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Pier height recommendations

CedricTheBrave

By CedricTheBrave
in DIY Observatories

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CedricTheBrave

CedricTheBrave

Posted
Posted

I am looking at building a pier in the garden on an old parasol mounting that's concreted into the ground.

Its pretty solid and goes down about 2 feet and 

question is that i have been given some steel tube for the pier but its only 500mm long (6.5" dia) so when the adaptor plate and base is all fixed together it will be about 575mm high to mount the HEQ5pro onto! the OTA is a 200pds. Will this be high enough? or do i need to go higher?

20190101_115942.jpg

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Dr_Ju_ju

Dr_Ju_ju

Posted
Posted

Is it for visual or imaging?  if imaging, as long as everything clears the ground\mount, then it should be ok.

Looking at the location, visual may be a little more trick due to the varying heights around it, and where the eyepiece ends up....

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teoria_del_big_bang

teoria_del_big_bang

Posted
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I am pretty new to this so take my thoughts with a pinch of salt. However, I am also looking into building a fixed pier so am also interested.

I would think a lot has to do with what you intend to do with the scope and what size of scope. If you intend to use for observing then the eyepiece of the scope needs to be at a comfortable height and you need good all round access to be able to view from various angles. But if only intended for imaging with a camera as the ep then the height just needs to be such that it keeps your scope and equipment clear of any surrounding obstacles.

Extra height also may help to a clearer view above house roof, fences or hedges etc but not essential.

Steve

 

EDIT: Basically same reply as Julian above but he obviously was more concise and thus it appeared whilst I was replying ? 

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Cosmic Geoff

Cosmic Geoff

Posted
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That foundation looks good, but the surrounding area looks like a Heath and Safety hazard for working in the dark. There are trip and unguarded edge hazards clearly visible in the photograph.  And positioning an observing chair would be awkward.  If you want to go ahead, I'd advise that you factor in a remodeling and leveling of the whole area in your plans - either lower the ground around or construct a wooden deck with a safety rail around it.

Accidents can happen - I leaned back too far on an observing seat placed on the lawn, overbalanced backward and fell in a flowerbed, whacking the back of my head on a concrete post. Not funny.  The telescope was unharmed.

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mikeyj1

mikeyj1

Posted
Posted

Apart from the visual/imaging consideration, and the longer term reflector/refractor consideration (looking into the top or bottom!), I measured the height of my AZEQ6 for the pier height, and reduced it a bit as i always needed a step up for viewing anything close to zenith.  i've just been out and measured it again its 27" or 700mm from ground to top of pier plate, which is good for my 250pds, although for visual, 75mm less would have been better.

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mikeyj1

mikeyj1

Posted
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11 hours ago, Gina said:

Polar alignment takes care of a base that isn't level

Sorry Gina, but i don't think that's right? 

You could polar align on any out of level as it's not a 'dynamic' process (apart from the RA hour rotation).  A Star alignment of 2 or better 3 stars or more would take out any out of level errors.. as it maps the location of the sky in relation to the axes of movement.  if the plate is level, then a 1 star alignment, from the home position, (such as a GOTO++ in APT is good enough to map the sky...so level is better and quicker, but not essential)

regards

Mike

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Astrokev

Astrokev

Posted
Posted
18 hours ago, mikeyj1 said:

Sorry Gina, but i don't think that's right? 

You could polar align on any out of level as it's not a 'dynamic' process (apart from the RA hour rotation).  A Star alignment of 2 or better 3 stars or more would take out any out of level errors.. as it maps the location of the sky in relation to the axes of movement.  if the plate is level, then a 1 star alignment, from the home position, (such as a GOTO++ in APT is good enough to map the sky...so level is better and quicker, but not essential)

regards

Mike

Isn't that what Gina said, but in fewer words ?

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mikeyj1

mikeyj1

Posted
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2 minutes ago, Astrokev said:

Isn't that what Gina said,

umm no Kev, the point made was that ' polar alignment takes care of a base that isn't level' .   Multi-Star alignment does, polar alignment doesn't ...  

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Astrokev

Astrokev

Posted
Posted
4 hours ago, mikeyj1 said:

umm no Kev, the point made was that ' polar alignment takes care of a base that isn't level' .   Multi-Star alignment does, polar alignment doesn't ...  

If the RA axis is set to point accurately to the pole the scope will track accurately, regardless of the angle of the base. You don't need the base to be level to get the axis aligned with the pole. You could nail the mount to the side of a tree - it makes no difference providing you can align the axis with the pole. Star alignment just improves the accuracy of polar alignment, so obviously has value. 

I like the pier by the way. Top job!

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JamesF

JamesF

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Accurate polar alignment means a non-level base (or a tree-based pier :) is irrelevant.  Once polar aligned the orientation of the base plays no part in whether the mount tracks a target accurately.

But it would be possible to have good alignment of the RA axis and the Earth's axis and still not know where the mount will point the telescope.  Star alignment would fix that.

Having a level pier or base can make life easier if you're drift-aligning as a means of polar alignment because the process can be arranged to make the adjustments to each axis more straightforward.

Because of Skywatcher's "bendy bolt" syndrome, I have actually considered putting a bit of a wedge on the top of my piers to move the alt adjustment bolts to a less "stressful" part of their range.  As it happens I don't think I'll bother.  I'll modify the mounts a different way in the fullness of time.

James

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mikeyj1

mikeyj1

Posted
Posted

I seem to have poked a hornet nest here, but I'm not letting go ?. 

The OP has an HEQ5PRo, so will be using GOTO to find objects, that's key!  James, you're right, (but just let me add an extra bit), whilst its true that good PA will give good tracking, it wont correctly map the sky so the GOTO wont go to the right spot if the base isn't leveled, leading to a lot of frustration or wasted time on multi star alignment to get the GOTO working properly each time.  With a  pier, accurately leveled and reasonably polar aligned,  a one star alignment is all that's needed... I know that as that's what i do.  I wanted to make sure that the OP didn't just take Gina's statement on face value and then wonder why his GOTO wasn't ummm GoingTo..  

I hope clarifying that helps the OP, that was my only intention!

 

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Astrokev

Astrokev

Posted
Posted

The OCD part of me would try and get the mount and base level - indeed that's what I did with mine. 

But I too am sticking by my guns ?.

Star alignment is used to ensure the GOTO system knows where the scope is pointing, so it can subsequently find targets. If the mount is accurately polar aligned, by whatever method one uses, in theory star alignment is then only a calibration in RA. How level the base is is at that time completely and utterly irrelevant. Any base, pier, tripod, or whatever, serves the simple purpose of holding the equatorial head in a fixed position, so that polar alignment does not drift and lose accuracy with use. How it achieves this doesn't matter. The key is to achieve accurate polar alignment, as Gina stated. 

Perhaps we're going to have to agree to disagree on this!

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