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Messages - dayers

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Gallery / Re: Yet Another Andromeda
« on: 2015 September 13 16:38:22 »
On a scale of 0 (black) to 1 (white), black clipping means the black level is zero. An area of sky with level zero cannot show any detail. I like to set my sky at to about 1 on the 0-1 scale, which still looks "black" but will show faint objects like distant galaxies and dim stars and such. On many objects a background sky setting of 1.5 to 2.0  shows the sky as dark gray and looks good.

Your background between stars looks to be around .5 as a guess. Looks good and I don't suggest changing anything, but as an experiment you might lighten the background toward dark gray (larger number), and see if you think it is an improvement.

I am answering your question poorly, but I hope you get my drift. Again, I certainly like your image as is.


Gallery / Re: Yet Another Andromeda
« on: 2015 September 12 08:45:29 »
Hi Shane,

This is one of the best M31's I've seen. You should be very proud of it. It spurs me to finally learn to drizzel. I downloaded your large image and poked around in it. Your stars are perfect! At first I thought you had some black clipping, but a close examination shows no clipping and a lot of distant objects. My only comment is that raising the black level a little might improve the overall image, at least as I viewed it. Or it might not.

I hope to image M31 from my LPd back patio next month. I am housebound so I do what I can from a Bortle 5-6 zone. I will use your image as my gold standard, but I can't hope to come very close.

Thanks for sharing,


Gallery / Re: Hundreds of Galaxies - M51
« on: 2015 July 06 05:32:30 »
Hi Jim,

I can readily see why you like this image of M51. It's one of the best I have seen. OK to pat self on back. Did you follow your cribsheet workflow?  :tongue:

Gallery / Re: M101 Pinwheel Galaxy RGB
« on: 2015 February 18 14:48:04 »

Can you tell me a bit more about the use of range masks? There is no RangeMask tool that I can find, so a range mask must come from the use of other tools. Can you straighten me out?


Gallery / Re: M101 Pinwheel Galaxy RGB
« on: 2015 February 18 14:04:20 »
Hey thanks Mike! I guess there can be life after ghastly. I plan on revisiting my data some day to try to coax a little more out of it.


Gallery / M101 Pinwheel Galaxy RGB
« on: 2015 February 18 12:06:33 »
RGB data for this image was acquired remotely using iTelescope T11 at Mayhill, NM. 15 5-minute exposures each for R, G, and B. I also took a lot of Ha, but the max 10 minute exposures were not enough to provide a usable amount of Ha, so I had to settle for RGB. Tried LRGB, but the RGB looked better.

Processed 100% in PI. Tools used were primarily ChannelCombination, DynamicCrop, DynamicBackgroundExtraction, BackgroundNeutralization, SCNR, ColorCorrection, CurvesTransformation, MaskedStretch, and TGVDenoise.

Question for you all: On objects like M101 with not all that much color, is there a way to get a bit more color saturation without it looking ghastly? My tentative conclusion is that this image had gobs of color information, but is essentially a "white" object with the R, G, and B pretty much equal. I'd be interested in your take on the situation.

I was pleased overall, especially the nice starfield.


Gallery / Re: NGC 281 HaRGB
« on: 2015 January 03 16:42:47 »
Thanks, Zocky.

Rick, thanks for your comment. Like you say, it's a matter of personal taste, and I tend toward understated colors. I am presently collecting exposures for an RGB starfield to some day replace the Ha stars (I substituted Ha for Luminance in the RGB).

Thanks to all for nudging me up the learning curve. I may get the hang of this stuff yet. Fun, fun, fun! And I had better hurry, because my next birthday will be my 84th.


Gallery / Re: NGC 281 HaRGB
« on: 2015 January 03 14:46:35 »
Rick, here is the result of messing around with ColorSaturation and CurvesTransformation. I used CS to knock back the blue halow and tame the red stars, curves to brighten as you suggested.

I plan to harvest some RGB stars soon and substitute for the present Ha stars. I'll let it rest here for now and keep my ear tuned to your (and others) suggestions.

Thanks again for your interest.


Thanks, bitli, that is very helpful information. I will check out the telescope I use a lot, T-11 at New Mexico. You confirmed my conclusion that usually using supplied calibrated frames is the best (and easiest) way to go.

Is it safe to mix east-side and west-side frames and let StarAlignment and ImageIntegration sort it out? It seems like I have done this in the past and didn't have problems.


Gallery / Re: NGC 281 HaRGB
« on: 2014 December 29 16:56:07 »
Thanks again, Rick, especially the one for ColorSaturation. I didn't realize you could select a narrow chunk of spectrum like that.


Gallery / Re: NGC 281 HaRGB
« on: 2014 December 29 06:39:12 »
Don't mind at all, Rick. I appreciate the time you took to "fix" my image. I will go back and see if I can do some fixin' myself. I'm not too sure I understand what you did. The ColorSaturation tool is one that I have not had much success with so far, but you encourage me to go back and take another whack. Stay tuned.


Gallery / Re: NGC 281 HaRGB
« on: 2014 December 28 08:57:59 »

The blue halos around bright stars just seem to follow me wherever I go! I haven't found a good way to reduce them. Maybe someone else can help me out here. Could it be the result of substituting an Ha image for the luminance in LRGBCombination? It seemed to do a good job of taming the stars so they would not dominate the image.

The blue portion of the nebula is, I believe, not related to the star halo problem. Many pics of the Pacman have this blue area, and I'm pretty sure that it is "normal" color. Personally, I like it, as well as the brown color of the lower part of the nebula.

Thanks for your comments.


Gallery / NGC 281 HaRGB
« on: 2014 December 26 08:21:00 »
Another rendition of NGC 281: 7.5 hrs total integration. Data acquired with iTelescope T-11 (20") over several days in mid December, 2014.

Thanks for looking.


General / Re: Integration using FWHM weights?
« on: 2014 December 25 06:03:44 »
Georg, how might WEIGHT = 1/FWHM compare with just using SNRWeight?


General / Re: Suggested workflow for spectroscopy please?
« on: 2014 December 21 17:42:35 »
Hi Steve,

I've followed you over to the General section. I am starting to educate myself on the subject. I assume that someone will move the initial replies to General also.

It appears that the Star Analyzer and the ISIS software are the essential pieces, and the Star Analyzer is mounted in the optical path at the CCD or camera focal point. Is that right? If I understand your question, you are wondering how PI can be used to get the most information out of the image.

I may be getting ahead of myself, but can spectroscopy be used to measure red-shift?


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