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LittleTime Observatory

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#1 herschelobjects

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Posted 12 April 2018 - 04:07 PM

Observatories on small footprints (i.e. 100 square feet or less), whether roll-off or dome, are typically designed for small telescopes (ex: short focal length refractors under 6-inches or SCTs 10-inches or smaller). The observer with a medium or large aperture reflector (12-inches and larger) typically has to go with a larger building to deal with the reflector’s large “sweep” radius, thereby increasing costs, and, if located within a typical community, subject to building code regulations.

 

To avoid these issues, I chose to house my 22" f/3.3 reflector in an observatory I call a Split A-frame which was built on a 10'x10' platform. I am not the originator of this style of observatory. The first (and only) example of this type of construction that I have seen was built by Greg Mort about 30 years ago to house a large, pier-mounted refractor. Photos of the observatory can be seen on pages 22-23 of John Hicks’ “Building a Roll-Off Roof or Dome Observatory” and an article with photos describing the observatory was originally published in the March 1990 issue of Sky & Telescope, pp. 329-331. Though we followed the design very closely, a few improvements were incorporated to make the observatory more functional and easy to use. Because I have little or no talent when it comes to building things (and, in any case, do not have the tools available to do a proper job), I hired an experienced local carpenter to execute the build.

 

Two rows of cement footings, five on each side and three feet deep, were poured. Each row was twenty feet long, separated by ten feet. The footings support two twenty-foot fence posts, 6"x6" in size and laid flat on the footings. Aluminum 1/8" plate strips were attached to the upper surface of the posts to provide a smooth, low resistance rolling surface for the observatory halves (see photos with this post). The 10'x10' floor uses 2x6s in a standard frame construction, overlaid by 3/4" plywood. On the north side of the floor, 500 pounds of cement was poured in a 30"x30" frame to support the telescope.

 

The roof slopes at a 60° angle. Each half of the observatory uses 2x4s in a simple frame construction, overlaid with 1/2" plywood sheets. Roofing underlay was then applied, followed by standard asphalt shingles to complete the “roof” portion. For the walls, 1/2" plywood sheets were overlaid with standard issue white vinyl siding. The observatory halves rest on standard in-line casters. There are three casters under each wall, 12 casters in all. Ratchet straps (four in all) are attached to the interior of the building... these serve to secure both halves of the building when closed and also serve to bring the halves together to perform a secure and tight seal. Standard hooks and eyebolts secure the rolling halves to the observatory floor when closed. A sub-sized door provides access to the observatory when closed.

 

The high walls (7'2" on the west side, 8'5" on the east side) provide good wind protection as well as blocking illumination from local street lights. Though the walls obstruct the sky somewhat to the east and west, as I am a deep sky observer, I typically do 99% of my observing within a couple of hours of right ascension either east or west of the meridian, so any object will eventually make it into this observing window. When opened, the observatory has an “airy” feel with very good sky access and none of the claustrophobic feel of the typical, high-walled roll-off or domed observatory. Movement around the telescope is very free and even if several observing companions are invited over, there is room for everybody and easy access to the platform and telescope.

 

I am following this initial post with a series of posts illustrating the build for those who are interested.

 

Overall I am very pleased with the results... the design would allow, I think, for a 24" f/3 reflector to be housed, although I think this would be a tight fit. Naturally, this observatory could be scaled up to accommodate larger telescopes but this would begin to make the walls difficult to open and close by hand.

 

 

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#2 herschelobjects

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Posted 12 April 2018 - 04:13 PM

Concrete footings poured and in the next image the 6"x6" treated wood posts laid over the footings.

 

 

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#3 herschelobjects

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Posted 12 April 2018 - 04:16 PM

The framing for the floor, using 2"x6" planks. Note opening middle left where concrete footing for the telescope will be poured.

 

 

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#4 herschelobjects

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Posted 12 April 2018 - 04:18 PM

Plywood floor over frame...

 

 

 

 

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  • Ob6.jpg
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#5 herschelobjects

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Posted 12 April 2018 - 04:20 PM

500 pounds of concrete was poured into the opening to provide rock solid support for the telescope.

 

 

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  • Ob8.jpg


#6 herschelobjects

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Posted 12 April 2018 - 04:25 PM

Standard casters (three on each wall) were used to facilitate rolling the observatory halves apart. 4"x6" posts (seen perpendicular to the 6"x6" posts) provide support for the walls and roof of the observatory.

 

 

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#7 herschelobjects

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Posted 12 April 2018 - 04:28 PM

The cap for the observatory with pre-cut ribs to match the slope of the roof. Second photo shows cap in position.

 

 

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#8 herschelobjects

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Posted 12 April 2018 - 04:32 PM

Ron Weigel (my carpenter) posing with the roof and wall framing under construction. Everything here uses 2"x4"s. Note the wood spacers between casters... Ron was adamant that no critters (or moisture) would get into the observatory.

 

 

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#9 herschelobjects

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Posted 12 April 2018 - 04:35 PM

The half inch plywood underlay going on (first photo) and completed (second photo).

 

 

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  • Ob14.jpg
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#10 herschelobjects

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Posted 12 April 2018 - 04:37 PM

Roofing underlay going on, then shingles...

 

 

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#11 herschelobjects

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Posted 12 April 2018 - 04:39 PM

Close up of grooved opening which guides the halves of the observatory along the track when it is opened or closed.

 

 

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  • Ob18.jpg


#12 herschelobjects

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Posted 12 April 2018 - 04:42 PM

Siding going on...

 

 

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  • Ob19.jpg


#13 herschelobjects

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Posted 12 April 2018 - 04:44 PM

Ron bevelling the floors so that the halves can slide off and onto the floors.

 

 

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  • Ob20.jpg


#14 herschelobjects

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Posted 12 April 2018 - 04:50 PM

The completed observatory. Because there are no windows or vents, it can get very hot in the observatory during the summer months. But just leaving the halves separated by 6 inches or so provides plenty of ventilation to keep the observatory within a few degrees of outside temperature. For those in hot climates, a small A/C unit can provide cooling.

 

 

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  • Ob22.jpg

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#15 herschelobjects

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Posted 12 April 2018 - 04:55 PM

The small door provides access to the observatory when it is closed up. But opening the observatory fully makes it easy to bring in chairs, tables, anything really, to facilitate observing. And it is easy to swap telescopes in and out. Photo one shows me with my SpicaEyes Slipstream telescope (which is the main observatory scope), picture two shows my 18" LITEBOX dob travel scope.

 

 

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  • Ob21.jpg
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#16 herschelobjects

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Posted 12 April 2018 - 05:27 PM

No observatory is perfect and in retrospect improvements can be made. One issue is the possibility of water infiltration along the roof line. Ron made everything as tight as possible but even in light rain showers I found water seeping in. To solve this I used a “V”-shaped piece of vinyl moulding slipped under the shingles on the east (right side) roof line and stapled in position. This acts as an eavestrough, catching rain dripping off the roof and directing water to the ground on the north and south side of the building. You can see this piece of moulding at the roof line in post #14.

 

If I could do it again, I might consider using V-groove steel casters with inverted angles welded to the aluminum plate. This would provide better gliding of the observatory halves along the track. Additionnally I would consider mounting the casters on the left side wall on springs which would allow me to push down on the observatory frame, breaking contact with the roof at the top and allowing the observatory halves to slide apart more easily. Currently, it takes about a minute or two to open the observatory and about five minutes or so at the end of a session to slide the observatory halves back together.

 

It is important to note that, in mid-northern climes, this is a three-season observatory. I live on the prairies and our winters are cold, harsh and sometimes snowy. The tracks that the observatory runs on will get icy and snowy in the winter. Since I don’t observe in frigid conditions, this was never a concern, but if you live in a cold and snowy climate and want to observe in the winter, this design will probably not work for you. The photo below shows the observatory on a cold day after a snowfall. I cover the exposed rails with tarps which keep snow and moisture off in the winter. If you’re down south and get little or no snow, this style observatory can be used year-round.

 

All in all, I’m super pleased with the results. There is ZERO snow or rain infiltration in the observatory and no critters can get in. After twenty months I did notice a small spider’s web in the rafters with a couple of bugs trapped in the web. Whaddaya gonna do?

 

 

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  • snowyday.jpg

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#17 mikerepp

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Posted 13 April 2018 - 06:57 AM

Clever design, I like it!  Have you thought about attic vents to keep it cool rather than leaving it slightly open to cool.  They have solar powered vents that could be used to cool it down rather than a passive vent system.


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#18 herschelobjects

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Posted 13 April 2018 - 07:37 AM

Hey Mike, no I have not heard of this. There is really not very much room near the roof in this design to allow for vents... they would have to be quite small. Heat build-up during the day is only a concern in June July and August where I live and only when temperatures get beyond 80°F. I usually only crack it open on days when I know I’ll be observing in the evening; opening the observatory fully late in the evening cools everything down pretty quickly.



#19 roscoe

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Posted 13 April 2018 - 07:41 AM

That is a grand idea!!  Well done!!

 

Only thing I'd change - or suggest to others, would be to keep the whole thing a couple inches in the air, so as to help keep the floor framing from absorbing ground moisture.....and/or use PT plywood for the decking....


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#20 herschelobjects

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Posted 13 April 2018 - 12:25 PM

That is a grand idea!!  Well done!!

 

Only thing I'd change - or suggest to others, would be to keep the whole thing a couple inches in the air, so as to help keep the floor framing from absorbing ground moisture.....and/or use PT plywood for the decking....

Thanks, Roscoe! The 6x6 and 4x6 posts are pressure treated, the rest of the lumber is not. Water seal was painted on the surface of the plywood floor and on exposed exterior wood at ground level which should provide some protection. Although we have wet spells where I live, we also have extended arid periods and humidity is usually lower than what would be experienced back east. Also, there is not a tight seal between the ground (which is uneven) and the base of the observatory, so there is at least a little “breathing” under the floor, so ground moisture is not necessarily trapped under the building. But you make a couple of very good points.


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#21 ScottW

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Posted 14 April 2018 - 03:45 PM

Really nice job!

It just so happens that I've been working on the same concept the last week or so.

I remember the 2009 article and did some sketches in 2011, they look just like you finished project.  

This week I changed the design somewhat. I'm making it just around 4' tall and hinging the halves instead of sliding them out of the way.  This is of course for storage of my scope but with the added advantage of unfolding into a dry 8' by 8' platform.  This I hope to do by cutting the outer corners  of the triangle 2' from the center so that there is 2' along the edge that will meet the ground.  This might might not be real clear but I'm not good enough at this computer stuff to attach a sketch, sorry.

 

Enjoy it,

Scott


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#22 herschelobjects

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Posted 14 April 2018 - 06:22 PM

Thanks, Scott! Best of luck with your project.



#23 Marc-Andre

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Posted 06 July 2020 - 10:14 PM

Congratulations on being featured in the August 2020 issue of Sky and Telescope magazine! (p 69)  It was that article that led me here for more information on your construction.  Your design is nice, and Ron did a good job!  




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