35 replies to this topic

[MyBluOx]

Hi again Richard, my Post #3 here lays out the priorities...the thrust of my latter response to you was predicated upon the 2 minute capture timespan I saw in your FC .txt & I wanted to emphasise the short-comings of such a duration.

 

Probably my zealous response to what I see as one of the major furphies being constantly disseminated on these forums!

 

As well, I'm between a rock & a hard place when confronted with some of the perpetrators of the "rotational blurring" brigade: they are often non-imagers (true!) or relative newbies who seem to like to argue despite reality...as an inveterate user of 5 & 6 minute Mars captures I feel obliged to ask them to look at our website or forum images to display what these time-spans create.

 

Btw, like Jeff (the OP) you are also using incorrect gamma settings. (each of you are on either side of the spectrum!)

 

Gamma shoud be set at "50" for capturing...you can increase it for a focus aid but must capture at "50" - I overlooked this before because I confused the threads where I had made specific points about gamma to Abe in this thread:  https://www.cloudyni...my-mars-data/     

Kokatha man,

 

I was told by many people and tutorial's that Gamma needed to be turned off in FireCapture. Am I understanding you right, that it needs to be checked and set to 50%? Also should I use the Drizzle settings when stacking in Autostakkert?

 

Thanks for all the help.

 

Jeff

Edited by MyBluOx, 18 October 2020 - 08:33 AM.

[Kokatha man]

Perhaps you're misinterpreting what's been said, but gamma must be set at "50" for all your captures in FireCapture Jeff!

[Tom Glenn]

It turns out that turning gamma "OFF" has the same effect as leaving it "ON" and setting it to "50".  Both have the effect of not altering the gamma, and thus recording raw linear data.  This came straight from Torsten (who wrote FC).  

[Rac19]

It turns out that turning gamma "OFF" has the same effect as leaving it "ON" and setting it to "50".  Both have the effect of not altering the gamma, and thus recording raw linear data.  This came straight from Torsten (who wrote FC).  

Thanks. This has always been a bit of a mystery to me.

 

EDIT: Watching one of Torsten's tutorials, I notice that he recommends turning de-bayer off during image capture and de-bayering in AutoStakkert (or whatever). I assume that the gamma setting is irrelevant under such circumstances. This is something else that I have been wondering about recently.

Edited by Rac19, 19 October 2020 - 03:10 PM.

[Ittaku]

The debate about how long Mars could be stacked for without derotation had me interested so I conducted some experiments of my own:

https://www.cloudyni...-to-10-minutes/

My conclusion was more than 2 minutes would be detrimental at that focal length and Mars' size at the time.

Edited by Ittaku, 21 October 2020 - 12:03 AM.

[Rac19]

I accidentally exposed for 10 minutes (smaller frame) then 5 minutes (larger frame) last night and, going by the images below, 5 minutes is OK and 10 minutes too long. Both were high gain, short exposures (2 to 3 ms) with gamma turned off. The 10 minute image was de-bayered by FC, the 5 minute was de-bayered in AS!3?

 

These are the best 5% of 45,000 and 23,000 frames respectively, meaning 2,250 frames and 1,150 frames stacked.
 

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Edited by Rac19, 21 October 2020 - 01:46 AM.

[Tulloch]

Loathed as I am to weigh in on others' arguments discussions about imaging technique, I offer this for discussion. During my last session on Mars where I imaged for 300 seconds, I noticed a period of better quality in the data on FC's graph between frames 30000 and 70000 out of a total of 75000 total (250 fps data). On a whim, I used the "Limit frames" tool in FC to only stack the best 5000 frames in this reduced time period (around 160 sec) and processed it in Registax and Photoshop.

 

The animated png below shows the result, the top 5000 frames stacked in FC from both stacks, with identical processing in Registax and Photoshop applied. Now, I'm using a alt/az mount, so the reduced time period has halved the field rotation from about 1.4 degrees to 0.7 degrees, but that usually isn't enough to see any effect. However, I don't have much experience with Mars, so who knows?

 

Provided for information only. In some areas there appears to be more detail in the shorter stack, but other areas have more detail in the longer stack. What do people think?

 

Andrew

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[Ittaku]

Loathed as I am to weigh in on others' arguments discussions about imaging technique, I offer this for discussion. During my last session on Mars where I imaged for 300 seconds, I noticed a period of better quality in the data on FC's graph between frames 30000 and 70000 out of a total of 75000 total (250 fps data). On a whim, I used the "Limit frames" tool in FC to only stack the best 5000 frames in this reduced time period (around 160 sec) and processed it in Registax and Photoshop.

No doubt; I usually use that technique to find the "best period" and use only those 2 minutes for Mars. However, that's why I went to great pains to say the seeing was quite consistent. The quality graphs virtually didn't move for 10 minutes of frames in my experiment.

[Ittaku]

I accidentally exposed for 10 minutes (smaller frame) then 5 minutes (larger frame) last night and, going by the images below, 5 minutes is OK and 10 minutes too long. Both were high gain, short exposures (2 to 3 ms) with gamma turned off. The 10 minute image was de-bayered by FC, the 5 minute was de-bayered in AS!3?
 

It doesn't matter if you captured extra; try using the "limit" function in AS to limit it to exactly as long as you wish.

[Rac19]

It doesn't matter if you captured extra; try using the "limit" function in AS to limit it to exactly as long as you wish.

Thanks. Even though I have been using both FireCaptue and AutoStakkert for some years, I am only now exploring features such as this. In this case, I wanted to see how much blur there was for 10 minutes versus 5 minutes.

Edited by Rac19, 21 October 2020 - 03:03 AM.

[Tom Glenn]

Hi Tom!  With all due respect, the premise that Autostakkert aligns sections of the image individually and stiches the pieces back together is not at all how it works.  During the alignment phase, AS evaluates alignment error at each AP across the frame and then calculates a single alignment transformation which minimizes error across all of the alignment points for that frame, subject to weighting as you described.  It then applies that transformation to the frame globally, not in pieces as you say.  This is an important distinction.  If it moved the pieces around individually and reassembled them, then you would be correct that it compensates for differential drift, to a degree, but it just doesn't work that way. 

Ryan, please see link below for my response to you in the other thread.  Many of us have known for quite some time that Autostakkert does indeed stack APs individually and even uses different subsets of frames for each AP.

 

https://www.cloudyni...tes/?p=10599055