Sundries
Some bits and bobs I I use and make myself.
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- Oregon Scientific Weather Station
- Base Plate
- Balancing system
- ETX Rings
- Automatic Flip Mirror
- Focal Reduce
- 2 x Tele Converter.
- EXPO Jumbo 11 x 80 Binoculars.
- Meade Auto focuser for ETX scope
Oregon Scientific Weather
Station Have you ever looked at the weather forecast in the morning and found it promises clear skies that evening. Then looked forward to an evening of quality observing all day. Then after work set the telescope and camera up. Taken dark frames, light frames and bios. Sorted out a planned observing session. Everything is going so well that the
first object lands dead centre on
the CCD chip and you start taking the first exposure straight away. Then after
downloading it you decide something is not quite right. It's not as bright or
crisp as you think it should be. Then you realize, It's cloudy outside!!
(Remember I use a remote observatory and am largely unaware of the weather
condition outside.) This weather station will not completely stop this
scenario, but it will give a better dear of what's going to happen in the short
term and local area. I was given it two months ago for my birthday and find it
very useful. It It measures temperature outside as well as inside, barometric
pressure, indoor humidity, moon phases and also has an alarm clock. It is even
attractive enough to use as a bedside alarm clock. Although it is not one
hundred percent accurate it seems to forecast local conditions much better in
the short term than other available forecasts. I use it with the local forecast
on TV and radio as well as satellite images from the Web and usually get it
about right taking every forecast into account. It says on the box it's about
70% accurate where as I heard somewhere the Met. office only admit to getting
it right about 40% of the time. (This means that if you assume the forecast
will be the exact opposite the Met. people say you will be correct 60% of the
time)
Base Plate
It's a steel plate of about a quarter inch with holes drilled
and punched in it for eyepieces, CCD cameras and a slot around the outside to
hang the LX-200 control panel on. Between it and the Meade wedge I placed a
circular nylon gasket so the wedge moves more smoothly. It's attached to the
pier by four threaded stainless steel rods set into the concrete, locked into
place an inch above the pier by two nuts on each side of the plate. (I think If
I did it again I would only use three as it would be easier to set up and
level.) Another similar rod goes through the middle of the plate to mount the
wedge on with the middle hole. In the three slots on the wedge around the
middle hole I insert three bolts witch screw into three nuts I welded to the
bottom of the base plate. The bolts pass through oversized holes drilled into
the base plate carefully aligned with the nuts welded to the bottom.
Balancing system
I use a home-made 2D balancing system. It's mounted on a rail made out of an aluminium bar. Two notches are machined out on the sides and a hole drilled each end to mount on the scope. The screws are not long enough to go through the rail so longer ones have to be used.
(I live in England and found it very difficult to get hold of these longer
screws as the threads are a peculiar size in England. I tried to order them but
did not want the 50 minimum order so I made them up from scratch.) I made up
five of these rails and attached them all around the telescope to attach other
things such as the ETX scope and a camera. The trolley that rides on the rail
is made from a piece of steel and is fastened down tightly with a bolt. A steel
threaded rod is perpendicularly set into this and cut down so it does not snag
on the telescope mount. The weights are two cylinders of steel with a hole in
the middle threaded to fit the steel rod. I screw them onto the rod and they
lock by screwing the two cylinders together. I had noticed that the scope
tracked much better before it passed due south than after. This seemed to be
caused because the scope seems to track better when it is working against a
weight as opposed to with a weight. I helped to stop this by simply attaching
velcro strips to the fork arms of the mount and to a plastic milk bottle. Then
simply put a desired amount of water in the bottle and stick it to the fork
arms when the scope has past the half way mark. This is not perfect as it does
not help much past the due west mark and I have to make sure that the length of
exposure will not let the scope drift too far past the due south mark. I am
working on a system using springs as I think this might have the advantage of
working past the due west mark and the springs will also apply more strain as
the scope moves farther west. I found all the wires tended to alter the
tracking as they weigh quite a lot collectively. So these are tapped to the
scope and then tapped to one of the fork arms. This reduces the weight of them
as only about 4 inches of them are left hanging below the fork when the scope
is pointing due south. If it's pointing west or east then I tape them to the
centre below the scope. If I move the scope from my computer room by a large
amount I have to go outside to check that the wires are not tangled up or come
unstuck.
ETX Rings
The mounting is a simple affair. Two pieces of steel bent in a circle of about 8 inches. These are mounted on two trolleys similar to the one used with the balancing system. Three holes are drilled and threaded in each ring. Bolts with plastic caps to protect the scope are screwed into these holes and the scope is then fed through the rings and screwed hand tight.
Automatic Flip Mirror
When I got tired of constantly going to the scope to close the flip mirror for dark fielding I decided to automate it. (I don't use this now quite as munch as I found the flip mirror was occasionally moving by a small amount and spoiling the bias, flat field and dark frames.) I found a small 6 volt electric motor and mounted in a box I had kicking about. I connected the wires to the female end of a phone cable to make it easy to connect and disconnect the cables. I then took the handle off the flip mirror and attached a grooved wheel to it I also had kicking about. Then duck tapped the whole thing to the flip mirror and attached the motor to the wheel with a rubber band. Then I simply reversed the current to the motor from my computer room to open and shut the mirror. (I know the ST7 has a mechanical shutter on it but it is not completely light proof.)
Focal Reducer
I use a Meade Series 4000 f6.3 focal reducer and find it invaluable. It screws on the LX 200 and then the camera screws onto it. This provides a very stable and secure mounting for the cameras. It changes the f ratio from the standard f10 to f6.3 on the LX200. This makes the field of view about twice as big and so makes focusing and centring the objects much easier. I use it for the majority of my imaging because of this. The only problem I have with it is when I screw it on the scope with out letting it cool down to ambient temperature. When I try to take it off later it is very stiff as the focal reducer contracts as the metal cools.
2 x Tele Converter.
I had some time to kill and was looking around in one of those cash covert stores and found this 2 x tele converter for £5.00. It is designed for cameras but fits my ST 7 CCD camera perfectly. It works in an opposite way to my focal reducer. This means that it magnifies an image creating a smaller field of view. I have tried using barlows for planets, the moon and small objects with little success. The tele converter is ideal, but you have to be so so careful to focus correctly. I an now looking for a 3 x tele converter, but I doubt I will find one at the same price.
EXPO Jumbo 11 x 80 Binoculars.
One of my most useful and used toys. My 11 x 80 binoculars. The field of view is 45° which I find is as good as any. Culmination could be better but I know someone who can tweak them up. I wear quite strong glasses and sometimes I have problem focusing as some binoculars have limited focusing movement but these have ample movement. The lenses do not appear to be coated in any way. But as they only cost just under £100 I am quite happy with them. I attach them to a camera stand with an adapter readily available from any camera store.
Meade Auto focuser for ETX scope
I got the Auto focuser as a birthday present. I intend to use it for guiding through the ETX while taking photos through the LX-200 with 35mm film. To do this I extended the cable between the focus motor and the hand paddle to some 95 feet. I used heavy out door telephone wire. Despite the distances involved there seems to be no appreciable drop in power and the motor responds perfectly well. While doing this I found my first moan with this piece of equipment. The OE cable connects directly into the motor unit so the wire is permanently attached. Why they could not put a telephone jack on both ends I do not know. On the end, that fits into the hand paddle is a very small telephone jack (the type that fits into the hand held receiver part of the telephone) I had a big problem finding a female connector for this. In the end I had to buy a cheep telephone and use the plug in that.
The motor is not sensitive enough for CCD work but can be got around by using the small amount of play in the ETX focus knob. This takes extra time and becomes very annoying, but it is a way around the problem.
The hand paddle has two speeds and there is know way of telling which speed it is on with out activating it and you can easily over focus if you are not careful. Both of the above problems could be overcome if I could control it from the LX-200 control panel, as I could work it through a program on my computer. I understand you can control it through the ETX computer and hand paddle.
My biggest moan is the undocumented fact that while the motor part and the paddle are connected the battery is under constant drain. I have wasted 4 batteries now as I keep forgetting to unplug them when I have finished observing.
All in all I am not very impressed with it at all.
I would not recommend it to anyone.
This document maintained by
pete.cox@zetnet.co.uk.
Material
Copyright © 2000 Pete