Vixen Sphinx Mounts with NexSXD Motor Control

[marki]

Originally Posted by 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.

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.

Mark

[renormalised (Carl)]

Maybe it needs some saki to loosen it up

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 (Carl)]

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]

Originally Posted by 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

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

Mark

[marki]

Originally Posted by 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.

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 (Carl)]

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]

Originally Posted by 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

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 (Matt)]

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 (Matt)]

Originally Posted by 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.

Hi Ross,

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

Matt

[MattH (Matt)]

Originally Posted by 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....

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