A HOME-MADE OBSERVING TABLE

Ian Ogilvie

Background

I decided to build this observing box/table several years ago after getting tired of dew-soaked charts on a dew coated card table and tripping over, or not being able to find the eyepiece box. This is not an original idea. I happened across a description and photo of an observing table in Dave Gault's web site; http://www4.tpgi.com.au/users/daveg/. I thought his design looked really practical and with some modification would suit my purposes. I took note of Dave's comments on his design and adapted the design for my requirements.
I had never attempted to build an item like this before so I was not totally confident of the outcome.
When I commenced planning this project I listed the following requirements for the observing box:

1. Must fit on top of the card table I was currently using.
2. Must fit in the back of a medium sized station wagon along with all the rest of the telescope paraphernalia.
3. Must keep dew off charts and equipment when in the open position.
4. Must have dimmable red lighting.
5. Must hold observing log, Hartung, Ellyard and SA2000 Companion reference books.
6. Must hold SA2000 Star Atlas and provide a dew protected surface for chart reading.
7. Must hold 6 x 1.25" eyepieces, small tool kit, torch, filters etc.

My general concept was that I would have to remember to pick up only 5 items to pack the car for a deep sky night: telescope tube, telescope base, card table, observing box and chair. The observing box was fun to build and has worked well. However, I still seem to have to pack the car with 20+ items each time I travel to a deep sky night.

Description
The overall dimensions were determined by the size and orientation of the star atlas I was using at the time: Sky Atlas 2000.0 field edition, and the eyepiece and tool stowage requirements. I calculated these dimensions would allow me to fit a small reference library into the lid with room to spare.

The closed dimensions of the observing box are:
Width 700mm
Depth 450mm
Height 140mm

Design
The observing box is quite simply a ply wood box with a hinged lid. The base and the lid have identical external dimensions and the lid stays hold the lid open at an angle so the lid overhangs the base and provide some dew and wind protection.

Hardware used for this project:

- Suitable quantities of plywood and dressed pine.
- 1 piano hinge
- 2 case latches
- 1 handle
- 2 lid stays (the ones I used were card table leg stays)
- 8 corner protectors
- Elastic straps to hold books in place
- 4 small hinges for equipment compartment lids
- 1 latch for eyepiece compartment lid

The observing box was fabricated out of 6mm plywood for the top, bottom and compartment lids, and 10 mm dressed pine for the sides and internal compartments. I also used 3 mm plywood for the small raised step around the top of the base for the lid to close onto. I am sure this feature has a name in the cabinet making world. I selected these materials as I already had them on hand and appeared to be of suitable dimensions for the task.
I first constructed the base and lid as identical units and then added the small raised step into the base and the main hinge. Next step was library compartments in the lid. It was at this point I realised I could probably use a bumper on the RH library compartment to keep the rear equipment compartment lid closed.
The photo below shows the bumper above the opened rear equipment compartment lid. When the observing box is closed this bumper pushes lightly against the lid and keeps it closed.
The box was designed to hold the following items of equipment:

Base:
6 x 1.25" eyepieces.
Prism.
Lens pen.
Small red torch.
Small kit of tools in see-through pencil case.
UHC and CLS 1.25" filters
Illuminated magnifier
Observing log
SA2000 Star Atlas

Lid
Hartung.
Ellyard.
SA2000 Companion
SA2000 transparent overlays.
Ephemeris.
Reading glasses.
Leatherman tool.
Red LED's and battery pack.

In the field it works just as intended. The open lid keeps the dew off the charts, all the equipment is on hand and due to the dim red LED's you can find what you want without fumbling for a torch. You do however have to use additional red light in order to read charts.

Modifications
In use the unit was placed on top of a card table as intended. However I subsequently modified a wooden folding chair frame to provide a more compact and stable set of legs. At this point, as it was no longer a box sitting on a table, it became an observing table in its own right.
As I have acquired more equipment there has been a tendency to fit more items into the box with the resultant weight increase. After I finally noticed this "middle-aged spread" I acquired a canvas tool bag and banished some items from the observing table as listed below.

Cheshire collimation tool.
Secondary collimation hex key.
Insect repellent.
Spare AA batteries.
Several 2" eyepieces.
Red torch X 2

In the field
The observing table has been great to use in the field. I find I don't use the library every time, but it is nice to have the books there when you need them. I consider the table size/weight to be on the upper limit for easy stowage in, and removal from, a medium sized station wagon. Due to weight issues one needs to watch for any tendency to add additional bits and pieces. The dew and wind protection provided by the angled lid has worked just fine. I have also found the red lights have greatly simplified changing eyepieces, adding filters etc.

I have noticed as the evening progresses and different eyepieces are used, I tend to just leave them loose in the chart area. This is probably an indication that the eyepiece compartment, while working really well for stowage and transport functions needs rethinking. I suspect it also indicates a tendency towards laziness on my part.
Initially I placed the observing table on top of a card table for use in the field. I found it a real pain to carry both the card table and observing table in the car. Fortuitously the cloth seat on one of our folding chairs gave way and this was an opportunity to make a set of folding legs for the observing table that would take up less room and be more stable than the card table. The absence of the unused area of the card table does however lead one into an unfortunate tendency to leave partly consumed cups of coffee in the chart area of the observing table, with the obvious results.

Summary

Liked
- Cost
- Reasonably light.
- It can hold most of what is needed during an observing session.
- Worked as planned with minimal mods required.
- Fun to build.

Not Liked
- Wrong size for the HB Astro Atlas.
- Cannot handle stowage of larger 2" eyepieces.
- Needs separate legs.

Knowing what I know now, would I make the same decision again?

Yes I would (and I will) build another observing table. However, I will change the design by simplifying the stowage requirements to allow for more room for chart use and incorporate folding legs into the design. I will also change the dimensions to accommodate either SA2000 or HB Astro Atlas.
It also needs a fold out cup holder incorporated into the design.

Overall
This observing table has worked well for several years and regular use has given me inspiration for an improved design.

Acknowledgment
I must thank Dave Gault for publishing the details of his observing table on the web, thereby providing me with the inspiration to build a similar unit.

CONSTELLATIONS OF THE MONTH - CAPRICORNUS

Albert Brakel

Capricornus is, of course, the zodiac constellation of the (Horned) Goat. Since ancient times, and probably since before recorded history, it has been represented with a fish's tail, and often called the Sea-Goat (in which case it should really have been called Caprimarinus). Why it was made a composite creature instead of a normal goat is now unclear (though some stories were invented after the fact), but it may have had something to do with it being a wet time of year in Mesopotamia when Capricorn was around, as there are also several other water constellations in the region (Aquarius, Pisces, Piscis Austrinus, Cetus, and Eridanus). According to one report from a Babylonian source, the world will be destroyed by a great conflagration when all the planets meet in this sign! (Please don't tell the prophets of doom, and remember that the people who believed this also believed that the world was flat).

For those who have no interest in double stars, the only object of note is the globular cluster M30. But before you start with the deep sky objects, look in on Neptune, visiting Capricorn at the moment and located directly between Theta (?) and 29 Capricorni, just over a degree NE of Theta. The planet was discovered in 1846 just across the border in Aquarius, and is slowly but inexorably closing in on that position again, to return there in 2011 after completing its first orbit around the Sun since discovery.

The following observations were made with a 20-cm SCT from my increasingly light-polluted back yard in Downer.

Let's start with the best: the fine globular cluster M30 (21h 40.4m, -23º 11'), in SE Capricornus. Its moderate size (11' diameter) and integrated magnitude of 7.5 allowed it to be barely visible through a 6x finderscope, but only after I knew exactly where it was. With 117x power and averted vision, the outer edges were just resolved, but the core remained solid-looking. Higher powers did not help much. Two short rays of stars could be seen on the NW side.

While in this vicinity, go 25' to the ESE (in the same low-power field) and check out the double star 41 Capricorni (21h 42.0m, -23º 16'). The primary component blazes away at mag. 5.3, while the secondary is a diminutive mag. 11.5, 5.5" away at position angle 205º. Obviously this is not an easy one, and will be a test of the seeing conditions.

6 deg. to the SW lies Burnham 271 (21h 19.8m, -26º 20'), a deep yellow binary with a 2.2" separation but with a big magnitude difference (6.6 and 9.7). In the less than perfect conditions I suspected a split, but wasn't sure.

Alpha (?) Capricorni (20h 18.1m, -12º 33') in the NW corner of the constellation is a well-known golden-yellow optical double that can be resolved with the unaided eye. The two stars are not physically connected and just happen to lie near the same line of sight, but each itself has true companions. The less bright Alpha-1 (mag. 4.2) has a colorless mag. 9 partner 45.4" to the SW (Hartung says it is reddish). Alpha-2 (mag. 3.6) has a faint companion 6.6" to the S that is itself a close (1.2") pair with mags. 11.0 and 11.3 - I was unable to split the latter even with 235x.

The remaining doubles are also located in this corner of Capricornus, SSE of Alpha. Beta (?) Cap (20h 21.0m, -14º 47') is so easy it can be split even with a 6x finderscope. The bright mag. 3.1 primary is deep yellow. Lying a very wide 205" to the W, the whitish m. 6.2 secondary appeared pale greenish-blue by color contrast, and after using a red-light torch it became light green. This goes to show how a red light or a strongly colored bright star can affect your color perception.

Pi (?) Cap (20h 27.3m, -18º 13') is a whitish, unequal (m. 5.2 and 8.3) pair separated by 3.4". It was just resolved with 77x, but was of course better with higher magnifications.

Straw-colored Rho (?) Cap (20h 28.9m, 17º 49") with very unequal mags. 5.0 and 10.0 at just 1.3" separation is a tough one, best left for good viewing conditions. The orbit is very eccentric, and the PA passed through more than 270º around closest approach of 0.1" in 1964. The stars will now continue to slowly move apart.

To wind up with a good one for a small scope, Omicron (?) Cap (20h 29.9m -18º 35') is a very easy white pair that was widely separated using 50x power. Mags. 5.9 and 6.7, lying at 18.9" SW.

If it's galaxies you're after, then frankly Capricorn is not the place for you unless you're really keen - all its galaxies are faint and difficult, and there are better pickings elsewhere. But if you really must try one, then have a go at the brightest, NGC 6907 (20h 25.1m, -24º 49'). This is a mag. 11.3 barred spiral 3.4' x 3.0' across, and in larger scopes is said to look like a roundish halo of grey light rising to a brighter oval-shaped middle.