Vixen Sphinx Mounts with NexSXD Motor Control

[MattH]

Hi,

I think I should share my experiences with Vixen Sphinx mounts. I bought my first telescope two years ago and very soon started thinking about astrophotography. It took me some time to buy all the bits and pieces, and then there was a big disappointment. Not only the mount (Sphinx SXW) was noisy (sometimes I thought it would fall apart) but guiding in the declination practically did not exist. There was a constant drift in one direction and then a sudden jump in the opposite direction. I have tried to identify the problem - too much load, lack of balance, dragging cables. I spent countless hours while browsing this and other astronomy sites. I even suspected my neighbour's black cat :screwy: who was constantly observing me from the balcony above, probably attracted by the grinding noise coming from the mount. I knew about problems many guys had had with this mount but at the same time I saw quite many good images taken using it. Finally, someone advised me to get a better model of Sphinx - SXD. After spending all the money on other equipment, I was so desperate that I ordered it.

By the time I received the new mount, I found the information about the NexSXD motor control produced by a MGAstro in Spain. It replaces the original board in the mount and uses NexStar protocol. It can be controlled using either NexRemote software or CGE-Pro hand controller. I had nothing to loose with the old mount, so why not to modify it. I received the new board and installed it without any problems. First, I thought that it did not work. I could not here any noise from the mount - absolutely nothing. Well, it worked. After few minutes I saw that the mount was moving along the RA axis. I was so eager to give it a try that I did not bother with proper alignment, balance, or correct focus. Just in case, I checked for the cat. She was not there :D. I started guiding and taking images of Centaurus A. I did not manage to take too many images because of the clouds but enough to see that the new board worked. The image is attached below. It is far from being perfect or even good but for me was fine.

The new mount SXD arrived, the problem in the declination axis still existed, and the mount was even noisier, so I immediately ordered another NexSXD board (they are a little different for both SXW and SXD). It arrived very quickly, no problems with installation, no more noise. Will it work? This time I took a little more time with balancing, alignment, etc, probably not enough time. The moon was almost full but I didn't care - there is a lot of light pollution from the surrounding block of units and car dealerships anyway. I was more than happy with the resulting images (Omega Centauri and M20). Then, there was cloudy for some time. Last week I took the image of M8 and was so happy that finally, after more than a year of struggling with the mount, things started to work, at least I hope so.

If someone needs more information about NexSXD, here is the link to their site:
http://www.telefonica.net/web2/amalthea/NexSXD/NexSXD_eng.htm

Cheers,
Matt

[marki]

Good to see you are having a win Matt. I also have both mounts and have a NexSXD board waiting to go in but celstron are being very slow at delivering the software.

Mark

[astroboy]

Sounds like like your trail of tears has finally come to a happy end .
I bought a Vixen GPDX GOTO a while ago and have yet to use it I hope it won't be a similar tale of woe.
Was the upgrade expensive ?
The shots are looking good BTW.

Thanks
Zane

[MattH]

Mark,

You can download the trial version of NexRemote (if this is the software you are waiting for) from Celestron web site. It is a full version that can be used for 30 days:

http://www.celestron.com/c3/downloads.php

The link to download is on the left-hand side.

Matt

[MattH]

Zane,

The current prices are at the bottom of MGAstro web site. I think I paid 158 Euros plus shipping. I do not think you will have these problem. I have never heard about such problems for GPDX.

Matt

[Ross G]

Hi Matt,

It's good to see that you are getting good results from your mount.

I have persisted with a Sphinx SXW mount for nearlly 2 years. The large DEC backlash has always been a problem, but with a lot of experimenting (...mainly, setting the Dec Backlash to 95%..) I am able to get good 10 minute guided exposures.
Unguided shots are a different story. I am lucky to get a good shot over 30 secs to a minute.

Apart from this, it is a beautiful, quality, well designed portable mount. Nothing around compares, not even a Losmandy G8 and is why I have persisted with it.

Therefore, I am happy to hear of the NexSxd replacement.
However, if it is just a replacement of the circuit board, do you still have problems with the DEC Backlash which I presume is a mechanical issue?

Great photos by the way.


Thanks.


Ross.

[MattH]

Hi Ross,

I have never had any significant problems with DEC backlash on my mounts. Perhaps I have been just lucky. I have thought for a long time that the backlash was huge. Later it appeared that as soon as you do the polar alignment in the StarBook controller on MORE THAN ONE STAR, the StarBook software starts compensating in DEC axis. Effectively, I saw huge jumps in DEC every few minutes and they were quite regular.

Since I got SXD, I was using mainly this mount. Judging by the log file from autoguiding, there is no backlash in DEC at all. OK, there must be some backlash but it looks like it is very small. I can see correction on both the sides of the axis, no sudden jumps, no persistence on one side.

I will do some tests with SXW, particularly, that I may decide to sell this mount and I do not want anybody to complain about it or get a Voodoo doll that looks like me :D. I will check later whether I have log files from this mount after installing NexSXD.

I will also try some unguided exposures, say 30s, 60s, 120s on both the mounts. Thanks for the suggestion.

BTW, I have not applied any backlash compensation in the NexRemote nor in the CGE-Pro hand controller.

Regards,
Matt

[renormalised]

Are all the Vixen mounts still being made in Japan, or do they build their mounts in China, ship them to Japan and do final assembly there??

[marki]

I have done Matt thanks but I have been waiting 2 months for nexremote to turnup from celestron.

Mark

[marki]

Yes they are made in Japan Carl, they have just come up with some crappy software and controllers that do not do the precision mechanics justice. Like Matt I have no difficulties with the dec axis on the SXD (even using the starbook) but there is some slop on the SXW.

Mark

[renormalised]

I've heard of some horror stories with the drive systems with these mounts and it just makes me wonder why would Vixen persist in sending out faulty mounts. Vixen mounts used to be spot on and you could rely on them, but it seems they've dropped the ball somewhere along the line. I hope their AXD and GAIA mounts don't have the same problem. I'd hate to fork out the approx $12K for the new AXD only to find out it was faulty.

[MattH]

The label reads "Made in Japan" on both the SXW and SXD. Does it mean anything? I do not think so.

[renormalised]

That's what I've been thinking...by the sounds of the stories I've heard about the DEC and RA problems, it seems that they're probably getting the mounts manufactured in China and then doing the final assembly in Japan. Chinese manufacturing is a real hit and miss affair (more miss than hit) and the quality of goods coming from there varies greatly, even on individual production lines. Just like Japan was after WW2, and the old adage of "Made in Japan" meaning rubbish and take your chances.

Won't do Vixen's reputation any good at all.

[marki]

Carl there is a big difference in the quality of the internals in the vixen mounts over the equivilant synta versions. I have stripped both of mine and inspected them in great detail (as I have with the synta mounts I once owned). A dead give away is that all the bearings are made in Japan as well as the quality of machining on the worms and gears as well as the motors and circuit boards etc etc. Remember these mounts cost a lot more then the synta equivilant, they really just messed up with the software and design of the starbook and that only comes in to play if you want to do AP as its fine for visual. like Matt I am hoping the NexSXD will cure the last of the irregularities present in autoguiding but can still guide for 20+ minute exposures using the starbook on the SXD. It will be nice to have a guider port on the mount rather than on the controller where vixen thinks it should be. This should remove the lag time also as the input will be direct rather then passing through the starbook.

Mark

[renormalised]

I didn't expect the Syntas to be upto scratch compared to the Vixen mounts. What caused me some concern was reading about some of the mechanical problems some Vixen owners had faced with their mounts and the shoddy deal they got off the Vixen customer service.

It seems the AXD also uses its version of the starbook to autoguide as well. Whether it's any better than the previous versions of the controller, I don't know as I've not seen any objective reviews done on the system, yet. It would be interesting to see if Vixen have solved their problems for their bigger mounts.

I'll be interested to see how the NexSXD goes in your mounts and how performs. Reason why is I'd like to grab a Vixen AX103S refractor in the future sometime, and I wouldn't mind mating it with a Vixen mount, considering their normal build quality and reliability. Although, if need be I'd get an EQ6...cheaper, I suppose:)

[MattH]

Carl,

I have just started using the modified mounts. So far I have spent no more than 10 hours for taking images, ranging from 120 secs to 300 secs. Of course it is too early to draw definite conclusions after 10 hours, especially that I am a rookie in astronomy. After struggling for more than a year, I am very happy with the results. As soon as I have more to say and show, I will do it. Everything depends on the weather.

Matt

[CometGuy]

Very interesting guys, and not an overlly expensive mod either.

To be honest I never had any problem autoguiding with the Sphinx SXW mount, it just seemed to work (using PHD and a DMK21). But then again I haven't exactly done a lot of guided Astrophotography. One thing is I never use the internal calibration to setup the mount - I rely on ASCOM software to do this instead.

Terry

[marki]

Carl you would have to be stark starring mad to consider the AXD mount even with the new starbook. These mounts will cost over 10K for a 31kg payload. The reason why you have not seen any pics etc is because no one is mad enough to buy one especially when vixen will not release PE etc. It was built to take on the AP Mach 1 but good luck to them with that one. The PMX costs around the same in oz with a stated PE, 41kg load capacity and a whole lot more going for it then the AXD. The biggest mistake vixen made was to phase out the atlux which had the same load capacity as the AXD, a stated PE of +/-5 (+/- 2 with PEC) and a cost of 6K. The SXD would make a good match with the AX103 plus camera/FW etc etc and is very light and small so easy to cart off to a dark site.

Mark

[marki]

Terry you also have to buy the software or celestron hand controller or both if you are keen and each will set you back about $269.00. Add that to the price of the NexSXD board and it all adds up.

Mark

[renormalised]

No, I wasn't considering one, I was just making comment on it after reading about the mount and the problems with the smaller mounts. I'm looking at an SXD for the mount...much lighter than the AXD which I'd have trouble carting about since I have trouble with arthritis in my joints.

I was looking at the PMX today...they've got them at Bintel for a shade over $10K. Beautiful mount, but at 26kg, with a good tripod that will be pushing it with the weight for me. Some days I'd have no trouble with it, but they're rare and having to pull the mount right down just to handle it would not make it all that portable for me, considering its size. Mind you, if I thought I could handle the weight and had a decent case/s to carry the parts in (and the money on me at the time) I'd buy one. I don't mind spending the time putting them together, it's just the thought of having to lift the whole caboose if I had to for whatever reason. I'd be more inclined to mount one permanently.

[marki]

The SXD is a very light weight mount so shouldn't cause too much strain on your back or joints Carl. Its actually lighter than the HEQ5 Pro or feels lighter anyway. The counter weights are also much smaller as well (1.8 and 3.9 kg) due to the design. A single 1.8 would be enough for the 103 with an EP. The PE is very good on mine, only the starbook that is the problem when trying to take pics, it can really cause grief with the autoguiding. I have had nights where I have not been able to get the thing to track properly using autoguiding so have turned off the correction leaving the tracking fuction on and guess what, two very flat lines appear on the graph. The starbook just doesn't like being told what to do and seems to fight any input. Either that or it processes the guide inputs before passing them on to the mount meaning it reacts too slowly and then a larger input is needed to correct and the whole thing turns upside down. On other nights using the exact same settings it just works:shrug:.

Mark

[renormalised]

Maybe it needs some saki to loosen it up:):P

Sounds like the starbook has a problem with talking to autoguiders. They need better software as it mightn't be a hardware problem per se. But if swapping out the control board is going to solve the problem then it might be worth it. It's a pity it's cantankerous like that as the starbook is a neat looking piece of kit.

[renormalised]

I was just looking at the Starbook Ten page. Apparently it has an "extension" you can add to the controller which takes in NTSC and Pal video inputs, so that it can act as an autoguider by itself. I wonder how accurate it is, or whether its any good at that function?? Unfortunately, I think it only works with the AXD mount

[Ross G]

Hi,

My first mount was a HEQ5Pro. It gave me 2 minute unguided exposures with a 650mm focal length. It autoguided for 10 minutes with no problems.

I then bought a Vixen SXW thinking I was upgrading. No way...!
Unguided exposures of even 30 seconds had bad periodic error.
I managed to get the autoguiding to work for 10 minute exposures by having the DEC Backlash at 90-95%. Admitedly, I can push these exposures to 20 minutes and they are still ok.
I have always thought the problem was too much backlash in the DEC axis. When I have slewing at the slowest setting I normally have to keep the Dec buttons pushed for 10 t0 20 seconds before the mount responds.
However, if the problem is actually in the Starbook, then maybe this modification is worthwhile. As I said before, the SXW mount has a certain quality that makes me want to persist with it.

Matt, I would be very interested in how your modified mounts work out.

Thanks.

Ross.

[marki]

You can do a similar thing with the current starbook but you have to buy the AGA1 autoguide adaptor (cheap at about $800 US :rofl:). Much better off with a sensitive CCD to do the auto guiding.

Mark

[marki]

The SXW has a problem with the dec axis. It is due to the fact that the mount has no roller bearings relying on closely machined tappered plain bearings in the cast which tend to be a bit sticky. You cannot get any decent tesion on the bolt holding the axis in place without locking the thing so they don't behave well there either. The SXD has bearings throughout and does not suffer from the same problem. The bearings are also the reason why the SXD can carry more weight than the SXW as the drive motors are actually much smaller on the SXD.

Mark

[renormalised]

Only one problem with the AGA....you can only use it on NTSC cameras. If you've got a Pal system camera, you've got to go buy another camera!!!!. And as you've mentioned....cost....not cheap for an add on that just gets your foot into the autoguiding door!!!.

Vixen didn't think this whole thing out too well, did they:)

[marki]

Their marketing team need a good kick in the pants. Would you believe at one time they were trying to sell the pec control as an add on even though they advertised the starbook as fully operational with all the functions. You had to go to their site in Japan, pay your fee and they would send you a code to unlock the function which was already loaded on the hand controller. Don't think they do that any more but I imagine the idea came from the American distributor as most the stuff on that site is overstated and exaggerated to say the least. They have the SXD listed as being able to carry 25kg even though the vixen manual clearly states it is 15kg 23 cm from the fulcrum.

Mark

[MattH]

Thanks guys for the discussion and all the information about Vixen Sphinx mounts, particularly for the remarks concerning SXW. Of course, I will continue using SXD and I will post some information about the progress (I hope there will be some). I have stopped using SXW but it looks like I will have to do some tests te check how it really behaves after the modification. Particularly, I have to check the infamous backlash in DEC and try to get some unguided exposures.

Cheers,
Matt

[Ross G]

Hi Matt,

I would be interested in seeing your unguided results with the SXW.
It would also be interesting to see whay sort of unguided exposures your SXD produces.


Thanks.

Ross.

[JohnH]

Matt,

FWIW your experiances are exactly what I found with this mount.

The DEC axis simply could not be used during guiding it might work for a while but was unstable backlash being 10s plus. I had the worms adjusted and it worked for a while but soon slacked off back to its bad old ways. I had to offset alignment and set to DEC to correct against the drift to be able to work at all. Even then I was limited in exposure times. I had a VC200L on the mount though and was using a Canon20D and that was too much scope I guess (0.7"/pixel).

I lost patience and sold it.

For visual use it is ok, a good and portable mount. With a small, short fl scope it might just be acceptable for AP. With the new motor control board perhaps finally the mount is meeting its potential.

I have a G11 now with which I am extremely happy. It just works but those smooth flat correction graphs stll make me smile every time....

[MattH]

Hi Ross,

As soon as I get some unguided exposures, I will let you know.

Matt

[MattH]

Hi John,

After I have started having problems with SXW, I searched this forum, and I think I can recall your posts concerning the mount. Unfortunately, it was a little too late for me, so I was still trying to get it working correctly. BTW, I also use VC200L which together with light polluted sky in my area is not helpful.

Matt

[marki]

I have mine all setup now so will just have to find time to try it out.

Mark