Meridian flip, any way to control it

[oldpink]

almost had a disaster twice last night

I was shooting Mars & Saturn and dodging streetlamps, when Mars was getting obliterated by a streetlamp I decided to swap to Saturn

clicked on CdC  and hit slew expecting it to move to the east, Ahhhhh my telescope decides it wants to be a crane and started slewing to the opposite side of the mount

and trying to lift my laptop via the camera lead, lucky I was standing next to the telescope and could grab things and unplug leads

it happened again when I went to M105 which was very close to mars
it could have been worse as I almost moved the telescope remotely from my bedroom but decided to plug in a HD to download some data

I read somewhere you can use EQMOD to control Meridian flip and stop the telescope colliding with the mount by setting points that it won't go beyond
has anyone set this up, if so can you give me any pointers as to how to go about it

[IanL]

Explained here:

http://eq-mod.sourceforge.net/docs/EQASCOM_Limits.pdf

http://eq-mod.sourceforge.net/docs/MovementStrategies.pdf

But that really applies to preventing scope to tripod/pier collisions during tracking and slewing.  You can disable auto meridian flip (somewhere in the options, can't remember exactly where), but that only works whilst tracking, and the mount will still auto-flip after a goto if it needs to.

I would suggest a few things:

- Set the limits and keep them enabled.  It is a good idea to avoid expensive mistakes due to avoidable collisions. You may need to turn off limits temporarily when using the EQMOD polar alignment routine, so remember to turn them on again afterwards.

- Turn off auto flip if you are likely to have issues as you describe above.  This will protect you from unexpected surprises when tracking!

- When slewing, be aware of which side of the meridian the scope is currently pointing, and which side your new target is. Make sure the meridian and current scope pointing are displayed in the planetarium if possible (definitely possible in Stellariaum, don't know about CdC), so you should know what is going to happen in advance.  Bit like looking both ways before crossing the road.

- Sort out your cabling so this can't happen.  We all make mistakes and when using heavy/expensive/fragile gear like this, it makes sense to try to protect yourself against the consequences of those mistakes.  What I do with my cabling is this:

- Take the cable(s) from the cameras, bundle them up and run them up the scope to the tube ring (or the equivalent position near the Dec axis if not using rings).  Fix the cables there with self-adhesive Velcro or similar.  The cables should be loose enough that they are not pulling on the cameras or connectors, but you don't want a big loop of cable that can snag or drag (causing flexure).

- From that point make a loop of the cable and fix it to the main body of the mount (the part that rotates in RA) and fix it again. The loop needs to be big enough so the Dec axis can rotate 180 degrees both ways from home.

- Now make a third loop and fix it to the mount base/tripod head.  Again the loop needs to be big enough so the RA axis can rotate 180 degrees both ways from home.

- Finally run back from there to your laptop, etc.

Now you have a set-up that minimises the risk of cable drag causing flexure when imaging, has less chance of snagging, no chance of pulling your laptop, etc. and still allows complete freedom of movement for the mount.  It would allow automated meridian flips if you wish, though personally I still supervise them just in case.

The cables might be a bit short for this though.  What I do is have a small powered USB hub fixed to the tripod base and connect the cameras, etc. to that.  Low voltage power cables are easy enough to make a bit longer if you can solder, etc.

[oldpink]

thanks for the advice
I was looking at routing the cables along one leg and up along the telescope

[Zakalwe]

The mess of cabling when imaging is always a nuisance (I'm liking the fact that some manufacturers are starting to integrate USB hubs into their mounts now). What I have done is mounted a 7 port hub onto the mount itself. All USB cables run to this so I only have a single USB cable running back from the mount to the computer. All the USB cables are then sheathed in a zip-up nylon braid that helps to prevent snagging.

My next step is to integrate the power onto the mount in a similar fashion. I'm currently using XLR pugs into a home-made distrubution box, but I might swap it for one of these:

http://www.amazon.co.uk/Etronix-Power-Block-Station/dp/B0035B9NHM/ref=sr_1_1?ie=UTF8&qid=1395751712&sr=8-1&keywords=Etronix+Power+Block+Station

The only thing that I don't like is the use of banana plugs. It's be too easy to have a brain fade at 3AM and get the polarity swapped, with potentially disastrous consequences...

This is the current setup:

[IanL]

I did have my old USB hub mounted on the side of the NEQ6, basically on the control panel.  I found I was getting a lot of crashing and random disconnects of the equipment.  Suspect this was due to the USB connectors moving about when slewing, etc.  I moved the hub to the tripod head and things have been a lot more reliable since.  I do have my dew heater controller mounted on the back side of the mount head (opposite the control panel), since it is a bit less mission critical if something disconnects randomly.

On the 5 you might struggle to find enough space to fit things on the head itself, so hubs, etc. on the tripod head/legs/spreader might be the best option.  Definitely bundle up the cables once you have the routing sorted out.  I tie them in to ropes using cable ties and then wrap them in spiral cable wrap (can get it off Amazon or eBay).

[Zakalwe]

I did have my old USB hub mounted on the side of the NEQ6, basically on the control panel.  I found I was getting a lot of crashing and random disconnects of the equipment.  Suspect this was due to the USB connectors moving about when slewing, etc.

Thats a good point.

I have my cables secured using a P Clip thats bolted into the mount. This means that there's no movement on the USB plug at the hub whatsoever.

[oldpink]

thanks for the tips folks

Zakalwe LOL thats some wiring loom you got there Never thought of using XLR for power etc and I'm a sound engineer
I think I'll make up a custom loom with a USB power hub and connections for RJ45 etc, I'm pretty handy with a soldering iron

[Zakalwe]

thanks for the tips folks

Zakalwe LOL thats some wiring loom you got there Never thought of using XLR for power etc and I'm a sound engineer

I have a pathological hatred of those blasted cigarette-plugs. The quality is too variable, there's no positive-lock which means that they can easily work loose and they can spark on connect/disconnect. Speakon connectors would be a good solution too...the XLRs are a bit bulky.

[Kirscovitch]

I had an issue with this the other night. The best view from the driveway is too the south and right along the meridian. Until I get a USB extension for the DLSR I find myself picking up the laptop and walking it around the mount until it finishes the flip. 

First night I had the mount out I nearly freaked when I attempted a simple slew to the east of only a few degrees and expecting the scope just to nudge to the left (east looking south) and the thing took off to the west and almost yanked the laptop onto the ground! I knew about meridian flip but first time with an EQ was not really thinking about it.