Orion widefield- Exposures, Stacking and Processing advice

[Icesheet]

Hi,

Completely addicted to getting out and imaging on my Star Adventurer just now and learning a lot on all aspects from shooting right through to processing. My latest image is an Orion widefield stacked only the lights in DSS and processed in Photoshop.

Nikon D3200/ Sigma 70-200mm f/2.8 @ 120mm f/6.3 on Star Adventurer

23 lights - 105sec ISO800

15 flats (not used)                 

15 darks (not used)

 

If possible I would like some help in advice in three areas:

Exposures- When I was taking my lights there was no hint of the HorseHead at all, so I was very pleased when I managed to pull it out when processing. However, in doing so it has blown up M42 too much. So for my next session I would like to take some images that will enhance the HorseHead further but also limit the brightness of M42. Do I have to look at different exposure times and/or ISO to compliment each? Thinking ahead to the stacking how is it best to do this. Should I keep ISO the same and change exposure time? Or change ISO and keep time the same. Does it matter? As an aside I couldn't really go past 120sec without trailing. Not sure if that was due to polar alignment or what I should reasonably expect from the Star Adventurer?

 

Stacking- I tried, unsuccessfully on numerous occasions to get a stacked image with my flats and darks included on DSS. Anytime I tried I got a striped image with no detail whatsoever. Tried watching tutorials, messing with settings but no joy. In the end I just used my lights and they stacked no problem. Has anyone had this problem and found a solution to it? Perhaps there are issues with my flats or darks.

 

Processing- I'm definitely improving my processing skills and adding Noel's actions has helped. I still seem to have some aberrations and halo things around bright stars which from a previous post is likely down to the lens. However, I've now also noticed colour 'splats'. Almost as if someone has flicked an RGB paintbrush at my image. Anyone any idea on this??

 

As always thank you for your comments.

 

Chris

 

 

 

                                                                                             

[geordie85]

This is a very good technique for combining 2 different exposure lengths for a finished image.

http://www.astropix.com/html/j_digit/laymask.html

I usually start processing until the core of M42 is where I'd like it to be. Then duplicate the image and use that as the "shorter exposure stack" 

[Icesheet]

9 minutes ago, geordie85 said:

This is a very good technique for combining 2 different exposure lengths for a finished image.

http://www.astropix.com/html/j_digit/laymask.html

I usually start processing until the core of M42 is where I'd like it to be. Then duplicate the image and use that as the "shorter exposure stack" 

Thanks! This looks like exactly what I need! Will give it a go tonight.

[happy-kat]

Flats would help with the vignetting. If you are using a lens then you might find the app lightbox on either a phone or tablet gives a big enough light source to take your flats. Same iso and f just vary exposure to aim for histogram peak in the middle. That's how I take mine.

What about trying bias files instead of dark files.

[Icesheet]

17 minutes ago, happy-kat said:

Flats would help with the vignetting. If you are using a lens then you might find the app lightbox on either a phone or tablet gives a big enough light source to take your flats. Same iso and f just vary exposure to aim for histogram peak in the middle. That's how I take mine.

What about trying bias files instead of dark files.

Thanks. I actually took the flats using my ipad and white t-shirt as described elsewhere. The histograms look good with thin peaks just past half-way point. However, when I try and stack them with the lights and darks on DSS it always comes out as a striped pixelated screen. There is no detail in the image at all. I'll post an image when I get home.

 

Good point on the bias fames, they are no hassle so I'll add them too.

[geordie85]

1 hour ago, Icesheet said:

Thanks. I actually took the flats using my ipad and white t-shirt as described elsewhere. The histograms look good with thin peaks just past half-way point. However, when I try and stack them with the lights and darks on DSS it always comes out as a striped pixelated screen. There is no detail in the image at all. I'll post an image when I get home.

 

Good point on the bias fames, they are no hassle so I'll add them too.

Are you using the latest version of DSS?

[Icesheet]

3.6.6 as far as I can remember. It is a modified version for Mac though. 

I'll fiddle about some more when i get the chance.

 

[wxsatuser]

17 hours ago, Icesheet said:

Hi,

Processing- I'm definitely improving my processing skills and adding Noel's actions has helped. I still seem to have some aberrations and halo things around bright stars which from a previous post is likely down to the lens. However, I've now also noticed colour 'splats'. Almost as if someone has flicked an RGB paintbrush at my image. Anyone any idea on this??

As always thank you for your comments.

Chris                                                                                     

Lots of hot pixels and colour noise.

If you have more than a dozen or so subs use Sigma Clip when stacking.
This should remove them, it will also remove satellite and aircraft trails.

[Icesheet]

Thanks, that's the option that requires some input for clipping right? If so any suggestions as to where to start with that?

[wxsatuser]

If your using DSS let it decide what the settings should be, it's reasonably good at it.
You can fiddle with them as you get used to it.

Here are the normal parameters, load and check your subs and click 'stack checked pictures'.
Don't hit ok while doing any of this as it will begin stacking.
First screen
Basically lets you know what you have got in the way of files and settings.

Click 'recommended settings'
This what DSS thinks the settings should be, they may or may not be right but should work.
Green is set, you can click blue to change to green to set.

Cancel that box don't click ok and click 'stacking parameters', should get the next screen
I always found Mosaic Mode or Standard Mode work best.

Now click the 'Light' button, should get this screen.
This is where you can change the stacking algo, kappa sigma or median kappa sigma will remove outliers, mostly anything you
don't want in the image. I believe a minimum of 12 subs will work best.
As well as the LIGHT box you may well have boxes for darks, bias and flats, if loaded, where you can alter their algos.

Will do another post so this does'nt get to big.

[wxsatuser]

The rest of the settings.
This screen is alignment, Automatic normally works ok.

Next screen
Choose tiffs

Next is cosmetic, I found the settings in mine work ok.

and finally the output

[Icesheet]

Thank you very much! If I could give you more likes I would!

[happy-kat]

I don't use a t shirt when taking my flats with the tablet, I wonder if the stripes are from the weave in the t shirt.

[wxsatuser]

I would leave the shirt off as well and see.

[Icesheet]

Ok, thanks I'll try that next time. Most seem to suggest doing it but I guess it's just what works that matters!