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Re: Can't get less than 1" total RMS

Mike Ahner
 

On Thu, Jul 22, 2021 at 07:13 PM, Henk Aling wrote:
I would like to understand the effect on tracking accuracy.
Maybe start here:
main@onstep.groups.io | Wiki


Re: Can't get less than 1" total RMS

Henk Aling
 

On Thu, Jul 22, 2021 at 07:10 PM, Alexander Varakin wrote:
Henk,
Can you share your guide graph for this session?
Not for this session but I will get a PHD2 log tonight.

Are you getting most of error on RA or on DEC?
This time about 50% more on RA but that was also because I did not counterweight much.  During my best run at 0.6" total RMS they were about equal.

Can you share your unprocessed stack? I can measure the PSF for you.
I will put an Autosave.tif on my cloud space and let you know.

One more question, I can't find good references for the TMC2130's Vref.  There was a calculator online that returned 1.27 V for my 0.9 Amps/phase (== Irms I think).  Howard said to turn it down to half that, which I did.  I would like to understand the effect on tracking accuracy.  I will experiment tonight.


Re: Can't get less than 1" total RMS

Alexander Varakin
 

Henk,
Can you share your guide graph for this session?
Are you getting most of error on RA or on DEC?
Can you share your unprocessed stack? I can measure the PSF for you.



Re: Can't get less than 1" total RMS

Henk Aling
 

Thanks Mark.  The numbers you mentioned are helpful.

I am very aware of the large weight especially now that I am getting more experience with it.  I will try imaging with my 6" Mak-Newt and see if it works better than the 12".

I am using DIY spring loaded worms that work great for goto.  For tracking I have turned them off sometimes and did not notice much difference.

I think my PA is very good as I do it using Ekos.  No drift unguided.  I am counterweighting in RA, not quite ready to misalign in DEC.


Re: Can't get less than 1" total RMS

Mark Christensen
 

Henk,

There are two variables you didn't consider: Your skies and the sheer weight (not to mention the moment of inertia) of your rig.

I used my G11 for several years with a 12" f/5 and it was hit or miss for imaging - sometimes I couldn't shoot longer than 120seconds, while other times I could go for 300sec. And of course it made a great sail in any breeze.

When I pulled in my horns and went back to my 8" f/5.5 everything was much more reliable, even if I stick a Barlow on it.

As to guide rate, 0.5X is the max I'd go. The only time I guide at 1X is when I am doing something like chasing a comet head.

Personally I shot 1 to 2 second guiding exposures. If I have done decent job of polar alignment and the skies are stable I get between 0.25 and 0.33". The reason why polar alignment is important is because the fewer corrections the mount makes in either axis the less chance there is that it will impact the other axis. But I don't do a perfect job of polar alignment since that way all corrections (aside from chasing seeing) will be in one direction on DEC. So backlash isn't a player there, and of course it isn't a player in RA either, if you bias the RA balance slightly eastward - that way the gear faces always stay in contact.

Stock G-11, high precision worms, old fashioned worm blocks carefully adjusted. And I don't try to get backlash out! That is overdone by most people and even the factories.

Mark Christensen


Re: ESP8266 ESP-01 and external antenna

 


Found here 
https://www.mentebinaria.com.br/forums/topic/764-lab-01-esp8266-esp-01-pigtail-antena/


Re: Calculations needed for spur gear drive

Tom Gideon
 

Great!!

Thanks,
Tom

On Jul 22, 2021, at 9:24 AM, Khalid Baheyeldin <kbahey@...> wrote:

Gear pitch is not important as long as both gears are the same.

The spreadsheet has two RATIOS since most mounts have two stages of reductions.
If your mount only has one gear reduction stage, then just enter 1 in the other.

If your mount has 13 teeth to 217 teeth, and nothing else, then use GR1 = 1,
and GR2 = 217/13 = 16.692.

This reduction is not enough even with a 400 step motor (0.9 deg), and 1/32 microsteps.
So you'd better use a geared motor, and enter that ratio in GR1.

For example with a 50:1 gearbox:

200, 32, 50, 16.692 = 14,837.333

If your goal is visual observing only, then less reduction may work.


Re: Calculations needed for spur gear drive

Khalid Baheyeldin
 

Gear pitch is not important as long as both gears are the same.

The spreadsheet has two RATIOS since most mounts have two stages of reductions.
If your mount only has one gear reduction stage, then just enter 1 in the other.

If your mount has 13 teeth to 217 teeth, and nothing else, then use GR1 = 1,
and GR2 = 217/13 = 16.692.

This reduction is not enough even with a 400 step motor (0.9 deg), and 1/32 microsteps.
So you'd better use a geared motor, and enter that ratio in GR1.

For example with a 50:1 gearbox:

200, 32, 50, 16.692 = 14,837.333

If your goal is visual observing only, then less reduction may work.


Re: Setting backlash Question

Henk Aling
 

On Wed, Jul 7, 2021 at 01:02 PM, Khalid Baheyeldin wrote:
There is a simpler way to adjust backlash than what is in the Wiki.
No calculations needed ...

Basically, during daylight, use a faraway stationary terrestrial object.
For example a communication tower, a nail on a neighbour's chimney, or something like that.

Start OnStep normally, then slew to that object.
Turn off tracking.
Now using trial and error, try to refine how the object is centered when you move E and W.
If it jumps, then the backlash value is too high, reduce it.
If it lags, then the backlash value is too low, increase it.
Keep doing this until you don't observe any jump or lag when you reverse direction.

Repeat with N and S buttons for the other axis.
I like that, and will try it myself.  However backlash may not be the same for each target.  Backlash due to a gearbox will likely be constant but backlash due to a non-round cog wheel or play in the RA and DEC axes, which every gear-based mount has, will depend on the position of the target in space and time.  It's best to just focus on the gearbox if possible and compensate for that part if you have a controller that allows it.  Or use stepper motors that don't require a gearbox.  But then you have to deal with noise as a result of the low torque, which I am looking into now.


Re: Backslash training function

Khalid Baheyeldin
 

Try the simpler day time backlash adjustment procedure that I described here.
If you have a camera with Live View zoom function, or high power eyepieces, it will be better.


Backslash training function

 

Hi all,

I have found a procedure for backslash adjusting here (https://onstep.groups.io/g/main/wiki/20943) but it requires Polaris star. I live in South hemisphere and cannot use Polaris here. Could I use a ground target instead?

Can a Backslash Training (BT) function be implemented in the web application? Maybe something similar to PA or Autostar Train Drive. Using some star and buttons to move the star to a target and let the system calculate the backslash?

Cheers,
Andre


Re: Question on Interfaces to OnStep

 

Hi,
Thanks but the ESP-01 has a different PCB antenna layout.


Re: Question on Interfaces to OnStep

Dave Schwartz
 

I came across this a while ago. It should apply to ant WiFi module with the wiggly-trace antenna.

https://www.instructables.com/External-Antenna-for-ESP8266/

On 2021-07-22 8:56 a.m., andre_moutinho wrote:
Hi,

I want to solder an antenna connector in the ESP-01 module. Still looking for somewhere that explain how to do it. The ESP-1 PCB antenna is different from the WeMos D1 modules pcb antenna.

Best
Andre


Re: Question on Interfaces to OnStep

 

Hi,

I want to solder an antenna connector in the ESP-01 module. Still looking for somewhere that explain how to do it. The ESP-1 PCB antenna is different from the WeMos D1 modules pcb antenna.

Best
Andre


Re: Can't get less than 1" total RMS

Henk Aling
 

On Wed, Jul 21, 2021 at 11:35 PM, Alexander Varakin wrote:

Given that the stars are round, I think the mount is not the culprit. 

I hope you realize that you are imaging at 0.56'' per pixel and that is not easy.

Possible culprits most likely are
1. Poor seeing
2. Poor focus. How do you focus ?
3. Poor optics


Yes, I use a lot of sharpening methods in PI - deconvolution and others.

Can you install demo version of PI and do DynamicPSF on your stars and share results?

Then I can compare with my results. 

The seeing may have been poor with the very warm days we had here.  I took an image tonight, about 40x60s subs with recycled biases and flats.  Guiding was ddone mostly with Ekos, several with PHD2, both multi-star.  Ekos seemed to guide better so I went back to that.  I did not counterbalance enough in RA because I wanted to play with loose clutches.  As a result the stars are oblong in RA but not too bad.  The total RMS was pretty bad, 1.5" RMS.  You can tell that the stars are blurry.  Here is a link:  Losmandy_users@groups.io | Photo .  This is on another IO board so just in case you can't see it, here it is included (at poor resolution, I don't know how to preserve it).  I will get a PI teaser subscription later but not now because in a week I will go on vacation so I won't get enough time out of it.  I focus with an autofocuser in Ekos, this works quite well.  I collimated the OTA before I started.  The Newt has a Paracorr II CC.  The optics are fine.



Re: Focuser for MaxEsp3

Ken Hunter
 

You can caarefully cut away the connecter, unsolder the pins 1 at a time and install the pins like I did in my build.


Re: Can't get less than 1" total RMS

Alexander Varakin
 

Given that the stars are round, I think the mount is not the culprit. 

I hope you realize that you are imaging at 0.56'' per pixel and that is not easy.

Possible culprits most likely are
1. Poor seeing
2. Poor focus. How do you focus ?
3. Poor optics


Yes, I use a lot of sharpening methods in PI - deconvolution and others.

Can you install demo version of PI and do DynamicPSF on your stars and share results?

Then I can compare with my results. 


Re: SHC with oled 2.4" display and bluetooh communication (ESP32 wireless)

Tong
 

Hi Gildo Bosi

Do you have the schematic diagram and the specific manufacturing method?


ESP8266 ESP-01 and external antenna

 

Hi all,

I am finishing my EM-10 onstep modification (PCBMIN1) and I am planing to have a metal face plate so the antenna need to be external.

Does anyone here have soldered an external antenna connector into the ESP-01 module?

Thanks
Andre


Re: Can't get less than 1" total RMS

Henk Aling
 

Here's a nice explanation of how the holding torque plummets with increasing microstepping that are probably not noticeable, https://www.ti.com/lit/pdf/sloa293 .  I would not be surprised if those $12 steppers of mine cause my problem.

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