Imaging Equipment 2002 / 2003
our most important bit of kit! We each own a pair of
Features include: Colour sensitve, enhanced low light capability at edges, variable aperture, chemical enhancement, automatic focus. No separate power supply required. Complete with a precision mounting system, which can, with practice, allow independent tracking.
Optional accessory: Moon Filter as demonstrated by Jools.
A few basic points on operation should be noted. When used for astronomy they are initially useless. After a few minutes, the automatic aperture system will have opened up and stars should become visible. Once the system has been in low light conditions for some minutes, the chemical enhancement system starts to work. The instrument housing will secrete chemicals slowly into the optical sensors which increase low light sensitivity. This effect can take over an hour to reach full power.
Binoculars - always a valuable astronomical tool, great for
observing great swathes of sky in a right-way-up sort of way. We
use a pair of Meade 9x63 binoculars, they give 9x magnification but have a
63mm diameter objective lens. We often attach the binoculars to a tripod -
very handy for pointing at an object and getting other people to look at the
Human eyes typically have 6mm diameter pupils during night vision so our binoculars collect about 100 times more light than the unaided eyeball. As the 9x magnification reduces brightness by 81x, the apparent brightness of the magnified image in these binoculars is about the same as the sky appears to the eye. Smaller binoculars tend to make an image darker and would be of less astronomical use.
Helios Explorer 200mm Newtonian reflector
- (Tom's Scope) This has
made a huge difference to our view of the skies! It is basically a 1
metre long tube, 200mm (8") in diameter which collects vastly more light
than an eyeball (roughly 1000x more). The light comes in the top of the
tube, is reflected by the 8" mirror at the base back up the tube, where a
small diagonal mirror sends the light out sideways through a port.
The image can either be captured directly by a camera or viewed using an
As the telescope collects so much light, it can be used to view bright objects at high magnifications or very dim objects at much lower magnifications - the amount of magnification is determined by the focal length of the eyepiece and the barlow lens(es).
Currently we have the following : 10mm & 20mm eyepieces, 2x
and 3x barlow lenses.
These combine to give effective magnifications from 50x-600x. On our lowest magnification (50x, 20mm, no barlow) the disc of the moon completely fills the viewfinder and is so bright it is best viewed with sunglasses!
The telescope sits on an equatorial mount, with recently added motors which compensate for the rotation of the earth so we can keep objects in our viewfinder more easily - all we have to do is point the mount's axis at the pole star - easy eh? The telescope is counterbalanced by two large weights on the mount so it is easy to manoeuvre.
Meade LX 200 - 250mm Schmidt Cassegrain - (Pete's Scope) This is a very silly telescope. Light comes in through the 250mm (10") annular-shaped lens at the top, down to the big curved mirror at the bottom which has a hole in, back up to the mirror in the middle of the top and then back down through the hole in the middle of the big mirror at the bottom. After all that bouncing up and down, the scope has an effective focal length of 2500mm. We did say it was silly.
Now for the clever bit... the telescope has a computer built in which knows about lots of stars and objects - we tell the scope where we are and what the time is, help it point at a couple of stars and then as if by magic the scope knows where everything is. As if that isn't magical enough, by means of a serial cable, the scope can be hooked up to a computer running skymap which can then move the scope to any object you like and track it - even satellites if you're that way inclined.
So how does it compare to Tom's scope? It's a lot heavier; it's big box barely fits in Tom's car. Dim objects appear much brighter but not much improvement on planets. Alt-Az mount makes it less useful for long exposure photography - equatorial wedge will sort that out shortly. A lot faster to hop between objects - great if you want to image as much as possible in a short time, not so great if you want to appreciate how tricky it is to find things for yourself.
Logitech QuickCam Pro 4000 - this was picked up in a sale at PC World for 30 pounds. It has been unceremoniously stripped of its funky spherical surround (left) and its cheap plastic lens. Its circuit board complete with chip were then fixed to a spare lens tube with blu-tac and placed at the prime focus of the telescope. Suitably impressed with the resulting images, the circuit board was then modified to allow long exposure images to be taken; a plastic guide was then fashioned to help position the CCD in its new housing. The webcam output is captured at 640x480 and then processed by K3CCD Tools, Registax and Photoshop to produce the images on display on this site.
Pentax P30T - a 10 year old SLR camera not ideally suited to astrophotography. Although the P30 does a wonderful job in daylight, it isn't so good at night time - it is difficult to focus in low light and the mirror movement can cause the camera to shake. It also requires batteries to hold the shutter open. The camera can be attached at the telescope's prime focus using a T-Mount but as yet knowing how long to hold the shutter open is a matter of trial and error. The resulting photographs are affected by film type and developing method as much as the paramaters used for taking the photograph, as such the P30 won't be used much until we have mastered the art of using the CCD.
Click Here for a chart demonstrating the various magnifications currently available to us.
Laptop - The laptop currently being used to drive the webcam has a high propensity to crash, it does however benefit from a moderately large disk to store the vast quantities of images captured in a session - it also makes transferring the large images between Tom, Jools and Pete's houses slightly easier.