A simple fix to wind issues for the ones who can't afford an observatory
Hi Guys,
Just put up a wind shield to block off those gusty winds at night. Its kinda pove but works. now it is fully shielded with the other side blocked by neighbours fence and garage.
I find that the straight head-height walls of my observatory are no good for preventing wind hitting the scope, in fact I wonder if they're worse. I find that the wind ripples over the top of the walls resulting in quite a lot of turbulent wind within the open half of the shed.
I suspect for me the actual result is probably no different to not having walls, because either way the scope gets shaken around, but to someone standing inside the observatory it's obvious that the wind is swirling around in a turbulent way rather than just blowing through.
A dome pointed away from the direction of the wind would be nice one of the reasons that in my observatory's current location I would prefer a dome to a shed.
I have often considered what a good aerodynamic design would be for an open roof/roll-off-roof shed would be to prevent wind disturbance, where the wind is directed overhead without touching the scope.
You will find that understanding a little bit about aerodynamics and basic air flow will help you too.
If you have the wind-break closer to the mount you will have more success. At the distance you have it in your pics, you will get swirling air flow up and over the tarp and buffeting around where your mount is. If you can confine the area more, the current should flow right over the top and down the other perimeter wall.
Your best option is to surround the mount with a windbreak only about 1m either side of the mount. Height can be kept down to about the height of the top of your scope or if you want, 200-300mm higher, so you won't be blocking any sky that way.
you want to hope it doesn't rip your guttering off or the lattace work on the fence, huge sail area there
hmm but is the wind really strong enough to do that?
Quote:
Originally Posted by rogerg
Interesting that it works for you.
I find that the straight head-height walls of my observatory are no good for preventing wind hitting the scope, in fact I wonder if they're worse. I find that the wind ripples over the top of the walls resulting in quite a lot of turbulent wind within the open half of the shed.
I suspect for me the actual result is probably no different to not having walls, because either way the scope gets shaken around, but to someone standing inside the observatory it's obvious that the wind is swirling around in a turbulent way rather than just blowing through.
A dome pointed away from the direction of the wind would be nice one of the reasons that in my observatory's current location I would prefer a dome to a shed.
I have often considered what a good aerodynamic design would be for an open roof/roll-off-roof shed would be to prevent wind disturbance, where the wind is directed overhead without touching the scope.
THanks Roger. Because the wind shield is directly facing north (you can see where my EQ6 is point at), it does help slightly with the west wind since west wind is always stronger.
Quote:
Originally Posted by ballaratdragons
Eric,
You will find that understanding a little bit about aerodynamics and basic air flow will help you too.
If you have the wind-break closer to the mount you will have more success. At the distance you have it in your pics, you will get swirling air flow up and over the tarp and buffeting around where your mount is. If you can confine the area more, the current should flow right over the top and down the other perimeter wall.
Your best option is to surround the mount with a windbreak only about 1m either side of the mount. Height can be kept down to about the height of the top of your scope or if you want, 200-300mm higher, so you won't be blocking any sky that way.
I was thinking exactly that Ken. Moving it closer to the mount only "after" I mallet the metal rods down to the ground. Tried pulling it out, no go..
I find that the straight head-height walls of my observatory are no good for preventing wind hitting the scope, in fact I wonder if they're worse. I find that the wind ripples over the top of the walls resulting in quite a lot of turbulent wind within the open half of the shed.
I've heard (haven't tried this myself) that you can stop this sort of turbulence if your windbreak is a bit porous - eg if you build a paling fence as a windbreak then leave small gaps between the palings, and also leave a gap under the bottom of the fence between the fence and the ground.
This all helps (apparently) to stop low-pressure regions forming behind the wind break where you and your scope are hiding.
I'll be trying this for myself shortly, I'm building a 2.5m high paling fence around teh concrete pad where I have my pier - I'll let you know if it works, or if it's all ...umm... hot air :-)
hmm but is the wind really strong enough to do that?
Wind pressure will vary directly to the square of the wind speed. Therefore a small increase in the wind speed will result in a much larger increase in the pressure. Here is some stuff I found on the web.
A wind speed of 7.5mph will produce a force of 1.5 lbs/sq m.
A wind speed of 12mph will produce a force of 4 lbs/sq m
A wind speed of 18mph will produce a force of 8.6 lbs/sq m
A wind speed of 24mph will produce a force of 16 lbs/sq m
A wind speed of 30mph will produce a force of 26 lbs/sq m
So, if the wind is gusting at 24mph (38kph), and your tarps have an area of say, 10sq m, then the loading will be equivalent to 160lbs, or 72kgs.
At 30mph (48kph), it will be 260lbs or 118kgs.
These are not small forces and personally, I would be concerned with anything lashed to the gutter.
Hi
before I embarqued on my poor man's observatory project I'd een using nothing but a wind screen around my scope (which was left out under a tarp in between sessions.
Here's how I designed it:
using mainly corrugated iron sheets (mostly zincalum type stuff and a few plastic/fiberglass ones) the kind used for roofing, I created a circular screen around the scope , 3 meters diameter, and about 5 foot high, not quite as tall as me.
(i'd used star pickets and tacked the sheets to those )
I ensured that the wall of the screen had a small incline towards the center, basically making the screen a bit conical, not a whole lot but basically, the whole at the top was slightly smaller than the diameter of the base. This angle was to account for the dynamics of air flow turbulence.
it looked horrible (recycling various metal/fiberglass parts different colors etc) , but did the job fine, in a terribly windy region.
dismantled now unfortunately, I cant post pics of it...
hmm but is the wind really strong enough to do that?
Depending on how well made the tarp and its eyelets are - a big wind may just tear them out.... A well made tarp/rope and a good wind may just pull the guttering off or damage it.....
one of the reasons that in my observatory's current location I would prefer a dome to a shed.
Tried pulling it out, no go..
