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Polar aligning CEM120 with a rubber mallet, compass and ratchet allen key

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#1 pyrasanth

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Posted 24 May 2024 - 11:33 AM

Sometimes when we make a mess of things we have to think out of the box to effect a solution.

 

When I rebuilt my CEM120 dual ring I only roughly polar aligned the Tri pier 360 tripod before installing all the equipment and counterweights. I would guess that installation weighs around 250 ilbs and there was no way to just lift & shift into the right position- I'm not superman and perhaps are more aligned to being weak & weedy TBH but I digress.

 

I took my Silva compass (no electronic gizmo for me) and attached a piece of stretchy string to two bolts about 3 feet long and I aligned this string as parallel as I could to the RA tripod leg along the North/South plane of the compass. Taking the rubber mallet I gently tapped the RA leg and finally the rear legs to get the RA axis leg parallel to the string. This took a lot of gentle nudging as you cant really wack the legs really hard- I was careful to disengage the mount worms as well- after a good few minutes I had a pretty good visual alignment of the tripod RA leg parallel to the string. I don't think the vibrations of the mallet reached the optics as there is a big hunk of metal & counterweights to absorb a lot of the nudges.

 

I then planned to firstly run an alignment using the hit & miss CEM120 IPolar that I had fitted and finally a three point NINA alignment. I did a quick test of the altitude adjustment knob- that great big lump of aluminium with the graduations and.....it was expected locked tight as the retaining altitude bolts had not been loosened. I tried an Allen key to loosen one of the bolts with only an intentioned quarter turn as mentioned in the manual- the allen key was actually bending.... as well as my fingers going blue/white but the bolt would not budge. I resorted to a ratchet 3/8" fitted hex key and that moved the bolt. The other side was not "welded" as bad. I could now finally move the mount in elevation. I tightened the bolts back down ready to come back later to see how succesful I'd been with the compass, string and the rubber mallet beating that I gave the Tri-pier.

 

Well......it has gone cloudy.....its been ages with cloud & rain......I will let you know when I can test.

 

The weather......sucks!

 

I wish all of you clear skies (I will be jealous if you get some).


Edited by pyrasanth, 24 May 2024 - 03:02 PM.

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#2 jdupton

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Posted 24 May 2024 - 12:23 PM

pyrasanth,

 

   Nice story. You have more finesse than I. When I was using my heavy EQ8 mount with EdgeHD 11" and 45 lbs of counterweights in "portable mode", I had to make similar adjustments sometimes. I resorted to the caveman technique of just kicking the pier legs into place for rough polar alignment after setting everything up.

 

 

John


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#3 TOMDEY

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Posted 24 May 2024 - 01:11 PM

The professionals use Sledge Hammers.    Tom

Attached Thumbnails

  • 161 80 24-ft dome foundation N-S monuments theodolite.jpg
  • 160 Tom sighting on Polaris 80.jpg

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#4 Dynan

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Posted 24 May 2024 - 02:16 PM

Any method that uses a hammer (aka persuader) is ok in my book!


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#5 pyrasanth

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Posted 24 May 2024 - 03:08 PM

I like the appreciation of this story so thank you all- but in seriousness it illustrates how hard this hobby can be. We have to think about every single aspect of the installation- even considering the optimal placement of the tripod which is the basic building block of all we do......we can then.....begin the journey!

 

Clear nights to you all.



#6 pyrasanth

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Posted 24 May 2024 - 03:11 PM

The professionals use Sledge Hammers.    Tom

Did you cement the children into the pier for added rigidity?


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#7 TOMDEY

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Posted 24 May 2024 - 05:11 PM

Did you cement the children into the pier for added rigidity?

Alas --- The Springwater Building Code specified 100% steel re-bar reinforcement for all 24-foot observatory foundations and 36-inch telescope piers. PS: Here's that observatory now >>>   Tom

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#8 pyrasanth

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Posted 24 May 2024 - 06:05 PM

Alas --- The Springwater Building Code specified 100% steel re-bar reinforcement for all 24-foot observatory foundations and 36-inch telescope piers. PS: Here's that observatory now >>>   Tom

That's a very nice observatory well done!

 

It sure beats my Telegizmo 365 cover in my garden......but I digress.

 

The sky cleared tonight and I tested with the Ipolar- I had landed within a couple of degrees of the pole- not bad for 2 bolts and and old compass!

 

I quickly dialled the setting to withing 30 arc secs of the pole which at my 805 mm focal length I guess is probably good enough- no need to egg the pudding anymore as they say in England.

 

This is my initial run taken from PHD2 this evening.

 

POLE.jpg


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#9 Xeroid

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Posted 25 May 2024 - 09:29 AM

Question from a visual observer:

Why could you not place say, an 80 or 120 mm refactor or a C6 SCT on the CEM120 + Tri-Pier and then do a Polar alignment with this equipment?

 

I would think that if the Tri-Pier is placed on solid ground, adding weight should not change Polar alignment?

 

What am I missing?


Edited by Xeroid, 25 May 2024 - 02:31 PM.


#10 Blackhawk163

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Posted 25 May 2024 - 03:25 PM

Question from a visual observer:

Why could you not place say, an 80 or 120 mm refactor or a C6 SCT on the CEM120 + Tri-Pier and then do a Polar alignment with this equipment?

I would think that if the Tri-Pier is placed on solid ground, adding weight should not change Polar alignment?

What am I missing?

I think what you’re missing is that the OP setup the equipment without giving it much thought to the actual polar alignment vs the rough alignment done earlier. The cem120/70/40(?) are great in that you don’t have to have any equipment loaded on to polar align as the ipolar is built in the mount.

Our plucky OP just didn’t want to tear down to align the mount, and you know what? As a previous cem120 owner who has setup with the tripier 360, I’ve done the same. Loaded all the equipment only to realize that the pier had shifted in the process (I had outlines on the pavement). No hammer for me I did it by hand. Which was harrowing!

Pyrasanth, you were that off that the az adjustments couldn’t get you to align?

Edited by Blackhawk163, 25 May 2024 - 03:28 PM.

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#11 pyrasanth

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Posted 25 May 2024 - 04:39 PM

I think what you’re missing is that the OP setup the equipment without giving it much thought to the actual polar alignment vs the rough alignment done earlier. The cem120/70/40(?) are great in that you don’t have to have any equipment loaded on to polar align as the ipolar is built in the mount.

Our plucky OP just didn’t want to tear down to align the mount, and you know what? As a previous cem120 owner who has setup with the tripier 360, I’ve done the same. Loaded all the equipment only to realize that the pier had shifted in the process (I had outlines on the pavement). No hammer for me I did it by hand. Which was harrowing!

Pyrasanth, you were that off that the az adjustments couldn’t get you to align?

I went from the RASA 11 on a CEM70 with tri-pier to the CEM120 with the RASA & the Altair ETX-115 on the Tri pier 360- so it was a complete tear down & rebuild. I did not give much thought to the positioning of the new tripod & by eye was simply not good enough. The azimuth was  so far out that I reached the end stops and could move no further. I had no alternative but to center the azimuth controls & manually move the mount as detailed in the post.


Edited by pyrasanth, 25 May 2024 - 04:40 PM.


#12 Blackhawk163

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Posted 25 May 2024 - 08:56 PM

I went from the RASA 11 on a CEM70 with tri-pier to the CEM120 with the RASA & the Altair ETX-115 on the Tri pier 360- so it was a complete tear down & rebuild. I did not give much thought to the positioning of the new tripod & by eye was simply not good enough. The azimuth was so far out that I reached the end stops and could move no further. I had no alternative but to center the azimuth controls & manually move the mount as detailed in the post.


Thought as much! In any case I’m glad you’re up and running.
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#13 555aaa

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Posted 27 May 2024 - 12:25 PM

In my last observatory I used a string to cast a shadow when the sun was on the meridian snd then marked along the shadow line.

#14 rgsalinger

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Posted 27 May 2024 - 01:04 PM

My hat is off to the ingenuity of the OP.

 

I have 3 systems in my observatory that I use regularly. My CEM120EC2 sits on a SkyShed pier which allows for rotation even if the system is already configuresd. Of course after spending all that money my guestimate was within 1 degree. I love those piers which work for pretty much any mount, if you're system will only be used in an observatory setting. 


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#15 pyrasanth

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Posted 27 May 2024 - 05:43 PM

My hat is off to the ingenuity of the OP.

 

I have 3 systems in my observatory that I use regularly. My CEM120EC2 sits on a SkyShed pier which allows for rotation even if the system is already configuresd. Of course after spending all that money my guestimate was within 1 degree. I love those piers which work for pretty much any mount, if you're system will only be used in an observatory setting. 

I have my Paramount MX+ on the SkyShed pier for the C14 setup. This pier sits on a block of concrete 1 metre deep under my lawn. I like the fact that you can rotate the pier head even when your set up. I cut a sheet of paper to make a rudimentary compass stuck to the pier so I could get an idea as to how far I was rotating the pier head- that worked well.


Edited by pyrasanth, 27 May 2024 - 05:44 PM.


#16 ngatel

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Posted 27 May 2024 - 06:52 PM

This is how I do it several times a year at campsites. With a lensatic compass (iPhones are not accurate) I am usually within 1 degree or less of true north. SharpCap quickly gets me to less than 1 arc minute.

 

http://popupbackpack...nsatic-compass/


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