Newbie - Problem with PA

Using SharpCap's Polar Alignment feature
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woldsweather
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Newbie - Problem with PA

Post by woldsweather »

This winter has been my first learning how to PA star align and take photos. I have an Altair EDF 72 a Canon 6D Mk2 and an Altair GPCAM2 130 Mono Guide Imaging EAA Camera.

I have been using Polemaster and/or Sharpcap to compare. I find Sharpcap much easier to use but Polemaster is very sensitive as soon has several stars once Polaris is visible.

Is it normal that it has to be totally dark before Sharpcap works? I find even after it has solved the first plate and I have turned the scope it may then fail to solve for 20-30 plates and I have to start again. I don't know how normal this is because I don't know anyone who uses it.

Is there a way to make it more sensitive? I have always had gain on full never lower and exposure mostly 4 secs though had to use 8secs some times.

It would be a wonderful tool if I could get it plate solving more frequently for me.
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oopfan
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Re: Newbie - Problem with PA

Post by oopfan »

"Is it normal that it has to be totally dark before Sharpcap works?"
-- I wait for the Sun's elevation to drop below -12 degrees.
woldsweather
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Re: Newbie - Problem with PA

Post by woldsweather »

I don'y know how I'd know when it was MS 12 deg. Last night it was still having trouble platesolving 1.5 hours after sunset.
chongo228
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Re: Newbie - Problem with PA

Post by chongo228 »

Is your camera cooled? Full gain is probably too much. If your camera isn't cooled full gain would create so much noise the image would have a ton of noise. Even with a cooled camera full gain would be too much. Try 25% to 50% gain and 3 -5 second exposures. Adjust the noise and black level until you see the star count move.

And as always focus....eyeball focus isn't always good enough. You really need a mask to be 100% sure it's in focus.
woldsweather
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Re: Newbie - Problem with PA

Post by woldsweather »

I have focussed the GPCAM a couple of times with a Bahtinov mask. The camera is not cooled. Noise and black level are new to me where are they? I'll have another look at focus with the mask tonight. I find the helical focuser diabloical. You turn the focuser and the star you are focusing goes off the screen.
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oopfan
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Re: Newbie - Problem with PA

Post by oopfan »

"I don'y know how I'd know when it was MS 12 deg."
-- Download for free Computer Aided Astronomy (C2A) to your laptop, search for "Moon" and wait for altitude to be less than -12
http://www.astrosurf.com/c2a/english/
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oopfan
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Re: Newbie - Problem with PA

Post by oopfan »

"The camera is not cooled"
-- I have an Altair GPCAM2 290M, not cooled, works great for polar alignment, guiding, and imaging

More importantly, your field-of-view is only 0.64 deg x 0.48 deg (see attachment RED). That is your FOV with the Altair 72 EDF and Altair 130 camera. From experience I can tell you that this combination won't work. Perhaps if you had a 0.5x focal reducer, it would help. Better if you should purchase a dedicated guide scope. Mine is 160mm focal length (see attachment YELLOW). You can pick one up for less than $100.
woldsweather - polar alignment.jpg
woldsweather - polar alignment.jpg (26.88 KiB) Viewed 177 times
Brian
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admin
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Re: Newbie - Problem with PA

Post by admin »

Hi,

if you are using the GPCAM on the EDF72 then the field of view would definitely be a bit small. If you are already on some sort of guide scope (~200mm focal length) then you should be in the sweet spot already.

Sometimes its easy to make so many adjustments to the star detection settings that it might be worth putting them all back to default, as the defaults are usually pretty good.

If you haven't already, check out the troubleshooting guide for PA - https://www.sharpcap.co.uk/sharpcap/fea ... leshooting

If you are still stuck with poor plate solving after that, save a frame or two (press the snapshot button) and share the images here.

thanks,

Robin
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