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M82, where is the Ha spikes?

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#1 solaryellow

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Posted 23 March 2023 - 08:39 AM

Had a little over 7 hrs using 3 minute subs. 

 

8" RC

Modded T3i

OAG-L 174mm 

Gem45 

 

I ditched the calibration frames because they created more of a mess in processing. 

150 lights in Siril.  

Besides the usual process in siril, i went into Gimp and made some curve adjustments. 

Then into LR for some color balance, saturation.. nothing drastic, but i would have thought i would get more of the Ha spikes you see in some pics.

Tell me its my DSLR so I can justify buying a true Imaging camera.   

 

 

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#2 KTAZ

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Posted 23 March 2023 - 08:49 AM

Well, ok, it's your camera! grin.gif

 

Actually, I'd recommend the true astrocam; however, you can consider a dual narrowband filter instead.

 

This was 12 hours with the L-eNhance. I have since switched to the Antlia ALP-T and like it much better. I intend to shoot this one again next time it comes around. This time with actual RGB stars.

 

get.jpg?insecure


Edited by KTAZ, 23 March 2023 - 08:49 AM.

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#3 Kerry D. Green

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Posted 23 March 2023 - 08:56 AM

It's your DSLR. lol.gif

 

The reality seems, with 7hours of data, that you should see more.  Seeing conditions, weather, temperature, etc. are going to be a factor.  That said, I think there are tricks you could use in your processing that would help.  A selective color mask would help isolate the red to stretch them a little more.  I have a tendency to mask the galaxy to suppress the background noise, but this often times suppresses the outlying galaxy details such as the spikes on M82.  The detail is most certainly there, but it is likely lower signal and hidden in the background which seems a bit dark.  I bet some additional processing could bring it out.

 

All that said, the QE of new dedicated cameras with the ability to actively cool is a very attractive package.


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#4 solaryellow

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Posted 23 March 2023 - 09:04 AM

Well, ok, it's your camera! grin.gif

Actually, I'd recommend the true astrocam; however, you can consider a dual narrowband filter instead.

This was 12 hours with the L-eNhance. I have since switched to the Antlia ALP-T and like it much better. I intend to shoot this one again next time it comes around. This time with actual RGB stars.

get.jpg?insecure


Thats what i was hoping for. Nice image!!!
I didnt use my reducer. Shot F8. My dslr OAG backspace is at 80mm. If i add reducer it would be almost 100mm. I coukd still get focus no problen, but reduction would be too much. I aim for .73.
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#5 solaryellow

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Posted 23 March 2023 - 09:14 AM

It's your DSLR. lol.gif

The reality seems, with 7hours of data, that you should see more. Seeing conditions, weather, temperature, etc. are going to be a factor. That said, I think there are tricks you could use in your processing that would help. A selective color mask would help isolate the red to stretch them a little more. I have a tendency to mask the galaxy to suppress the background noise, but this often times suppresses the outlying galaxy details such as the spikes on M82. The detail is most certainly there, but it is likely lower signal and hidden in the background which seems a bit dark. I bet some additional processing could bring it out.

All that said, the QE of new dedicated cameras with the ability to actively cool is a very attractive package.


I was trying to find a tutorial on masks, havent really mastered that.

Im in an out of PS, GIMP and LR. For various things.

I'll have to play some more.

#6 imtl

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Posted 23 March 2023 - 09:16 AM

It's because you don't use calibration frames.
With your DSLR
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#7 zakry3323

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Posted 23 March 2023 - 09:38 AM

Like imtl said, I'd first work on taking and applying calibration frames correctly and seeing how much better the result is before buying a new camera. Proper calibration is a fundamental step to getting the most of out your camera, whether that's your DSLR or whatever you purchase next. 


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#8 solaryellow

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Posted 23 March 2023 - 10:00 AM

It's because you don't use calibration frames.
With your DSLR

I had darks and bias, skipped flats. They made it worse in Siril.
Going to make new darks and bias, as well as flats and try again.

There was a temp difference on my previously used darks. Trying to make new ones that match better

Edited by solaryellow, 23 March 2023 - 10:01 AM.


#9 imtl

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Posted 23 March 2023 - 10:05 AM

Like imtl said, I'd first work on taking and applying calibration frames correctly and seeing how much better the result is before buying a new camera. Proper calibration is a fundamental step to getting the most of out your camera, whether that's your DSLR or whatever you purchase next. 

goodjob.gif


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#10 zakry3323

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Posted 23 March 2023 - 10:09 AM

I had darks and bias, skipped flats. They made it worse in Siril.
Going to make new darks and bias, as well as flats and try again.

There was a temp difference on my previously used darks. Trying to make new ones that match better

Bias calibrate flats, flats and darks calibrate lights. You can reshoot darks to better temp match, but if the sensor isn't in the same position at the same focus as when you shot your lights, your flats may not help, or they may make your lights worse. Best practice is to shoot your calibration frames before/after your imaging session while everything remains set up. 


Edited by zakry3323, 23 March 2023 - 10:10 AM.

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#11 James Peirce

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Posted 23 March 2023 - 10:11 AM

Your camera can do it… this doesn’t need to be a “get an astronomy camera” thing.

As noted above, take calibration frames seriously if you want to get the most out of images, but especially if you are interested in bringing up fainter details. They’re very important for concerns like separating faint signal from noise and bringing up faint signal in stretching without putting optical train issues that flats would have corrected on display. From there, taking care with the black level helps. The deeper blacks are pushed, the more challenging it can be to accent faint details and the more easily they are lost in various monitor calibrations.

And also noted above, but another great way to accent some specific structures like these is with narrowband data. You wouldn’t want to shoot the galaxy only in narrowband, but you could use a multi-bandpass narrowband filter and take the red channel from that data to serve as Hα data that can be combined with the broadband data through various specific techniques that vary depending on the post-processing software used. This trick is employed frequently in galaxy imaging to bring up those nebulous regions, but it does a very good job of boosting the Hydrogen-alpha structure in and around M82.
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#12 bbasiaga

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Posted 23 March 2023 - 10:35 AM

Bias calibrate flats, flats and darks calibrate lights. You can reshoot darks to better temp match, but if the sensor isn't in the same position at the same focus as when you shot your lights, your flats may not help, or they may make your lights worse. Best practice is to shoot your calibration frames before/after your imaging session while everything remains set up. 

Nevermind...mis undserstood what you said. 

 

 

-Brian


Edited by bbasiaga, 23 March 2023 - 10:36 AM.

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#13 bbasiaga

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Posted 23 March 2023 - 10:40 AM

This might be a candidate to post your stack (when you add the darks) and see if others can find those jets.  I posted some data I just couldn't do anything with and was amazed at what others did.  Got some pointers to up my processing knowledge along the way.  Still a long way to go.

 

-Brian



#14 bobzeq25

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Posted 23 March 2023 - 10:46 AM

Key point.  It's almost certainly a combination of things.  The DSLR is unlikely to be the most important.

 

Processing is a big one (but is complicated).  That background is awfully black.  That can remove dim detail.  A major reason why people make the background too black is that there are no flats.  So they raise the black point to "fix" it, and lose stuff.  Flats (and bias, necessary to make flats work) are basically required for decent images.

 

If your calibration frames make your image worse, you're either not taking them properly, or not processing well.  Siril is good for many people, but my usual recommendation to beginners is Astro Pixel Processor, and that could be better for you.  It calibrates and stacks really well.

 

A cooled astro camera will work better.  But there are other, more fundamental things you need to deal with.  Any modded DSLR should be able to capture the spikes some with 7 hours of exposure.  The astro camera is a good idea, but won't fix all the issues that caused you to have NO spikes.  That means other things are wrong.

 

The pretty pictures do not come easy.  <smile>


Edited by bobzeq25, 23 March 2023 - 10:50 AM.

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#15 solaryellow

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Posted 23 March 2023 - 10:51 AM

Camera is still setup in same orientation for more M82 data. So flats won't be a problem.
I have used these calibration frames on a couple other images ive done and they made a huge difference where it allowed me to process with much greater control..

My library of Darks and bias are somewhat varying.
But I went with the ones that closely matched the temp for that evening.
For some reason, after background extraction, the image was really noisy.
I have 3 nights of imaging on this, and temps were generally the same.
Going to do another 4 hrs and redo everything.
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#16 solaryellow

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Posted 23 March 2023 - 11:00 AM

Key point. It's almost certainly a combination of things. The DSLR is unlikely to be the most important.

Processing is a big one (but is complicated). That background is awfully black. That can remove dim detail. A major reason why people make the background too black is that there are no flats. So they raise the black point to "fix" it, and lose stuff. Flats (and bias, necessary to make flats work) are basically required for decent images.

If your calibration frames make your image worse, you're either not taking them properly, or not processing well. Siril is good for many people, but my usual recommendation to beginners is Astro Pixel Processor, and that could be better for you. It calibrates and stacks really well.

A cooled astro camera will work better. But there are other, more fundamental things you need to deal with. Any modded DSLR should be able to capture the spikes some with 7 hours of exposure. The astro camera is a good idea, but won't fix all the issues that caused you to have NO spikes. That means other things are wrong.

The pretty pictures do not come easy. <smile>

I'll look into APP.
Had used DSS since the day it it was invented, but it takes longer to stack.

Siril had been doing well for me, and im having a little trouble trying to see the differences with my Asighn stretching. I never set the black point above .007 and stay under 1 percent on the clipping.
Have always done 4 or 5 different adjustments and saved those images, bringing them into GIMP or PS to process further and looking for the best.
It is tedious for sure..

I will look into APP though.

Edited by solaryellow, 23 March 2023 - 11:00 AM.

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#17 James Peirce

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Posted 23 March 2023 - 11:01 AM

Camera is still setup in same orientation for more M82 data. So flats won't be a problem.
I have used these calibration frames on a couple other images ive done and they made a huge difference where it allowed me to process with much greater control..

My library of Darks and bias are somewhat varying.
But I went with the ones that closely matched the temp for that evening.
For some reason, after background extraction, the image was really noisy.
I have 3 nights of imaging on this, and temps were generally the same.
Going to do another 4 hrs and redo everything.

What software are you using? Generally speaking, when you do a background extraction (or some other operations like noise reduction) and then re-apply softwares auto-stretch it will stretch the image more aggressively and, in the process, display the faint signal noise more aggressively. It should balance out reasonably in stretching.

Some care is warranted with calibration frames. If there is a material difference in temperatures, which is very easy to accomplish when trying to draw from a library with a non-cooled camera, the calibration frames can correct poorly or even introduce issues. It can be a pretty good idea to plan in some dark frames during the session. Good timing is the period right before things get dark enough to image (if you set up in time) or can snag some right before packing up while winding down. Even 15-20 proper dark frames can make a big difference relative to attempting to approximate things. Bias can be a lot easier to re-use. And flats sometimes also require care. If things are set up and having been adjusted or knocked/tumbled around, they may still be very easy to capture. But there are some other things to watch for. For example, on many DSLRs, there is a sensor-cleaning operation that runs when shut down. This can shift positions of dust, creating mismatches with flats. But this can also usually be disabled. If the right is picked up and moved around that can also shift dust. Calibration frames are a fuss, to be sure, but they are also some of the most critical components involved in getting the most out of equipment. The fuss is worthwhile.



#18 arbit

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Posted 23 March 2023 - 11:16 AM

I'll look into APP.
Had used DSS since the day it it was invented, but it takes longer to stack.

Siril had been doing well for me, and im having a little trouble trying to see the differences with my Asighn stretching. I never set the black point above .007 and stay under 1 percent on the clipping.
Have always done 4 or 5 different adjustments and saved those images, bringing them into GIMP or PS to process further and looking for the best.
It is tedious for sure..

I will look into APP though.

I'd suggest the GHS stretching option.

Quite a few very good videos on it. Those are PI based but the UI in Siril is very similar.

You can do arcsinh and normal stretching with a lot of control.

Sent from my SM-S908E using Tapatalk

#19 Robert7980

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Posted 23 March 2023 - 11:55 AM

Just need to process it, all the red that's there is Ha so you picked up plenty, it's just hiding the background...

The DSLR is fine, an astro camera would have just picked it up in 30 minutes rather than 7 hours is all...

#20 bobzeq25

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Posted 23 March 2023 - 12:53 PM

Just need to process it, all the red that's there is Ha so you picked up plenty, it's just hiding the background...

The DSLR is fine, an astro camera would have just picked it up in 30 minutes rather than 7 hours is all...

The difference between a modded DSLR and an astro camera is _nowhere_ near that large.  Unmodded, sure.


Edited by bobzeq25, 23 March 2023 - 12:53 PM.

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#21 MrDan

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Posted 23 March 2023 - 02:15 PM

Wow....I get this now! Calibration frames eases and enhances the background extraction. You want as clean a background as you can get so you don't have to bury it with black point adjustment which hides all of the wisps we all long for. As I think one or two of you have said before.....Fundamental. If you process out a bad background....you process out detail. Ah Ha Moment! Thank you,

 

Dan

 

edit: I should have said proper calibration frames used properly


Edited by MrDan, 23 March 2023 - 02:19 PM.


#22 imtl

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Posted 23 March 2023 - 02:24 PM

Wow....I get this now! Calibration frames eases and enhances the background extraction. You want as clean a background as you can get so you don't have to bury it with black point adjustment which hides all of the wisps we all long for. As I think one or two of you have said before.....Fundamental. If you process out a bad background....you process out detail. Ah Ha Moment! Thank you,

Indeed, H alpha moment.


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#23 bobzeq25

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Posted 23 March 2023 - 02:32 PM

Wow....I get this now! Calibration frames eases and enhances the background extraction. You want as clean a background as you can get so you don't have to bury it with black point adjustment which hides all of the wisps we all long for. As I think one or two of you have said before.....Fundamental. If you process out a bad background....you process out detail. Ah Ha Moment! Thank you,

 

Dan

 

edit: I should have said proper calibration frames used properly

Also important.  Calibration frames let you stretch the data more.


Edited by bobzeq25, 23 March 2023 - 02:32 PM.

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#24 solaryellow

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Posted 23 March 2023 - 02:37 PM

In Siril.

First order.

Crop out bad stuff.
Background extraction
Color calibration.
Then asihn stretch.
Where sometimes unusual things happen, like when you raise black point one click, the image actually gets a tad brighter, before getting darker on the next click. I have learned to make a few smaller adjustments versus one shot. All subsequent adjustments are more sensitive and reactive. My understanding is asihn preserves color better.

However, after that, i would hit the auto histogram cog, and sometimes its perfect as is, and other times, blown up badly.
The new GHS i have also used by itself. Again samll adjustments looking at histogram.

I agree now it is most likely needing the calibration frames. So i am going to run the stack again, and start with some new darks, flats ans bias.

#25 Oort Cloud

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Posted 23 March 2023 - 04:58 PM

I hate to say it, but unless you have fairly dark skies, 7 hours at f/8 isn't really that much. 7 hours at f/5, for example, would be equivalent to over 14 hours at f/8.

Then there's the fact that your DSLR (assuming it's not modded) cuts H-alpha with its internal IR filter, because H-alpha doesn't matter for the terrestrial usage that DSLR cameras are designed for.

Now...it would be possible to get some of the H-alpha spikes in 7 hours, if you spent 3 hours collecting RGB and the other 4 collecting H-alpha with a mono camera. Maybe with OSC and a duoband filter, but then you're only using 25% of your pixels to capture the H-a, making it 25% as effective, so would likely need more than 4h for that part I think.


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