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by Tim Snowdon 07/07/12 | Email Author

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Takahashi Mewlon 210 Review.

With reference to the iOptron Mini Tower Pro and the Baader Mk V Binoviewer.

By Tim Snowdon

This review is primarily of the Takahashi Mewlon 210, but it also touches on the Baader MK V binoviewer and the iOptron MiniTower Pro. It is not just a review of the equipment, it is also my personal guide to getting the best out of your telescope, particularly, but not exclusively, mirror based scopes. This has been gained from 21 years observing, reading and testing manufacturersí hype, and discovering the truth for myself.

I said I would write this review (on CN forums) 20 months ago when I bought the scope, but decided I did not want to write one of those: Iím so excited about my new purchase reviews. I wanted to live with the scope over a yearís viewing before giving a more considered, and I hope, informed opinion.

First, a bit about my observing history and habits. I live in city of 500,000 in the UK so my skies are nowhere near dark; I am a visual observer with a passion for the planets and the moon. I also love open and globular clusters and occasionally look at fuzzies (if they are bright enough to make it through my light polluted skies). My history of scopes reads:

  • Bausch & Lomb 6000 SCT Ė pretty bad and cost £700 in 1989. When you think what you can get for just half this cost today it makes you realise how lucky we now are.

  • Carton 100mm F13 refractor Ė great planetary scope (I never saw false colour below 180x) but a very, very long tube.

  • Intes MN61 Ė wow what a scope! But unwieldy, heavy and not easy to use with binoviewers.

  • TMB 115 F7 Apo Ė a great apo, useable, well built, great optics, great focuser, light weight and compact (I reviewed this scope on CN)

  • Takahashi Mewlon 210 Ė read on......................

It took me a long time to learn that the best telescope is the one you use the most. Thatís why I eventually sold my wonderful Intes Mak Newtonian. †It used to take me an age to set it up on a bulky and heavy EQ6 mount; the effort often deterred me from bothering. It was also awkward to aim and use with a binoviewer. Optically it was TOP class, and if I had a permanent observatory an 8Ē Mak Newt would be on my wish list.

I then discovered the joys of using a premium 4.5 inch TMB apo on an un-driven atl-az mount (the wonderful AYO AOK mount). I had so much pleasure viewing through this set up; it had fantastic optics, was easy and quick to set up, and gave me great planetary views. The scope also had another significant benefit in that it cooled down very quickly. I would put it in my unheated conservatory about an hour before viewing. Fifteen minutes after taking it outside is was thermally stable and delivering great high power views.

After having it for two years though, I was really hankering to see more detail on planets and globular clusters. The problem was how to do this without going back to the days when I could not be bothered to set up my heavy and awkward gear. I was also very nervous about buying a short tubed catadioptric scope as I had fallen in love with the pin-point stars and high contrast obtained from a Mak Newt and an apo refractor.

Lots of research later, and a huge amount of advice from CN forum members (you know who you are, I am forever in your debt) and I decided to go for the Takahashi Mewlon 210. The other scopes I considered were:

  • Intes Micro 715D. Rumoured to have optics that are second to none, but significantly less aperture (35mm or 1.4inches) for the same price as the Tak. I would have gone for the 815 but it was too heavy and too expensive.

  • Orion Optics (UK) OMC200. An eight inch F20 scope with a very small central obstruction and a very long focal length of 4000mm. I decided against this as its focal length was too long for many open clusters and I knew I would take a huge hit on depreciation if I did not like it.

  • Celestron 9.25 SCT. Was this a real planet killer as some state? I just did not have enough confidence to be sure I would get a good one.

  • Intes Micro MN76. I know I have said negative things about the ease of use of Mak Newts but I well remember the optical quality of the six inch version of this scope. Bulk, cool down and difficult to use with binoviewers decided me against in it the end.

This left the Takahashi Mewlon 210. What appealed to me was the following: fantastic optical and mechanical reputation, compact and light, relatively quick cool down (more of which later) great with binoviewers and any easy resale with small depreciation if it did not work out.

I should point out that I am not one of those people who believe everything that Takahashi does is perfect. In fact, a previous Tak 5mm LE eyepiece I bought had decidedly poor contrast (this single negative experience would have stopped my buying the scope if I had not been able to speak to so many CN users about their experiences of the 210). After 6 months of research, I sold my apo (which really made me sweat; had I done the right thing?) and bought a new Takahashi.

After having my first scope destroyed in shipping (always buy through a good dealer who will support you through a trauma like this), I finally got the scope. Having never actually seen one in the flesh I was bowled over by the quality of fit and finish, this scope does give you real pride of ownership. The tube is a classy cream and the cast aluminium back is finished in Tak green. It even comes with its own engraved plate with its serial number. This shows that mine was the 18th scope built in 2010. This scope is so well built that Takahashi actually recommends that you use the finder scope as the handle!! In 20 months of doing this and I have not had to adjust it once Ė how do they do that?

My research on the CN forums had repeatedly warned me that collimation was critical with Mewlonís, and very difficult to achieve. So part of the deal I got from my supplier was to have the scope set up professionally. This was 100% worth doing as the scope arrived very well collimated, not perfect but I would say about 97%. Again in 20 months I have not had touch this once, it holds collimation perfectly, even when transported. Itís got to the point that I hardly even bother to check it as it never changes.

I have read some stories on CN of people really struggling with collimation with the Mewlons, apparently the collimation screws on the secondary are very tight. Tak say this is intentional so that when set up it stays set up. This certainly my experience. After-market quick adjust knobs are really not recommended for this scope.

Mounting the scope

At first I tried this scope on my old AYO AOK mount that had worked so brilliantly with my previous refractor. I discovered that it was much harder to use a manual mount with a short tube scope that gave little leverage to any hand driven movements. This could have been easily overcome by making a handle to control the mount, but by then I had other plans.

I had been attracted to the simplicity of the iOptron Minitower mounts, and when the Pro version came out I decided this would give me an easy to set up mount ideal for visual observations. What I love about this mount is its ridiculously simple set-up. My friendís Meade literally takes at least 5 times as long. With the iOptron I just level the mount with the special knobs designed to do this (I donít even need to do this as I have marked my observing area with marks to show where to put the tripod feet. If I do not change the tripod between viewing sessions the mount is already level). Point the arrow on the mount head towards approximate south, point the scope approximately vertically and select an easy to spot object, usually a planet. Press Goto and the scope swings to the selected object. As your initial south and vertical settings will not have been precise the scope will be some way off the target. Simple select Sync to Target and use the hand controller to centre the target in the truly superb Tak 7x50 finder, confirm, and thatís all you need to do to view. Do this on two or three objects and the pointing accuracy improves, but for MOST viewing single object alignment is perfect, nothing more needs to be done but enjoy the view.

One trick with this mount is to use Energizer AA lithium batteries (x8), four sets of these last me a year of observing (if you do lots of slewing I imagine you will use more than this), non lithium AA batteries are too affected by cold and the high drain used when slewing. So I have a fully computerised Goto mount with no power lead, no separate large battery, that can take scopes that weigh up to 33 pounds. Pointing accuracy is very good (but not perfect), if set up correctly. I have used this mount to view at up to 500x magnification, which was pushing it a bit, but 400x is no problem. At 500x you can see a little sawing movement in the observed object as the motors activate. This does not prevent observing but it can be seen. I love this mount, easy to carry, simple and quick to set up and very stable Ė it just gets out of the way. The only negative point is they use strange naming for double stars, so donít try looking up Albireo; they will give it some other name which is just plain daft. iOptron Ė take note.

The Mewlon 210

Anyway back to the scope, letís start with the tech stuff. The Takahashi Mewlon 210 is an 8.25 inch Dall Kirkham Cassegrain. It is different from a SCT (Celestron/Meade) or Maksutov in that it does not have a glass front corrector plate. This means it has only two mirrors to create the image and an open tube; the secondary being held in place by four spider vanes. Even though the front clear aperture of the scope is 210mm, the primary mirror is in fact 10mm larger than this at 220mm. This results in the outer 5mm of the mirror being masked by the opening of the scope. This ensures the best image quality as it is often the edge of a mirror that has optical problems. It shows a pretty committed stance to image quality by Takahashi, manufacturing a mirror and then reducing its aperture! I bet their marketing department hated the idea. Observers will love it. The tube weighs just over 16 pounds and comes with rail attached, and a sublime 7x50 finderscope that can be illuminated.

So letís cut to the chase: do I regret selling my wonderful apo as many people had predicted. NOT AT ALL. I love this scope so much that even when I had an opportunity to exchange it for a TEC 140 plus a very reasonable amount of cash (the 140 had been my dream scope for many years) I could not bring myself to do it!!! But my love for this scope was NOT love at first viewing; I had to learn how to get the best out of it. The beauty of a refractor is that it so easy to get the best out of them. A Cat/Cass takes more effort. †A Mewlon is a real performance telescope, and you need to learn how to get the best out of it, just like a Lamborghini!

Chill Out

When I first got the scope I was disappointed how bad my seeing had become. It is well known that larger aperture scopes are affected more by poor seeing than smaller scopes. As I had just nearly doubled the aperture of my scope I was expecting the seeing to be worse; but not as bad as it was. Then I read an article (on CN) that explained how to detect the difference between poor seeing and a scope that was not thermally stable, and it sounded like the problem I was having was more a cool down issue than seeing.

I had been putting the scope in an unheated conservatory (on average 3.5 degree C warmer than the outside temperature) about 1 hour before going outside, then expecting the scope to be ready to observe about 20 minutes after taking outside. The simple truth is this was not giving the nearly nine inch mirror enough time to cool.

So I went and bought a large plastic storage bin ($20), put some draft sealing foam around the top so the lid made a nice tight seal, lined it with foam and started putting the scope outside for at least two hours before observing. As the scope is in a water tight box I do not have to keep worrying about the changeable UK weather. This solution is so easy and cheap for any with a SCT, Maksutov or Cassegrain OTAís; if your scope is fork mounted then getting a box big enough might be challenging.

This simple idea transformed my viewing. I would now describe the seeing as only slightly worse than when I used a 4.5 inch scope. On my recent viewing of Mars I would put the scope out as soon as I got home and be viewing anything from 3 to 4 hours later. Doing this I could use 270x† on most evenings, 340x was useable on at least 1 in three evenings and on three great nights I pushed it to 450x and was still presented with a crisp edged globe with great detail and contrast. I even did a drawing one night as I did not want to forget what I had seen. Just to be clear here, my old TMB 115 was a great planetary scope, but the Mewlon showed massively more detail, this was not a case of splitting hairs; it was a no contest win for the Mewlon. It just shows that when you have quality and aperture you have a winning combination.

Once cooled in this way I have never had problems with the scope not being able to keep up with fast dropping temperatures. I coldest I have observed in was -7 degrees C, my wife thinks I am mad. I never use a dew shield and the scopeís optics have never been affected by dew, even when the outside of the scope is covered with moisture. I always observe without the pretty screw-in cover from the front of the secondary mirror, as this is something else to cool down and creates a sealed void that would further slow cooling. It also gives another surface to diffract light.

At the eyepiece

One of the things I had been warned about with this scope was coma distortion, which is inherent in the Dall-Kirkham design. Yet in my observing I have never been able to see it unless I go looking for it at the very edge of the eyepiece at lower powers, and even then it is mild. At powers over 150 it is not visible at all.

I was also warned about the diffraction spikes caused by the spider holding the secondary mirror. These can be prominent on very bright stars and less so on planets. If I am honest I wish they were not there, but you do get used to them, and I end up spending my time ogling all the detail you can see on the planet rather than observing the spikes. On bright stars they can even be rather attractive. On most stars, and globular clusters they are not visible at all.

I was told this scope would be a great visual scope, particularly for the planets, and it is. In particular the views I have had of Mars have been really breathtaking, with large amounts of recognisable detail, particularly Syrtis Major looking like an upside-down India. The polar caps look so different, the southern being soft-edged and diffuse, the northern gleaming like a sharp-edged jewel. Also, the 3D nature of the image is transfixing; you knew you were looking at a globe, not a disk.† A friend of mine (who has a well-collimated 8 inch SCT) wondered why he could not see all the surface detail visible in the Mewlon in his scope.

Jupiter is a mass of detail; it was fascinating to watch a tail of small vortices be consumed by the Great Red Spot. Also the view was now in colour! This was a real surprise to me and made the viewing so much more enjoyable and convincing. I presume this detection of colour by the eye is because the scope collects more light, but seeing all the different shades of brown and blue really improves the viewing experience.

Saturn is always a great target, even if it tends to stay the same most of the time (apart from ring angle). The Cassini division is always clearly visible (unless the seeing is disastrous), and far more shading is visible on the planet than I have ever seen in other scopes. I am currently enjoying the clear-edged shadow cast by the rings on the planet which helps make the already 3D image even more pronounced.

Uranus was a tiny clear blue disk with the faintest of banding running at an angle north to south. Its so cool to actually see the outer planets. Neptune is on my list for later this year.

With the Moon, the magnification just keeps going up (to 500x) giving you fantastically sharp and contrasty images; this scope was made for the moon. Nearly every time I start a new session viewing the moon my first view gives me a shock (unless the seeing is abysmal). The detail in craters, mountains and seas just jumps out at you, itís so 3D. When you combine this with fantastic contrast it keeps me observing for hours. The tonal subtleties are also outstanding, making viewing fascinating as subtle shading gives you a greater understanding of what you are observing, particularly in the seas. Comparing the view to the wonderful photos in Legaultís New Atlas of the Moon (a must for any lunar observer), I have often seen views that match and occasionally better his incredible photos. It is worth repeating, this scope is a visual lunar observerís dream.

Globular clusters have been transformed by nearly doubling the aperture over my old apo. Not only is the image so much brighter but the stars are pin points just like in my old refractor. No fuzzy blobs here. I love settling down with a cloth over my head (to stop my night vision being ruined by city lights) and just letting the cluster unfold as my eyes become more sensitive. It also great to be able to increase the power on globular clusters up to 400x without them becoming impossibly dim. Itís a great feeling to be able to see right into the heart of one of these balls of stars and imagine what the night sky would be like in a place where the star density is eight thousand times that of our location of space!!!

Open clusters are also great. M35 used to be my favourite but now some of the dimmer clusters look even better, again pin-point stars.

Finally a quick mention for the Orion Nebula. It hangs there like a giant bat, with just so much more detail and tonality than I ever got near to in my lovely old apo. The mixture of aperture and quality optics makes for a fantastic viewing experience.

Focusing & Binoviewing

The focusing on this scope is done by moving mirror, which enables the scope to come to focus with a binoviewer without any corrective optics. This allows you to get a low power of 100x with a 24mm Panoptic, enough to observe M35. With a 2 inch diagonal you could get as low as 60x with a 41mm Panoptic.

Moving mirror focusing gives you great flexibility but it can never be as smooth and precise as a Crayford focuser - you are sliding a mirror thatís part of the optical chain, after all. I have often considered getting a short Crayford focuser but have not gone down that route as yet as I do not want to lose back focus (more of which later). So I emailed ScopeStuff and asked them if they could make me a Fine Focus Knob for the Mewlon. They were really helpful and once I had given them the exact size of the focusing knob (28.7mm) they made me a custom one for little extra cost.

This oversize knob slips over the rubber knurled ring on the Tak focuser. It was a bit tight on mine and I needed to spend 20 minutes enlarging the hole by sanding it with fine wet and dry paper. This had the advantage of enabling me to size it very precisely and it now sits snugly over the focuser near the scope. It is a friction fit not requiring glue or a locking screw, and has never slipped. As you can see it just clears the visual back by about 1mm. The system gives me a simplified two-speed focuser; the original knob for quick focusing and large one for fine focusing. I estimate that I can make focus adjustments about 60 to 70% finer with the larger knob than with the original. Itís certainly not as good as a Feathertouch, but itís a cheap upgrade that works. It also looks rather cool; in a mad scientist sort of way!

There is some image shift with the scope: at 275x Mars moves about 1x its disc size, but I find this no problem as I am a visual observer.

The scope comes with quite a long (and pretty basic) visual back. As I wanted to save as much in-focus distance as possible (so my binoviewer would come to focus with the mirrors as near as possible to their optical prime focus position), I removed this and bought a Mewlon to SCT thread adaptor, a Baader SCT to T2 low profile adaptor that screws directly into my Baader diagonal (from Teleskop Express). I estimate this saved nearly 20mm of back focus.

Takahashi sent me the following diagram that shows the prime focus of the scope.

Itís now time to give a plug to binoviewers. For me they transformed my viewing, particularly on planets. I first had a cheap Chinese one, then a standard Denkmeier, then I invested in the Baader Mk V. It is the best accessory I have ever bought. I know itís very expensive, but looking at Jupiter through the Baader for the first time was like having a veil removed from my view (I exaggerate, but not by much). The clarity offered by this binoviewer, particularly when mated with the Baader Zeiss prism diagonal, is worth every penny of its not inconsiderable cost. I use all three Glasspath correctors, 1.25, 1.7 and 2.6, and find them all of equal quality, even though some people say the 2.6 is not as good as the others. You might have noticed that I keep mentioning how 3D the images I get from this scope are, this is in no small part due to the Baader Binoviewer. Occasionally I will view one eyed and I am horrified by how little I can see compared to two eyes.

I use an eclectic range of eyepieces:

GSO 32mm Plossls - with T2 thread for my rare attempts at imaging. Surprisingly good eyepieces.

Zeiss 25mm Aspheric Triplet Orthos - microscope eyepieces but brilliant contrast and lack of flare.

Pentax XW 20mm Ė totally brilliant (even on planets) but rather big and heavy for binoviewers and may have to go as they unbalance the scope.

Televue 17mm and 21mm Plossls Ė very nice and donít have the horrible eye-guards or cut-outs of the current TV plossls.

Badder 12.5 Ortho Ė lovely eyepiece, very much underrated. Such a shame they are now out of production.

Conclusion

Two years ago I regarded myself as a refractor nut. Selling my TMB apo was bordering on the traumatic, I am still surprised I did it. But I am now DELIGHTED that I did. The Takahashi Mewlon is a real performance telescope, but you will only get the best from it if you take cool down seriously, as you should with all larger mirror based scopes. THEN IT IS BRILLIANT, showing way more detail than my old 4.5 inch apo on all targets, for about the same cost!

If you want to learn more about the importance of cooling down your scope I recommend you go to Cats & Casses in the CN forum, click on Links of interest and the Best of Cats & Casses, and select How to get the best from your CAT (cooling issues).

So now the toughest test of any telescope, after having it for 20 months am I hankering after another scope or am I finally satisfied? As much as I love my Mewlon 210, I do want to change it; I now want a Mewlon 250! Unfortunately my bank manager wonít let me!

Clear skyís.

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