Date
1 - 20 of 149
Eggy Stars with Polar Axis Correction
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Last night I took a 10 minute test sub and the stars were slightly egg shaped. I was chatting with Bill Long and he told me that he saw something similar with Polar Axis Correction enabled. Sure enough, I disabled this in the Pointing Model and my next test sub had perfect pinpoint round stars.
Thought I would pass this on in case someone else has seen this and also to see if there is a setting somewhere else that might be causing a conflict with PA correction. I polar aligned using sharpcap and use a weather station for local conditions. PA error after making my model was 20 arcseconds for elevation and 30 arcseconds for azimuth as reported by APCC. Thanks BILL! |
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Ray Gralak
Chris,
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I'll have to investigate this, but I need some information: 1. How many points were in the model? 2. Was this an all-sky or dec-arc model (through NINA)? 3. Which pier side was affected(i.e., eggy stars)? East, West, or both? 4. What was the approximate location in the sky? (e.g. Dec=30, Hour Angle = 1) Thanks, -Ray -----Original Message----- |
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On Mon, Jul 18, 2022 at 09:21 AM, Ray Gralak wrote:
Chris,Ray, It was a 180 point all sky model in APPM. I only use NINA for the camera connection. I'll attached the map and results for reference. I was pointing at Cygnus as it rose in the East, at approx 75 degrees altitude. Thank you very much. |
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Ray Gralak
Okay thanks. Where any of the "eggy" images with counterweight-up?
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-Ray -----Original Message----- |
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No. Counterweight down.
And it's not a huge sample set. I was just testing and chatting with BILL. I bring it up because for both of us disabling PA correction seems to have resolved it. |
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Bill Long
One thing I didn't try, but will if I see this again, is to try turning off refraction correction.
From: main@ap-gto.groups.io <main@ap-gto.groups.io> on behalf of Chris White <chris.white@...>
Sent: Monday, July 18, 2022 6:42 AM To: main@ap-gto.groups.io <main@ap-gto.groups.io> Subject: Re: [ap-gto] Mach2 and Eggy Stars with Polar Axis Correction No. Counterweight down.
And it's not a huge sample set. I was just testing and chatting with BILL. I bring it up because for both of us disabling PA correction seems to have resolved it. |
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Oh, I didn't put this in earlier. We are both using Mach2 Mount.
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Michael Freeberg
Hi Chris,
Just curious, but where in APCC do you enable/disable Polar axis Correction. Thanks, Mike |
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On Mon, Jul 18, 2022 at 09:57 AM, Michael Freeberg wrote:
Hi Chris,On the pointing model tab. See attached. |
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Ray Gralak
One more question, Chris:
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Did you try enabling Dec Arc tracking? -Ray -----Original Message----- |
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On Mon, Jul 18, 2022 at 10:30 AM, Ray Gralak wrote:
One more question, Chris: Good question. I can't remember If the box is checked. I'll confirm when I get home tonight. I have never created a dec arc model with apcc in case that matters. |
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Bill Long
In the case in which I had a repro Dec Arc was in use.
From: main@ap-gto.groups.io <main@ap-gto.groups.io> on behalf of Chris White <chris.white@...>
Sent: Monday, July 18, 2022 7:43 AM To: main@ap-gto.groups.io <main@ap-gto.groups.io> Subject: Re: [ap-gto] Mach2 and Eggy Stars with Polar Axis Correction On Mon, Jul 18, 2022 at 10:30 AM, Ray Gralak wrote:
One more question, Chris: Good question. I can't remember If the box is checked. I'll confirm when I get home tonight. I have never created a dec arc model with apcc in case that matters. |
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Ray Gralak
Chris,
There is no specific option to create a Dec Arc Tracking model. It is implemented using an entirely different algorithm that applies only to tracking and co-exists with the All-Sky model. Although it seems common that people are using it for tracking a single target, if you use many points across the sky, the Dec Arc algorithm can be used over the entire portion of the sky mapped with points. That way of using it is probably best for permanent installations.Did you try enabling Dec Arc tracking?Good question. I can't remember If the box is checked. I'll confirm when I get home tonight. BTW, the Dec Arc algorithm does not use the pointing terms, so tracking is unaffected by disabling the polar alignment checkboxes. -Ray |
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Ray Gralak
Hi Bill,
Are you sure that iwas the case? Dec Arc tracking does not use the pointing terms at all. It's an algorithm completely independent of the terms. Only pointing correction will use the pointing terms when Dec Arc tracking is enabled. -Ray |
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Ray Gralak
Dec Arc tracking does not use the pointing terms at all. It's an algorithmThat said, there should be at least 5 points mapped to each declination, although more points at each declination will increase tracking accuracy. -Ray -----Original Message----- |
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Bill Long
I'm positive Dec Arc was in use, that's the only method I use now.
From: main@ap-gto.groups.io <main@ap-gto.groups.io> on behalf of Ray Gralak <iogroups@...>
Sent: Monday, July 18, 2022 8:24 AM To: main@ap-gto.groups.io <main@ap-gto.groups.io> Subject: Re: [ap-gto] Mach2 and Eggy Stars with Polar Axis Correction Hi Bill,
> > In the case in which I had a repro Dec Arc was in use. Are you sure that iwas the case? Dec Arc tracking does not use the pointing terms at all. It's an algorithm completely independent of the terms. Only pointing correction will use the pointing terms when Dec Arc tracking is enabled. -Ray |
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Bill Long
Interesting. Then something else was at play in my case. This is good information to have.
From: main@ap-gto.groups.io <main@ap-gto.groups.io> on behalf of Ray Gralak <iogroups@...>
Sent: Monday, July 18, 2022 8:22 AM To: main@ap-gto.groups.io <main@ap-gto.groups.io> Subject: Re: [ap-gto] Mach2 and Eggy Stars with Polar Axis Correction Chris,
>> Did you try enabling Dec Arc tracking? > Good question. I can't remember If the box is checked. I'll confirm when I get home tonight. > I have never created a dec arc model with apcc in case that matters. There is no specific option to create a Dec Arc Tracking model. It is implemented using an entirely different algorithm that applies only to tracking and co-exists with the All-Sky model. Although it seems common that people are using it for tracking a single target, if you use many points across the sky, the Dec Arc algorithm can be used over the entire portion of the sky mapped with points. That way of using it is probably best for permanent installations. BTW, the Dec Arc algorithm does not use the pointing terms, so tracking is unaffected by disabling the polar alignment checkboxes. -Ray |
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Linwood Ferguson
On Mon, Jul 18, 2022 at 11:28 AM, Ray Gralak wrote:
That said, there should be at least 5 points mapped to each declination, although more points at each declination will increaseDo you have advice on how far apart the arcs should be, let's say you do three arcs with one centered on the target's DEC, should you stay close (1 degree), or go further out? And is three a good number? I still get more drift when I experiment than I expect, and have tried 3 arcs of 1 and of 2 degrees. Clearly more points are better but where is it best to put them? Linwood |
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Ray Gralak
Interesting. Then something else was at play in my case. This is good information to have.If you watch the RA and Dec rate values in APCC's "Tracking Correction Status" group box (on the Pointing Model tab), which shows the real-time tracking rate values sent to the mount, you can observe what happens when you enable/disable Dec-Arc Tracking and any of the pointing terms. -Ray |
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Bill Long
It Dec Arc using the refraction correction a setting at all or is that also a non factor?
From: main@ap-gto.groups.io <main@ap-gto.groups.io> on behalf of Ray Gralak <iogroups@...>
Sent: Monday, July 18, 2022 8:45 AM To: main@ap-gto.groups.io <main@ap-gto.groups.io> Subject: Re: [ap-gto] Mach2 and Eggy Stars with Polar Axis Correction > Interesting. Then something else was at play in my case. This is good information to have.
If you watch the RA and Dec rate values in APCC's "Tracking Correction Status" group box (on the Pointing Model tab), which shows the real-time tracking rate values sent to the mount, you can observe what happens when you enable/disable Dec-Arc Tracking and any of the pointing terms. -Ray |
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