PIER-14 Sime 147

Post edited (deleted) out. I've been up too long and got brain fade, so have removed what I had written in error. 

Peter, 

Thank you. All these tips you give us are essential to know if we want to keep improving. 

I do the auto stretch all the time and tend to only view one filter set at a go. In cosmetic correction I will do a real-time preview, and on large images select a couple of small preview windows. I had to use it this time as the dark frames are only now going to be collected and weren't available. 

Any advice on the flat frames for this pier?I have in the past in similar but not as bad situations, tweaked the master flat using placed curves adjustments. When I used the master Ha flat I ended up with the original dark area being bright. It was after midnight by then so I ended up not doing any calibration. 

Best regards, 

Ray 

Hi Ray, 
When using blink, if you first open all of the frames you want to check then click the auto stretch box this will normalise the
preview window for al of the selected frames.

Now the weather has gone down hill again I'm using the time to take new darks for P14. They will be uploaded in the coming days.
The problem with this camera is it doesn't have a mechanical shutter, so dark
frames have to be done while the roof is closed at night. In addition we then
have to arrange for someone to go and cover the scope, its only then we can
take fresh darks. 

The over correction when calibrating your lights is normally down to how you prepare and create your master flats. Most imagers don't bother as normally
a simple flat will do what is needed. The effect becomes more noticeable when
the background ADU is very low. To get the best correction you must treat your
flats the same as the light frames and calibrate them. So in addition to doing
the standard darks I am also going do a set of Flat calibration files. this
will solve your "over correction" problem.
Regards
Peter

Yes we all get that at times
sussed it was the OAG prism then ?

Good morning Steve, 

I was definitely suffering from brain fade after too many late nights and starting to jump to conclusions while I was having trouble concentrating. There is something not right though. I haven't ruled myself out of the equation at this point. Going stir crazy these days. 

I had briefly considered an OAG, but this scope is unguided so would have no need for one. Besides, even an amp glow problem or OAG would not explain why this obstructed area remains in the same physical place (bottom of the image) on those taken both before and after the scope and camera are flipped at the meridian. 

Answers on a postcard or better still, as a reply below. 

Cheers, 

Ray 

I will take a look when I get back from the dentist. I hate the dentist lol

Although p14 is unguided it is indeed fitted with a back up plan OAG, just in case the mount struggled with 5 minute unguided subs (which it doesn’t) we made sure the imaging train had an OAG inline so we could guide if it became necessary

We were only discussing this a few days ago as it happens, now the mount is fully up and running and we know it’s capabilities, we will adjust the prism so it does not protrude into the light path on our next trip to Spain.

Steve

Ps P6 is setup the same but as it’s been installed longer and the mount capabilities were a known quantity on the last trip I was able to move the prism on that one then. 

A dentist eh, something rarer than hen's teeth these days around where I live. Good luck with the visit, I hate those places. 

Thanks for the update on the OAG situation, but my poor brain is still struggling with it.  

Wasps and Dentists, only things in the world i am scared of


Piers flips are always disorientation when it comes to calibration frames LOL

I beleive Pete in mid stack on this object at present

Steve

Peter, 

Thank you. All these tips you give us are essential to know if we want to keep improving. 

I do the auto stretch all the time and tend to only view one filter set at a go. In cosmetic correction I will do a real-time preview, and on large images select a couple of small preview windows. I had to use it this time as the dark frames are only now going to be collected and weren't available. 

Any advice on the flat frames for this pier?I have in the past in similar but not as bad situations, tweaked the master flat using placed curves adjustments. When I used the master Ha flat I ended up with the original dark area being bright. It was after midnight by then so I ended up not doing any calibration. 

Best regards, 

Ray 

Hi Ray, 
When using blink, if you first open all of the frames you want to check then click the auto stretch box this will normalise the
preview window for al of the selected frames.

Now the weather has gone down hill again I'm using the time to take new darks for P14. They will be uploaded in the coming days.
The problem with this camera is it doesn't have a mechanical shutter, so dark
frames have to be done while the roof is closed at night. In addition we then
have to arrange for someone to go and cover the scope, its only then we can
take fresh darks. 

The over correction when calibrating your lights is normally down to how you prepare and create your master flats. Most imagers don't bother as normally
a simple flat will do what is needed. The effect becomes more noticeable when
the background ADU is very low. To get the best correction you must treat your
flats the same as the light frames and calibrate them. So in addition to doing
the standard darks I am also going do a set of Flat calibration files. this
will solve your "over correction" problem.
Regards
Peter

Peter

I have always calibrated flats. It doesn't take much extra time, and any data I get at home is precious (North Wales skies being what they are). And since I have started using a CMOS camera I have used matched dark flats. I though that was the recommendation?

old_eyes

Peter, 

Thank you. All these tips you give us are essential to know if we want to keep improving. 

I do the auto stretch all the time and tend to only view one filter set at a go. In cosmetic correction I will do a real-time preview, and on large images select a couple of small preview windows. I had to use it this time as the dark frames are only now going to be collected and weren't available. 

Any advice on the flat frames for this pier?I have in the past in similar but not as bad situations, tweaked the master flat using placed curves adjustments. When I used the master Ha flat I ended up with the original dark area being bright. It was after midnight by then so I ended up not doing any calibration. 

Best regards, 

Ray 

Hi Ray, 
When using blink, if you first open all of the frames you want to check then click the auto stretch box this will normalise the
preview window for al of the selected frames.

Now the weather has gone down hill again I'm using the time to take new darks for P14. They will be uploaded in the coming days.
The problem with this camera is it doesn't have a mechanical shutter, so dark
frames have to be done while the roof is closed at night. In addition we then
have to arrange for someone to go and cover the scope, its only then we can
take fresh darks. 

The over correction when calibrating your lights is normally down to how you prepare and create your master flats. Most imagers don't bother as normally
a simple flat will do what is needed. The effect becomes more noticeable when
the background ADU is very low. To get the best correction you must treat your
flats the same as the light frames and calibrate them. So in addition to doing
the standard darks I am also going do a set of Flat calibration files. this
will solve your "over correction" problem.
Regards
Peter

Peter

I have always calibrated flats. It doesn't take much extra time, and any data I get at home is precious (North Wales skies being what they are). And since I have started using a CMOS camera I have used matched dark flats. I though that was the recommendation?

old_eyes

I agree photons are precious but you would be surprised how many don't bother to calibrate their flats....

A few more replies since I've come back. 

Re calibration :

One does if one can.

I have had a good look at the data and this is what I've managed to come up with....I've had a long discussion with Steve and will be arranging to have the prism adjusted. 
Although the flats do an adequate correction, on low signal target like Simeis 147 does make a challenging  process. 

Its such a stunning target....I think more time on this before it leaves us until next season would be a good idea?

Although it was easy enough to calibrate the prism out it was leaving some complex gradients from the prism. These were a pain to control.  Because of the gradients Steve and I have taken the current fortunate run of bad weather to get the prism moved before clear skies resume.
as soon as that is done I'll get some fresh flats..

Although it was easy enough to calibrate the prism out it was leaving some complex gradients from the prism. These were a pain to control.  Because of the gradients Steve and I have taken the current fortunate run of bad weather to get the prism moved before clear skies resume.
as soon as that is done I'll get some fresh flats..

That's good news. The bite taken out of the frame by the prism was very visible. I see from the splendid Simeis 147 image that with sufficient processing skills you can swerve the issue, for someone with limited processing skills, I need all the help I can get!

old_eyes

Although it was easy enough to calibrate the prism out it was leaving some complex gradients from the prism. These were a pain to control.  Because of the gradients Steve and I have taken the current fortunate run of bad weather to get the prism moved before clear skies resume.
as soon as that is done I'll get some fresh flats..

Peter - interested in the process you used to control the remaining gradient. I have just been looking at the LUM data for M31 (on the grounds that it ought to be simpler). I created the Master Darks and Flats using the Warren Keller recommendations for calibration and integration for PI. Then fed the lights through WBPP with the master dark and master flat. The integration shows a nasty residual gradient that spreads up into the M31 image. I would not know how to deal with that without messing up the target. DO I use a mask and work on the background separately? How did you do it for Sime 147?

old_eyes

I should have added an image to show what I mean

That was using the process I described and then one pass of DBE.

old_eyes

 How do you create your master flat, master dark and master bias frames ? I need to understand your work flow a little better  .......this is the key to good correction

 How do you create your master flat, master dark and master bias frames ? I need to understand your work flow a little better  .......this is the key to good correction

My normal workflow for my CMOS camera at home (OSC) is:

Everything recorded at the operating temperature[/*]
Typically 25 Darks, 50 Bias. Darks done at a range of exposures to match typical subs.[/*]
Flats and Flat Darks made using Voyager or NINA auto-flat process. Flat Darks recorded at the same exposure as Flats.[/*]

Integration Darks/Bias in PixInsight using settings from Warren Keller's book:

Combination      Average
Normalisation                                                   No Normalisation
Weights                                                             Don’t Care
Evaluate Noise                                                 OFF
Pixel Rejection 1
                Rejection Algorithm                       Linear Fit Clipping (>15 frames)
                Normalisation                                 No Normalisation
                Generate Rejection Maps            OFF

Flats Calibration using WK settings:
Master Bias                                                        Enable
                Calibrate                                             OFF
Master Dark                                                       Enable
                Calibrate                                             ON
                Optimise                                             ON

Flats integration using WK settings:

[b]Combination                                                     Average
Normalisation                                                   Multiplicative
Weights                                                               Don’t Care
Evaluate Noise                                                  OFF
Pixel Rejection 1
                Rejection Algorithm                       Linear Fit Clipping (>15 frames)
                Normalisation                                   Equalise Fluxes
Generate Rejection Maps            OFF

I normally use WBPP with matching master flat. bias and dark. Cosmetic Correction applied with both Master Dark and Auto Detect enabled with default settings.

Allow WBPP to select reference frame after ditching dodgy subs.

Usually, that gives me a good starting point, and I rarely have to tweak the initial Master Light. Then onto DBE and the rest of the process. The dark and flat calibration gets rid of most of the gradients.

This is the first time I have had to deal with a residual variation that is so noticeable. I have had to deal with some flare from adjacent bright stars in some images, but have generally not tried to remove it.

These are two single luminance images from the Pier 14 M31 project. We have no bias files in the calibration folder so the same process as above just without master bias.

Original raw file just STF autostretched:
[/b]

  

After calibration and cosmetic correction:



I you can suggest where I am going wrong it would be enormously helpful

Hi Richard, 

That’s what I was getting as we well on Simeis so I've left that for now. After I finish what I'm currently working on I think I'll try something different leaving the flats out altogether, if I still have no success. 

It's a shame that the galaxy wasn't nearer the top then you could have cropped it for now. Looking good mind you with that space around it, rather than just squeezing in 

I did have a bit more success without the flat and using DBE with careful placement. 


Ray

That is pretty much my settings....but the most important thing is the bias frame. When creating the master calibration frames your flats and darks must calibrated themselves with the bias frame., 
The other thing is I do mine all manually and dont use any of the scripts to create masters or stack light frames.
20x Bias frames were definitely done, I will ask Phil to check they are should either be in the Flat Darks folder or in with the Darks folders Marked up as BI for bias

Totally my fault guys - I dropped the Bias frames into the wrong folder and didn't notice.

They will be up and ready to download by 11AM

Regards,