M20 Trifid Nebula + Questions

[lazjen (Chris)]

I've collected a number of images over a few nights for this nebula. I'm still trying various things to get the best image I can from it all. Most of this data is just incidental collection as I sort out getting things working at the scope - aligning, guiding, etc.

Details:

Taken from the backyard, streetlight blazing away...
Stacked with DSS 3.2.2, post processed in PS.
Mix and ISO 800 (60 sec) and ISO 1600 (30 sec) images. Around 70 in total I think after weeding out *many* crappy images. Darks taken on each night total about 40.

I'd like to drop to lower ISO in the future to reduce some of the star "bloat", but I'd obviously need longer exposures - something I'm not quite capable of achieving just yet.

Questions:

1. I notice that DSS makes a master dark to use for each ISO (and I assume if I had varying times within an ISO, there would be another master). I assume it uses the masters across the lights (again on a per ISO/time basis). My camera records the temperature with each picture, so I can see a large range of temperatures, so I assume the darks will vary greatly. Does DSS take note of the temperature data if it's there? Would applying darks to lights at specific temperatures give better results than using a master dark?

2. I found that saving the image from DSS - 16bit TIFF was the only thing PS liked - the image tended to have gradient bands or noise. Is it better to do minimal adjustments in DSS, save an image and post process in PS, or get as close as possible in DSS, then save, etc?

3. What alternatives have I got to using DSS? I've read a bit about PixInsight which looks interesting, but I've been wanting to get some good data (and a lot of it) before giving it a go - also I'm going through some large learning curves elsewhere that taking on PixInsight might be tough at this time.

Feel free to give any feedback or suggestions.



Google+ Post with a larger picture

[lazjen (Chris)]

Just for anyone dropping by in the future: there were quite a number of wonderful, helpful replies in this thread that were unfortunately lost in a recent HD crash for the site.

[pfitzgerald (Paul)]

And I for one wish they were still here as I hadn't copied them before the crash. :-(

Currently I'm using Nebulosity and then PS so I have very similar questions.

If the OP are able to re-post their suggestions that would be awesome.

Paul

PS Lazjen it's a nice image and apologies for the mini hijack ;-).

[rcheshire (Rowland)]

I use Pixinsight for preprocessing - calibration, alignment and integration ( stacking) and StarTools for post processing. DSS and StarTools is OK. The learning curve is not as steep. Ivo has produced some nice tutorials for StarTools. You can try the demo version for free - fully functional except for saving.

OK. I'll stick my neck out. My experience, not a sales pitch. StarTools is a set of modern unique algorithms that make up an integrated tool set for astro image manipulation/processing. But have a read of the developers notes. Cost is relatively low - not free. It's very clever the way it handles and cares for your data, tracking every move and preventing silly actions that just dont make sense, whether the image is linear or stretched.

[lazjen (Chris)]

I had a bit of a play with StarTools yesterday on this image. I could see its potential.

[lazjen (Chris)]

Originally Posted by pfitzgerald

And I for one wish they were still here as I hadn't copied them before the crash. :-(

Currently I'm using Nebulosity and then PS so I have very similar questions.

If the OP are able to re-post their suggestions that would be awesome.

Paul

PS Lazjen it's a nice image and apologies for the mini hijack ;-).

Thanks.

I've got some of the replies because I was subscribed to the thread, but not all of them because of the way it does notifications. Here's some of what I got:

rustigsmed has just replied to a thread you have subscribed to entitled - M20 Trifid Nebula + Questions - in the Beginners Astrophotography forum of IceInSpace.

This thread is located at:
http://www.iceinspace.com.au/forum/s...2&goto=newpost

Here is the message that has just been posted:
***************
hi chris,

nice job.

1. if you are worried about star bloat, you could try reducing it through photo editing rather than reducing ISO. http://darkhorizons.emissionline.com/PSStarBloat.htm
http://www.flemingastrophotography.com/starbloat.html
I believe there are a number of other methods, like copying the stars from a less intense image over the stretched image.


2. After the image is stacked in DSS i usually go straight to PS and or Astra Image.

3. I can't answer question regarding PI, its something I too am looking into, and i've stopped for now till reading the CPU system requirements, will need a new computer!!

cheers,

rusty

DJT has just replied to a thread you have subscribed to entitled - M20 Trifid Nebula + Questions - in the Beginners Astrophotography forum of IceInSpace.

This thread is located at:
http://www.iceinspace.com.au/forum/s...2&goto=newpost

Here is the message that has just been posted:
***************
Thats a great image with good detail and nicely processed. Well done.

With DSS, what I do is manually match the temperatures of the darks with the lights with a ratio of 2:1 then DSS create the master.

I use Backyard Eos to manage the capture process which records the temperatures of both types in the file names so its a pretty straight forward process.

The master dark I dont use again though unless restacking the same image, as there are too many variables in temperature night to night and when using a DSLR .

DSS wont take notice of the temperatures, you do have to manually match them though I believe there is some software knocking around that can do it for you. Over time I built a library of darks on those cloudy nights so you are not wasting imaging time.

I personally never do any pre-processing in DSS. If you are using photoshop your really dont need to and that includes letting DSS align channels. It means your start point in Photoshop is off.

I have also tried Nebulosity for registering images but find the workflow with DSS suits my needs at the moment plus of course its free and does the job very well and is indeed simple...

Get polar alignment and guiding sorted ..one step at a time

Jon has just replied to a thread you have subscribed to entitled - M20 Trifid Nebula + Questions - in the Beginners Astrophotography forum of IceInSpace.

This thread is located at:
http://www.iceinspace.com.au/forum/s...2&goto=newpost

Here is the message that has just been posted:
***************
Hi Chris,

After worrying a bit about data loss etc. I found that asking the 32-bit output from DSS then converting that to 16-bit in photoshop gave solid results.

I haven't mastered StarTools yet, but everyone seems to be saying good things about it.

Jon has just replied to a thread you have subscribed to entitled - M20 Trifid Nebula + Questions - in the Beginners Astrophotography forum of IceInSpace.

This thread is located at:
http://www.iceinspace.com.au/forum/s...2&goto=newpost

Here is the message that has just been posted:
***************

---Quote (Originally by lazjen)---
How do you convert the 32bit output? I have to save 16bit TIFFs for PS to operate on. Nothing else seems to work.
---End Quote---
This vexed me for ages, till I discovered it. In PS open the native DSS 32-bit TIFF that DSS autosaves, then choose Image->Mode->16 Bit. Use the "Exposure and Gamma" setting in the drop down menu ( the default is "Local Adaptation".)

Then play with curves, intensity and filters as you like.

It seems I had most of the advice given, from memory...

[graham.hobart (Graham stevens)]

I think the combination of DSS and Star Tools is a good one. Although MAxIm DL will also do your calibration and is good for a CCD. I have never stacked any RAW DLSRS with anything other than DSS.

[pfitzgerald (Paul)]

Cheers - thanks for this.

Paul

[Manav (Yugant)]

Nice! Setup almost same as mine and the image is something to aspire to!