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Please help with Sharpcap

Celestron EAA dso equipment
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#1 nrcapes

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Posted 22 July 2020 - 02:40 PM

I have a Celestron Evolution 9.25 telescope. I’ve had some success with DSO using the Revolution 2 Imager on things like M57 and M13.  I want to move to SharpCap but have had no success with objects like these. I suspect part of the problem is that the ZWO ASI290MM Mini camera has a much smaller FOV than the analog camera of the R2. I am sure that the object is centered in a 4mm illuminated reticle EP and that nearby stars are in focus. I then swap in the ZWO mini for the EP, fire up SharpCap, and take a 10 stack shot. NADA.  Then I try Livestack and it ignores all frames because it can’t find enough stars to align.. BTW, I am using a Celestron 0.63 focal reducer in front of the star diagonal. I live in St. Paul, MN which has pretty darn high light pollution, so maybe this is why SharpCap can’t find enough stars. Is there something else I should be doing other than going to a dark sky site? Thanks!



#2 descott12

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Posted 22 July 2020 - 02:43 PM

The focus for the EP and the camera is dramatically different. Best thing to do is practice in the daytime on a distant object or on the moon and see for your self. Then it will be easy at night.

if out of focus, even the brightest stars will literally disappear.


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#3 nrcapes

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Posted 22 July 2020 - 02:53 PM

I forgot to add that I did get stars in focus through the camera but they move very fast across the computer screen. Of course, this is an alt-az mount. Then when ai go to the DSO, there is still NADA.

The focus for the EP and the camera is dramatically different. Best thing to do is practice in the daytime on a distant object or on the moon and see for your self. Then it will be easy at night.

if out of focus, even the brightest stars will literally disappear.



#4 descott12

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Posted 22 July 2020 - 03:27 PM

Well if they are moving then your tracking isn't on... or am I missing something??


Edited by descott12, 22 July 2020 - 03:30 PM.


#5 GazingOli

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Posted 22 July 2020 - 03:28 PM

What exposure time did you use? What was the Gain setting?

 

CS.Oli


Edited by GazingOli, 22 July 2020 - 03:29 PM.


#6 Noah4x4

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Posted 22 July 2020 - 03:50 PM

Well if they are moving then your tracking isn't on... or am I missing something??

I found that if using a CPWI/Sharpcap combination I needed to switch (CPWI) tracking on within Sharpcap itself. Options include Sidereal and Lunar. My default tracking was set to off.

 

I am also accustomed to Hyperstar at f/2. That immense wide field can make one lazy. To use my ASI294 or particularly my ASI224 at f/6.3 or f/10 I had to sharpen all my settings, reapply Starsense calibration, add additional alignment points and generally take far more care as it isn't easy to keep an object in FOV if you don't. I had also not used my RACI Finderscope for a couple of years, but found it vital to help resolve all that I had to fix at longer f/numbers.



#7 nrcapes

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Posted 22 July 2020 - 04:49 PM

To all:  thanks for the help. I use SkyPortal for scope control, not CPWI but SkyPortal has tracking set to Sidereal. I will have to see if that’s a problem. Re: exposure and gain, what are good ballpark settings to start with?



#8 RazvanUnderStars

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Posted 22 July 2020 - 07:21 PM

Nrcapes, it'd be helpful if you post a screenshot of your SharpCap window, so we can see all the settings. Another suggestion: orient the scope to Polaris. This way tracking will not matter.

 

For exposures, start with exposures of several seconds and a high gain. This should show stars provided they are in focus. The goal is to get to see Polaris and to see it in focus. Then make sure you perform a careful alignment. 

 

It's not needed initially but super useful to learn to use plate solving from within SharpCap (see https://www.sharpcap...s/plate-solving and note that since that page was written, SharpCap also supports the faster and more modern ASTAP, http://www.hnsky.org/astap.htm, so I'd suggest to start with that). This is useful to bring the target in the center of the view, even when out of frame. You can use it during alignment as well; when the SkyPortal tells you to center a star, instead of slewing the scope, you only click once. But one step at a time.



#9 nrcapes

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Posted 22 July 2020 - 09:29 PM

Nrcapes, it'd be helpful if you post a screenshot of your SharpCap window, so we can see all the settings. Another suggestion: orient the scope to Polaris. This way tracking will not matter.

 

For exposures, start with exposures of several seconds and a high gain. This should show stars provided they are in focus. The goal is to get to see Polaris and to see it in focus. Then make sure you perform a careful alignment. 

 

It's not needed initially but super useful to learn to use plate solving from within SharpCap (see https://www.sharpcap...s/plate-solving and note that since that page was written, SharpCap also supports the faster and more modern ASTAP, http://www.hnsky.org/astap.htm, so I'd suggest to start with that). This is useful to bring the target in the center of the view, even when out of frame. You can use it during alignment as well; when the SkyPortal tells you to center a star, instead of slewing the scope, you only click once. But one step at a time.

Thanks! I will do that the next time there are no clouds.



#10 Noah4x4

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Posted 23 July 2020 - 05:51 AM

To all:  thanks for the help. I use SkyPortal for scope control, not CPWI but SkyPortal has tracking set to Sidereal. I will have to see if that’s a problem. Re: exposure and gain, what are good ballpark settings to start with?

When I moved from Atik Infinity software to SharpCap I struggled with Gain as  Atik uses whole dB units and Sharpcap/ZWO use 0.1 units. Hence 310 with ZWO is 31 with Atik. My saviour was SharpCap's Smart Histogram.  I would be fairly confident that there will already be a sensor profile stored in Sharpcap for the ASI290mm.

 

Simply switch on Smart Histogram (the green graph triangle to the right of Zoom) and once open check <logarithmic>. Then adjust Gain until the left edges of the two (upper) green bars in the Smart Histogram are aligned as far left as they will go. Then adjust Exposure until the left vertical edges of the graphs are just right of the green bar limit. That will put you in the right ball park without even looking at the image on screen. Tweak it from there.

 

The most tricky bit (IMHO) is focus and keeping your target in FOV given that the ASI290mm has such a small sensor. It is best to ensure you have tweaked everything mechanical with an eyepiece and Finderscope to ensure ideal alignment and tracking before you start imaging.  This is especially true if imaging Planets at f/10 (or f/6.3) on an Alt-Az, and keep exposures short and stack them.  Best start by chasing (apparent)  larger targets like the Moon or a larger DSO (like the Orion Nebula) until you get the hang of things as it can be frustrating until you get the knack.



#11 nrcapes

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Posted 24 July 2020 - 01:30 PM

UPDATE:

 

1) Celestron SkyPortal app does not set tracking to sidereal. I had to do that from the hand controller.

2) I was able to capture Polaris with the ASI mini, but I’m not sure how to upload a screenshot of the pc under the forum rules.

3) even with tracking set to Sidereal, any other star move off the SharpCap screen too quickly to do anything with the ASI mini.

4) BUT I was able to stack M13 using the Revolution Imager 2 connected through the USB dongle to the pc. RI2 was at 16 FLD, 42 max gain, DNR 4. SharpCap was set to one second exposure every 2 seconds, and I stacked for 40 minutes according to SharpCap. Image attached. No post processing.

M13-SharpCap-RI2
[


#12 descott12

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Posted 24 July 2020 - 01:36 PM

If stars are moving out of your FOV that means tracking is not enabled for one reason or another. A very annoying thing about the Evolution  mounts (and maybe all Celestron mounts??) is that tracking will always be off until you successfully do a star alignment. Even if you manually turn it on. There is no reason this but it is what it is.

So have you done an alignment first?  When tracking is on, you will definitely hear the motors running.



#13 RazvanUnderStars

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Posted 24 July 2020 - 02:04 PM

As Dave said as well, the mount is not tracking. nrcapes, some questions for you: has the mount ever tracked successfully or is it one that you just got? It could be defective. If you hear the motors, make sure the clutches are tight, otherwise the motors will spin without engaging the mount. It's a common error to make since there's no obvious indication when the clutches are tight (guess how I know smile.gif). 

 

Thirdly, be careful when using both the hand controller and SkyPortal. The alignment model resides in the device with which you aligned, not in the mount itself.

 

As one last thing to try is to use the better CPWI instead of SkyPortal for alignment. 

 

On the M13 image: one-second exposures are way too short. That's a probable cause why SharpCap was not able to align the frames - they were severely undexposed. I understand that without tracking you couldn't take longer exposures - this underlines the need to fix tracking first. You may find that all the other problems go away afterwards.



#14 nrcapes

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Posted 24 July 2020 - 06:13 PM

If stars are moving out of your FOV that means tracking is not enabled for one reason or another. A very annoying thing about the Evolution mounts (and maybe all Celestron mounts??) is that tracking will always be off until you successfully do a star alignment. Even if you manually turn it on. There is no reason this but it is what it is.
So have you done an alignment first? When tracking is on, you will definitely hear the motors running.



#15 nrcapes

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Posted 24 July 2020 - 06:21 PM

Hi and thanks! Yes, I did a manual StarSense alignment and calibration and re-alignment. Through a 4 mm EP at f/10, there is slight movement of a bright star like Deneb. I was attributing this to the mount being alt-az. Should I really expect accuracy like you are saying without a GEM? I confirmed that Tracking is set to Sidereal with the HC. I realize that the ZWO camera has a much narrower FOV than a 4 mm EP. Maybe I need to go to a Hyperstar!



#16 nrcapes

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Posted 24 July 2020 - 06:29 PM

As Dave said as well, the mount is not tracking. nrcapes, some questions for you: has the mount ever tracked successfully or is it one that you just got? It could be defective. If you hear the motors, make sure the clutches are tight, otherwise the motors will spin without engaging the mount. It's a common error to make since there's no obvious indication when the clutches are tight (guess how I know smile.gif). 

 

Thirdly, be careful when using both the hand controller and SkyPortal. The alignment model resides in the device with which you aligned, not in the mount itself.

 

As one last thing to try is to use the better CPWI instead of SkyPortal for alignment. 

 

On the M13 image: one-second exposures are way too short. That's a probable cause why SharpCap was not able to align the frames - they were severely undexposed. I understand that without tracking you couldn't take longer exposures - this underlines the need to fix tracking first. You may find that all the other problems go away afterwards.

Thanks! It is a brand-new Evolution 9.25, so I don’t have a record of tracking. I know very well about using a HC with SkyPortal. As to CPWI, I haven’t had much luck with it. Fir example, when I Disconnect it doesn’t offer the Park Mount option as it is supposed to. I also prefer a planetarium program like SkyPortal that I can walk around with rather than being tied to the pc for goto’s. I will try longer exposure with M13 and see if it makes a difference but frankly I was rather pleased with the results that I got with a first try using the RI2 camera through USB to Sharpcap: I am in a Bortle 8 or 9 so if I can see anything it’s a miracle!



#17 nrcapes

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Posted 01 August 2020 - 12:05 PM

Stacking of M57 using Revolution 2 Imager at 16FLD (0.32 sec exposure), AGC Max 44.8. Frames were stacking but all I saw was a white field. When I changed to view individual frames as they were being stacked, I did get frames which I saved as AVI and then copied them as PNG. First shot, the SharpCap histogram:

 

SharpCap screenshot

 

Next, a frame from the stack:

 

M57 SharpCap AVI PNG
 
Obviously the mount is tracking and I am able to stack.  But  something must be wrong if I just get a white field while viewing the live stack. I'm making progress but still need help. Thanks!


#18 RazvanUnderStars

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Posted 01 August 2020 - 02:28 PM

A couple of comments:

 

  • you got a white field because the white level is set way too low, lower than even the histogram peak corresponding to the sky glow. Reset the histogram by clicking the top-right button that looks like a circle with an arrow. Then you can start adjusting it again and watching the effect. In most cases, it's the mid level that you need to adjust (to the left) and the dark level (move to the right to make the noisy sky background darker). In this case the image is underexposed moving the white level to the left is ok, but not beyond where you have pixels in the highlights, otherwise they get burned.
  • the exposures of each frame are way too short: 82 frames with 8.2s mean each frame is 100ms. This is not appropriate for DSOs where each EAA exposure is typically dozens of seconds (longer for dark skies, shorter in light polluted skies)
  • I see oblong stars even with these very short exposures. I'm still not sure the mount is tracking properly. It is possible that the short exposures freeze the stars image enough so SharpCap can stack even without tracking. 
  • it's very odd that the Camera Control Panel window is completely blank. It should be full with various controls (which would be helpful in debuging the problem). How do you control the camera if not through that panel?
  • SharpCap can automatically save each frame (as PNG or FITS), there's a checkbox on the screen. I didn't quite understand what "frames saved as AVI" meant but normally there wouldn't be a need to use a video format. 
  • it'd be helpful to post the contents of the log that appears in the Log tab


#19 nrcapes

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Posted 01 August 2020 - 04:40 PM

 

A couple of comments:

 

  • you got a white field because the white level is set way too low, lower than even the histogram peak corresponding to the sky glow. Reset the histogram by clicking the top-right button that looks like a circle with an arrow. Then you can start adjusting it again and watching the effect. In most cases, it's the mid level that you need to adjust (to the left) and the dark level (move to the right to make the noisy sky background darker). In this case the image is underexposed moving the white level to the left is ok, but not beyond where you have pixels in the highlights, otherwise they get burned.
  • the exposures of each frame are way too short: 82 frames with 8.2s mean each frame is 100ms. This is not appropriate for DSOs where each EAA exposure is typically dozens of seconds (longer for dark skies, shorter in light polluted skies)
  • I see oblong stars even with these very short exposures. I'm still not sure the mount is tracking properly. It is possible that the short exposures freeze the stars image enough so SharpCap can stack even without tracking. 
  • it's very odd that the Camera Control Panel window is completely blank. It should be full with various controls (which would be helpful in debuging the problem). How do you control the camera if not through that panel?
  • SharpCap can automatically save each frame (as PNG or FITS), there's a checkbox on the screen. I didn't quite understand what "frames saved as AVI" meant but normally there wouldn't be a need to use a video format. 
  • it'd be helpful to post the contents of the log that appears in the Log tab

 

thanks! OK, I will try longer exposures.  As far as the mount tracking, the object does not appear to move for 15 - 30 seconds at least when viewed on my R2 monitor. Is it possible that the oblong stars could be do to some defect caused in the transmission from the camera through USB to SharpCap? There really are no controls for the R2 camera in SharpCap.  The camera is controlled by a remote attached to the camera that lets me set length of exposure and gain.  It is an analog camera so that there aren't many controls other than that. I will test your suggestions as soon as I get a clear night.



#20 RazvanUnderStars

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Posted 01 August 2020 - 05:40 PM

Ah, ok, thanks for the explanations, I'm not familiar with the R2. If you see the object stationary, then the mount is tracking. The oblong stars are probably caused by imperfections in tracking. It's not that important right now, getting proper exposure is more relevant. If you haven't already, may I suggest you use the time until you the next test to go in detail through SharpCap's docs, they are well worth the time.

Also to answer your other question: transmission through USB is digital and therefore there's no distortion of the signal that could cause oblong stars.

Edited by RazvanUnderStars, 01 August 2020 - 05:44 PM.


#21 KTAZ

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Posted 01 August 2020 - 06:06 PM

Here are a couple of calculator outputs for you to consider:

T5eMxem.jpg

gALiRmj.jpg

 

First, and I know you know this, and we all try to stretch what we have as much as possible, but that camera is causing you several problems. To start with, it is just wrong for your rig...you need a really good mount and careful guiding if you want round stars with that camera. Not likely.

 

Second, SharpCap will not be able to plate solve. SC needs a FOV of between 1 and 2.5 degrees. Per that second calculator, you are getting much less than that. Some folks say .5 is enough, but I was not able to do it with .7.


Edited by KTAZ, 01 August 2020 - 06:07 PM.


#22 nrcapes

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Posted 01 August 2020 - 10:10 PM

Here are a couple of calculator outputs for you to consider:

T5eMxem.jpg

gALiRmj.jpg

 

First, and I know you know this, and we all try to stretch what we have as much as possible, but that camera is causing you several problems. To start with, it is just wrong for your rig...you need a really good mount and careful guiding if you want round stars with that camera. Not likely.

 

Second, SharpCap will not be able to plate solve. SC needs a FOV of between 1 and 2.5 degrees. Per that second calculator, you are getting much less than that. Some folks say .5 is enough, but I was not able to do it with .7.

Very enlightening. I consulted with High Point Scientific before buying the camera. Its less than one year  old. Maybe I can do a return or exchange. What camera would you suggest and where can I find the calculator? Thanks.!



#23 KTAZ

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Posted 02 August 2020 - 11:03 AM

Calculators are here:

http://astronomy.tools/

 

Help us understand what you are trying to do short and long term with AP. What are your preferred goals and targets?

 

For planetary, I am using the ASI224MC OSC at the moment. I also am experimenting with "how far I can push it" and am hitting a wall when it comes to trying to grab deep sky objects. The sensor size is just too small to grab enough sky at long focal lengths to do plate solving (not enough stars). So I cut down a spacer tube that can go in the place of my diagonal on my Celestron finder scope and can now at least focus and plate solve for Polar Alignment with SharpCap.

 

Ultimately, I am looking at a combination of an ASI294MC and ASI174MM for my future DSO camera/guide camera combo. That will be a $1500 investment plus an OAG is required. I'll get there.



#24 KTAZ

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Posted 02 August 2020 - 11:08 AM

And BTW, it is not that the 290 cannot do what you want it to do for planetary...it is just when you look at the much more demanding task of DSO that the CCD Suitability calculator should be looked at much more closely. Everything gets harder; chip size and pixel size get very important, not to mention your tracking mount.



#25 nrcapes

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Posted 04 August 2020 - 09:17 AM

Calculators are here:

http://astronomy.tools/

 

Help us understand what you are trying to do short and long term with AP. What are your preferred goals and targets?

 

For planetary, I am using the ASI224MC OSC at the moment. I also am experimenting with "how far I can push it" and am hitting a wall when it comes to trying to grab deep sky objects. The sensor size is just too small to grab enough sky at long focal lengths to do plate solving (not enough stars). So I cut down a spacer tube that can go in the place of my diagonal on my Celestron finder scope and can now at least focus and plate solve for Polar Alignment with SharpCap.

 

Ultimately, I am looking at a combination of an ASI294MC and ASI174MM for my future DSO camera/guide camera combo. That will be a $1500 investment plus an OAG is required. I'll get there.

Like most of us, I want to get the most bang for the buck with my gear. I have been very pleased with the ability of the Revolution Imager to let me at least SEE objects like M13 and M57 with a 6 inch Schmidt-Cassegrain in a Bortle 8 zone. I don’t have any motivation to spend long hours guiding in order to get beautiful DSO images. That’s why EAA is best for me. I’m not particularly interested in lunar or planetary, mainly because the planets are almost always behind my house. I bought the ZWO camera as an entry point to see what could be done with these limitations. SharpCap just befuddles me, and I was an IT guy for 20 years! I don’t think that I would get much better images by investing in a top of the line camera in a Bortle 8 zone. Same goes for spending $1000 for Hyperstar. So I think I will keep trying to push the R2 to its limits. I was able to get SharpCap to stack for several minutes on M57 the other night but didn’t see any noticeable improvement over the images I have gotten with the R2 alone and its internal stacking. Before long, M31 will be up, and that will be a challenge! It works well with globulars, too, but I think M51 would be beyond its capabilities.




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