DSC October - Actual astrophotography?

[MarkS]

Mark, how do you go cope when having to work the next day

I normally get 6 hours sleep in total.  Interrupted maybe.  But no worse than the interrupted sleep we used to get when we had young babies.  The main difference is that this particular baby has 3 metal legs and one huge eye!

Mark

[JohnP]

Also waiting to see everyone,s images from oct DSC

Me to....

[JonH]

Also waiting to see everyone's images from oct DSC

You might have to wait a little while before mine are ready. I have 90 x 5min subs of M31 stacked which took my poor old laptop something in the reign of 12hours to do!!! 
But still load of shorter ones I need to stack and figure out how to combine with the rest, which I still haven't a clue how to do yet. Then I need to process it all without a calibrated monitor.
If I have anything respectable to show this week it will be a miracle! 

[Fay]

 

Jon, you are doing very well, dont worry about it, you will soon sort it all out. dont like to tell you but, we all still have lots of problems when outside!!!!!!

[JonH]

Jon, you are doing very well, dont worry about it, you will soon sort it all out. dont like to tell you but, we all still have lots of problems when outside!!!!!!

I do hope so! That is exactly what keeps it interesting, if I could just plug everything together and have it spit a perfect image out every time there would be no fun in it at all and nothing to learn!

I have almost finished stacking the last of the subs now, just got to combine the different length exposures then start processing.
I am using Iris to combine the different sets of subs rather than messing about with photoshop, layers, masks etc etc. The method is a bit off an odd one and sorta making it up as I go along, it also means all post processing is done after combining the different length subs which is very unlike using photoshop. If it will work or not is another question altogether!
Watch this space.......

[JonH]

HA yea right! I really have no idea what I'm doing!
There are SO many variables with Iris figuring out what numbers to feed into it is proving the stuff of nightmares, for the most part I'm simply guessing.
I'm pretty sure I'm heading in the right direction though, all the data has come together as it should (I think) I just can't get it all to process out like it should.
It did just dawn on me though I need to go back a few steps as done something wrong that will make a big difference.

My head hurts! 

[MarkS]

Also waiting to see everyone,s images from oct DSC

Me to....

You'll have to wait for mine.  M31 is proving a real pig to process - another nightmare of background gradients - exaggerated because the data quality is good enough to perform a fairly extreme stretch.  It's the untold reality of using a DSLR on a very fast scope in a light polluted place.

Mark

[Fay]

Mark, i am sure it will come out as the most amazing M31 ever taken!!!

[JonH]

I'll be very interested to see how your M31 comes out compared to mine Mark. How many subs did you get in the end?

[MarkS]

I'll be very interested to see how your M31 comes out compared to mine Mark. How many subs did you get in the end?

101x5min subs plus 10x60sec plus 10x20sec so as not to burn out the core.  The HDR image created in PixInsight has a dynamic range of 26bits per channel.

[JonH]

That should make the difference between our results all the more interesting then!
I got 90 x 5min 20 x 2.5min and 16 x 30sec
So we have quite similar amounts of data the big difference will be your MUCH bigger and faster scope and processing.
How do I get Iris to tell me dynamic range of each channel?

[MarkS]

How do I get Iris to tell me dynamic range of each channel?

I don't know if you can in Iris.  PixInsight gives this info as it assembles the HDR image. 

Once you have the HDR image, the challenge is to compress the dynamic range into something that is perceived to be "right".

[JonH]

Yes, that is exactly where my problem is! Or at least half if it....
The dynamic range is there, just not all at the same time. But I have researched the merge_hdr and reduce_hdr commands some more since my last try and have a few good ideas where I might have been going wrong.
In fact I did have another 'revelation' moment earlier to use the merge_hdr command to stack them all at once rather than in three sets with the normal 'add a sequence' method.
But thanks to me deleting all the temporary files that means going threw the registration process again which will take a LONG time!

Smart one Jon! 

[RobertM]

It's good to see this as on-topic as all the other forum posts

Jon, From experience, I've found it very easy to overdo HDR in Astro images.  As Mark mentioned processing it into something that looks sensible and 'right' is the difficult trick.  I applied a bit of HDR to my recent Iris image but only very lightly to tease out more detail in the bright nebula, overdoing it risks loosing precious colour information.

Robert

[MarkS]

But thanks to me deleting all the temporary files that means going through the registration process again which will take a LONG time!

Time for a processing hint:

During image registration, it is the star matching calculations that take the time.  Iris saves the final image offsets and rotations it has calculated to a couple of LST files.  You can then quickly rerun the image registrations using the FILE_COREGISTER command without all the time time consuming star matching.  Clever eh?  Just remember to save the relevant LST files (you can rename them to something relevant and rename them back just before running FILE_COREGISTER to prevent them being overwritten).

All part of the power of Iris!

I often make use of this to perform stacks with different combinations of darks, flats etc.