strange data from narrowband

Questions and answers about processing in StarTools and how to accomplish certain tasks.
Rkonrad
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Joined: Sun Feb 07, 2016 2:55 am

strange data from narrowband

Post by Rkonrad »

Hello all,

It's been awhile since I was last on this forum...new look I see....hope everyone is well!

Being quite frustrated with my own primitive setup, I persuaded my wonderful wife to Christmas gift me with some points towards itelescope.. Nice gift. One of my favourite targets is the core of the Heart Nebula - the environs of Melotte 15. I used their Planetwave 20' f/4.5 (focal reducer). I imaged Ha for 50 min (5x10min), S11 (40 min (4x10min) and Oiii (4x10min). Even inspite of the specs of the scope, I was surprised that I had barely enough data. I may buy more points:)

There's definitely something odd about the Sii and Oiii data. I chose to bin them from the camera by 2 (400% by startools I believe) but kept the Ha layer at full as I was using this for the luminance. I resized the bin2 layers to the Ha but when I combined them in lrgb etc the stars were completely msis-aligned. When I edited this, the colours were unsubtle and blotchy - and way too strong for just Sii and Oiii. In fact, I was surprised that the S11 data was so much stronger than the Oiii! A little frustrated, I'm not sure what to do. I have processed just the Ha layer https://flic.kr/p/2kpAVTc . I'd love some help. Here is a link to the files:
https://www.dropbox.com/sh/ugdqqv188e7z ... mSBwa?dl=0 Thanks.

Cheers! Richard
almcl
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Joined: Wed Jan 21, 2015 7:15 pm
Location: Shropshire. UK

Re: strange data from narrowband

Post by almcl »

Hi Richard, nice to hear you are still up and running!

By no means an expert in this, but I think you need to stack all the narrow band images separately but use just one reference frame. There is, as you say, quite a bit of displacement between the Ha channel and Sii and Oiii and I don't think it will be possible to correct this in StarTools.

Depending on your stacking software (I use Deep Sky Stacker) you may need to get all three channels at the same resolution and then re-stack, this should produce three aligned channels which can be used in the compose module. I don't believe you can use compose to realign the mis-aligned Ha with the other two.

Sorry if that doesn't help much.
Skywatcher 190MN, ASI 2600 or astro modded Canon 700d, guided by OAG, ASI120, PHD2
happy-kat
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Joined: Sun Feb 01, 2015 11:31 am

Re: strange data from narrowband

Post by happy-kat »

Hi
If using DSS
whilst I am OSC I would like above stack each channel separately but make sure each stack includes your one reference frame. In one stack only depending on which channel it is the reference frame would be ticked. In the other two stacks the reference frame would be marked as the reference frame but would not be ticked. Select the reference frame on the best score (usually what I do).
Rkonrad
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Joined: Sun Feb 07, 2016 2:55 am

Re: strange data from narrowband

Post by Rkonrad »

Thank you for the "reference frame" advice. I never knew about this. Though I had to go "over to the other side" (Windows):) to do it. If anyone runs DSS successfully on Linux, I'd love to know how. So all channel are nicely lined up but.....now the data from the Sii and Oiii channels aren't contributing to any colour. So far all I get is the green from HA. https://www.flickr.com/gp/rkonrad/KL8r30

So I'm guessing this may have happened through 2 possibilities -

1. I resized them to full resolution with Image Magick (mogrify -resize 4008x2672 *.tiff) or

2. I opened each individual frames of Sii and Oiii which are FIT files and then saved them (automatically to TIFF). This was actually my first step.

I'm not sure if I'm clear enough....please let me know if you require clarification. Thanks for the help.


Cheers Richard
Burly
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Location: Northamptonshie uk

Re: strange data from narrowband

Post by Burly »

In dss make sure reference frame is in first tab , then load separate channel in the tab2 , tab3 etc , reference frame will be used for all .
Rkonrad
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Re: strange data from narrowband

Post by Rkonrad »

Thanks,

I will try that. I forgot to upload my new files. Could someone (Ivo too) look at the S2 and O3 to see if there is anything odd? Thanks.
https://www.dropbox.com/sh/17ha4ltuipjp ... GmY7a?dl=0
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admin
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Re: strange data from narrowband

Post by admin »

Rkonrad wrote: Sat Jan 09, 2021 5:00 pm Could someone (Ivo too) look at the S2 and O3 to see if there is anything odd? Thanks.
The S-II and O-III files appear to be corrupt (they are very small).
The H-alpha looks good, though very noisy. Given that Ha is usually the strongest of the signal, there may or may not be much signal in the S-II and O-III to work with. There is also a satellite trail visible, which should not be happening if you are stacking with the recommended settings applied (see links & tutorials section).

If you're on macOS, you may want to consider ASTAP as well (again, see links & tutorials section), as it appears to produce excellent results, on par with PixInsight's stacker, and works across all platforms.

Hope this helps!
Ivo Jager
StarTools creator and astronomy enthusiast
Burly
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Re: strange data from narrowband

Post by Burly »

on par with PixInsight's stacker, and works across all platforms.

Thats intresting ivo.
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Re: strange data from narrowband

Post by admin »

Burly wrote: Sun Jan 10, 2021 10:12 am on par with PixInsight's stacker, and works across all platforms.

Thats intresting ivo.
I've really been quite impressed with the stacks it produces - it is definitely worth having a look (this guide should get you started for optimising ASTAP for StarTools).

My statement was because a while back I was inspecting the same stack stacked in ASTAP and PI. They were completely identical (replicability given the same inputs and same algorithms/configuration is arguably a great litmus test). The only way I could tell they were different was due to a slight difference in the way dead pixel outliers were treated. The source material was "real world" and not perfect by any means.

As you may know, I hold PI's stacking capabilities in high regard, so this was a very interesting finding.
Ivo Jager
StarTools creator and astronomy enthusiast
almcl
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Re: strange data from narrowband

Post by almcl »

I've tried ASTAP a couple of times and had great difficulty getting it to work with the Canon raw files, but have since tried with the .fit files generated by my (new) ASI 2600. While it seems happier with these, it is painfully slow. A stack that DSS would have dealt with in under 3 minutes ASTAP is still churning away with after 20 minutes.

Has anybody else had a similar experience? Or have I mis-configured something?
Skywatcher 190MN, ASI 2600 or astro modded Canon 700d, guided by OAG, ASI120, PHD2
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