Re: EXOS2 PMC-Eight Polar Alignment issue.


Thank you Wes. 

On 5 Sep 2020, at 15:43, Jason Colbeck <jasonacolbeck@...> wrote:

Nice write up.  I allways got perfect alignment with my CG4 & polar scope,,regularly got 3 to 5 mins exposure just tracking in RA at 420mm focal length. 20 mins when guiding, the clock face reticle makes it so easy to align,,The reticle in the exos-2 , is unfamiliar ,I'm going to replace it with a eq5 train track/ clockface one if it fits. I would like to try polar alignment using my guide scope & sharpcap but I haven't made the plunge yet. The exos-2 is new to me & I'm still learning my way around it,  But It has great potential & I love it so far. Hopefully its dark tonight so I can try aligning with the guide cam. 
It's all good 😃

On Fri, 4 Sep 2020, 21:57 Wes Mcdonald, <wesmcd6@...> wrote:
So I want to just make a point or two that might help.  

I cannot advise you on using the polar scope except to say don’t bother.  Get something else  which I will recommend below.  Life is too short to be messing with that danged little scope on your hands and knees.  If you are bound and determined to use it for heavens sake watch some you tube videos about it. There are
Many out there. And don’t forget to get the thing collimated to the ra axis per internet videos.  Bill, any mount that has a polar scope has the same issue for a user.  If you want to use a polar scope you just have to figure it out.  But you can buy your way out as I will show below.

If/when you get your RA axis polar aligned, which in the end you do using your altitude and azimuth adjustment bolts, you must return the mount to ra and dec polar home position before turning on the pmc8. You find out where polar home is for your mount by executing the procedure I documented in a document that is found in the files section of the mounts sub group.  

If you are going to not use a virtual alignment in explorestars, your mount must be level for your gotos to be correct even after you get a good mechanical polar alignment.

PSAlign pro has been mentioned.  It works wonders in an iPhone.  Yes you have to make sure the compass calibration is correct.  Be sure your phone compass is set for true north not magnetic.  This is also true if you are finding north with a regular compass.  You must remove the magnetic declination for your area to point the compass to true north.

Calibrate the phone compass by using the figure eight rotation method.  My app tells me when the compass calibration is poor.

PSAlign pro is used with the phone sitting in the  telescope saddle bottom down, face to the sky.  You need to make a jig to achieve this.  Mike lemhious has made 3D printed design for achieving this which you can download and send off for fabrication to a place like 3D hubs or a friend with a 3D printer.  He has. Aeolus posts about it with links.   But it’s easy to make up something out of some wood.  Just be sure the axes of the tray you make is square to the saddle etc so the phone is pointing dead along the line of sight.

When you use PSAlign pro do not have the motors on the mount turned on.  They generate a terrific magnetic field that will ruin you.

With the phone in your cradle and PSAlign pro running make sure you have you mount in polar home.  Then you adjust the az and alt bolts until the cross hair is centered.  When it is you are pretty good polar aligned.

So the above is one way that costs little and works pretty good   If you don’t mind spending some money you can get almost perfectly polar aligned using an electronic device that fastens onto your scope ra axis.  There are two out there, ipolar from ioptron or a polemaster.  You can look them up.   I use a polemaster because I had it to polar align my Meade lx200gps on wedge mount.  It works
Very well and you will be polar aligned to a high degree.  If your mount is level and your polar home positions are good you will get excellent gotos after your first sync.  No need for virtual alignment with the explorestars app.  These devices cost about the same as a great eyepiece.  For me it is an easy decision to spend the cash to facilitate all the rest.  And since you polar align every time you go out you amortize that cost over many uses.  And that is cost against all the lost time and the aggravation of trying to use the polar scope each time.  There isn’t enough dark sky
Time to waste fooling around with polar alignment.   With polemaster or ipolar you will be polar aligned in a few minutes.  And never be on your hands and knees.  Sound good?

If you are going to use exorestars by all means use the 2-3 star alignment for visual use.  It will correct for polar alignment errors, level errors and ra home errors.  I suggest you get your polar home correct tho and this will make your gotos better.

If you are imaging with explorestars you better be at very short focal length.  The virtual polar alignment only keeps the pointing in track during P mode (point mode).    It this mode basically points the scope 5 times a second so there will be jitters noticeable if the fl is much longer than a couple of hundred mm.

If you run explorestars in T mode (track) the mount only goes along in ra.  So basically the 2-3 star alignment is not used.  So you are probably stuck with PMode unless you guide.

So that is my two cents.  If you have the money and insist on great polar alignment get an ipolar or a polemaster.   If not try to get yourself set up with PSAlign pro. Baring that do short focal length exposures with explorestars in P mode.  Or some mix with guiding.

Or you can fight through figuring out polar alignment with a polar scope.  People do get good at it.   


Wes, Southport NC
EXos2-GT PMC-8, iExos 100
ES ED 127, 10" LX200GPS+wedge, Astro-Tech 8" Newt, ETX-90, 60mm no-name guide scope ~ 260mm FL
Polemaster, Orion ST-80 and SAG, ZWO 290MM, D5300 astro modified
Nina, Bootcamped Mac Mini control computer, RDP to iMAC
110 amp hour lead acid deep discharge battery for field power
Electrical Engineer, Retired

Michael Whitaker
Wakefield, UK. 
MOUNTS. Exos-2 PMC Eight..
SCOPE: RVO Horizon 72ed. 
CAMERA: Not Applicable. 
SOFTWARE: Just iPad at moment. 

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