Re: Polar Alignment Routine
Adjusting the Polar Alignment Reticle with Polar Scope Align Pro
?I have been working on fine tuning my PA process with the Losmandy Polar Scope and am using Polar Scope Align Pro with the Kenko reticle. My starting setup as I begin this process is RA pointed north, CWD position. I have been using my watch display (synced to my iPhone) to determine the setting of the reticle, and rotating the reticle to match my watch orientation, and going from there. But Tim says (post?#66181 )?the reticle can be find tuned (¡°adjusted¡±). I thought I would try it, but found myself confused.
Picking up Tim¡¯s guidance on adjusting the PS reticle, he writes:
There¡¯s is an iOS app called ¡°Polar Scope Align Pro¡± ...??Having done this, rotate the scope in RA until the Polaris line in the reticle is straight up/down (verticle). You can adjust the altitude knob on the mount to make sure Polaris glides up and down along this line.?
The?'scope'?in this sentence refers to the polar scope, not the OTA, correct? Actually, to do a PA with the polar scope, I don¡¯t need the OTA mounted at all, correct? If I ¡®rotate the?(polar)?²õ³¦´Ç±è±ð¡¯, I assume this means rotating it *within the RA axis housing*, not rotating the entire RA axis, correct?
Next, in the app, tap?the ¡°Set zero position¡± and a sub-menu asks you to read the current RA value on the ²õ³¦´Ç±è±ð¡¯s setting circle. ? ?Enter the value and click ¡®done¡¯. ?
This confuses me, b/c if I have rotated the polar scope within its housing, I have not changed the ¡°RA value on the ²õ³¦´Ç±è±ð¡¯s setting circle¡± at all. It has stayed the same, and was set when I started with the mount in the CWD position.??Is this correct?
Back on the main screen it will now provide a ¡°Zero Adjusted¡± RA time. ?Rotate the mount in RA to the zero-adjusted value (watching the setting circle on the mount). ?
"Rotate the mount in RA" now means rotating the entire RA axis, housing, Polar Scope and all, either by hand or with the HC buttons, correct?
The?¡°Zero Adjusted¡± RA time?on the setting circles does not seem clear to me either. There are two scales of 24 hours on top of each other, counting in different directions. Which one is the proper one to calibrate?
That¡¯s it¡ your polar alignment reticle is now *perfectly* adjusted.?
But it does not match the orientation on my watch face anymore, because I just 'adjusted' it, does it?
I may be *way confused* on all this, and I¡¯d be glad for some clarity!!
Thanks,
Geoff
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Re: I put a G11 gearbox in the freezer...
I have a newer G11G, up here in Michigan and was getting a lot of DEC stall warnings as the temperature got down in the single digits. I was able to stop them that night by increasing the stall limits. The next day I took off the worm cover and cleaned off the worm and lubricated with some Mobil 1 0W-20 while driving the DEC axis. Seems better.?
Sometimes if I haven't run the mount for a while I also use a program I wrote to exercise both axis.
Rick?
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Re: Best Way To Raise GM811G Saddle Height?
On Mon, Mar 1, 2021 at 02:34 PM, Jim Waters wrote:
That's the issue.? My 1/4-20 Cap Screws are?hardened steel and my hacksaw can't get through it.
No, your hacksaw wouldn't cut hardened bolts. But you can cut them with a cut-off wheel, or grind away the excess with a grinding wheel. The bolt is going to get real/red hot. so quench often and go slow. If you go in 1/4" plate sizes, you should be able to use 1/4" bolt lengths. Typically bolts grow in 1/16, 1/8, or 1/4" lengths. You might find something at or Lowe's, or for certain at
When the chips are down, McMaster-Carr has always come through for me. But you have to make sure what you order is what you need. But you can custom build your spacing. ? -- SonnyE (I suggest viewed in full screen)
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Re: Best Way To Raise GM811G Saddle Height?
Hi John - I am looking for a DEC extension.
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Re: Best Way To Raise GM811G Saddle Height?
Jim,
Not sure if you are just talking about an RA extension. I pulled these pieces out of my G11 when I put in the break-apart RA EXT kit. I am sure HGM still sells these. They are 4 7/8 in. in diameter and add about 2 in. to the RA assembly.
Regards,
John
P.S. I was just comparing the G8 and G11 on the Losmandy site and it appears the G8s have a 2 bolt RA attachment and the G11 is a 4 bolt, so there may not be a matching part.
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Re: Used GM-8 Guiding Help
Hi Brian,
Yea that's how I view the logs, tonight started clear but after an hour or so I would get an occasional cloud drifting through the FOV. A clearer night would be nice but it still seems like I'm fighting the same problem whatever it is
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Re: Used GM-8 Guiding Help
Nick just curious have you looked at these logs in PHD Log Viewer?
they are pretty crazy, and shows a lot of lost guidestar problems and poor guidestar SNR
Update
So I went ahead with the changes - enlarged the gearbox holes and aligned the shafts very well, worked with a much better polar alignment, adjusted worms to be on the looser side, they could spin very freely, and also played with the RA divisor in separate logs.
Derek, I'm all ears, I've been going with default settings based on various advice to allow the logs to show a good baseline and applying guiding assistant recommendations.
Michael, I was thinking the worm was possibly sticking so I adjusted it to be more loose (end of counterweight shaft would have a deflection of 1-2mm). I'm not sure where the axis would stick? I did a full cleaning and re-greasing of the mount and the needle bearings move very freely, I suppose I could do it again though. This is an old used mount, I did replace the worm bearings with new ones and they rotate nice and smooth.
Wish I had more exciting news, more of the same unfortunately and started getting some clouds toward the end of tonight. I'm really not sure why RA is all on one side with the occasional bounce back. Attached are logs of guiding assistant and guiding at default settings, the first 01 and 02 are with sidereal rate, next logs 03 and 04 are using an RA divisor of 56115 in hopes of slowing down the mount a little to bring the RA graph down. Didn't seem to help too much.
Would bumping up guide speed to 0.8x help? Any other ideas? Maybe I'll try re-installing ascom/phd2 etc but everything seems to communicate fine. Just seems weird, I know the mount isnt perfect but seems like PHD2 should be able to guide it a little better, something just isnt clicking
-- Brian?
Brian Valente portfolio
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Re: Used GM-8 Guiding Help
Update
So I went ahead with the changes - enlarged the gearbox holes and aligned the shafts very well, worked with a much better polar alignment, adjusted worms to be on the looser side, they could spin very freely, and also played with the RA divisor in separate logs.
Derek, I'm all ears, I've been going with default settings based on various advice to allow the logs to show a good baseline and applying guiding assistant recommendations.
Michael, I was thinking the worm was possibly sticking so I adjusted it to be more loose (end of counterweight shaft would have a deflection of 1-2mm). I'm not sure where the axis would stick? I did a full cleaning and re-greasing of the mount and the needle bearings move very freely, I suppose I could do it again though. This is an old used mount, I did replace the worm bearings with new ones and they rotate nice and smooth.
Wish I had more exciting news, more of the same unfortunately and started getting some clouds toward the end of tonight. I'm really not sure why RA is all on one side with the occasional bounce back. Attached are logs of guiding assistant and guiding at default settings, the first 01 and 02 are with sidereal rate, next logs 03 and 04 are using an RA divisor of 56115 in hopes of slowing down the mount a little to bring the RA graph down. Didn't seem to help too much.
Would bumping up guide speed to 0.8x help? Any other ideas? Maybe I'll try re-installing ascom/phd2 etc but everything seems to communicate fine. Just seems weird, I know the mount isnt perfect but seems like PHD2 should be able to guide it a little better, something just isnt clicking
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Re: Guiding without Gemini
Liam,
Keep in mind that G11 is the easiest mount for OnStep conversion. GM8 is a little more complex, but also not hard. Look for reverse worm design for GM8 on onstep forum, it seems to be the simplest method.
There are several options for building OnStep which require very little soldering:?
1. MKS Gen L v1
2. MKS Gen L v2
2. CNC shield + ESP32
I have 4 mounts converted using MKS Gen L? 1 - it is very cheap and easy, and works fairly fast despite old processor.
The biggest challenge for me was to reduce the diameter of the coupler because I do not have easy access to a lathe.
If you have a challenge programming board, let me know, I have some spare boards which I can program for you and provide at a fair price.
Alex
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Re: Help with interpreting PHD2 log on G11
Magnus,
One possible source of the problem may be that your eastward weight bias is insufficient and your RA gears may be "floating" in a wind breeze or gust. I personally have found that the best way to establish proper eastward weight bias is to do short live exposures and nudge the OTA with my hand to see if stars move in live view. I have found that arbitrary eastward weight bias (wherein balance just begins to tip eastward) is more often than not inadequate for real world wind conditions.I suggest that you try increasing eastward weight bias to a point where you estimate wind gusts will no longer make your gears float by applying force on the OTA with your hand that you estimate will be sufficient given the sail area of your setup. Pretend that the pressure from your hand is a gust of wind and from there determine how much balance offset actually works. Do this for both RA and DEC. For DEC my weight bias is tail heavy.
The motors and gears will have to work a little harder but they can take it. I do not think it is a problem at all. Just make sure that your power source is sufficient. Note that the power source offered at the Losmandy site is 15v 4.3amps.
I too have a C11 RASA on a G11 and get similar wild spikes. Increasing eastward wight bias eliminated it.
Hope this works for you too.
John
On Tuesday, March 2, 2021, 8:35:32 AM GMT+8, Alexander Varakin <avarakin@...> wrote:
Looks like you took this graph with PEC enabled and I don't think you will be seeing the expected frequencies in that case.
Can you share the freq analysis without PEC and guiding?
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Re: Typical Guided Performance of GM8G, GM811G, and G11
Liam,
I have both G11 and GM8. I use G11 with 10" RC @2000mm FL in my home observatory and it is great.
On the other hand, I bought GM8 specifically for travel imaging due to its lower weight.?
I tried using it with 8" RC but was not very happy with it, so I switched to 750mm refractor and it works very well for this payload with guiding.
Here are some results:
https://www.astrobin.com/nn5su1/?nc=user
Alex
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Re: Help with interpreting PHD2 log on G11
Looks like you took this graph with PEC enabled and I don't think you will be seeing the expected frequencies in that case.
Can you share the freq analysis without PEC and guiding?
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Re: Best Way To Raise GM811G Saddle Height?
On Mon, Mar 1, 2021 at 03:26 PM, Michael Herman wrote:
If it's just a matter of the bolt lengths, just get longer stainless steel 1/4-20 bolts
That's the issue.? My 1/4-20 Cap Screws are?hardened steel and my hacksaw can't get through it.
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Re: Best Way To Raise GM811G Saddle Height?
If it's just a matter of the bolt lengths, just get longer stainless steel 1/4-20 bolts...(at least that's the threads on my GM8 DEC).
?If the bolts are too long, you cut them to the correct length with a hacksaw and file the ends.? The dovetail mounting threads are pretty shallow.??
Best,
What¡¯s the best way to raise the height of my ADM Dovetail Saddle?? I would like more clearance between the saddle and the motors.? I am currently using a 3¡± round 1/2" thick aluminum stock but the screw lengths are not ideal for attaching the saddle.? They are either too short or long.
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Best Way To Raise GM811G Saddle Height?
What¡¯s the best way to raise the height of my ADM Dovetail Saddle?? I would like more clearance between the saddle and the motors.? I am currently using a 3¡± round 1/2" thick aluminum stock but the screw lengths are not ideal for attaching the saddle.? They are either too short or long.
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Re: Used GM-8 Guiding Help
I
have lots of thoughts about your PHD2 settings..
?
Derek
?
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From: [email protected] [mailto:[email protected]] On Behalf Of Nick
Sent: Sunday, February 28, 2021
7:59 PM
To: [email protected]
Subject: Re: [Losmandy_users_io]
Used GM-8 Guiding Help
?
Update
So I received the new gearboxes and installed on RA and Dec. I was hopeful
since they seemed to have a little less play in them compared to the ones I've
been using. I still can't shake this bad guiding, not sure if anyone has other
thoughts? I attached a few of tonight's guide logs, but looks like more of the
same. Everyone says its a mechanical issue, I just have to wonder though
because I can manually guide in PHD2 better than hysteresis and PPEC...open to
any input...feeling defeated tonight :(
?
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Re: Used GM-8 Guiding Help
All good ideas.
The puzzle is this report: The worm blocks are loose and the worm must be loose.? But the axis is sticking or the worm is sticking?
This is a used mount, right?? Maybe it's needle bearings are gummed up and not rotating???
Sounds like the internal cylindrical needle bearings are gummed up.? If they have a varnish coating on them maybe that's causing trouble?
You'd have to pull out each axis and spray in or pour in a cleaning solvent, with a rag stuffed into the bottom of the axis 1.25 inch hole, to get those needle bearings rotating freely.? Let the solvent dissolve the gum or varnish.??
You can see the needle bearings in this photo of a G11.?
The other possible trouble is a bad worm bearing.? That would be felt as the worm rotates, when the worm is not engaged. you feel a sticking point or roughness.? Consider new worm bearings R4ZZ ABEC -5 or -7...higher -7 is supposed to be better.? Look for these on with the Komodo grease packing.??
Anyway, just a few thoughts.? Else this is a strange puzzle.
Michael
On Mon, Mar 1, 2021, 8:28 AM Brian Valente < bvalente@...> wrote: I suggest you err on the side of looseness with the RA. at least you can rule out stiction then
Thanks Brian,
The DEC was an odd adjustment this go around for some reason, even with the block pushed as far away as possible the worm seemed tighter than normal, but still rotated without much effort.?I'll revisit it but I'm really wanting to focus on the RA issues. The PA error was roughly 4arcmin based on the guiding assistant which is larger than normal for me, should have spent a little more time on it.
I believe part of the issue this time was the new gearboxes don't line up with the worm/oldham very well. I'll have to enlarge the mounting holes to move it further down, I had to do the same with the old gearboxes, just wanted to try these stock before hacking away at them
I agree the RA in one direction is my main issue and I cannot figure it out. I checked just to be sure, it is on the correct mount and all the gearing is set correctly and on sidereal rate and 0.5x guide speed.?
I do gotos successfully, not last night in particular, but I have never had issues with a goto once I've built a decent model with multiple stars
A week or so ago I played with the RA divisor by setting to comet rate and doing some calculations to slow it down 0.5asec/min (I believe this came to 56127 RA Divisor) it was a little aggressive/overshoot, so maybe I would consider slowing down by 0.3asec/min (roughly 56114). When I did the the testing I had trouble with clouds and it didn't seem to have big improvements, but I can give it another shot on a clear night.
I don't think I'm over tightening...but its hard to say I guess since apparently I've never felt what a fine tuned mount feels like. I'll try loosening up some, maybe I've been too focused on "minimizing backlash" and making things too tight...I'll feel dumb and happy if this has been the problem all along!
Tonights plan: Align gearboxes better, adjust worm mesh with stiction in mind, get a better polar alignment. On a separate run play with an RA divisor of 56114. I'll update assuming weather permits
--
Brian?
Brian Valente portfolio
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Help with interpreting PHD2 log on G11
Hi!
I've recently upgraded my C8 to a C11, and accordingly, things
started becoming problematic after that....? particularly my
guiding. I have an older G11, with OPW on the RA axis. I normally
have 0.6 - 0.8" RMS before, now I struggled a lot to come below
1". Most particularly, there has turned up some new "bumps" in the
RA and in general RA RMS is around 2x DEC RMS, which is not good
for my stars (elongated).
So I have been doing polar alingment, adjusting the RA worm and
all. And finally got it all to play nicely, I get a rather smooth
curve when doing unguided gudiing assistant in PHD2 or acquiring
data in PEMPro. The PE is a bit to big (some +/- 7") but that is
not much cause for worries when it is smooth. Frequancy analysis
shows almost nothing execpt for the worm ger at 239 secs. Nice!
So I capture a PEC curve and program my mount. And I see an RMS
of about 0.5". I am a happy amateur... for a few minutes. Then
there are some "bumps" coming on the curve. Now what is this? So,
here is my question to you - what might it be that causes this?
Attached is a PHD2 log from last night. There are a lot of
sessions because I do variable stars. But session 15 is the one I
am interested in now - the long one. There are a number of big
bumps, but since most are in RA and DEC at the same time, I assume
that is external things, like a wind gust or a bird landing on the
scope.
But when I choose a section betwen those bumps
and do a frequency analysis, I get a contribution from something
that is around 60 secs. This is the one I worry about now. See the
attached screenshot from PHD2logviewer frequency analysis window.
Anyone got any idea what might cause this frequency? I know of the
76 secs and the 31.9 secs, but this one....?
Any help much appreciated.
Magnus
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Re: Used GM-8 Guiding Help
I suggest you err on the side of looseness with the RA. at least you can rule out stiction then
Thanks Brian,
The DEC was an odd adjustment this go around for some reason, even with the block pushed as far away as possible the worm seemed tighter than normal, but still rotated without much effort.?I'll revisit it but I'm really wanting to focus on the RA issues. The PA error was roughly 4arcmin based on the guiding assistant which is larger than normal for me, should have spent a little more time on it.
I believe part of the issue this time was the new gearboxes don't line up with the worm/oldham very well. I'll have to enlarge the mounting holes to move it further down, I had to do the same with the old gearboxes, just wanted to try these stock before hacking away at them
I agree the RA in one direction is my main issue and I cannot figure it out. I checked just to be sure, it is on the correct mount and all the gearing is set correctly and on sidereal rate and 0.5x guide speed.?
I do gotos successfully, not last night in particular, but I have never had issues with a goto once I've built a decent model with multiple stars
A week or so ago I played with the RA divisor by setting to comet rate and doing some calculations to slow it down 0.5asec/min (I believe this came to 56127 RA Divisor) it was a little aggressive/overshoot, so maybe I would consider slowing down by 0.3asec/min (roughly 56114). When I did the the testing I had trouble with clouds and it didn't seem to have big improvements, but I can give it another shot on a clear night.
I don't think I'm over tightening...but its hard to say I guess since apparently I've never felt what a fine tuned mount feels like. I'll try loosening up some, maybe I've been too focused on "minimizing backlash" and making things too tight...I'll feel dumb and happy if this has been the problem all along!
Tonights plan: Align gearboxes better, adjust worm mesh with stiction in mind, get a better polar alignment. On a separate run play with an RA divisor of 56114. I'll update assuming weather permits
-- Brian?
Brian Valente portfolio
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Re: Used GM-8 Guiding Help
Thanks Brian,
The DEC was an odd adjustment this go around for some reason, even with the block pushed as far away as possible the worm seemed tighter than normal, but still rotated without much effort.?I'll revisit it but I'm really wanting to focus on the RA issues. The PA error was roughly 4arcmin based on the guiding assistant which is larger than normal for me, should have spent a little more time on it.
I believe part of the issue this time was the new gearboxes don't line up with the worm/oldham very well. I'll have to enlarge the mounting holes to move it further down, I had to do the same with the old gearboxes, just wanted to try these stock before hacking away at them
I agree the RA in one direction is my main issue and I cannot figure it out. I checked just to be sure, it is on the correct mount and all the gearing is set correctly and on sidereal rate and 0.5x guide speed.?
I do gotos successfully, not last night in particular, but I have never had issues with a goto once I've built a decent model with multiple stars
A week or so ago I played with the RA divisor by setting to comet rate and doing some calculations to slow it down 0.5asec/min (I believe this came to 56127 RA Divisor) it was a little aggressive/overshoot, so maybe I would consider slowing down by 0.3asec/min (roughly 56114). When I did the the testing I had trouble with clouds and it didn't seem to have big improvements, but I can give it another shot on a clear night.
I don't think I'm over tightening...but its hard to say I guess since apparently I've never felt what a fine tuned mount feels like. I'll try loosening up some, maybe I've been too focused on "minimizing backlash" and making things too tight...I'll feel dumb and happy if this has been the problem all along!
Tonights plan: Align gearboxes better, adjust worm mesh with stiction in mind, get a better polar alignment. On a separate run play with an RA divisor of 56114. I'll update assuming weather permits
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Michael Herman