ICEINSPACE
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Moon Phase
CURRENT MOON
Last Quarter 50.4%
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17-03-2011, 12:40 AM
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avandonk
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Join Date: Aug 2005
Location: Melbourne
Posts: 4,786
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Why direct drive is the Future
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17-03-2011, 12:57 AM
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Narrowfield rules!
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Join Date: Nov 2006
Location: Torquay
Posts: 5,065
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Yeah, whopp de do, show me the money!. Direct drive is not "WOW the future", its old hat and its future is "depending" on quite a few things. For us astro plebs, its an end performance/cost ratio that has a long way to go before it becomes universal and default.
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17-03-2011, 01:33 AM
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The 'DRAGON MAN'
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Join Date: Jan 2005
Location: In the Dark at Snake Valley, Victoria
Posts: 14,412
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Quote:
Originally Posted by Bassnut
Yeah, whopp de do, show me the money!. Direct drive is not "WOW the future", its old hat and its future is "depending" on quite a few things. For us astro plebs, its an end performance/cost ratio that has a long way to go before it becomes universal and default.
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That is a ridiculously arrogant and rude response!
It is actually quite a stunning piece of equipment.
8.38 MILLION steps per revolution is not old hat.
And I'm sure there are a few people in here that would be happy to part with the dollars for accurate tolerances like this.
So Whoop de do that!
No wonder some people refuse to post interesting items when they get repsonses like Freds!
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17-03-2011, 01:44 AM
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Old Man Yells at Cloud
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Join Date: Jan 2007
Location: Rockingham WA
Posts: 3,435
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Quote:
Originally Posted by ballaratdragons
That is a ridiculously arrogant and rude response!
No wonder some people refuse to post interesting items when they get repsonses like Freds!
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Agreed.
I was not aware such drives existed so thanks Bert.
Will be doing a bit more reading.
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17-03-2011, 07:57 AM
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Registered User
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Join Date: Mar 2009
Posts: 349
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Is that a direct drive system, such as the ASA DDM and Astelco NTM-500 type mounts, or a harmonic drive (with gears) like the Chronos mount? True direct drive systems do not use gears, and are therefore PE-less, so to speak.
The resistance to these new direct drive systems mostly comes from those who have invested heavily in the traditional (geared) type mounts.
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17-03-2011, 08:00 AM
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Mostly Harmless
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Join Date: Jun 2006
Location: Cairns
Posts: 1,349
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that would be 7 steps per arc sec yeah?, math never my strong point...
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17-03-2011, 08:00 AM
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Really just a beginner
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Join Date: Jun 2009
Location: Brisbane
Posts: 3,045
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Amazing that such technology still uses the RS-232 interface back to a computer...
DT
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17-03-2011, 08:34 AM
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Watch me post!
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Join Date: Mar 2006
Location: Melbourne
Posts: 1,905
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Gotta semi agree with Fred here.
While it looks good, its a long way from useable ( for a mount )
Reading the tolerances etc
"after correction" its 10arcsec position accuracy, so the quoted encoder resolution doeasnt appear to directly be useable.
I cant tell from the specs but i'm pretty sure the encoder is just a std unit, ie its absolute position is "calculated" by keeping track of a quadrature pulsetrain, vs having a true absolute encoder.
Must be used indoors, no moisture, thermally stable environment.
Holding torque is pretty low and it would appear to lose alignment if bumped.
Dont get me wrong, I like the idea of direct drives or harmonic drives,
but a good worm drive with a precision encoder ( preferably absolute )
on the output shaft will still achieve the same end, for a lot lower cost.
IMHO, the biggest gains for astro work will come when precision encoders become cheaper.
And even then, this still doesnt address refraction, flexure, other misalignments downstream of the axle etc etc,
Andrew
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17-03-2011, 09:00 AM
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Registered User
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Join Date: Aug 2009
Location: sydney australia
Posts: 832
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whats the difference between this direct drive and the maxxor motors you can get with a losmandy mount?
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17-03-2011, 10:02 AM
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Like to learn
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Join Date: Jul 2007
Location: melbourne
Posts: 4,835
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Very nice bit of engineering.I wonder if the company is still operating after the earthquake.
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17-03-2011, 10:12 AM
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Registered User
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Join Date: Feb 2007
Location: Beaumont Hills NSW
Posts: 2,900
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Quote:
Originally Posted by ballaratdragons
That is a ridiculously arrogant and rude response!
It is actually quite a stunning piece of equipment.
8.38 MILLION steps per revolution is not old hat.
And I'm sure there are a few people in here that would be happy to part with the dollars for accurate tolerances like this.
So Whoop de do that!
No wonder some people refuse to post interesting items when they get repsonses like Freds!
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Please don't take Fred too lightly. I know he likes to stir. but he does know what he is talking about.
Barry
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17-03-2011, 11:11 AM
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No More Infinities
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Join Date: Apr 2008
Location: Townsville
Posts: 9,698
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Quote:
Originally Posted by AndrewJ
Gotta semi agree with Fred here.
While it looks good, its a long way from useable ( for a mount )
Reading the tolerances etc
"after correction" its 10arcsec position accuracy, so the quoted encoder resolution doeasnt appear to directly be useable.
I cant tell from the specs but i'm pretty sure the encoder is just a std unit, ie its absolute position is "calculated" by keeping track of a quadrature pulsetrain, vs having a true absolute encoder.
Must be used indoors, no moisture, thermally stable environment.
Holding torque is pretty low and it would appear to lose alignment if bumped.
Dont get me wrong, I like the idea of direct drives or harmonic drives,
but a good worm drive with a precision encoder ( preferably absolute )
on the output shaft will still achieve the same end, for a lot lower cost.
IMHO, the biggest gains for astro work will come when precision encoders become cheaper.
And even then, this still doesnt address refraction, flexure, other misalignments downstream of the axle etc etc,
Andrew
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CDK700
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17-03-2011, 01:32 PM
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The 'DRAGON MAN'
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Join Date: Jan 2005
Location: In the Dark at Snake Valley, Victoria
Posts: 14,412
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Quote:
Originally Posted by Barrykgerdes
Please don't take Fred too lightly. I know he likes to stir. but he does know what he is talking about.
Barry
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I'm not debating his knowledge on the subject, just the rudeness of his post.
It is not worded as a 'stir'. It is total lack of respect to a poster.
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17-03-2011, 03:17 PM
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Narrowfield rules!
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Join Date: Nov 2006
Location: Torquay
Posts: 5,065
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Quote:
Originally Posted by ballaratdragons
That is a ridiculously arrogant and rude response!
It is actually quite a stunning piece of equipment.
8.38 MILLION steps per revolution is not old hat.
And I'm sure there are a few people in here that would be happy to part with the dollars for accurate tolerances like this.
So Whoop de do that!
No wonder some people refuse to post interesting items when they get repsonses like Freds!
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Sorry about that Ken, no offence intended.
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17-03-2011, 03:41 PM
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Registered User
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Join Date: Aug 2006
Location: Western Australia
Posts: 8,276
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Direct drive mounts are available as you Know but are still quite expensive and generally beyond the pockets of us poor amatuers
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17-03-2011, 03:45 PM
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No More Infinities
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Join Date: Apr 2008
Location: Townsville
Posts: 9,698
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Quote:
Originally Posted by TrevorW
Direct drive mounts are available as you Know but are still quite expensive and generally beyond the pockets of us poor amatuers
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That's the problem...but it's a matter of supply and demand, apart from anything technical.
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17-03-2011, 04:05 PM
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Registered User
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Join Date: Aug 2006
Location: Western Australia
Posts: 8,276
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True but each of the directs I've seen advertised are over $10k
ASA and Chronos
demand won't be an issue because of the price
look how well the EQ6 (in all it's guises) has done because it is a cheap mount that does what it does well for what you pay for
Personally I believe the Chinese are missing a complete market segment by not producing a good quality heavy duty mount around the $5k mark
If the EQ8 comes in at that price or thereabouts to be competitive then they'll be on a winner IMO
Sorry off track a bit
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17-03-2011, 04:08 PM
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Registered User
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Join Date: May 2009
Location: Thailand
Posts: 446
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Quote:
Originally Posted by renormalised
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You want to lend me the $185 000!!??....lol
Nice looking setup though!
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17-03-2011, 04:13 PM
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No More Infinities
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Join Date: Apr 2008
Location: Townsville
Posts: 9,698
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Quote:
Originally Posted by OzRob
You want to lend me the $185 000!!??....lol
Nice looking setup though!
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Put a lotto in for tonight....it's $20M 
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17-03-2011, 04:13 PM
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Certified Village Idiot
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Join Date: Jul 2006
Location: Mexico city (Melb), Australia
Posts: 2,359
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Quote:
Originally Posted by icytailmark
whats the difference between this direct drive and the maxxor motors you can get with a losmandy mount?
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About $25000. 
Well to answer this a little better...these direct drive units use harmonic drive mechanism that virtually eliminate backlash (they drive the axis directly ...no gear train) and also have very accurate encoders that can drive a scope (edit: keep the drive position accurate) so accurately that you probably don't need guiding (edit: auto guiding etc).
Well that's the principle. I guess they should work but they haven't yet reached mainstream ..yet. Probably due to high costs. More here.
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