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Re: Steel worms. Should I change them?
Ok. I have a short anecdote. I attended a hospital management retreat a few years ago.? One of the hospital board members and I chatted.? She said she was a relative of Murphy.? The Murphy.?? She said he (Capt Murphy) was in the military and his job was to gather the body parts of the test dummies that were blown apart during initial phases of the space race: the rocket sled tests.? That was to determine what G forces the human astronauts (or their test dummies anyway) could withstand during a rocket launch.? I imagine the parts were scattered quite a distance.? ? He had to give a report on his work at a meeting and he noted that anything that can go wrong will go wrong at the worst possible time.? The saying stuck, as they say.? Murphy's Law was born.?? Ironically, the town I live in is now called Sunnyvale.? That is a very idealistic name.? If you go to the main park, there is a stele monument to Murphy....a different Murphy.? For Sunnyvale was once known as the town of Murphy...once Murphy's farm.? ? No wonder my astronomy endeavors have trouble! Best, Michael ?? On Sat, May 29, 2021, 1:34 PM Bob Redding <bob.redding@...> wrote:
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Re: Steel worms. Should I change them?
I guess the last two posts better phrased my question and gave me the answer I was looking for.? I understand Murphy's Law and personally I think that Murphy was an optimist.
I really have two goals which both lead to the same place.? I want the best PE I han achieve which will lead to the best image shooting available from my mount.? The resultant images are, of course up to me. Thanks to all.? I shall proceed slowly and just record the PE for each change over time. |
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Re: Steel worms. Should I change them?
It has been a long time since I did that work on my first CG11, but yes...the brass were better.? I can't recall exactly what my original PE was on the steel one that came with the (Celestron G11 or CG11).? I think the initial PE was about 5-8 arcsec RMS, so about 15-20 arcsec peak to peak.?? That number seems high by today's standards, yet these early mounts were not optimized for astro photography, but used for visual...star hopping.? That's why the slippery plastic clutch disks were considered a good feature.? Now you would not want that.? (I make high friction clutch disks for these mounts so if interested contact me).? That CG11 is now tested at 1 arcsec RMS or about 2.8 arcsec Peak to peak.? It was not all from the worm...I also changed to these: ? Long original style OPW ? ABEC-7 quality R4ZZ RA worm bearings? ? Single Belleville R4 spring behind far worm bearing? ? (Losmandy gearbox...was later changed to McLennan 25:1 gearbox) I also similarly modified another G11 with approximately equal or better results.? I've got a GM8 at about 1.6 arcsec RMS.? See attached reports.? I'm optimizing a G11T RA drive now with a different system (belt drive suggested by Allen Ruckle).? That's at 1.77 arcsec RMS so I'm still testing drive options, but the stars in autoguiding are round.?? ?? There is no sense chasing perfection if your present mount does what you want.? If you have a steel RA worm (they are magnetic, the brass ones are not) and it gives you good images, stay with it.? No sense spending money for no gain. But if your system is oscillating in RA and the oscillation has a period of 240 seconds, then suspect your Oldham coupler alignment, and your RA worm.? There are other possible oscillations: the worm balls can get pinched, and the gearbox can be faulty.?? I believe you really must test the RA drive using only star tracking and not by looking at the autoguiding signals.? One can always blame the autoguiding settings and this leads to madness...you will never come to a solid conclusion.? You must remove autoguiding from the analysis to find believable data on the RA drive components itself. See the attached reports for a way to do this.?? All the best, Michael On Sat, May 29, 2021, 10:03 AM wa1vta01452 <loeblt@...> wrote: Michael, when you tested the brass worms did you find a significant difference between them in PE? |
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New G11G and bad guiding first night: Need advice for gathering data tonight.
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Hello, Got a new Losmandy g11 and seems to have bad guiding right from the box or I'm doing something really stupid.? Did the Wizard set up, CAL and GA and at DEC 0.? Started guiding and WOW the RA was way bad.? Gave up for the night after a little while and started to work on perfecting back focus and tilt, that's why the choppy log later.? Later on (See section 21) I looked at the Frequency Analysis and I'm freaking out seeing a huge spike at 76 Seconds.? Clear skies tonight so I'm going out and redoing everything and just try to work on running PHD2. Maybe just do some really long GA runs for data.? Don't want to touch worms or anything, it should be set correctly from the start and I don't want mess anything up.
Any Tips would be appreciated. Thanks.
David Malanick
Losmandy G11 (with Losmandy Power Supply)
Orion EON 115
ASI 174 guide camera and QHY OAG
Direct connect through Ethernet to laptop.
P.S.? The? weather was a tad windy at times, settled later and temp was 44F. Don't know how much weather affects it.? Equipment acclimated before guiding for 1.5 hours. |
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Re: Steel worms. Should I change them?
I can't exactly answer your question ...only relate my own experience.? You might have the world's best steel worm, and you might buy the world's worst brass worm.? That Murphy's Law in action.?? It is the case that each worm has its own PE from the way it was cut in the precision lathe that made it.? You will only tell the PE of that steel worm by measuring it...tracking a star over about 45 minutes, starting at the intersection of the celestial meridian and equator.?? For that star tracking log, I use the free program PHD2, allow it to calibrate E, W,N,S, then turn off guide pulses (you will find a checkbox under the Brain icon).? I then use the free program PECprep.exe, downloaded from the EQMOD group's software on SourceForge.? Then select G11 (or GM8, or Titan) from the Mount list, import your PHD2 log file, and press Autofilter.? Out pops your PE RMS and Peak to Peak value. Then you swap in a different worm and run that test again.? Is it better?? I tried my existing steel RA worm, my existing steel DEC worm, and several new precision brass worms, until I found the best of the worms for the RA.? The lowest of the ones I tried was one of the new brass ones. The PE is not related to the smoothness of the worm surface.? A worm can be smooth and still have a high PE, or it can have a low PE and have a rough surface finish.? Some people have used a high speed electric drill, inserted a 1/4 inch rod, into a rubber hose like auto gas line then connected to the 1/4 inch worm shaft, and used lapping compound to polish their worm against the ring gear teeth.? That can give less surface roughness and might improve very fine fast vibration of the ring gear, but it can't affect the worm PE.? The PE is the variation of the worm thread all the way around the worm, not anything microscopic.?? Investigation of the worm to ring gear friction shows the lubrication there is also critical to reduce "chatter" vibration of the ring gear.? The specs, and experience, of using the complex CRC Brake and Caliper Grease show it tops the alternatives like Superlube and ArcticJetlube.? The key tests to look at are the 4-ball scar length (lowest is best) and Timken weight (highest is best).? I could feel residual chatter vibration on my G11T worm using only Superlube, but that vibration was eliminated using the CRC grease. I didn't expect that outcome...I thought the two lubes were going to have the same result. The mounting of the worm bearings also matters in reducing PE oscillations, because the worm bearings have small balls and small races.? You want those bearings to line up perfectly with the worm axle.? How can it be done?? The oldest mounts had 2 worm blocks independently bolted down with 1 bolt underneath.? If a block is not lined up, it's bearing balls can get pinched in a tight spot...there are 8 balls and they take a certain time to roll into the pinch point.? So Losmandy created a metal channel called the One Piece Worm (OPW) assembly to hold those two blocks in line.?? But what if the bottom or side of a block is not absolutely perfectly aligned with it's worm bearing cylinder? It was thought that matching the block sides alone would line up the bearings.? But recent investigations by Allan Fang showed that the alignment (measured by the PE test) could be improved by "floating" the far bearing on a special sized Belleville spring.? Then the inside and the outside of that bearing self-centered on the worm axle.?? This stuff is discussed in a PDF document I wrote some years ago.? It needs to be updated with the latest information.? If interested, it is attached... Best regards, Michael ?? On Fri, May 28, 2021, 5:29 PM Pete <pete.ingram@...> wrote: Thanks Michael.? So I get that the brass worm is the current, and probably the best worm but, my steel ones are well run in and are probably as well mated to their wheels as can be after 19 years of running together.? |
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Re: Steel worms. Should I change them?
Thanks Michael.? So I get that the brass worm is the current, and probably the best worm but, my steel ones are well run in and are probably as well mated to their wheels as can be after 19 years of running together.?
Bearing changes aside, what is the advantage of just putting in new brass worms please? Thanks Pete? ? |
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Re: next up: polar alignment tutorial
As?Michael says, phd2 drift align works great -- that's what I use. I can't see Polaris from my yard. Now for aligning with the sun. I do this by making a tripod locator in the yard. Align the mount at night, and put it back in the exact same position during the day. It will still be aligned as long as you left the tripod legs and mount polar adjustments the same.?
Jamie |
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Re: next up: polar alignment tutorial
Good question... In daytime, the trouble is that the sun's path is not on the perfectly same path as the Earth's rotation, as the sun will appear to be moving higher or lower in the sky during the seasons.?? The sun has only got about the same path... same elevation ... at a solstice, either winter or summer....that moment of those 2 days.?? Likewise you cannot use the moon's path either for accurate daytime polar alignment.? But your other question...how to polar align if your view of Polaris is blocked...there is an answer: You use a Drift alignment.? That uses your tracking of a star at 90 degrees to either pole. _____ The only problem with drift align is that if your initial RA axis is very far off, it's hard to tell if you are getting lower drift from minor adjustments of AZ or EL (elevation).? You would need coarse adjustments to see an improvement or deterioration.? If you are already pretty close, you can perfect the polar alignment by small adjustments to AZ and EL using Drift alignment.? Therefore it helps to use a polar scope or Polemaster first, then follow by Drift alignment.?? The free PHD2 tool has very useful methods in it's Tool menu selection to aid in drift alignment.? To give those a try, you must have an autoguide camera available for PHD2 to track a star in your scope.?? Have fun, Michael On Thu, May 27, 2021, 10:58 AM <t.bottoni@...> wrote: Any thoughts on including how to polar align during the day for solar use or at night if you don't have a view of Polaris? |
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Re: Camera Tilt
One last update just in case any crickets are listening. -- I was able to resolve the issue tonight. Starizona took a look at images of my corrector plate alignment and said it looked good, so I wasn't considering that for a while. I decided to try and adjust it, and now I've got it almost perfectly aligned. Yay!?
Jamie |
Michael Herman
Pete
David Malanick
Jamie Amendolagine