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Telescopes & Equipment

Skywatcher Explorer 200PDS

My first telescope was a Skywatcher Explorer 200PDS, an 8 inch Newtonian reflector. This is quite a big scope in physical size, and the 8 inch mirror is good for visual observations, but its fast f5 focal ratio makes it pretty good for imaging. I use it mainly for imaging the Moon and planets. It is mounted on the NEQ6 Pro GOTO mount, a heavy duty mount that can just cope with the 200PDS once all the cameras and guiding equipment are attached. My first four years of astronomy have been done with the scope set up on the patio. 

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Skywatcher Evostar 80ED

The second scope I bought was a Skywatcher Evostar 80ED Pro, 80mm F7.5 Apochromatic refractor, fitted with Skywatcher's dual-speed Crayford focuser. The scope, which arrived in January 2015, was just the basic package without the finderscope or diagonal as these weren't needed. This scope is used for more deep sky targets, particularly large nebulae that cover a large area of sky, and won't fit on the DSLR sensor when using the 200PDS with its longer focal length.

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It is seen here on the NEQ6 mount, shortly after being piggybacked on the 200PDS, hence the extension bar for the weights.

I have also made use of it on this home made MDF mount. With this, it is ideal for quick Solar and Lunar imaging sessions with the Nikon DSLR.

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Celestron 76mm FirstScope

In October 2016, I bought a Celestron 76mm FirstScope for my daughter. I plan on using it too, when the Sun or Moon are too low to be seen from the observatory.

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solarscope1.jpg (178645 bytes) Lunt LS50THa Solar Scope

In September 2015, I got a Lunt LS50THa Hydrogen Alpha Solar Scope. This allows me to view and image the Prominences, Filaments and other Ha features that are invisible to White Light.

It didn't come with a case, but found one at B&Q for 12.00, with a slightly damaged lining, but was able to get it for the reduced price of 5.00. The foam the scope came in was cut down to fit the new box. solarscope2.jpg (150409 bytes)
130m2.jpg (78105 bytes) Skywatcher Explorer 130M

I had no plans for another scope, but this was too good to pass on to give me some portability now my mount is in the observatory.

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Computer Shade

When imaging the Sun, or daytime Moon, a bright sky and reflections in the laptop screen don't make for easy laptop operation!

To solve the problem, I built this collapsible wooden box for the computer. It will flat pack away in the observatory when not needed, but is quick to slot together.

There's a black fleece that pulls over the top, large enough to pull over my head, but it also has a small opening cut in the front just big enough to see through so I don't need to completely hide all the time, as it can get hot under there.

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Observatory Build

In December 2015, I began to wonder if there was space for a permanent observatory. Carrying all the equipment up two sets of steps to the patio was a pain, but clearing it away in the freezing cold and when tired was ever worse.  The photos below show an impression of what is planned.

See more details of the observatory build here.

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All Sky Camera Housing

 After spotting a security camera dome on Ebay for a couple of pounds, I got around to building a housing for an all sky camera. The camera mounts from below and the whole housing is removable to protect the dome from extreme weather and UV.

More details of the build can be found here.

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Imaging Equipment

Nikon D3200 camera

The D3200 is the replacement for the D50. While still a base model, its technology is far ahead of the D50. It will probably only be used for Solar and Lunar imaging, in addition to general DSLR imaging of my other hobbies.

Canon Rebel T3i/1100D camera

As of March 2014, my deep space imaging is being done with an Astro-modded Canon 1100D. It is a significant improvement over the 8 year old Nikon D50, though I will be still using that for Solar and Lunar full disc images.

ZWO ASI 120MM

This is the mono version of the popular ZWO camera. It is good for Planetery, Solar & Lunar Imaging, although I've dabbled with long exposures of small deep sky targets. It was purchased along with a filter wheel and LRGB filters for planetary imaging.

ZWO ASI 120MM

I tried a friends colour ASI120 and was impressed enough to go for one myself. I chose the mono and filter wheel as a more flexible approach to planetary imaging. In addition to the LRGB filters, there is also a 742nm IR Pass filter for the Moon.

ZWO ASI 120MM

15 months after the first, I got another ASI120MM, just for solar imaging. This one is connected to the cooler and has the solar continuum filter and IR block filters permanently fitted, avoiding the need for removing the camera from the filter wheel.

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Atmospheric Dispersion Corrector

As light passes through the atmosphere, it is refracted into its component colours. The lower in the sky the object is, the greater the refraction is. The Atmospheric Dispersion Corrector uses two adjustable prisms to bend the light by an equal and opposite amount to correct the effect of the atmosphere.

The planets are all quite low in the sky for observers in the Northern hemisphere, and so the ADC should help to compensate for that low altitude and allow sharper images.

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The GIF to the right shows the effect of the ADC on a Bahtinov mask.
 
Nikon Remote Trigger and Light Pollution
Nikon cameras can only do 30 second exposures, or 'bulb' settin for longer. To avoid vibration, the 'bulb' needs an infra-red trigger. The USB-IR Camera Trigger is operated via a laptop, with software that can be used to set the length and number of exposures. scope6.jpg (142306 bytes) The Skywatcher Pollution Filter cuts out the orange sodium light while allowing the rest of the spectrum to pass through. It can be used for imaging through the scope, or with the stepdown ring to allow the filter to be fitted to the camera lens for widefield imaging. scope8.jpg (92971 bytes)
 
Guiding
TS 9mm Off Axis Guider

After much deliberation about guiding options, I settled for an off-axis guider rather than a separate guide scope. This takes the light from the edge of the viewing area, and directs it to a second camera which is used for controlling the position of the telescope. While there were a number of OAG's available, I was concerned as to whether the thickness of the OAG would prevent focus.

 

My guide camera is the Starlight Xpress Lodestar Autoguider. Regarded as one of the most sensitive guide cameras on the market, something that is needed with my OAG and in my light polluted area.
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Due to the limited back focus of Newtonian scopes, I ended up with the very slimline TS 9mm Off Axis Guider. I've recently discovered that the ASI120 fits the OAG, so hope to experiment with that on small Deep Space targets.

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scope10.jpg (80301 bytes) I've made this aluminium clamp to hold the cables. This is to create a strain relief so they are not pulling on the plugs and sockets on the back of the camera as the mount moves.
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Flat Field Panel
flatfield1.jpg (134544 bytes) In order to stop vingetting of the images, I need to take 'flats'; a plain evenly illuminated image recording the light distribution across the sensor. I used to do this with a desk light and white cloth stretched over the scope. flatfield2.jpg (151277 bytes) At a dark site, I can't shine a bright white light, spoiling everyone's night vision. Instead I made this self contained light box, that fits over the end of the scope. It is powered by the same 12 volt battery that powers the telescope.
 
Motor Focusser and Bahtinov Mask
focusser1.jpg (118543 bytes) This is my motor driven focusser, utilizing an old R/C servo motor and elastic bands onto the fine tuning wheel. The bands can be slipped off for manual control. Power for the focus motor comes from four 1.2volt batteries in this box. A double pole double throw centre off switch controls the motor direction. focusser2.jpg (78409 bytes)
scope9.jpg (140435 bytes) The Bahtinov Mask, designed by Pavel Bahtinov, is an aid to focussing a telescope. The grid lines take advantage of diffraction spikes caused by objects ahead of the main mirror, and make a pattern which can be seen in the picture to the right. Adjusting the focus moves the central line between the two diagonal lines. When the central line is equidistant, the image is correctly focussed. scope11.jpg (48908 bytes)
 
Water Cooling for the ASI 120MM
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Having tried the ASI120 for long exposure deep space photography, I decided the next step was to cool it to reduce noise. This should also be of use in the Summer imaging the Sun, where sensor temperatures can rise to 40+ degrees Centigrade.

See The Conversion Here

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Solar Imaging and Observing

solar1.jpg (89588 bytes) To the left is my first home made Solar Filter. I was advised at the time, that there was little point going larger than 100mm aperture for the main filter.

It uses Baader solar filter material that blocks 99.9% of sunlight, allowing safe observing. The wooden frame and covers protect the fragile film.

solar2.jpg (109360 bytes) These are my new Solar Filters, 190mm for the 200PDS and 100mm for the 80ED. The larger filter uses the original finder screen and filter. This will hopefully give better resolution for imaging, and lower the native f number from f11 to f5.25.
To allow a quick grab and go solar capture set up, I made this Baader filter for my 70-300mm DSLR lens. It lives in the camera case so I can shoot the Sun any time I'm out and about and the Sun is out. The wood case protects the fragile film. 300mm_filter.jpg (219681 bytes) In early December 2014, I bought a 1.25in Baader Solar Continuum filter ( right filter ), to improve my white light images. It needs to be used with a UV/IR block filter as it leaks IR itself ( left ). So far, the seeing has been poor for tests, but have still given good results. solar3.jpg (91210 bytes)

Telescope Maintenance 

focusser3.jpg (58412 bytes) Because of the difficulty in reaching the retaining screw with the OAG fitted ( see left ), I drilled and tapped a new hole ( right ). I also faced the focusser drive surface with 1200 grit wet and dry paper, to stop it slipping due to the camera weight. focusser4.jpg (86230 bytes) focusser5.jpg (67310 bytes)
In addition to a Cheshire collimator, I've also got a laser version. Now that I have a guide camera and can start taking long exposures, I want to make sure the optics are properly aligned, and I can now check in the dark. collimator.jpg (121139 bytes) To monitor observing and imaging conditions, I got a thermometer and hygrometer. It is most useful to monitor the temperature for taking 'Darks', and also the humidity for seeing conditions for both visual and imaging. thermometer1.jpg (101775 bytes)
dew1.jpg (98988 bytes) My battery box uses an 80 AH leisure battery and has two cigar lighter sockets, plus the four dew heater controllers and output sockets. dew2.jpg (95926 bytes) This is one of the home made dew heater strips around the front of the scope. This along with a short length of camping mat, keeps a little warm air around the secondary mirror. Another sort heater is used on the finderscope.

Transport & Storage

The 200PDS tube is about 9 inches diameter and about 40 inches long. It is a big lump to store. I made this storage and transport case to protect it and the eyepiece case during transit. Of course, now I have the observatory, it's not needed much. scopebox1.jpg (83759 bytes)
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The equitorial mount is the most expensive part of the whole system. It is also very heavy, so I wanted a sturdy flight case to keep it in should it need to be transported. The balance weights are also kept in this box, but with them inside, it is just within my ability to lift. scope4.jpg (132270 bytes)
scope5.jpg (137368 bytes) The eyepiece and accessory case has filled up since this picture was taken. In addition to eyepieces, 1.25" & 2" adapters and barlows, it has the telescope handset, guiding accessories, USB leads, Off Axis Guider, Filters, Collimator, a red torch and some tools.

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