A Space & astronomy forum. SpaceBanter.com

Go Back   Home » SpaceBanter.com forum » Others » UK Astronomy
Site Map Home Authors List Search Today's Posts Mark Forums Read Web Partners

Barn Door without the Door?



 
 
Thread Tools Display Modes
  #1  
Old August 2nd 05, 11:37 AM
JamesB
external usenet poster
 
Posts: n/a
Default Barn Door without the Door?

Looking online at these types of mount for widefield. I have read plenty
about the fact that a simple drive will lead to errors as the angular rate
changes over time, and that a "double hinge" method is better.
What I was wondering is if anyone has ever tried driving the hinge mechanism
directly? Instead of the threaded rod, simply gear down the motor enough
(which would increase the torque) and drive the hinge directly at the right
speed?
I'm guessing I am missing something obvious here else I'd have found people
who have done it... is it too hard to get the right speed through gearing?
Or is there some other reason? If it could be made to work it would surely
produce a lighter and more compact mount.
James.


  #2  
Old August 2nd 05, 03:06 PM
external usenet poster
 
Posts: n/a
Default

(If I understand you correctly...)
The point it is not of it being lighter (most likely it won't) or more
compact (most likely it will). The point of the barn door tracker is
that it's easy to manufacture with commonly available materials and
parts. If you were to drive the swivelling platform directly you'd have
essentially a RA drive and that would require, in its turn, quite lot
more work and sophisticated parts, and likely access to a lathe as
well.

Andrea T.

  #3  
Old August 2nd 05, 06:39 PM
Robert Williams
external usenet poster
 
Posts: n/a
Default

Hi there James,

this is slightly OT, but have you considered an equatorial
driven head for a camera tripod. It uses a ball joint mounted
1/4" camera mounting mated to a synchronous motor driven
right ascension axis, and runs off 12 V DC (600rpm motor geared down
via a planetary gearbox to 1 rpd).

There is also a simple 'hinge' to adjust the polar axis and I've upgraded
it with a 6x30 finderscope with cross-hairs to act as a polar finder.

I have one (from Beacon Hill Telescopes, Beverly)
and it works a treat. I have done 5 minute exposures with very little star
trailing
(provided I take time to set up the polar axis accurately).
I've acquired a anti-rotating motor (from BHT) for southern
hemisphere use.

I can a pic if you are interested.

Robert
"JamesB" wrote in message
...
Looking online at these types of mount for widefield. I have read plenty
about the fact that a simple drive will lead to errors as the angular rate
changes over time, and that a "double hinge" method is better.
What I was wondering is if anyone has ever tried driving the hinge
mechanism directly? Instead of the threaded rod, simply gear down the
motor enough (which would increase the torque) and drive the hinge
directly at the right speed?
I'm guessing I am missing something obvious here else I'd have found
people who have done it... is it too hard to get the right speed through
gearing? Or is there some other reason? If it could be made to work it
would surely produce a lighter and more compact mount.
James.



  #4  
Old August 2nd 05, 06:51 PM
JamesB
external usenet poster
 
Posts: n/a
Default


wrote in message
oups.com...
(If I understand you correctly...)
The point it is not of it being lighter (most likely it won't) or more
compact (most likely it will). The point of the barn door tracker is
that it's easy to manufacture with commonly available materials and
parts. If you were to drive the swivelling platform directly you'd have
essentially a RA drive and that would require, in its turn, quite lot
more work and sophisticated parts, and likely access to a lathe as
well.

Hmm, that figures- I hadn't actually worked out a design, I was just
thinking aloud!
James



  #5  
Old August 2nd 05, 06:52 PM
JamesB
external usenet poster
 
Posts: n/a
Default


"Robert Williams" wrote in message
news
Hi there James,

this is slightly OT, but have you considered an equatorial
driven head for a camera tripod. It uses a ball joint mounted
1/4" camera mounting mated to a synchronous motor driven
right ascension axis, and runs off 12 V DC (600rpm motor geared down
via a planetary gearbox to 1 rpd).

There is also a simple 'hinge' to adjust the polar axis and I've upgraded
it with a 6x30 finderscope with cross-hairs to act as a polar finder.

I have one (from Beacon Hill Telescopes, Beverly)
and it works a treat. I have done 5 minute exposures with very little star
trailing
(provided I take time to set up the polar axis accurately).
I've acquired a anti-rotating motor (from BHT) for southern
hemisphere use.

I can a pic if you are interested.


The one on this page?
http://www.beaconhilltelescopes.mcma...cessories.html

Pic could be interesting, to see whats-what. Get rid of the
"whodoesntlikespam" in my address if you mail it.

James


  #6  
Old August 2nd 05, 11:14 PM
John Knight
external usenet poster
 
Posts: n/a
Default

JamesB wrote:
Looking online at these types of mount for widefield. I have read plenty
about the fact that a simple drive will lead to errors as the angular rate
changes over time, and that a "double hinge" method is better.
What I was wondering is if anyone has ever tried driving the hinge mechanism
directly? Instead of the threaded rod, simply gear down the motor enough
(which would increase the torque) and drive the hinge directly at the right
speed?
I'm guessing I am missing something obvious here else I'd have found people
who have done it... is it too hard to get the right speed through gearing?
Or is there some other reason? If it could be made to work it would surely
produce a lighter and more compact mount.
James.


James,

I have made a few prototypes that adjust the speed of the drive to
overcome the changing angular rotation if you are interested. Simple
hardware - hard bit done in software.

http://home.btconnect.com/John-Knight/camplat.htm

JK
 




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Is the universe spatially infinite? dkomo Astronomy Misc 27 August 11th 04 01:39 AM
Looking for micro controller based barn door tracker URL Brian Reynolds Amateur Astronomy 12 January 30th 04 10:10 PM
UFO Activities from Biblical Times (Long Text) Kazmer Ujvarosy UK Astronomy 3 December 25th 03 11:41 PM
UFO Activities from Biblical Times (LONG TEXT) Kazmer Ujvarosy SETI 2 December 25th 03 08:33 PM
UFO Activities from Biblical Times Kazmer Ujvarosy Astronomy Misc 0 December 25th 03 06:21 AM


All times are GMT +1. The time now is 06:17 PM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004-2024 SpaceBanter.com.
The comments are property of their posters.