Feedback on M45 Pleiades - Forums

Topic starter

Feb 28, 2023

I would like to ask your opinion and feedback for my take on the pleiades. I had some issues adjusting the reducer, basically never got it to work perfectly, so egg stars it is. What would you do differently on the image? Thank you for some honest feedback

https://astrob.in/mrhjep/0/

Tobias

Pete Bouras

Feb 28, 2023 · Edited: Feb 28, 2023

Tobias,

Nice image.

I would try a different type of stretch like Generalized Hyperbolic Stretch, which can better resolve the bright stars, they look blown out now.

Also, the blue areas in the lower part of the Pleiades seem weak for some reason, and the color in the nebula seems a bit green and not enough saturation (although this is probably a taste thing). Probably a lot of folks boost the blue in the nebula a little using masks.

Try using SPCC to get a good baseline on the color.

Lastly, use noise reduction, NoiseXterminator works very well, as does EZDenoise, and even Topaz Denoise AI (if used properly).

Not that my image is spectacular, but you can see what I'm talking about:
https://www.astrobin.com/w5qspe/C/

Hope this helps,

-Pete

Helpful Respectful Engaging Supportive

Nick Large

Feb 28, 2023

Hi Tobias,

This is a great image already, the nebula color and star color are nice and beside the star shape you mention, which is not very pronounced either, the star size is good.
The two major things I would personally do would be:
1- some slight noise reduction. You got some apparent noise in the dark areas.
2- it could be my screen, but it seems that you have some red tint in your dark background so I would play on the red curve to correct that.

Not sure how you process the stars and nebula, separately or together, but if you can process them separately and dial down on the stretch of the stars that would keep the larger stars from bloating too much. In PI there are different blending formulas you can use that can help you achieve smaller stars and have a natural/smooth blending.

If you're interested, this is my most recent version of M45

Nick

Helpful Engaging Supportive

John Favalessa

Feb 28, 2023 · Edited: Feb 28, 2023

You are getting there as this is a good image. BWT I have the same 102gt, reducer and camera. they are a great match but I don't understand how your pixel scale is 2.296 arcs/pixel (slightly under sampled). with this setup you should be slightly over 1arcs/pixel which is optimal. I see the biggest issue is your backspacing resulting in the weird corner stars (see pic). I grabbed your image with a screenshot on my mac. I used PI/scripts/image analysis/Aberrationinspector to generate. I also used ASTAP to do an analysis (see pic). Seems your camera is too close. what is your mm adjustment on the reducer? adjusting the backspace usually helps the tilt, but you may need to adjust tilt separately after backspace. when you dial that in good enough I'd highly recommend spending the money for BluxTerminator. Use its correct only setting to run deconvolution on the stars which will improve any egg shaped stars. also get NoiseXterminator. -john

Helpful

TobsHD

Topic starter

Feb 28, 2023

Pete Bouras:
Tobias,

Nice image.

I would try a different type of stretch like Generalized Hyperbolic Stretch, which can better resolve the bright stars, they look blown out now.

Also, the blue areas in the lower part of the Pleiades seem weak for some reason, and the color in the nebula seems a bit green and not enough saturation (although this is probably a taste thing). Probably a lot of folks boost the blue in the nebula a little using masks.

Try using SPCC to get a good baseline on the color.

Lastly, use noise reduction, NoiseXterminator works very well, as does EZDenoise, and even Topaz Denoise AI (if used properly).

Not that my image is spectacular, but you can see what I'm talking about:
https://www.astrobin.com/w5qspe/C/

Hope this helps,

-Pete

Dear Pete,

thanks a lot for your comments. I was using 3 types of stretch in parallel to see which version comes out best. Manual stretch, EZ soft stretch and masked stretch. But i guess i need to play with Generalized Hyperbolic Stretch as it was recommend quite often. The weak blue was somewhat of a choice as i tried not to oversaturate and keep M45 nicely transitioned with the surrounding nebulae. As per noise reduction i am using the manual jon rista approach which is basically EZ Denoise. But maybe overall i was too shy with color saturation and denoising.

thanks again Tobias

Helpful Respectful Concise

TobsHD

Topic starter

Feb 28, 2023

Nick Large:
Hi Tobias,

This is a great image already, the nebula color and star color are nice and beside the star shape you mention, which is not very pronounced either, the star size is good.
The two major things I would personally do would be:
1- some slight noise reduction. You got some apparent noise in the dark areas.
2- it could be my screen, but it seems that you have some red tint in your dark background so I would play on the red curve to correct that.

Not sure how you process the stars and nebula, separately or together, but if you can process them separately and dial down on the stretch of the stars that would keep the larger stars from bloating too much. In PI there are different blending formulas you can use that can help you achieve smaller stars and have a natural/smooth blending.

If you're interested, this is my most recent version of M45

Nick

Dear Nick

thank you for your feedback. Now i can also see some red in the background. I always struggle with seeing these subtle things when you spent countless hours working on an image. Its is hard to be able to get fresh eyes, even when some time has passed. As per denoising, i agree the background could use a little more.

awesome feedback Nick

thx Tobias

TobsHD

Topic starter

Feb 28, 2023

John Favalessa:
You are getting there as this is a good image. BWT I have the same 102gt, reducer and camera. they are a great match but I don't understand how your pixel scale is 2.296 arcs/pixel (slightly under sampled). with this setup you should be slightly over 1arcs/pixel which is optimal. I see the biggest issue is your backspacing resulting in the weird corner stars (see pic). I grabbed your image with a screenshot on my mac. I used PI/scripts/image analysis/Aberrationinspector to generate. I also used ASTAP to do an analysis (see pic). Seems your camera is too close. what is your mm adjustment on the reducer? adjusting the backspace usually helps the tilt, but you may need to adjust tilt separately after backspace. when you dial that in good enough I'd highly recommend spending the money for BluxTerminator. Use its correct only setting to run deconvolution on the stars which will improve any egg shaped stars. also get NoiseXterminator. -john

John, wow thanks for the deep analysis in terms of sensor distance. I spent several nights adjusting the reducer and sensor distance however it never seemed to work. I either was too close or too far away from the sensor although i used to distance settings provided by WO. The adjustment ring is wobbly on my reducer with quite some play in the thread. Maybe that is the issue. But still, it shouldnt be so off, as you showed, the corner stars are quite ugly. I also have the flattener without reducer and there is no tilt. So it must be the reducer. I used the recommended 15.6 mm on the reducer and a backfocus of 70.6 mm. During adjusting i plates with backfocus and the reducer distance. How the pixel scale came to be i am not sure. The image was drizzled in processing it should be slightly over 1 arcs/ pixel.

all of you again thanks a bunch. Now i have new approaches to try out.

clear skies

Tobias

John Favalessa

Feb 28, 2023

those are the correct distances for the 102gt and the WO reducer. Your filter is 1mm thick so that means you should add 0.33 to the backspace. The wobble is the big concern. that shouldn't have play, should be locked down with no flex. I'm sure that's adding the tilt. I'd contact who you bought it from for advice/repair/replacement. -john

Helpful Concise