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Vixen Atlux German Equatorial Mount
Submitted: Thursday, 11th October 2007 by Matthew Kendall

This is a review of Vixen’s second generation, top of the line, German equatorial mount – the Atlux.  This is my fourth equatorial mount in three years.  I started with an eq3, followed by a second eq3-2 mount that I added motors too.  My first goto mount was a Celestron CG5 I purchased 2 years ago.  With astrophotography in mind I determined my next purchase would be a more decent platform.

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The Vixen Atlux GEM
What field did I select from?

I wanted one step above the typical workhorse EQ 5 or EQ6 pro in terms of pointing and tracking (low, smooth PE) performance.  I budgeted between $3,000 - $7,000 and was happy to consider either new or excellent condition used gear.  After a lot of information and help here the mounts I considered best fit my desires and budget included:

  1. Celestron CGE (new $5,900)
  2. Losmandy G11 + Gemini (new $5,500)
  3. Vixen Atlux using SkySensor2000-PC (new $7,200)
  4. Vixen Sphinx SXD using StarBook (new $2,900)
  5. Takahashi EM-200 Jr + Temma2 (new $7,100)

My selection criteria included reliability, carrying capacity, pointing ability, tracking ability and the ability to computer control this mount under Windows XP.

So to briefly compare these mounts – the CGE has the greatest carrying capacity – but I read needs significant tuning to improve pretty shabby PE (so hence mediocre tracking ability).  The G11 has slightly lower carrying capacity, better pointing and better tracking, it’s a workhorse for serious imagers – but I’ve heard if you mis-balance the load be prepared to suffer burnt out motors!  The Atlux I have heard a few folk say – get one if you can, but all sales are halted until the next version (which is skybook controlled) is available for overseas sales later this year.  The deluxe version of the Sphinx is a very interesting beast, but a load capacity of around 15kgs for astrophotography use was just a bit under my target.  The Takahashi has slightly lower load capacity than the Atlux, but it’s reputed to have the best gears, mechanics and therefore best pointing and tracking ability.

I was very close to closing a deal on a second hand EM-200 mid-year when my financial controller balked at the expense and its timing.  However this softened things up and when I saw a mint condition Atlux – well it was sold within 36 hours of listing.

So I went into this with six months sporadic research that indicated the Takahashi or Vixen were my best platforms at the lowest rung of high-end equipment to meet my needs.

Atlux Overview

A few quick facts on the Vixen Atlux are useful before we dive into its performance:

  1. It’s cream – in colour and performance
  2. It just looks Japanese and screams build quality
  3. Its heavy – you exercise all the muscles built up a lift time ago being a gym junkie
  4. Its rated carrying capacity for imaging workloads is 22 kgs – so up to a 14” SCT.
  5. Its PE untrained is 7 arc seconds and trained Vixen claim 3 – 3.5 arc seconds.
  6. A power cable and a signal cable connect to the mount, no other cables run externally anywhere.
  7. It is easy to expose the RA and DEC motors and gears – which are all large, high quality brass affairs.
  8. It is driven by a hand controller called the SkySensor2000-PC, which is an old-fashioned brute of a unit, with awesome power and reliability hidden under a plain looking interface.
  9. Its smart enough to account for things like polar mis-alignment on point and tracking!
  10. On power on it remembers its last position if you wish it and its internal clock is quite accurate
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Side view

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Hand Controller
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With the scope
 
What where my expectations?

My initial expectations where equal measures of joy, fear and anticipation.  It looks sexy and extremely well constructed – but this was an opportunity purchase I hoped I wouldn’t be regretting.  And of course for a week after purchase every single night it was cloudy.

The only challenge attaching this to my permanent pier was drilling a slightly large bore central hole in 75mm thickness of aluminium that forms the plug in the head of my pier.  Next time a machinist does this because drilling a soft metal like Aluminium with anything other than a lathe is a total pain.  A task I hoped to complete in 20 minutes was 3 hours of pain staking effort.

After that it was simplicity to attach the OTA via CG5 dovetails to the mount.  Note I view the C9.25 to CG5 dovetail to be flimsy – I’m upgrading to Losmandy dovetail side saddle gear as soon as possible.   Finally I powered the mount initially from a Celestron 17amp hour Powertank, then a 3amp regulated 12 volt power supply then finally a 14 volt 5 amp cooled, regulated power supply.

What are its limitations, odd characteristics and hard to love features?

So the pain before the gain, and believe me there were many initial pain points – all minor but all just a series of stresses to absorb or challenges to overcome on the journey to better Astro pics!

Let me say Thank God the Yahoo SkySensor2000-PC user group exists!  Now onto the pain:

Dom argito gazhi mashitia – if you don’t understand that you’ll probably guess what my first issue with the instruction manual was – all 150 pages of it.  It only took me four days searching each evening (warning the Vixen Japan website is useless to search for online English PDF manuals).  At leash the Hand Controller had been switched to default to English from its original Japanese settings!

How’s the electricity wired on this thing?  Short answer backwards compared to anything else on the market – so be carefully wiring this thing to a permanent transformer via the ubiquitous cigarette lighter connection type.

What ring tubes are sold today?  Originally these things were sold holding Celestron Scopes (white if that dates them) with a single massive tube ring – from the Japanese Manual.  AstroOptical say to the best of their knowledge these rings never even existed for my scope version!

The new interface walk – well it’s different from the Celestron CG5.  It’s corny – but read the manual and practice, practice, practice.  Many features of the hand controller and their implications really aren’t spelt out well.  Its go online to query meaning a lot.  A few examples follow:

Hello I’m in the southern hemisphere – why is -060 180 -060 180 very important to me, and which way do I start the mount off from, how do I enter my Latitude and Longitude and what date format am I using?   Why is it that so many international developers seem to think only the Northern Hemisphere exist and adopt all it conventions for an international audience?  The above questions bugged me because of poor definition.  For instance those funny numbers are gear ratios, but the negative sign tells the scope run the gears backwards fella – you’re in the Southern hemisphere, get the sign wrong and watch the fun of inversed sidereal tracking rates!  Latitude and Longitude simple huh?  No you need the signs positive and negative again not North South or East or West so get a sign wrong and pain isn’t fun.  The date format is yy/mm/dd – just wish that was documented somewhere.  For the Southern hemisphere you have to start the mount off with the scope level and pointing due East (verse due West in the Northern hemisphere) – again poorly documented.

It all died one night – watch it recover.  At some point a PC freeze or a power surge sent the hand controller into Ker blitz mode.  Nothing seemed to help it.  Normally a 5 minute power-off trips its clever protection circuitry to re-start.  Not this time.  Anxiety followed – but wait there is a hard coded reset – power on holding all four direction buttons for three seconds and it’s a firm re-set – worked a treat.  Luckily I had written down all settings so I could just re-enter them and you’re go again!

PHD auto guiding wiring – oh you think they use S-BIG ST4 pin compatible wiring layouts do you?  Of course not – and it’s a major pain in the posterior wiring a 6 pin plug the way they did – not just sorting wires into a funny sequence – you have to short negatives and discard one wire.  So it’s soldering and crimping if you don’t want to buy a cheap converter from ShoeString Astronomy and wait a month for it to arrive!

PHD Guiding DEC yo-yoing - often during the night’s guided shots I’d see yo-yoing.  Turns out after a lot of diagnostics at least three factors came into play.  Firstly I’d told the mount its was polar aligned when it was 20 arc minutes off the SCP.  Secondly I was sending 500ms pulse guides when a star moved 0.2 pixels – but viewing, pixel size for a Meade DSI and focal length on my auto-guider OTA meant the optimal setting was closer to 0.8 pixels and 350ms pulses.  Thirdly DEC backlash was too high (defaults to 100 – I needed 60).  Finally the DEC gears had too much play – the DEC motor needed to be about .3 mm closer to the second DEC gear.  Figuring this out took close to a month and copious posts.  The corrections were all completed in under an hour once I knew what as required.

How do I tune the motors for backlash adjustment or shudder removal?  Well an Allen key reveals all the inner workings of the gears – and they are beautifully machined.  Some inspection and lithium grease helped – but the main thing was the motors with their 60 tooth gears sat just slightly the wrong distance from another 60 tooth gear causing a shudder every revolution in one spot on the RA, and way too much play on the DEC.  Simple fix with a screw driver once you’re brave enough to try!

What diameter is the weight shaft – not your normal 20 mm Sky Watcher size.  Oh no!  And of course the weights where misplaced by customs.  So I re-drilled my Sky Watcher weights initially until the Vixen’s appeared.  How many folk have 25mm drill bits handy – or are comfortable drilling that size hole with an electric hand drill?  Well it took an hour but all sorted – and a lot simpler than drilling Aluminium (which snatches the drill bit from the drill in the first 1/3 of a second of any drill attempt!).

Were does it excel?

So there was a steep learning curve setting up this mount.  But once a problem is fixed it didn’t re-occur, it stays fixed.  I wanted a mount with spot on gotos and tracking. 

Dead accurate pointing.  By spot on gotos I mean I want to remote image from 50 metres away from my backyard observatory in the cold of Winter.  So on a long focal length tube (2.3 metres) I want the target close to dead centre on a Canon 400D’s viewfinder’s central dot – quite a small target.  That is a very big ask.  With MaxPoint helping it’s pretty feasible.  So far every slew has been on target, normally close to the centre of the CCD chip – which is a blessing for faint targets like the Horsehead nebulae; where you won’t know if you’ve hit your target until a 3 minute shot completes.

Let’s talk about the tracking.  Incredible tracking – even if your polar alignment is miles off.
Tell the mount you are in polar unaligned mode, goto three well dispersed stars – centre them well and press align and you wake a very intelligent beast.  I did three to five minute unguided shots in this fashion (without PEC enabled) and got shots with very round stars – when I was initially 2-3 degrees off the SCP.  The scope adjusts and runs both motors to counter for polar misalignment and the airs refractive index at any given elevation – wow!  The tracking rate also accommodates object with different orbital rates to stars – planets, comets, satellites or the Moon – sophisticated!

Wake up – I’m ready to go.  The restart on power on is a beautiful feature I have almost mastered.  Basically at power on press escape and everything is meant to be exactly calibrated per your last use – so for a permanent rig on a pier – heaven.  My pointing in this fashion is under ½ a degree out – but I just realised my polar alignment was ½ a degree out and I had set the mount into polar aligned mode.  More tests as soon as the weather clears will show how fine this feature can be tuned.  At present it looks like there is consistent 20 arc minute pointing error in one direction on re-start – the consistency showing me its likely set-up is holding things back.

Performance under load – what load?  Carrying my C9.25, a heavy piggy-backed Megrez 80mm and all my imaging gear is a walk in the park.  So much so that I’m adding a 5” MAK to this combination soon and it’s not likely to push things.  The motors don’t strain, it’s not jerky or inconsistent – everything is smooth under load.  Slews don’t rush to a target and halt abruptly – they accelerate up to maximum rate selected, hold it until it’s close to target, then slow down preventing excessive torque on the bearings and gears.  There is so much thought put into the quality of this rig it simply shines.

Bottom line – the documentation probably needs to be 300 pages to define all that this mount can do and how to run it properly.  I feel like I’ve gone from operating a V6 to a powering a Ferrari – I need to learn to be worthy of driving this mount.  I’m sure no one ever diminishes the pride and appreciation of their first heavy duty, quality mount – but this thing really performs effortlessly against huge expectations and a major claim on what it can do.  It’s a fully capable impressive mount in a second year novices hands – I give it nine out of ten – only the documentation hold this from a perfect score!

Review by Matthew Kendall (g__day). Discuss this review on the IceInSpace Forum.

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