chromosphere

I have been thinking again about finally getting my astronomy kit up and running again – so I’m looking into designs for observatories. There are many different types of observatory – domes, roll-off roof, roll-away building, etc, but due to the size of our garden, I think that a dome could be the most desirable option (it has the smallest footprint, has good shielding properties from wind and light, and it looks like a “proper” observatory . Of course, we have to consider what are the downsides: More expensive/harder to make, needs to be rotated every so often (or motorized), and it looks like an observatory rather than a common old garden shed!

Of course, I could buy a commercial product – The pulsar domes seem to be most affordable (ignoring the Exploradome – useless with a German Equatorial mount!), though the 7 foot version is a bit small for my liking – and the 9 foot version is over 3 grand… So, I have come up with some ideas on a DIY dome and they are listed below (in a psuedo-design brief).

Aim:

Building of a 9 foot diameter observatory dome.

Requirements:

• Fully weatherproof (water/wind proof) – including shutter seal and skirt to avoid water/snow ingress between dome and walls
• Rotates 360 degrees
• 2.5′ door opening (enough for a 14″ telescope?); door to open either by sliding back over roof of dome, or by two doors sliding sideways away from the opening.
• Door opening to extend 1.5′ beyond the zenith
• Ability to securely lock dome in place (no rotation) when not in use, and securely lock doors from outside.
• Mount dome (and associated circular runners) on a solid base (eg breeze blocks laid to circle with mortar)

Ideas:

• Suggestions: Use marine grade plywood to construct frame of dome, and then cover with a skin of weather proof material (eg masonite, painted & caulked and then sealed with multiple layers of urethane paint to weatherproof). Alternatively, a metal skin would be acceptable. (eg: http://www.pictorobservatory.ca/html/pictor.htm; http://www.geocities.com/va3ngc/Astronomy/Projects/ObsDome.html)
• Dome runners – angle iron rolled to circle, run on castors with horizontally mounted guide wheels to keep the ring in place on the runners: http://www.astro-sharp.com/dome_wheels_door.asp
• Dome shutter: – Possible design involving a sliding section which slides back over the dome: http://www.astro-sharp.com/dome_shutter.asp. Bottom portion of the shutter must be removable (rather than flap down as shown) to avoid being fouled by the garden fence when rotated.
• Dome shutter – Alternatively full length split shutters which open to either side of the dome slit.
• Investigate the possibility of incorporating a motor drive into the design of the observatory – this should be able to drive the dome in azimuth in both clockwise and anticockwise directions (motor drive not required at first, but allowing for the addition of the motor drive at a later stage would be very useful).

So the first ideas are pretty much there. The dome itself looks OK, the door/shutters looks tricky, and the motorization is something that I think I will have to look at later… Maybe time to start getting some costs for materials, making some drawings, etc. and possibly worth thinking about getting some prices for parts (eg – getting wooden arcs cut? angle iron track? getting someone to make the whole thing?!?)…

Start Slide Show with PicLens Lite

Brewed this one up on 16th December and used yeast recultured from the bottom of a couple of Brakspear Oxford Gold bottles.

Following on from the last brew, where I think I finally sorted the water treatment out properly, I treated 36L of water with 31ml of Brupaks CRS (alkalinity measured as 194mg/l), and added 10g of gypsum (CaSO4) and 5g of Epsom Salts (MgSO4) to really bump up the sulphates and calcium in the brew (looking for about 450ppm of sulphates to see if I can get a nice sulphur bite!).

2.7kg Maris Otter
100g Crystal 120L
50g Flaked Barley
20g Black Malt
250g Dark Brown Sugar (boil)

Mash 66C
OG 1034 (22L in FV)

Various goldings for hops:

30g EKGs (4.1%, 60min)
20g WGV (8.7%, 15min)
30g Styrian Goldings (1 min)

Gonna bottle it tonight – it’s down to about 1010-1008 (3.1-3.3%ABV) as far as I can see (the krausen came and went very quickly indeed – a day or two and it was mostly done – but at 1034 there’s not much there to chew through anyhow I suppose).

I’ll harvest the slurry from the fermenter too – this will be used with any luck in the new year – maybe something along the lines of a Bishop’s Finger and then in the third batch a nice traditional IPA, bitter, and hoppy with a reasonably high OG .

Start Slide Show with PicLens Lite

Today’s full moon happens to (almost) coincide with the the moon being its closest to Earth for 15 years (it was last closer on 8th March 1993). The BBC have an article, including:

Its orbit is elliptical, meaning it does not follow a circular but rather an oval path.

It is currently approaching the point where this oval orbit is nearest to the Earth.

Gotta love the generic term “oval”. From the latin word for egg (ovum), it’s a rather generic word for a squashed circle and is often used to describe an ellipse in common speech.

However, that’s where the “dumbing down” comes. The ellipse is a precise term used to describe the shape of an orbit (like that of the moon) – it is the bounded case of the conic section produced by the intersection of a plane and a cone. It has two foci, and can be described by a clear mathematical formula: (x/a)^2 + (y/b)^2 = 1.

So why use the rather inaccurate “oval”, especially since you’ve already used the words “ellipse” and “elliptical” earlier in the article? Where’s Kepler when you need him?

They’re at it again! Not content with “atoms of light“, now we have a report on the moon-venus-jupiter conjunction on 1st Dec:

At the same time, the crescent Moon will eclipse Venus and, if you watch the Moon at sunset through binoculars, you will see an occultation of Venus by the Moon.

What? It’s not an eclipse! It’s an occulation! How can you manage to refer to the same event twice in the same sentence, make them appear like separate events, and then get the event description wrong one time out of the two?!?!?!!?

Friday night – time to get a brew on for Christmas drinking – this will be kegged and tapped for the festive season (and hence a nice drinking bitter – the Imperial Stout will wait for next year ).

3.7kg Maris Otter
165g Crystal Malt 120L

Mash 90min at 66C. Water: 40L liquor treated with 36ml CRS, 4g gypsum, 9.5g CaCl.

Hops:
Target (9%) 16g (90min)
WGV (8.7%) 8g (90min)
Styrian Goldings Bobek (3.7%) 4g (90min)
Styrian Goldings Bobek 9g (15min)

~29IBU

Dry hop in barrel with 2g Styrian Goldings

Yeast: Hopback

Read the rest of this entry »

Start Slide Show with PicLens Lite