To Refract or to SC

"Robert Geake"
wrote in message ...

My quandry is this, i cant seem to find any decent refractors
above 4" without going for meade or celestron.

Nothing wrong with either, as long as you avoid the Goto toys. I
have a Celestron 150 6" f/8 achromat. It yields views just as
sharp as any APO, although with a not insignificant amount of
false color. Whether you find the purple halos objectionable
is a matter of personal taste. But for £650, I feel it is money
well spent.

Mark McIntyre wrote in message . ..
On 8 Oct 2003 11:26:16 -0700, in uk.sci.astronomy ,
(andrea tasselli) wrote:

If any 4" scope beats constantly a 10" one something is deeply wrong
with the latter. There is no known law of physics to allow for such a
difference in aperture not to win hands down.

You're assuming both are perfectly figured, aligned etc. AFAIR
refractors are easier to figure right, and stay aligned better. That,
plus other bits to do with the actual optical design, means they tend
to produce sharper images for a given aperture. Sure, you might gather
6x the light from a 10" buf if that is spread out over a larger area,
the result might be worse.


Well, yes, the usual caveat applies: "all things being equal". Sad
truth is that often things are nowhere near to being equal.
Nevertheless I would expect that a 10" at about f/5, if figured
properly, well acclimated and kept in tight collimation would still
yield far better images than a 4" would do, expecially if one thinks
about going the planetary imaging route.

Me think that if one wants to go down that route he/she better have a
big newtonian at f/6 or slower of fairly good size (8" or above)
instead of spending nearly or more money on a 4" APO for however good
this might be.

Of course a MN or a MCT is even better :-).

Best

Andrea T.

My Astronomy Pages at:
http://www.geocities.com/andreatax/index.htm

This thread has really cracked me up!
Twelve quotes most likely to get the fists flying:

1. I understand that refractors are very good for planetary / binary /
cluster
observations from experience(The little tal eats the Europa for brekkie
when it comes to that kind of observing).

2. SCTs are, IMHO must better than refractors if you intend to *use* them
and not just sit and admire them as penis substitutes.

3. .... and a 5" to 8" SCT blows away an
equivalent refractor easily, in terms of performance.

4. An SCT of an equivalent aperture (to apo refractor) is cheaper, and more
easily used and has almost the same performance,

5. ive looked through where actually worse than the TAL 4" refractor.
Including a 10" meade LX, a celestron 8" and an Orion Starmax.
It will take a lot of perswading to make me buy a Schmitt of any kind!

6. this happen with a goto SCT? I don't know because I have
resited the hype and have never owned one.

7. I must admit that I have been suckered in by the look of
these units from time to time. However, I get the impression that you
have to look a bit deeper than the glossy appearance.

8. Me think that if one wants to go down that route he/she better have a
big newtonian at f/6 or slower of fairly good size (8" or above)
instead of spending nearly or more money on a 4" APO for however good
this might be.

9. To date, the refractor has performed brilliantly in comparison to the
reflector and it has certainly given a number of it's bigger cousins
in the Meade and Celestron arena a damn good run for their money

10. It's only 80mm. That's the problem. (this one also works in the bedroom)

11. Hard to see why you'd want to buy a rinky-dink el-crappola short-tube
refractor to go with your apparently sub-standard reflector

12. I have a Celestron 150 6" f/8 achromat. It yields views just as
sharp as any APO,

Morgoth wrote in
:

On Wed, 08 Oct 2003 23:43:07 +0100, Mark McIntyre
inscribed in blood upon a parchment:

On 8 Oct 2003 11:26:16 -0700, in uk.sci.astronomy ,
(andrea tasselli) wrote:

If any 4" scope beats constantly a 10" one something is deeply wrong
with the latter. There is no known law of physics to allow for such a
difference in aperture not to win hands down.

You're assuming both are perfectly figured, aligned etc. AFAIR
refractors are easier to figure right, and stay aligned better. That,
plus other bits to do with the actual optical design, means they tend
to produce sharper images for a given aperture. Sure, you might gather
6x the light from a 10" buf if that is spread out over a larger area,
the result might be worse.

Only if the 10" is horribly miscollimated, dirty, misaligned, smeared
and so on.


Nah. Reflectors are just smoke and mirrors without the smoke. Get a REAL
telescope, a refractor!

Klazmon.




Best,
Dave
Author of the TalkOrigins Supernovae and Supernova Remnants FAQ
http://www.talkorigins.org/faqs/supernova/
Visions of Light, Visions of Darkness - Photography of Wessex
http://www.valinor.freeserve.co.uk/visions.html
Conception 2004 - the South Coast Gaming Convention
http://www.wessexgaming.org
Musings from Thangorodrim - A livejournal
http://www.livejournal.com/users/mrmorgoth

Geoff Smith wrote:
10. It's only 80mm. That's the problem. (this one also works in the
bedroom)

We'll defer to your more catholic experience here, Geoff.

Best,
Stephen

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"Stephen Tonkin" wrote in message
...
Geoff Smith wrote:
10. It's only 80mm. That's the problem. (this one also works in the
bedroom)

We'll defer to your more catholic experience here, Geoff.

Best,
Stephen

Is it the old "... is that an 80mm refractor in the bed or are you just
pleased to see me..."

Martin

On Fri, 10 Oct 2003 02:57:50 +0100, "Geoff Smith"
wrote:

This thread has really cracked me up!
Twelve quotes most likely to get the fists flying:

We're all quite civilised now though. A few years back and a verbal
war would have broken out.

Perhaps it's a realisation that the "this scope is better than that
scope" argument is largely pointless (with the obvious exception that
apo refractors are better than SCT's and Newts ;-) ).

If you want a fight these days, you really have to wade into the film
vs digital argument on a photographic forum. Oh boy, do they fly.
--
Pete
Homepage at http://www.pbl33.co.uk
CCD/digicam astronomy

On 10 Oct 2003 16:15:54 +1300, Llanzlan Klazmon The 15th
inscribed in blood upon a parchment:

Morgoth wrote in
:

On Wed, 08 Oct 2003 23:43:07 +0100, Mark McIntyre
inscribed in blood upon a parchment:

On 8 Oct 2003 11:26:16 -0700, in uk.sci.astronomy ,
(andrea tasselli) wrote:

If any 4" scope beats constantly a 10" one something is deeply wrong
with the latter. There is no known law of physics to allow for such a
difference in aperture not to win hands down.

You're assuming both are perfectly figured, aligned etc. AFAIR
refractors are easier to figure right, and stay aligned better. That,
plus other bits to do with the actual optical design, means they tend
to produce sharper images for a given aperture. Sure, you might gather
6x the light from a 10" buf if that is spread out over a larger area,
the result might be worse.

Only if the 10" is horribly miscollimated, dirty, misaligned, smeared
and so on.


Nah. Reflectors are just smoke and mirrors without the smoke. Get a REAL
telescope, a refractor!

Klazmon.

Fiddlesticks. Those are just glorified (and unwieldly) toilet rolls
with a couple of magnifying glasses stuck in at each end that give
back and neck ache to anyone lunatic enough to want to use them....

Best,
Dave





Best,
Dave
Author of the TalkOrigins Supernovae and Supernova Remnants FAQ
http://www.talkorigins.org/faqs/supernova/
Visions of Light, Visions of Darkness - Photography of Wessex
http://www.valinor.freeserve.co.uk/visions.html
Conception 2004 - the South Coast Gaming Convention
http://www.wessexgaming.org
Musings from Thangorodrim - A livejournal
http://www.livejournal.com/users/mrmorgoth

Author of the TalkOrigins Supernovae and Supernova Remnants FAQ
http://www.talkorigins.org/faqs/supernova/
Visions of Light, Visions of Darkness - Photography of Wessex
http://www.valinor.freeserve.co.uk/visions.html
Conception 2004 - the South Coast Gaming Convention
http://www.wessexgaming.org
Musings from Thangorodrim - A livejournal
http://www.livejournal.com/users/mrmorgoth