60mm Refractor Vs 76mm Reflector
the hot steppa
I have been looking at getting a really cheap scope just so i can have a
look at whats going on out there.....
I started off thinking I dont need much, its only a whim, so I would get a
cheap 50mm one for £30, and if I like it I can always upgrade.
I scoured the net and most info seemed to say to go for at least 60mm for
refractor, or 76mm for a reflector. It is more than I wanted to spend on my
whim but I dont want to be put off the whole idea by buying the wrong scope.
I have now set my limit at £75, which may not sound much but its trippled
from my initial, 'hey i wanna look at the stars' figure. All I want is an
entry route into the subject, I would love to see clusters and nebulae but
do have a realistic idea of what I can see for £75.
So my question is this, should I get a :-
a)50mm refractor by a good manufacturer
b)60mm refractor by a cheap manufacturer
c)76mm reflector by a cheap manufacturer.
It doesnt need to be particularly portable, It will mainly be for garden
viewing and rigging up my digital camera to.
I am thinking the reflector because I get more diameter (and light
collection) for my money.
They will all cost roughly the same I think, so what the advice ?
second hand is fine by the way so if anyones got advice on that its welcome.
tia
please answer only in this group, no email. thanks.
Starstuffed
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Starstuffed
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"the hot steppa" <n...@email.please> wrote in message
news:ap3emm$5e7$2...@news6.svr.pol.co.uk...
the hot steppa
Would I be better off forgetting the whole idea ?
I guess its like wanting a BMX and being given a grifter.
At £75 second hand that should equate to about £140 new price, surely there
is something ?
I have saved my money to move from the toys up to the bottom of the range
scopes. If thats not enough I cant justify spending more, I only want to try
it out. Perhaps I will leave it to the rich, and buy their books instead.
I know its advised to go for a pair of bins, but I particularly wanted
digiphotos.
Surely a tasco with 60mm lens will be ok for pictures of the moon ?
I am not asking to prove the origins of the universe, that will come when I
upgrade.
anyway if i do get something, i am bound to pop back in here with more
questions.
"Starlord reach.com>" <starlord@in<*> wrote in message
news:yaet9.530$T62.24...@news.inreach.com...
David Knisely
> So my question is this, should I get a :-
>
> a)50mm refractor by a good manufacturer
> b)60mm refractor by a cheap manufacturer
> c)76mm reflector by a cheap manufacturer.
None of the above. Get at least a 60mm (or larger) refractor or a
114.3mm (4.5 inch) reflector from a reputable manufacturer. 50mm is a
bit on the small side, but you should also consider some 10x50
binoculars, as with a tripod to hold them, they make a cost-effective
way of getting into amateur astronomy. I also like the 80mm refractors
being sold by Meade, Celestron, Orion, ect. Clear skies to you.
--
David W. Knisely KA0...@navix.net
Prairie Astronomy Club: http://www.prairieastronomyclub.org
Hyde Memorial Observatory: http://www.hydeobservatory.info/
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the hot steppa
"James Cook" <james.spam...@btinternet.com> wrote in message
news:ap4en4$msq$1...@helle.btinternet.com...
>
> > I guess its like wanting a BMX and being given a grifter.
>
> Oh come on, grifter beats BMX hands down. Gear change on the left grip
> (didn't we all pretend we were riding motorbikes?), impressive weight
(kill
> a dog if you run one down I reckon) and they only come in 2 colours. Ahh,
> down the park, jumpers for goalposts................
>
>
>
>
James Cook
> I guess its like wanting a BMX and being given a grifter.
Oh come on, grifter beats BMX hands down. Gear change on the left grip
KC5CQW
60mm refractor and a 76mm reflector. If you must stay in this size range go
with the refractor. In the 76mm reflector, you'll lose about 2cm in
obsruction from the secondary mirror. By next year I'd like to get an Orion
Astroview 120EQ. I really like the Orion line of scopes. They are at
www.telescope.com you really can't find an easier website to remeber!
I did a side by side of the two scopes, (both El Cheapo's) and I found
a drastic differince in the brightness and clarity. The refractor won and I
beleave it was 'cuz of the secondary in the reflector.
You can also look into one of those cheap Russian spotting scopes with
an alt/az tripod for a camera. I used on for years and it gave me wonderful
wide angle views. However, at that price, you may want to get some good
binoculars with a tripod mount.
From personal exp. good bino's are far better the a cheap scope any
day. Plus you can take them anywhere.
"the hot steppa" <n...@email.please> wrote in message
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Martin Lewicki
"the hot steppa" <n...@email.please> wrote in message
news:ap3emm$5e7$2...@news6.svr.pol.co.uk...
> So my question is this, should I get a :-
>
> a)50mm refractor by a good manufacturer
> b)60mm refractor by a cheap manufacturer
> c)76mm reflector by a cheap manufacturer.
60mm are the most common small refractor. I lived with one for years. Did
lots of succesful lunar photgraphy with it. Brands like Tasco are usually
good. The eyepieces however often leave much to be desired, but are ok to
begin with.
A 60 mm will give nice views of Venus (phases), Mars (at close approach),
Jupiter and Saturn - including satelite eclipse shadows on Jupiter. It will
show Casini's division in Saturn's rings in good viewing conditions. Even
Uranus shows a discernable disk. It will, resolve dozens of clusters, give
nice views of the Orion and other nebulae including planetary nebulae, split
dozens of binary stars, track many asteroids, follow many comets and the
Moon will keep you entertained for ages.
You can't do all this with binoculars!
Small-scope viewing refines your observing skills, especially with faint
objects. This pays off when you migrate to a larger scope.
So I reckon go for a 60mm. However, many of these scopes vary in optical
quality so arrange to test drive (money back) gaurantee if you can.
Martin Lewicki
Jornada
I'm not sure if you can really resolve Uranus into a disk using a 60mm...and
a Tasco at that.
My etx 105 can barely show that disk and that was at x388.
Unless you have excellent optics like Takahashi, Televue or Borg, i think
the rule-of-thumb for maximum mag is aperture (mm) x2 . Hence a 60mm
normal optics scope will probably provide good image under good seeing
condition up to x120 after which the image will breakdown (i.e. unable to
focus)...
Am I wrong on this?
--
If replying directly, please delete "abc" from e-mail address.
Thanks
"Martin Lewicki" <mlew...@ozemail.com.au> wrote in message
news:Tr4w9.22285$Sr6.6...@ozemail.com.au...
Martin Lewicki
news:aprkbn$adk$1...@mawar.singnet.com.sg...
> Hi,
> I'm not sure if you can really resolve Uranus into a disk using a
60mm...and
> a Tasco at that.
> My etx 105 can barely show that disk and that was at x388.
> Unless you have excellent optics like Takahashi, Televue or Borg, i think
> the rule-of-thumb for maximum mag is aperture (mm) x2 . Hence a 60mm
> normal optics scope will probably provide good image under good seeing
> condition up to x120 after which the image will breakdown (i.e. unable to
> focus)...
> Am I wrong on this?
The Rayleigh criterion for a 60mm lens is 2.3 arcs seconds. This is the size
of the airy disc of a point source like a star under good seeing condition
and good optics.
Now, the size of Uranus at opposition is 3.7 arc seconds. This means the
airy discs of which the image of Uranus is comprised will overlap to produce
a disc 3.7 arc sec. Uranus would therefore look a bit larger (~60%) than the
single airy disk of a comparable star. That is, it is resolvable as
non-stellar. In fact it looks like a dull grey-blue extended "star" in my
60mm telescope. You can tell it is not a star.
Not so Neptune.With size 2.2 arc seconds it does not quite make the Rayleigh
criterion and looks just like any other comparable star. This is one
instance where using high magnification _is_ desirable. When doing
threshold observing like this you need to magnify the image so that the airy
disks are large enough for you to discern the difference. Of course you need
good seeing conditions, but not necessarily excellent seeing.
Good observing is training yourself to use the capabilities of your eye and
of the instruments at hand.
Martin Lewicki
Martin Lewicki
> I'm not sure if you can really resolve Uranus into a disk using a
60mm...and
> a Tasco at that.
> My etx 105 can barely show that disk and that was at x388.
> Unless you have excellent optics like Takahashi, Televue or Borg, i think
> the rule-of-thumb for maximum mag is aperture (mm) x2 . Hence a 60mm
> normal optics scope will probably provide good image under good seeing
> condition up to x120 after which the image will breakdown (i.e. unable to
> focus)...
> Am I wrong on this?
The Rayleigh criterion for a 60mm lens is 2.3 arcs seconds. This is the size
of the airy disc of a point source like a star under good seeing conditions
and good optics.
Now, the size of Uranus at opposition is 3.7 arc seconds. This means the
airy discs of which the image of Uranus is comprised will overlap to produce
a disc 3.7 arc sec. Uranus would therefore look a bit larger (~60%) than the
single airy disk of a comparable star. That is, it is resolvable as
non-stellar. In fact it looks like a dull grey-blue extended "star" in my
60mm telescope. You can tell it is not a star.
Not so Neptune.With size 2.2 arc seconds it does not quite make the Rayleigh
criterion and looks just like any other comparable star. This is one
instance where using high magnification _is_ desirable. When doing
threshold observing like this you need to magnify the image so that the airy
disks are large enough for you to discern the difference. Of course you need
good seeing conditions, but not necessarily excellent seeing.
Good observing is training yourself to use the capabilities of your eye and
of the instruments at hand.
Martin Lewicki
> "Martin Lewicki" <mlew...@ozemail.com.au> wrote in message
David Knisely
> Unless you have excellent optics like Takahashi, Televue or Borg, i think
> the rule-of-thumb for maximum mag is aperture (mm) x2 . Hence a 60mm
> normal optics scope will probably provide good image under good seeing
> condition up to x120 after which the image will breakdown (i.e. unable to
> focus)...
> Am I wrong on this?
Well, sort of. The maximum power that can be used with a telescope is
not a hard and fast thing. At powers beyond 120x, a 60mm scope of
reasonable quality will still be able to "focus", but on extended
objects like planets, it will show little if any more detail than it did
at 120x. However, I have pushed the power on these scopes from 120x to
150x, and still gotten reasonable views. High power is also useful for
detecting elongation in double stars which are close to or a little
below the resolving ability of a given aperture. For making some gross
detail easier to see, sometimes you have to push things a little.
However, powers much beyond 3x to 4x per mm are probably more or less
nearly useless. Clear skies to you.