Telescopes
Helios 200mm
ETX 70
ETX90 in its case
Our new recommendation for 2005 - the Orion Starblast
click the image for a review
Before we started our club, we had read criticism of 'goto' scopes in the astronomy press . Some feared that they would take the skill out of astronomy. Our conclusion is -it's rubbish! Students have found the scopes a challenge to align. Experienced astronomers have little problem with them but beginners still need support and help. Whilst a 'goto' scope will allow experienced children to explore further, they will be able to make a much less frustrating start with a simple manual scope like the Starblast. We also strongly recommend the use of non-magnifying red dot type finders with all telescopes.
Our most popular scope is a 200m Newtonian reflector on a Dobsonian mount. Its enormous, strikes fear into parents who ship it backwards and forwards in their cars, and takes up quite a bit of room in their houses too. That said, it's easy to use and gives spectacular views of planets and deepsky objects like the Orion Nebula and Andromeda Galaxy. It can resolve features on the Moon down to 1km (Hadley Rille). However it is completely manual. A popular option that some members do, is to borrow it with one of the little ETX 70s, using the widefield goto to find objects and then following them with the Dob. It's also very cheap.
Two Meade ETX 70s and a Celestron 80GT were our first scopes.
The Celestron is better optically and its metal build will probably outlast the ETXs. However its big and bulky, particularly in its case. It has to be mounted on its tripod and it can't be used without power. We did have a problem with the star diagonal (the right angle bit connecting the optical tube to the eyepiece) but a bit of glue sorted that out.
The Meades are light, plasticy and not so good optically. You can see that Saturn has a ring and that Jupiter is banded (i.e. its better than Galileo's) but upping the power won't resolve anything else. Imaging using a digital camera tends to be limited to whole moon shots and sunspots with a white light filter. The goto works very well although the tracking isn't really up to long exposure film shots. Using the 25mm eyepiece (14x) with a 3X Barlow gives greater eye relief (eyeball to eyepiece distance) and is far easier for most people than the 9mm. Their case is small, light, strong and fully fitted. To make aligning easier you also need to add a Celestron red-dot finder and stick it on the tube with double sided, foamed sticky tape. In fact we are adding this finder to all of our scopes. The Meade's computer handset (unlike the Celestron's) can have data added to it using a PC and connection to Meade via the internet. You can also write your own tours and upload them to the handset. You need an extra cable to do this. The telescope can be used on a table without its tripod. To sum up the ETX 70 would be our choice for a scope that needs to go home. It's very portable, even by small children, versatile, robust, great for widefield observations and cheap. It's only let down by its optics at high magnification.
With support from our sponsor (The Royal Commission for the Exhibition of 1851) we were able to buy the next telescope up the Meade ETX series - the ETX90. This scope is a Maksutov Cassegrain design. Cassegrain because it has a primary mirror with a hole in it and Maksutov because its objective lens is deeply dished and has the secondary mirror silvered on its inner surface. This means that for a reflector it's nice and compact. Its optically far better than the ETX 70 but the price for this setup is far higher. The ETX 90 allows close up views of the Moon and the opportunity to record them by poking the lens of your digital camera into the eyepiece. The main bands on Jupiter are easily seen. The disk of Saturn's rings and the gap between them and the planet can be spotted. The narrower field of view makes this scope not as good for widefield views of star fields as the ETX 70 and it's small aperture means that dim deep star objects are uninspiring. Seeing the ring nebula by averted vision is not something that excites most beginners.
Power. We used the relatively new rechargeable alkaline batteries (cells to scientists). These give a higher voltage which the ETX90 needs and the 70 prefers. They need a dedicated charger and, awkwardly, need 6 cells whilst the charger can charge only 4 at a time. There are two other options. Get students to supply their own good quality alkalines and take them out when they return the scope. Buy an external power supply. The second option is initially expensive and is something else to have to lug home and trip over in the dark but its reliability is attractive. You can also power other things like dewshields and lights.
If you have the money for one observatory unit buy a 6 inch (150mm)Helios Dob.
If you have money for two buy an ETX70 and a Helios Dob.
If you're rolling in money, think about the ETX90 instead of the 70.
If you use our advice in setting up astronomy at school, please let us know.
Home Astronomical Observatories
Helios 200mm or 150mm Dobsonian Home Astronomical Observatory:
Helios 200mm or 150mm Dob (incl. OTA, Dobsonian base, focuser, finderscope, 26mm and 10mm eyepieces, 2x Barlow lens) accessory case, Celestron red dot finder.
For younger pupils, who would find the 200mm too heavy to carry into the garden, the 150mm is still very good even on deep sky objects (and even cheaper).
Meade ETX 70 Home Astronomical Observatory:
Meade ETX 70 (incl. hand computer, tripod, tripod case, 25mm and 9mm eyepieces) Custom case, 2 sets of alkaline rechargables and charger or Powerstation., Celestron red dot finder, computer connection cable, dewshield, 3x Barlow lens, scopetronics solar filter, scopetronics focuser, align-mate compass level.
Meade ETX 90 Home Astronomical Observatory:
Meade ETX 90,Autostar hand computer, tripod, tripod case, 25mm and 9mm eyepieces,Custom case, 2 sets of alkaline rechargables and charger or Powerstation., 2x Barlow lens, Celestron red dot finder, computer connection cable, dewshield, scopetronics solar filter, scopetronics focuser, align-mate compass level.