Date   

Re: Guide Graphs and Impressions

Jeremy Parker
 

Hi Ji,

OK, right, sorry about that. I think Jerry passed along the same message from Alex about the couplers. If you check out helical couplers on McMaster-Carr, you'll see the amount of allowable axial/parallel misalignment seldom exceeds 0.005-0.008". 
So if I can measure 0.017" of runout from the coupler itself, how well could that possibly work? They are cheap Chinese couplers that have secondary operations performed on them to fit the G11, while the Ruland couplers are precision-made for 1/4"-to-5mm, plug-and-play. They are expensive in single quantities, but also have clear and extensive specifications, so in my mind, they are well worth the money.

I spoke to Scott Losmandy at NEAF, and the only reason he does not use the Ruland helical beam couplers, is because they can 'wind up' and release torque suddenly if the worm binds at all, with the servo-style motors in the Gemini G11. So this is why he prefers the Oldham couplers that cannot 'store' any energy. The torque capability of the stepper motors is much less, and he agreed that these should work well for the ES G11. When there is binding, the steppers just lose steps and make an audible sound.

So for anybody looking to tune their mount and reduce PE, I can't recommend the Ruland couplers enough.

Jeremy

---In ESPMC-Eight@..., <ji.theriot@...> wrote :

Jeremy,
I am the one that posted the picture of the offset motor shat. ES is milling a new motor plate at my suggestion that has about 2mm of lateral movement along with countersunk screws, rather than the button head screws that are currently used which bracket the motor and lock it into place. Hopefully this will get the shaft in line with the worm and smooth things out.

Both of my couplers are bent and have significant run out but Alex told me that that’s the way they are designed. I showed him what you did with the Ruland couplers (although he insisted that they would not work).

I’ve also developed a 12” spike that shows up every 10 or 12 min. Not sure what that’s about.

Ji


Re: Guide Graphs and Impressions

ji.theriot@...
 

Chris,
My guide rate is set to .7 and my dec aggression is 60%. My PA is typically in the .5 range. Last night it was ~1.


Re: Guide Graphs and Impressions

ji.theriot@...
 

Jeremy,
I am the one that posted the picture of the offset motor shat. ES is milling a new motor plate at my suggestion that has about 2mm of lateral movement along with countersunk screws, rather than the button head screws that are currently used which bracket the motor and lock it into place. Hopefully this will get the shaft in line with the worm and smooth things out.

Both of my couplers are bent and have significant run out but Alex told me that that’s the way they are designed. I showed him what you did with the Ruland couplers (although he insisted that they would not work).

I’ve also developed a 12” spike that shows up every 10 or 12 min. Not sure what that’s about.

Ji


Re: Guide Graphs and Impressions

W. Christopher Moses
 

Ahhh... You said peak to peak error, not PA error.  My mistake.


Re: Guide Graphs and Impressions

Jeremy Parker
 

Hi Jerry,

Yes, I think the guiding was really good, aside from the oscillations which I think I made improvements on as the night went. Tonight is a different story, but I think it's mostly due to the seeing conditions up here in the northeast. Maybe down the road I'll think about a bigger guidescope or better guide cam.

Jeremy


Re: Guide Graphs and Impressions

Jeremy Parker
 

Yes, the seeing is pretty bad tonight, so I'm getting 0.8" RMS total, it seems. Wow, 38" peak-to-peak could be the culprit for your issues. I had a similarly bad PE, and it turned out to be a bent helical coupler, as well as more fine-tuning of the worm and bearing blocks. Have you seen my thread here or on Cloudy Nights?


Re: Guide Graphs and Impressions

W. Christopher Moses
 

Hi,
    I don't trust the PA error in PhD2. I'm working on a CN post about it right now.  I do want to learn how to use the Static Alignment tool just to compare it to other methods.

I got much better results when I set the guide rate to 0.6x.  PhD2 recommends at least 0.5x. (If you want to use 0.6x, change it in the driver. I think PhD2 will pick it up automatically)

So far, I'm getting the best results with the PPEC algorithm and 2-4 second exposures.  I find the Auto setting bounces around a lot.

Of course, that is just my set-up...

Hope that helps a little,
Chris


Re: Guide Graphs and Impressions

ji.theriot@...
 

Well I ran the guiding assistant for about 12 minutes and it recorded a 38.01" peak to peak error.  That's my first issue.  But I'm guiding with a 1.6" RMS error with 1.37" in RA.  I don't know if my guiding speed is off or what.  I've tried both sidereal and King speed but I'm not getting very good results with either.


Re: Guide Graphs and Impressions

W. Christopher Moses
 

    Well, if it makes you feel any better, I'm barely getting 1.0"  tonight.  As usuall, my dec is all over the place.  I'm going to post some info about that and PA in a separate post.
    I am imaging at a dec of almost 70. Much higher than the past few nights.


Re: Guide Graphs and Impressions

ji.theriot@...
 

Geez, I am so jealous of you guys...I just want to get below 1.0"...like once.

Ji


Re: Guide Graphs and Impressions

hubbell_jerry@...
 

Hi Jeremy,

I just read through you posts on CloudyNights. It looks like your RMS guiding in terms of pixels were < 0.15 or so which in my mind is excellent. I don't know what the limits of PHD2's centroid algorithm is, but it seems to me that you would need to change your plate scale on your guiding camera to improve it any more. I think your guide scope has a focal length of 210 mm with a plate scale of 3.68 arc-sec/px. If you could get this to around 2.5 arc-sec/px then you may still see some improved guiding, perhaps < 0.5 arc-sec total RMS.

Jerry Hubbell
Director Electrical Engineering
Explore Scientific, LLC.


Re: Guide Graphs and Impressions

W. Christopher Moses
 

Just to clarify - those numbers are in arc-sec. not pixels.


Re: Guide Graphs and Impressions

W. Christopher Moses
 

Hi,
    Thanks for the update!
    I've seen about the same thing - very good RA, good overall RMS,  but a little choppy in DEC.

    I don't have the exact numbers in front of me but Sun. my total RMS was about .6.  Last night it was up to about .75.  Both nights I was using PPEC, which seems to work better for me than hysteresis.  Both nights my DEC was higher than my RA.
    I'll try turning down the DEC aggressiveness. I don't recall exactly what it was.  I did about a 10m Guiding Assistant run and took its recommendations.

Chris


Re: Guide Graphs and Impressions

Jeremy Parker
 

Hi All,

Just another update on my G11 guiding. Predictive PEC in PHD2 is working well, and I'm consistently able to get RA RMS error around 0.45" on average now. The DEC backlash issues I think have been improved by tweaking the DEC aggression setting in particular, from 0.8 down to 0.55. Basically, oscillations would occur, where corrections back and forth (north and south) would overshoot. Turning down the 'gain' I think is the solution for the time being. If I ignore the regions of large oscillations, DEC RMS error was also around 0.45", with total RMS error of 0.64" on average. I will hopefully be able get more time with these settings tonight, but here's my rundown on Cloudy Nights:


Regards,
Jeremy


Re: D or V series saddle for EXOS2 ?

hubbell_jerry@...
 

Hi Wes,

I purchased a similar saddle from ADM about 8 years ago to go on my SkyWatcher EQ6 Pro mount and it works great, but like you said, it is very expensive in relation to the total cost of the mount almost 20%!!
Having said that, what price can you put on convenience and time savings if you find it necessary?

Jerry Hubbell
Director Electrical Engineering
Explore Scientific, LLC.


Re: D or V series saddle for EXOS2 ?

Wes Mcdonald
 

So I found in Cloudy Nights a fellow who put this on his Exos-2

DUAL-GPDX- DUAL Series Saddle. Fits Vixen GPDX Mounts.


It looks like it replaces the saddle that came on the Exos-2.  Interested in knowing if that seems right to anyone.  Jerry?  Dang thing cost $160, a high percentage of what the PMC-8 package cost!

Wes.



Re: Forum Purpose and Member Comments and Questions.

r_hoskin@...
 

+1.   What Chris said...

I've learned a lot, reading posts about issues that I have not yet encountered ( but probably will, some day).
No need to restrict oneself to current posts, either...   

- Bob


Re: Forum Purpose and Member Comments and Questions.

W. Christopher Moses
 

Personally, I really enjoy the posts here. Even if the thread goes way off topic, not something I am advocating, I still learn something.

Also, I enjoy getting people up and going on the PMC-8 system.  I learn something every time and,  the more of us there are, the more tips and tricks we can share.

Just a few days ago, Cyclops (Sunil) saved me immeasurable hours of frustration when he pointed out that my PoleMaster looks like it is having problems.

My personal advice to new and old members alike is to share as much as possible.  If you are having a problem, post it!  The worst that happens is we don't know and suggest that it is a better topic for CloudyNight.

Use common sense, but observing time is highly valuable.  It's better to post a problem or question than to lose multiple nights trying to figure it out. 90% of the time, it will be something simple - and, again, I've just learned to avoid that mistake.

Just my thoughts.

Chris



Forum Purpose and Member Comments and Questions.

hubbell_jerry@...
 

HI Cyril, Mark,

The purpose of this forum is stated in the group description on the main page and states in part:

"This is a public forum for our customers to discuss their experience with the PMC-Eight and the associated mount hardware..."

So in my mind Marks comments and questions about the PMC-Eight ASCOM driver are appropriate. I think your issue is and unfortunately will continue is that members do not take the time to provide descriptive enough subject lines for their comments and questions. 

I think the best that we can expect is to remind those that we are talking to to change the subject line when change the topic, or start a new thread. 

Not to pick nits, but I noticed Cyril that you did not change the subject line of your response to Mark about starting a new forum.

I really don't want this to get contentious, and I apologize to anyone if this is becoming tedious. It is up to all the members to decide for themselves how much time they want to spend reading these posts and actually answering fellow members questions. 

I am always grateful for anyone posting on this forum especially if you are actively helping a fellow member with a problem when I am not available in a timely manner to provide support.  As always, anyone can email me if they have a question they do not wish to share on the forum.

Jerry Hubbell
Director Electrical Engineering
Explore Scientific, LLC.
 


Re: D or V series saddle for EXOS2 ?

W. Christopher Moses
 

One thing about the side by side saddles is that they can make balancing a little bit more difficult.
Having said that, I have one I've been meaning to sell.  It's a dual D/V setup from ADM.
Let me know if you are interested.

9141 - 9160 of 10082