Konus 80mm v Synta 102mm
A CHANCE MEETING
By Antony McEwan
At a recent Highlands Astronomical Society Equipment Night, I was very happy to see, fully set up just a few feet along from my 127mm Maksutov, one of my first telescopes. It was a Konus Vista 80mm short tube refractor. It was mounted on the same photo tripod that I included when I sold it to its current owner and it even came out of the same foam lined aluminium carry case that I also parted company with about three years ago.
Naturally I went over and inspected the little yellow scope, remembering the great observing nights I had enjoyed with a scope that took two minutes to set up and could be carried, with tripod and eyepieces, in a small bag. The optical design of the scope is an 80mm achromatic doublet, with a focal length of 400mm, making it a fast f5 wide-field scope, not suitable for high powers, but giving rewarding low power views of star clusters, galaxies, comets and even the planets!
Anyway, after making contact with the Vista again, I started thinking about getting another short-tube refractor for those lovely wide views of the brighter deep sky objects that are often too big to fully appreciate in a 1500mm focal length Maksutov which gives quite a narrow field of view. Having experienced some fantastic views through another observing friend’s 102mm f5 scope, and appreciating the increase in light gathering performance over the 80mm model, I eventually decided to buy a SkyWatcher 102mm 500mm focal length achromatic refractor tube assembly.
Since owning the 80mm Vista, I have gone through an ETX 90 and onto a Synta 127mm Maksutov, my current main telescope. It is mounted on Synta’s Skyscan 2001 EQ3 mount, with dual axis drives added, and I had thoughts of mounting the 102mm refractor tube straight onto the Skyscan using the tube rings that came with the optical tube assembly. As mentioned before, the Vista had been mounted on a simple Miranda photographic tripod and had sometimes been used with a set of Pro-Optic deluxe slow-motion controls, mounted between the tripod head and the scopes ¼” x 20 mounting block.
The main aim of this article, then, is to give a comparison of my experiences as a relative beginner with the simply mounted 80mm Vista, against my new and updated wide-field set-up of Skywatcher 102mm on driven Skyscan EQ3. Both scopes are f5 achromats and I thought this might even provide some useful information for people trying to decide whether to buy an 80mm or 102mm tube assembly. In addition, I will state that both scopes were purchased new, from independent UK astronomical retailers, and that I have no association with, or interests in, either manufacturer.
Fly Me To The Moon
I remember when I first bought the Vista, I had been struggling with my very first telescope; an equatorially mounted Celestron Firstscope 114 reflector. The eq mount was too much for me to handle at that stage and it became so much of a struggle to try and find things to look at in the sky that I sold it and bought the friendly yellow Vista - a much more portable and easy to use package for my inexperienced hands and eyes! In contrast, no knowledge of complicated mountings was required for me to get the Vista up and running. I simply attached the base of the tube assembly to the head of my photo tripod, using the ¼” x 20 fixing block on the underside of the tube, and used the tilt and pan head of the tripod to slew this way and that to line up on whatever I wanted to look at. Simplicity itself. The Vista was supplied with a 6x30 finder in a dovetail mounting bracket, and my memories of the finder are that it gave a wide field and held its alignment very well, due to the locking screws which held the tube in place within the bracket, even when not attached to the main scope.
The package also included a 45' erect image prism diagonal and two eyepieces of, I think, 17mm and 10mm, giving 23x and 40x, as well as a 2x barlow. I had also bought a Pro-Optic 7.5mm plossl, so I had a range of magnifications of 23x, 40x, 46x, 53x, 80x and 106x. It is only with hindsight, and experience of higher budget eyepieces, I realise the limitations that were placed on my viewing by only using these, somewhat lacking, eyepieces. Certainly the Pro-Optic was far superior to the two Konus plossls, but I found that many different eyepieces outperformed the Konus Plossls. The 45' diagonal also limited my viewing comfort, as to view anything more than 45' above the horizon, I had to fully extend the central bar of the tripod and look upwards through the eyepiece, which was less than comfortable.
However, I owned this set-up for over a year and put it to a lot of use. I think the fact that it was so small and easy to set up helped a lot in introducing me to the stars, as I was able to carry the whole kit, including extra eyepieces, map, and seat, to many observing sites within walking distance of my house. Going by memory, I think the tube mounted on its tripod with diagonal, eyepiece and finder fitted, weighed about 8 or 9 pounds.
The first object I looked at through this set-up, on the night of its arrival, was the Moon. I remember it was about three quarters full and hanging in a fairly dusky sky. Needless to say I was very impressed and used all my eyepieces to view the terminator and zoom out to get the full wide field effect. I had been warned about false colour but at low powers (up to about 46x) I really didn't notice it much. Certainly it was more evident at 53x and upwards.
In the following weeks and months I discovered Jupiter and Saturn. I had never been able to get the Celestron lined up on them, so was very happy to see these wonderful planets in a scope! Belts were easily visible on Jupiter, using the 10mm and 7.5mm lenses, and I remember using 106x and getting a fair bit of detail, though the false colour made anything higher impossible. Saturn was very pretty to observe but I dont remember making out much detail on it. Of course, wide clusters such as the Pleiades and the Double Cluster stood out wonderfully in the little Vista, and I had my first views of M31, which showed up well, though dimly, across my field of view. I was also able to find M1, the Crab Nebula, with this scope, and make it out as a faint oval blob. The Dumbell Nebula showed some shape, with averted vision (see - I was learning tricks), and on one memorable night I finally found M33, the very faint galaxy in Triangulum. I was very pleased with that, as I had been unable to find it for the several nights previous.
With the 17mm I was getting a field of view of about 2 degrees, so finding and keeping these objects in my eyepiece got to be quite easy and enjoyable, and once I found the limits of the scope (and my expectations) I spent many happy nights with the Vista and map book. So, the Vista really helped me to learn my way around the sky. There was nothing complicated about it. I just took it out, plonked it down level, and started looking up!
Eventually, I started wanting more aperture and the ability to see these objects with more magnification, and so the Vista was passed on to another starting Astronomer in exchange for some cash to put towards my next scope - the Meade ETX 90RA.
A Step Up
Time passed. More observations were made, more scopes tried. Then I bought my Synta 127mm Maksutov on Skyscan 2001 EQ3 mount. Drives were added. Better eyepieces, with names like Meade, Televue and TAL, were added to my accessory case. But then my next wide field scope came to me; the Skywatcher 102mm f5 achromatic refractor tube assembly. This would be similar in many ways but different in some.
The basic optical system is the same. It's fast and achromatic but has a little more light gathering power, being able to catch stars just below magnitude 12 instead of the limit of magnitude 11 (ish) with the 80mm. The tube is a little bit longer, wider and heavier, but I think has a feel of being put together slightly better. Certainly the 2" focuser is tighter than the Vista’s and I now have access to using a 2" diagonal and eyepieces for ultra wide field viewing. This package also included two eyepieces (10mm and 20mm Plossls) and a 2x barlow, along with a 6x30 finder.
Attaching the tube to the Skyscan mount is simple and the whole package is very sturdy, though a lot heavier than the Vista on its simple lightweight tripod. In fact, this is a major difference - the 80mm could be put into a back-pack and taken on a long walk, used, and carried home no sweat, but that just isn't possible with the 102mm. It is possible to mount the 102 on a heavy-duty photo tripod but it would need to be a sturdy one to cope with the strain. My Velbon D-600 doesn't like it very much, besides which it's just a whole lot chunkier package than the 80mm, so I won't be taking the 102 on my holidays.
Having now used the 102mm a few times, I have to say that the sturdiness of the scope on the EQ3 and the functionality of the twin drives are a huge step up from the more basic set up of the 80mm Vista. I remember the Vista wobbled a bit, and at anything around 40x or higher it took a few seconds for the vibration caused by focusing, bumps, or the wind to die away. This doesn't wobble. Ever. It takes longer to set up and, of course, you have to polar align the mount and plug in the drives, but that's the trade-off for a sturdier kit.
The light gathering advantage is noticeable, as is the quality of the optics. As you would expect, deep sky objects such as M31, M33, M27 are all brighter and show more detail, and clusters such as the Double Cluster, and M35 in Gemini, reveal more stars. And, of course, it's easier to make out the extra detail because of the improved sturdiness of the mount.
I'm not going to compare the false colour qualities of the two scopes as it would not be fair for several reasons. I am using better quality eyepieces with the 102mm than I owned with the Vista, and the 102 is a brand new scope which makes use of the latest anti-reflection coatings which may or may not have been applied to a better standard than the Vista, which was "new" over three years ago. I'm sure that anyone reading this who has a little knowledge of refractors will be aware that a fast f5 achromatic refractor will begin to exhibit colour fringing on brighter objects as magnification is increased, and that this is accepted. What I can say is, that viewing Albireo through the 102, with a 9mm Ortho giving 55x, I noticed only the vivid gold and blue colours of the two component stars. At that magnification false colour was not an issue. I have also noticed that the view in the 102mm is quite sharp, almost to the edge, when using good quality eyepieces. That flatness does deteriorate when using high powers but when being used as a wide field scope it is quite pleasing. I seem to remember that the 80mm was not quite up to the same standard regarding field flatness, but I stress again that it was an older model when compared with the Synta, and I would like to see how the currently produced models fare.
Something else struck me which I should mention. As Mars is presenting itself very well at the moment, I couldn't resist a look at the Red Planet, but I did so expecting the worst - a blob of an indistinct orange-red glow. However, the 55x view was excellent! Very sharp and showed a hint of the ice cap! Hardly any glow. Barlowing it up to 110x showed more detail, just as sharp and hints of more surface detail. There was more surrounding glow but I made it go away by using my Baader Contrast Booster filter. Sure, it couldn't get rid of it completely but it improved the view enough to make it very rewarding for an f5 achromat. Again, I feel this is cheating a bit as I didn't have a Contrast Booster with the Vista, and I haven't tried it with any new 80mm f5 refractors yet, but it shows that even a fairly good achromatic image can be improved upon, if necessary.
I really enjoyed both of these scopes. Obviously, part of the enjoyment of the 80mm had to do with the fact that it was the first scope that I was really discovering things with, but it was also a very rewarding scope which didn't ask too much of me in the way of setting-up and care, and was always ready to take me skywards at a moment’s notice. The 102mm on EQ3 is just as rewarding, if not more so, and I think that this is partly due to the fact that I have had three years observing experience between the two scopes and am able to make good use of the extra light gathering ability. The improved mount is a blessing in that it is rock steady, but a curse in that it takes longer to set up and maintain. In some ways the two telescopes were very similar: Both scopes required a little in the way of DIY improvement to get the best out of them. The 80mm was better for a thorough blackening of the tube interior and draw tube, and the 102mm was similarly improved, with the draw-tube being blackened, and re-greasing the rack and pinion focuser. Both had good 6x30 finders, and nothing creaked, wobbled or lurched ominously on either scope. Both would be improved by buying a quality 90' mirror diagonal (though the Synta is supplied with a generic one). Both tube assemblies can be attached to 35mm cameras and used for astro or terrestrial photography, though this is not something I have tried, so I cannot make any claims about their quality or functionality in those roles. Finally, both telescopes were priced reasonably and both tube assemblies are now available, with accessories, for around the £160 mark, which may make the decision of which one to buy a little difficult. Of course, aperture usually wins, but what about portability? Ultimately, I have to summarise:
80mm Vista (on photo tripod):
Pros: Very light and easy to set up
Rewarding first-time views of many faint objects
Responds well to improved eyepieces
Cons: Limited to low-medium powers
Tripod mount a bit shaky (but could be EQ mounted)
102mm Synta (EQ-3):
Pros: Good light-gathering ability
Sturdier driven mount
Cons: Bigger, heavier, longer set-up time
Requires polar alignment for good tracking
So....the two scopes are laid out side by side and my good and bad experiences with them have been laid bare. I consider both scopes to be worthwhile purchases and although it may be hard to get a Konus Vista model now, the same type of scope is still produced by Celestron, Synta, et al. It's a great get-up-and-go scope, ready at a moment’s notice, and can easily be improved. The Synta 102 on EQ-3 I consider to be more of an all-rounder package, though it is still limited regarding magnification.
I hope this exercise hasn't seemed pointless or merely introspective, and hope that someone out there may actually find these hands-on experiences worth reading and noting. If nothing else, writing this has had an interesting side effect: I'm now looking for a 2nd hand 80mm!
Antony McEwan, Nov 2003