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?!?)…

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?

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?!?!?!!?

Saw this circumzenithal arc on Friday 15th from Abingdon. Looks much like an upside down rainbow above the sun (which needs to be lower than 33 degrees or so for this to occur) – it occurs due to horizontally orientated ice crystals high in the upper atmosphere.

Only had the camera on my phone so the image is a bit ropey, but hopefully clear enough…

I had lots of trouble with this image (taken on 6th Feb, 2007) – the flats I took didn’t work out (there’s the odd artifact here and there!), and I’m not quite happy with the colour balance – have another go at this later I think…

At 100% scale, the detail in the Rosette Nebula (showing the dark regions obscuring the bright emission nebula in the background) shows the effects of the stellar winds from the hot stars of cluster NGC 2244 (top right). This is a crop from the full size image above.

More recently, on the 21st February, 2008, another lunar eclipse was visible from the UK and Europe early in the morning. However, the weather for this event was not as favourable with cloudy conditions across much of the UK (despite having a long period of clear weather in the preceding week!).

There will not be another lunar eclipse visible from the UK in its entirity until 2015 (though two will be partially visible with the eclipsed moon setting on Dec 21st 2010, and the eclipsed moon rising on June 15th 2011).

Here are some of the best images from the eclipse (if you view the gallery, make sure the post has the full width of the page to see it all – clicking the expand button or viewing the individual post):

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The h-alpha filter works by using an etalon to restrict the wavelengths of light as viewed through the telescope down to only a small region of the spectrum around 656.3nm (typically with a bandwidth of <0.7Å), which is a principal emission wavelength of excited hydrogen atoms (for the transition n=3 to n=2 in the Balmer series). This allows features such as prominences, flares, filaments and active regions to be observed, whereas in white light these are often not as noticable or are invisible.

My images were taken using either a Toucam Pro II webcam (for the closeups), or using the SBIG ST2000XM coupled with a Denkmeier Part O/Cell #150 relay lens combination to give the system enough backfocus to bring the camera to focus on the Takahashi FC60NZ. Note, for those of you with an SBIG camera taking very short images (milliseconds), you’ll want to check out SBIG’s Article on Vertical Streaking (.pdf)- you need to adjust a potentiometer in the back of the camera to avoid this happening!

The following gallery is a collection of images taken using the Coronado filter – there are more images of the sun in h-alpha during the 2005 Annular Eclipse.

[Show as slideshow]

Of course, nothing goes smoothly:

1. CCD dessiccant had (long) expired and when bringing the chip of the CCD down to temperature (-25°C), ice formed all over the chip. Solution: Bake the dessiccant canister in the oven for 4 hours at 175°C and then reinsert and let it dry out – I’m still waiting for the dessiccant to do its thing – I may even have to bake it again tonight to get it dry.
2. Focuser issues – This is so far unresolved – think it’s gonna need fixing as I can’t connect to it.

However, all was not completely lost. I adjusted the RA worm clearance on the Titan (much less backlash, but still loose enough not to bind and fry the motor), and I installed a demo version of PemPro to look at the periodic error on the mount. This measured out as about +7/-5 arcsec uncorrected, and with a very quick run through, I was able to get it down to +/- 2 arcsec. This is an excellent piece of software, and one I think I will be buying in the future – not to mention its ability to help polar alignment, and backlash correction settings.