Stacking Tips? RAW vs JPG? ISO Setting? Camera Settings?

[DaveyLeo10]

I'm sure these questions have been answered many times on these forums but I haven't been able to find anything.

I've been stacking JPG images at either 800/1600ISO. Should I switch to RAW? Is my ISO target dependent or is there a max ISO I should never use?

My exposures on single frames are usually 30 seconds long.

What settings do you use? What camera settings could I change to get the most out of imaging. I own a Canon60Da.

I'd love to hear what settings you use and if you'd like to show off your results I never tire of seeing other people's work!

Thanks

David

[Steve Ward]

RAW always ... too much data lost with JPEGs ...

[hjw]

Keep the images uncompressed as long as possible. Raw (or TIF or FIT) for stacking and processing and only at the last step, before sending it to the web, convert to JPG. I always keep a TIF file for the record. You never know, you might learn a new processing trick and can always revert back to the old TIF file. As for the ISO setting it requires a bit of test and see. 800 and 1600 are good starting points. I use 800 for bright objects (M42 and Carina comes to mind) and I might push it to 3200 for faint galaxies. Above this you will just amplify the noise with the signal.

Good luck!

HJ

[DaveyLeo10]

Wow I thought 1600ISO was pushing it but I suppose it's all about how you process it. I'm lucky enough to have a really good camera. Is there anything in the camera's settings which you'd recommend changing? I have on that thing where the camera tries to process the picture once it's taken. Usually takes about the same time as the exposure time, says BUSY in big letters on the lcd screen lol.

I'm having a great time using it and I will switch to RAW. I have never taken a flat frame and I honestly don't know how I'd be able to with a 9.25' scope but how many dark frames should I take? I usually just go for half the amount of the light frames.

Any other tips are most welcome!

[kendg]

Always raw. As for iso, the higher the iso them higher the noise so that needs to be compensated for by stacking lots of images. It becomes a balancing act.

As for the camera. Canon cameras can do in camera noise reduction but this essentially doubles your time for an image. The exposure time plus the same amount of time to subtract a dark frame.

Now some Canon camera will do the noise reduction after shooting 4 frames. This way you don't have to shoot any dark frames at all. The cost is a 20% increase in time to take the images.

Lastly, you can set the camera to do raw only. You can make jpegs later.

Just my small opinions. Have fun. 

[kendg]

Just another quick thought.

For flats, I found a very nice piece of white  HDPE foam sheet. I cut a circle to fit the inside where the corrector plate is and take flats with this in place. 

It seems to work fairly well. I use lots of variations of iso/exposure times.

[wxsatuser]

The 60Da does ISO 1600 very well.

For faint stuff 1600 is fine, for stars like clusters 800 is good.

Turnoff the noise reduction as mentioned as I believe the 60D has on sensor dark current subtraction.

The only thing I would do is try to increase your exposure time as 30secs is quite limiting.

13x5minute exposures 60da and a Borg 67mm scope @f/3.8

Quite noisey but you take what you get.

[Pete Presland]

RAW always i hardly ever use JPEGs even when posting on line i try to use lossless PNG's where possible.  As for the ISO settings i have read pages and pages about ISO and it does or does not effect dynamic range? For every site that has said it does, there is another disputing it. I think all you can do is experiment with both and see which is better for you.

[laser_jock99]

Personally I use a slightly different approach (having found RAW stacking not that good with Fuji .RAF files).

My workflow is open each RAW file in Photoshop, apply the same basic processing to the file (colour balance/colour temp etc.) then save the file as 48 bit .TIF files. These seem to go through DSS much better. The stacked .TIF may then be further processed in the usual ways.

Having always worked that way- I also process my Canon RAW data this way too.

Regarding the ISO I tend to shoot ISO800 with the Canon camera and up to ISO3200 with Fuji as they are less noisy.

[DaveyLeo10]

I'm limited with my exposure times until I get a wedge for my Nexstar Evolution.

I guess there's no sure fire way to stack pictures but your advice really does help. I do have a question about Darks and Flats though. How many dark frames should I take? I usually go for half the amount of the light frames.

Also how do you take a flat frame? Is there a method to it? How much difference do flats make to the overall image?

[Davey-T]

Some disagreement about number of flats/darks/bias frames, some law of diminishing returns so once you get to 16 the improvement is less and less noticeable.

You can use any white light source for flats and yes you do need them, take them before taking the camera off the scope.

Turn off all the stuff in the camera that's annoying for astro, auto dark frame subtraction, auto rotate, auto switch off etc.

Dave

[Xiga]

Some useful info here:

http://www.astropix.com/HTML/I_ASTROP/SETTINGS.HTM

[D4N]

Personally I use a slightly different approach (having found RAW stacking not that good with Fuji .RAF files).

My workflow is open each RAW file in Photoshop, apply the same basic processing to the file (colour balance/colour temp etc.) then save the file as 48 bit .TIF files. These seem to go through DSS much better. The stacked .TIF may then be further processed in the usual ways.

Having always worked that way- I also process my Canon RAW data this way too.

Regarding the ISO I tend to shoot ISO800 with the Canon camera and up to ISO3200 with Fuji as they are less noisy.

The Fuji S5 pro cameras are odd creatures that is for sure.

Up to ISO 1000 it shoots with all pixels and doesn't use automatic in camera noise reduction. When you go above ISO 1000 the R pixels (R is the small pixels not the red ones) get turned off and the automatic noise reduction turns on.

This has the effect of greatly reducing the noise but it also greatly reduces the dynamic range.

There is actually less noise at ISO 1600 than ISO 800 on that camera but also less dynamic range.

It is a complicated camera to use and some software doesn't like the hexagonal pixel array which is probably why you have better luck in DSS after converting the files. Nebulosity handles the files far better than DSS.

/Dan

Sent from my iPad using Tapatalk

[DaveyLeo10]

So for a flat frame if i cover my scope's lens with a big sheet of paper and have light on nearby instead of pointing directly at scope that would work?

Also amazing link Xiga thanks for that!

[Davey-T]

So for a flat frame if i cover my scope's lens with a big sheet of paper and have light on nearby instead of pointing directly at scope that would work?

Also amazing link Xiga thanks for that!

Pretty much, you need to expose using AV mode I think and get the histogram peak about a third of the way from the left.

Dave

[D4N]

Remember that the light needs to be even, if the light is off to one side you will introduce a gradient.

Small scopes can use tablet or laptop screens set to white, larger scopes require a larger light source.

/Dan

Sent from my iPad using Tapatalk

[DaveyLeo10]

Does anyone have an example of what the histogram should look like for a flat frame? I've got a white wall near my scope so I figure I'll put a t-shirt over the lens and point the scope at the wall.

[Davey-T]

Haven't got a picture but you need the histogram peak about a third from the left, even better if you've got some software to measure it.

Dave

[DaveyLeo10]

Cheers Dave, gives me something to practise while the weather is bad.

[dph1nm]

Wow I thought 1600ISO was pushing it but I suppose it's all about how you process it.

ISO does not change the sensitivity of the camera to light. So whatever ISO you choose you need roughly the same total exposure time. After that, if you are really keen  you can worry about high ISO saturating quickly on bright stars, and low ISO suffering quantisation noise, pattern noise and/or higher read noise (although this depends to some extent on your model of camera). 

Nigel