Not solving (have 15 stars used)

Using SharpCap's Polar Alignment feature
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mhectorgato
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Joined: Thu May 18, 2017 2:48 am

Not solving (have 15 stars used)

Post by mhectorgato » Sun May 21, 2017 2:11 am

Got my SSAG t play nice with SharpCap, and the clouds have cleared out. So I brought out my mount, got it configured, hoping to get PA with SharpCap.

Am having an issue of it not solving, despite what seems to be enough stars. One time it solved the first image, but it took many minutes (guestimating about 20). For the second image it was doing that again. I turned on the night mode, and it reset the session, thus it never completed.

Following the troubleshooting guide, I increased the exposure times, turned on NR and the gain. My laptop has 8GB and a i6500U processor.

I also tried with the test camera sample DSO image (orion's nebula) and a similar situation occurs, where it takes quite a while. I gave up waiting on it to see if it would solve. That fact that the sample image took so long, seems to rule out my camera.

Is there some silly mistake I am making? Is there anything I can do to speed up the process?

Thanks
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mhectorgato
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Re: Not solving (have 15 stars used)

Post by mhectorgato » Sun May 21, 2017 2:22 am

Here's the solved image 1 on my second attempt at giving it the time it needs.

Unforunately I accidentally shut down the app, so I never got image 2.

I restarted the process and am now at 10 minutes, and still not solved.

Thanks
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admin
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Re: Not solving (have 15 stars used)

Post by admin » Sun May 21, 2017 8:12 am

So the polar alignment plate solving will only work if you are already pointing within 5 degrees of the pole, so the Orion nebula test images will not solve no matter how long you wait! There are a couple of test images attached to this thread - viewtopic.php?f=13&t=132 - that you can use for testing polar alignment with the 'Test Camera 1'.

Back to doing it for real - The first attempt to solve may be a bit slow since it builds the plate solving index initially, but after that it should take less than a second to process each frame - in fact you can see in your second image that the 'Solve Time' for the last frame was 108ms (0.108s). Waiting for a very long time in the hope that a frame will solve is probably not going to help - better to try adjusting the parameters like exposure, gain, digital gain, etc.

However, in your case I think the issue might be simpler - looking again at your second image I can see that the declination found was about 85.5 - that puts it right on the edge of the area that SharpCap has a star index for and it's entirely possible that as you rotated the scope you moved even further from the pole meaning that SharpCap couldn't solve the second frame at all because it was seeing stars that it didn't have in its index.

For now, the best solution is to get your rough polar alignment a little closer. I am considering an increase to the area covered by the polar alignment star index in a future version, but it will require some other changes otherwise it might become too slow.

If you continue to have issues, please remember to grab a capture of the star field causing problems by pressing the 'SnapShot' button in SharpCap (as well as screen shots). If you are using SharpCap 2.9, you may need to turn polar alignment off before taking the snapshot to avoid getting a corrupted image.

cheers,

Robin

mhectorgato
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Re: Not solving (have 15 stars used)

Post by mhectorgato » Sun May 21, 2017 9:19 am

Thanks for the response. I am really new to all of this - just got my scope less than a month ago. So I am still learning all that I need to learn.

In my naivety I was hoping that if I point it in the vicinity of Polaris, SharpCap would know where it was. I need to work on my rough PA skills.

My issue is that the guide scope has the SSAG mounted to it, so I tried to look down the barrel to get it aligned.

I'll give it a try again, as I am sure the fault is mine :)

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Re: Not solving (have 15 stars used)

Post by admin » Sun May 21, 2017 3:42 pm

My usual approach for a rough polar align would be:

* Set the altitude on the mount equal to your latitude
* Put the mount in place, use a compass to align roughly with North (check to see if magnetic north deviates much from true north where you live)
* Sight along the top of the telescope tube(or anything else aligned with the tube) look for Polaris - move left/right if Polaris seems misaligned in the horizontal
* Once aligned left/right, check the mount is close to level (may have a built in bubble level)

The combination of the first and last steps should get your altitude close enough to start fine polar aligning. Steps 2 & 3 get the direction set up for you.

cheers,

Robin

mhectorgato
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Re: Not solving (have 15 stars used)

Post by mhectorgato » Sun May 21, 2017 4:51 pm

That's been my routine as well, at least that's what I attempt to do.

I also have a StarSense. Perhaps I should have it do an auto-align first, and then slew to Polaris. Hopefully then it would be closer to Polaris than I am getting to.

I have a AVX mount, and use the ST4 on the SSAG. PHD2 tries to track, but I think the PA is too far off, and it looses the star.

cuivenion
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Re: Not solving (have 15 stars used)

Post by cuivenion » Sun May 21, 2017 5:32 pm

If you've got a polar scope use that. It doesn't have to be very accurate I just center polaris in the crosshairs in the circle. Sharpcap never has a problem solving after that.

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