Another newbie with PA issues

Using SharpCap's Polar Alignment feature
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Muskoka
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Another newbie with PA issues

Post by Muskoka »

Hello all, new guy here. Received a Svbony Sv305 camera, and Svbony Sv165 guide scope yesterday, so this was my first time using this equipment.

Without a long story, I purchased the Pro version so I could try to polar align with this setup. The camera connected fine to my laptop, and after playing with some of the camera settings I was getting 25+ detected stars, 15 used stars, but it would never solve. Before starting I did my usual polar align through the polar scope on my EQM-35 Pro, so I was very close to aligned before even starting up Sharpcap.

After this unable to solve went on for perhaps an hour, with me trying different settings, I refocused the guide scope using a 25mm eye piece just to make sure it was fine. After that I put the camera back in place

Again, Sharpcap was detecting 25+ stars, was using 15, but it still would not solve. After trying for over 2.5 hours I finally gave up, and shut everything down for the night.

I tried the troubleshooting steps, which didn't really change anything, the camera was already seeing lots of stars. I'm not sure what else to try to get it to solve.
Sky-Watcher 200p - Meade 390 - ZenithStar Z61 - Star Adventurer 2i - EQM-35 Pro - Canon T3i Unmodded - SvBony Sv305 - SvBony Sv165 Guide
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oopfan
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Re: Another newbie with PA issues

Post by oopfan »

I looked up the specs of your camera and guide scope. Your field-of-view is large enough. Next time you are out, can you capture a singe PNG image? I'll download and plate solve it at nova.astrometry.net. I want to make sure that your scope is pointing within 5 degrees of the pole.

Brian
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Re: Another newbie with PA issues

Post by Muskoka »

oopfan wrote: Wed Apr 14, 2021 4:16 pm I looked up the specs of your camera and guide scope. Your field-of-view is large enough. Next time you are out, can you capture a singe PNG image? I'll download and plate solve it at nova.astrometry.net. I want to make sure that your scope is pointing within 5 degrees of the pole.

Brian
Thanks for the feedback Brian. I will do that next time I'm out, hopefully tonight.

In the meantime I took these screenshots of a tree top about 200' away, after changing the guide scope focus of course. Just focused enough so you could see the tree. You can see in the images where the guide cam is pointed in relation to my main imaging camera (the BYEOS image). Last night Polaris was dead center (very close to center on the camera lcd) in the imaging camera, so I don't know if you can tell from these images if my guide scope was close enough. There's no adjustment with the guide scope mount, other than forward / back, it is what it is. I also included a picture of my set up.
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Sky-Watcher 200p - Meade 390 - ZenithStar Z61 - Star Adventurer 2i - EQM-35 Pro - Canon T3i Unmodded - SvBony Sv305 - SvBony Sv165 Guide
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Re: Another newbie with PA issues

Post by admin »

Hi,

Brian is right to suggest checking the pointing using plate solving - if you are detecting 25 stars and are within 5 degrees of the pole then the plate solving for polar alignment should kick in rapidly. I suppose it's possible that the tree may be blocking out enough of the frame to cause problems, but I know others get reasonable results with polaris only just in view.

Anyway, if you haven't already, read the troubleshooting page : https://www.sharpcap.co.uk/sharpcap/fea ... leshooting

If that doesn't help then grab both an image from the camera ('Snapshot' button) and a screenshot and post them here and we can advise.

thanks,

Robin
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Re: Another newbie with PA issues

Post by Muskoka »

admin wrote: Wed Apr 14, 2021 6:17 pm Hi,

Brian is right to suggest checking the pointing using plate solving - if you are detecting 25 stars and are within 5 degrees of the pole then the plate solving for polar alignment should kick in rapidly. I suppose it's possible that the tree may be blocking out enough of the frame to cause problems, but I know others get reasonable results with polaris only just in view.

Anyway, if you haven't already, read the troubleshooting page : https://www.sharpcap.co.uk/sharpcap/fea ... leshooting

If that doesn't help then grab both an image from the camera ('Snapshot' button) and a screenshot and post them here and we can advise.

thanks,

Robin
Hi Robin. The only reason I took the picture of the tree was to show "how close" the two scopes are in relation to each other, with respect to a target. Surely if Polaris was in the center of either of these images, both scopes / cameras would be looking at almost exactly the same section of the sky. I have no trees blocking my view in any direction, again, those images I posted are only for reference, hope that makes sense?

My skies are Bortle 3 as well, so light pollution is never an issue. Nearest neighbors are 300' away. The only reason I've come here seeking help is as far as I'm concerned it shouldn't have been an issue. For close to 2.5 hours the camera had 25+ stars detected, using 15, to me that should have worked without issue, yet it didn't.

The system / software simply would not solve, with that many stars, pointing directly at Polaris. Also don't forget, I had already polar aligned as I always have, using the polar scope as I mentioned in my first post. So I know I was pointed where I needed to be, the system was already polar aligned. I was "trying" with the software to get it even closer, but for some reason it just wouldn't solve.

Should also add, prior to purchasing the guide scope and camera, I had watched at least 3 videos on YouTube on how it "should work" with Sharpcap, so I wasn't trying this completely blind. It looks simple enough in the videos, so I assumed it wouldn't be a issue at this end, again, with a full screen of stars surrounding Polaris.
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Re: Another newbie with PA issues

Post by oopfan »

Also, can you do the following:
Click "Tools -> Plate Solve". It employs a different plate solving routine.

If successful it will show the solution coordinates in the status bar. Click the "Copy" button to copy it to the clipboard. Save it somewhere so that you can post it here later.

If unsuccessful then slew anywhere at around 45 degrees declination. Try "Tools => Plate Solve" again. If it works, copy to the clipboard and paste here. If it doesn't work, just report back.

Brian
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Re: Another newbie with PA issues

Post by Muskoka »

oopfan wrote: Wed Apr 14, 2021 8:05 pm Also, can you do the following:
Click "Tools -> Plate Solve". It employs a different plate solving routine.

If successful it will show the solution coordinates in the status bar. Click the "Copy" button to copy it to the clipboard. Save it somewhere so that you can post it here later.

If unsuccessful then slew anywhere at around 45 degrees declination. Try "Tools => Plate Solve" again. If it works, copy to the clipboard and paste here. If it doesn't work, just report back.

Brian
Thanks again Brian. Just so I'm sure, you want me to try "plate solve" instead of "polar align" while I'm in the home position, and pointing at Polaris? As a first attempt / test?
Sky-Watcher 200p - Meade 390 - ZenithStar Z61 - Star Adventurer 2i - EQM-35 Pro - Canon T3i Unmodded - SvBony Sv305 - SvBony Sv165 Guide
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Re: Another newbie with PA issues

Post by oopfan »

I'd like you to try PA again, but there is no reason to spend hours trying. Run "Tools -> Plate Solve" as just another test. I'm curious to know where the guide cam is pointing, and whether SC can successfully plate solve the polar region.

Also, what exposure and gain are you using? Most people here don't have Bortle 3 skies. I'm wondering if dark skies are getting in the way. I think it might be helpful to try different exposures and gains.

I start PA when the Sun drops below 12 degrees below the horizon. The skies are still a little light. I'm at Bortle 5. I use a 2-second exposure with 30% gain. I have an Altair 290M mono cam and a 50mm f/3.2 guide scope. Most times, SC detects far fewer stars than what you reported in your original post.

You might want to try dropping the exposure so that the number of stars detected is 10 to 15.

Brian
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Re: Another newbie with PA issues

Post by Muskoka »

Thanks to everyone that offered help.

Success, sort of. It was a focus issue all along. I tried some exposure and gain setting that were suggested, and I suddenly saw this big blob on the screen. Knew right away it had to be Polaris. Loosened the collar, started winding the lens in, and in, and in, then suddenly Sharpcap solved what it was trying to solve, a miracle. I measured the gap between the lock ring and the lens last night when the focus was perfect with a 25mm eyepiece, 27mm. When I finally reached focus, or close to it on the screen tonight, the gap was only 19mm. Never thought it would need to move that far. It must have just been noise that it was detecting last night, although some of them looked like stars to me. But there's no way they could have been with that much of a change in focus.

Anyways, then the clouds rolled in, and spoiled the fun. I never got a chance to finish. I had just done the 90 degree rotate thing, and it just sat there, couldn't solve. I'm looking everything over, what now, scratched my head for a minute, finally decided to look up, and saw what the issue was.
Sky-Watcher 200p - Meade 390 - ZenithStar Z61 - Star Adventurer 2i - EQM-35 Pro - Canon T3i Unmodded - SvBony Sv305 - SvBony Sv165 Guide
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Re: Another newbie with PA issues

Post by admin »

Hi,

glad to hear that you located and fixed the cause of the problem. Hope you get some clear sky to try again soon!

Robin
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