Topics

Weird tracking artifacts


Hemant Hariyani
 

Hello all,

I am using a Meade 16 inch f/8 (FL - 3250 mm) on AP1600 GTO with AE. I am seeing some weird tracking artifacts in my images. I cannot go beyond a minute or so unguided.

A couple of nights ago, I tried live stack of m57 with 30s sub exposures.

As you can see in m57_livestack.jpg, there seems to be a "wavy" drift in the image. I saved individual images (30s x 20) and after stacking in PixInsight, the same error is seen on noise (m57_stacked.jpg) - but the pattern is clearer because of smaller structures.

Each 30s exposure itself was just fine as you can see from cleaned up m57.jpg. Guiding was not enabled. If this was polar alignment error, I would have thought it'd follow a more linear drift.

Any ideas on what could be causing this?

Regards
Hemant





uncarollo2 <chris1011@aol.com>
 

Classic periodic error. Every mount has that to some extent (except for encoder mounts), is well known by imagers. Can be mostly eliminated with periodic error correction using a program like PEMPro - the gold standard of PE programs.

Rolando



-----Original Message-----
From: Hemant Hariyani <hemanthariyani@...>
To: main@ap-gto.groups.io <main@ap-gto.groups.io>
Sent: Sat, Jun 20, 2020 2:24 pm
Subject: [ap-gto] Weird tracking artifacts

Hello all,

I am using a Meade 16 inch f/8 (FL - 3250 mm) on AP1600 GTO with AE. I am seeing some weird tracking artifacts in my images. I cannot go beyond a minute or so unguided.

A couple of nights ago, I tried live stack of m57 with 30s sub exposures.

As you can see in m57_livestack.jpg, there seems to be a "wavy" drift in the image. I saved individual images (30s x 20) and after stacking in PixInsight, the same error is seen on noise (m57_stacked.jpg) - but the pattern is clearer because of smaller structures.

Each 30s exposure itself was just fine as you can see from cleaned up m57.jpg. Guiding was not enabled. If this was polar alignment error, I would have thought it'd follow a more linear drift.

Any ideas on what could be causing this?

Regards
Hemant





uncarollo2 <chris1011@aol.com>
 

By the way, the majority of the tracking error in your images is drift due to polar misalignment and the fact that you are not using a model. For such a large scope and long focal length you really cannot do unguided imaging unless you reduce the periodic error below 1 arc sec (can be done on the 1600), AND also make an extensive accurate all-sky model with APPM. Then you might be able to get 5 minutes or more unguided.

Rolando



-----Original Message-----
From: uncarollo2 <chris1011@...> via groups.io <chris1011@...>
To: main@ap-gto.groups.io <main@ap-gto.groups.io>
Sent: Sat, Jun 20, 2020 2:29 pm
Subject: Re: [ap-gto] Weird tracking artifacts

Classic periodic error. Every mount has that to some extent (except for encoder mounts), is well known by imagers. Can be mostly eliminated with periodic error correction using a program like PEMPro - the gold standard of PE programs.

Rolando



-----Original Message-----
From: Hemant Hariyani <hemanthariyani@...>
To: main@ap-gto.groups.io <main@ap-gto.groups.io>
Sent: Sat, Jun 20, 2020 2:24 pm
Subject: [ap-gto] Weird tracking artifacts

Hello all,

I am using a Meade 16 inch f/8 (FL - 3250 mm) on AP1600 GTO with AE. I am seeing some weird tracking artifacts in my images. I cannot go beyond a minute or so unguided.

A couple of nights ago, I tried live stack of m57 with 30s sub exposures.

As you can see in m57_livestack.jpg, there seems to be a "wavy" drift in the image. I saved individual images (30s x 20) and after stacking in PixInsight, the same error is seen on noise (m57_stacked.jpg) - but the pattern is clearer because of smaller structures.

Each 30s exposure itself was just fine as you can see from cleaned up m57.jpg. Guiding was not enabled. If this was polar alignment error, I would have thought it'd follow a more linear drift.

Any ideas on what could be causing this?

Regards
Hemant





Hemant Hariyani
 

Hello Roland,

Thanks a lot. That is interesting. So I guess this is PE with drift. I do have encoders on the mount though. Is it possible that encoders are not working?

Regards
Hemant

On Sat, Jun 20, 2020 at 2:29 PM uncarollo2 <chris1011@...> via groups.io <chris1011=aol.com@groups.io> wrote:
Classic periodic error. Every mount has that to some extent (except for encoder mounts), is well known by imagers. Can be mostly eliminated with periodic error correction using a program like PEMPro - the gold standard of PE programs.

Rolando



-----Original Message-----
From: Hemant Hariyani <hemanthariyani@...>
To: main@ap-gto.groups.io <main@ap-gto.groups.io>
Sent: Sat, Jun 20, 2020 2:24 pm
Subject: [ap-gto] Weird tracking artifacts

Hello all,

I am using a Meade 16 inch f/8 (FL - 3250 mm) on AP1600 GTO with AE. I am seeing some weird tracking artifacts in my images. I cannot go beyond a minute or so unguided.

A couple of nights ago, I tried live stack of m57 with 30s sub exposures.

As you can see in m57_livestack.jpg, there seems to be a "wavy" drift in the image. I saved individual images (30s x 20) and after stacking in PixInsight, the same error is seen on noise (m57_stacked.jpg) - but the pattern is clearer because of smaller structures.

Each 30s exposure itself was just fine as you can see from cleaned up m57.jpg. Guiding was not enabled. If this was polar alignment error, I would have thought it'd follow a more linear drift.

Any ideas on what could be causing this?

Regards
Hemant





uncarollo2 <chris1011@aol.com>
 

If the encoders are turned off, then yes, you will have PE. Drift is not something the encoders can fix.
We have a utility that allows you to turn the encoders on or off. Also you can do it in APCC. You have to, of course have the encoders plugged in, and that may not be the case. If they are not plugged in and operating, the mount will simply revert to non-encoder mode and display a but of PE. Check the encoders to see if the light is blue or green. If the light is not on or shows red, then the encoders are not plugged in, or not working.

Rolando



-----Original Message-----
From: Hemant Hariyani <hemanthariyani@...>
To: main@ap-gto.groups.io
Sent: Sat, Jun 20, 2020 3:02 pm
Subject: Re: [ap-gto] Weird tracking artifacts

Hello Roland,

Thanks a lot. That is interesting. So I guess this is PE with drift. I do have encoders on the mount though. Is it possible that encoders are not working?

Regards
Hemant

On Sat, Jun 20, 2020 at 2:29 PM uncarollo2 <chris1011@...> via groups.io <chris1011=aol.com@groups.io> wrote:
Classic periodic error. Every mount has that to some extent (except for encoder mounts), is well known by imagers. Can be mostly eliminated with periodic error correction using a program like PEMPro - the gold standard of PE programs.

Rolando



-----Original Message-----
From: Hemant Hariyani <hemanthariyani@...>
To: main@ap-gto.groups.io <main@ap-gto.groups.io>
Sent: Sat, Jun 20, 2020 2:24 pm
Subject: [ap-gto] Weird tracking artifacts

Hello all,

I am using a Meade 16 inch f/8 (FL - 3250 mm) on AP1600 GTO with AE. I am seeing some weird tracking artifacts in my images. I cannot go beyond a minute or so unguided.

A couple of nights ago, I tried live stack of m57 with 30s sub exposures.

As you can see in m57_livestack.jpg, there seems to be a "wavy" drift in the image. I saved individual images (30s x 20) and after stacking in PixInsight, the same error is seen on noise (m57_stacked.jpg) - but the pattern is clearer because of smaller structures.

Each 30s exposure itself was just fine as you can see from cleaned up m57.jpg. Guiding was not enabled. If this was polar alignment error, I would have thought it'd follow a more linear drift.

Any ideas on what could be causing this?

Regards
Hemant





Hemant Hariyani
 

Thank you once again Roland. Indeed my encoders were disabled - no idea how and when that happened? Can APCC update do this?

Enabling encoders from APCC did the trick - I do not see PE anymore. Still trailing but linear as expected. Trailing is minimal near zenith - quite a bit about 45 degrees down. I will build a model and give this a shot again - and may be autogude.

Regards
Hemant



On Sat, Jun 20, 2020 at 3:18 PM uncarollo2 <chris1011@...> via groups.io <chris1011=aol.com@groups.io> wrote:
If the encoders are turned off, then yes, you will have PE. Drift is not something the encoders can fix.
We have a utility that allows you to turn the encoders on or off. Also you can do it in APCC. You have to, of course have the encoders plugged in, and that may not be the case. If they are not plugged in and operating, the mount will simply revert to non-encoder mode and display a but of PE. Check the encoders to see if the light is blue or green. If the light is not on or shows red, then the encoders are not plugged in, or not working.

Rolando



-----Original Message-----
From: Hemant Hariyani <hemanthariyani@...>
To: main@ap-gto.groups.io
Sent: Sat, Jun 20, 2020 3:02 pm
Subject: Re: [ap-gto] Weird tracking artifacts

Hello Roland,

Thanks a lot. That is interesting. So I guess this is PE with drift. I do have encoders on the mount though. Is it possible that encoders are not working?

Regards
Hemant

On Sat, Jun 20, 2020 at 2:29 PM uncarollo2 <chris1011@...> via groups.io <chris1011=aol.com@groups.io> wrote:
Classic periodic error. Every mount has that to some extent (except for encoder mounts), is well known by imagers. Can be mostly eliminated with periodic error correction using a program like PEMPro - the gold standard of PE programs.

Rolando



-----Original Message-----
From: Hemant Hariyani <hemanthariyani@...>
To: main@ap-gto.groups.io <main@ap-gto.groups.io>
Sent: Sat, Jun 20, 2020 2:24 pm
Subject: [ap-gto] Weird tracking artifacts

Hello all,

I am using a Meade 16 inch f/8 (FL - 3250 mm) on AP1600 GTO with AE. I am seeing some weird tracking artifacts in my images. I cannot go beyond a minute or so unguided.

A couple of nights ago, I tried live stack of m57 with 30s sub exposures.

As you can see in m57_livestack.jpg, there seems to be a "wavy" drift in the image. I saved individual images (30s x 20) and after stacking in PixInsight, the same error is seen on noise (m57_stacked.jpg) - but the pattern is clearer because of smaller structures.

Each 30s exposure itself was just fine as you can see from cleaned up m57.jpg. Guiding was not enabled. If this was polar alignment error, I would have thought it'd follow a more linear drift.

Any ideas on what could be causing this?

Regards
Hemant