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 Another automation idea 
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Joined: Tue Oct 14, 2008 12:44 pm
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Post Another automation idea
It seems an ideal program would both control the meade/milapse through the 497, and also the camera.

Has anyone tried using applescript or a windows scripting language?

The ideal movement of the meade would be for the motion to stop while the photo taken. Is this correct, or am I missing some logic?

I see applescript sending the appropriate text move command to the 497, then using the camera control program to take the photo. In my case that program would be Canon camera utility. But it could be done with any camera control program. A front end like what Thomas is working on could do the calculations.

The benefits would be:
- coordination between movement and shutter release
- camera control without touching the camera
- the ability to see and adjust exposure in more difficult situations.

The idea is that the program will run automatically, but can be tweaked while running if necessary. For example, changing ISO and shutter.

Comments?


Wed Oct 22, 2008 7:13 am
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Post Re: Another automation idea
dcmiller wrote:
The ideal movement of the meade would be for the motion to stop while the photo taken. Is this correct, or am I missing some logic?


You'll need to account for load when doing movement timings.

That is, generally speaking, if I want to move 100 degrees over 1000 shots, I have to move 0.1 degrees between each shot. In the simple world, I can say that at max speed (to simplify the model, we'll state there is no need to adjust speed from the max speed) and max efficiency I can move at 200 deg/sec. So, I'd need to run the motor for 1/20th second. This works fine, until we account for the fact that speed will be modified by load torque - so that the speed it moves slows down as the load torque (weight of camera) increases beyond max efficiency. You would need to tune it to a particular load weight. This would also have to be an empirical activity given that the motors used in it are unlikely to be designed to the point that they have a guaranteed speed graph over all load ratings. (That is, these aren't $200 motors and are likely to vary from unit to unit.)

You would be able to get close, but not exact - and rarely repeatable. That may be good enough for most uses though.

I've experienced similar issues with the stepper motors in my project when doing movements > 1/8 step. That not all micro-steps complete as required, although I've found the problem largely coming from making the steps at a fixed speed, rather than ramping speed (e.g. 200uSec between steps fixed, instead of going from 500uSec to 200uSec across the steps). It doesn't become that obvious, until you put it all together and there's the occasionally jerky movement.

!c


Wed Oct 22, 2008 8:23 am
Post Re: Another automation idea
First and foremost 'pulsing' the Meade head has to be tested... If you try it in an anecdotal manner by pressing and releasing a direction button say for a count of 2 seconds @ 16x sidereal you will hear the motors 'settling in' to their set speed. This is where my concern rises... Will the stop start produce accurate repeatable movements? hard to say. I doubt it though.

At the end of the day a pause for the shutter is only 'really' required beyond say 2 sec. exposures and even at that slowing the speed down to compensate 'can' work. The big exception comes when your doing stars and want those perfect points in the sky... (unless your tracking the stars! ;) ) Now... can you get motion blur under say 1/30"? sure. Again this is where slowing the speed to compensate comes into play. Are you 'in theory' creating motion blur by not pausing? sure. but... remember hand held shots are subject to the same theoretical critique.


Wed Oct 22, 2008 8:31 am

Joined: Tue Oct 14, 2008 12:44 pm
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Post Re: Another automation idea
How about the mumford? Can it be both stepped in small increments and computer controlled? I don't mind doing the software, but I would like to buy finished hardware.

Thinking about it more, it would seem I would want to move the mount at the slowest speed, time permitting. That would max the run time. It seems to me that these devices would need to be extremely accurate for Goto to work. But I don't see how a $130 device can be accurate.
I see the 497 works with the LXD75 also. So I could try that.
Instead of just running the motor, perhaps a GOTO would work. The 497 may take into account starting movements of the motor.


Wed Oct 22, 2008 9:00 am
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Post Re: Another automation idea
dcmiller wrote:
How about the mumford?


It's ready to go out of the box... Camera and motion are coordinated via the 'time machine'

dcmiller wrote:
I see the 497 works with the LXD75 also. So I could try that.


It's a serious mount at 40+ pounds and very smooth. Designed for astro-photography so it's the real deal.


Wed Oct 22, 2008 10:05 am
Post Re: Another automation idea
dcmiller wrote:
How about the mumford? Can it be both stepped in small increments and computer controlled? I don't mind doing the software, but I would like to buy finished hardware.

Thinking about it more, it would seem I would want to move the mount at the slowest speed, time permitting. That would max the run time. It seems to me that these devices would need to be extremely accurate for Goto to work. But I don't see how a $130 device can be accurate.
I see the 497 works with the LXD75 also. So I could try that.
Instead of just running the motor, perhaps a GOTO would work. The 497 may take into account starting movements of the motor.


Well, yes, the mumford operates (afaik) exactly like we've been discussing, movement can happen between shots, either before or after shooting. But, if you're getting into the nitty-gritty of it, you can get the same performance at a much lower price. Obviously, it would require some time in the shop and plenty of time writing code, but if you enjoy those things - it can be done at bargain-basement prices.

I don't know if his allows driving from a computer, but lets be honest - steppers are steppers. (Of course, there are bi-polar and uni-polar steppers, but what the hey...) You could either buy his and run it directly via an easydriver and an arduino (which could hook up via usb/serial to a computer), or you could go straight to sherline, buy theirs for $270 and buy a stepper on ebay for $20. There are a lot of less expensive options for rotary tables if you plan to write the control logic yourself.

!c


Wed Oct 22, 2008 10:20 am

Joined: Tue Oct 14, 2008 12:44 pm
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Post Re: Another automation idea
I don't want to write the control logic at a low level. I want to send commands to a intelligent device like the 497. i.e. what to do, not how to do it.

I want to do that from a laptop because I would like to also use a camera control program. The camera control programs are getting sophisticated with Live View.


Wed Oct 22, 2008 10:47 am
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Post Re: Another automation idea
Pulsing the Orion telescope mounts off and on should not be a problem. They used pulsed motor controls, so there is no start up etc. Switching the power to the motor control on and off at say 1 second intervals would be easy by just interrupting the DC supply.

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Wed Oct 22, 2008 11:32 am
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Post Re: Another automation idea
I'd have to agree, that if you have a solid rig, there is not much need for stopping motion between shots under most circumstances.
In fact, I would even be inclined to say the motion could help in making the movement look more natural in a lot of cases.
I remember back when The Empire Strikes Back came out they made a big deal about using "Go Motion" instead of "Stop Motion" where they intentionally blurred the moving objects to make the movements look more real and flowing during playback to the naked eye.

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Wed Oct 22, 2008 12:07 pm
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Post Re: Another automation idea
I do frequently shoot still photography at night. Not much TL so far. I would like a mount that can move to take out star trails. I does the DS2000 do this, or do I need something like the LXD75?

I have the faster Canon cameras, but still would like to go out to 2 minutes on exposure. Many of the Canon 1.2/1.4 lenses get very sharp at f2. As far as power, I would rather deal with a laptop than make mistakes. But if I'm backpacking I'm not going to bring a computer. At this point I'm exploring an ideal (for me) interface and setup. That includes knowing for sure what I'm shooting, and having the mounts to do what I want as far as motion.

Anthony, that's an interesting point about motion. I know still photographers tend to be unnecessarily critical of the quality of single video frames.


Wed Oct 22, 2008 12:36 pm
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Post Re: Another automation idea
tmophoto wrote:
......................
if you take any still photos with the ground in the shots the stars become sharp and the ground gets blurred

t


Since I blend exposures anyway (sky and ground) I would have everything sharp. (Taking the ground shot without camera tracking)


Wed Oct 22, 2008 12:56 pm
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Joined: Wed Oct 01, 2008 8:40 pm
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Location: Montréal, Canada
Post Re: Another automation idea
dcmiller wrote:
I do frequently shoot still photography at night. Not much TL so far. I would like a mount that can move to take out star trails. I does the DS2000 do this, or do I need something like the LXD75?

I have the faster Canon cameras, but still would like to go out to 2 minutes on exposure. Many of the Canon 1.2/1.4 lenses get very sharp at f2. As far as power, I would rather deal with a laptop than make mistakes. But if I'm backpacking I'm not going to bring a computer. At this point I'm exploring an ideal (for me) interface and setup. That includes knowing for sure what I'm shooting, and having the mounts to do what I want as far as motion.

Anthony, that's an interesting point about motion. I know still photographers tend to be unnecessarily critical of the quality of single video frames.

If it's just to get rid of star trails in long astrophoto shots, what you need is the AstroTrac 320X. Pricy, but very portable: http://www.kendrickastro.com/astro/mt_astrotrac.html. You just need 12V (8 AA batteries) to power it. I have the former model, the 320 (lot cheaper!), and I'm very satisfied. Even simpler (and way cheaper, something like $10 in parts) and easier to use is a barndoor platform. (instructions are for the Northern hemisphere) 2 boards, 12-13 inches long, hinges on left side, a hole with a 1/4-20 T-nut at exactly 11 7/16" from the center of the hinges, a 1/4-20 4" long bolt passing through it that will push up the upper board when you turn the bolt clockwise. You can cut a cross-shaped piece of wood and attach it to he head of the bolt. The idea is to turn the bolt at 1rpm, or if you are using a normal or wide angle lens, 1/4 turn every 15 seconds (the reason for the cross-shaped head, easier to operate). Attach a ball head to the top board and glue a large drinking straw on the hinged side (left side). Mount it on a tripod, aim the left side to the Pole star until you see it looking through the straw. Lock the tripod, aim the camera, and voilà! You're in business! Here is an example of a shot, taken with this barndoor platform. 35mm camera, 135mm lens, 2 min. exposure:


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Wed Oct 22, 2008 1:09 pm
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Post Re: Another automation idea
dcmiller wrote:
I would like a mount that can move to take out star trails. .


If all you want to do is take out star trails on a wide shot, this is about the cheapest option I've seen...
at Amazon

You need the drive motor too listed on the same page.

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Wed Oct 22, 2008 4:25 pm
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Post Re: Another automation idea
Antz wrote:
dcmiller wrote:
I would like a mount that can move to take out star trails. .


If all you want to do is take out star trails on a wide shot, this is about the cheapest option I've seen...
at Amazon

You need the drive motor too listed on the same page.

I agree with you that the Orion is a great astrophoto head at an unbeatable price. But its german equatorial design (involving the use of a counterweight) makes it a heavy solution: 10lbs 5oz head alone, add a few pounds with motor, controler and batteries. Not optimal if you are backpacking or need to travel light (for example, some interior airlines and chartered flights have strict weight limitations). The very expensive AstroTrac is 2.5 lbs, and the very cheap barndoor is less than 2 lbs. If you don't need to make multiple exposures (for stacking), you don't need a motorized head, just something that will track for 2 to 5 minutes at a time (longer than that requires precise polar alignment and guided exposure). The barndoor is just great for that. No batteries needed, super simple to make and use, very light and perfect for backpacking. But again, if weight is not an issue, the Orion is surely the way to go! ;)


Wed Oct 22, 2008 5:32 pm
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Post Re: Another automation idea
I haven't used one of these myself, but I know a guy who has one, he does not use the weights when he is just using his SLR, so the total weight is not very much, not sure just how much exactly, but a lot less than posted in the specs.

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Wed Oct 22, 2008 7:09 pm
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Post Re: Another automation idea
Antz wrote:
I haven't used one of these myself, but I know a guy who has one, he does not use the weights when he is just using his SLR, so the total weight is not very much, not sure just how much exactly, but a lot less than posted in the specs.

Hmmm, not a good idea. A german equatorial head performs correctly only if well balanced. Even with a small ball head, it is a lever arm long enough so a small DSLR will exert a great force on the right ascension axis (the tracking axis). Bad for tracking accuracy. Bad for the gears too, in the long term... But let me think, a good way to balance it would be to attach another camera on the counterweight bar instead of the actual counterweight... Wow, 2 tracking cameras with one tiny mount! ;)


Wed Oct 22, 2008 7:29 pm
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