Tracking w/ Passil 4 polar alignment


Wiggins, Rick
 

Hi group,
Would someone comment on the Mach1 tracking capability with only visual polar alignment using the PASILL4.
I setup and aligned on Polaris and second star. I was using Cassidy double bar with two cameras on either side of the mount center. My 400mm lens and Canon RA were used to capture images. I got about 30% smearing of the stars at 25 sec exposures. I seem to recall doing better than this in the past; however, I’m usually using autoguider, so I’m not sure what I should expect. Thanks for any input.
Rick


Roland Christen
 


I setup and aligned on Polaris and second star.
That routine is not good enough for polar alignment for imaging. You will either need to use a polar scope or other precision polar align method. You will also need to have a good PE correction curve loaded and turned on in order to get good RA tracking.

Rolando


-----Original Message-----
From: Wiggins, Rick <rickwiggins@...>
To: main@ap-gto.groups.io
Sent: Tue, Jul 21, 2020 11:06 am
Subject: [ap-gto] Tracking w/ Passil 4 polar alignment

Hi group,
Would someone comment on the Mach1 tracking capability with only visual polar alignment using the PASILL4.
I setup and aligned on Polaris and second star. I was using Cassidy double bar with two cameras on either side of the mount center. My 400mm lens and Canon RA were used to capture images. I got about 30% smearing of the stars at 25 sec exposures. I seem to recall doing better than this in the past; however, I’m usually using autoguider, so I’m not sure what I should expect. Thanks for any input.
Rick


Wiggins, Rick
 

Hi Roland,
I did setup using the pasill4 polar scope and got good alignment on the two stars through the polar scope. I did not use a PE curve. Do you think slight smearing in 25 secs given that rough setup is reasonable or should it be better?
Thanks, Rick


Christopher Erickson
 

Depending on the lens focal lengths, personally I have found polar alignments with a PASILL4 to be more than accurate enough for astrophotography with SLR's ranging up to 30 minute exposures for wide fields.

Could be flexure someplace. If both cams show the same defects then it is something they both have in common.

Long cam lenses can exhibit a lot of flexure and sag, depending on how and where they are attached to the plate. And on their design and quality.

Turn off image stabilization too. It often has trouble with very dim scenes. And turn off autofocus, of course.

I hope this helps.

-Christopher Erickson
Observatory engineer
Waikoloa, HI 96738
www.summitkinetics.com
   


On Tue, Jul 21, 2020, 7:59 AM Wiggins, Rick <rickwiggins@...> wrote:
Hi Roland,
I did setup using the pasill4 polar scope and got good alignment on the two stars through the polar scope. I did not use a PE curve. Do you think slight smearing in 25 secs given that rough setup is reasonable or should it be better?
Thanks, Rick


Roland Christen
 

Even if the polar alignment is spot on you will need to use a PEM curve.  I'm guessing here because you did not provide enough information to go on. For instance, what direction did the trailing go, where in the sky did you image. There is no information on how the scope is being held, or the camera, or whether there is focuser sag. Lots of things can add up to give poor results.

Rolando



-----Original Message-----
From: Wiggins, Rick <rickwiggins@...>
To: main@ap-gto.groups.io
Sent: Tue, Jul 21, 2020 12:58 pm
Subject: Re: [ap-gto] Tracking w/ Passil 4 polar alignment

Hi Roland,
I did setup using the pasill4 polar scope and got good alignment on the two stars through the polar scope. I did not use a PE curve. Do you think slight smearing in 25 secs given that rough setup is reasonable or should it be better?
Thanks, Rick


Christopher Erickson
 

And for FWIW, I have a big, heavy/1.5kg+ (and sharp!) Nikkor 80-400mm AF-S ED zoom lens and if I want to try to image the sky with it, I have to add a Losmandy DVR108 Guide Scope ring to the plate, near the front end of the lens to keep it rigid and stable. The thing will sag/flex/shift quite a bit under its own weight when mounted on it's integral tripod shoe. I assume there are a lot of floating parts inside of that big zoom lens, fighting gravity. If I am using two or more cams on a long plate, I have the telephoto set up rigidly with a secondary lens support and the cams with shorter lenses go on ball heads on the plate. Most ball-heads have a lot of flex so I only put 58mm or shorter lenses on them. My favorite lenses for the second and third cams are 20mm ultra-wide and a 10mm fisheye.

I hope this helps.

Virus-free. www.avg.com


On Tue, Jul 21, 2020 at 8:27 AM uncarollo2 <chris1011@...> via groups.io <chris1011=aol.com@groups.io> wrote:
Even if the polar alignment is spot on you will need to use a PEM curve.  I'm guessing here because you did not provide enough information to go on. For instance, what direction did the trailing go, where in the sky did you image. There is no information on how the scope is being held, or the camera, or whether there is focuser sag. Lots of things can add up to give poor results.

Rolando



-----Original Message-----
From: Wiggins, Rick <rickwiggins@...>
To: main@ap-gto.groups.io
Sent: Tue, Jul 21, 2020 12:58 pm
Subject: Re: [ap-gto] Tracking w/ Passil 4 polar alignment

Hi Roland,
I did setup using the pasill4 polar scope and got good alignment on the two stars through the polar scope. I did not use a PE curve. Do you think slight smearing in 25 secs given that rough setup is reasonable or should it be better?
Thanks, Rick