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#1 venyix

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Posted 18 October 2020 - 12:08 AM

I really feel kind of lost towards the end of image processing. I end up getting images that I'm not entirely happy with. Am I just nitpicking? I feel like there is too much noise, stars aren't very sharp, clipping black levels, etc. Granted I've only been doing AP for about 5 months or so, but I'd appreciate some honest impressions on this image. 

 

What do you think about the stars? (roundness/trails)

The image overall?

Ways that I can improve this image?

 

Edit: This is Ha, SII, OIII narrowband images

139 5 minute subs, ~11.5 hours exposure

 

Fullsize https://drive.google...iew?usp=sharing

 

Image04.jpg


Edited by venyix, 18 October 2020 - 12:14 AM.


#2 m1618

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Posted 18 October 2020 - 12:42 AM

Comparing the left side and right side, looks like the star shapes change. Could it possibly be the image train being heavy to one side?
For me, I had a similar experience with having thumbscrews too tight on one side and my focuser having too much play.



#3 imtl

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Posted 18 October 2020 - 12:43 AM

Hi Phillip,

 

Well there are several things going on here. I think before you worry about processing you might want to take a closer look at your mount's tracking. You're star trails are quite big in the full size image. I think you have several things going on: PA is not great and you got some probably differential flexure. Since you're doing few minutes subs with these 3nm narrow band filters, it will show.

 

Regarding processing, well, you have quite a bit of chromatic noise and star burn. Which is because you were pushing your stretching too much probably. Did you work with masks?

 

I think its not a bad image as a beginner. There is always room for improvement. Don't be discouraged. So, from here I would try and work on getting the guiding and mount to produce better lights. And for now, use the data that you have to better your processing skills. There are many tutorials to help you get a better final image. 

 

There is a sticky link here on CN with PI workflows by very experienced and good imager that might help you get going:

link

 

Try and produce a clean final image first with working with masks

Keep going at it! You'll get better!


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#4 venyix

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Posted 18 October 2020 - 01:03 AM

Comparing the left side and right side, looks like the star shapes change. Could it possibly be the image train being heavy to one side?
For me, I had a similar experience with having thumbscrews too tight on one side and my focuser having too much play.

Interesting idea, it never occurred to me that the thumb screws might be too tight and thus favor one side. I know when I tighten it down that one thumbscrew is generally tighter than the other two when attaching the imaging train. I'll adjust these and see if that ends up helping. Thanks for the idea!

 

Hi Phillip,

 

Well there are several things going on here. I think before you worry about processing you might want to take a closer look at your mount's tracking. You're star trails are quite big in the full size image. I think you have several things going on: PA is not great and you got some probably differential flexure. Since you're doing few minutes subs with these 3nm narrow band filters, it will show.

 

Regarding processing, well, you have quite a bit of chromatic noise and star burn. Which is because you were pushing your stretching too much probably. Did you work with masks?

 

I think its not a bad image as a beginner. There is always room for improvement. Don't be discouraged. So, from here I would try and work on getting the guiding and mount to produce better lights. And for now, use the data that you have to better your processing skills. There are many tutorials to help you get a better final image. 

 

There is a sticky link here on CN with PI workflows by very experienced and good imager that might help you get going:

link

 

Try and produce a clean final image first with working with masks

Keep going at it! You'll get better!

I'll admit that I HATE the polar alignment scope on the EQ6-R Pro. The main issue I have with it is that to orient it with 0 at the top, you have to rotate the mount to a certain angle, but it's done by eye so it's possible to be off slightly. I'm going to look into getting a Polemaster(I think that's what it's called), and hopefully that'll help.

Secondly, I do work with masks, and I don't think I pushed the stretch too far, but I may have pushed the post processing in PhotoShop too far, I'll upload a copy of the original straight from PixInsight. 


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#5 venyix

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Posted 18 October 2020 - 01:11 AM

Hi Phillip,

 

Well there are several things going on here. I think before you worry about processing you might want to take a closer look at your mount's tracking. You're star trails are quite big in the full size image. I think you have several things going on: PA is not great and you got some probably differential flexure. Since you're doing few minutes subs with these 3nm narrow band filters, it will show.

 

Regarding processing, well, you have quite a bit of chromatic noise and star burn. Which is because you were pushing your stretching too much probably. Did you work with masks?

 

I think its not a bad image as a beginner. There is always room for improvement. Don't be discouraged. So, from here I would try and work on getting the guiding and mount to produce better lights. And for now, use the data that you have to better your processing skills. There are many tutorials to help you get a better final image. 

 

There is a sticky link here on CN with PI workflows by very experienced and good imager that might help you get going:

link

 

Try and produce a clean final image first with working with masks

Keep going at it! You'll get better!

FullSize Image before PS

https://drive.google...iew?usp=sharing

 

This is a raw Ha 5 minute sub that my camera literally just took. Monoceros 

https://drive.google...iew?usp=sharing



#6 imtl

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Posted 18 October 2020 - 01:12 AM

Interesting idea, it never occurred to me that the thumb screws might be too tight and thus favor one side. I know when I tighten it down that one thumbscrew is generally tighter than the other two when attaching the imaging train. I'll adjust these and see if that ends up helping. Thanks for the idea!

 

I'll admit that I HATE the polar alignment scope on the EQ6-R Pro. The main issue I have with it is that to orient it with 0 at the top, you have to rotate the mount to a certain angle, but it's done by eye so it's possible to be off slightly. I'm going to look into getting a Polemaster(I think that's what it's called), and hopefully that'll help.

Secondly, I do work with masks, and I don't think I pushed the stretch too far, but I may have pushed the post processing in PhotoShop too far, I'll upload a copy of the original straight from PixInsight. 

You can use sharpcap for PA.

 

Well, your stars are blown out and you have a lot of chromatic damage around them so something in your post processing is not great. So, maybe try and look at different stages of your post processing and identify what is the stage that this is happening the most.



#7 imtl

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Posted 18 October 2020 - 01:14 AM

Are you using any sort of field flattener with this scope?

 

From your single Ha sub it is clear where the aberrations are coming from in the final image since Ha is probably very dominant compared to OIII and SII. The fact that some stars have a bit of a different shape in the final image vs. the single Ha sub could be because of meridian flip or just other tracking issues with some of the subs.

 

Anyways, from your single sub it shows several things. First, your focus is off. Second, you have either and field curvature in place, or in case you did use a field flattener then your spacing is off. You need to reduce spacing. So, which one is it?

 

It look like either, field curvature + bad PA + soft focus, or FF spacing is off + PA + focus.

 

But it might have other issues as well. I'm doing a guessing game here based on this single sub.

 

My advice to you is to go one step at a time. Get your PA in order first! Then get your focus tight. Take a sub. See what you get.


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#8 venyix

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Posted 18 October 2020 - 01:42 AM

This is zoomed in on the Ha sub, and the kind of weird stars that I end up getting. I use a bahtinov mask for focusing, but maybe it fell out of focus somehow. I am using a field flattener, but I've been experimenting with it as you can see in this other thread... https://www.cloudyni...ack-focus-help/
ghost stars


#9 venyix

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Posted 18 October 2020 - 01:47 AM

Are you using any sort of field flattener with this scope?

 

From your single Ha sub it is clear where the aberrations are coming from in the final image since Ha is probably very dominant compared to OIII and SII. The fact that some stars have a bit of a different shape in the final image vs. the single Ha sub could be because of meridian flip or just other tracking issues with some of the subs.

 

Anyways, from your single sub it shows several things. First, your focus is off. Second, you have either and field curvature in place, or in case you did use a field flattener then your spacing is off. You need to reduce spacing. So, which one is it?

 

It look like either, field curvature + bad PA + soft focus, or FF spacing is off + PA + focus.

 

But it might have other issues as well. I'm doing a guessing game here based on this single sub.

 

My advice to you is to go one step at a time. Get your PA in order first! Then get your focus tight. Take a sub. See what you get.

Here is a 5 min sub without the flattener, seems like I still have the star ghosting issue.

https://drive.google...iew?usp=sharing


Edited by venyix, 18 October 2020 - 01:47 AM.


#10 bjulihn

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Posted 18 October 2020 - 01:52 AM

I think you are doing quite well for the time you have been doing this. If polar alignment is difficult, I would recommend Sharpcap. The polar alignment tool work well with your guide camera and guide scope. It's accurate and easy.

 

Second, you are expressing concern about noise levels. I highly recommend Jon Rista's website and tutorial on noise reduction. It took my images to a whole new level. Here's the link. Good Luck!

https://jonrista.com...duction-part-1/



#11 imtl

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Posted 18 October 2020 - 01:54 AM

 

This is zoomed in on the Ha sub, and the kind of weird stars that I end up getting. I use a bahtinov mask for focusing, but maybe it fell out of focus somehow. I am using a field flattener, but I've been experimenting with it as you can see in this other thread... https://www.cloudyni...ack-focus-help/

 

Okay then this is important information. You see in your single Ha sub how your star trails are going tangential around the center? That is usually because of too much spacing. Reduce your spacing by 2mm and try again. You might need to experiment with this. BUT,

if you do not do a proper PA and get good focus you might be fooling yourself with what is going on. Focusing with Bahtinov mask is fine but focus does change during the course of the night. I don't know how much time and what was the temperature change between the time you focused till you shot that sub. Anyways, my advice is:

 

Fix a spacing, PA, focus - Take a sub.

Reduce spacing, focus - take another sub.

repeat until you start seeing a change from tangential aberration to radial aberration. That means you crossed from too much spacing to too little spacing.

 

Regarding your image without the FF. Well, I cannot really know what is going on over there because the field is quite distorted. All the above mentioned reasons and beyond.

 

It will be much better if you debug all this things using your L filter or G.



#12 venyix

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Posted 18 October 2020 - 02:05 AM

Okay then this is important information. You see in your single Ha sub how your star trails are going tangential around the center? That is usually because of too much spacing. Reduce your spacing by 2mm and try again. You might need to experiment with this. BUT,

if you do not do a proper PA and get good focus you might be fooling yourself with what is going on. Focusing with Bahtinov mask is fine but focus does change during the course of the night. I don't know how much time and what was the temperature change between the time you focused till you shot that sub. Anyways, my advice is:

 

Fix a spacing, PA, focus - Take a sub.

Reduce spacing, focus - take another sub.

repeat until you start seeing a change from tangential aberration to radial aberration. That means you crossed from too much spacing to too little spacing.

 

Regarding your image without the FF. Well, I cannot really know what is going on over there because the field is quite distorted. All the above mentioned reasons and beyond.

 

It will be much better if you debug all this things using your L filter or G.

Thanks for the note on the spacing, I'll give that a try next imaging session. I went outside and did confirm that I had gone out of focus somewhere along the line. I refocused with the mask and am taking another exposure, will post when it's finished. I also ensured my thumb screws were tightened evenly around the imaging train. (I'm also going to attach via threads probably for next session) I'll give this a try with the L filter, as it will shorten exposure duration, and maybe they will be easier to see? Other reasons why using L would be better?



#13 venyix

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Posted 18 October 2020 - 02:09 AM

Here is the exposure after focusing

https://drive.google...iew?usp=sharing



#14 imtl

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Posted 18 October 2020 - 02:11 AM

Using L will give you fast results and will take out long exposures tracking issues. 

Do 5-10 seconds subs on a rich star field (Milkyway area is good), take short subs and see what you get. If you got any PA errors then the short subs will make PA error effect minor and you can see what else is going on in your system. 



#15 venyix

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Posted 18 October 2020 - 02:14 AM

Here is a 2 minute L sub, I'll upload some shorter ones in just a second...

https://drive.google...iew?usp=sharing



#16 venyix

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Posted 18 October 2020 - 02:14 AM

Here is a 5 second L sub

https://drive.google...iew?usp=sharing



#17 imtl

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Posted 18 October 2020 - 02:15 AM

Here is the exposure after focusing

https://drive.google...iew?usp=sharing

Okay this looks much better. Now you got star trails going in the same direction all across the field.

Take a shorter sub with L and see what you get now.

 

The star trails are tracking errors. Are you guiding? What is your RA rms vs. DEC rms?

I see you use a guide scope, so even if you get good guiding numbers this might be differential flexure.

Take a shorter sub!

 

Its definitely a progress!



#18 venyix

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Posted 18 October 2020 - 02:19 AM

Okay this looks much better. Now you got star trails going in the same direction all across the field.

Take a shorter sub with L and see what you get now.

 

The star trails are tracking errors. Are you guiding? What is your RA rms vs. DEC rms?

I see you use a guide scope, so even if you get good guiding numbers this might be differential flexure.

Take a shorter sub!

 

Its definitely a progress!

For some reason I can't switch PHD off of Pixels to Arcsecond, the option is greyed out. Any idea why?
Capture
 
This is my guide log from tonight as well


#19 imtl

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Posted 18 October 2020 - 02:45 AM

I don't know why its gray. It shouldn't. Try and stop guiding for a sec and see if you can change it to arcsec.

 

In any case, if you are using the guide scope and guide camera from your signature then your guide scale is 7.3"/pixel. That is quite big and I would suggest you think about barlowing your guide camera to get better resolution. Your guide stars are basically 1 pixel. That's not really efficient guiding.

 

Looking at your RA rms vs DEC rms it clearly shows that RA is much bigger than DEC but I don't know what is the time scale of the PHD2 plot you posted. Anyways, your RA rms is 1.45" and DEC rms is 0.3". That will explain the elongation you're getting in your sub.

 

 

So I plate solved your image and the elongation is on the RA axis. So, my comment from above is probably what is happening.



#20 Boeglewatcher

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Posted 18 October 2020 - 03:01 AM

 

For some reason I can't switch PHD off of Pixels to Arcsecond, the option is greyed out. Any idea why?
 
 
This is my guide log from tonight as well

 

Could be that there is no focal length data available. Then, PHD2 can’t calculate the arcsec. Check the focal length setting under Advanced setting - Guiding - Focal length entry should be the focal length of your guiding scope.


Edited by Boeglewatcher, 18 October 2020 - 03:05 AM.

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#21 Hypoxic

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Posted 18 October 2020 - 07:21 AM

You can use sharpcap for PA..

+1

 

Upped my game with my EQ6-R. It was quite entertaining to see how far off my manual alignment was in comparison to aligning with Sharpcap.



#22 TelescopeGreg

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Posted 18 October 2020 - 05:24 PM

I'll admit that I HATE the polar alignment scope on the EQ6-R Pro. The main issue I have with it is that to orient it with 0 at the top, you have to rotate the mount to a certain angle, but it's done by eye so it's possible to be off slightly. I'm going to look into getting a Polemaster(I think that's what it's called), and hopefully that'll help.

You're not the only one, and it's not limited to the EQ6-R.  My Celestron AVX is similarly numb. 

 

The solution I use is credit to The Elf here on CN:  With the alignment scope oriented with the little circle at the exact top, turn on the mount and tell it to GoTo Polaris.  That will rotate the RA to be exactly where it needs to be.  Zero cost, highly accurate.



#23 venyix

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Posted 19 October 2020 - 08:21 AM

I decided to purchase this monster reducer about a month ago, and for poops and giggles, I tried to get it to work with my 80mm ES scope. Although, no matter how far back I push the spacing, it still seems to need to be further back. This isn't TOO surprising because it's probably mainly meant for the larger refractors, but I'm planning on getting a larger one in the near future anyway, so I can always hang onto it. The problem is that I spent 7 hours last night with this reducer and the Astromania flattener, and I was never able to get them pushed far enough back to remove artifacts from the images. I'm going to upload some images soon showing my struggles, and each image has that "blown out from the center" look that is supposed to mean you need to add more spacing. Is it just me or this scope?



#24 venyix

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Posted 19 October 2020 - 10:31 AM

I don't know why its gray. It shouldn't. Try and stop guiding for a sec and see if you can change it to arcsec.

 

In any case, if you are using the guide scope and guide camera from your signature then your guide scale is 7.3"/pixel. That is quite big and I would suggest you think about barlowing your guide camera to get better resolution. Your guide stars are basically 1 pixel. That's not really efficient guiding.

 

Looking at your RA rms vs DEC rms it clearly shows that RA is much bigger than DEC but I don't know what is the time scale of the PHD2 plot you posted. Anyways, your RA rms is 1.45" and DEC rms is 0.3". That will explain the elongation you're getting in your sub.

 

 

So I plate solved your image and the elongation is on the RA axis. So, my comment from above is probably what is happening.

Ok, so using this reducer https://explorescien...d-apo-152mm-f-8 I was able to take this image. However, it the corners of the image have this weird + shape version of the stars. Is this too much spacing? too little? This process is so FRUSTRATING!!!

 

Here is a 5 second L sub using the reducer

https://drive.google...iew?usp=sharing



#25 imtl

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Posted 19 October 2020 - 01:39 PM

Ok, so using this reducer https://explorescien...d-apo-152mm-f-8 I was able to take this image. However, it the corners of the image have this weird + shape version of the stars. Is this too much spacing? too little? This process is so FRUSTRATING!!!

 

Here is a 5 second L sub using the reducer

https://drive.google...iew?usp=sharing

You need more spacing. However, this reducer is not designed for your scope so it won't give you ideal results and might actually just not work well with your current telescope. Reducers/flatteners are usually specifically design to handle certain speeds/focal lengths.




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