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Sharp Cap PA, not so Sharp?

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#1 Ballyhoo

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Posted 24 April 2019 - 12:44 PM

I would like to share my experience last night. I should have taken screenshots but I will describe.  I used my QHY-5L for the first time tried the SharpCap PA, and the iteration would not proceed to step two.  There were dozens of stars in the field but they were not being solved! I waited minutes, adjusted the gain and exposure time and reset the process a few times.  I would get these red and yellow boxes in the field but nothing more than that. Very odd to me and makes me question the efficacy of this program. How could I have all of these stars in the field around the pole star and SharpCap was incapable of solving. I went down as low as a few second expsosure, up to about 30 seconds. What else could I a done?

 

Edit:

This gets my official "This is an outrage," seal of disapproval.



#2 entilza

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Posted 24 April 2019 - 01:20 PM

Maybe you weren't close enough to pole to begin with.

Also, What scope were you using, guidescope or oag. You can also use your primary camera depending on your field of view instead of the smaller guide cams!

#3 Ballyhoo

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Posted 24 April 2019 - 01:34 PM

Maybe you weren't close enough to pole to begin with.

Also, What scope were you using, guidescope or oag. You can also use your primary camera depending on your field of view instead of the smaller guide cams!

Hello. actually was set on zero position which meant I was on Polaris -- which was visible when I put my 17mm ethos polaris was within that FOV.  I was using the QHY5 with my St 50mm.  I saw plenty of stars in the FOV but why were they not beiong solved is the mystery I would like to disover. It was the first time I ever tried with this QHY. 

 

Certainly there must be someone else out there who experienced this, plenty of stars in the FOV but no solution?

 

What exposure times should be used? I fluctuated bw .5 and 35 seconds.  And again I saw all the red and yellow boxes popping up.  

 

If I do use my larger ASI294, perhaps I should barlow it so as to reduce the FOV...

 

 

Thank you!



#4 entilza

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Posted 24 April 2019 - 01:49 PM

Oh no more than 1 to 2 seconds are necessary.. You can increase the gain.

No need to barlow the 294 it will be fine as is. What is the main scope?

Edited by entilza, 24 April 2019 - 01:49 PM.


#5 Ballyhoo

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Posted 24 April 2019 - 01:55 PM

Oh no more than 1 to 2 seconds are necessary.. You can increase the gain.

No need to barlow the 294 it will be fine as is. What is the main scope?

This is the main scope.   https://optcorp.com/...CQaAuw7EALw_wcB

 

 

If anyone else has some ideas please me know bc this should be able to solve w a QHY5 in an ST50 I would think. That is a very basic configuration.



#6 entilza

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Posted 24 April 2019 - 02:01 PM

It takes practice to learn new things. Knowing now you only need 1 to 2 second exposures should help you.

There should be some adjustments at the bottom with the star detection to see if that helps.

Take a screen shot next time you are having some trouble. Will be easier to help too.

Will work with both scopes just fine.

#7 davidparks

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Posted 24 April 2019 - 02:03 PM

Be aware of a few requirements that are specified in the Sharpcap Documentation, specifically:

   •A field of view in the camera of between 1 degree and about 2.5 degrees
   •Able to see about 15 stars in the field of view
   •To already be aligned within 5 degrees of the pole

 

And when your looking at the screen seeing lots of stars, make sure you are looking at the un-stretched raw image  (reset your display stretch)

 

Use a 2x or 4x binning during plate solve operations (like polar align)

 

As far as the "efficacy of this program", by this forums indication, it works fantastically for many people under many different conditions.


Edited by davidparks, 24 April 2019 - 02:04 PM.

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#8 entilza

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Posted 24 April 2019 - 02:08 PM

FYI its down to .5 field of view. I've tested and it works well. Very impressive :) I don't think the document is updated but it was posted somewhere.
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#9 Ballyhoo

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Posted 24 April 2019 - 02:25 PM

Be aware of a few requirements that are specified in the Sharpcap Documentation, specifically:

   •A field of view in the camera of between 1 degree and about 2.5 degrees
   •Able to see about 15 stars in the field of view
   •To already be aligned within 5 degrees of the pole

 

And when your looking at the screen seeing lots of stars, make sure you are looking at the un-stretched raw image  (reset your display stretch)

 

Use a 2x or 4x binning during plate solve operations (like polar align)

 

As far as the "efficacy of this program", by this forums indication, it works fantastically for many people under many different conditions.

Yeah like most things I get wrong, I miss some basic element.  Like last night I was having a tough time for a few minutes getting my bahtinov mask to give me a good image for main camera in Nebulosity. It was just that I needed to adjust the histogram. But I am not sure in this case what I could have done diff in SharpCap. FOV of guide camera is 1.37" by 1.03." There were many stars on the screen that I saw, above #15 for sure. and I was certainly very close to Polaris.  Maybe those settings at the bottom of the screen - but I was not going to adjust them without knowing I could improve on the defaults.

 

I went ahead and had a decent guiding session without the Sharp Cap PA.

 

I have been fortunate to be able to go out last couple of nights. Last night I shot M101, night before M51.

 

Just like my experience with M101 visually, it is quite faint compared to M51 and I am surprised Messier even cataloged it.  Each of these represent about 2 hours integration.  

 

So for me SharpCap PA is something I Would like to nail down to improve my star shape, but does not seem absolutely necessary. 

Attached Thumbnails

  • M101 & 51.gif

Edited by Ballyhoo, 24 April 2019 - 02:26 PM.

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#10 Stelios

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Posted 24 April 2019 - 02:40 PM

Hello. actually was set on zero position which meant I was on Polaris -- which was visible when I put my 17mm ethos polaris was within that FOV.  I was using the QHY5 with my St 50mm.  I saw plenty of stars in the FOV but why were they not beiong solved is the mystery I would like to disover. It was the first time I ever tried with this QHY. 

 

Certainly there must be someone else out there who experienced this, plenty of stars in the FOV but no solution?

 

What exposure times should be used? I fluctuated bw .5 and 35 seconds.  And again I saw all the red and yellow boxes popping up.  

 

If I do use my larger ASI294, perhaps I should barlow it so as to reduce the FOV...

 

 

Thank you!

There's nothing wrong with the QHY camera and a 50mm guidescope for using Sharpcap.

 

You should use 2 seconds exposures, wait till it's fairly dark, and be fairly close to Polaris. Also make sure that the guidescope is in focus!!!

 

It works for everyone, it will work for you, too :)


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#11 Ballyhoo

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Posted 24 April 2019 - 02:53 PM

There's nothing wrong with the QHY camera and a 50mm guidescope for using Sharpcap.

 

You should use 2 seconds exposures, wait till it's fairly dark, and be fairly close to Polaris. Also make sure that the guidescope is in focus!!!

 

It works for everyone, it will work for you, too smile.gif

Ok Steleios,

 

I prob was not super focused like I would be w my main imaging camera, which now I go to great lenghts to get focus. For Phd the focus does not need to be right on, in fact a little larger of stars maybe helps Phd. So you think if I was not 100% on focus I could have had this lack of solving?



#12 DSO_Viewer

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Posted 24 April 2019 - 03:16 PM

I would like to share my experience last night. I should have taken screenshots but I will describe.  I used my QHY-5L for the first time tried the SharpCap PA, and the iteration would not proceed to step two.  There were dozens of stars in the field but they were not being solved! I waited minutes, adjusted the gain and exposure time and reset the process a few times.  I would get these red and yellow boxes in the field but nothing more than that. Very odd to me and makes me question the efficacy of this program. How could I have all of these stars in the field around the pole star and SharpCap was incapable of solving. I went down as low as a few second expsosure, up to about 30 seconds. What else could I a done?

 

Edit:

This gets my official "This is an outrage," seal of disapproval.

There is absolutely nothing wrong with Sharpcaps PA and it works perfect for me. 9 x out of 10 it is user error and perhaps post your question directly to Robin of SC on his forum for some help.

 

Steve



#13 kenkolen

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Posted 24 April 2019 - 03:17 PM

Did I miss something? What were you trying to do? Polar Align?

#14 Paulyman

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Posted 24 April 2019 - 03:39 PM

Because I setup every night I have to go through the process of aligning the tripod with true south using a compass. Nearly every time I obviously get it close enough and Sharpcap works it’s magic. But I have had the same issue as you a few times, where it sees lots of stars evidenced by those yellow and red boxes but won’t solve. On reexamination using sky safari on my phone I found each and every time I was not pointing close enough to the SCP. That’s right, no Polaris here I can’t see any visual reference in the suburbs here. It’s just a part of setting up every night, most times it is flawless and very occasionally it needs more refining.

Edited by Paulyman, 24 April 2019 - 03:41 PM.


#15 kyle528

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Posted 24 April 2019 - 03:53 PM

Zero position does not mean polar aligned. Just because you can see Polaris in the eyepiece at zero position does not mean you are polar aligned. The experience you describe sounds like your initial PA was out by more than the required 5 degrees. Maybe do a rough PA using your mount's polar scope first? 



#16 Ballyhoo

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Posted 24 April 2019 - 04:12 PM

Zero position does not mean polar aligned. Just because you can see Polaris in the eyepiece at zero position does not mean you are polar aligned. The experience you describe sounds like your initial PA was out by more than the required 5 degrees. Maybe do a rough PA using your mount's polar scope first? 

yea I know zero is not celestial north but again, everyone here, I was very close to celestial north. If I Was not, how would I have been able to proceed onto guiding n and get the images I did? I did a polar align using the android app and my IEQ45's polar scope. The only explanation would be that my polar scope is out of alignment, but I have checked that too and it appears to be in alignemtn. 

 

 

edit, here  is the center of my field yesterday . I do not use a flattner so my edges will show elongation but the ctr here, tell me those stars are elongated. This was a 3 min sub so if I was off the celestial north how would my stars look like that? 

 

 

EDIT EDIT, I agree there is some elongation and that is why I would like to use the SharpCap PA, but not enough that I would be off more than a degree from Polaris. Or maybe I am wrong and my polar scope is out of alignment but I tend not to think so.

Attached Thumbnails

  • 101 crop.jpg

Edited by Ballyhoo, 24 April 2019 - 04:22 PM.


#17 StephenW

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Posted 24 April 2019 - 04:19 PM

@Ballyhoo - as you know, you can used PHD2 and other tools to measure how accurate your PA actually is.   Had you set-up you mount again since the previous night when you were just 18' out of PA alignment?



#18 Ballyhoo

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Posted 24 April 2019 - 04:24 PM

@Ballyhoo - as you know, you can used PHD2 and other tools to measure how accurate your PA actually is.   Had you set-up you mount again since the previous night when you were just 18' out of PA alignment?

Are you saying that given my current images, with the star elongation that I have (above) I could be so far off that SharpCap will not solve?  Because I would think that given that I followed the polar scope alignment very close with the Android app and my current images, I would not be too far off.

 

edit , and if I was that far off would you not see field rotation (#9) ?

 

 

EDIT EDIT, Okay maybe here is something, maybe........   I did not start my SharpCap PA alignmet as step 1.

 

What I did first was go to a star nearby where I wanted to image and I got my focus. Then, I went to my zero position, which, was where I started my native PA. So, maybe, the goto the zero position was not at celestial north. 

I am not sure how that would be bc last night's goto was right on the dime's nose. 


Edited by Ballyhoo, 24 April 2019 - 04:28 PM.


#19 Stelios

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Posted 24 April 2019 - 04:29 PM

@Ballyhoo: You don't try for perfect PA just to avoid field rotation (and your images do not appear to exhibit that, though it's not easy to see at this scale). But there are other things PA helps with. One is fewer adjustments in DEC. Another (which may or may not apply to your mount) is ease of alignment (stars more likely to be within FOV after a slew). 

 

Also, the idea that PhD2 does better with distorted stars is an urban legend and should be fought. From the PHD2 manual, under "Exposure Time and Star Selection"

 

"If you're using a small guide scope, like a finder-scope, the focus may react strongly to small adjustments.  It's important to spend the time to get a good focus because a poorly focused guide star can lead to many other problems."

 

When in doubt, get the truth from the horse's mouth.


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#20 Ballyhoo

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Posted 24 April 2019 - 04:33 PM

@Ballyhoo: You don't try for perfect PA just to avoid field rotation (and your images do not appear to exhibit that, though it's not easy to see at this scale). But there are other things PA helps with. One is fewer adjustments in DEC. Another (which may or may not apply to your mount) is ease of alignment (stars more likely to be within FOV after a slew). 

 

Also, the idea that PhD2 does better with distorted stars is an urban legend and should be fought. From the PHD2 manual, under "Exposure Time and Star Selection"

 

"If you're using a small guide scope, like a finder-scope, the focus may react strongly to small adjustments.  It's important to spend the time to get a good focus because a poorly focused guide star can lead to many other problems."

 

When in doubt, get the truth from the horse's mouth.

So then maybe I just did not have good enough focus??  And I am not questioning why to do PA, I am just saying if I had bad PA, if I was not close to celestial north, I would have field rotation, and star elongation. 



#21 kyle528

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Posted 24 April 2019 - 04:33 PM

yea I know zero is not celestial north but again, everyone here, I was very close to celestial north. If I Was not, how would I have been able to proceed onto guiding n and get the images I did? I did a polar align using the android app and my IEQ45's polar scope. The only explanation would be that my polar scope is out of alignment, but I have checked that too and it appears to be in alignemtn. 

 

 

edit, here  is the center of my field yesterday . I do not use a flattner so my edges will show elongation but the ctr here, tell me those stars are elongated. This was a 3 min sub so if I was off the celestial north how would my stars look like that? 

 

 

EDIT EDIT, I agree there is some elongation and that is why I would like to use the SharpCap PA, but not enough that I would be off more than a degree from Polaris. Or maybe I am wrong and my polar scope is out of alignment but I tend not to think so.

I don't think anyone here is saying that it was in fact your PA that was the issue. Just going through the steps of diagnosing the problem. Sharpcap PA issues in most cases stem from initial PA issues. On the solving screen in sharpcap PA, it will show a number for "stars found" and "stars used". I believe the minimum to continue is 10 stars used. Just because there were many stars visible in the image, it may not have used enough to advance to the next step. This is just my thinking though, as I have never had this problem. Out of focus and low SNR come to mind, but you say focus was good so you may be able to rule that out. 



#22 Ballyhoo

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Posted 24 April 2019 - 04:51 PM

I don't think anyone here is saying that it was in fact your PA that was the issue. Just going through the steps of diagnosing the problem. Sharpcap PA issues in most cases stem from initial PA issues. On the solving screen in sharpcap PA, it will show a number for "stars found" and "stars used". I believe the minimum to continue is 10 stars used. Just because there were many stars visible in the image, it may not have used enough to advance to the next step. This is just my thinking though, as I have never had this problem. Out of focus and low SNR come to mind, but you say focus was good so you may be able to rule that out. 

thanks, no what I meant was focus on the main imaging camera was good.   I do not think that the focus on the guide cam that I used for the Sharp Cap Pa was that good. so now I am thinking, I would like a little 50mm bahtinov mask.

 

1) guide-cam not in good focus.

2) When I slewed back to zero position, which was where I did the initial native PA, maybe the goto slew was not close enough.

 

I think #1 seems more likely bc I am confident my focus on the guide cam was not very good.

 

But that just raises the question: how well in focus is required for a SharpCap PA? 



#23 StephenW

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Posted 24 April 2019 - 04:55 PM

Are you saying that given my current images, with the star elongation that I have (above) I could be so far off that SharpCap will not solve?  Because I would think that given that I followed the polar scope alignment very close with the Android app and my current images, I would not be too far off.

 

My point was that when in doubt, you can use tools like PHD2 to check.  I (and nobody else) has any idea whether you were withing Sharpcap's 5 degree initial pointing requirement - but you can certainly check to make sure that you were, and so eliminate that as a potential problem.

 

And again, had you torn down and set up your mount again or were you still using the 18' aligned set-up from the previous night?  Obviously if you had not moved the mount and were still within 18' then this was not the cause of Sharpcap failing.



#24 Ballyhoo

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Posted 24 April 2019 - 05:09 PM

My point was that when in doubt, you can use tools like PHD2 to check.  I (and nobody else) has any idea whether you were withing Sharpcap's 5 degree initial pointing requirement - but you can certainly check to make sure that you were, and so eliminate that as a potential problem.

 

And again, had you torn down and set up your mount again or were you still using the 18' aligned set-up from the previous night?  Obviously if you had not moved the mount and were still within 18' then this was not the cause of Sharpcap failing.

I have had these long drawn out threads before from a prev night only to go out the following night without issue. So I bet it will work next try



#25 Ballyhoo

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Posted 24 April 2019 - 07:10 PM

One more question, if someone gets to step 2. but the scope is point to  a low-lying hill or obstruction, do you just slew somewhere else?




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