My two tweets from Astrofest which appeared in a Google search. Click for larger image
Never let it be said that fate (perhaps that should be temptation) does not play the long game. Shortly before purchasing the APM LZOS 130 F/9.2 triplet apo refractor in 2018 I Googled the scope and two of my own tweets from Astrofest in 2015 and 2016 appeared in the search results professing that were I to add a fourth LZOS refractor to my collection (already owning the 105 f/6.2, the 115 f/7 and the 180 f/7) it would be this one. Destiny came knocking at the end of February when I received an email from Rupert Smith at Astrograph (the UK distributor for APM) acting as my serpent in the telescope apple tree with discounted offers on the latest production from LZOS which included several lenses for this rather desirable scope. It did not take many days before I agreed to purchase this scope and select a lens from the those on offer.
Who are LZOS and the APM/TMB Relationship?
Located in the town of Lytkarino a few kilometres southeast of Moscow, LZOS (Lytkarino Zavod Optychisovo Sticklo – translates as Lytkarino Optical Glass Works) was founded in 1934 to manufacture high end optics for military and research use. While part of the Russian military industrial complex, it also operated as a Zeiss subcontractor for commercial optics and until recent geopolitical events, continued to offer high end telescope optics to the global amateur community. Unlike virtually all other telescope companies, LZOS manufacture the optical glass used in their telescope lenses as well as fabricating the lens cells which allows them to control the entire optical assembly process. LZOS produce their own extra-low dispersion glass, OK-4 (and matching mating elements), which has very similar optical properties as the well-known O’Hara produced FPL-53, though they are able to produce blanks in far larger sizes which allows LZOS to offer triplet refractors of up to 20” diameter.
Thomas M Back of TMB Optical had a love affair with astronomy which started as a child aged 8 after the receiving a small telescope for Christmas. He also developed a serious interest in optics becoming a prolific designer of telescope objectives and eyepieces. He started the TMB optical business in the late 90s in partnership with APM in Germany, selling high end refractors which featured lenses of his design fabricated in Russia, optical tubes from Germany and focusers from Starlight Instruments in the US.
Owned by Markus Ludes, APM was founded in 1990 offering a range of reflecting and refracting telescopes include large research grade instruments to observatories around the world. They became the exclusive worldwide agent for LZOS made, TMB designed lenses in 1998. Sadly, Thomas passed away aged only 50 in 2007 with APM retaining the rights to his designs which they continued to offer in APM branded scopes.
The APM LZOS 130 at Astrocamp in Wales waiting for darkness to fall
The history of the TMB LZOS 130 f/9.2 (and some controversy)
Feel free to skip this bit if you are not interested but I thought the history was quite fascinating and who doesn’t like a little controversy? Looking at the history of the LZOS 130 F9.2 leads you back to a rather special scope (among many special scopes) from Astrophysics Inc. From around 1991 to 1995 the company offered the 130 f/8 EDT (meaning ED Triplet). In 1998, the model came back into production but was slightly iterated to be the 130 f/8.35 EDT. Effectively, it was thought of as the middle piece of the larger 155 f/7 EDF (they both have the same 1,085mm focal length). I believe to avoid confusion between models, the EDT appellation was kept. Tom Back himself stated “what a sweet telescope” in his article on the history of Astrophysics lenses which indicated in Back’s mind, to that point in time for visual observers that Astrophysics had produced no finer scope than this. A few lucky individuals received scopes in a couple of runs (perhaps only 40-60 were produced) through 2002. However, among those who did not receive a 130 f/8.35 were a couple of good customers of TMB who suggested he should design a super planetary 5” scope as the successor. TMB took up the challenge in 2003.
Reportedly, TMB submitted 4 different designs for this scope to APM and LZOS ranging from f/9 to f/ 9.25 (initially it was believed LOMO may fabricate the lens with glass supplied by LZOS) and it was up to them which to produce but the essence of the scope was a 130mm f/9.X (up to 1,202mm focal length). I already owned the TMB 115 f/7 in 2004 and was lurking around the Yahoo TMB group (sadly now lost after they were all closed) and recall reading a very exited Markus Ludes at APM sending a message to Tom Back after the first run of lenses were delivered stating that the star tests of each were incredible, and even Thomas would find it impossible to tell apart each scope regardless of the measured strehl ratio. Back did retort (after asserting that is how he designed them with a focal ratio that would have no visual aberration, limited only by seeing) that he would take Markus up on that and might be able to see a difference, but he would not bet that he could. And he stated he has never said that about any optic by any telescope maker.
Now for the controversy (at least in some corners of the internet). A few individuals have suggested there is a question as to whether LZOS actually put into production the TMB design or one of their own. The initial face plates did not include the usual “T.M.B Design” engraving and stated f/9 (as well as on the test certificate). The belief the lens may be f/9 is also not helped by the product number of the lens in the APM catalogue being the 130/1170 which would imply that it is f/9. Someone has claimed to have an email (never posted as far as I can find but said to be sent in June 2005) that Tom Back was angry that his lens design was not used and only discovered this when he went to design a dedicated field flattener for it.
Taking each in turn, the decision not to engrave the usual T.M.B Design would seem to be strange and is compelling to this narrative. The stated f/9 on the lens faceplate and test certificate would not be the first example of a scope not stating the precise focal length. The initial run of the aforementioned Astrophysics 130 f.8.35 EDT stated f/8 so it is hard to make conclusions from that. One could certainly believe that for simplicity APM have used the 1170 in the product number to match the implied focal length of the engraving and certificates. The logo graphic on the dew shield states 130-1200. Several experienced observers have measured the focal length of their scopes and found ranges of 1202-1216mm (each production run needs be modified to reflect the glass melt data so slight variations would be expected for high-end refractors away from the prescribed design to maximise performance over hitting a specified focal length). More on that later. The statement about an email is at best a secondary historical source without production of said email. Several individuals who pushed TMB to design the scope and took delivery of the first lens run are adamant it is a TMB design though this can only be considered a secondary source as well (though one shared lens schematics which were required as he was making his own OTA and clearly needed the focal length – that is a primary historical source). In a post in 2016, someone describing themselves as a close friend of TMB stated it was Tom’s design and that he had confirmed that in conversation with Markus at APM five or six years earlier. Compelling but without a recording, that could only be considered a secondary source as well.
The most convincing counterargument I have found is a Cloudy Nights post from 24 September 2006 by Thomas Back himself titled “What is a TMB? A little history.”
Tom Back lists all the optics he has designed that were at that point being sold. One of the scopes is the TMB 130 F/9.25 (1,202mm focal length). By this time TMB was very ill and had to ask moderators to lock the thread shortly after posting as he was unable to keep responding to well-wishers so it would seem he was hardly in a position to be designing a flattener for the scope at that time so this statement would seem to be well after the alleged email expressing anger that his design was not used yet he was still asserting it was his design. Perhaps an element of deference to a man who contributed a tremendous amount to our hobby, both as an accomplished amateur astronomer and skilled designer, but that statement sways it for me, and I choose to believe it is his design.
The OTA
Those familiar with the APM LZOS offering will know that the optical tubes are made of Kruppax-50 (a phenolic resin impregnated paper composite) which has an almost magical ability to repel dew, finished with a deep cream white slight gloss paint. Knife edge baffles are often held in place by an internal frame (as seen in the 2019 rebuild of my LZOS 115 f/7 which I commissioned for the scope’s 15th birthday).
The APM LZOS 130 using a United Optics aluminimum tube which is very well machined and finished in a white powder coat.
For the round of scopes offered that I purchased, the lens came housed in an aluminium alloy tube made by United Optics in China. The machining is excellent with threads used rather than grub screws to attach components and four knife-edge baffles (I would have expected more in a scope this long, but I can see that models sold in the LW tubes as far back as 2006 also had four) are machined inside the tube which is painted flat black. The external finish is a white powder coat. I do not think it looks quite as nice as the traditional APM tubes, not that it matters in the dark. The lens cap also threaded onto the dew shield but was thin with no handle making it difficult to hold (especially with cold hands or when damp) so I had APM fabricate a more traditional slide on cap.
Perhaps unsurprisingly with a c.1,200mm focal length, this is a long scope, even at transportation length it measures 1,060mm though with the supplied tube rings, Losmandy D-Plate, and handle (which is so useful) it only tips the scales at 11.3kg which I have found easy to carry around and is relatively well balanced unlike some of my refractors which can be very front heavy. The length of the scope certainly creates a beautiful profile, harking back to the long-focus achromatic refractors of yesteryear. To butcher a quote from a famous Jedi Knight, “it appears like an elegant telescope from a more civilised age.”
There may only by 25mm difference in aperture, but the comparison of transportation length between the 105 f/6.2 which is airline portable and the 130 f/9.2 is quite something. However, the 105 achieves its compact length with a long sliding drawtube when in use.
I would note that while the OTA diameter is 141mm, the dew shield is somewhat oversized, extending to a 178mm diameter. I use an Oklap 150/1200 refractor bag to transport the scope which is meant for 150mm f/8 scopes and while the length has 10cm or more to spare, I can only just zip up the bag because of the height of the scope in its rings with that dew shield dimension and must remove the handle.
The focuser
Historically, APM has offered LZOS scopes with Starlight Instrument Feathertouch focusers which hardly need an introduction. Widely regarded to be the finest focusers available, a variety of models are available whether it is a two-inch model on a sliding drawtube (as seen on my 105/650) which keeps transportation length down and reduces weight, or one of the beefier models of three-inch (now on my rebuilt 115/805) or the massive 3.5” feathertouch (on my 180/1260) which is a work of art (9kg load capacity) and the finest focuser I have ever used. All three have a premium price with the latter costing over £1,100 (including VAT) at time of review. As part of the reduced price offering of my scope, it came with an APM designed 3.7” ZTA rack-and-pinion focuser with 1:10 reduction (current cost is around €500 excluding VAT). The unit weighs 2.04kg (2.5kg with rotation adaptor) and the drawtube extends 98mm (clear aperture of 102mm which means medium-format cameras would be covered without vignetting and is compatible with APM reducers and flatteners) with an etched graduated scale. The focuser benefits from a self-centring 2” adaptor which ensures that accessories such as a diagonal are clamped on axis with no risk of marring due to the absence of set screws. I count 10 small baffles inside the focuser, followed by a section of micro-baffles all of which is coloured flat black to minimise stray light reducing contrast.
Comparison of the focuser fully racked in and extended showing the 98mm of focus travel.
While not directly comparing the focuser to a Feathertouch, there is an implication of comparability given they are referenced on the APM webpage but as a more reasonably priced alternative. So how does it perform? In short, very well. It does not quite have the absolute precision feel of the 3.5” Feathertouch, but the focus is very smooth and backlash is not evident until well above 300x. The focuser can be rotated by 360o to allow framing of targets. This is done by loosening a knurled retaining screw (which I found very useful at outreach when someone particularly short comes along) and upon tightening there is virtually no image shift. It also performs well under load, never once slipping when holding a 21mm Ethos in a 2x Powermate on top of a 2” diagonal (combined weight in excess of 2kg / 4.4lbs) and tension is easily adjusted by a small nut under the pinion (payload capacity is stated as 9kg).
The ZTA focuser has a large fine focus knob which is easy to use when wearing gloves.
The ZTA focuser uses the same adaptor plates as Feathertouch so upgrades are relatively straight forward. I may do so in the future but honestly for visual use, it would be an unnecessary expense.
Details on flatteners and focal reducers
While I am a visual only astronomer, and I would argue this scope is very much targeted at that userbase, the 130-1200 is compatible with (including those with the ZTA focuser) the optimised APM Model 1 flattener and the Massimo Riccardi designed APM reducer which decreases focal length by 0.75x a much more acceptable photographic speed of around f/6.9. In that regard, if you like to have a foot in both camps of visual and astrophotography, this scope plus reducer could be a perfect combo, though the length and associated larger turning moment will mean a more robust mounting solution would be needed in comparison to the 130 f/6 LZOS offering for example.
The lens
With 25 years of delivering optics to the amateur astronomy community via the TMB/APM relationship (and much more as fabricators of Zeiss optics), LZOS are known to be among the top tier of refractor lens makers. The quality of the glass, the manufacture of the lens elements as well as the fully-collimatable temperature compensating lens cell are what would be expected from a premium telescope offering.
The lens design is a triplet with a central, low dispersion OK-4 glass element which is mated with two elements of special dense crown glass known as OF-1 (though I would note that a TMB FAQ indicated two different mating elements were used so there may be a third glass used and I cannot find the original source for OF-1 only claim despite mentioning in my other LZOS reviews) which was specifically designed to work with OK-4. A small air-spacing is employed along with different internal radii to control optical aberrations including sphero-chromatism. The coatings are smoothly applied and exhibit a deep blue hue that is very similar to both my 115 and 180 (though the 105 shows deep blue/violet) and reflections are extremely muted (APM state that light transmission is above 96%) with the lens almost vanishing at certain viewing angles.
The business end. The LZOS made 130mm triplet apo lens.
My one criticism is the same as for other LZOS lenses. The cell seems over engineered and disproportionally heavy compared to some other manufacturers. The cell is made from steel and is very robust. I have travelled over awful terrain with my 105 which has bounced the scope around and it has held collimation perfectly. However, the long tube and large focuser does help to balance this scope at a sensible point on the OTA.
Obviously dependent on temperature differentials, but cool down time is starting to increase now we are in the 5” scope class (there is a lot more glass than the one-inch increase might initially suggest). My 105 cools quickly whereas this scope may take an hour or more if the difference between warm home and cold night-time is substantial.
What is the Focal length?
If you read the history of the LZOS 130, you know certain corners of the internet ask questions about the actual focal length as part of the argument around what design was implemented. I used the star drift method to determine that property of my scope. By allowing a star to drift from the edge of the field stop to the other (making sure that it crosses the diameter and not a chord) and timing the transit allows the calculation of the true field of view using the equation TFoV (arcminutes) = T * 0.2507 * Cos (Dec). T is time in seconds, the 0.2507 is a constant that converts time to movement based on the motion of the earth and the final term is the Cosine of the declination in degrees. Ideally, one should use a star on the celestial equator, but any star up to 5o from zero declination will work (certainly for the accuracy I want).
To convert this result into a focal length of the scope, you must also know the field stop diameter of the eyepiece precisely. Measuring this can be tricky, especially as many EPs have internal field stops which would necessitate taking the eyepiece apart (don’t!). Fortunately, Tele Vue publish this information on all their eyepieces. Given there would be manufacturing variances I used three Delos eyepieces (4.5mm, 10mm, and 14mm) and averaged the result.
To calculate the telescope focal length, multiply the field stop diameter by 57.2958 (this is 360 / 2 * pi which the number of radians in a full circle) and divide the result by the measured TFoV in degrees. My result was 1,206mm. As such, no one has published a result I can find measuring a sub 1,200mm focal length. Herr Rohr on Astro-Foren just stated 1170 based on the f/9 on the test certificate. He did that with many scopes.
Addendum 29 April 2024 – APM have updated listings for a number of LZOS scopes in recent days including the scope reviewed here. The introductory text adds additional evidence this is in fact an f/9.2 scope. Text below
“If you want to visually magnify higher or need a longer focal length for smaller celestial objects, you should take a look at the 130mm f / 9.2 triplet SuperED Apo from us.
With a focal length of 1200mm you can already achieve high magnifications with a moderate focal length of the eyepiece”
What is the big deal about this specific model?
The longitudunal abberation plot showing four widely space colour crossings.
Why did I keep stating that I would purchase the 130/1200 LZOS if I were to add another scope to my collection? When TMB created the lens, the design polychromatic strehl was 0.984 (meaning a perfectly executed example would have this level of measured strehl across the visual spectrum) and the longitudinal aberration plot showed that it has four widely spaced colour crossings (and almost 5) which makes it a super-achromat (5 is called a hyper-achromat). The only other production lens to have four crossings was the APOMAX f/12 back in the late 90s and one of those crossings was in the near-infrared so it had no impact on the visual performance of the scope. The lens is also better than 1/10 P-V wavefront from 450nm to 700nm which means it is getting close to being a Baker Super-Apochromat. However, colour crossings do not tell the whole story. The Takahashi TOA series have zero crossings (achieved with two ED-elements and a substantial air spacing requiring a large complex lens cell) and those scopes are very much colour free.
Being quick off the mark to purchase the 130/1200 meant I had choice over all the lenses in that current batch run of eight. While all had excellent specification, a couple had measured strehl ratios at 0.99 or above at 532nm. I selected lens cell 122 which had the highest measured value of 0.992. By itself that does not mean much as even a “lowly” achromat could have a value that high at one specific wavelength but given what I knew about the lens design and the consistency and quality of LZOS production, it gave me confidence that this lens would be close to a perfectly executed example of the optic.
The certificate supplied with each LZOS lens to demonstrate that the lens has met the minimum spec as per the contract.
At the end of the day, these are all just numbers which parts of the internet like to discuss ad infinitum. What really matters is how a scope performs under the night sky. What can you see on the Moon, planets, double star splits and low contrast features in DSOs etc?
Under the stars
It actually took far too long to have first light with this scope. Work commitments, bad weather and other factors conspired to prevent me discovering if the scope was all that I thought it would be. After just one session, it completely redefined my definition of what it means to be an apochromat. It’s a reflector without the central obstruction lowering the contrast. It does not matter what object and what power; I have never managed to glimpse any false colour. I do not quite view any other Apo the same way anymore.
Eventually I decided to perform a star test though it was not going to tell me anything I had not already learned from many sessions under the stars. Even with Suiter’s book directly to hand, it was beyond my capabilities to determine what deviation there is from a perfect optic. I am not surprised. If Markus Ludes was unable to tell the lenses apart, and Tom Back was not prepared to bet that he could, both of whom were far more experienced and knowledgeable than I ever will be, what chance did I have? Without a dark green filter in place (how you should always star test a refractor according to both Roland Christen and Tom Back, though I find it instructive to do with and without) the Fresnel pattern is pure white.
I took the LZOS 130 on a staycation in in 2020 after Covid lock downs were eased and it delivered some memorable stargazing.
King of the Solar System, Jupiter is pretty special with this scope. Subtle shading in the numerous belts littered with white spots, dark storms, hue variations in the polar hoods and the GRS along with attendant vortices that track it, and hard-edged ellipse shadows during transits along with clear Galilean moon disks against the Jovian surface. Speaking of the moons, you can put away your planetarium software. Identifying each moon is easy as they are different sizes and have delicate colours to differentiate them. Did I once see a slight variation in the shading of Ganymede indicating surface detail at stupidly high power in excellent seeing conditions? Perhaps, but not confident enough to put money on it (we have all been guilty of averted imagination in this hobby).
Saturn is equally special. The ring shows structural features with variations in shading with a very sharp Cassini division and the crepe ring is really obvious. The Encke minimum is also seen (not to be confused with the Encke Division which requires a much larger scope). The planetary disc itself shows numerous subtle bands and the polar hood reveals structure as well with some banding
I am not a big Mars observer. Perhaps my dad played Jeff Wayne’s War of Worlds in the car too often when I was kid. But I may have whispered wow during the most recent opposition on a night of good seeing.
One other aspect I would highlight are the colours seen on the planets. At best, with all the telescopes I have used, it is delicate hues that are seen in cloud belts and surface markings. While vibrant is too strong a word, the colours seen with the 130, in particular with the gas giants, show an increase in intensity from other scopes in the aperture class which really helps to bring out the often-subtle variations in features on the planetary discs.
The APM LZOS 130 on top of Primrose Hill in London after a session broadcasting with BBC local radio (team in the background). Saturn was pretty special that night.
I view the Moon as a big source of light pollution in the sky to be avoided. But sometimes I find myself taking quick looks and it is certainly an impressive sight. Jet black shadows cast across snow whites, greys, silvers and tans of the surface made of riles, craters and mountains. The night sky on the edge of the moon is pitch black with no unfocused light. One of the great lunar tests for a telescope is the number of visible craterlets in Plato though this is also very sensitive to seeing conditions. I have managed four several times and had a fifth twice. I think 6 or 7 might just be possible on a night of exceptional seeing, though as white spots rather than pits in the surface.
The scope eats double stars for breakfast (and lunch and dinner) and provides some of the most satisfying views of them I have ever had with a medium aperture scope. Delta Cygni, Lambda Cygni, Zeta Herculis, Antares (difficult from the UK due its low altitude), 36 Andromedae, Propus, Struve 1126 (for when you realise Procyon is beyond pretty much any amateur scope! But at 0.8” a good challenge) Omega Leonis, and Sirius among a whole host of others. If the atmospheric conditions allow it, this scope will split/resolve it thanks to its capacity to go to very high magnifications and really putting all the light where it is supposed to go. Those troublesome doubles where the secondary sits directly on the first diffraction ring of the primary are just that bit easier as the ring is so faint. To really push this scope, you need to head to arcsecond and sub-arcsecond separations and then you are also at the mercy of seeing conditions.
While the LZOS 130/1200 is thought first and foremost as a planetary and double star scope, all the qualities which make it such a formidable instrument for those targets also transfer directly to a superlative performance on deep sky for its aperture. The focal length means the maximum field achievable with a 2” eyepiece is 2.2o which is more than enough to encompass all but a few of the largest DSOs. The maximum field is fully useable with no field curvature spoiling the periphery (no doubt aided by the greater depth of field that a focal ratio of 9.2 delivers – Sidgwick uses the formula 4 x (1.22 x wavelength x Focal Ratio2) to calculate depth of focus. As it is proportional to focal ratio squared, an f/10 scope has four times the depth of focus of an f/5 scope for example).
While 25-30mm of additional aperture over the 4” class scopes might not seem like much, there is a noticeable jump in how deep this scope will go compared to its smaller cousins due the almost 70% additional light it gathers. Many globular clusters are resolved across the entire face of the cluster as the optics make pinpoints out of the cluster members.
The APM LZOS 130 in Regent’s Park with the BT Tower in view at a Baker Street Irregular Astronomer starparty.
I have found the superb contrast means the extent of nebulae and galaxies and the details within, can match instruments as much as a couple of inches of greater aperture in terms of what can actually be seen, even if the image itself is dimmer. And sometimes much greater apertures (looking at you M33).
Open clusters are truly spectacular. Once again, the cliché of diamonds on velvet, but subtle variations in star colours seem to show more easily, providing an extra dynamic to often familiar targets. Being a deep sky junky, and only a casual planetary observer, I have found this scope delivers what I was hoping in DSO performance.
Given the length of the scope, some consideration is needed around mounting, especially if you take it to very high powers which this scope takes without breaking a sweat. Runing out of light or the local seeing conditions are always the impediment to higher magnification rather than image breakdown because of the optic. 400x, even 500x is no problem if the conditions allow it. It is ably carried by my Tele Optic Ercole but some focus-induced shakes above 200x start to become intrusive which is just cruising speed for this scope. However, with the APM AzMaxLoad which I use with my 180mm refractor, it is solid as a rock. I know another UK-based owner uses his with a T-Rex mount and states it is a very stable platform “even at ludicrous magnifications.”
Current Availability
Given current geopolitical events, purchasing this scope new today is not possible. Markus Ludes of APM did post that after sanctions were imposed on Russia, LZOS were still able to deliver on the lens run that was then in production as it was part of a pre-existing contract. However, now the distributors of APM scopes list them as unavailable till further notice. The price of the 130/1200 in the configuration I own was listed as £6,719 including VAT at that time. The Kruppax-50 APM tube with standard 3.5” Feathertouch (smaller focusers could be ordered) would likely be higher. It is not clear if that price included the storage case (I paid for that separately at a price of £335 but I only paid around £5,400 for the scope). At the time I ordered, the serial numbers only went to 123. I know of at least one more production run which took that into the 130s, so possibly there is only 140 of these telescopes out in the wild at most. Unfortunately, in an era where astrophotography is the dominant focus of a majority in our hobby, short focal length scopes are far more popular. The 130/780 production run is at least 3x as great. The 130/1200s do come up for sale on the used market from time to time, I imagine followed by a touch of regret after the seller lets the scope go.
The substantial flight case is safe home for the scope when not in use.
Review Conclusion
If you have made it this far, it is clear I think rather highly of this scope. The longer focal length combined with a superbly made triplet objective delivers a viewing experience that is unrivalled in its aperture class. This really is a seeing limited instrument every night of the year. Regardless of whether you are a dedicated planetary or double star observer, or a DSO junkie like me, this scope provides views at the eyepiece that will put a smile on your face.
The APM LZOS 130 at night after just completing my target of observing all open clusters brighter than mag +12 in Cassiopeia.
One obvious question to ask would be is my lens outperforming other 130/1200s due its very high strehl? The answer is almost certainly no. The internet is littered with observing reports from owners of this remarkable scope reporting very similar experiences to my own and many of these scopes have a lower measured strehl (LZOS guarantee a minimum 0.95 strehl as part of their contractual arrangement with APM for lenses 6-inches and under). The experiences of Markus Ludes and Tom Back touched upon in the history of the scope reinforce this. Tom Back actually compared an early version of this scope against his own Astrophysics 130 f/8.35 (reportedly with a measured strehl of 0.996) and concluded the 130/1200 was superior.
While the scope is quite long, it is still light weight enough to travel around with (I have taken it across London to Baker Street Irregular Astronomer star parties) but the extra length does mean a slightly more robust mounting solution is needed to really push the scope to stupid powers.
It is a shame that long focus refractors are not more popular but with only as many 140 of these out in the wild and current geo-politics what they are, obtaining one will be difficult but they do come up for sale from time-to-time. Do make sure to steal a look through one if you see it on the observing field. It will be worth the diversion. Thomas Back gave the community some amazing scope designs but in my opinion this one is his magnum opus.