Has anyone used the old style Vixen GP/Starbook-S for imaging?

[andyrawlins]

Hello all

I have one of the old olive coloured Vixen GP mounts which I have been using mainly for visual and photos of the moon since 2012.  Ever since I got the Starbook-S for it there has been a tendency for a vibration to be set up after fine movement in the Dec minus direction.  This can usually be cancelled my nudging Dec + and has't been a problem for short exposure photos of the moon with my 8" Europa Orion Optics tube.  However, with longer exposures, even say 5 seconds, I get non round stars.  Now I should say that its probably overloaded - I think it is rated at 7Kg whereas my rig plus camera is about 10Kg.  I believe that the vibration thing would happen with lower weights/nothing  (I need to check)  but the overweight could be affecting it in other ways I guess.  I have more luck with the tube nearly horizontal than with it nearly vertical.  

I will probably upgrade and keep this one for more casual use or a later lighter scope but I'd be interested to know if anyone has used this successfully for images with any setup.  The Starbook-S 'chart mode' feature is a nice one but I think I read somewhere that the way the Starbook works makes it unsuitable for imaging.  It would be nice to hear that it is actually a good mount if used within its capabilities. 

The obvious answer is a better mount and I'll probably get an HEQ5-R though I have considered the Explore Scientific EXOS-2 PMC-Eight GOTO Mount.  Any thoughts?

Cheers

Andy

[Stu]

I’m not an imager at all Andy, but given that normal advice is to stick with 1/2 to 2/3rds of rated capacity when imaging, it seems likely that overloading the mount is what is causing the problems.

I’ve used a Vixen GP quite often for visual and even though the 7kg is likely conservative, I still think you are just asking too much of the mount.

I’m sure others who have direct experience will be along shortly to comment.

[Franklin]

Wow, nice mount. I have a Vixen GP2, same as yours but white and I think the problems you are experiencing are probably due to overloading. I am visual only but I put 9.5kg on it once and it was useless. It now carries a 102mm refractor at 5.5kg and performs very well. When I load my little 2kg frac, it is hurricane proof! I have it on a CG5 tripod which definately helps.

 

[F15Rules]

Hi Andy,

I know this will sound like a dumb question, but your photo doesn't show a counterweight on the c/w bar.. so, a) are you using one and b) is it heavy enough to properly balance your scope? 

If the answer to either of these questions is no, then that could be part or all of your problem.

Lovely mount.. I have one and really like it. A 10kg load for visual IF perfectly balanced would probably work. I'm not an imager though, so can't comment on that aspect.

Hope you get it sorted.

Dave

Edited October 31, 2021 by F15Rules

[dweller25]

Hello @andyrawlins

I have the same green Vixen GP which I use for visual only.

I keep the scope weight down to around 6.5kg maximum for best results and use a counterweight big enough to allow good balance close to the EQ head rather than at the far end which can set up vibrations.

I also had the same tripod as you but found it not stable enough so changed to a Berlebach UNI.

10kg of kit is possibly a bit too much for imaging.

It s a very good mount used within it’s capabilities.

Perhaps you can look for a bigger Vixen GPDX - that will take 10kgs and you can use your existing Starbook.

Or consider a lighter more compact scope - I use a Mewlon 180 on mine and it is very stable at x400.

Hope that helps.

Edited October 31, 2021 by dweller25

[andyrawlins]

2 hours ago, F15Rules said:

Hi Andy,

I know this will sound like a dumb question, but your photo doesn't show a counterweight on the c/w bar.. so, a) are you using one and b) is it heavy enough to properly balance your scope? 

If the answer to either of these questions is no, then that could be part or all of your problem.

Lovely mount.. I have one and really like it. A 10kg load for visual IF perfectly balanced would probably work. I'm not an imager though, so can't comment on that aspect.

Hope you get it sorted.

Dave

Thanks Dave

Yes I have one 7.5kg weight.  It not quite enough to balance the scope with the camera on (its fine without) but that motor seems very strong.  It's the Dec motor/movement that seems to cause the problems.  I did report it to Orion Optics when I bought it - I'm not sure what they said or why never sent it back (or indeed why they sold me that scope with that mount).  I'll have a play with just the camera and no telescope and see if it behaves which will confirm the overloading problem.  I originally bought the mount with a single axis motor that was fine.  It was when I added the Starbook and motors it all went wrong.  I'm guessing that motor is faulty.  I might take it to bits.  That always helps

 

PS yes it is a lovely mount - beautifully finished and pristine apart from some of the plastic bits.  I have seen several HEQ6/tripods with rusty bits.  The mount does have a bit of play on both axis and always did but its way better than the GEM starter mount I had on my first scope.  

Edited October 31, 2021 by andyrawlins

[andyrawlins]

3 hours ago, dweller25 said:

Hello @andyrawlins

I have the same green Vixen GP which I use for visual only.

I keep the scope weight down to around 6.5kg maximum for best results and use a counterweight big enough to allow good balance close to the EQ head rather than at the far end which can set up vibrations.

I also had the same tripod as you but found it not stable enough so changed to a Berlebach UNI.

10kg of kit is possibly a bit too much for imaging.

It s a very good mount used within it’s capabilities.

Perhaps you can look for a bigger Vixen GPDX - that will take 10kgs and you can use your existing Starbook.

Or consider a lighter more compact scope - I use a Mewlon 180 on mine and it is very stable at x400.

Hope that helps.

Good tip about keeping the weight close to the mount.  I'll see if I can get another one second hand.  Matching of course!  Thanks David

[andyrawlins]

I have just had another fiddle with the mount with and without the scope on.  The vibrations in the dec axis are there all the time at a low level but much worse with the scope on. (which is a big metal tube after all)  The dec motor was slightly loose in its mounting which I have tightened.  However, the dec axis is incredibly stiff, with the RA one not much better.  Does anyone have any instructions for servicing this mount?  I assume its a case of take it apart, clean re-grease and reassemble but that may be easier said than done

[pete_gamby]

If you are using the alignment process in the Starbook S and the mount is not physically perfectly polar aligned, the controller will constantly "nudge" the DEC motor to maintain tracking. This "feature" was typically referred to as DEC jump.

The received wisdom for imaging with a Starbook or Starbook S was to not use the controller to align but to make sure physical polar alignment is spot on (polar scope, drift align etc) so that only the RA motor is in use to track/image.

I'd tend to agree that overloading is also not helping.

Cheers, Pete (who used to be Vixen product manager at Opticron)

[andyrawlins]

2 hours ago, pete_gamby said:

If you are using the alignment process in the Starbook S and the mount is not physically perfectly polar aligned, the controller will constantly "nudge" the DEC motor to maintain tracking. This "feature" was typically referred to as DEC jump.

The received wisdom for imaging with a Starbook or Starbook S was to not use the controller to align but to make sure physical polar alignment is spot on (polar scope, drift align etc) so that only the RA motor is in use to track/image.

I'd tend to agree that overloading is also not helping.

Cheers, Pete (who used to be Vixen product manager at Opticron)

Brilliant thanks Pete - I knew I'd heard something about it 'hunting'.  I can't use a polar scope (because I don't have on and because of my knees if I did) but am planning to get an iPolar for my new mount.  They don't do an adaptor for Vixen GP but would you happen to know if it is compatible with other mounts.? I seem to remember hearing that you can use another make of polar scope (maybe Skywatcher) on them so an adaptor of that make should do the trick.  Polemaster do a Vixen adaptor but they are more expensive and people seem to prefer iPolar. 

[pete_gamby]

As far as I recall the Skywatcher polar scopes didn't fit the GP mounts but someone else may remember better!

It's a shame they don't include detailed dimensions of the thing in the user guide. If the diameter of the nosepiece was such that it would fit into the polar scope hole with a gap around it, you might be able to then 3D print a collar-style adapter to secure it in place.

Cheers, Pete

[Franklin]

I have a Skywatcher polar scope in my GP2 and it works fine. There was a 2-3mm gap that needed making up with a washer though.

[andyrawlins]

I got the iPolar with the HEQ adaptor to go on my new HEQ5 Rowan which is 'on the way'.  It doesn't directly fit the Vixen mount (too small)  but I managed to make a collar or washer out of a stiff foam which allows me to seat it quite firmly and reasonably accurately - more than enough for my needs.  The iPolar worked a treat (once I entered long and lat the right way round) and the Starbook worked like a deamon finding targets with better than ever precision.  So it looks like after 16 years of owning it I've finally found out how to use it properly, just in time to replace it with the HEQ5

I took the Dec axis apart cleaned and re-greased it.  Actually the grease in it wasn't too bad and I had quite a bit of trouble getting it back together just tight enough to work properly.  I think what made more difference was carefully adjusting the worm gear.  The whole thing now moves far more smoothly and quietly.  There still seems to be a vibration which renders it useless for long exposures but that may be due to overloading.  It will probably spend its retirement as a posh equatorial mount for my DSLR.