Re: Noisy EXOS 2 PMC8?


Wes Mcdonald
 

Hi Peter

Well I can't say it sounds bad.  Its hard to hear but it is not hacking the way mine did when it stalled.  If you use the keypad to move it around, with rate set to 9, do you hear the musical notes step up as it goes through a series of ascending rates and then down again as it stops?

Now this is the part you probably don't want to hear.  When I tried to use it with a scope that weighed in at about 23# I had some pointing problems.  But I never really used it much to see was it my head or the mount.  I did get a pretty good alignment once with the heavy scope using a polemaster.  My overall stick time with the sky and this mount has just been too danged limited.

With any luck I will get some outside stick time this wednesday.  Then next week I'm heading out to a dark sky site for a few days for more fun I hope.  I will wring out the alignment procedure then.  I have to tell you though I have spoken to Jerry about alignment and am satisfied the thing works just fine -- notwithstanding my own problems.  Lots of others are using this thing.  In the end if you just cannot get it to do then it should go back for a checkup.

One thing I did the other day in my study was to run through the alignment procedure a number of times.  While I don't like the way it selects stars for me, it always went through and after the third star solved for the mount model matrix.  After that it moved around per plan, although I can't vouch for its accuracy.  Jerry published a presentation he made at AHSP earlier this month (its in the groups.io) in which he says in the video goto accuracy should be achievable to 5 arc minutes.  That should be plenty to have things in the eyepiece.   Wednesday I won't have my polemaster so I will be relying on the 2 and 3 star alignment algorithm.  I hope I can see the danged stars with the full moon and obstructions where I am.

Up to now my primary scope/mount has been a Meade LX200 10" SCT fork mount.  It took me a long time to learn to get a polar alignment with it on a wedge.  In the end I had to resort to a polemaster which did the trick.  With the EXOS II the polemaster will allow you to get a very good polar alignment.  I believe the correct approach is to do the polar alignment with the polemaster then set the mount precisely at its home position, recycle the PMC and explorestars and then do a one or more star alignment to clean up any little errors.  At least I think that is what worked for me with my heavy old Newtonian on the EXOS II.  I do remember the tracking error was very small but frankly I can't remember if the gotos were great or not.  In my view these two performance parameters are related and interdependent buy one is not sufficient for the other.  Atleast a great PA still might have bad gotos if the mount is not precisely aware of its orientation.

By the way is the timebase for your computer right on?  Need for it to be pretty close to on.

TLDR.  Lots of BS, not much light.

Wes.

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