Author Topic: NGC6188 and NGC6144 in 3nm NII  (Read 3836 times)

Offline avandonk

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NGC6188 and NGC6144 in 3nm NII
« on: 2015 May 01 17:04:04 »
Data
       22x16 min 3nm NII at -35C. Corrected with PI for flats and darks and aligned and stacked.

Large image here 7MB

http://d1355990.i49.quadrahosting.com.au/2015_05/NGC6188_NII.jpg

Full resolution data as 32bit compressed fit 55MB


http://d1355990.i49.quadrahosting.com.au/2015_05/NGC6188_NII_32b.zip



Would be very interested to see what others can do with this data.

Bert

System Equipment



Astrograph is an Officina Stellare RH200 which has a focal length of 600mm and is F3. Clear aperture is 200mm.
FLI Atlas Focuser.
FLI ten position filter wheel CFW-3-10 with 50mm square filters.
Astrodon E series LRGB and HA, NII, SII and OIII 3nm NB filters. Also a continuum filter 5nm.
Camera is a FLI PL16803 which has a sensor size 36.8 X 36.8 mm.
The FoV of this system is 3.5 X 3.5 degrees.
Mount is a Software Bisque PMX.



Offline RickS

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Re: NGC6188 and NGC6144 in 3nm NII
« Reply #1 on: 2015 May 03 20:02:41 »
Looks like you still have problems with flexure and/or tilt on that set up, Bert.

Cheers,
Rick.

Offline avandonk

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Re: NGC6188 and NGC6144 in 3nm NII
« Reply #2 on: 2015 May 04 15:31:43 »
Thanks for that RickS. What program did you use to produce these maps?


I have the system far better aligned and getting better. Some residual flexure is still a problem. This is now only occurring at the front plate of the ten position filter wheel due to its asymmetry. It is more noticeable when the optic axis is near vertical or low near the SCP. Alignment does vary slightly over a full data acquisition run. This has made alignment difficult when it varies with mount orientation. The CFZ of the RH200 is about ten micron so any flexure of this order will be noticeable especially with a larger sensor than RH200 specifications.

I may have to go to the two wheel filter wheel.

I designed this system to get low noise very very dim stuff. If I want perfect stars I will get an RC telescope that cannot record any dim stuff.

Bert
« Last Edit: 2015 May 04 15:53:44 by avandonk »

Offline Geoff

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Re: NGC6188 and NGC6144 in 3nm NII
« Reply #3 on: 2015 May 04 15:49:59 »
Thanks for that RickS. What program did you use to produce these maps?

Bert
Script>Batch Processing>Subframe Selector
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Offline avandonk

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Re: NGC6188 and NGC6144 in 3nm NII
« Reply #4 on: 2015 May 04 16:38:38 »
Thanks Geoff

Bert

Offline Zocky

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Re: NGC6188 and NGC6144 in 3nm NII
« Reply #5 on: 2015 May 05 13:33:21 »
Script>Batch Processing>Subframe Selector
I thought that those maps are produced by Script/Image Analysis/FWHMEccentricity.
Could someone please give an explanation what those maps represent and how to interpret them? 
Skywatcher ED 80/600 with FF/FR x0.85; HEQ5-pro mount
SBIG ST-8300M, FW5 with Baader LRGB Ha7nm filters
https://www.flickr.com/photos/zoran-novak/

Offline RickS

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Re: NGC6188 and NGC6144 in 3nm NII
« Reply #6 on: 2015 May 05 17:02:18 »
I thought that those maps are produced by Script/Image Analysis/FWHMEccentricity.
Could someone please give an explanation what those maps represent and how to interpret them?

You can create the FWHM and Eccentricity maps with either script.  I did the ones in this thread with FWHMEccentricity but SubframeSelector will produce them as well (Output Maps button.)

The maps show how your star sizes (FWHM) and shape (Eccentricity) varies over the FOV.  In a perfect world you'd have a consistent and small FWHM all over the field and lovely round stars everywhere, i.e. low Eccentricity - the SubframeSelector doc suggests that anything lower than 0.42 looks round.

Cheers,
Rick.

Offline kolec

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Re: NGC6188 and NGC6144 in 3nm NII
« Reply #7 on: 2015 May 05 23:13:23 »
I have a question . How exact can tell something when we have no raw fits , but edited image? How  impact editing picture on this result (excentricity, for example)?

kolec

Offline RickS

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Re: NGC6188 and NGC6144 in 3nm NII
« Reply #8 on: 2015 May 05 23:56:57 »
I have a question . How exact can tell something when we have no raw fits , but edited image? How  impact editing picture on this result (excentricity, for example)?

I don't believe the data has been edited, just calibrated, aligned and stacked.  The eccentricity calculation still gives an indication of how much the star shapes vary from perfectly circular.  The FWHM calculation will be based on pixels since image scale isn't known but in this case it's the variation that's more interesting than the absolute size.

Cheers,
Rick.

Offline kolec

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Re: NGC6188 and NGC6144 in 3nm NII
« Reply #9 on: 2015 May 06 01:02:46 »
OK.

But when you stack together  data before and after flip   ?
When you stack data from another days (years) ?

kolec

Offline RickS

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Re: NGC6188 and NGC6144 in 3nm NII
« Reply #10 on: 2015 May 06 01:41:37 »
OK.

But when you stack together  data before and after flip   ?
When you stack data from another days (years) ?

I agree that checking the raw subs is definitely a better approach if you are trying to diagnose a problem.  However, if there is a problem with an integrated stack then that still tells you that things aren't right.

Cheers,
Rick.

Offline avandonk

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Re: NGC6188 and NGC6144 in 3nm NII
« Reply #11 on: 2015 May 06 16:47:16 »
Here are three 32 bit subs start middle and end of run. Only corrected for darks and flats. Image scale is 3.08" per pixel. 165MB

http://d1355990.i49.quadrahosting.com.au/2015_05/three.zip

Bert
« Last Edit: 2015 May 06 21:12:36 by avandonk »

Offline avandonk

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Re: NGC6188 and NGC6144 in 3nm NII
« Reply #12 on: 2015 May 18 01:31:10 »
OK.

But when you stack together  data before and after flip   ?
When you stack data from another days (years) ?

I agree that checking the raw subs is definitely a better approach if you are trying to diagnose a problem.  However, if there is a problem with an integrated stack then that still tells you that things aren't right.

Cheers,
Rick.


Have not seen your version of the data yet Rick or anybody else's. I just seem to get the noise of armchair experts. If you cannot show me how to do better,  just  then all of you shut f---k up with your puerile fantasies. Bert.

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« Last Edit: 2015 May 18 08:38:45 by Carlos Milovic »

Offline RickS

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Re: NGC6188 and NGC6144 in 3nm NII
« Reply #13 on: 2015 May 18 02:23:16 »
Have not seen your version of the data yet Rick or anybody else's. I just seem to get the noise of armchair experts. If you cannot show me how to do better,  just  then all of you shut f---k up with your puerile fantasies. Bert.

Bert,

This "armchair expert" has processed a fair few images in PixInsight.  Some of them are here: http://www.astrobin.com/users/RickS/  I don't claim to be an expert but I think I'm now a competent intermediate imager.

It requires a significant amount of time & effort to do justice to good data.  I downloaded yours, took a close look at it and decided that the cost/benefit tradeoff wasn't sufficient.  I probably would have decided the same if I'd captured the data myself.  It's not particularly deep or detailed and you clearly still have problems with imaging train.

I mean this as constructive criticism but I know you probably won't take it that way.  Have a nice day  :)

Cheers,
Rick.