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Re: Counterweight Placement

W. Christopher Moses
 

How can you be all the way up with a 16 lbs rig? I guess I need to weigh mine. I'm halfway down with a 115 refractor, but I do have a mini-pc and all the electronics on top of it.


Re: Dec Worm Adjustment

W. Christopher Moses
 

Hi Jerry, Jeremy,
I'm trying to think of some way to qualitatively measure the rotational rate of my couplers to see if it changes as a result of storing and releasing energy.  The best I can think of is to score the coupler at regular intervals and then take a video for a full rotation. Hopefully, any large release would be visible.  I could also count the frames per scoring mark.

Come to think of it, I could also just directly tell the stepper to take X steps/second and see if the score marks moved consistently.

Can you think of anything simpler or more accurate?


Re: Paper on all the errors causing oblong stars in astrophotographs [1 Attachment]

W. Christopher Moses
 

Ironically, I was actually looking for that earlier today.  You originally posted it as a "normal" post, right?
I was thinking about it in relationship to the relative benefits of Drive Master and/or of adaptive optics.

I would like to see an updated version.

Thanks,
Chris

On Friday, August 10, 2018, 8:21:19 PM EDT, hubbell_jerry@... [ESPMC-Eight] wrote:


 
[Attachment(s) from hubbell_jerry@... [ESPMC-Eight] included below]

I posted the attached paper to CloudyNights a couple of years ago I think and since we have had a few discussion about how our mounts contribute to or detract from that perfect star image, I thought it might be good to revisit this paper and update it based on what I have learned the past couple of years.


Let me know you thoughts and we can discuss it so that I can make it better.

Thanks

Jerry Hubbell
Director Electrical Engineering
Explore Scientific, LLC.


Paper on all the errors causing oblong stars in astrophotographs

hubbell_jerry@...
 

I posted the attached paper to CloudyNights a couple of years ago I think and since we have had a few discussion about how our mounts contribute to or detract from that perfect star image, I thought it might be good to revisit this paper and update it based on what I have learned the past couple of years.

Let me know you thoughts and we can discuss it so that I can make it better.

Thanks

Jerry Hubbell
Director Electrical Engineering
Explore Scientific, LLC.


Creation of the Explore Scientific OpenGOTO Steering Committee

hubbell_jerry@...
 

As a result of the OpentGOTO Community Conference held last month at the Explore Scientific headquarters in Springdale, Arkansas, Explore Scientific is proud to announce the formation of the OpenGOTO Community Steering Commitee. 


This committee will drive the future direction for sharing the PMC-Eight technology with the OpenGOTO Community and develop the procedures and processes that we will use to make the system fully accessible to PMC-Eight users and developers. This includes sharing the source code for the ExploreStars application, ASCOM driver, and other test programs via GitHub or similar open source platform, and improving all the documentation for the PMC-Eight System.


I will serve as the committee Chairman and several forum members that attended the conference have been asked to volunteer to serve on this committee. A couple of other people will round out the committee membership:


Executive Sponsor: Scott Roberts

Committee Chairman: Jerry Hubbell

Developer Representative: Dan Dickerson

Vendor Representative: Steve Mallia

Customer Representative: Chris Moses

Customer Representative: Steve Seidentop

Customer Representative: Brian Tucker


Michael Fulbright, the developer of the LINUX PMC-Eight INDI Driver will be consulting with us also as he becomes available in the future.


I will share the progress of the team in the coming weeks and months as we work to effectively share the PMC-Eight technology with all our customers and others that are interested. We will be letting you know how everyone can become involved at whatever level you wish to contribute.


Thanks again for your support and interest in the PMC-Eight System and our other products.


Jerry Hubbell

Director Electrical Engineering

Explore Scientific, LLC.




Re: Counterweight Placement

Jeremy Parker
 

Hi All,

I've been keeping my 21lb. counterweight all most all the way up with my G11 and my ~16lb rig, rather than moving to an 11lb counterweight further down the bar, for the above mentioned reasons. It's the smaller moment of inertia that should allow the mount to settle more quickly and respond faster to guiding impulses, etc. The only thing I wonder about is at what point does the added weight of the former case cause orthogonality problems or runout on the axis bearings, etc. that the latter wouldn't have. So I'm probably no where near that point, but maybe that's something also to keep in mind?

Actually, thinking about it just now; since I'm always up towards the top of the bar, maybe I should move to the shorter 8" counterweight bar, to reduce overall weight further and slightly reduce the moment of inertia? What's another $100 at this point? :)

Jeremy


Re: Dec Worm Adjustment

Jeremy Parker
 

Hi Jerry, Chris,

I'd guess that Scott is aware of the 76s error that some experience, and perhaps the OPWB was a way to minimize that (at least compared to the stock 3-piece setup). I've emailed Scott and Tanya several times about my efforts to get to a single, spring-loaded OPWB that is directly attached to the motor, but it seems they're too busy to engage in much discussion about my particular situation. Tanya also mentioned that they have no awareness or involvement in the ES drive system, and that I should direct my inquiries to ES, not Losmandy. So I get the sense that they don't want to be bothered. If I want to speak to Scott directly, I'd probably have to wait until NEAF next year.

Chris, I'll try your approach of not tightening the clutch so much, and see if that makes any difference. I have noticed that my PE has changed with different worms, different couplers, different bearings, and different adjustments of the mesh and above components - but never coming close to matching your performance. I have log files and even pictures of the 3-D printed motor plate prototype that would allow me to attach the motor directly to the OPWB, but I'll add this to an existing thread or start a new one, as this is getting off-topic from the DEC worm adjustment.

Thanks,
Jeremy


An existing poll has been modified, check it out.

ESPMC-Eight@...
 

Which features would you most like to see in a wireless-settings utility for the PMC-8?
Created by: Chris_Moses
  1. Ability to operate the PMC 8 in Access Point mode (added by: stevesiedentop . August 9, 2018)


Thanks!


New poll for ESPMC-Eight

ESPMC-Eight@...
 

Enter your vote today! A new poll has been created for the ESPMC-Eight group:
Which features would you most like to see in a wireless-settings utility for the PMC-8?
Created by: Chris_Moses
  1. Easy wired to wireless switching
  2. Changing the default PMC-8 wireless network name (SSID)
  3. Changing the default wireless password
  4. Other - Please Add


Thanks!


Re: Counterweight Placement

W. Christopher Moses
 

Hi,

I agree with Jerry, the torque is equivalent and the rotational inertia is not, clearly. It is precisely Jerry's last two points, and their affect on real-world data,  that interests me.

Jim's observations are consistent with my expectations.

I've ordered another counterweight and will report back. It will be interesting to see if it has an effect on any periodic errors or best guiding rate. 


Re: Dec Worm Adjustment

W. Christopher Moses
 

Jerry,

Stop Tinkering....???? Does not compute!


Re: Counterweight Placement

James Buck
 

Okay, Here we go...  I have the Exos2PMC8 system and have 3 counter weights.  One higher, one just below that and the third just above the end of the CW bar.  I have a Bresser 8 inch Newtonian 208mm f/3.9 and a First Light 4 inch x 600mm with a combined weight of 27 pounds.  With the with the Exos2 PMC8 I have found a little vibration at the end of a fast slew.  I could have went with a longer rod and two weights, however I had much more vibration with the longer counter weight bar.  So for my two cents worth, heavier weight, shorter bar as Jerry H. suggested.

Jim B


Re: Counterweight Placement

hubbell_jerry@...
 

My thinking is that the torque applied is equivalent, but the harmonic frequency of the system changes because of the length of the moment arm. If the weight is greater and higher up on the shaft, the harmonic frequency of the system is higher and will (probably) settle out faster than when the weight is hanging way out on the end of the counterweight shaft. This seems to be a better configuration overall. There are other factors involved including the correction rate for the tracking and the magnitude of your non-periodic (random) error in the tracking rate.

My two cents.

Jerry Hubbell
Director Electrical Engineering
Explore Scientific, LLC.


Counterweight Placement

W. Christopher Moses
 

There are numerous threads on CN about whether it is better to have more weight high up or less weight lower down on the CW bar.  

I can dust-off my physics degree enough to understand the concepts without any problem, but I was wondering if anyone with our specific mounts has actually experimented with weight(s) placement.


Here are a few articles on the subject:

http://www.astro-physics.com/products/accessories/mounting_acc/Balance_to_Optimize_Guiding.pdf

http://www.robincasady.com/Astro/WeightCalc.html




Re: Dec Worm Adjustment

hubbell_jerry@...
 

Thanks Jeremy for finding more about the 76 second periodic error. I wonder if Scott Losmandy has done any work to improve this with the OPWB as stated in the linked article about the error. It sounds like that was the plan.

Jerry Hubbell
Director Electrical Engineering
Explore Scientific, LLC.


Tripod Case

W. Christopher Moses
 

Hi,

I just received my tripod case from Losmandy:


http://store.losmandy.com/fhdcase


Just in case (haha) anybody was wondering, it is really nice,  It's an SKB brand. I'm not sure if it is a special SKU or just one they found that works, but I'm happy,

It has a few extra inches at the top than I'm going to use to duct tape in a desiccant pack



Re: Dec Worm Adjustment

W. Christopher Moses
 

Jeremy,
Very, very interesting about the error.  I will look into that.

I wish I could tell you why my guiding improved so much.  All I did was
1. Remove, clean, and regrease the worm. (it had been open in a really buggy, pollen-filled area)
2. Try to get everything situated as tightly as possible without binding.
3. Switch to not tightening my clutches as much.  If you turn the worm by hand while tightening the clutch, you can feel how much of a difference it makes.

Have you posted any of your recent logs?  Please do


Re: Dec Worm Adjustment

W. Christopher Moses
 

I'm just pulling out my mount.  I'll double check my gaps, but my motor side was smaller than the other side.

I dont think the gaps in the ra and dec should have any relationship upon each other.

Backlash - that is a good question.  I've wondered that also. I'm pretty sure 1500 is close to reasonable and 4500 is large.  But, my GA failed to measure mine the last two nights and I had good guiding.  So, I wish I had a better answer but ultimately if the guiding is ok....



Re: Dec Worm Adjustment

Mark Lamb
 

According to PHD2 GA, my DEC has backlash problems.  A few nights ago it was ~4100ms, and after loosening and tightening, it was 1568ms.  This seems to vary from night to night even without any adjustments (measurement error?).

Today, I just got some feeler gauges and checked the gap between the bearing blocks and the flats on the mount.  I checked the DEC, and the motor side bearing block had a  noticeable wider gap that the far bearing.  With my feeler gauge, I used the 2 widest consecutive blades, totalling 0.047", and adjusted both of the blocksto this gap.  This was definitely tighter on the motor side, and I did not record the pre-adj distances.

I then checked the RA worm distances, and they are tighter.  But the motor side has the smallest gap at 0.033" and the far block at 0.037".  I did NOT make any changes on the RA worm.

Questions:
Are there any recommended block gaps?  If so, what?

Is the small difference between my RA block gaps OK?

Should the gaps in the RA and DEC worms be the same?

What amount of backlash is OK?

Thanks!

Mark


Re: Dec Worm Adjustment

Jeremy Parker
 

Hi Guys,

The 76" error is a known issue with G11s, if you look on the forums/studies people have done. It is close to a 3rd harmonic, but not quite. Usually, it is associated with worm bearing misalignment and bearing race issues.


I have noticed it on my setup, especially if there is too much compression force applied between the two bearing blocks (to remove the side-to-side play in the worm) when tightening them, either on the stock setup or OPWB.

I just can't believe how low your 240s PE is though, and I'm left wondering what it would take for me to get even close that level. My stock worm in the OPWB is giving me 16" peak-to-peak, at best. The 2nd OPWB with new worm is giving much less peak-to-peak error, but the waveform is very strange, with many unrelated frequency components. I'll break this out to a seperate thread, or post it onto the OPWB thread when I have more data to share.

Jeremy

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