Hello Mathew
No I do not have automation.
My ob is on the geologically ancient Yilgarn block which has very deep weathering.
Thus a clay subsoil to a great depth.
The link above describes the pier and its placement.
Even this large chunk of concrete moves around with the seasonal change in soil moisture. This is not a problem, it just requires polar alignment every month or so.
For photography the pier is rock solid, with a Mesu 200 MK1 on top guiding with PHD2 easily accommodates the polar alignment error,(down to .25 seconds RMS on a good night..
My floor is a 3 metre square , in placing it I did not make sufficient foundations and it has acquired a north/south slope.
Chris
Thanks Chris. I have deep clay as well so have the same problem. Maybe I’m better to try to go deeper with the pier foundation… will definitely look at some additional foundations for the slab though, that’s very good advice. Thanks, Mat 👍👍
Even with a simple 4" slab, neither my 2.3m or 3.5m observatories induce vibrations in the mount whist turning. I can get a vibration if I jump up and down, but that isn't part of my imaging workflow
The downside of the otherwise superbly built Sirius 2.3m dome is that the aperture is rather narrow by modern standards - these were designed when an 8" SCT was a monster of a scope. I did have a 14" in mine, but it was hard to keep it central even with automation.
Thanks Jonathan! I’m considering whether I hedge my bets since I’m on clay and do a foundation that is T-shaped in cross section so I have a deeper element as some floating towards the surface that might help resist any sideways movement. Good point on the slit width -I see astrodomes have a 900m slit for their 2.4m dome. Thanks, Mat
I chose not to mechanically couple my pier to the dome floor.
BTW Mike and Trish's (non-Sirius) dome (I recall they had some building progress shots) is definitely one of the more impressively planned and engineered domes in Oz.....if you needed template, theirs is flawless.
Thanks Peter, I’ll see if I can find that thread. Cheers, Mat
Quick take from my experience. Sirius and Scopedomes both have a “premium” finish and feel, but I can’t comment on current pricing, either would make a fine home.
My Nexdome by comparison is utilitarian and functional but suited my purposes and budget at the time of purchase, but it does lend itself toward someone comfortable with tinkering to setup and fine tune issues resulting from less than precise manufacturing tolerances.
The benefit is that it’s as close to a flat pack dome as you’ll get and to Martin’s point, it holds up to weather well.
One thing to note, if disturbing the neighbors or co-habitants with the sound of the dome moving at night is a potential issue, then the Nexdome is notoriously “clunky” and might not be the best choice, in my experience.
Thanks Paul. The NexDome pricing is very attractive. Luckily my obs will be well away from neighbours 😀 I’m hoping to avoid too much tinkering - the best option in that regard is the Scopedome 2m which comes full assembled so pretty much plug and play. The 2m is a bit smaller than the other options but has a similar slit width. I’ll be running it remotely and it might just work hmmmm.
Thanks Jonathan! I’m considering whether I hedge my bets since I’m on clay and do a foundation that is T-shaped in cross section so I have a deeper element as some floating towards the surface that might help resist any sideways movement. Good point on the slit width -I see astrodomes have a 900m slit for their 2.4m dome. Thanks, Mat
I'm on clay rich soils too and had a level platform cut and compacted for the astro-toys. Amazingly and despite over a metre of rainfall in three days during the recent flooding events, when I went to polar align the big scope, it had only shifted by a few arc seconds. The larger dome went in 10 years after the smaller on, so the ground had plenty of time to settle!
Our house had some decently deep pining to keep it from moving like you suggest - a 10" auger hole sunk as far as you can be bothered will do the trick. Dig out a few other holes in the garden at the same time and fill them with decent soil - it's a great way to establish shrubs quickly
I have professionally installed a few observatories around Oz and recommend the following for a Sirius dome.
To remove any possibility of induced vibration, provide ventilation and reduce condensation and reduce local seeing from the thermal inertia of a 12+ tonne slab ( I'd suggest the thermals would be impressive in summer) mount the observatory on low deck.
If you really want to get fancy, make it really high deck to get above ground turbulence/seeing ( Perth Observatory, did this in extreme with their 61cm Lowell telescope..amazing what a little support , read $$$, from NASA can achieve) .
The pier should be isolated from the deck. AC sheet ( used in bathroom floors) or Modwood are good weather and fire resistant low maintenance choices for the decking surface. Make the deck wide enough to allow you to walk around the dome for cleaning, servicing. Nothing too hard about this, but certainly worth getting right at the planning stage.
One thing I should have pointed out is the creepy crawly factor. In the case of my Warrambungles dome, the mud wasps will find their way into just about any opening into your dome or RoRo - same goes for spiders (which the mud wasps hunt), this is another area where the Sirius and ScopeDomes offer an improved degree of protection - the Nexdomes are far more open to dust ingress and bugs.
Not matter what you go with, strongly recommend budgeting for either a dehumidifier (plumbed into the dome so you dont have to empty it) and/or a chiller (ideally this can also dry the air), depending on how warm your dome gets. It sounds extreme, but as Peter mentioned, heat (and dew) is your enemy.
I have professionally installed a few observatories around Oz and recommend the following for a Sirius dome.
To remove any possibility of induced vibration, provide ventilation and reduce condensation and reduce local seeing from the thermal inertia of a 12+ tonne slab ( I'd suggest the thermals would be impressive in summer) mount the observatory on low deck.
If you really want to get fancy, make it really high deck to get above ground turbulence/seeing ( Perth Observatory, did this in extreme with their 61cm Lowell telescope..amazing what a little support , read $$$, from NASA can achieve) .
The pier should be isolated from the deck. AC sheet ( used in bathroom floors) or Modwood are good weather and fire resistant low maintenance choices for the decking surface. Make the deck wide enough to allow you to walk around the dome for cleaning, servicing. Nothing too hard about this, but certainly worth getting right at the planning stage.
Thanks Peter. I will definitely look at having the pier foundation separated from the dome support, if I use concrete will looks at some silicone sealant between the 2 slabs for moisture control. A deck is an option but the ground gets fairly wet over winter so moisture control is a consideration. Not sure if I can get planning approval for the dome to be any higher than it is 😂
One thing I should have pointed out is the creepy crawly factor. In the case of my Warrambungles dome, the mud wasps will find their way into just about any opening into your dome or RoRo - same goes for spiders (which the mud wasps hunt), this is another area where the Sirius and ScopeDomes offer an improved degree of protection - the Nexdomes are far more open to dust ingress and bugs.
Not matter what you go with, strongly recommend budgeting for either a dehumidifier (plumbed into the dome so you dont have to empty it) and/or a chiller (ideally this can also dry the air), depending on how warm your dome gets. It sounds extreme, but as Peter mentioned, heat (and dew) is your enemy.
Thanks Paul -I am not a fan of spiders so that is a good point in favour of Sirius and Scopedome 😂 I am thinking about putting a small split unit heat pump in there for controlling temp and humidity. I have been looking at Lunatico Dragonfly for an IP controlled power switch to control all of this.
