Jump to content

Stargazers Lounge Uses Cookies

Like most websites, SGL uses cookies in order to deliver a secure, personalised service, to provide social media functions and to analyse our traffic. Continued use of SGL indicates your acceptance of our cookie policy.

  • Announcements

    sgl_imaging_challenge_banner_rgb.jpg.9467c4d39b22ba8239e1b5ad252fcee2.jpg

Recommended Posts

DaveS    2,705

Been working on this again, still with old data. Loads of gradients that I can't seem to get rid of. I dumped a lot of [NII] subs that had rubbish stars, elongated and trailed.

TS 80mm f/4.4 six-element astrograph, 3nm Astrodons, ASI1600. I think I ran 5 min subs at max DR. Captured in Maxim DL processed in AstroArt5. Sigma Add stack, multiple gradient removals, ans several Histogram Stretch iterations.

Need more data. I have 2 hours of decent HII, but I want to add new [NII] and [OIII].

5a6e2a8ef3d61_NHOShortN.thumb.jpg.8f756e58d6d031bc66ea5f38a366e0b4.jpg

C&C welcome, and suggestions for further work. The JPEG looks nothing like the FITS I was working on, or how it looks on my monitor from Windows Photo Viewer. Pah!

  • Like 8

Share this post


Link to post
Share on other sites
MarsG76    2,058

Nice detail.... I'm glad to be seeing imaged captured by the ASI1600 since I'm in the market for one.... good work.

  • Like 1

Share this post


Link to post
Share on other sites
DaveS    2,705

Thanks guys.

Yes, the 3D effect jumped out at me as I was processing the RGB stack.

The original subs have a much wider FoV, unfortunately they are offset at an angle to each other needing a heavy crop. Hopefully the new data I capture (When I can) will be better aligned.

I still need to get rig of some annoying gradients resulting in an uneven background that multiple gradient removal algorithms failed to cure. Cleaner data should help.

Share this post


Link to post
Share on other sites
swag72    5,696

I'd be really interested in seeing the single NB channels side by side..... what does the NII look like compared to Ha and OIII for example?

Share this post


Link to post
Share on other sites
DaveS    2,705

Hi Sara

The [NII] is almost as strong as the HII with the [OIII] very weak and noisy by comparison. I'm at work ATM (Naughty!) so I'll see what I can do tonight.

  • Like 1

Share this post


Link to post
Share on other sites
swag72    5,696
4 minutes ago, DaveS said:

Hi Sara

The [NII] is almost as strong as the HII with the [OIII] very weak and noisy by comparison. I'm at work ATM (Naughty!) so I'll see what I can do tonight.

Thanks! I'd be interested to see not the different strength in the data, but the actual changes in where the data is.....SII is quite interesting on this one.

Share this post


Link to post
Share on other sites
DaveS    2,705

OK

I'll put up the individual stacks, though to get them on here I may have to post JPEGS. I have a Dropbox account (Which I've hardly used) so I'll try to dropbox the original FITS files.

Share this post


Link to post
Share on other sites
swag72    5,696

I'm not worried about the raw data .... Just a quick stretch jpeg to show the difference would be interesting :) 

Share this post


Link to post
Share on other sites
DaveS    2,705

OK, for Sara @swag72

Firstly, the HII

5a6f70de53d34_HIIstretchforSara.thumb.jpg.8e72df3e0d9c88fb2d603421f28af27c.jpg

Next the [NII]

5a6f70e529f6a_NIIstretchforSara.thumb.jpg.2dbdfa66327960d372f7631cbb04f18f.jpg

Lastly the [OIII]

5a6f70d8533e4_OIIIstretchforSara.thumb.jpg.f767442b4eb26d999ca79924547425f9.jpg

As I intimated, the [OIII] is horribly noisy and all suffer from gradients, the [OIII] worst of all, probably due to imaging in less than brilliant conditions. All are from 5 min subs using the Max DR setting in the ZWO driver.

I will have to recapture good data and dump these dodgy files when I do. I'll probably keep some of the HII data captured most recently.

  • Like 2

Share this post


Link to post
Share on other sites
swag72    5,696

Many many thanks for this Dave - Most interesting........ :) 

  • Like 1

Share this post


Link to post
Share on other sites
carastro    2,500

Very interesting more data in the N11 image.

Carole 

  • Like 1

Share this post


Link to post
Share on other sites
DaveS    2,705

You're both very welcome :wink:.

When I first looked at the [NII] data I thought I'd made a mistake and used the HII filter, they're so similar. I think that similarity is what gives the 3D effect.

Share this post


Link to post
Share on other sites
DaveS    2,705

Added more data to the stacks, and dumped some dodgy [OIII] that was very noisy. I also did a lot of pre-processing before stacking. Each set of data was individually stacked and gradient reduced before each group of hydrogen, nitrogen and oxygen data was individually aligned and combined, to give the three components. These were then aligned with each other before each was given a preparatory sequence of histogram stretches. After combining in the NHO palette there was a lot of cropping needed, to get rid of the horribly skewed alignment borders. Another gradient reduction was applied before many small iterations of histogram stretch, with and without curves to give the final result.

5a835f67a6154_AllDatapreprocessed.thumb.jpg.654c03ac1bb81155cd4ac7e03588cdde.jpg

Not entirely sure it was worth the effort, as I think my first version was better.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Recently Browsing   0 members

    No registered users viewing this page.

  • Similar Content

    • By moise212
      Season greetings!
      Got my 80 Esprit around one week ago and yesterday was the first clear-ish night since. I came to my parents' for Christmas and here the skies are much better. I went to a hill nearby where our galaxy was visible. I had an EQ5 which I didn't polar align very well. I tried to start my RPi3, but it didn't connect to my mobile router so I had to forget about it. I was limited to 15s or 20s subs. The scope is quite heavy, heavier than I expected, it doesn't balance well with a Canon 550D attached. I had to tighten its dovetail towards its end as much as I could and the setup was still camera heavy a bit. Anyways. I left it to cool for maybe half an hour and it didn't reach thermal equilibrium perfectly. Focuser is very good, no slip with the DSLR and tightening it doesn't shift focus. No tilt either.
      I bought my scope from FLO and checked by Es.
      Here are some pictures taken through it, I only had the camera, no visual stuff.
      M45 is 151x15s: https://drive.google.com/open?id=1CbAuNQCGkQPSsPB11UOBkye3Y8EnzNDL
      M42 is 14x20s: https://drive.google.com/open?id=1dVgAxK8LQ4jXqPDlv2G0CVjV88UnsU9u
      M37 is 10x20s: https://drive.google.com/open?id=1iITFwXffhGvAi4dUbE_qR9_9VQVJszPT
      All ISO1600. Darks and bias, no flats.
      Today are exactly 2 years since I took my first astrophoto. Quite some progress since then.
      Clear skies and happy new year!
      Alex



    • By DaveS
      90min HII, 72min [NII], and 80min [OIII] in 2 min subs with the 80mm f/4.4 and ASI1600 MMC camera through 3nm Astrodons. Piggy backed on the 130 f/7 mounted on the DDM60 and encoder guided.
      Sigma Add stacking in AA5, then gradient removal, alignment and Trichromy with [NII] mapped to Red, HII to Green, and [OIII] to Blue, following the Hubble Palette.
      Multiple Histogram Stretches, and a Low Pass filter to get rid of some of the noise. The RGB stack needed a serious crop as the [OIII] subs were at a steep angle to the other data, which is a pity as I can see plenty of outlying detail in the individual stacks.
       

      I'm not taking this particular image any further as the data is too short. I've already got another 2 hours of HII in 5 min subs which I'll stack and add to the existing HII stack. The [OIII] I think I'll bin as it's so badly skewed, I'll try to replace it with 5 min subs properly aligned. The [NII] is OK as it stands, but I'll try to add to it.
      When I'll be able to get more data is a moot point, as the weather here has been dire. There *may* be a couple of windows coming up, but I'm not counting on them.
       
    • By moise212
      Happy to see the stars again last night, though cirrus clouds were everywhere. With some luck I got some (short) time with lower cloud density and I pointed the scope towards the Orion. 32x30s usable longest subs, 15x10s for the core and I also used 14x20s taken on the 25th to remove the big halos caused by the brighter stars seen through clouds. I could not expose longer, I only had my DSLR and my EQ5 mount, no intervalometer.
      The second picture contains some narrowband data I had, which I added in a very small amount to the RGB image. Ha as red and O3 as G and B. This is taken through another lens and it is just an experiment.
      The scope seems to perform very well. I can't wait to see what I can get in proper conditions, but it seems that I have to wait a while for this.
      Clear skies!
      Alex


    • By Tommohawk
      Funny thing - I have an ASI1600 + EFW and am connecting to SW coma corrector which requires 55mm spacing. The camera is 6.5mm the EFW is 20mm, total 26.5, so 28.5mm spacer required - sound correct hopefully?
      But the suppllied spacers are 21mm and 16.5mm which doesnt help (and doesnt seem correct even for a colour ASI1600 with no EFW) There is also a 11mm female/female adapter and a very short 1.5mm male/male adapter, so I guess I could use the 11mm F/F followed by the 1.5mm M/M + the 16.5 giving 29mm but this seems a bit complicated!
      Just wondering what other folk do - I cant be the only one with this problem. Any thoughts please?
    • By CCD Imager
      Here is an image I took last month, around 8 hours of data. Taken with an FSQ and ASI 1600M Cool camera

×