Orpington Astronomical Society

Astronomy => Technical => Topic started by: MarkS on May 14, 2013, 20:11:11

Title: Off Centre Mount
Post by: MarkS on May 14, 2013, 20:11:11

More planning for my observatory.

If I cast a 12" diameter concrete pier, is there any reason why the mount shouldn't sit off-centre as in the photo below (the 12" cardboard disk represents the top of the pier.

By doing it this way, the scope could access far more of the sky before hitting the top of the pier.

(http://www.markshelley.co.uk/webdisk/OffCentreMount.JPG)
Title: Re: Off Centre Mount
Post by: Carole on May 14, 2013, 20:22:04
Looking through the polarscope might be difficult - looking at your picture, looks like the pier might be just where your chin needs to go.  I had this problem with my CG5 GT and I could never do a decent PA because of this reason.

Carole
Title: Re: Off Centre Mount
Post by: Rocket Pooch on May 14, 2013, 20:47:18
Nope thats ok
Title: Re: Off Centre Mount
Post by: MarkS on May 14, 2013, 21:42:54
Thanks Chris.

Carole - if I ever to need to use the polarscope (unlikely) I'll just use a small mirror.  

So I plan to bolt one of these:
http://www.altairastro.com/product.php?productid=16169  (25 quid from an odds and ends bucket at Kelling Heath)
to one of these (300mm diameter)
http://www.ebay.co.uk/itm/Mild-Steel-Plate-Profiled-Disc-10mm-Thk-Various-Diameters-/221214751172#ht_326wt_988
then attach the EQ6 using the centre bolt and then bolt the whole lot down onto thick studs protruding from the concrete pier.

If I change my mount I just need to redrill another 10mm mild steel plate.

Mark
Title: Re: Off Centre Mount
Post by: Carole on May 14, 2013, 22:18:59
You were lucky with the pier plate Mark.

Re: Polarscope, I tried to use a mirror but found it impossible.  Made an adapter to use a webcam on the polarscope, but that wasn't very successful because it didn't sit quite Square add to that an unlit reticle it was a nightmare until I got the NEQ6 which sticks out further.

Carole

Title: Re: Off Centre Mount
Post by: Mike on May 14, 2013, 22:50:21
There are many pieces of software available to do polar alignment without the polar scope at all. I use alignmaster.
Title: Re: Off Centre Mount
Post by: RobertM on May 15, 2013, 18:05:18
I wouldn't worry about the polar scope because of what Mike mentioned.

An even better idea would even better would be something like this: http://www.astrosysteme.at/eng/mount_ddm160.html (http://www.astrosysteme.at/eng/mount_ddm160.html)
Title: Re: Off Centre Mount
Post by: julian on May 15, 2013, 19:35:39
Here's is my setup, which works ok.


(http://farm8.staticflickr.com/7289/8741036005_76b0706b51_c.jpg)

(http://farm8.staticflickr.com/7292/8742151524_acc66b9e39_c.jpg)

Julian
Title: Re: Off Centre Mount
Post by: MarkS on May 15, 2013, 20:15:27
Thanks Julian - interesting to see.

What is the diameter of your pier?

Did you do the metal fabrication yourself - or an engineering shop?

Quote from: RobertM
An even better idea would even better would be something like this: http://www.astrosysteme.at/eng/mount_ddm160.html (http://www.astrosysteme.at/eng/mount_ddm160.html)

Nice!

Mark
Title: Re: Off Centre Mount
Post by: julian on May 15, 2013, 21:43:09
(http://farm8.staticflickr.com/7294/8741445981_2079eca288_c.jpg)

LARGE IMAGE
http://farm8.staticflickr.com/7294/8741445981_fb8128aeb8_o.jpg

Owls nest made by Astro part  01908586747
Title: Re: Off Centre Mount
Post by: MarkS on May 15, 2013, 22:44:13
Wow - detailed measurments of everything!

I can see the owls nest.  Can't see the robins nest!
Title: Re: Off Centre Mount
Post by: julian on May 15, 2013, 23:06:43
QuoteI can see the owls nest.  Can't see the robins nest!

give it time
Title: Re: Off Centre Mount
Post by: Ivor on May 16, 2013, 10:37:20
I'm in discussion about putting a pier in the garden so I'm following this thread with interest. With the cost of the Astair pier adapter I'm keen to see any alternative.

Julian you didn't answer Mark's question about your setup and I'd be interested in knowing

QuoteDid you do the metal fabrication yourself - or an engineering shop?
Title: Re: Off Centre Mount
Post by: MarkS on May 16, 2013, 11:35:19
Quote from: julian
Owls nest made by Astro part  01908586747

I think the quote above was Julian's answer.
Title: Re: Off Centre Mount
Post by: The Thing on May 16, 2013, 12:47:57
Quote from: Mike on May 14, 2013, 22:50:21
There are many pieces of software available to do polar alignment without the polar scope at all. I use alignmaster.

I use AstroTortilla.
Title: Re: Off Centre Mount
Post by: The Thing on May 16, 2013, 12:51:23
Quote from: Ivor on May 16, 2013, 10:37:20
I'm in discussion about putting a pier in the garden so I'm following this thread with interest. With the cost of the Astair pier adapter I'm keen to see any alternative.

Julian you didn't answer Mark's question about your setup and I'd be interested in knowing

QuoteDid you do the metal fabrication yourself - or an engineering shop?


I have read of a Skoda brake disc being used to make an HEQ5 pier adaptor as the hub part is just right for the head to sit in and there is plenty of metal for bolt holes. I wonder if there is a disc which would work for an EQ6?