Date
1 - 10 of 10
Dark Nebula in Aquila ... and a few stars
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Was able to get out under the stars last night in the San Diego County Desert. 100 degree days but the temperature slowly got down to a comfortable 65 F or so just before dawn. This time of year you have to hurry and pack up before the sun comes up over the mountains. :-)
This one is an unguided image taken with the Mach2 and my FSQ-106 + the 0.72 645 reducer for a focal length of ~381 mm. The camera was the full frame ZWO ASI2400MC Pro. 89 x 180 second unguided exposures. https://astrob.in/full/ejtna2/0/ This is a work in progress. -- Dean Jacobsen Astrobin Image Gallery - https://www.astrobin.com/users/deanjacobsen/
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The "quite a bit less red" version.
https://astrob.in/full/ejtna2/B/ Still no colors in the stars other than red and white though. Will have to figure that one out. Edit: Another revision, hopefully less garish than the last two versions. This particular field has been more challenging than usual: https://astrob.in/full/ejtna2/C/ -- Dean Jacobsen Astrobin Image Gallery - https://www.astrobin.com/users/deanjacobsen/
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Roland Christen
If you combine a lot of images and then convert the stack to color, all the stars will become color-less. You have to first de-Bayer them to produce a color image of each individual frame before stacking them. MaximDL has this feature and can do the stacking of hundreds of images in the background without running into memory limitations. The result is a final group stack that has lots of colorful stars.
I don't know how other programs do it, but I've always relied on MaximDL to do it right.
Rolando
-----Original Message-----
From: Dean Jacobsen <deanjacobsen@...> To: main@ap-gto.groups.io Sent: Sun, Jun 26, 2022 6:56 pm Subject: Re: [ap-gto] Dark Nebula in Aquila ... and a few stars [Edited Message Follows]
The "quite a bit less red" version.https://astrob.in/full/ejtna2/B/ Still no colors in the stars other than red and white though. Will have to figure that one out. Edit: Another revision, hopefully less garish than the last two versions. This particular field has been more challenging than usual: https://astrob.in/full/ejtna2/C/ -- Roland Christen Astro-Physics
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Dean it's a beautiful target and starfield How are you processing these? in my experience with PixInsight i always need to color calibrate and then boost saturation to taste Generally the colors are pretty muted coming out of the camera
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Brian Brian Valente astro portfolio https://www.brianvalentephotography.com/astrophotography/ portfolio brianvalentephotography.com
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Hi Roland and Brian, thanks for the tips and comments.
I calibrate, stack and do basic stretching in PixInsight. The procedure I follow is for color cameras is: - calibrate - debayer - align - image integration -> stack I have been using my ASI2600MC color camera for two years now and had settled on my standard exposure times based on the focal length. The exposure times were metered based on keeping the stars in the field from becoming over-saturated. Generally I have been successful in avoiding over exposing the stars and thus preserving star color with the ASI2600MC. Here is an example of what I generally see: https://astrob.in/full/w013xz/D/ This last image was with a new color camera - the ASI2400MC - and I thought that I should be good with the exposure times that worked with the ASI2600MC... such as 180 seconds. Well, I just spent some time going over my unstacked subs and, as it turns out, almost every star, even the small field stars, were saturated/overexposed... at 180 seconds. So, I guess my next move is to notch down the exposure time to 120 seconds and see how things go. Seeing saturated field stars at 180 seconds with the ASI2400MC is sort of a surprise but the pixels are 60% bigger than the ASI2600MC. -- Dean Jacobsen Astrobin Image Gallery - https://www.astrobin.com/users/deanjacobsen/
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On 6/27/2022 1:01 PM, Dean Jacobsen wrote:
Hi Roland and Brian, thanks for the tips and comments.FWIW, I add a couple of steps: After Calibrate, Cosmetic Correction sometimes can help, but I don't use it on NB subs. After Debayer, I use Subframe Selector (now an official PI process, not a script) to identify the best subframes to use for star alignment (sorted FHWM ascending) and for image integration (sorted SNR Weight descending). --- Mike
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Hi Dean >>>Well, I just spent some time going over my unstacked subs and, as it turns out, almost every star, even the small field stars, were saturated/overexposed... at 180 seconds. I'm not sure how you determined this, but i regularly do 10 min exposures with a 6200mc on the SVX80 scope with reducer, so I think it's around f5.25. Here's a example similar to yours I generally find stretching the image to non-linear to be the real key to all this, it's definitely an art form. Generalized Hyperbolic Stretch has become a great "control panel" for managing stretches in both lum and color. TAIC just did a guest speaking slot on this
On Mon, Jun 27, 2022 at 10:01 AM Dean Jacobsen <deanjacobsen@...> wrote: Hi Roland and Brian, thanks for the tips and comments. --
Brian Brian Valente astro portfolio https://www.brianvalentephotography.com/astrophotography/ portfolio brianvalentephotography.com
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What a star-dense area, Dean! Nicely done. Karen AP
From: main@ap-gto.groups.io <main@ap-gto.groups.io>
On Behalf Of Dean Jacobsen
Sent: Sunday, June 26, 2022 6:57 PM To: main@ap-gto.groups.io Subject: Re: [ap-gto] Dark Nebula in Aquila ... and a few stars
[Edited Message Follows] The "quite a bit less red" version. -- Karen Christen Astro-Physics
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Joseph Beyer
Hi Dean,
Joe
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Joseph Beyer
Sheesh, I should read my own notes, I makes notes to remember and then forget to read them… The initial stretch was done using ArcSinH just bring up colors followed by Histogram Transformation. Glad I wrote down the processing method somewhere!
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