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Re: G-11 worm issues

ji.theriot@...
 

I don’t think anyone really knows a measurement for the acceptable degree of offset. This was on my RA axis. The worm on my dec axis is also very slightly misaligned but there is no binding. When I first removed my worm cover it was very obvious that the worm was binding on the RA side. If you were to try to turn the worm by hand it would spring back to its original spot. If you kept spinning it slowly that built up torque would unload and rapidly spin the worm. It’s hard to explain but it’s very obvious if you’re having this issue and try to turn the worm by hand.


Re: G-11 worm issues

W. Christopher Moses
 

Very interesting. Thanks for sharing.
Was it on your DEC or RA?
Did Jerry or Alex say what degree of misalignment is acceptable?  I'm not even sure how to measure that.


G-11 worm issues

ji.theriot@...
 

To make a long story short even with a perfect (literally a 0.0" on my guide log) PA I couldn't get my RMS under .9" on my new G11.  Peak to peak PE was >30".  Most nights RMS was about 1.1", still better than my old EXOS-2 but no where near what I was seeing from other G11 owners.


After reading Jeremy's detailed discussion about his mount and the large PE he was experiencing, I decided to look at mine.  What I found was a coupler that was binding and unloading as it rotated.  This was, as I discovered, due to the motor shaft and worm being offset from each other. 


After lengthy discussion with Jerry and Alex from ES, they will be milling me a new motor mount that is slotted to adjust it, which should fix things, but if you are having similar issues, I advise you look at the motor/worm alignment..


Re: Worm Cover Plate Set Screws (1/8" - 40 x 3/16")

W. Christopher Moses
 

Thanks


Worm Cover Plate Set Screws (1/8" - 40 x 3/16")

Steve Siedentop
 

All - 


I managed to lose one of the set screws from the DEC worm cover.


I found a suitable replacement at Harbor Freight in their Storehouse Set Screw Assortment (1/8" - 40 x 3/16").


https://www.harborfreight.com/150-piece-set-screw-assortment-67671.html


Hope this is helpful to someone at some point.


-Steve




Re: ES G11 / ExploreStars issues

David Pickett
 

At 16:47 01-05-18, Steve Siedentop sdsiedentop@gmail.com [ESPMC-Eight] wrote:

As Jerry stated, the RA Direction and DEC
Direction switches in the preferences pane
change the direction of each axis to accommodate
the mount pointing south. I had these turned
on, which may very well have been what was causing the drift.
Unless you are doing photography, or are using a
large magnification, it should be fairly easy to
keep objects in the field of view even if the motors stop running.

My next outing will include fresh batteries and
a standard configuration in the app.
Fresh batteries sound like an expensive long term
proposition. I am using a YUASA NP7-12 7.0 Ah
rechargable lead acid battery. I am also making
up a 12-19 volt convertor to keep my laptop
running from the same source. Time will tell
whether this has enough capacity for the job. Watch this space... :)

Best,

David


Re: Guide Graphs and Impressions

W. Christopher Moses
 

Hi,
I will look in to the RA Osc number, I've never really paid much attention to it.
Thanks for the tip.

I am pulse guiding.  What are you using?


Re: Guide Graphs and Impressions

W. Christopher Moses
 

Hi,
I always try to get as close as I can to the equator and meridian but my FOV at home isn't the greatest.   The number of guide pulses in each direction is pretty close during the calibration. I did a star-test at one point, just as a sanity check, and it looked good - all sides were equal. 


Re: Guide Graphs and Impressions

W. Christopher Moses
 

Hi Sunil, Jeremy,
When I first received my PoleMaster it was out of focus. After I fixed that it worked perfectly, as far as I know, until a few nights ago - which is the first time I've used it since last winter.  I wonder if it has slipped out of focus again.  It looks ok on the screen.
Those are good tips. Thanks.
Actually, SC requires a pretty large field of view 1-5 degrees, so I was using my main camera.

Looking at the forecast, it will be a few nights before I get to test anything, but I look forward to it.


Re: ES G11 / ExploreStars issues

Steve Siedentop
 

Thanks, David.

Through a good bit of experimenting, I introduced too many variables to be able to determine the cause of the tracking issues.

As Jerry stated, the RA Direction and DEC Direction switches in the preferences pane change the direction of each axis to accommodate the mount pointing south.  I had these turned on, which may very well have been what was causing the drift.

My next outing will include fresh batteries and a standard configuration in the app.

-Steve

On Mon, Apr 30, 2018 at 1:20 PM, David Pickett yahoo@... [ESPMC-Eight] <ESPMC-Eight@...> wrote:
 

At 18:29 30-04-18, sdsiedentop@... [ESPMC-Eight] wrote:
>Questions for Jerry (or anyone else that may be able to answer):
>
>What function do the RA Direction and DEC Direction controls perform?

They are instead of steering the mount by hand;
as long as the clutches are engaged, PMC will
continue to know where the mount is pointed.

>Also, would a .33 difference in the tracking
>rate present itself visibly in the eyepiece in a
>very short period of time, or is it something
>that would present itself in a long exposure (5 minutes +)?

(0.33/53.33) x 100 = 0.62%

Since the stars move 15°/hour, or 1.25° per 5
minutes, even if your mount doesnt move for five
minutes, a star will only have moved 1.25° from
the centre of view. If the field of view of your
scope/eyepiece is greater than 2.5°, the star
will not have reached the edge of the field of
view in 5 minutes! Thus, if your mount is
tracking 0.62% slower than it should be, the star
should still be well in view after longer than 5 minutes.

David



Re: Guide Graphs and Impressions

Jeremy Parker
 

Hi Sunil,

Interesting, I'll keep an eye out for any sudden issues with mine. The atmospheric refraction is in one of the menu settings, can't remember off the top of my head. Also, the camera must be oriented correctly when using this feature (so the USB connector is pointing horizontally to the left when looking into the lens of the camera). I can see why using your main imaging camera would be most accurate for this. Maybe someday when I get a real astro cam, I will switch over to this method. In the meantime, I can get pretty good polar alignment and see no field rotation in over 8 minute exposures (longest I've tried).

Thanks,
Jeremy


Re: Guide Graphs and Impressions

Sunil Bhaskar Bhaskaran
 

Jeremy,

        The problem started all of a sudden. The gain and sensitivity are lowest actually. I choose a star thats further away from Polaris so that the alignment is more accurate.Where do you see the atmospheric refraction option? SOmeone mentioned this point to me at Cloudynights. I use my Imaging camera ( 1600mm-c ) to align with sharpcap. I measure the PA error running the guiding assistant at phd2. With Sharp Cap , the only thing guiding assistant tells me is to adjust a few settings like Hysterisis or Aggressio where as with PM it says to redo polar alignment > 10px or something. Really appreciate you giving your feedback Jeremy.

Sunil



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On Tue, May 1, 2018 at 8:48 AM, jrs1@... [ESPMC-Eight] <ESPMC-Eight@...> wrote:
 

Hi Sunil, Chris,


You guys both had issues with PoleMaster? Was it all-of-a-sudden, or from the beginning? I've pretty consistently been able to get polar aligment at 1" or less. I've done a few things to insure I get the best alignment each time, and I think they help. First, I set the camera sensitivity (gain and exposure) not to brightest, but a couple steps down. I'm thinking that the stars around Polaris shouldn't be saturated, in the same way the PHD2 can't find the centroid if there isn't a good star profile. I also use the atmospheric refraction option (probably only a small difference since I'm at 42°N). Then, I make sure that the alt-az knobs and RA clutch are all tight when the mount is rotated (using POTH motion controls), so the axis of rotation isn't dynamically changing as the mount rotates. Then I choose a star pretty far out from the center and rotate a bit more than 45° at a time, so there is a larger part of a  larger circle being represented by those three star positions. Hopefully that gives me a better estimation of the center of rotation of the mount.

Maybe you tried some of these things this already, but just figured I would mention them.

Alternatively, I wonder how much better I could get with SharpCap? Is it better for you guys, because your guidescope has a smaller image scale than the PoleMaster camera/lens? What do you measure for polar alignment error with SharpCap?

Thanks,
Jeremy



Re: Guide Graphs and Impressions

Jeremy Parker
 

Hi Sunil, Chris,

You guys both had issues with PoleMaster? Was it all-of-a-sudden, or from the beginning? I've pretty consistently been able to get polar aligment at 1" or less. I've done a few things to insure I get the best alignment each time, and I think they help. First, I set the camera sensitivity (gain and exposure) not to brightest, but a couple steps down. I'm thinking that the stars around Polaris shouldn't be saturated, in the same way the PHD2 can't find the centroid if there isn't a good star profile. I also use the atmospheric refraction option (probably only a small difference since I'm at 42°N). Then, I make sure that the alt-az knobs and RA clutch are all tight when the mount is rotated (using POTH motion controls), so the axis of rotation isn't dynamically changing as the mount rotates. Then I choose a star pretty far out from the center and rotate a bit more than 45° at a time, so there is a larger part of a  larger circle being represented by those three star positions. Hopefully that gives me a better estimation of the center of rotation of the mount.

Maybe you tried some of these things this already, but just figured I would mention them.

Alternatively, I wonder how much better I could get with SharpCap? Is it better for you guys, because your guidescope has a smaller image scale than the PoleMaster camera/lens? What do you measure for polar alignment error with SharpCap?

Thanks,
Jeremy


Re: Guide Graphs and Impressions

Jeremy Parker
 

Hi Chris,

Did you run your calibration near the celestial equator and meridian? I wasn't initially, and I was getting unexpected values for DEC/RA. Ideally, when you're near 0° declination, you should get equal movements for RA and DEC, in terms of how much guide star motion is produced by a given guide pulse, and therefore the best calibration. Then when you slew to your target, PHD2 should be able to compensate for being at a different location, assuming you're using ASCOM pulse-guiding.

Regards,
Jeremy


Re: Guide Graphs and Impressions

Sunil Bhaskar Bhaskaran
 

Chris,

            Good to see you active now a days :) . Long time since we talked . I really like SharCap. I contacted Qhy , changed the polemaster mutiple times but no avail. One thing I might suggest is taking a look at the RA OSC value. WHen I had some of my best guidings , the RA OSc used to around .3 . Later on I found out that .3 is bad ( Even though its the ideal value) where as something between .4 to .5 is what is preferred. .3 or .2 means we are over correcting in RA or Dec. I had this issue with Polemaster. The detaulf speed of .4 works well for me. Just one doubt : Are you pulse guiding or St4?

Sunil



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On Tue, May 1, 2018 at 1:09 AM, chris_moses@... [ESPMC-Eight] <ESPMC-Eight@...> wrote:
 

Yep, a PA with SharpCap seems more accurate than PM by far.  PhD2 still shows a higher PA error than SharpCap, but not by nearly as much.


I also really like SharpCaps suggestions about how to identify if you have flexure or hanging cable issues:


My most recent guiding data is
RA    0.52 (0.63")
DEC  0.45 (0.55")
TOT 0.7 (0.85")

Much better!!

I've been running the PPEC algorithm for about 30 minutes. I haven't run the standard hysteresis so I'm not sure if it is any better.
I also bumped my guide rate up to 0.6x. PhD2 recommends at least 0.5x, but the PMC-8 ASCOM driver defaults to 0.4x 



Charlie Elliott Astronomy May 2018Meeting and Observing

Steve Siedentop
 

If you're going to be in the general vicinity of the Atlanta area next weekend, check out this astronomy club meeting.


https://mailchi.mp/4bae8439b39a/astronomy-club-meeting-saturday-april-14-2018-600-pm-2125401?e=9fbcfde3ce


-Steve



Re: Guide Graphs and Impressions

W. Christopher Moses
 

Yep, a PA with SharpCap seems more accurate than PM by far.  PhD2 still shows a higher PA error than SharpCap, but not by nearly as much.

I also really like SharpCaps suggestions about how to identify if you have flexure or hanging cable issues:


My most recent guiding data is
RA    0.52 (0.63")
DEC  0.45 (0.55")
TOT 0.7 (0.85")

Much better!!

I've been running the PPEC algorithm for about 30 minutes. I haven't run the standard hysteresis so I'm not sure if it is any better.
I also bumped my guide rate up to 0.6x. PhD2 recommends at least 0.5x, but the PMC-8 ASCOM driver defaults to 0.4x 


Re: Guide Graphs and Impressions

W. Christopher Moses
 

Hi Sunil,
Good to talk to you again.
I'm really glad you told me that.  I thought I was going insane.  I just redid my PA in PM 3 times and my error in PhD2 is still 25 arc-min!!


I've never heard of PM being off before. Have you contacted QHY or checked their support forums?

Looks like I'm about to buy SharpCap.

10 min unguided at fl 900? That is great. Congrats!


Re: Guide Graphs and Impressions

Sunil Bhaskar Bhaskaran
 

Chris,

         I think you are in the same boat as me : for some reason Polemaster is not giving me good guiding results with phd2( I follow the alignment procedure to the letter). When I use sharp cap to polar align I am perfectly aligned. Even Jerry has seen how good I am able to align with Sharp Cap. Pmc8 allows me a good 10m unguided at 900mm focal length where as polemaster only allows me 4m atmost. I even asked Jerry if he knew anyone who had faced similar issue with Polemaster and G11. Also opened a thread in CN but results were inconclusive. 

P. S : There is another post regarding the goto performance of the mount and I can say one thing : With Sharpcap my goto is phenomenal : target is right in the field of view. There is no need for a star alignment, where as polemaster is waaay off. Meridian flip with Sharpcap is better as the item is perfectly centered too.

Sunil 



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On Mon, Apr 30, 2018 at 11:09 AM, chris_moses@... [ESPMC-Eight] <ESPMC-Eight@...> wrote:
 

I did notice that my expected and actual RA and DEC rates were slightly different.  I'm not sure how big of a difference is important:


         ACTUAL        EXPECTED
RA      4.725 a-s/s       4.7
DEC   6.143 a-s/s       6.0 

The orthogonality error was 3.7, which I think is pretty good.
I'll do some research on the rates, but if anybody knows anything about them, please chime in.

Tonight I', going to try to characterize the PE.



Re: ES G11 / ExploreStars issues

hubbell_jerry@...
 

These change the motor direction. When you are in the southern hemisphere you need to set it the opposite for the RA. We have not really tested these as Scott has not bought us a trip to Australia to go test this feature. Maybe someday!

Jerry Hubbell
Director Electrical Engineering
Explore Scientific, LLC.

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