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Concrete pier is not in center of dome -- is this a problem?

Astrophotography Equipment Mount Observatory
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#1 sheakev

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Posted 14 June 2021 - 05:56 PM

Hi,

I am looking at buying a winter home (in dark skies).  It comes with an Ash Dome (I believe 16.5')  The concrete pier (36") is not in the center of the dome.  It was offset to accommodate a 24" telescope and its mount (see drawing attached).  With the offset of the large mount the telescope was in the center.  I have a much more modest mount and telescope.

 

The dome is automated, although it hasn't been operated in about 9 years.  I am hoping that I could mount my SB Paramount MX+ on the pier with my 130mm refractor scope and somehow it would all work -- but I have no basis for that "hope".

 

I could get a large plate, bolt it down to the existing pier plate and cantilever the plate such that my MX+ would be centered in the dome.  If I could avoid this it would make life simpler (maybe).  I was never good with trig or geometry so I am having a problem visualizing how such an offset would affect the ability of the dome and scope to rotate and track in synch.  Any comments, Ideas, or questions would be very welcomed.

 

Thanks,

Kevin

 

 

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#2 LuscombeFlyer

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Posted 14 June 2021 - 06:40 PM

Geometrically, you shouldn't have a problem. The dome moves in azimuth only, and the azimuth of any particular object is independent of the pier position. But... this sounds like a perfect justification to buy a 20" Ritchey-Chr├ętiensmile.gif


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#3 Taosmath

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Posted 14 June 2021 - 07:29 PM

I think the biggest problem you will have is that the top of the pier is 4' below the sidewalls of the dome.

 

You therefore will not be able to bolt the MX+ directly to the top of pier unless you are willing to lose access to the lower part of the sky (Maybe that's OK since the seeing's bad anyway at low altitude )

 

Anyway without seeing more measurements, my guess is you will have to mount a pier extension  (3' or more maybe??) on top of the concrete to get the mount high enough, (and the extension will also have to be high enough to let your imaging rig clear the top of the concrete ).


Edited by Taosmath, 14 June 2021 - 07:31 PM.

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#4 kathyastro

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Posted 14 June 2021 - 07:58 PM

The only issue is mechanical: will the scope clear the dome in any position?

 

The synchronization issue is not a problem.  All dome sync software needs to be told where the mount is in relation to the centre of the dome.  No software expects it to be perfectly centred.  You just tell it where the intersection of the RA and Dec axes is in relation to the dome's centre, in three dimensions, and it makes the calculations accordingly.


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#5 TOMDEY

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Posted 14 June 2021 - 08:33 PM

Hi, Kevin!

 

Nice Dome and interesting concern. It looks like the 24" was on a fork mount? That enjoys the advantage of staying centered E-W. Your German Equatorial will be off to the side most of the time, which also enters into the mix. That massive pier would certainly accommodate interfacing your mount north with no issues. The scope to dome geometry, new installation... two steps:

 

1) assure that your mount, scope, any/all intended instruments, in all allowed pointings and flips etc. cannot possibly hit the dome, in all rotations.

2) buy or develop the software to relate your pointing to the corresponding best centered dome azimuth.

 

 I always wrote my own, but that was long ago. I gota believe that kinda stuff would be available in free-ware now. The dome and mount guys would certainly have that or point you in the right direction (feeble pun).    Tom

 

PS: An observatory that has seen no use in nine years can suffer a lot of distress from the elements and infestation (hornets, ants, termites, birds, bats, mice, snakes, mammals). Would want inspect and hopefully exercise the rotation and shutters before jumping on the deal maybe. Dark Skies sure get one's attention!    Tom


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#6 sheakev

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Posted 14 June 2021 - 09:53 PM

Wow, thanks to everyone who responded, every post had a big nugget of wisdom!

 

I believe the original scope was a 24" RC by RC Optical Systems.  Pretty sure it was a fork mount

 

It is a Bortle 1 site at around 4100' elevation



#7 kathyastro

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Posted 15 June 2021 - 05:00 AM

 

I always wrote my own, but that was long ago. I gota believe that kinda stuff would be available in free-ware now. The dome and mount guys would certainly have that or point you in the right direction (feeble pun).   

Here you go.  As long as you have ASCOM drivers for the mount and dome, this will do it: https://www.dropbox....ncV3.0.zip?dl=0


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#8 astrokeith

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Posted 15 June 2021 - 05:26 AM

You could get some steel welded up to a) lift the mounting point by 4' and b) centre the mount as far as necessary.

 

Incorporate some equipment shelves into it and it will look as if it was always meant to be like it!


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#9 Chucke

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Posted 15 June 2021 - 03:57 PM

I don't suppose you are looking at the old Light Buckets property are you?  They had a 24" RCOS in a pretty big dome at about 4100' an a probable Bortal 1 site.  It is about 5 miles down the road from me.



#10 PastorBillV

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Posted 15 June 2021 - 05:16 PM

https://planewave.com/tools/

 

OptCorp used this spreadsheet to help me setup my TI dome around my pier. 

Good luck!

Bill


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