just know when you’re there. In contrast, the M500 uses the usual moving primary mirror. The focus knob is a lot stiffer to turn than in my old Nexstar 8i XLT, or my newer C8 XLT. To its credit, there’s almost no image shift when focusing the M500. However, I usually have to rock back and forth inside and outside of focus slightly to determine the point of best focus with the M500.

Winner: ED80 by a wide margin.

The ED80 wins in this department hands down. The typical cool-down time for the M500 in my experience is roughly 3 to 4 times that of the ED80 in minutes. This is to be expected, because of the larger number of optical surfaces on the M500. Its thick meniscus corrector lens doesn’t help either. The ED80 is a great grab-n-go scope. The M500, well…not so much.

Winner: ED80 by a wide margin.

Both scopes are outstanding visual performers. One would expect that the M500 would win in this department simply because of its larger aperture. However, the situation is a more complex. The ED80 excels at providing superb wide-field vistas of star fields. It’s is also an extremely decent lunar and planetary performer. I’m surprised at how much magnification can be thrown at this little guy. False color is very well controlled. I can’t see any false color visually on most bright objects. About the only things I have noted are a bit of a purple fringe when viewing Venus and Sirius. There’s no false color on Luna that I can detect. From dark skies it provides stunning views of the brighter DSOs. My personal favorites are the North American Nebula, the Double Cluster, the Andromeda Galaxy, the Orion Nebula, the Pleiades and the Lagoon/Trifid Complex. These just seem to float in velvety black space framed by perfectly pin-pointy stars. The field of view is very generous, and I can easily fit both cluster components in the Double cluster into the somewhat constricted 50 degree view offered by a regular 32 mm Sirius Plossl. Star colors are vividly defined. Alberio is my favorite double star to view with this scope. In terms of visual color temperature, the view from this scope tends to be cooler than through the M500. On axis sharpness is superb. Contrast is excellent and stray light is well controlled by the internal baffles. This is undoubtedly a very fine 80mm scope.
The situation is somewhat different for the M500. This scope delivers true “Apo” visual performance. I’ve never seen any false color on anything viewed through this guy. I’d have to say that it performs comparably to say a 90mm or perhaps a 100 mm apochromatic scope. The field of view is significantly narrower for this scope compared to the ED80. I can barely fit both components of the double cluster into the field of view of a 32 mm Plossl with this scope. The resolution and sharpness of this scope are outstanding. However, stars aren’t quite pinpoints through this scope. They have a bit of a blob like character. It’s not distracting, just a different feel to the view compared to the ED80. The contrast is excellent, and the internal baffles eliminate stray light very effectively. Of course its aperture is more than that of the ED80 and so it provides brighter views of many DSO which are at the limit of detection with the ED80. Its resolution is better.
As a specific example, I never tire of comparing the view of the trapezium and its environs in the Orion nebula with the M500 and the ED80. On average nights, the ED80 shows four stars at all times in the trapezium. On the same night the M500 will usually steadily resolve four stars and a fifth star will resolve from time to time. On nights of exceptional seeing, the ED80 will resolve four stars clearly and the fifth star will pop in from time to time. On the same night the M500 will clearly resolve five stars in the trapezium. Also, the column of dark dust which juts into the trapezium will have finer resolution through the M500 than through the ED80. Knot structure and wispiness in this dust column will be easier to see through the M500 than through the ED80. However, the visual punch is undoubtedly higher through the ED80. The ED80 will resolve M13 into about 50% of its core visually. The M500 on the other hand resolves M13 right into its core. However, the stereoscopic cues provided to your eye from the view through the ED80 are significantly larger than those through the M500, making the view of M13 appear to be much more like a three dimensional fuzz-ball through the ED80 (even in Cyclops mode). In terms of color temperature the M500 provides warmer views compared to the ED80. Star color saturation is slightly lower with the M500 than with the ED80. So yes, in terms of resolution and light gathering capability, the M500 wins, but the visual punch and emotional response factor appears to be definitely higher for the ED80.
What about planetary performance? Well, here the M500 delivers a better experience because of its larger aperture, better resolution and to a small extent, better color correction. As a specific example, I have compared the performance of both scopes on Jupiter. Visually with the ED80, the planet’s disc is a distinct whitish pastel shade in color and appears more three dimensional. On average nights the ED80 will show at least two of the main bands and polar darkenings well. The bands themselves will have a mottled appearance, and upon careful examination will reveal spots and swirls within them. The bands will usually have a distinctly reddish appearance. The GRS through the ED80 will appear to be a salmon colored eye-like shape within one of the main bands. With careful examination, the edges of the eye will have some mottling and a slightly darker hue than the center. On the other hand, the M500 will show a slightly flatter (less 3-D in appearance) circular planetary disc, which appears to be a bit more yellowish pastel in color. On average nights the M500 will show at least four bands on the planets surface. The main equatorial bands will have a significantly more mottled appearance, and clear evidence of swirls and spots. Spot shape will be easier to discern with some spots appearing to be circular while others appearing to be more elongated. The band color will be significantly more reddish in appearance through the M500. The polar darkenings will also appear to be somewhat more mottled in appearance. The GRS will appear to be a bit more reddish salmon in color, and its edges will clearly have a significantly more mottled appearance. Some detail will also be seen within the GRS, particularly the central circular swirl which will be slightly darker than the surrounding reddish salmon. On Saturn, both scopes comport themselves well, particularly the M500 where Cassini, and the equatorial band is usually easier to see at lower powers. The planetary disc shadow on the rings is easier to see with the M500 but the 3-D appearance is more pronounced with the ED80. These observations are at comparable magnifications. Oh yeah, as expected, higher powers make the planetary image appear to go dim in a hurry on the ED80, unlike on the M500. When it comes to shadow transits I like to use the M500 more than the ED80, because the shadow is easier to see and more distinct at the same power.
This is a tough one, folks. I’m going to call this a tie. If you want a rich field scope to sweep the Milky Way, and like to fit extended DSOs into the field of view go with the ED80. If however, you want higher resolution and higher magnification, such as required for careful planetary study, go with the M500. Let me just say though, that either scope will serve you well as a purely visual instrument.

Winner: Tie.


The performance of both scopes in terms of imaging, mirrors their visual performance. DSO imaging using a Canon Digital Rebel is a more satisfying experience with the ED80, not only because of the inherently wider vista captured, but also because of its faster focal ratio. The other point in its favor is that in conjunction with the Digital Rebel, a 0.6X focal reducer can be used on the ED80 providing an even faster focal ratio. However, for planetary imaging with a Toucam Pro II webcam using QCfocus, the M500 wins because of its better light gathering ability and better resolution.
As a specific example, the images (taken with a Digital Rebel) below show what can be expected when imaging the Lagoon/Trifid complex with the ED80 and the M500. Note the wider field of view with the ED80 where both the Lagoon and the Trifid can be easily fit into the same image.

Similarly, the images of M13 below emphasize the difference in field of view as well as overall feel and look of stars through these scopes.

Exposure times are shorter with the ED80 at prime focus or using a focal reducer therefore the mount is taxed less. With the M500 on the other hand, since the focal ratio is larger, and it is not possible to use a 0.6X focal reducer without severe vignetting at the Digital Rebel’s sensor, the mount is taxed more and for anything more than reasonably short exposures, careful guiding becomes necessary. On the other hand a 0.6 focal reducer works well with the ED80 for an effective fast focal ratio of f/4.7. Even short exposures can capture faint nebulosity as shown in this image of the Pleiades. That the field of view is generous at f/4.7 can also be seen in the image of the Andromeda galaxy below where it can be completely captured with room to spare.

A wide field image fitting the entire Pleiades cluster or the Andromeda galaxy like above would not be possible with the M500 unless a mosaic of images were stitched together. Therefore, with the 0.6X reducer, the ED80 performs almost like a (dare I say it?) poor man’s FSQ (FSQ owners, I apologize profusely for my blasphemy).
In terms of planetary imaging, the situation is reversed, with the M500 emerging as the better scope. This is because for webcam planetary imaging, high magnifications are desirable, and the M500 is more suited to this role. My webcam of choice used for this aspect of imaging comparison was the Philips Toucam Pro II. I used QCfocus to obtain avi movies of the planets (~1500 – 1800 frames per movie) and used Registax to stack the sharpest frames from the movies (~150 – 200 frames per movie) into a single sharp image. Wavelet processing was then used to enhance detail in the images. Using a 2X Barlow, the M500 was at f/20, but the ED80 was at f/15.
First up is a comparison of Jupiter shown below, and it is easy to see that the image from the M500 is significantly higher in resolution. Note also the increased magnification which the M500 tolerates easily. I lucked out with these images, as I had a rare night of excellent seeing when these were captured.

Similarly a comparison of images of Saturn follows the same trend, namely larger image scale and a bit better resolution from the M500.

This again is a murky situation. For planetary imaging the M500 emerges as the winner, but on deepsky imaging particularly for widefield imaging, the ED80 is the clear winner. I will call this a tie.

Winner: Tie.


Fortunately or unfortunately, it appears that there is no clear victor in this contest. In different usage scenarios, one scope may be a better choice than the other. For grab and go observing, or for use as a fast widefield deepsky astrograph the ED80 clearly is the better choice. However, for planetary observation (with good cool-down and under good seeing conditions) and webcam planetary and lunar imaging, the M500 wins.
Okay, so you still want to know who won? My personal interest is widefield deepsky astrophotography, so when the time came to choose between the ED80 and the M500, I kept the ED80 and sold the M500 in favor of a larger aperture scope.