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RustyM

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About RustyM

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    Nebula

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    Texas
  1. Would narrow-band M1 work ? If so would a ~100MB zip via sendspace be ok ?
  2. You really nailed the depth ! Beautiful.
  3. Hi Zakalwe, You have an excellent first M42. Be very patient with your processing skills....it just takes time Your are off to an excellent start. Enjoy,
  4. Have you tried using a recent dark ?....might be better than no dark How many subs do you have ?....Using a median combine with high and low range rejection should clean most of the outliers....with enough subs Looks like some really good stuff is in there. I think the juice will be worth the squeeze.
  5. You might be pushing for a black background at the expense of the nebulous detail...could just be the JPEG (evil format) compression. You might consider extracting each color channel and working them separately. This will usually allow better control of the faint detail present in each color frame. A larger image with max JPEG quality would help the examination
  6. Tips, criticism, ideas, harsh language, dirty looks, et.al. are always welcome and always appreciated Excellent tip. Unfortunately, my PosAng is usually governed by guide star position. Ahhh....So always keep an eye on how you want the final framing ? I was thinking of a DSS image, NASA Sky View or the like, as the reference frame and using the star alignment tools in PixInsight to build each mosaic frame. Sound like a plan ? Thanks, Rusty.
  7. Okaaay....had you down for the 32" RCOS.... I'll make a note... "Kevin prefers SK 200P HEQ6 over RCOS."...check
  8. Some stuff on my list of useful things.... Sheet filters in different colors If typical red acetate filters don't work for you....everybody is slightly color blind in one form or another...or your computer monitor just doesn't get on with a given shade of red... "Gel" color filters used in theatrical lighting are an excellent option. Your local community/high school/college theatre can usually spare a sheet or two. Rosco has a large color selection. Gaff Tape : Like Duct Tape but cloth backed and won't leave a sticky mess behind when removed. Black for obvious reasons. White for labeling big, flexible (tarps, bags) or oddly shaped stuff...writing with a fat red Sharpie works best. Gaffer tape - Wikipedia, the free encyclopedia Glow Tape : Excellent for marking tripod legs, table edges, cars and other stuff you need to find/avoid in the dark. Also good for locating items that tend to wander off....like small children. Gerber Tool : The human sized Swiss Army Knife. If you can't fix it with a Gerber you probably shouldn't be messing with it. Gerber Gear (might not be considered inexpensive but worth a mention) Wire, string, rope : A must if you need to tie or tether something (or somebody) up, down, left, right or indifferent. Lighter, Matches, Blowtorch : You never know when you might need a little fire. Bug spray, bug spray, bug spray. First-Aid Kit : Because stuff happens. Extra water : Setting up and taking down all that gear can be more strenuous that you might think or be aware of at the time. Don't forget to bring the stuff you forgot to bring. Rusty.
  9. So.....Who is member 10,000 ?....and.... Do I have'ta get gifts for everybody ?
  10. Good point. Bearing and other mechanical slop can be a killer. Should the use of two cylinders mounted in opposition (pushing against each other slightly) be considered ? This would "pre-load" the compression and mechanical slop. An opposing gas shock (from a car hatch back, say) might be better...cheaper, simpler. Divide an Conquer. Always a sound strategy. Be bold and mighty forces will come to your aid. On parts and such...... I live in Dallas and work from home for a company based in Las Vegas (we also have a shop outside London). We do all our manufacturing in Vegas where we have a machine shop and an electrics/controls shop. I'm going to be working in Vegas for two plus months starting ~15 January. During that time I will have unlimited access to the shop and its tools. So....If we come up with some parts designs in the next few months I can make them There is a huge aerospace junkyard/surplus store in Los Angeles. They might have some useful goodies....valves, cylinders, etc. I might have a buddy that could go have a rummage or I can go myself while I'm in Vegas (only ~250 miles from Vegas). If we can find somebody in the Seattle area....there is the Boeing surplus store (never go there with a credit card or more cash than you are willing to part with). They might also have some good stuff at a good price. Cheers, Rusty.
  11. Nick....I love you, man. Most see things in the exact opposite way. When there are many variables that should be considered....the number is always higher than you think....The usual approach is to try and reduce the variables considered and solve the reduced set. While this is perceived as simplifying the problem. In reality the excluded variables still exist and will bring complexities that can seldom be resolved. Your super-simple method is vastly superior terms of results and violently more simple in implementation. The geek name for Nick's super-simple approach is: Closed-Loop. Warning: Geek Ramble: On Closed-loop motion control systems compensate for variables, like temperature, that introduce errors in how an actuator tracks a set-point....like position or velocity. Here's a classic example... A long time ago auto makes hit on a great idea: Cruise Control. The first implementations used throttle position as the set-point value; held steady when the driver flipped the cruise switch. Cool...works...better than nothing on a long trip....sorta. There are some obvious problems with this "open-loop" solution...The actual speed of the vehicle changes with changes in conditions...hills, wind, temperature, etc. and it wasn't long before a six year old girl, looking for relief from motion sickness induced by these constant changes in speed on long trips, wrote the automakers demanding a solution... "or else". In light of this veiled threat the automakers used the speedometer position as the set-point value and the throttle position as the control variable. In this "closed-loop" arrangement the actual position of the speedometer, sampled at some constant rate, is compared to the set-point value and the difference, the error, between them is used to adjust the throttle position. Thus, compensating for changes in external conditions that would otherwise cause changes in the vehicles speed. Cool, the little girl was pleased. The difference between the closed loop algorithm in your car's cruise control and the one that controls the gimbal positions of the Space Shuttle's three main engines ...the ones that hold the Shuttle on trajectory while compensating for all the external factors encountered in accelerating from zero at 4,400,000 lbs to 17,320 mph at 240,000 lbs... ? Cost. They perform the same function, use the same math and can be written in less than 50 lines of code. For the RA cylinder's position control a basic Proportional Integral Derivative (PID) loop should do nicely. It is robust, extend-able and amazingly simple. The PID loop math is executed at some constant rate....say 100 times a second (a 10ms sample rate the BlackFin will laugh at)....and looks about like this... error = desiredCylinderPosition - currentCylinderPosition; integral = integral + (error * sampleRate); derivative = (error - lastError) / sampleRate; commandToValve = (Kp * error) + (Ki * integral) + (Kd * derivative); lastError = error; Really. The three gain constants (gains)...Proportional Gain (Kp), Integral Gain (Ki) and Derivative Gain (Kd)... are determined during a "tuning" phase that would take place for each system. For most systems only Kp is needed with Ki and Kd left at zero. Large changes, like going from a 5lb to a 50lb OTA, will require different gains. Simple look up tables and self calibration can be used to automate gain changes with very little, if any, user intervention. General Rules of Thumbs* - The resolution of the position feedback should be 10 times greater than the maximum allowable error. i.e. If you must within 1cm of the desired position at all times the position feedback device should have a resolution of 1mm or better. - The frequency response of the valve should be at least 2 times the sample rate. i.e. For a 10ms sample rate the valve should be able to change the cylinder direction every 5ms. *Deciding to bend the rules is deciding to hit your thumb with a hammer.....you might miss....rarely. Geek Ramble: Off What is the schedule for the first prototype ? Rusty.
  12. Dude ! Really nice. Rich and Smooooth....... My wife had a look and wandered off mumbling something about needing chocolate. Ha is awesome. More please.
  13. EQMOSAIC looks like it will do the trick quite nicely Thanks Guys/Girls/Other your the best, Rusty.
  14. Hi Nick, I think your onto a Great Idea. The motion would be smooth, accurate and backlash free…like butter. (I love Hydraulics....one of my favorite methods for moving stuff.) Here is a bit of what I know of hydraulics and controls*. Ramble Warning: I'm just going to brain dump. You might want to leave now. Most of these notes go to "controllability" where many small errors can accumulate...often resulting in "uncontrollability" i.e. Tracking errors. - Fluids are incompressible....mostly. Hydraulic fluid will have ~2-3% entrained air that will give cylinders a very small bit of "softness". Obviously this becomes more pronounced has cylinder volume increases but it is always there. Hoses, pipes and plumbing all expand and contract as a function of temperature and pressure...all adding a bit more softness to the actuator.- Cylinders have slip-stick and they leak internally (by design). Cylinder pistons must both move and provide a seal between the rod and cap ends of the cylinder. In moving, a thin film of fluid must be allowed around the seal as a lubricant or the seal, O-rings, will be destroyed. In sealing, a tight fit is required to prevent pressure passing from one end of the cylinder to the other. Bit of a Catch-22. Some amount of “break-away” force will always be required to overcome the outward pressure of the piston-seal-cylinder relationship. For slow, smooth motion it is very important that the break-away force not be much greater than the force required to move the piston once in motion. Large force deltas will cause start/stop stuttering at low speeds and limit the minimum controllable speed of the actuator. Keeping the force delta low is a function of outward seal pressure…low outward pressure gives a lower minimum speed but also allows more pressure across the seal which adds more softness to the actuator…fun, fun. Oh…don’t forget the rod end seal….it has the same effect on performance…more fun.- Fluid flow (volume) controls actuator velocity. Flow is the control variable in hydraulic systems. Pressure and fluid velocity are seldom actively controlled, they are really just design parameters. This can be a little brain twisting….for example: Given a pump that supplies 1000psi to a valve that is used to control a 3” cylinder and a load of ~1413 lbs. then 200psi (1.5” x 1.5” x pi x psi) would be needed to move the load, therefore pressure in the cylinder would be 200psi. For the pressure in the cylinder to be 1000psi the load would need to be ~7068 lbs. i.e. You can only do as much work as there is work to do…no more, no less. So…what happens with the extra 800psi of energy the pump is producing ? It gets dumped via a pressure relief valve that is set at 1000psi (also producing heat and a bunch of noise). Now here is the important bit: The valve controls flow by changing the size of an orifice between two ports: P for the pump side port and A for the cylinder side port. So we have 1000psi at P and 200psi at A. This give us a pressure across the valve, P - A, of 800psi (deltaP). It is the deltaP that determines the volume of fluid that will flow across a given orifice in a given amount of time… not the size of the orifice itself. Temperature induced fluid viscosity changes will also directly impact flow across a given orifice (as the night gets cooler less fluid will flow).As the speed of the actuator is in direct proportion to this flow; Flow ends up being the primary control variable. You’re killing me…why is this important ? Good question….For the actuator to move the mount in RA a linkage will be required to translate the cylinders linear motion into an elliptical motion. This linkage translation will cause the load on the actuator to be constantly changing. When the load changes the deltaP changes. When the deltaP changes the flow across the valve changes. When the flow across the valve changes the speed of the actuator changes. So…If the actuator needs to travel at a precise rate and the load variations can never be zero: Control of the valve needs to be fine grained both in orifice sizing and frequency response. It will take very little load change for minor oscillations to develop…. Resulting in same type of tracking errors you get with gear driven systems. If you like we can get into closed-loop control and the like at another time... Assuming my insane ramblings don't get me excommunicated first. Ramble Off The BlackFin with a fast valve and high resolution position feedback should handle all but the most glaring hydro-mechanical issues with ease....Probably run multiple rigs, handle temperature control and make coffee (or tea) without breaking a sweat. Again, Great Idea. I'd love to assist in anyway you like. Rusty. *I design and build software and hardware for multi-axis motion control systems for the Theatre...Broadway, West End, Las Vegas… From 35ft tall, 60ft wing-span, 24-axis hydro-mechanical Dragons to single axis electric curtains controls. I can’t believe they pay me to play with the toys.
  15. RustyM

    m31

    Very nice indeed. Dust lane detail is awesome ! More please, Rusty.
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