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SharpCap Polar Alignment Experiences

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#1 ChrisMoses

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Posted 03 August 2016 - 03:26 AM

Hi,

I would like to know what everyone's experience has been using the new polar alignment feature in SharpCap

 

(For those of you that might have missed it, the latest 2.9xx version of SharpCap has a polar alignment feature that many are comparing to the PoleMaster - but it is free)

 

Specifically, for anyone who has used it, please let us know things like:

 

1. Did it work for you. If not, how did it fail

2. Did it produce good results - I.e. - good polar alignment

3. How long did it take

4. What sort of camera and scope were you using.

5. Was the software easy to understand?

6. WIll you be using it in the future? Why or why not.

7. If you also have experience with the PoleMaster, how do they compare?

 

If you haven't used it, feel free to ask questions about it.



#2 ChrisMoses

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Posted 03 August 2016 - 03:44 AM

I tried the SharpCap Polar Alignment feature for the first time tonight. 

I was using a QHY5II-L on an AT-60 guidescope.  Can't remember the FOV offhand.

 

I hadn't read the instructions, just selected it from the TOOLS menu.

It instructed me to slew to near Polaris. Once there it spend about 30s finding and identifying stars. Then it told me to slew about 90 degrees in RA, which I did.

 

It sat and thought for a few seconds as it identified more stars. Then it had me move to a third screen.  

 

This is a very cool screen!  It shows the NCP, polaris, and your current errors in ALT and AZ.  All you have to do is adjust ALT and AZ and you get real-time feedback and can see a highlighted star move to where it should be.

 

I was using 2s images, so it was more like: make an adjustment, wait 5-6 seconds for a new frame and the software to catch up - but that is real, real close to real-time in my book.

 

So far I had spend about 15 minutes at it.  Mainly reading the directions at each step.

 

I was running short on time and high on clouds, so I stopped when I got the total error to under 3am. I tried to go over to Phd2 to verify the accuracy using drift guiding, but Phd2 started giving me problems. Probably due to the clouds.  Anyway I had been shooting 45 second guided subs all night long so I thought I would try a few unguidedd ones with my now (hopefully) improved PA.  On initial inspection, they look great - probably at least as good as my guided ones.  (I'll inspect them more tomorrow)

 

So, my initial conclusion, based on a brief experience, is that this has the potential to be really, really cool.  A free, real-time polar alignment tool.

As an added benefit, it should work as soon as the camera can see the stars.  With my QHY this is often significantly before I can.

 

On the downside, I think it works best with a guidescope and camera with a fairly narrow field of view.  I think they mention that in the docs.

 

I hope everybody will give it a shot - and report back their experiences and knowledge gained.


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#3 A. Viegas

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Posted 03 August 2016 - 05:57 AM

Hi Chris. Thanks for that review. I tried it about a month ago but stopped on the first page because I can't see Polaris from my location as its obstructed. So I did not go any further. I will give it another go this week to see if there is a workaround for an obstructed NCP.

Al

#4 FiremanDan

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Posted 03 August 2016 - 06:44 AM

Good to know. I was planning on ordering a pole master today when I got off shift.

I might have to wait a bit. Right now I have an SSAG and a 50mm guide scope, would that be narrow enough? Do you enter in your FL/image scale?



#5 larryjh

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Posted 03 August 2016 - 07:09 AM

I am surprised to see folks saying the FOV needs to be narrow.  Even with a 0.5x focal reducer I can't get a 1 deg FOV, so I was thinking I couldn't use this utility.  The Sharpcap website says 1 - 2.5 deg.  Has anyone tried it with an FOV of less than 1 deg?



#6 nxda

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Posted 03 August 2016 - 08:16 AM

Was this capturing images through the guide camera or your main imaging camera?



#7 ChrisMoses

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Posted 03 August 2016 - 10:42 AM

Good to know. I was planning on ordering a pole master today when I got off shift.

I might have to wait a bit. Right now I have an SSAG and a 50mm guide scope, would that be narrow enough? Do you enter in your FL/image scale?

I was using a 60mm guidescope with a small chip. So it will probably work.

I'll calculate my fov and post it.


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#8 ChrisMoses

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Posted 03 August 2016 - 10:47 AM

I was using an AT-60: FL 240mm, F4

Qhy5II-l: 1280x960 3.75 um

 

FOV = 1.15 x .86

 

Pretty tight for a guidescope.



#9 ChrisMoses

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Posted 03 August 2016 - 10:48 AM

Was this capturing images through the guide camera or your main imaging camera?

IN this case, through the guide camera.  Although there is no reason you couldn't use your main camera.  As long as SharpCap can control it, it should work just fine.



#10 Iver

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Posted 03 August 2016 - 10:19 PM

I used it a few times and found it to be very quick and accurate. I have a QHY-5 and a 50 mm guide scope. Once I had used it a few times I was able to get polar aligned very quickly! I haven't been able to get out for a few months due to fog and now a lot of smoke from a nearby wild fire. After the last time I used it, I posted this on another forum on May 21.

 

I gave the Polar align feature in SharpCap a real test tonight, I spent a little extra time getting the alignment as close as possible. This still took less then 5 min. I centered M13 and started guiding with Dec. corrections disabled.  I let this go for 25 min. and during that time the average error in Dec. remained at .06 pixel. No detectable drift in 25 min. Quite a nice PA tool.


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#11 FiremanDan

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Posted 04 August 2016 - 10:00 AM

I'd really like to see a side by side shoot ou between the pole master and this. To see how close they are for accurate PA.

#12 ChrisMoses

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Posted 04 August 2016 - 12:06 PM

I'd really like to see a side by side shoot ou between the pole master and this. To see how close they are for accurate PA.

Yeah me too.  

I don't have a polemaster but the next time I go out I'm going to give sharpcap a complete test.  First up, I want to verify its reported accuracy with a drift test in Phd2. If that is good, then I'm not sure I personally will have a lot of reason to consider a polemaster.  SharpCap seems fast, cheaper, and doesn't require toting around more hardware.

 

Tonight's sky is looking good.  Cross your fingers...


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#13 Becomart

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Posted 04 August 2016 - 03:33 PM

I've got absolutely no evidence whatsoever to base this opinion on but I'd be surprised if the sharp cap was as quick and accurate as the polemaster being a dedicated piece of hardware to do a very specific job. 



#14 Stelios

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Posted 04 August 2016 - 04:01 PM

I have a feeling that SharpCap would be much more of a hassle even if more accurate. The huge advantage of Polemaster is saving time. Once you got the axis position recorded, it takes about 1-2 minutes *tops* for the whole thing. And then you cover it and leave it on your scope. I've made a little niche in my mount case for it. 

 

I bet there would be many more steps involving using Sharpcap with one's guide cam as you'd have to remove and replace it from/to the guidescope, otherwise you'd be aligning the *guidescope*. As time is always short for me, Polemaster is a godsend.

 

As for Polemaster accuracy... yesterday I shot 10 2-minute videos of Saturn at about 380 pixels frame with Firecapture, and the planet just stayed put the whole time. (I think my CG-5 likes the little guy, it's not usually this accommodating).



#15 ChrisMoses

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Posted 04 August 2016 - 04:01 PM

I've got absolutely no evidence whatsoever to base this opinion on but I'd be surprised if the sharp cap was as quick and accurate as the polemaster being a dedicated piece of hardware to do a very specific job. 

I'm not sure if SharpCap knows the exact sensor dimensions and pixel sizes.  If not, that could help make POleMaster more accurate.



#16 ChrisMoses

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Posted 04 August 2016 - 04:17 PM

I have a feeling that SharpCap would be much more of a hassle even if more accurate. The huge advantage of Polemaster is saving time. Once you got the axis position recorded, it takes about 1-2 minutes *tops* for the whole thing. And then you cover it and leave it on your scope. I've made a little niche in my mount case for it. 

 

I bet there would be many more steps involving using Sharpcap with one's guide cam as you'd have to remove and replace it from/to the guidescope, otherwise you'd be aligning the *guidescope*. As time is always short for me, Polemaster is a godsend.

 

As for Polemaster accuracy... yesterday I shot 10 2-minute videos of Saturn at about 380 pixels frame with Firecapture, and the planet just stayed put the whole time. (I think my CG-5 likes the little guy, it's not usually this accommodating).

I'm not sure I understand what you are saying, but there is nothing to remove and replace.  SharpCap just uses your normal guidescope and camera.  Or, you could use your imaging camera if you wanted to, as long as SharpCap can control it and it has the right FOV.



#17 nxda

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Posted 04 August 2016 - 07:26 PM

I bet there would be many more steps involving using Sharpcap with one's guide cam as you'd have to remove and replace it from/to the guidescope, otherwise you'd be aligning the *guidescope*. As time is always short for me, Polemaster is a godsend.

 

 

Stellios,

 

Your imaging scope is not where you guide scope is... your logic implies your imaging scope should be where your PoleMaster is for correct tracking. A few inches of angular difference to infinity is really a non factor.

 

And remember, SharpCap is free! 

 

Full disclosure... I have had to be really patient today not buying a PM. Skies will be clear enough tonight to try SharpCap. If it works well... no PM. If I find it just ok or a hassle... PM on order tomorrow.

 

Will 


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#18 ChrisMoses

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Posted 04 August 2016 - 08:16 PM

 

 

Full disclosure... I have had to be really patient today not buying a PM. Skies will be clear enough tonight to try SharpCap. If it works well... no PM. If I find it just ok or a hassle... PM on order tomorrow.

 

Will 

 

 

I think I speak on behalf of all of us when I say you should buy one - as a public service to the CN community.  Just so you can do a side by side comparison. If everyone who reads and benefits from this thread donates a beer towards the cause, you will end up...drunk.


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#19 Iver

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Posted 04 August 2016 - 09:57 PM

 

I've got absolutely no evidence whatsoever to base this opinion on but I'd be surprised if the sharp cap was as quick and accurate as the polemaster being a dedicated piece of hardware to do a very specific job. 

I'm not sure if SharpCap knows the exact sensor dimensions and pixel sizes.  If not, that could help make POleMaster more accurate.

 

Since SharpCap is plate solving the image I think it must know the image scale.

 

FWIW, I have read that the PA scope on my mount is considered to be very good, so I my be able to align a bit faster because I get a better initial alignment.


Edited by Iver, 04 August 2016 - 10:27 PM.


#20 ChrisMoses

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Posted 04 August 2016 - 10:07 PM

 

 

Since SharpCap is plate solving the image I think it must know the image scale.

 

Actually you can plate solve without knowing the image scale.  That is called blind solving, when you don't know the approx. scale or location.  It is much more computationally intensive.  However, SharpCap states that the image must be in a certain range, to make it much easier.



#21 Iver

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Posted 04 August 2016 - 10:33 PM

Yes, but once the image is solved the scale will be known.



#22 Ent

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Posted 05 August 2016 - 07:51 PM

I tried polar aligning with the SharpCap tool last night and it worked very well with my QHY5L-II and 50mm guide scope. I found it to be pretty straight forward and intuitive. There's only three steps really, let it plate solve when the mount is parked, rotate in RA ~90 degrees then let it solve again then move the indicated star into the circle with the physical adjustments. There's an arrow from the star to the circle to make adjustments easily visible and when you get really close it changes to parallel lines so you can see how far you'll need to adjust.

 

Yes, it blind solves and figures out all the numbers it needs. You don't need to put in any information at all. I used 2 second exposures and solving took about 300ms on my laptop (2.5 year old i7).

 

My biggest issue was having my mount on a wooden deck meant the alignment would change a bit when I went back to my laptop. Nothing to do with SharpCap, but I just had to aim past the circle a bit so it would bounce to the right place when I left. Still ended up with an indicated under 1 arcmin off the pole. Then I fired up PHD and let the guiding assistant run for 5 minutes or so and got a measured 1.5 arcmin off the pole. Good enough to get steady <1" RMS guiding with my un-tuned Atlas. Can't complain for an under 10 minute first try.

 

I have to setup every time I go out and was considering the Polemaster but the SharpCap polar align tool worked well enough that I'm not going to bother. Which is good because up here in Canada land the Polemaster would be close to $500 after taxes and shipping.



#23 ChrisMoses

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Posted 05 August 2016 - 08:23 PM

I spent some more time playing with the PA function.  I few impressions:

1. It is really easy, Ent's (poster above) description is exactly what I was going to say - just 3 steps

2. Getting feedback in realtime when adjusting the alt/az is incredible.  No wondering if you are moving it in the the correct direction. And no waiting minutes to see how much affect your movement had.

3. I did find that sometimes it would take about 10s to register my changes in alt/az

 

In the end, I stopped before I was dead on the target location just because I was tired of fighting with my alt, which was desperately in need of some lube.

 

According to Phd2, my error was about 3-5 arc  minutes.  Very good.

 

If it is repeatable, and reliable (which it appears to be) , I'll happily keep using it.



#24 nxda

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Posted 06 August 2016 - 12:25 AM

Well I tried it last night too. Unless I am missing something, I don't think it works with my gear. Neither my Lodestar or Nikon are listed as supported cameras and I could not get it to do anything.... bummer!

 

Will



#25 Iver

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Posted 06 August 2016 - 12:41 AM

Will, you should be able to use the Lodestar if you use the ASCOM driver.




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