Pier position in 2.3 metre dome

[pmrid]

I have a 2.3 metre Sirius dome on a pallet and am deciding whether to erect it now or keep it for "later".
Part of that process of mulling it over involves the tricky question of where to position the pier in the dome.
The designs I have seen all seem to be for fork-mounted scopes and the pier is located more or less against one wall. But all my mounts are equatorial and my interests largely in imaging.
What is the conventional wisdom on this??

Peter

[Tandum]

Peter, on the SkyShed Pod site (http://www.skyshedpod.com/), under more info, is a downloadable program to let you see different scopes and pier positions in a pod. The pod has a smaller radius and is shorter but it may be worth a look. It's all in inches though I think.

[bert]

Equatorial forks are better offset to the north. I had a pme and 12.5 rc mounted in a 2.3 Sirius and trust me you want it smack in the middle for clearance.

Brett

[rally]

Peter,

Unless you have a very large OTA that might require clearance considerations, the best spot is to position the intersection point of your mounts Dec and RA axis at the centre of the dome.

That usually means there will be some slight offset of the centre of the pier to the centre of the dome. But it may not be great.
If the OTA is small then it becomes less relevant as the slit will always be wide enough !

If you are automating the dome, the dome controller software will automatically calculate any dome slit offsets to counter the RA movement of the equatorial mount about the centre of the pier. The larger the OTA is with respect tot he dome slit - the more this matters.


Rally

[allan gould]

Peter
as above however there are a few considerations that you must also make. Don't place your door either due east or west, offset it slightly as when you enter the dome you may bump directly into either the scope or the counter weights as you enter. Also make sure that when you setup that where the computer is placed in one of the insets or bays that you won't get in the way of the scope etc.
The best advice is place the pier in the center of the dome and allow sufficient height to easily see your horizons or near enough.
Just my 2c, Allan

[pmrid]

Thanks everyone. I am grateful for the input. As always.
Peter

[ChrisM]

Peter, the above advice seems good.

I offset my pier so that my fork-mounted scope would be central - and that worked fine.

Then I upgraded to an equatorial mount with a much larger scope. The dome slit is probably on the narrow side, being just 700 mm in a 3.6 metre dome, and the pier is offset 250 mm North of centre. I was surprised how much off-centre the scope is especially when looking at objects close to the meridian. Objects close to the zenith require crazy dome positions, but I can always manage to get a 'full' view. Any larger aperture would not work!

So if there is a lesson in all of this, it would be to do some modelling first!

Good luck

Chris

[trek1701]

The Sky Shed Manual probably suggests mounting your scope off centre because it can’t archive reaching zenith due to the design of the dome.
I could be wrong.

Cheers Mark

[allan gould]

Peter
I have the 2.3m dome and an equatorial mount in it. If you would like to see the setup just pm me.
Allan

[Tandum]

This is an old thread allan. I believe the dome is now gone.

[bojan]

Have a look at drawing I did for my 10" Newt on EQ6.
I also intend to place all that under the Sirius dome.
http://www.iceinspace.com.au/forum/attachment.php?attachmentid=105342&d=1323580363

[Barrykgerdes]

Where you put the pier will depend on a number of things and what is good for some may not suit you.

The first thing to know is your latitude. This will determine the fine location of the fulcrum about which your rotational tracking will rotate.

In a Fork mounted telescope this will be the centre of the axis of declination. This needs to be at the centre of your dome and the pier will usulally need to be offset to accomodate this.

On a GEM the center of rotation will be the basically the same position. The point where the declination axis and OTA Axis intersect along the centre line of the RA Axis

If you have a heavy scope that needs to be mounted equatorially allow for a crane of some sort to plumb this centre.

This is my design for a Sirius 2.3 metre dome

http://barry.sarcasmogerdes.com/observatory/programs/obsvatry.doc

Barry

[mithrandir]

Barry the URL is wrong. This one (http://sarcasmogerdes.com/observatory/programs/obsvatry.doc) works.

[Barrykgerdes]

that's odd. It works for me

Barry

[mswhin63]

The original is a local intranet link so it would have worked fine.