Need Some Guidance on Siting an Observatory

[russellhq]

I'm would like to build an observatory in the garden to house the telescope so I can keep it set up outside (and also keep it out the house), but I'm surrounded by streetlights and I'm not sure the best way of dealing with them would be.

My options are ROR style, which is nice and simple. Or a dome to keep stray light away. I was pretty fixed on going down the simple route, but with the number of street lights to contend with, I'm thinking a dome may be the more worthwhile investment. The scope runs on a mini PC that I remote desktop into and control from my house, so the observatory only needs to be big enough to house the scope, I won't be getting in it. Hopefully that would keep costs down.

To give you an idea of the challenge, below is a satellite view of my house showing where I would site the observatory and where the local street lights are (there are a few).

PLAN

This is also a shot from StreetView looking west towards my house:

Any ideas or advice on dealing with the stray light would be greatly appreciated. 

[Astrokev]

Most of the lights appear to be due South, which is not ideal. The one just outside your boundary is a killer ?

Regarding type of obsy, a dome may be better for the reasons you state. Another consideration though is that a dome may advertise the contents more than a ROR, possibly inviting unwanted guests. A ROR would like more like a standard shed and be less conspicuous. Perhaps you could make a ROR but with some form of simple shuttering that you could erect when needed (eg. black cloth draped between posts in each corner?).

Not an easy one and I'll be interested in how you decide to go with this. Good luck.

[russellhq]

Thanks Astrokev, I had thought about the cloth between posts idea (kinda like a wind breaker for the beach).

The one just outside the boundary is a real pain, though the photo below shows that there is a large tree behind it, so that section of the sky is out of bounds anyway.

 

I think i could make up a screen to block them, but it's deciding what high to set it at has me scratching my head.

[Charic]

I screened my street lights, specifically to protect my eyes, but noticed that the light was still  being reflected of the buildings themselves, so gave up  screening, but haven't stopped considering other options?
I also use a utility tent, but it needs several layers to get fully dark, and I cant use the finder scope once snuggled inside, only the focuser, as only the very end of the scope sticks out, with my  DIY foam extension snood  added to further help baffle any stray light.
There's still street light about, but my eyes are better dark adapted inside my pitch black tent during the winter months. It feels better, but still a lot of faffing about to get dark-dark inside the tent. My other disadvantage is my limited sky here, literally straight up to Polaris.

Nothing beats getting away from industrial light sources, and finding a truly dark and safe site to observe from.
 

[russellhq]

Thanks Charic, I won't be observing from the garden, only imaging. So I'm trying to keep the streetlights from shining directly onto the telescope.

I'd found this material before which looks like it could be a good contender for building screens out of:

https://www.growell.co.uk/grow-tents-sheeting/reflective-sheeting/reflex-total-blackout-reflective-sheeting.html?nosto=nosto-page-product1

 

[Charic]

How much light gets through your hedge? keeping your setup low may help.
I have a Tree to my North which when fully leafed does help somewhat to shield the carpark light, but  just keeping inside the shadows is better than nothing.

I know its important to keep the eyes dark adapted, and thinking that the camera for imaging  collects more light overtime, I'd expect the images to be overexposed, but I'm not an astrophotographer just yet, not something I have tried, but hopefully there's a solution.

Then I see your location, now there's no chance ( only kidding ). The last trip I made to the Planetarium shows how Glasgow could look if all the lights went out? what a difference.

How are your present images from said garden, if only a little shielding works, then a proper observatory may be essential, or at least more permanent.

[DaveS]

What are the planning regs in Scotland like?

I know that in England if you wanted to put a building there you'd have to get planning consent, because it's in front of the property lines, bit of a pain in a corner plot as *everywhere* is in front.

[russellhq]

1 minute ago, DaveS said:

What are the planning regs in Scotland like?

I know that in England if you wanted to put a building there you'd have to get planning consent, because it's in front of the property lines, bit of a pain in a corner plot as *everywhere* is in front.

Thanks Dave, but from looking around at what the neighbours have in their gardens (and extensions to their houses) it seems to be a free for all! Pretty sure it would fall inside permitted development whatever I go with.

[DaveS]

OK, but I'd be reluctant to take *anything* for granted where planning is concerned, you don't want to have to knock it all down again, *and* get done for a fine.

[Adam J]

23 hours ago, DaveS said:

What are the planning regs in Scotland like?

I know that in England if you wanted to put a building there you'd have to get planning consent, because it's in front of the property lines, bit of a pain in a corner plot as *everywhere* is in front.

You would hope that the front is the aspect to the front of the property, or more likely the street to which the address of the dwelling is attached...if the door is on the side then it may be more of an issue, but I find if hard to believe that planning would be so restrictive, people on corner plots need sheds etc like everyone else.

Do you already take images / observe from the garden on a mobile mount? If so how badly does the light from the street lights currently effect your imaging / observing? Do you get bad gradients etc. 

It really is that one closest to you which will be the killer especially after they convert it to LED, It will happen soon so you have to plan as if its already happened. For all the benefits of LED (directional and dimable and often turned off after a set hour)  I would want to be within direct line of sight of one even less than a high pressure sodium or low pressure sodium light as you cant filter them.  If they are not in direct line of sight then LED can actually improve things a little. 

In placing my obsy I put it in a location in my garden where all the lights are blocked by buildings I did this even at the expense of poorer views to the south. 

My recommendation is:

1) Call the council and:

                                 a) Ask when the lighting will be upgraded to LED. If its in the near future then wait out and see how it effects things, you dont want to make choices based on the current lighting and find them to have been incorrect when they change the lights the day you finish the obsy. 

                                 b) Ask if its possible to have the light shielded (they can place a screen on the rear of the light that prevents it from shining in a given direction, some councils will be willing to help you out with this, some will not) frame it in respect to the impact on your garden and house as oppose to just the observatory.  

 

2) I don't really like the idea of the screen in the garden, its not a very elegant solution in my opinion as such a structure could not be fixed permanently, it would be an eye sore and catch the wind too badly every time there is a storm. My solution would be to plant a tree (or two) in that corner close to the nearest light something fast growing and ever green (blocks all year round) directly behind the light. Keep it trimmed to a height just above the light as you do not want to annoy neighbors with a 60ft Leylandi. In addition in this case I would also chose a dome...too many other lights (although no so big an issue) in the area blocking all that stray off axis light will help you no end. 

3) As I am sure you are aware narrow band is your friend and so you may just have to accept that your not going to be doing any award winning broad band imaging from your location. Focus effort on what you can do well from your location and try not to worry about the rest. 

Hope that helps 

 

Adam 

 

[DaveS]

I found this on the Scottish .gov website regarding permitted areas.

Planning Areas.pdf

Hope it's of use.

Edit: link didn't work, Hope the PDF will.

[DaveS]

Looking at your Google Maps and Street View, I think the area "behind" the house will be OK.

[JamesF]

I find myself wondering if careful placement of the obsy on the other side of the house (roughly where the shadow of the house meets the northern boundary, say) might allow it to block most of the street lights from direct view, and allow the house to be used to mount a shield for at least one of the remaining visible ones.  Of course you do then risk the house obstructing some of the views you're after.  It's never easy

James

[russellhq]

Thanks James, but what's hard to see, is that there is a large tree (as well as street light) to the north and a really bright street light to the south which would be difficult to deal with. Also the 'front' garden is much less private compared to the 'rear'.

 

Looking south, the very bright street light

 

 

Looking North - large tree and street light

 

This is the head of the very bright street light

[russellhq]

I took some panoramas while standing in the spot I'm thinking of siting the pier.

This is NNW to SSE

And this is SSE to NNW

 

So you can see most of the street lights are below the roof line of the house and another has a large tree behind it. So if i could shield the scope from these then I don't think I'd loose much, if any sky.

[russellhq]

What I really want to figure out is how high above the top of the scope (when pointing at the zenith) show I make the walls, and how far from the scope should they be so I don't block the scope when point nearer the horizon. Hopefully this crude sketch explains what I mean.

[JamesF]

The easiest way to work that out might be to knock a couple of stakes into the ground with the first being where your telescope will be and with the top of the post at the same height as the highest position your OTA can reach.  The second goes a few metres away on the line between the first and the lamp post, with its top on a line from the top of the first post to the actual light (so if you sight along the tops of the two stakes they line up with the lamp fitting.  (Or knock in a couple of stakes along the right line and then screw a cross-piece on at the correct heights.)

You can then put a line over the top of the stakes and measure off the absolute minimum height of the wall at any given distance from the telescope.  I'd probably add a few inches just to make sure the light was blocked because taking the highest point your OTA will reach isn't necessarily a perfect choice.

If you can measure the angle to the lamp fitting from the top of the OTA you could just do the calculation mathematically.

James

[russellhq]

Thanks James. I engaged my brain for a bit today and had a play around with the mount, slewing the telescope in all different directions to get an idea of what's happening. It seems that the telescope's heights point is when it's pointing at the NCP and it's at it's lowest when pointing south at the horizon. So I sketched out a couple of scenarios. These were based on the assumption that I would need to block the from the horizon to 10 degrees to be able to shield most of the offending stray light. So the first scenario is with the scope pointing at the NCP and an observatory 1.4m x 1.4m. In this scenario the wall of the observatory would have to be at least 821mm above the pier top. The second scenario was based on the same assumptions as the first and with the same wall height but with the scope pointing south. In this scenario the scope would only be able to image down to about 40 degrees above the horizon before the observatory walls blocked it's view.

 

I don't like the idea of limiting my viewing horizon to 40 degrees above the horizon, so I'll need to rethink this a bit. I reckon I'll have to go with some kind of board that's attached to the walls inside the observatory and is on some kind of sliding rail which, once the roof is off I can slide up to whatever height I need.

Something like this:

This way I can 'raise' and 'lower' the height of the observatory walls once the roof is off.

[Gina]

Clever ?

[JamesF]

You want a roller blind that works upside down ?

A blind mechanism is almost too complex, actually.  I have an idea in my head that's something I've seen somewhere (the other way up), but I can't recall where.  Basically a sprung roller so the "blind" remains under tension, with a scissor action mechanism (like a scissor lift) to raise the blind to the required height.

Actually I imagine the tricky bit is making it sufficiently rigid to cope with the occasional gust of wind.

I'm sure it must be possible to create a mechanism that would lift a wall extension or some sort of blind with adequate support without compromising views by being any higher than the actually extension and provides it with the required resistance to wind.  I have an idea in my head that I can't quite focus on at the moment.  Sort of like a combination of the scissor mechanism and an old-fashioned deck chair.  I'll post again if I can get my head around the idea.

James

[Astrokev]

4 minutes ago, JamesF said:

You want a roller blind that works upside down ?

A blind mechanism is almost too complex, actually.  I have an idea in my head that's something I've seen somewhere (the other way up), but I can't recall where.  Basically a sprung roller so the "blind" remains under tension, with a scissor action mechanism (like a scissor lift) to raise the blind to the required height.

Actually I imagine the tricky bit is making it sufficiently rigid to cope with the occasional gust of wind.

I'm sure it must be possible to create a mechanism that would lift a wall extension or some sort of blind with adequate support without compromising views by being any higher than the actually extension and provides it with the required resistance to wind.  I have an idea in my head that I can't quite focus on at the moment.  Sort of like a combination of the scissor mechanism and an old-fashioned deck chair.  I'll post again if I can get my head around the idea.

James

Intrigued, and sounds interesting ?

[JamesF]

No, I'm over-complicating it.  How about a mechanism like some extending tables have?  Two bolts poking out of the wall horizontally into the observatory at the top, two a little further down, vertically beneath the first two.  The "wall extension" has a vertical slot either side that fits over the shanks of the bolts.  On the ends of the bolts you have a large washer and wingnut or other "easily undoable" nut.

To deploy the extension you just release the wingnuts, lift the extension to the required height and do them up again.  At the end of the night it's the reverse process.

Does that make sense?

James

[russellhq]

Thanks James. I was thinking of using something like slotted shelving rails where instead of shelves it would be a screen.

Something like this. So the screen would have the hooks in the back of it and I could just clip it into the position I wanted.

[Gina]

Nah!  A piece of plywood in guide rollers and string attached to the bottom then up over a pulley to pull it up.  I'll make you a diagram if you like.  But tomorrow - I'm off to bed shortly as I've had a busy and tiring day.

[Astrokev]

Interested in this discussion as I have an horrendous decorative lantern in next doors drive just at the back of my obsy. My neighbour has kindly agreed to "blank out" the side facing my garden, but I'm worried there'll still be some stray light finding it's way into my OTA!