Re: Newbie asks about xmas scope...

Hi Simon,

On 30 Dec 2005 10:59:02 -0800, "Simon James"
<sicommando@xxxxxxxxxxxxxx> wrote:

>My wife purchased a telescope for me for xmas from a site called
>"bestoptics". It's a Bushnell Northstar reflector, 76mm aperture,
>900mm length with goto.
>
>The scope came with two eye pieces and a barlow lens that looks like it
>fell out of a cheap cracker. I've ordered a set of six eye pieces from
>South West optics and some filters, seemed a bargain at just £99.
>Hope they're better than the rubbish the scope came with! (SR4mm and
>SR20mm).

They should be much better. As you know, the maximum magnification
that you can expect to be able to use is twice the aperture or the
'scope in mm (same as 50x the aperture in inches): 76 x 2 = 152. As
your new telescope is 700mm focal length this means an eyepiece of
700/152 = 4.6mm. Now it is likely that you will only be able to use
that magnification on very steady nights so I would think that the 6,
9 or 12mm eyepieces will be in the right range, giving magnifications
of 117, 78 or 58. When observing, use the lower magnifications first
and work up. Do ensure that the telescope is cool before using it,
leave it for a least half an hour or more to reach the same
temperature as the chilly outside.

>My one fear now (having not yet had a good try of the scope) is that
>the 76mm mirror will not be enough to see saturn, for example, at any
>decent magnification.

You will be able to see Saturn when the air is clear and steady enough
and the telescope in well collimated, but don't attempt any
collimation yet, you need to use the 'scope for a while to get used to
how the image is affected by the varying atmosphere and the different
magnifications that suit it.

>Needless to say I fell for the 525x mag as
>described on the site the scope was purchased from, that was before I
>understood about the 50x per inch guidelines, etc.

Yes, it's very deceptive, that sort of advertising and very common
too.

>My question is,
>does anybody know of a site where I can view images that were taken
>using a 3" reflector scope such as mine so as I can compare what I see
>with the art of the possible and decide whether or not to upgrade
>sooner rather than later!

There is the, rather good, 60mm refracter site at:

http://astrosurf.com/l60/en/index_en.html

Regards

- Mike

.

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