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Robindonne

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Posts posted by Robindonne

  1. 13 minutes ago, CraigT82 said:

    In theory yes. But difficult to achieve in practice. Depends on the resolution you're imaging at (or focal length if visual). Some expensive mounts don't require guiding at all, they use sky models and encoders to know exactly where they are pointing. 

    Thx.  Im aware the scale we are using with astronomy is not imaginable with earth sized calibration possibilities.  That I underestimated i think.  My questions were mostly raised due to all these graphs?? Of guiding accuracy.  It looks like their is always adjustment of the tracking needed and the less adjustment the better of course.  But getting a straight line without adjusting is just not possible it seems. Thank you again for the info.  Ill never have to ask it again after this chat. 

  2. On 28/04/2020 at 18:41, Grierson said:

    Why? If you have the ASIAIR the Polar Alignment process in the software is more than capable of producing the required accuracy. I can see little or no difference between using the PoleMaster or the AIR or indeed SharpeCap for that matter!

    No well than im happy with your advice and just plan my future set without paying much attention to the whole polarscope/polemaster.  I think if i never got to know asiair Or sharpcap my answer would also be: polaralignment can only be done with a polarsope.  Thx

  3. On 28/04/2020 at 18:23, CraigT82 said:

    No I dont think so, even changing primary collimation on a newtonian will introduce cone error

    Thanks. Thanks all answers but this cone error reason answer in particular.  
     

    To make a happy end on this conversation a last question.  If you somehow manage to reduce cone error to almost zero. Let say by calibration in whatever form. Turning a newtonian or refractor in its rings or some other methods for other scope types.  And having a perfect polaralignment.  Will it reduce the amount of help movements of the second motor for accurate guiding?   Or will their always be slight(minimal) differences in starpositions? I mean a minimal off the equatorial axes movements.

  4. 9 minutes ago, CraigT82 said:

    Have you heard of cone error? It can be quite difficult to have the main scope optical axis exactly aligned with the mount's RA axis, especially with moving mirror scopes.

    Aah.  Thats i think some missing info in my head.  And that error can occur in both directions of course.  So my fixed homeposition is not even possible when changing scopes?

  5. 17 minutes ago, miguel87 said:

    It could in theory but why worry when you can just use the mount and be done with it rather than worrying how well aligned your main scope and mount are, marking home position etc etc.

    Align mount. Done.

    So rebuy a polemaster and forget about asiair polar alignment? I hate the idea of bringing a laptop and still believe a good polaralignment is possible in some minutes with a solid homepositioned mainscope and without kneeling or using a polemaster and its laptop.  

  6. 9 minutes ago, miguel87 said:

    Great method, exactly as I use.

    So I dont understand why you need a home position?

    I dont have one marked, dont need one.

    My scope could be pointing due west when I align the mount. Doesnt matter, it is still polar aligned.

    I agree with all the answers.  And maybe im to confused to see your points.  Or maybe im confused about the polaralign methods using asiair or sharpcap.  Im really just starting astronomy for some months. Im more experienced with making wooden  stairs on my cnc machine.  And if my axes are not calibrated perfectly the straight line im planning to route through wood will always need some movement of my second steppermotor.  And thats where things go wrong i guess.  I thought a good polaralignment means guiding uses only movement of one motor
     

    So to understand all of your answers.  Polaralignment can never be done accurate through the main scope?  

  7. 2 minutes ago, miguel87 said:

    You are just adding another potential cause of inaccuracy (finding the home position PRECISELY).

    If you can polar align with the mount it is a better option as this dictates the position of the RA and dec axiis. And the scope on the mount is automatically aligned.

    If you align via the main scope and you are not exactly in home position then the RA and dec axiis will be lined up wrong.

    Yes that’s exactly my point.  Whats the use of polaraligning without a solid homeposition?  

  8. 1 minute ago, Carbon Brush said:

    Some polar scopes have internal markings to help with alignment.

    I have seen (or used) one with a circle, size to represent the circle of polaris, another with a rough map of bright stars near polaris, with a small circle where you put polaris.

    HTH, David.

    Yes i have the same small map of the area around the celestial pole in my polarscope.  And of course i use it and align it as perfectly as i can with my ps-align app.  It gives me a accurate position of polaris in that “clocklike map” in the polarscope i hope.  But my initial question was why we all have to mark our own homeposition on our mounts? Unless you have damaged or bent the bracket on top or the dovetails on your scope, and need to re-align both parts.


     Dont we all have our home position on the same spot?

  9. 4 minutes ago, Cornelius Varley said:

    The polar scope, when accurately aligned, should be pointing at the celestial pole not Polaris. The polarscope and telescope should therefore be pointing in the same direction.

    Okay I understand that its not the same point.  Pls forget the polaris mentioning from me.  The celestial pole is where my mount should be pointed at and also my mainscope in home position?  So whats the point of not marking the home position during the production of the mount? Im confused. 

  10. 13 minutes ago, Jiggy 67 said:

    An accurate home position is needed so a GoTo handset knows where it’s starting from and pointing. I have a perfect home position which I keep with markings on the mount so I can repeat it anytime. I don’t think there’s a need for a factory fitted home position 

    The scope has nothing to do with polar alignment, it’s the mount you are aligning not the scope as it’s the mount that moves to follow the object you’re observing. If you have an accurate home position, the scope will just follow the mount, I don’t understand how you would align the scope on Polaris and what that would achieve 

    But when you polar align through the mainscope?

  11. Thanks for replying. So basically im wrong with assuming that when you have perfect polar aligned your mount, the main-scope in its home position, is not facing the same direction as the polarscope?   But let say i polar align through my main-scope, with asiair for example. Shouldn’t the end-result mean my main scope is also perfectly aligned with my polarscope.  
    And also be in “home position” after this alignement?

    And thus all mounts all over the world have the same home-position marks?

     

    im trying to find ways to smooth guiding without much movement on both axes. 

  12. Oh and maybe a second question related to my first.  A lot of tutorials tell you how to determine the home position of a mount. By leveling in both directions.   What is wrong with this other method: polaralignment through the polarscope, and after that, aligning the mainscope on polaris?   Shouldnt this “alignment of both scopes”, the polar- and mainscope not give a more accurate homeposition than leveling the axes?

  13. Hello to you all.  I’m not really a writer, more a reader on this forum. But as a somewhat starter with all that’s related to astronomy i cant seem to find an answer for this question.  What is the reason my mount, and probably my future mount,(planning to move from eq5 to eq6) dont have marked homepositions? Im planning my future setup and want to avoid polar alignment through polemaster or polarscope(i sold my polemaster that came with my first set, didnt know why i should need it😬😬). So i sold it and now im starting to see the needs for it. But planning to polaralign with my scope and asiair i think the need of a fixed homeposition should be very useful for this action.  When my handmade markings are a bit off then my whole polar alignment will be off for the time im using this method.  And i hope to use this method for a long time.   Less is more i hope and really love the polar alignment through the mainscope.  Or am i thinking wrong?   Shouldn’t factorys mark a zero point on their mounts?   Sorry for my dutchie english.  
     

     

    edit: maybe the newer mounts have it and im just not aware of it.  Then sorry for bothering 

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