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Linearity test camera ASI 294 MC (not cooled)

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#1 Hubert

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Posted 21 July 2019 - 04:08 PM

Hello,

 

I'm looking for the best way to do a linearity test of my not cooled ASI 294 MC, a colour one. Who can point me to the best free software to do this? I know how to make the subs but don't have any sofware to measure. I do have some astrophotography software like Pixinsight, Sharpcap and AstroImage (never used it).

 

Clear skies, Hubert



#2 Jamey L Jenkins

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Posted 21 July 2019 - 08:32 PM

Last Spring I performed a linearity test on my Atik 314L+ mono in preparation for learning photometry. At the time I didn't realize that my capture software provided that data in the corner of the frame in a small box...does yours?

 

I did make my measurements however with AstroImageJ by simply opening the FITS file in AIJ. When you mouse the cursor across the image the ADU called "value" is visible in the upper right corner. Or an ADU mean value of the entire image appears at the bottom of the window as the "mean value".



#3 Hubert

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Posted 21 July 2019 - 10:39 PM

Hi Jamey, thanks. That is what I was looking for. Thanks again.

#4 Ed Wiley

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Posted 28 July 2019 - 10:18 PM

The AAVSO Photometry Guide tells all about linearity tests.

 

https://www.aavso.or...hotometry-guide

 

Ed


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#5 vsteblina

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Posted 09 August 2019 - 08:22 PM

The AAVSO Photometry Guide tells all about linearity tests.

 

https://www.aavso.or...hotometry-guide

 

Ed

With all due respect...Ed.......NO...the AAVSO photometry guide does NOT tell all about linearity tests.

 

Give the manual to somebody without a background photometry or CCD imaging and see if they can complete the linearity test.

 

The past couple of days I have gone through the linearity test and had to get help from a imager.  The AAVSO manual assumes a level of expertise way beyond a typical beginner.  

 

Writing technical instructions for beginners is a tough task.  Not to critique the AAVSO manual, but technical instructions need to work on different levels.  The AAVSO photometry guide assumes, IMO, a imaging background that is beyond the beginner stage.


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#6 Hubert

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Posted 10 August 2019 - 02:28 AM

With all due respect...Ed.......NO...the AAVSO photometry guide does NOT tell all about linearity tests.

 

Give the manual to somebody without a background photometry or CCD imaging and see if they can complete the linearity test.

 

The past couple of days I have gone through the linearity test and had to get help from a imager.  The AAVSO manual assumes a level of expertise way beyond a typical beginner.  

 

Writing technical instructions for beginners is a tough task.  Not to critique the AAVSO manual, but technical instructions need to work on different levels.  The AAVSO photometry guide assumes, IMO, a imaging background that is beyond the beginner stage.

Hi Vsteblina, can you tell me what software that you used? I know the way to do it but still don't know a good software to measure the counts. I do have Sharpcap Pro an PI. I tried AIJ without result.



#7 Ed Wiley

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Posted 10 August 2019 - 12:46 PM

Linearity test: AAVSO Guide to CCD Photometry, Chapter 3, page 16.

 

So, yes, it is there, step-by-step. I cannot speak to the level of expertise needed to follow the instructions but they seems fairly straightforward to me. It is what we teach in CHOICE CCD1.

 

Granted, it does assume a CCD, but most of the principles are the same. (CCDs usually have a factory-set gain while CMOS cameras do not, for example.) There is probably a section in the DSLR manual as well and it might relate more to CMOS sensors, but I don't have that handy. 

 

Ed


Edited by Ed Wiley, 10 August 2019 - 12:52 PM.


#8 vsteblina

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Posted 10 August 2019 - 02:29 PM

These are the software packages I use:

 

https://www.willbell.com/aip/

 

and CCD Soft....see this comment

 

https://www.cloudyni...ned-to-ccdsoft/

 

Do you know anybody that is a imager in your area??

 

Vladimir



#9 vsteblina

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Posted 10 August 2019 - 03:47 PM

Last Spring I performed a linearity test on my Atik 314L+ mono in preparation for learning photometry. At the time I didn't realize that my capture software provided that data in the corner of the frame in a small box...does yours?

 

I did make my measurements however with AstroImageJ by simply opening the FITS file in AIJ. When you mouse the cursor across the image thecalled  ADU "value" is visible in the upper right corner. Or an ADU mean value of the entire image appears at the bottom of the window as the "mean value".

Ed, this is the level of information that the AAVSO guide does not provide. And it stops people as they search for ADU and cannot find it as called.

 

I would recommend that AAVSO, take a free software package and make it available on the AAVSO site. Then record somebody using the software package as they progress through the AAVSO photometry guide. That would make a huge difference in the success rate for people taking the CCD courses.  

 

Here is the video for Backyard EOS on UTUBE.  Having something like this for AAVSO photometry would answer lots of student questions up front. It would also allow people to work through the course on their own....and then when the course is taken "officially" the student level of achievement will be much higher.

 

https://www.youtube....h?v=z3gkw8bx7Aw

 

When I was working the Forest Service developed a cadre of individuals to teach National Environmental Policy Act (NEPA) regulations to Forest Service employees. That subject is drier and more difficult than photometry....trust me.

 

The Forest Service sent all of us to a week long session on adult learning theory. It was a very interesting session on how adults learn and we keyed the presentations based on it. I suspect within the AAVSO there are plenty of teachers and others that are familar with adult learning theory, that could help refine the AAVSO photometry guide.

 

It is a photometry is a difficult subject to teach. So a muti-media approach with videos, text, etc would allow more people to succeed and complete the course.

 

Here is some background info on adult learning theory....it is from a company that is selling these services. I have no knowledge of them...period. But they quickly cover some of the material that was in that week long session I attended.  

 

https://www.ej4.com/...is-it-important

 

Some ideas to consider.  BTW...I am working my way slowly through the guide. And once I complete it I will sign up for the course. I think this way, I will get more out of the course than taking it cold.



#10 S.Boerner

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Posted 10 August 2019 - 08:23 PM

A few questions before I try an answer. 

 

     What kind of camera are you using?  (DSLR, CMOS, CCD)

     What format are you saving the images in?  (Fits, RAW, Jpg, something else)

     When you say AstroImageJ didn't work for you could you be a bit more specific?  (Image didn't load, image loaded but you didn't know  what to do after that, etc?)

 

I've got AstroImageJ on my computer.  I  don't use it much but if I just File/Open and open a fits file it displays properly in a new window.  Up in the top right there is a box called Values that displays the ADUs as you move the mouse around the screen.  I would think that sampling the middle of the image ten times and taking an average would give you data that would be good enough for your purpose.

 

I used Sequence Generator Pro to do a linearity test.  I used it to both take all the images and to read the ADUs for each image with the Image Statistics Docking Module.  The problem is that SGP is $100 and I don't know that you'd like to go that far. 


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#11 Ed Wiley

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Posted 10 August 2019 - 11:01 PM

Declaration: I am not on the AAVSO staff nor do I represent AAVSO in any official capacity.

 

In CCD1 my job is teaching the first steps to becoming a photometrist. As explained in the manual (Ch. 3, p 22), students are responsible for learning their software. Terms like ADU (defined and mentioned several times in Ch 4) can usually be found with a bit of digging and even googling if not explained to satisfaction in the manual. Fact is, no manual is perfect, some effort might be required to fill in information. Of course, if you are in the course CCD1, all you have to do is query your friendly instructor. 

 

AAVSO does not recommend or provide a particular kind of software nor does AAVSO recommend a particular brand of CCD camera. IMO this is not only wise, but necessary. IMO AAVSO has no business recommending products it does not produce.

 

We instructors cannot be expected learn every piece of software. I will certainly help a student if I happen to know that particular piece of software. We are entirely unpaid volunteers. I am not a professional photometrist. My CCD1 budget is $0, my pay is the satisfaction of training up some observers who might be lead to measure variable stars. My contribution is teaching one course, but all should know to many functions of AAVSO are not carried out by staff but by volunteers, many of whom put in long hours.

 

Teaching principles: CCD1 is an interactive course with a peer-to-peer forum for daily exchange of results, regular challenge questions and the ability to exchange images and for evaluation. All students have direct email access to me and are encouraged to ask questions directly to me or (better) post them on the forum. I even provide images to students who are clouded out so that they can process and evaluate them as if they took these images themselves. They learn such interesting things as the fact that calibration does not get rid of noise and that flats and darks have both signal and noise. The take home is not noise elimination (impossible) but achieving high signal-to-noise ratios. In short, the basic principles that guide photometrists and how to produce science images that they can measure. (To get on my high horse: the idea that calibration is meant to eliminate noise is not correct. What you are eliminating,hopefully, is unwanted signal and variations in pixel response. IMO understanding that leads to a better understanding of photometry.)

 

Videos: The Henden videos are available and heavily discounted for AAVSO members. https://www.aavso.or...d-school-videos. Unlike me, Dr. Henden is a professional photometrist, one of the best.

 

Software: AAVSO members have access to VPhot as a member benefit and there is a CHOICE course for that program. IMO: well worth the cost of membership. There are other pieces of software and the CHOICE courses to back up some of them.

 

Ed

[E. O. Wiley]

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Edited by Ed Wiley, 10 August 2019 - 11:36 PM.


#12 Hubert

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Posted 11 August 2019 - 04:02 AM

Linearity test: AAVSO Guide to CCD Photometry, Chapter 3, page 16.

 

So, yes, it is there, step-by-step. I cannot speak to the level of expertise needed to follow the instructions but they seems fairly straightforward to me. It is what we teach in CHOICE CCD1.

 

Granted, it does assume a CCD, but most of the principles are the same. (CCDs usually have a factory-set gain while CMOS cameras do not, for example.) There is probably a section in the DSLR manual as well and it might relate more to CMOS sensors, but I don't have that handy. 

 

Ed

Hi Ed, I know how to do it, I just haven't the got sofware to measure. I have done in the past photometry of High Amplitude Delta Scutis stars. I used Maxim DL with an ST7.  But my Maxim DL is old and no longer usefull.  

 

In my first post I mentioned that I know how to do the test but haven't any software to do it. 

 

And like Vsteblina already wrote, the AAVSO manual gives the way to take the subs but that's al. A newby is there stucked and probably stops and goes to astrophotography wink.gif



#13 Hubert

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Posted 11 August 2019 - 04:12 AM

A few questions before I try an answer. 

 

     What kind of camera are you using?  (DSLR, CMOS, CCD)

     What format are you saving the images in?  (Fits, RAW, Jpg, something else)

     When you say AstroImageJ didn't work for you could you be a bit more specific?  (Image didn't load, image loaded but you didn't know  what to do after that, etc?)

 

I've got AstroImageJ on my computer.  I  don't use it much but if I just File/Open and open a fits file it displays properly in a new window.  Up in the top right there is a box called Values that displays the ADUs as you move the mouse around the screen.  I would think that sampling the middle of the image ten times and taking an average would give you data that would be good enough for your purpose.

 

I used Sequence Generator Pro to do a linearity test.  I used it to both take all the images and to read the ADUs for each image with the Image Statistics Docking Module.  The problem is that SGP is $100 and I don't know that you'd like to go that far. 

I use a ZWO ASI 294MC (not cooled) I save the images in FITS. When I loaded the images in AIJ, I always got a ADU of around a two digit nummer, way to low. 

 

But I'm going to install my old Maxil DL again, if I can find it on my old hard disk crazy.gif , and try to use it for the measure of the star counts.



#14 S.Boerner

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Posted 11 August 2019 - 07:44 AM

This is a screen shot of the upper right corner of my AstroImageJ window with one of my darks loaded and reading from the center of the image.  It is about 8,200 or 8200.  Is your similar?  I'm in the US.  You're in Belgium.  Could it be you are reading the , as a decimal point?

astroimageshot.png

 

MaximDL should work well if you can get it loaded.

 

 



#15 Hubert

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Posted 11 August 2019 - 07:58 AM

This is a screen shot of the upper right corner of my AstroImageJ window with one of my darks loaded and reading from the center of the image.  It is about 8,200 or 8200.  Is your similar?  I'm in the US.  You're in Belgium.  Could it be you are reading the , as a decimal point?

attachicon.gif astroimageshot.png

 

MaximDL should work well if you can get it loaded.

Hi Boerner, that's it!  I did read is as a decimal point. Oh my, now I feel somewhat stupid blush.gif   My defense is that I'm mainly a visual observer who was used to work 15 years ago with Maxim, but only for capture and analyse the subs. 

 

And yes, I found Maxim on a old hard disk and was busy all morning installing it. It gives me the same value as AIJ with the same frame.

 

Thanks all for this big help. waytogo.gif waytogo.gif waytogo.gif bow.gif bow.gif bow.gif


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#16 Ed Wiley

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Posted 11 August 2019 - 10:06 AM

Let us clear up a couple of things.

 

First, the statement " the AAVSO manual gives the way to take the subs but that's al" is, IMO opinion, incorrect. It not only tells you how to take the subs, it presents how to interpret the subs you have taken in the form of explicit graphs. It is true that the manual does not have instructions on how to find ADU counts for each piece of software and it does not teach you how to graph. Frankly, I have never used apps like Maxim so finding out how Maxim (or other software) counts would be up to you. If I knew I would tell you.

 

Second, please read the CCD CCD Photometry Equipment Requirements :"Students in CCD 1 and CCD 2 are assumed to have suitable software and know how to use it for such activities as taking, manipulating and analyzing images."

 

So the manual (and the course) may not be for everyone. You must come to it with some basic software and imaging skills. I encourage all to pick up those basic skills and join the effort.

 

Ed



#17 vsteblina

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Posted 11 August 2019 - 01:02 PM

Let us clear up a couple of things.

 

First, the statement " the AAVSO manual gives the way to take the subs but that's al" is, IMO opinion, incorrect. It not only tells you how to take the subs, it presents how to interpret the subs you have taken in the form of explicit graphs. It is true that the manual does not have instructions on how to find ADU counts for each piece of software and it does not teach you how to graph. Frankly, I have never used apps like Maxim so finding out how Maxim (or other software) counts would be up to you. If I knew I would tell you.

 

Second, please read the CCD CCD Photometry Equipment Requirements :"Students in CCD 1 and CCD 2 are assumed to have suitable software and know how to use it for such activities as taking, manipulating and analyzing images."

 

So the manual (and the course) may not be for everyone. You must come to it with some basic software and imaging skills. I encourage all to pick up those basic skills and join the effort.

 

Ed

First....Ed

 

Thanks for doing this.

 

It is a tough job and as you say you don't get paid for it. So thanks.....and don't take is personally.  I have worked with volunteers throughout my career.  It is much, much tougher being a volunteer than a paid professional.



#18 vsteblina

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Posted 11 August 2019 - 01:37 PM

I do think the AAVSO course does need to be redesigned such that most BEGINNING students sucessfully complete the course.

 

Way back at the turn of the century I bought a ST-7XE specifically to do variable star measurements. I live in a micro-metropolitan area, with only about ten amateurs and until recently NONE into imaging.

 

So I kept at it and without any resources to insure my success I would every four or five years.....try to do it on my own. And give it up. I did get to the point of taking variable star fields and estimating magnitudes, but never got to the point that I clearly felt I was getting GOOD data. 

 

I have worked with data throughout my professional career, bad data is worse than no data. 

 

This time around, there was an imager that moved into the Wenatchee Valley and though he doesn't do variables. He knows more than enough to interpret the AAVSO manual. Having him as a resource was enough to get over that first hump....the linearity exercise.  After a brief look, at the Calibration chapter he gave me a heads up on what will probably be my next roadblock.

 

The US military is primarily staffed with 18-25 year olds most of whom have not graduated from college. They run some of the most sophisticated systems on the planet under pretty stressful situations.  Teaching beginners how to do photometry should be a piece of cake.

 

Anyway....here are my suggestions. Ed, remember they are only worth what you paid for them. They are somewhat based on what I can remember about adult learning theory!!!

 

The AAVSO photometry guide is fine IF it is backed up with additional information.

 

I have not viewed Arne's presentations, but there does need to be a video lecture, that backs up and discusses the individual chapters in the Photometry Guide.

 

There need to be exercises for each chapter based on "rigged" data. In addition, to the written work, there should be a short video showing how to complete the exercise. At this point, a standard software package, should be used by to students. This would get students past where do I look??

 

After this I would encourage the students to do their own data collection for the exercise. After this the students can use their own software since now they know what data they are looking for. I could NOT get this step on my own. In fact, my imager friend had to get back to me on where to find the information in AIP and CCDSoft.

 

I think, following this type of format will signifcantly increase the number of students that are successful. 

 

I think the CCD choice class would be perfect for making sure that the data collected by students meets "science" standards. Really that is the whole point of the CCD class.

 

Getting beginners started on the path of collecting good photometric data will significantly get more people doing "science" with their CCD camera's instead of just pretty pictures. I don't think there are enough "pretty picture" imagers that want to switch to doing science, but I suspect there are plenty of beginners that are willing to give it a go.....if they succeed.



#19 Ed Wiley

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Posted 11 August 2019 - 06:14 PM

Valdimir: I am not the one to talk to about these issues. Ciriculum is determined by AAVSO staff, not us volunteers. I suggest that you contact AAVSO and give them your suggestions. It might also be a good idea to sign up for the CCD courses so that you have firsthand knowledge of what we actually do in the courses.

 

Ed



#20 vsteblina

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Posted 11 August 2019 - 07:24 PM

Thanks...Ed.

 

I will probably try and take the course this winter.

 

Sometime this week I should be on the Calibration chapter. That really is the most difficult part for me. So hopefully, with a little help from my imager friend I can get through this chapter. It is where I failed before.

 

Vladimir




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