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Another ASI294MC thread (help requested)

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#26 RoscoeD

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Posted 25 June 2022 - 04:00 PM

There I go...what?  I don't understand.  I have no clue how to debayer a master.  No clue how to apply that as a new master.  Recall I am a total noob at APP.


Edited by RoscoeD, 25 June 2022 - 04:00 PM.


#27 Borodog

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Posted 25 June 2022 - 04:15 PM

What software are you stacking in? Somebody can probably explain it for whatever tool you are using it.



#28 Borodog

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Posted 25 June 2022 - 04:17 PM

Borodog,

 

   That is an excellent idea for working around the red pattern issue with the IMX294 OSC camera when a narrow-band filter is not being used! I had not considered doing that but it makes perfect sense.

 

   I tried the idea but changed one thing. If you look at Flats that show this red interference issue, the green channel of the Flat always has some artifacts also due to the overlap and red and green response in the sensor at longer wavelengths. However, the blue channel is usually not affected at all, so I used the blue channel rather than the green. 

 

   Here is a highly stretched view of what I got:

attachicon.gifRoscoe_M101_wBlueFlats.jpg

 

   This looks just about as clean (color pattern wise) as the NoFlats example I posted in Post #11 above. However, since a flat was actually used, the dust mote and vignetting are fully corrected. Some experimentation may be required but this looks like something others should try if they have issues with the fixed red patterns in images from the IMX294 sensor= due to using an LCD Flat light source.

 

 

Roscoe,

 

   What this means is that you should be able to use your existing data to process your images. I can outline the general extra steps required but it may depend on the specific software you use and what tools are available to you.

  1. Stack your Dark frames into a Master_Dark
  2. Stack your Flat-Dark frames into a Master_FlatDark
  3. Calibrate your Flat frames with the Master_FlatDark
  4. Stack the calibrated Flat frames into a Master_Flat
     
  5. Debayer the Master_Flat
  6. Extract (or split the color channels) to get the Blue channel only of the Master_Flat (Blue_Master_Flat)
     
  7. Calibrate your Light frame using the Master_Dark and Blue_Master_Flat
     
  8. Proceed with your normal calibrated Light processing -- DeBayer, Align, Stack, etc.

   The steps in bold above are the added steps to a normal pre-processing workflow.

 

   I may go back to another user's data I still have and try this again but the method seems to hold great promise for folks having this issue when it is present in the Flats but not the Lights. I don't think it will help the more general case where a narrow-band filter is used in the image train for Lights.

 

 

John

I just made a feature request on the SharpCap forums asking that the "blue channel only for flats" be implemented as an option in the settings. I see this problem over and over and over again, to the point where people, like the OP, want to switch to a different camera because of it.



#29 RoscoeD

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Posted 25 June 2022 - 04:17 PM

APP



#30 Borodog

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Posted 25 June 2022 - 04:20 PM

I will let somebody more familiar with APP respond. If nobody does, I can explain how to implement this fix with a free tool like SiriL or PIPP, plus GIMP or any other reasonably advanced image editor.



#31 RoscoeD

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Posted 25 June 2022 - 05:02 PM

John et el. I'm very confused now.  I went outside and took a sky flat with a layered t-shirt.  No LED/LCD screen.  I got a similar pattern.  As excited as I was from your experimenting, I don't understand why I keep keep getting the same splotch pattern.  

 

This is becoming too much like work and not a hobby.  

T shirt Sky

 



#32 RoscoeD

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Posted 25 June 2022 - 05:35 PM

I have both the ASI294MC pro and ASI 294MM pro. I found I have the best luck with flats using 4 layers of t-shirt material and an LED tracing pad from Amazon, (~$15). Using my tablet with a white screen app worked well with my ASI183MC but not with the ASI 294 series. I have to use sky flats with my red filter on the ASI294mm pro, but the SII, OIII, Ha, green and blue filters seem to work fine the tracing pad.

What pad specifically?  Given the issue with this sensor I'd rather not guess but would rather start with something that we know has worked for somebody.



#33 gabebalazs

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Posted 25 June 2022 - 06:44 PM

I'm far from being an expert in this topic but I've just discovered something that may be useful. I have an SVbony SV405CC which is an ASI294MC Pro clone.

 

I've had problems with weird looking flats in the month or so I've owned it. I've read up on it and learned about ADUs, longer flats etc.

 

So last night I shot the Lagoon nebula, and finished late, so an hour ago (about 6:30 pm the day after imaging) I started doing the flats. I've read enough to have my flats > 2s (around 3.5 seconds long). What I noticed though is that even though that I let the camera quickly cool down to -10C (my standard temp for all kinds of frames), I noticed on my screen that my captured flats displayed a very faint darker area in the center 60%, sort of a beat up oval shape. The shape seemed familiar. I saw it on my final stacks weeks ago and it bugged me (in those stacks the center was overcorrected and brighter, showing the same shape as I just saw).

 

What I noticed though that as time passed the center oval shape got smaller and smaller. I took the same series of flats every 10 minutes as a test. After about 30-40 minutes the odd oval area completely disappeared. 

 

I presume even though the temp sensor was indicating -10C, only parts of the sensor actually reached that temp. Sensor temp was uneven in the first 10 minutes. I presume the center cools down slower. And I remember that in the past I took most of my flats the day after imaging and did not wait 30 minutes to start capturing them. I did them within a minute or two, as soon as the temp gauge showed -10C

 

I am stacking now the Lagoon nebula with various sets of these newly acquired flats. I also took dark flats, an hour after starting the camera, to have those also at the correct temperature. 

I'll see the results in a few minutes. 


Edited by gabebalazs, 25 June 2022 - 06:46 PM.


#34 bobzeq25

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Posted 25 June 2022 - 07:02 PM

What pad specifically?  Given the issue with this sensor I'd rather not guess but would rather start with something that we know has worked for somebody.

Easy way to tell if your pad is the problem (or if it's the camera).  Take the pad out of the equation.  Take a flat using a blank wordprocessing document on a laptop.  Or take a flat using an evenly illuminated wall (which I did when I started out).  Still blotchy?  It's not the pad.



#35 jdupton

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Posted 25 June 2022 - 08:06 PM

Borodog,

 

I just made a feature request on the SharpCap forums asking that the "blue channel only for flats" be implemented as an option in the settings. I see this problem over and over and over again, to the point where people, like the OP, want to switch to a different camera because of it.

   Keep in mind that this applies only to a very specific set of conditions. If SharpCap implements this a standard feature, even if optional, and doesn't full explain when it would apply, things will get worse than better.

 

   The specific conditions required for this to work are:

  1. You must be using an IMX294 sensor camera -- the ASI294MC-Pro or QHY294C.
    It will not be useful for any other camera types.
     
  2. You must ensure that you are NOT imaging with any filters in the optical train.
    If any Light Pollution, Narrow-Band, or multi-Band filters are being used, the method is useless.
     
  3. You must first verify that the fixed red color pattern is coming from the Flats only.
    -- To do this, you should run once calibrating with Flats and then again calibrating without Flats. If an extreme stretch shows the fixed red pattern in the image with-Flats run but NOT in the no-Flats run, then the method may be of some help. Otherwise, move on; this will not help

   When workarounds such as this are found for a very specific issue, all too often, it gets generalized and everyone with any random camera starts using the method and then comes back here reporting that it doesn't work or that their camera must be bad. We should be careful that anyone trying this understands exactly when it can be used to advantage and what very specific issue it might solve.

 

 

John


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#36 jdupton

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Posted 25 June 2022 - 08:12 PM

gabebalazs,

 

So last night I shot the Lagoon nebula, and finished late, so an hour ago (about 6:30 pm the day after imaging) I started doing the flats. I've read enough to have my flats > 2s (around 3.5 seconds long). What I noticed though is that even though that I let the camera quickly cool down to -10C (my standard temp for all kinds of frames), I noticed on my screen that my captured flats displayed a very faint darker area in the center 60%, sort of a beat up oval shape. The shape seemed familiar. I saw it on my final stacks weeks ago and it bugged me (in those stacks the center was overcorrected and brighter, showing the same shape as I just saw).

 

What I noticed though that as time passed the center oval shape got smaller and smaller. I took the same series of flats every 10 minutes as a test. After about 30-40 minutes the odd oval area completely disappeared. 

   This is almost certainly a very different issue. What you are seeing is most likely frost or dew forming on the center of the rapidly cooled sensor. Over time during the imaging session, that will slowly clear away as you observed. You can prevent it by cooling the sensor more slowly at the beginning of the session so that the condensation does not form at all. 

 

 

John


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#37 jdupton

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Posted 25 June 2022 - 08:28 PM

Roscoe,

 

There I go...what?  I don't understand.  I have no clue how to debayer a master.  No clue how to apply that as a new master.  Recall I am a total noob at APP.

   Unfortunately, I have never used APP. I did a quick search for a user manual that I could use to guide you but found that, like many other astro image processing software, not user manual seems to exist. It seems everyone prefers YouTube videos which I think are terrible when what you need is a reference. Since you have APP, you could post to the support forum and hope to get an answer regarding how to do what I outlined in Post #23.

 

John et el. I'm very confused now.  I went outside and took a sky flat with a layered t-shirt.  No LED/LCD screen.  I got a similar pattern.  As excited as I was from your experimenting, I don't understand why I keep keep getting the same splotch pattern.  

   The Flat you showed in Post #31 could be OK. We are not looking at the overall patterns in the Flat itself. Those are likely to look very much the same regardless of light source or method. All Flats will be whatever they will be as determined by your optics. The issue you are encountering is that the Flats taken with the iPad are quite different between the Red, Green, and Blue color channels. It is those differences that are causing you the Red splotchy patterns that are always the same. Normally, Flats taken with an OSC color camera will look very similar to identical in the Red, Green, and Blue channels.

 

   The method that Borodog suggested and I tested is that we know the Blue color channel is the least affected so we suck that out of the Flat then use it to calibrate all of your Lights (along with using your Master Dark which is working fine).

 

   Hang in there. Once you find out how to do each step of the modified process in APP, you will be good to go even when using the iPad. (Although, Wall Flats or Sky Flats may be marginally better.)

 

 

John


Edited by jdupton, 25 June 2022 - 08:38 PM.


#38 RoscoeD

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Posted 25 June 2022 - 08:44 PM

Victory.  I used my wife's laptop instead of my iPad and the flats came out much better. Here's the stacked image:

Victory
 
Needs some post-processing (I see what I suspect is LP gradient) but this is what I expected!
 
Thanks for everyone's help
 
(I need a better solution than the laptop; it's way too cumbersome)

 

 


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#39 Borodog

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Posted 25 June 2022 - 09:20 PM

jdupton,

SharpCap contains many options that are not applicable to all cameras or situations. That’s exactly why we need options, because equipment and circumstances differ.

#40 bobzeq25

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Posted 25 June 2022 - 11:14 PM

 

Victory.  I used my wife's laptop instead of my iPad and the flats came out much better. Here's the stacked image:

 
 
Needs some post-processing (I see what I suspect is LP gradient) but this is what I expected!
 
Thanks for everyone's help
 
(I need a better solution than the laptop; it's way too cumbersome)

 

First, that's a classic LP gradient.

 

Next, a response to your need.  Easy.  All you have to do is pay for it.  I use this.

 

http://www.spike-a.com/flatfielders/

 

Point the telescope up, sit this on top.  Shoot flats.  Done.

 

I bought it after I wearied of cumbersome solutions that were of uncertain quality.

 

It.                Just.             Works.

 

It even works with my RASA.  Set it on a table, point the RASA down at it.

 

Some remote observatory imagers hang it on a wall, have an Internet switch that turns it on.

 

It cares not about broadband or narrowband.

 

I do have some concerns over whether the 294 will have a weird incompatibility.  I've used it with a Nikon D5600, an Atik 460EXM, both 183s, both 2600s.

 

But if I were you I'd find someone who uses it with a 294.


Edited by bobzeq25, 25 June 2022 - 11:18 PM.


#41 rgsalinger

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Posted 25 June 2022 - 11:31 PM

I just don't really follow why people don't just use sky flats. I've been using them for years and years across many many cameras and scopes and I get excellent flat calibration. I must be missing something as I keep seeing people using all sorts of "things" that might or might not work. If I were the OP, I'd just take sky flats. Now, someone tell me why this is a bad idea because I just can't work out why people keep trying to re-purpose anything that emits light as a flat panel.

 

Rgrds-Ross



#42 Borodog

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Posted 26 June 2022 - 08:52 AM

Sometimes I shoot sky flats. Sometimes it just isn't convenient. I could go into the reasons, but trust me, sometimes it just isn't. I have an A3 sized dimmable tracing pad for use with my C8 and 1100 EdgeHD, and I use an ipad mini with my 70mm refractor. Both work well enough. Pretty much anything is a hassle, though, and if I could get away without flats I would.



#43 bobzeq25

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Posted 26 June 2022 - 10:46 AM

Sometimes I shoot sky flats. Sometimes it just isn't convenient. I could go into the reasons, but trust me, sometimes it just isn't. I have an A3 sized dimmable tracing pad for use with my C8 and 1100 EdgeHD, and I use an ipad mini with my 70mm refractor. Both work well enough. Pretty much anything is a hassle, though, and if I could get away without flats I would.

You can't.  They do more than most people think.



#44 RoscoeD

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Posted 28 June 2022 - 12:51 AM

So, I thought the "Not iPad" light source was the answer so I bought an LED edge-lit tracing tablet off Amazon.  Not as bad as the iPad, but not acceptable.  I'm going to start another thread asking for a SPECIFIC model of tracing pad that folks have gotten to work SUCCESSFULLY with the ASI294MC.

 

What's bizarre is the total color difference from the laptop screen Master Flat and the Tablet MF.

 

Laptop Master flat and final product (good)

Master Flat from Laptop screen
Victory

Tracing pad Master Flat and final product (not so good)

Tablet Master Flat
Stacked image using tracing pad
 
The MF from the tracing pad is RED whereas the laptop screen (the one that worked) is green.  This is driving me nuts.  I really don't want to drop 300 $amolians on a Spike-a-Flat that so many folks have said works (yes, I've spent a ton already, but my wife's patience has quite frankly run out).

Edited by RoscoeD, 28 June 2022 - 01:04 AM.


#45 jdupton

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Posted 28 June 2022 - 07:12 AM

Roscoe,

 

   The color of the Flat frames doesn't really matter. It reflects the spectrum of the light source which doesn't matter. However, for whatever reason, the Light calibrated with the tracing panel still shows some of the pattern you had before so it would be good to use a different one as is your plan.

 

   You don't need to care much about the color of the Flat. You just want one that doesn't have characteristics that cause the fixed red pattern to show up.

 

= = = = =

 

   By the way, have used the ASI Studio application to reset the white balance of your camera? If you ever use the native (non-ASCOM) driver method to connect to the camera the default settings in all ZWO cameras can cause issue with color balancing. See the following Post Quote regarding changing the default camera "white balance" color settings form those used for EAA (default) to balanced settings for long exposure DSO use.

 

 

 

The easiest way to change the WB settings is using the ZWO ASI_Studio application. Load that up and run it. Open the (Planetary Imaging) ASI_Cap application. Choose your ASI294MC camera in the camera selection box. Look farther down the right side of the application to the Control Section. Press the "..." circular button to the right of the Gain slider. This opens up the camera settings dialog.

 

   Next, choose the "Color" tab of the setting dialog. There are two setting there -- Red and Blue. First uncheck the "Auto White Balance Box" if it is checked. Then use the sliders to set both the Red and Blue to be 50 for each. The  default settings for these from the factory are 52 & 95. Both need to be changed to 50 & 50. After doing this once and pressing OK button in the settings dialog, and disconnecting from the camera should cause the new settings to be remembered for all applications. This is a one-time procedure for any given camera. The white balance settings are saved in the camera and don't have to be redone unless you want to use it for EAA and would like the factory settings restored.

 

   After you have done this procedure, you will need to take a new set of calibration frames for new imaging targets. All existing data will need to be calibrated with the old calibration frames you already have.

 

 

John


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#46 gabebalazs

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Posted 28 June 2022 - 09:29 AM

How is the uniformity on these cheaper panels?



#47 RoscoeD

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Posted 28 June 2022 - 09:31 AM

Interesting...somebody mentioned that in my other thread and I didn't know what they were talking about.  Now I do.

 

FYI I switched from a laptop to ASI AIR Plus which I suspect does not have the ability to make those setting changes.  I'll have to dig out the old hardware...



#48 Zambiadarkskies

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Posted 28 June 2022 - 09:56 AM

You can't.  They do more than most people think.

I am curious/needing educated here.  Apart from vignetting and correcting for dust spots, is there anything else that flat frames achieve?  I have been (lazily) quite often skipping flats - only with one particular configuration that I have never seen any vignetting with - and am wondering what I am missing.  It's sheer laziness and bad practise I know, but when it is late, cold and I have work in a few hours and need to pack down and get into the car for the (admittedly very short) drive home it is sometimes just too tempting.  And honestly speaking, the times I have skipped it my newbie eyes haven't seen any problems.  

 

On my FF DSLR it is a completely different story, but with my 533mc I just haven't seen the same issues.   



#49 RoscoeD

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Posted 03 July 2022 - 10:19 PM

For what it's worth, I retried my iPad with a blue screen instead of a white screen on a whim. Didn't make a  bit of difference...



#50 bobzeq25

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Posted 04 July 2022 - 01:52 AM

I am curious/needing educated here.  Apart from vignetting and correcting for dust spots, is there anything else that flat frames achieve?  I have been (lazily) quite often skipping flats - only with one particular configuration that I have never seen any vignetting with - and am wondering what I am missing.  It's sheer laziness and bad practise I know, but when it is late, cold and I have work in a few hours and need to pack down and get into the car for the (admittedly very short) drive home it is sometimes just too tempting.  And honestly speaking, the times I have skipped it my newbie eyes haven't seen any problems.  

 

On my FF DSLR it is a completely different story, but with my 533mc I just haven't seen the same issues.   

They also reduce fixed pattern noise.

 

Is that a big deal?  Depends on what you're imaging, and how well you're doing it, how much total imaging time you're doing (which relates to light pollution), how light polluted your skies are, how good you are at acquiring good flats, at processing the data....  If you have other noise because of other things not being optimal, your images may indeed not look different, the noise due to the lack of flats may be lost in other noise.   It's not rare for a beginner to say "I can't see any difference."  And rare (very rare?) to find an experienced imager who doesn't do them.

 

It takes me less than 5 minutes to do flats.  Point the scope up, put the Spike a Flat on top, adjust exposure, run off 30 flats.  An alternative is to do sky flats before the session, that doesn't keep you up any later.

 

Note that my advice is always aimed at helping someone do the best images their budget and talent will allow.  It's easy to just get something, and that's good enough for some people.  Personally, I like to maximize my results, this is hard work.  Flats, after you get it down, are an easy part.


Edited by bobzeq25, 04 July 2022 - 02:00 AM.

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