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This page gives a few morsels of information to enable visitors to place Ravenshead Observatory on the world map and what is needed to make astronomical imaging a practical proposition. To start with - for non-UK visitors to the site - this is the only map I could find quickly that places Nottinghamshire on the map of England.
Nottinghamshire
Due to the extremely poor and continually degenerating weather conditions and light pollution at the Ravenshead site I decided to re-locate my imaging system in November 2008. Now I have two observatories. One is in my back garden in the small town of Ravenshead, Nottinghamshire, England which currently has no imaging equipment installed on the telescopes and mount that you can see in the pictures below. The other is at the Sacramento Mountains Astronomy Park (SMAP), just south of Mayhill, New Mexico mounted on a new telescope and mount. The details of each observatory are set out below.
FIRST OBSERVATORY
- RAVENSHEAD
The observatory site is located 20 km North of the City of Nottingham, England
and it is 6 km South of the town of Mansfield. Ravenshead is near the left centre
of the green area shown on the map. The observatory is set in the back yard
of our property and is within the area that was once part of the great Sherwood
Forest. For avid film-goers, it is only partly true that the men around here
still wear tights - and these tend to be football players (soccer to US viewers) !! The village of Ravenshead
is quite rural but it is increasingly threatened with in-fill developments. As
a result there are fewer trees every year and there is a moderate but increasing
level of light pollution from all directions, but most heavy from SE - SW and
NE - NW. If I had been around in the 16th century the site would have looked
very different. This is Nottingham Castle at that time - I assume taken with
the very first Kodak Brownie CCD Camera (??). I would have put the observatory at
the top of the tower on the left of centre! Not much else around in those days..........
The area is very different now. At 20 km North of Nottingham Castle (which is now mainly re-built and restored) there have been many smaller towns developed - many of them grew to support the lace and mining industries until the late 20th century. At the site of Ravenshead Observatory now the least light pollution is through the directions NE to SE and the sky typically gives around magnitude 3.5-4.5 star visibility. Very occasionally the Milky Way is visible but with variable seeing (air stability). Due to nearby tree heights and the light pollution there is little opportunity to view the sky below 45° altitude and few images taken from this site have been taken when the target has passed the meridian (ie gone past South to the West).
As a concession to the semi-rural nature of the area around Ravenshead, I built this private observatory to simulate a garden summer house and to blend in with the garden setting - in other words I painted it green. The second view is taken from the South East, looking North West. The equipment in view is currently being used for visual observing and is described in the Equipment section of the web site. Since this site was created the mount has been replaced with a Paramount ME German equatorial mount with full robotic control capability.
The wall supporting the roof rail track of the observatory was built high to shield the telescope from local lights in the house and neighbouring property security lights. The instruments I use can all "see" from about 35° altitude to the zenith - enough to keep above the heaviest light pollution.
The telescope shown here is an Astro-Physics AP155 refractor ie 155mm diameter object glass or 6.1" in old money. The focal ratio is f/7. Whenever I want to change the field of view of my imaging sessions I can add a focal reducer to the AP155 which converts the focal ratio to f/5.3. The AP155 also has a Takahashi FSQ106N astrograph refractor mounted on its back. This has a 106mm object glass and has a focal ratio of f/5.0. This is used when I want to take very wide field images such as the Pleiades image in the FSQ106 Gallery page. The steel pillar supporting the telescope assembly is bolted down to a concrete base about 1 metre deep and 1.5 metres square. The base of the observatory itself is 3.1 x 2.6 metres. Mounted on the telescope (only just visible in this picture) is the digital imaging camera:- an 11 Megapixel Santa Barbara Instrument Group ST-11000M with an integrated ST-237H self-guider guider chip and an 8-position filter wheel for taking RGB colour and narrowband images. I also have the option to use a remote guide camera on the FSQ106 when imaging with the AP155. This set-up worked very well but the camera and filter system have now been re-lcated to New Mexico.
On top of the pier and the workhorse of the entire setup is shown an Astro-Physics 1200GTO electronic drive mount. This recently been replaced by a Paramount ME German equatorial mount. This mounting has been aligned to within 40 arc seconds of the true north celestial pole to allow precise tracking of most celestial objects. This has recently been replaced by a Paramount ME
In the observatory I use a laptop computer that controls all the aspects of astronomical imaging. This computer is in turn controlled by a computer from inside the house using an ethernet power socket link and RADMIN PC control software. In a normal nights imaging, the only reason to be at the observatory is to roll off the roof and to connect the laptop. Typically this would take 5 minutes. From that point image target finding, framing on the camera CCD, focusing and imaging sequences are all performed using Windows XP on the observatory PC but then RADMIN controlled by computer inside the house. To avoid laptop damage through damp and cold it is never left in the observatory when not in use.
SECOND OBSERVATORY - SMAP , WEED, NEW MEXICO
This site is a very dark site at an elevation of over 7,200 ft. It has been developed to support more than 100 individual amateur astronomer observatories, each with dedicated power and telecomms for internet control of the whole observatory. The site was purchased by two English amateur astronomers, Chris Traher and Phillip Stone - both of whom live in the UK. They have invested their own funds to make this facility available to amateurs anywhere in the world. In my own case, the roll-off roof observatory structure, the power, telecomms and insurance are all rolled into a single monthly rental sum. A resident on-site support astronomer provides the physical and technical support that is essential to installing and operating a remote observatory. Without this support and investment by the SMAP team I would not have been able to achieve my objectives and I am delighted to have been the first user of their astronomy park facility. The site and its location in the USA can be viewed at http://www.sacramentomountainastropark.com/ .
The equipment in the SMAP observatory is owned and operated by myself. This includes the UPS power supply, a weather monitoring device and a fairly powerful desktop PC. This PC has all the control programs to enable me to open and close the roof, monitor the local weather, switch the power on and off to any individual device in my telescope set-up and of course to operate and control the mount, telescope and cameras to facilitate digital imaging. The telescope that I installed is a 400 mm aperture f/8.26 Ritchey-Chretien supplied by Officina Stellare of Italy. The mount is a Software Bisque Paramount ME and the CCD camera I currently use is an SBIG ST-11000M (11 Mpixel monochrome) with a self guiding second CCD chip integrated into the optical path. The new dome that is in the process of being commissioned belongs to me.
After delivering
all the new equipment to site in November 2007, I returned to the site in February
2008 to install all the imaging systems and to build the controlling PC. The
PC was set up to operate as a RADMIN Server to enable me to use RADMIN Viewer
on my home PC in the UK to take full control of the observatory and all imaging
related functions. To avoid damage due to cold and damp this PC is only switched off when under maintenance. After numerous difficulties and a great deal of frustration,
the first light image was achieved in November 2008. The first light image is shown on the right below. The picture on the left below shows
the type of roll-off roof observatory that I use at SMAP as well as one of the
local inhabitants.
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After 19 months of imaging with the roll-off it became clear that I was losing around 60% of the clear nights available due to the wind speed alone. I was unable to keep the scope stable in winds over 6 mph. As a result, in March 2010 I decided to order a dome from ScopeDome (Poland) and I travelled to NM to install it with the help of a local contractor and the on-site astronomer. There were fundamental mechanical and electrical problems and it was not possible to commission the dome in the two weeks I was there. Over the next 7 months we were unable to resolve the problems with the manufacturere and ultimately had to fabricate my own solutions to the mechanical issues. I returned on 26th October 2010 to complete the task. The picture in the centre above (foreground dome) shows the new dome design. The remaining problems I have are all concerned with the successful use of sequencing programs and their method of controlling the dome rotation. These are still on-going and my imaging still remains largely manually controlled from the UK.
The weather monitoring
system is mounted on the external wall of the observatory and can be seen in
these pictures. The SMAP site has a similar system of its own but it is set up
to continuously record the main weather variables and displays them on a 24
hour graph as shown in this link: http://www.sacramentomountainastropark.com/weather.html
. An All-Sky camera is installed on the SMAP site which will also
allow me to see the condition of the sky for myself at any time. This will be
sensitive enough to pick out the main constellations and will cover the whole
sky in one continuously refreshed image. The pictures in the Equipment section
give some idea of the way the telescope is installed and the arrangement inside
the observatory.
GENERAL PRINCIPLES OF ASTRO-IMAGING
Almost all images are made up from multiple exposures taken sequentially through Red, Green, Blue and Clear filters. Other special filters are sometimes used for deep sky imaging. These "see" only Hydrogen Alpha (Ha), Oxygen III and Sulphur II emissions. These filters also have a very narrow band-pass but they are ideal for imaging nebulae and some planetary nebula. The Ha filter is often used to supplement normal RGB images - Ha emission is in the red end of the visible spectrum. The (Ha), R, G, B and unfiltered luminance (except for infra-red) exposures are later combined to produce the full colour images presented in the Gallery on this web site. Special digital image development software is used to do this frame processing once the raw images have been taken and almost always this is some time after the images were taken. In some cases, the images may be taken over a span of many weeks if the weather is poor and multiple long exposures are needed.
For more detailed information about the equipment and astronomical processing used to produce these images, please see the other pages of this web site or use the eMail link below.
Thank you for your interest.
If you would like to contact me for more information - click here: [email protected]
