Quote:
Originally Posted by JeniSkunk
What about the really small table top reflectors, like the 76mm reflector (Orion FunScope 76mm, Celestron FirstScope, Sky-Watcher Heritage 3 inch, Saxon Mini Dobsonian, ect) ?
Such supermarket/department store priced 76mm reflectors have even been sold by Aldi.
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Jenifur,
Now we head into the Dark Side of astro - the cheap.
What Nick and I have been discussing so far has been in relation to GOOD astro gear. To be able to push a scope to its theoretical limits, it needs to be a quality instrument. Sadly, the majority of what newcomers to astro buy is not good.
Before I go into tearing shreds off any item, I need to make something very clear, and something that is VERY CLOSE TO BOTH NICK AND MINE HEARTS:
"The best telescope is the one that gets used. If all you can afford is an inexpensive item, and you use it all the time, then it is just as good as the finest, most exquisite instruments humans have ever devised! And Damned be anyone who dismisses this."
So, knowing that cheap supermarket scopes are poor, we can discuss the Good, the Bad and the Ugly.
To make a scope cheap, then cheap and crude manufacturing techniques need to be used. And in turn, cheap scopes appeal to those people who unfortunately on a whole don't understand what they are buying. There's no right or wrong here, just a merge of two different forces - ignorance and market.
The requirements needed of an astronomical telescope are very stringent, and to produce such a high standard of instrument needs high quality materials and highly controlled manufacturing processes. And this costs money. Don't make the mistake of blaming China for cheap and nasty stuff. The Chinese are also very capable of making outrageously fine equipment, and today can rival and even surpass many traditional manufacturing powerhouses! Don't forget, some high profile Japanese and American brands have their entire product line now manufactured in China, and no one blinks an eye.
Those supermarket telescopes are not made using the optimal processes for a good astro telescope. They can't. These cheap scopes are entirely made to a price, and quality is only skin deep. Those 76mm reflectors are made with a poor quality spherical mirror, not a parabolic one. The eyepieces use plastic lenses, or uncoated glass lenses. This means that they are very poor at high magnification. These cheap scopes are best for low power wide field viewing, and they can deliver a very nice low power image. But they do not deliver a good high power image at all. They can't, and many people end up very disappointed with astronomy within 5 minutes and take it no further. And it's not just the figure of the primary mirror, but the cell it sits in, the focuser, the secondary mirror and its holder and the stalk that holds it. These can be altered to an extent to improve the little scopes performance, but these mods should not be something that the end consumer should be responsible for. These scopes are made to a price after all.
I have owned 3 of the Celestron FirstScope table top reflectors. All have been terrible at high power. I suspected this when I purchased my first, but I bought it as a had a particular use in mind with it, as big aperture finder scope, which meant I was exploiting its greatest strength - low power. And these scopes proved to be great for this. I had one mounted on my 17.5" dob!
Would I recommend these cheap little scopes to anyone? It depends. These would not be my first or second suggestion, but for better or worse they do fill a niche. As a first telescope, they may work out to be a wonderful introduction to astronomy for a little kids - my own children when little enjoyed this little FirstScope. For older, more discerning kids and for adults, not a chance.