Date   

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.


Re: ES G11 / ExploreStars issues

Steve Siedentop
 

Hi Jerry -

My DEC Direction and RA Direction question was referencing the "switches" in the Preferences pane.

Any thoughts on what those do and under what circumstances they should be set to "on?"

Screenshot attached.

-Steve


Re: ES G11 / ExploreStars issues

hubbell_jerry@...
 

Hi Steve,

Others have identified the issues with certain tablets running ExploreStars that doesn't show up when you load it up on a PC where the default rate is initially set to 53.00 instead of 53.32 as it should be (I just posted a message explaining the difference between the nominal 53.3333 rate and the actual 53.32 rate). The difference of 0.33 counts/sec is equal to a drift of 0.28125 * 0.333 or approx 1 arc-sec/sec which would amount to 5 arc-min drift in 5 minutes. Anyway, the fix is to select another mount such as the EXOS 2 and then go back to the G11 mount and the value should be fixed. 

RA and DEC Up/Down/Left/Right buttons perform the same as any traditional hand controller. You select the speed number (0 to 9) where 0 is 2 x sidereal and the rate basically doubles up to 9 for the fastest slew speed of around 3.3 deg/sec.

Jerry Hubbell
Director Electrical Engineering
Explore Scientific, LLC.


Re: ES G11 / ExploreStars issues

hubbell_jerry@...
 

The difference of 53.33 and 53.32 is the difference between the nominal calculated rate and the actual rate based on the firmware resolution. Since I use integers in the firmware for setting precision rates we have two different types. The slew rate and the precision tracking rate. The slew rate has a resolution of 1 count/sec which for the G11 is equal to  0.28125 arc-sec/sec increment. The precision tracking rate value is 25 times better and can be set to the closest 0.04 counts/sec or 0.01125 arc-sec/sec. So the actual rate closest to the nominal 53.3333 count/sec (which is the exact count rate for sidereal rate) is 53.32 counts/sec.

This is explained further in the PMC-Eight Programmer's Reference available on our website.

Jerry Hubbell
Director Electrical Engineering
Explore Scientific, LLC.


Re: MoveAxis Command

hubbell_jerry@...
 

Hi Chris, 

Yes the driver supports MoveAxis commands. If you connect the mount to the ASCOM POTH you can use the hand control there to demonstrate to yourself that it works. You can set the jog amount and the rate to different values.

Jerry Hubbell
Director Electrical Engineering
Explore Scientific, LLC.


Re: ES G11 / ExploreStars issues [1 Attachment]

David Pickett
 

At 18:29 30-04-18, sdsiedentop@gmail.com [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: ES G11 / ExploreStars issues

Steve Siedentop
 

Hi Mark / Jerry -

I had my G-11 set up for the first time this weekend and noticed tracking problems.  I worked through a few things related to my own misunderstandings and got the alignment process to work as expected.

However, once I was aligned and chose the first target, I noticed the target would drift out of the eyepiece in about 30 seconds.  I changed the tracking rate to 53.33 but had a couple of other variables in the mix including a low charge on my battery that may be causing the issue

Questions for Jerry (or anyone else that may be able to answer):

What function do the RA Direction and DEC Direction controls perform?
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 +)?

The debug data section of the screen is attached for review if it's relevant.

-Steve


Re: Guide Graphs and Impressions

W. Christopher Moses
 

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.

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