Solved! Troubleshooting Maxdome alignment parameters request

[g__day (Matthew)]

Nailed, absolutely perfect - thanks to a post by Tandum on Cloudy Nights and the power of Google to find it searching for Maxdome slaving problems. Tandum shared that for Southern Hemisphere folk when using POTH the East / West dome / mount axis offset must the the opposite sign of what is documented.

I change that (and then the home bearing to match 11 degrees East of magnetic South) and everything worked to perfection. All slews to all bearings and elevation where nailed after those parameter changes. Really sweet outcome and feeling so good about this.

I sent an update and thanks to Doug at Diffraction Limited, Chris Ericksson at Cloudy Nights and Tandum and would like to thank folk who helped me out here as well. Lateral thinking, friends, google and preservation really paid off! Now I think it's definitely time to chill!

Matthew

[w0mbat (Ian)]

Hi Matthew. How is it going? I will be interested to see if you get any worthwhile help from Diffraction Ltd.
As you know I also have not been able to get my dome synch correct yet. It is interesting that my mount intersect is also below the dome equator. I have a negative number here. Diffraction never commented on that.
I notice in your list you have Dome diameter=44.9" Your not confusing diameter and radius are you? Your 44.9 is the correct value (I use 45") but that is the radius not the diameter.
Good luck. I'll be very interested in your progress.
Ian

[g__day (Matthew)]

Yes, typo - 44.9" is the radius.

A Dome lower won't affect things much. In the end you are solving at a particular place inside a half sphere you a shoot a ray out to a distant object and wish to know where that line intersects the dome. The maths is complex but not overly so.

Diffraction Limited kept saying the maths is correct, and they obviously don't have any optimal troubleshooting testing methodology. Well the equation part of their maths was correct but not the definition of signs of input parameters; so their maths was overall incorrect!

If you are in the Southern Hemisphere and your Mount is East of your Dome - that is a negative offset, not a positive one. Once that was changed the mount and the dome align perfectly.

[w0mbat (Ian)]

This all really annoys me. Over a year ago I had long discussions with Diffraction Ltd along very much the same lines as you have. They insisted that the Maxdome software was tested and verified to work in both hemispheres. I have wasted days and days trying to work out where I was going wrong. Now they say there are differences in the Southern Hemisphere!!!! I am not impressed!
The other thing that amazes me is that there must be many southern hemisphere users that have encountered these issues before. Maxdome has been around for ages. I just don't understand why these things have not been sorted long ago.
The one positive is that I now know I'm not such an idiot as I thought!
Ian

[g__day (Matthew)]

Diffraction Limited stated they had no way of testing things out in the Southern Hemisphere - which is half the world. You think such a long track company with global sales would have tested things in both hemispheres with a simple check of alignment with no offset between dome and mount pivot point, with only an East offset, with an North East offset, with a North offset, with a North West offset, with a West offset with a South West offset, with a South offset and with a South East offset. That's 9 offsets * say 12 compass points * 3 elevations - where you are just doing slew then check. I would estimate that you could easily do all that in a day then certify your gear works - or in their case reveal the sign for East / West was wrong.

I presume most folks mount their domes directly over their mount pivot points or with no East / West offset in our hemisphere. Searching on Diffraction Limited's technical support boards there were no other posts on dome mis-alignment. Maybe everyone just solves it for themselves.

I am kinda stunned I was the guinea pig that spotted the cause of the error. When I called Sirius labs today to update them of the solution - the first thing Alan said was he was going to write Diffraction Limited immediately to say why wasn't this tested properly and stress they need to update their Southern Hemisphere documentation.

Hopefully now there is this thread here, plus the detailed version on Diffraction Limited's own MaxDome forums and plus one entry on Cloudy Nights on fixing dome alignment other folks won't be challenged by this to the degree we faced! I hope you get a chance to see if this simple switch of parameters corrects your set up.

One last thing I noticed. After correcting the slaving parameters in each of POTH, ASCOM Maxdome driver and MaximDL - the standalone Diffraction Limited ASCOM driver alone didn't at all align the scope and the mount - ever - it was 40 degrees out for reason unknown - whereas POTH and MaximDL were spot on every time; something weird is happening there.

[h0ughy (David)]

only just stumbled on this one - fantastic effort and documentation. you know i had the exact same issues when i first got my maxdome and never managed to get it working properly

[g__day (Matthew)]

Thanks David - really a group effort and a lot of patience to solve one small documentation error on the sign of a particular offset for the Southern hemisphere. I hope other folk find this useful - both the solution, and the methodology and tenacity that is often helpful when struck with a persistent problem!

[g__day (Matthew)]

So yesterday I bought the SkyX universal subscription - trying to get the Mount and Dome working first.

The Mount seems to work best as a Meade LX200 mount - the selectable Vixen SS2K-PC driver just hangs things.

When I control the Dome via TSX - the slews are off again - I basically entered all all the units as 100x what they were in inches - and am now trying to figure out which sign for which parameter is wrong in my hemisphere!

[h0ughy (David)]

Originally Posted by g__day

So yesterday I bought the SkyX universal subscription - trying to get the Mount and Dome working first.

The Mount seems to work best as a Meade LX200 mount - the selectable Vixen SS2K-PC driver just hangs things.

When I control the Dome via TSX - the slews are off again - I basically entered all all the units as 100x what they were in inches - and am now trying to figure out which sign for which parameter is wrong in my hemisphere!

well i thought i was pretty darn dumb, as i bought the sky6 and automadome when i got the dome in 2009 but i could never get the thing to work no matter how many times i reloaded and reconfigured it to what they told me. I had help from some members on this site and even showed them the result i had and they didn't know either.. but then it worked with gemini.net and ascom dome control to which i am trying to get going again after rebuilding the dome.

I emailed them for help which ended up never got fixed so it ended up being a 900 dollar loss of investment in software, in my opinion crud support and crud results. you worked the issue more than what i did and managed to get a result. Software biscuit I think was a waste of time and money for me..IMO

Which then brings me to an interesting point - how is it that some southern hemisphere dome owners can get the thing to work and others like me cant get it going at all

[g__day (Matthew)]

David,

I think the East / West offset thing could have fooled many folk - but only those who had their mount not perfectly under their dome's pivot point may have experienced this issue.

I know having tested several dome management software solutions - MaximDL seems the most reliable; the struggles I am having trying to get TSX to solve the required dome position - when I supply it exactly the same geometry parameters that MaximDL uses baffles me. If its not the sign then that speaks to me that someone didn't test the software properly - and maybe a coding error or sign problem occurs in the code.

Matthew