|
|
Thread Tools | Display Modes |
#1
|
|||
|
|||
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
|
|||
|
|||
(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
|
|||
|
|||
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
|
|||
|
|||
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
|
|||
|
|||
"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
|
|||
|
|||
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 | |
|
|
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 09:10 PM |
UFO Activities from Biblical Times (Long Text) | Kazmer Ujvarosy | UK Astronomy | 3 | December 25th 03 10:41 PM |
UFO Activities from Biblical Times (LONG TEXT) | Kazmer Ujvarosy | SETI | 2 | December 25th 03 07:33 PM |
UFO Activities from Biblical Times | Kazmer Ujvarosy | Astronomy Misc | 0 | December 25th 03 05:21 AM |