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Messages - Ken Pendlebury

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Gallery / Re: NGC7023 Cooperation Dr. Franz Gruber and Oldwexi
« on: 2011 September 08 20:19:17 »
That is stunning.  Nice work!

Gallery / Re: M16 with HD 11
« on: 2011 September 08 20:18:02 »
Nice job Sander.  Beautiful detail in the  shadows...


Gallery / Elephant's Trunk - HST Palette
« on: 2011 September 02 22:11:05 »
Hi folks,

Below is my attempt at the Elephant's Trunk Nebula in HST Narrowband. I had great difficulty getting this image into shape... more than any other I have done. Most of my troubles originated from the weak OIII and SII signals when compared with the very strong Ha signal. When creating a LRGB composite from these signals, the HST palette creates a "very" green image.  The first set of color corrections I made used Photoshop's "Selective color" tool to tame the greens (certainly effective), but the version posted here used the PI curves module (hue) as Niall details here:

Comments and criticism welcome.

Large Size:

Original Size:

Equipment and Exposure Details:


General / Re: Help with Bias
« on: 2011 September 02 09:02:32 »
Tasos and Juan,

Thanks so much for your help.  I feel a bit silly that I was unable to find these threads myself.

While I understand what the issue is, I have one more question about the flats I take in AA5.  As I understand it, AA5 will use 16 bit signed to save bias frames and 16 bit unsigned to save longer frames (darks, lights etc..).  My flat frames are about 6 seconds in length and in AA5 and Nebulosity show a mean of ~25K ADU. 

Making the assumptions outlined above (that this image is also 16 bit signed), I checked the box to enable "Signed integer images store physical data".  Opening this frame with this option on or off yields an image with a mean of ~63K.  I am almost certain this is user error, but I am not exactly sure what I am doing wrong.  Any thoughts on this?

I should also note that, checking this box and opening a bias frame works much better.  One slight difference is that the mean, as indicated by Nebulosity and AA5 is 914 ADU.  When PI opens it, the image shows a mean on ~1800 ADU.  This is probably not significant enough to affect a light image during calibration, but I though I would point it out...

To test this, I opened an AA5 bias frame without the "Signed integer images store physical data" checked and verified the  mean ADU was around 33k.  Using the RGB/K: $T-0.5, the image is manipulated such that the mean ADU is the expected 900.  Nor sure why checking the "Signed integer images store physical data" doubled the mean ADU in this case.


General / Re: Help with Bias
« on: 2011 September 02 05:47:12 »
Thanks Sander.  I will check the hints out and post info if I need to...

There seems to be some inconsistency with this issue...

When I open a "light" frame taken with Astroart in PI, it opens just fine, appears normal and reports all of the correct image statistics.  The error in opening seems to occur with 100% frequency when I am inspecting bias or flats (which baffles me since flats are actually lights).


General / Help with Bias
« on: 2011 September 01 20:38:12 »
Hi folks,

I am hoping somebody might be able to help me understand some image behavior that has baffled me...

I am attempting to take bias frames for my camera.  I have gathered the 16-bit frames with the Astroart application and inspected them.  All frames are at an acceptable level (below 1000 ADU).  To verify, I open the same frame in the Nebulosity capture application and it verifies that the images is below 1000 ADU.  When I open this very same image in PI, it shows a mean ADU of 33682!

Obviously integrating these frames as PI sees them creates a terrible bias frame. 

Strangely, when I use Nebulosity to capture the bias frames, PI does indicate that the ADU value is less than 1000.  Astroart uses an ASCOM driver for capture (QHY9 Camera) while Nebulosity uses a native driver.  I'm not sure if this is relevant at all, but though I would mention it.

Any thoughts are appreciated


Gallery / Re: Eastern Veil Bi-Color
« on: 2011 August 15 18:39:56 »
Thanks Gerhard.  I will give that a shot.  Do you have any examples to show with this method?

Gallery / Eastern Veil Bi-Color
« on: 2011 August 07 16:54:48 »
Hi folks,

This is my attempt at a bi-color (Ha & OIII) version of the eastern veil.  Equipment and exposure details can be found by following the link below.

Here is a summary of the processing approach:
  • Stretch Ha and OIII separately to ensure equal contribution to total signal strength
  • Map Ha to Red and OIII to Blue
  • Create false green channel using Pixel math.  Lots of experimentation here, final was (0.45*Ha + 0.55*OIII)
  • Use hue adjustment to fine-tune colors to liking
  • Neutralize background to remove excessive reds (mask over nebula)
  • Perform HDR Wavelets to enhance tendrils
  • Erode stars to minimize noise (Morph module w/ 7 iterations)
  • ACDNR to cleanup some noise

Please let me know if you have suggestions for improvement.  I'm here to learn and this is my first narrowband attempt.

Full Size:

Exposure Details:

Thanks for looking,

Gallery / Melotte 15 (Heart Nebula)
« on: 2010 December 17 14:11:41 »
Hi folks,

I thought I would post my first real try at an emission nebula using some variation of an HaRGB combination technique.  In the spirit of Jack's post, I am hoping this might be a learning experience for me (and others).

I thought the detail turned out well (especially considering the suburban location), but I am not thrilled with the color balance.  Without reciting the entire processing methodology I used, I wanted to layout what I suspect are possible culprits:

1.) I only captured 60 minutes of 5min 2x2 RGB (each) from a suburban location.  I think that the signal might be a bit too weak to obtain proper balancing of colors.
2.) The LRGB method I used is likely suspect:  First I processed the Lum(Ha) to my liking.  Next I used the LRGB module (without L checked) to combine the linear RGB stacks.  This was followed by background neutralization, DBE, color calibration (no structure detection) and finally by MTF.  I had difficulty with BN and CC because the emission nebula covers the entirety of the frame (I was unable to provide a viable reference background).  As such I chose the entire image as the reference (probably a bad idea).

At this point I have a RGB composite that looks very weak.  Using the LRGB combine tool, I add the Ha as Luminance and this turns a very nicely colored image (albeit weak) into a red-pink monstrosity.  I have not yet tried Vincent's methodology ( because I am unsure if capturing RGB at 2x2 will scale well.

Any suggestions are welcome...


General / Re: Heart Nebula Advice
« on: 2010 December 08 07:23:11 »
Thanks Philip!  I will give this a try.

General / Heart Nebula Advice
« on: 2010 December 06 21:48:58 »
Hi folks,

I have a couple of questions about processing nebulae (like the heart nebula).  First a bit of data...  I took ~3 hrs of Ha (1x1) data with 1 hr each of RGB (2x2) with intent to use Ha as the luminance channel.

My general approach was to take and process the RGB data and ensure that it has the desired color.  It is a bit difficult to use tools like color balance because nebulous gas covers the entirety of the frame.  This scenario does not allow for the use of a background reference and, as such, the entire frame yields background stars that are a bit too "orange-red".

So... my first question is:

1.) How does one go about balancing colors where there is no "empty" (non-dso) background to reference?

Next, I think I have a fundamental misunderstanding about the Lum channel.  When I arrived on an RGB frame that was ok and had the right shade of red (except as described above), I went to register and combine this with my Ha data.  Using the LRGB combine module, I select the Ha as "L" and apply this to the registered RGB data.  The resultant image has changed the deep red color created in the RGB to a pale salmon color.  I know that combining the Ha with the Red channel can sometimes crate this color, but I didn't know that the Lum channel could change color this drastically.  I think that Juan may have explained to me how this can happen, but it was probably above my head...

2.) So... is there a better way to use Ha data as the Lum and retain color?  Perhaps I am going about this the wrong way entirely.

Thanks for any help,


Gallery / M33, ET and the Flaming Star
« on: 2010 November 12 16:10:33 »
Hi folks,

The links below point to data I captured at the Eldorado Star Party in Texas.  Three beautiful nights of clear crisp skies allowed for a good deal of exposure time.  M33 might be a little over-processed.  This is likely a matter of taste, but I had to darken the background a bit more than I like because applying ACDNR to an over-stretched background lends itself to a "mottled" look of which I am not too fond.  The ET cluster is nice, but can probably use a bit more saturation in the stars.  The flaming star I found a bit hard to frame.  As a result I ended up cutting some of the most interesting parts out...  oh well.

Comments and criticism welcome.  I am always looking to refine my techniques.


ET Cluster:

Flaming Star:


Gallery / Re: M31 with Ha and RGB (No Lum)
« on: 2010 October 14 13:30:53 »
Thanks Jack.  I think the next project will use LRGB only because I usually don't have 7 hours to devote to a single target (not because I don't believe RGB can achieve decent results).

Gallery / Re: M31 with Ha and RGB (No Lum)
« on: 2010 October 13 09:16:35 »
Thanks Max.

I believe that this image contains a comparable amount of depth to similar images that used a luminance filter.  That being said, I am far from a veteran imager...

Gallery / M31 with Ha and RGB (No Lum)
« on: 2010 October 13 08:39:08 »
Hi Folks,

Following some advice from Juan, I decided to see what this whole "No Lum" thing was all about.  Since I had time to capture over 7 hours of RGB from a dark sky, I felt that was sufficient to overcome the need for luminance frames.  After this, I was able to add in a couple hours of Ha in order to emphasize the faint HII knots on the outer arms.

Here is the result:

Wide field:


Exposure and Equipment Details:


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