Home position on mounts.

[Robindonne]

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 

Edited April 28, 2020 by Robindonne

[Robindonne]

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?

Edited April 28, 2020 by Robindonne

[Cornelius Varley]

6 minutes ago, Robindonne said:

What is wrong with polaralignment through the polarscope and after that aligning the mainscope on polaris?

The purpose of polar aligning is to align the mount on the north (or south) celestial pole. Polaris in the Northern hemisphere is just a convenient nearby star for doing this. The telescope should also be pointing at the celestial pole in its home position. 

[Jiggy 67]

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 

[miguel87]

Yeah, more accurate using the polar scope in the mount. I know its awkward to look through (I sit on the floor!) But you can buy a 90° attachment that makes it a doddle.

[Jiggy 67]

1 minute ago, miguel87 said:

Yeah, more accurate using the polar scope in the mount. I know its awkward to look through (I sit on the floor!) But you can buy a 90° attachment that makes it a doddle.

I use one, makes a huge difference, worth the £60

[Robindonne]

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. 

[Robindonne]

9 minutes ago, miguel87 said:

Yeah, more accurate using the polar scope in the mount. I know its awkward to look through (I sit on the floor!) But you can buy a 90° attachment that makes it a doddle.

No i dont really mind sitting on my knees and bending my neck like 100 degrees😅

[Robindonne]

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?

[Cornelius Varley]

1 minute ago, Robindonne said:

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?

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.

[Robindonne]

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. 

Edited April 28, 2020 by Robindonne

[Cornelius Varley]

Just now, Robindonne said:

The celestial pole is where my mount should be pointed at and also my mainscope in home position?   Im confused. 

This is correct.

[miguel87]

10 minutes ago, Robindonne said:

But when you polar align through the mainscope?

You should never be polar aligning through your main scope. 

If your mount is aligned then your scope WILL be pointed at the north celestial pole in home position.

Edited April 28, 2020 by miguel87

[Robindonne]

2 minutes ago, miguel87 said:

You should never be polar aligning through your main scope. 

So the asiair and sharpcap polaralignment methods make no sense?

Edited April 28, 2020 by Robindonne

[Carbon Brush]

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.

[miguel87]

2 minutes ago, Robindonne said:

So the asiair and sharpcap polaralignment methods make no sense?

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.

[Robindonne]

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?

[miguel87]

5 minutes 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.

Your skywatcher mounts have this in the polar scope. Makes it super easy, just get polaris in the circle.

[Robindonne]

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?  

[miguel87]

Just now, Robindonne said:

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?

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.

[miguel87]

2 minutes ago, Robindonne said:

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

Polar align so that I can follow things across the sky using just the motor or turning 1 axis.

Without polar aligning my mount wont track stuff and I have to fiddle with tow knobs to keep track of things.

Edited April 28, 2020 by miguel87

[Stuart1971]

Personally, I would never use a polar scope as the chances are that they are not perfectly aligned with the mount..or aligned within there own tube, they can be calibrated but I would not bother.....

Use a scope and a camera and use sharpcap, or even better buy a polemaster camera...

As for home position it is a good idea to mark on the mount the home position so you can repeat this, a small sharpie mark on the mount will help...

[LongJohn54]

It's sometimes easier to watch a short video where someone explains why a good home position is required whilst showing you how to do it.

https://www.youtube.com/watch?v=4fO6hyYtPwM

 

[miguel87]

1 minute ago, LongJohn54 said:

It's sometimes easier to watch a short video where someone explains why a good home position is required whilst showing you how to do it.

https://www.youtube.com/watch?v=4fO6hyYtPwM

 

I think we are confusing things here.

Depends what the OP is doing.

For visual astronomy there is no need to mark a home position or even know where one is.

For photography it may be different.

[Robindonne]

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?  

Edited April 28, 2020 by Robindonne