Username:

Password:

Altair AstroDIO DehumidifiersAtik CamerasModern AstronomyDavid HindsNe3 Filters
UKAI is moving to Facebook

Author Topic: Horsehead gone weird  (Read 1040 times)

0 Members and 1 Guest are viewing this topic.

Offline Ian Straton

  • Poster God
  • *****
  • Posts: 1131
    • Stoneage Observatory blog
Re: Horsehead gone weird
« Reply #15 on: 00:02:02, 09 March, 2018 »
I don't think there could have been any light leakage, the dust cap was on the scope, the obs roof was closed and the lights out... hard to get it much darker... I could reshoot them or try something from a previous session?  how have you measured this value?

as for the bias, I have never used bias before,  I seem to remember reading they weren't required as the dark frame also contains the bias signal, is that not correct?

Offline chris.bailey

  • Administrator
  • Galactic Poster
  • *****
  • Posts: 10009
  • If at last you do succeed, don't try again
    • Rosemount Observatory
Re: Horsehead gone weird
« Reply #16 on: 08:52:28, 09 March, 2018 »
Ian

Your MasterDark has 14 bit ADU values of 512 pretty constantly. Your Lights vary obviously but are typically in the 530 range so not quite zero but very low.

Yes the Darks contain the Bias but so do the Flats. The (slightly simplified) calibration formula is Light-Dark/Flat-Bias. That gives a different answer to Light-Dark/Flat. Now if the Bias signal is very low the error will be small too BUT the error will be larger in the darker parts of the light i.e. where the dust motes and vignetting are. As such calibrating with flats that do not have the bias removed tend to under correct.

I'm now downloading all the files and will have a play.

Chris
LX200|ZS70|FSQ85|FLT110|Altair DF250RC|EQ6 Pro(Rowan Belt Mod)|ParamountMX
ATIK383L+/EFW2/OAG|Lodestar|Baader 36mm LRGBHaSIIOIII
Starlight Express SXVRH16/ONAG/FW|Lodestar X2|Baader 2" Filters
Starlight Express SXVRH814/ONAG/FW|LodestarX2|Baader 2" Filters
Lunt LS60PTBF1200|DMK41|Quark Chromo
Samyang 135mm f1.8

Offline Ian Straton

  • Poster God
  • *****
  • Posts: 1131
    • Stoneage Observatory blog
Re: Horsehead gone weird
« Reply #17 on: 09:21:04, 09 March, 2018 »
Ok, I guess its pretty easy to get bias.. I'll shoot a load when I get home tonight.

It would be interesting to have a look at the ADU values of images I have previously managed to process, what tool are you using to measure that value?

I look forward to seeing what you get, I have only uploaded a limited selection of the lights and darks, I figured uploading/downloading 160 odd frames would take us far into the diminishing returns calculation! but if you would like more lights or darks let me know.

Offline chris.bailey

  • Administrator
  • Galactic Poster
  • *****
  • Posts: 10009
  • If at last you do succeed, don't try again
    • Rosemount Observatory
Re: Horsehead gone weird
« Reply #18 on: 09:26:58, 09 March, 2018 »
Ian

I'm just mousing over the image in PI and reading off the value at the bottom of the screen.

I have downloaded all the images and though the signal is low, I don't get that solid blue image you do. In PI Format Explorer for RAW do you it setup as pure Raw - you just click on the Pure RAW button in Edit Preferences.

Chris
LX200|ZS70|FSQ85|FLT110|Altair DF250RC|EQ6 Pro(Rowan Belt Mod)|ParamountMX
ATIK383L+/EFW2/OAG|Lodestar|Baader 36mm LRGBHaSIIOIII
Starlight Express SXVRH16/ONAG/FW|Lodestar X2|Baader 2" Filters
Starlight Express SXVRH814/ONAG/FW|LodestarX2|Baader 2" Filters
Lunt LS60PTBF1200|DMK41|Quark Chromo
Samyang 135mm f1.8

Offline chris.bailey

  • Administrator
  • Galactic Poster
  • *****
  • Posts: 10009
  • If at last you do succeed, don't try again
    • Rosemount Observatory
Re: Horsehead gone weird
« Reply #19 on: 09:32:04, 09 March, 2018 »
Ian

This is what I get out of it (using just darks - there isn't a lot to the flats so I get very similar if I do use the flats)

Just colour calibrated quickly and stretched.

Chris
LX200|ZS70|FSQ85|FLT110|Altair DF250RC|EQ6 Pro(Rowan Belt Mod)|ParamountMX
ATIK383L+/EFW2/OAG|Lodestar|Baader 36mm LRGBHaSIIOIII
Starlight Express SXVRH16/ONAG/FW|Lodestar X2|Baader 2" Filters
Starlight Express SXVRH814/ONAG/FW|LodestarX2|Baader 2" Filters
Lunt LS60PTBF1200|DMK41|Quark Chromo
Samyang 135mm f1.8

Offline Carole

  • Poster God
  • *****
  • Posts: 1631
    • Carole Pope Astro-Imaging
Re: Horsehead gone weird
« Reply #20 on: 10:01:35, 09 March, 2018 »
I am glad Chris managed to get something out of your data.  I tried, but they wouldn't even load into DSS and DSS kept crashing, so I tried Astroart even though I don't yet know how to use that for coloured files, and it kept telling me the images were different sizes, so would not stack.

I thought the flats looked over exposed. 

Sorry I couldn't help.

Carole
Mount: HEQ5,  Telescopes: SW ED120 Pro and SW Evostar ED80 pro, WO ZS71 APO,  SW130PDS
Cameras: Modified Canon EOS 1100D, Atik 460EX, Atik314, DMK21, DBK21, Dual rig options. Observatory: SkyPOD & PZT
https://sites.google.com/site/caroleastroimaging/home

Offline chris.bailey

  • Administrator
  • Galactic Poster
  • *****
  • Posts: 10009
  • If at last you do succeed, don't try again
    • Rosemount Observatory
Re: Horsehead gone weird
« Reply #21 on: 10:43:00, 09 March, 2018 »
Astro Pixel Processor does a reasonable job with it on default settings. This is what I got entirely within APP other than resize for web.

Chris

LX200|ZS70|FSQ85|FLT110|Altair DF250RC|EQ6 Pro(Rowan Belt Mod)|ParamountMX
ATIK383L+/EFW2/OAG|Lodestar|Baader 36mm LRGBHaSIIOIII
Starlight Express SXVRH16/ONAG/FW|Lodestar X2|Baader 2" Filters
Starlight Express SXVRH814/ONAG/FW|LodestarX2|Baader 2" Filters
Lunt LS60PTBF1200|DMK41|Quark Chromo
Samyang 135mm f1.8

Offline Ian Straton

  • Poster God
  • *****
  • Posts: 1131
    • Stoneage Observatory blog
Re: Horsehead gone weird
« Reply #22 on: 12:35:11, 09 March, 2018 »
Ian

I'm just mousing over the image in PI and reading off the value at the bottom of the screen.

I have downloaded all the images and though the signal is low, I don't get that solid blue image you do. In PI Format Explorer for RAW do you it setup as pure Raw - you just click on the Pure RAW button in Edit Preferences.

Chris

Yes, this was a setting I changed recently (in-between my first and second efforts on this thread), currently set to Pure RAW

Offline Ian Straton

  • Poster God
  • *****
  • Posts: 1131
    • Stoneage Observatory blog
Re: Horsehead gone weird
« Reply #23 on: 12:44:00, 09 March, 2018 »
Chris, I am pleased to see you get a result out of my data but I still don't really understand why I'm getting such weird results.   Could you run me through your work flow so I can try and replicate your steps and see if I get the same result?

I have to say I am rather disappointed by the low SNR in my lights... I thought 5 minutes at iso 400 should give a reasonable signal without generating lots of noise, guess I'll have to try iso 800 instead..

Offline chris.bailey

  • Administrator
  • Galactic Poster
  • *****
  • Posts: 10009
  • If at last you do succeed, don't try again
    • Rosemount Observatory
Re: Horsehead gone weird
« Reply #24 on: 14:06:38, 09 March, 2018 »
Ian

Nothing at all special. Image Calibration (Darks only). Debayer (Auto, VNG). Star Align (Default Settings). Image Integration (Winsor Clip [4,3], Large and small Scale Rejection Enabled. I then just applied the unlinked channel screen stretch to the histogram tool.

With Astro Pixel Processor I ran it through with flats and darks with all default settings other than enable BPP in calibration tab and some local normalisation (1 and 3 I think).

This is a pretty faint area (other than Alnitak!) so with an OSC CCD I have used 10 minute subs and if doing it again in RGB may well go longer still.

Chris
LX200|ZS70|FSQ85|FLT110|Altair DF250RC|EQ6 Pro(Rowan Belt Mod)|ParamountMX
ATIK383L+/EFW2/OAG|Lodestar|Baader 36mm LRGBHaSIIOIII
Starlight Express SXVRH16/ONAG/FW|Lodestar X2|Baader 2" Filters
Starlight Express SXVRH814/ONAG/FW|LodestarX2|Baader 2" Filters
Lunt LS60PTBF1200|DMK41|Quark Chromo
Samyang 135mm f1.8

Offline Nomis Elfactem

  • Administrator
  • Galactic Poster
  • *****
  • Posts: 13006
    • The View From A Room
Re: Horsehead gone weird
« Reply #25 on: 14:15:07, 09 March, 2018 »
What camera is it Ian ?

Anything younger than a EOS600d and you'll be fine with ISO 800 and possibly 1600 (the later chips are a whole lot better than they used to be).

When I imaged with my 600d I'd hardly get anything at 5 mins on ISO 400.... ISO 800 always felt optimum  ;)

S.
Simon

Scopes: Astro-Tech AT-111EDT Triplet, TS65ED Quad, Orion ST80, Modded PST-90 Solar Scope, PST Cak (on loan)
Cameras: SXVF H694, Atik 16ic, Canon EOS 600d, DMK41, DMK21, QHY 5L-II (mono & colour)
Accessories: SX USB Filter Wheel, SX OAG, Baader LRGB Ha SI OII Filters, SharpSky Focuser
Mount: EQ6 (EQMOD), SW Star Adventurer, plus a lot (and I mean a lot) of other bits and pieces

Offline allyman

  • Full Member
  • ***
  • Posts: 205
Re: Horsehead gone weird
« Reply #26 on: 17:12:50, 09 March, 2018 »
Hi Folks,

I've not been following this thread but I had this or a very similar problem in Pixinsight so I recognise the weirdness. Basically I had screwed up during integrating as I was experimenting with Local Normalisation at the time. For the life of me I couldn't work out what I had done but the results were very similar, repeatedly. I fixed it by deleting my PI processing folder and starting again.

GrahamM.

Offline Ian Straton

  • Poster God
  • *****
  • Posts: 1131
    • Stoneage Observatory blog
Re: Horsehead gone weird
« Reply #27 on: 18:37:00, 09 March, 2018 »
What camera is it Ian ?

Anything younger than a EOS600d and you'll be fine with ISO 800 and possibly 1600 (the later chips are a whole lot better than they used to be).

When I imaged with my 600d I'd hardly get anything at 5 mins on ISO 400.... ISO 800 always felt optimum  ;)

S.

550D, commonly quoted sweet spot is "between 400 and 800" since you can only select *either* 400 *or* 800 I have generally gone with 400 for lower noise... looks like I . might need to boost up to 800 for the higher gain...

Offline Annie

  • Poster God
  • *****
  • Posts: 1026
Re: Horsehead gone weird
« Reply #28 on: 14:43:54, 10 March, 2018 »
I've used a 550D for 3 years now and it's always performed well re: noise at ISO800.

Annie
Pulsar Observatory; NEQ6/EQ6 wedge; HEQ5 Pro; TS Star 71 Astrograph; Takahashi FSQ 106ed; Skymax 150 Pro; Nikon D600; Canon 550D modified; Canon 5D Mk11; ZWO ASI120 MM-S; Lacerta MGEN stand alone guider.

Offline Ian Straton

  • Poster God
  • *****
  • Posts: 1131
    • Stoneage Observatory blog
Re: Horsehead gone weird
« Reply #29 on: 22:12:24, 10 March, 2018 »
Back to the original problem now, butterfly shaped stars after stacking...

Star alignment didn't report any errors.  it was reporting lots of RANSAC matches for each frame... Should I decrease the RANSAC tolerance so that it finds fewer matches - forcing it to match only the brightest stars?

 

ukbuysellRemote Imaging from AustraliaSharpSkyblank APTUKAI on Facebook
Powered by SMF 2.0.15 | SMF © 2006, Simple Machines LLC
DarkBreak by DzinerStudio. Theme modified by The UKAI Team

Page created in 0.441 seconds with 37 queries.
TinyPortal © 2005-2012