Loosing USB connection all the time

[lukepower]

Hello,

 

I noticed today how sensitive my mount/scope combination is regarding balancing. It worked quite well for a few hours, but then there was simply no way to use it. I tried to rebalance it, and it was damn close to perfect, but still I kept loosing the connection. Please note that the tracking (or slewing) continued even without USB connection, so it wasn't a power failure, and I could guess that the balance is not the issue here.

It could be a USB cable issue, even if I use right now a shielded one with an industrial USB hub in front of the scope (and all other accessories working well even during the interruption, like the CCD camera). Maybe it has something to do with the interface to the mount (which I hope is not the case, as I am not really willing to unmount everything to send in the mount ).

 

As for the errors, sometimes i get ReadInt errors, sometimes I loose one axis, but most often Autoslew starts to do the Software USB Unplug/Plug procedure, mostly without success.

 

Any ideas?

 

Thanks

[lukepower]

I have to make my compliments to ASA, within less than one week they were able to tackle down the problem, fix it, and soon ship it back to me

Let's wait and see, I suspect the weather will turn evil as soon as the mount is back in the observatory

[lukepower]

Hi there,

 

today I got the mount back, yippey. And as I was too eager to try it, I re-mounted already everything back (well, I forgot to connect the focuser, but who cares) and fired up Autoslew.

It has to be said that the balance is bad, really. Autoslew starts, powers up the motors without trouble, and it runs just fine. So yes, I am happy

 

Thanks ASA for this really quick support procedure.

[GeorgeCarey]

Excellent news! Enjoy the mount.

George

[Waldemar]

Congratulations, Lukas, I am really happy for you! Enjoy!

Waldemar

[Roger]

And I am more than a mite relieved too (will soon be a proud owner...)

[lukepower]

Yes folks, I too love the sound of the direct drives, and yes, it is truly working WAY better than before. Even in its current unbalanced state (OK3Z is sitting 30cm out of the center of the tube) it is working

[lukepower]

Alright, finally the mount is working as expected, together with Sequence (beta) I made the following image:

 

As you see, I have quite some coma, I have to investigate this. If I remember correctly, this should come from the secondary, right?

[wemartin]

Hi Lukas,

 

Looks like you have a collimation problem, could be primary or secondary.  The focus is difficult to find when the collimation is off.  Do you have a field flattener?

 

Bill

[lukepower]

Hi Bill,

 

yes, the picture was taken on my Cassegrain with the ASA 4" reducer-corrector. I will go shortly to the observatory and see if moving the primary helps.

[Roger]

Luke

 

I sent you a PM.

[lukepower]

Alright folks, after some more fiddling at least the collimation seems better:

 

As for the reflections, the baffle tube of the primary seems shiny on the inside, so I'm gonna work on that for now.

[wemartin]

Hi Lukas,

 

Suggestion: Find a very bright star and centre it in your field of view, take the camera off and look through aperture and/or simply allow the light to fall on a white screen.  You should be able to see if there are stray reflections from baffles or screws or whatever.  By slewing the OTA you may be able to make these bad enough to find what's causing it and remove or mask these.  You should be able to use the diffraction spikes from the secondary mirror to fine adjust the collimation and centering also (I am somewhat surprised these are not stronger on the brightest stars). The 'rings' look like they have stars in them which means a stray reflection is ending up in the focal plane.  Have a close look at your corrector for polished edges on the optics which have not been masked.  I would be surprised by a baffle reflection ending up focused.  Usually these problems show up as poor contrast or 'blobs' in parts of the image.  Good hunting.

 

Bill

[lukepower]

Hi Bill,

 

good idea. Till now I identified some screws and the inside of the baffle tube being shiny, so I'll start with them. The corrector is from ASA; so hopefully they did a good job and it's ok

 

Anyway, I had the pleasure of using Sequence last night for a night-long session, and it ran flawlessy. For the first time I was also able to command the roll-off roof, so that it both opened at the beginning and closed at the end of the night.

 

Best regards

[wemartin]

Hi Lukas,

 

I have a 3" Wynn corrector from ASA.  It's an excellent optical design but the internal masking for the polished edge on one of the lenses was not done properly.  I had to take the corrector apart and cover this edge in order to get rid of some ghosts and to get good flat fields.  If you take some images with and without the corrector (balance problem...) you should be able to isolate this.  The pure Cassegrain images will also give you an idea of how much the corrector is doing for you at the FLI ccd edge.  You say Cassegrain-Newton...does this mean the primary does not have a hole and you have two secondary mirrors?  Baffling a fast configuration like this would be a real challenge and light diffracting around the Cassegrain secondary could be a problem with small misalignments.  All well-known and ray-traceable..

 

Bill

[lukepower]

Hi Bill,

 

I will check the corrector today, as I am dismantling the back of the scope to apply some velours on the inside of the baffle tube. It is definitively very shiny, so this should have some sort of impact.

 

The Scope design I have has basically a hole in the primary (like on a schmidt-cassegrain), where the lights comes back from the secondary towards the camera. I can exchange the secondary ( I have a total of three), effectively changing the focal ratio (between f/9 and f/20 in Cassegrain mode) or even making a Newton out of it (coming to f/3). I never tried that so far, though...

 

Thanks Bill

[lukepower]

Hi BIll,

 

I checked the corrector and it looks alright. Especially from the back (where the camera is mounted) everything is nicely black. From the front there are two very tiny white rings to be seen, probabily where the lenses are fixed in the casing.

 

My father helped me out yesterday to apply some velours (black of course) on the inside of the baffle tube, as well as on part of the secondary baffle. I then took a few images through slight clouds, judge by yourself:

 

I am quite happy now

[Roger]

Lovely.

[Pepepastrónomo]

Hello ,Luke.

just one question...how much did it cost you to send the mount to ASA and get it fixed?

thanks

 

Jose