Re: Mach2 - Elongated stars


Roland Christen
 


One issue I am facing with Mach2 guiding is that I am not quite sure why my RA correction is mostly one direction. I can understand DEC correction in one direction due to polar alignment error, but RA should be random. Is this normal?
If your guiding is in one direction it simply means that you either have not perfect polar alignment or you are guiding in that part of the sky where the stars are moving slower than sidereal. This is caused by atmospheric refraction, and it is quite normal.

Rolando

-----Original Message-----
From: yanzhe liu <liuyanzhe@...>
To: main@ap-gto.groups.io
Sent: Sat, Mar 27, 2021 11:51 pm
Subject: Re: [ap-gto] Mach2 - Elongated stars

Rolando,

I am still digging into why my stars are elongated, currently I am focusing on collimation and possible fan noise. When I looked carefully into my old subs (with another mount), I got elongated stars too, but because the stars were larger (ie, guiding performance was not as good as Mach2) it looked rounder.

One issue I am facing with Mach2 guiding is that I am not quite sure why my RA correction is mostly one direction. I can understand DEC correction in one direction due to polar alignment error, but RA should be random. Is this normal?
Screen Shot 2021-03-27 at 9.48.16 PM.png

Yanzhe

On Fri, Mar 12, 2021 at 3:41 PM Bill Long <bill@...> wrote:
I did have my scope well-balanced in both axis. I guided it for a short while as a test for a 5 min sub (image below) then turned it off and went unguided and noticed the stars were of identical quality, so I went unguided for the evening instead.




From: main@ap-gto.groups.io <main@ap-gto.groups.io> on behalf of yanzhe liu <liuyanzhe@...>
Sent: Friday, March 12, 2021 2:41 PM
To: main@ap-gto.groups.io <main@ap-gto.groups.io>
Subject: Re: [ap-gto] Mach2 - Elongated stars
 
I have been using mach1 and 1100 prior to mach2. I knew I changed mount to mach2 in ascom driver.

Let me try again with balanced DEC, as suggested by Roland, to see if the issue is going away.  

On Thu, Mar 11, 2021 at 7:38 AM Ray Gralak <iogroups@...> wrote:
Yanzhe,

> I am able to run "AP Log Zipper", there are 2 files shown in the app: ap.ini and Setting.apdb, however both were dated
> 12/29/2018. Maybe I did not enable ASCOM log.

Hmmm... that is not the default. Did you happen to use this computer with another A-P mount in the past?

Since it is probably a small file, please attach that zip file to a post. It's worth checking the settings to see if anything stands out as an incorrect setting.

BTW, can you also provide a dropbox or google drive link to one of the single raw FITS images with the elongated stars? It's important that it is an unprocessed image and not a jpeg or stacked with other images.

Thanks,

-Ray

> -----Original Message-----
> From: main@ap-gto.groups.io [mailto:main@ap-gto.groups.io] On Behalf Of yanzhe liu
> Sent: Wednesday, March 10, 2021 10:36 PM
> To: main@ap-gto.groups.io
> Subject: Re: [ap-gto] Mach2 - Elongated stars
>
> Ray,
>
> I am able to run "AP Log Zipper", there are 2 files shown in the app: ap.ini and Setting.apdb, however both were dated
> 12/29/2018. Maybe I did not enable ASCOM log.
>
> Yanzhe
>
> On Sun, Mar 7, 2021 at 7:37 PM Ray Gralak <iogroups@...> wrote:
>
>
>       Yanhze,
>
>       > Where is ASCOM driver log? I dont use APCC, I use SGPro.
>
>       The AP V2 ASCOM driver, which you must use with SGPro, comes with a log zipper utility called "AP Log
> Zipper". You should be able to find it from the Windows start menu by typing that name. The utility will grab the log files
> for X number of days in the past. If you can't find it, you probably didn't install it when you installed the AP V2 driver. In
> that case, just reinstall the AP V2 driver and select the option to install it.
>
>       BTW, you can use APCC with SGPro. In fact, it is recommended. An APCC Pro license comes with your
> Mach2 mount, but you must contact A-P to get it.
>
>       -Ray
>
>
>       > -----Original Message-----
>       > From: main@ap-gto.groups.io [mailto:main@ap-gto.groups.io] On Behalf Of yanzhe liu
>       > Sent: Sunday, March 7, 2021 4:19 PM
>       > To: main@ap-gto.groups.io
>       > Subject: Re: [ap-gto] Mach2 - Elongated stars
>       >
>       > Ray,
>       >
>       > Where is ASCOM driver log? I dont use APCC, I use SGPro.
>       >
>       > Yanzhe
>       >
>       > On Sun, Mar 7, 2021 at 10:45 AM Ray Gralak <iogroups@...> wrote:
>       >
>       >
>       >       Hi Yanzhe,
>       >
>       >       Can you zip and post your PHD2 logs, as well as APCC/AP V2 ASCOM driver logs?
>       >
>       >       There might be something useful there.
>       >
>       >       -Ray
>       >
>       >       > -----Original Message-----
>       >       > From: main@ap-gto.groups.io [mailto:main@ap-gto.groups.io] On Behalf Of yanzhe liu
>       >       > Sent: Sunday, March 7, 2021 10:12 AM
>       >       > To: main@ap-gto.groups.io
>       >       > Subject: Re: [ap-gto] Mach2 - Elongated stars
>       >       >
>       >       > Roland,
>       >       >
>       >       > I will check my mount serial number later as I just packed everything due to rain forecast.
>       >       >
>       >       > My camera's orientation was 0/180 degree, so I assume top to bottom elongation would be DEC.
>       >       >
>       >       > I dont have any picture of my setup, I just tore it down since it will be rainy this week. My setup is
>       >       > FSQ106+OAG+16803, image scale is 3.5".
>       >       > I was imaging Rosetta Nebula, after it was just past meridian for 2-3 hours.
>       >       >
>       >       > I used PHD2 drift for PA, it reported <5' PA error, I am waiting for polemaster adapter so I can confirm I
> get
>       > good PA
>       >       > next time.
>       >       >
>       >       > DEC was out of balance because my setup was rear end heavy, if it was in balance position then I
> could
>       > not rotate
>       >       > my CCD in all directions. My guess is that the DEC balance was off by less than 1lb. In the next test, I
> can
>       > balance
>       >       > DEC to see if the issue still exists.
>       >       >
>       >       > My suspicion is that if DEC balance is off, then DEC might creep under gravity, even PA is perfect. So
> you
>       > might
>       >       > see DEC continually drift  then gets corrected by PHD2 periodically.
>       >       >
>       >       > Yanzhe
>       >       >
>       >       > On Sun, Mar 7, 2021 at 9:35 AM Roland Christen via groups.io <chris1011=aol.com@groups.io> wrote:
>       >       >
>       >       >
>       >       >       Couple of questions:
>       >       >
>       >       >
>       >       >       1 - what's the mount's serial number
>       >       >       2 - which axis is the elongation
>       >       >       3 - which direction was the scope pointing (RA-Dec)
>       >       >       4 - what scope and focal length or what is the arc sec per pixel.
>       >       >       5 - do you have a picture of your setup?
>       >       >
>       >       >
>       >       >
>       >       >       One comment about balance - it should be easy for you to completely balance the scope with the
>       > clutches
>       >       > loose. Can you estimate how many lb out of balance your scope is in Dec? Normally i would not think
> this
>       > would
>       >       > have any effect, but doesn't hurt to check this.
>       >       >
>       >       >
>       >       >
>       >       >       Roland Christen
>       >       >       Astro-Physics Inc.
>       >       >
>       >       >
>       >       >
>       >       >
>       >       >       -----Original Message-----
>       >       >       From: yanzhe liu <liuyanzhe@...>
>       >       >       To: mailto:main@ap-gto.groups.io
>       >       >       Sent: Sun, Mar 7, 2021 12:44 am
>       >       >       Subject: [ap-gto] Mach2 - Elongated stars
>       >       >
>       >       >
>       >       >       Testing new mach2 for a couple of nights. It works great out of the box and I am very pleased.
>       >       >
>       >       >       One issue bothering me is that I got slightly elongated stars across the entire image (15min Ha sub).
>       >       >       The exact same telescope/CCD were used with another mount and stars were round, I am
> wondering
>       > what I
>       >       > should check (I think there was due to some setup issue, but I could not figure it out).
>       >       >       - Used OAG for guiding, so there should not be any flexure.
>       >       >       - CCD orientation was 0/180 degree. The stars were elongated top to bottom.
>       >       >       -  I did polar alignment with PHD2 drift align. PA error should be < 5'. The field rotation of each sub
> is
>       > ~0.01
>       >       > degree, much larger than the other system (but elongated stars do not look like field rotation, they were
>       > same
>       >       > across the image)
>       >       >       - Both RA and DEC guiding curves looked smooth, had similar RMS. DEC correction was mainly to
>       > one
>       >       > direction.
>       >       >       - DEC balance was slightly off, camera heavy. Is Mach2 DEC sensitive to this? Will the
> guiding/image
>       > be
>       >       > affected?
>       >       >
>       >       >       I dont think any of the above is of particular concern, except DEC balance. Any comment/help is
>       > appreciated.
>       >       >
>       >       >       --
>       >       >       Roland Christen
>       >       >       Astro-Physics
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--
Roland Christen
Astro-Physics

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