My first stack s with the K-1, LMC and SMC. 200mm.

chris gunn said:

It's better than I expected, in terms of resolution (no AA filter), but I had hoped for better tracking (despite using it on a volcano, and being close to metal, and wearing a cell phone and doing a half-assed job of calibration). I'll experiment more later. Still looks fine sized down to 4k.

20s frames.LMC, 153 frames. I'm quite pleased! Seems to be sharper than the K5 despite the pixel pitch being about the same. My best result so far!

Click to expand...

chris gunn said:

SMC 180 frames. I'm not positive I have the colour right. Lots of variation on the web.

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Dan Paris said:

Wonderful shots chris, sharpness is impressive !

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I may disagree a bit about the white balance but this is a rather subjectif subject... Thanks. I used Daylight white balance of course said:

chris gunn, post: 62826380, member: 1723200"]
It's better than I expected, in terms of resolution (no AA filter), but I had hoped for better tracking (despite using it on a volcano, and being close to metal, and wearing a cell phone and doing a half-assed job of calibration). I'll experiment more later. Still looks fine sized down to 4k.

20s frames.LMC, 153 frames. I'm quite pleased! Seems to be sharper than the K5 despite the pixel pitch being about the same. My best result so far!



SMC 180 frames. I'm not positive I have the colour right. Lots of variation on the web.

Click to expand...

Click to expand...

chris gunn said:

Thanks. I used Daylight white balance of course, and the actual colours of the subject are objective. However I may well have messed up in my PP.

Click to expand...

Dan Paris said:

Dan Paris said:

Thanks. I used Daylight white balance of course, and the actual colours of the subject are objective. However I may well have messed up in my PP.

Click to expand...

I believe there's too much blue.

Check the tarentula nebula for instance, it is an emission nebula (so dominant colors should be red and to a lesser extent green), on your picture the the blue channel is the highest.



The best way to get objectively correct colors on astro shots is to use photometric data, you may try this free software

http://www.andreasroerig.de/regim/regim.xhtml

that calibrates color stars automatically using plate-solving. I have tried with your JPEG but there's not enough color depth, you may try with a TIFF output.

It is very easy to use: color -> automatic BV calibration then enter the name of the object (LMC) and an approximate field of view.

I'm curious to see what you get

Click to expand...

chris gunn said:

Dan Paris said:

chris gunn said:

Thanks. I used Daylight white balance of course, and the actual colours of the subject are objective. However I may well have messed up in my PP.

Click to expand...

I believe there's too much blue.

Check the tarentula nebula for instance, it is an emission nebula (so dominant colors should be red and to a lesser extent green), on your picture the the blue channel is the highest.



The best way to get objectively correct colors on astro shots is to use photometric data, you may try this free software

http://www.andreasroerig.de/regim/regim.xhtml

that calibrates color stars automatically using plate-solving. I have tried with your JPEG but there's not enough color depth, you may try with a TIFF output.

It is very easy to use: color -> automatic BV calibration then enter the name of the object (LMC) and an approximate field of view.

I'm curious to see what you get

Click to expand...

Serious answer! Ok, I spent 2 hrs working out how to add Java to Ubuntu. Got Regim going.

I tried entering my .fts file and .tif file

"Stars could not be matched,"

Tools->Plate solve gives 25 matching pairs, and a "Focal length = 0.0 mm"?

Then I tried the SMC Tif file, and it was happier!

63 matching pairs.

Sigma combined factors: 0.736, 0.788, 0.849

Normalized factors: 0.93, 1.0, 1.079

How's that?

EDIT: It occurred to me that it's the ,JPG that we are talking about. The SMC.JPG got:

1.0 : 0.87 : 1.33

I assume that's RGB, and so the Blue is quite high and the green is low. So, how does one adjust the WB easily?

Edit: ran it again and got: 1.0, 0.807523836782864, 1.1662517832166148 (24 pairs)

Also: 1.0, 0.8722480234600529, 1.5865392161835377 (42 pairs)

also: 1.0, 0.8718443563368131, 1.3346123357703497 (49 pairs)

Click to expand...

Dan Paris said:

Hi Chris,

sorry I don't know what happened with your FITS file.... did you enter the coordinates and FOV manually ?

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Dan Paris said:

More importantly, are you happy with the results of the calibrated TIFF file ? How does it look like ?

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chris gunn said:

I hadn't understood how the calibration worked. It actually recommends more blue and less green for the SMC!

I tried on the posted SMC => everything purple including the cluster. Bad.

I tried on the basic TIF (I pre-processed the RAWs with vibrance and sat before stacking) and manually black point and stretched => slightly grey/cyan galaxy, bit of purple on the edges, white and yellow stars in the cluster. Not too bad.

Then I tried calibrating that => everything blue.

Disturbing.

I assume you should only calibrate once? Only on basic RAW=> .FTS ?

Click to expand...

Dan Paris said:

I may have a hint about the issue. The calibration works great with 16-bit data from dedicated astro-cameras. However with 12- or 14-bit data from DSLR most of the time the brightest stars are overexposed (unlike you shoot low-ISO, rather short exposure times). When this happens the calibration routine is probably fooled ? I don't know if this applies to your data though.

Click to expand...

Dan Paris said:

Dan Paris said:

I hadn't understood how the calibration worked. It actually recommends more blue and less green for the SMC!

I tried on the posted SMC => everything purple including the cluster. Bad.

I tried on the basic TIF (I pre-processed the RAWs with vibrance and sat before stacking) and manually black point and stretched => slightly grey/cyan galaxy, bit of purple on the edges, white and yellow stars in the cluster. Not too bad.

Then I tried calibrating that => everything blue.

Disturbing.

I assume you should only calibrate once? Only on basic RAW=> .FTS ?

Click to expand...

Click to expand...

chris gunn said:

I manually added coords and size and managed to plate-solve my LMC.

Calibrating my LMC gives: 1.5031648470727776, 1.0, 0.40868180308333263

IE more red and much less blue.

Click to expand...

Dan Paris said:

Dan Paris said:

I manually added coords and size and managed to plate-solve my LMC.

Calibrating my LMC gives: 1.5031648470727776, 1.0, 0.40868180308333263

IE more red and much less blue.

Click to expand...

Good, how do you like the result ?

Click to expand...

chris gunn said:

It's better than I expected, in terms of resolution (no AA filter), but I had hoped for better tracking (despite using it on a volcano, and being close to metal, and wearing a cell phone and doing a half-assed job of calibration). I'll experiment more later. Still looks fine sized down to 4k.

20s frames.

LMC, 153 frames. I'm quite pleased! Seems to be sharper than the K5 despite the pixel pitch being about the same. My best result so far!



SMC 180 frames. I'm not positive I have the colour right. Lots of variation on the web.

Click to expand...

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Polacofede said:

I think tracking looks fantastic for 400mm.

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Polacofede said:

I never paid much attention to LMC i think i will after seeing this amazing samples.

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Polacofede said:

I also find K-1 astro better than K-3 even cropped.

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chris gunn said:

Dan Paris said:

chris gunn said:

I manually added coords and size and managed to plate-solve my LMC.

Calibrating my LMC gives: 1.5031648470727776, 1.0, 0.40868180308333263

IE more red and much less blue.

Click to expand...

Good, how do you like the result ?

Click to expand...

Well, I tried doing a RAW stack. I needed to use a lower star minimum brightness for the .FTS calibration. The result was everything yellow, which is silly. Your suggested Green and Red nebulae didn't happen.

Calibrating the pre-saturated TIF resulted in some green stars, the brighter Cyan areas surviving, reddish galaxy. Failure.

Here is a single frame with zero added Saturation or Vibrance. Just a diagonal line in curves to increase brightness/contrast (no BP subtraction):



It shows Magenta and Cyan nebulae.

So, where lies the problem? Maybe one possibility is it assumes more IR sensitivity?

I used ISO 3200, and you are right, it looks like a number are blown out. I'll try to use lower ISO in future.

Edit: I just noticed, this is the FA*400/5.6! I'm an idiot. I was wondering why f5.6 was min. Similar looking lenses.

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Dan Paris said:

Yes, I think that with the K-1 ISO 800 is high enough. With a 400mm lens with a large entry pupil, I would maybe even stick to ISO 400.

In my milky way shots I have already noticed a strong difference between ISO 800 and ISO 1250, star colors are much more vivid in the former case

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