Mount turning circle questions for attic observatory

[eshy76]

Hi everyone,

I've been searching furiously for this and have not really found an answer, so forgive me if this has been asked already.

Background: I'm having my house renovated and the possibility has come up for an attic observatory of sorts (I currently image from the garden and set up and tear down each time). My builder can see the passion I have for astro-imaging and really wants to come up with a solution for me! 👍 A fixed garden observatory is not feasible from a family and trees perspective. I've read at length about potential issues such as vibrations and thermals rising from the house and I'm working with the builder to minimize these, so this post is not really talking about those things. I have also seen the other attic observatory threads on this site, which are inspiring!

Questions: It is looking like I will end up having a sliding rooflight of about 1.1m squared....probably powered....so what turning circle for the mount and scope do I need to be worried about to not "hit the edges" of the frame when opened? Does that rooflight size sound ample for say an 8-9.25" Edge HD + appropriate mount? Has anyone making their obsies had to worry about the opening above mount and scope?

The idea is to have the scope and mount "parked" at an angle just under the rooflight (it is almost a flat roof) and then "unfold" it all when the rooflight is opened to maximise the height of the OTA above the house once in the open air. I could consider a motorised rising pier if that would work better.

Am I right in saying the key dimension is along the counterweight bar, through the mount and across the width of the OTA...for e.g. when imaging near zenith? 

I currently have a CEM25P, William Optics Z73 and a scope mounted PC, and measuring along the counterweight bar line, gives me about 71cms, so the 1.1m rooflight seems to be ample for that, but I am anxious that the size of the rooflight might seriously hamper upgrade options for mount/scope...at a minimum I would look to upgrade the mount. And it's not always a dimension mount manufacturers disclose....

Any guidance/shared experience would be helpful - I can still cancel the whole thing and keep imaging from the garden if it is not going to be worthwhile, although a permanent setup and uninterrupted skies are extremely tempting!

Many thanks!

 

[WanderingEye]

Nice idea, am watching this thread with interest.... 😀👍

[eshy76]

2 hours ago, WanderingEye said:

Nice idea, am watching this thread with interest.... 😀👍

I will keep updating it as progress is, or isn't, made!

After more hasty research (I have to move quite quickly on this), I am leaning towards a Linak DL2 motorised column approach....if I can get the whole kaboodle through the gap, then maybe the whole turning circle thing is irrelevant....? Park scope diagonally across hatch (1.1m squared is 1.56m diagonally)...open hatch...raise column...and we're away...?

[old_eyes]

There is a model that allows you to work out the swept volume of a scope on a German equatorial mount https://www.blackwaterskies.co.uk/2013/12/observatory-planning-and-german-equatorial-mounts/

I used this to work out the minimum spacing around the scope for my ongoing observatory build. I found it easy and very useful.

 

[eshy76]

8 minutes ago, old_eyes said:

There is a model that allows you to work out the swept volume of a scope on a German equatorial mount https://www.blackwaterskies.co.uk/2013/12/observatory-planning-and-german-equatorial-mounts/

I used this to work out the minimum spacing around the scope for my ongoing observatory build. I found it easy and very useful.

 

Boom! I ask and the SGL community delivers....that is pretty much spot on what I was looking for - time to dust off the old A-Level maths and crunch some numbers...if the sphere of rotation works out, I won't need to spend on the rising column...although that looks like a solution could increase what I put up there.

Thank you very much!

I will keep updating the thread as progress is made.