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New Camera – EAA with ZWO ASI224 with NexStar 8SE

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#76 mclewis1

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Posted 25 September 2015 - 12:07 PM

You have to be careful when comparing other cameras and other stacking software.

 

Certainly when to stop (if at all) the stacking is a personal choice but there are other variables at play.

 

In the case of the LodeStar X2 it using a substantially more sensitive sensor than the 224 so there's more data in each of the initial exposures which makes the initial stacks look a little better (so the stack looks better with fewer exposures but there may be more noise present). Then there are the algorithms being used by the stacking software. High dynamic range (HDR) stacking really helps the sensitive sensor by not blowing out the brighter parts of an object, this allows for more aggressive histogram adjustment (allowing for more faint detail to be brought out). This difference makes it difficult to directly compare images from the different cameras.

 

With the variety of software options available we now have to ask a lot of questions about how an image was created to understand what we are seeing and how that would compare with something we are more familiar with.

 

Speaking of questions ... Martin, how did you take those really nice 7331 images?



#77 Astrojedi

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Posted 25 September 2015 - 12:35 PM

Hiten, I really like the results you're getting with that camera. I'm of the opinion that low read noise (and high QE!) is the future of EAA as it opens up some nice low-budget approaches that don't have to sacrifice image quality (yes, I'm talking stacking lots of short subs…).

 

Just to give my take on the "how many subs" question. One often hears imagers say beyond 30 is a case of diminishing returns, and EAA types suggest not much improvement after 3 or 4. My own view is that photons should be collected for as long as you want to observe an object (which might run into 10s of minutes), and not to do so is a waste. My experience is that quality continues to improve during that time (as physics says it should), and the apparent absence of improvement is, I believe, largely a matter of visual psychophysics -- the just noticeable difference between a stack of N and a stack of N+1 gets smaller. Anyway, here are some not-very-scientific captures of short subs of NGC 7331 from the other night, where I saved the image approximately on each doubling of sub count, and the improvement I think is present and worthwhile. I had to reduce the image a bit due to size limitations.

 

attachicon.gifNGC7331a.png

 

Keep up the great work

 

Martin

 

Thanks Martin. I agree with you on both points.

 

My motivation behind this thread is to show the EAA possibilities of a high QE low read noise camera. These two attributes are critical for delivering higher resolution without sacrificing speed.

 

In my view higher resolution is very important for EAA if we want to get closer to what the eyes can see and beyond. The speed is also very important in bringing the experience to folks who don't have EQ mounts or expensive optics.

 

On a related note, I think with appropriate software to wrap this camera it is possible to create a user experience which far exceeds the capability and perceived simplicity of video cameras and is more accessible (maybe I will write the SW myself since the camera manufacturer has no interest in investing in EAA).

 

When I am by myself many times I let the integration run to 10mins+ in the background since I typically spend 10-15 minutes observing an object anyways. The key for me though is that I see the first frame within 10-15s and a pretty good image within 1-2 minutes (to keep the experience 'live'). Ultimately the laws of physics are what they are and the more photons you collect the better the image. I do definitely see the difference after a few minutes but you need a higher resolution camera/image to appreciate the difference.

 

Hiten
 


Edited by Astrojedi, 25 September 2015 - 01:44 PM.


#78 Astrojedi

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Posted 25 September 2015 - 01:40 PM

You have to be careful when comparing other cameras and other stacking software.

 

Certainly when to stop (if at all) the stacking is a personal choice but there are other variables at play.

 

In the case of the LodeStar X2 it using a substantially more sensitive sensor than the 224 so there's more data in each of the initial exposures which makes the initial stacks look a little better (so the stack looks better with fewer exposures but there may be more noise present). Then there are the algorithms being used by the stacking software. High dynamic range (HDR) stacking really helps the sensitive sensor by not blowing out the brighter parts of an object, this allows for more aggressive histogram adjustment (allowing for more faint detail to be brought out). This difference makes it difficult to directly compare images from the different cameras.

 

With the variety of software options available we now have to ask a lot of questions about how an image was created to understand what we are seeing and how that would compare with something we are more familiar with.

 

Speaking of questions ... Martin, how did you take those really nice 7331 images?

 

Mark,

 

You make a valid point but it is getting harder to separate the camera and the software especially since the market is getting so siloed (Lodestar Live only supports SX, Infinity only supports Atik). It is the combination which delivers the EAA experience (integration is I think overall is a positive trend for simplifying the experience).

 

On a side note: I love my Lodestar X2 but I disagree that the Lodestar X2 has a more sensitive sensor. The QE is very similar to the 224. Also need to compare apples to apples here. Comparing a mono sensor to a sensor with an RGB bayer matrix is not quite appropriate. Also cannot compare 10s exposures with the ASI224 to 30s exposures with the Lodestar.

 

If anything, I think it is the other way around. The 224 with 3.75 micron pixels (vs. 8.2 microns for the Lodestar X2C - a more appropriate comparison) and an RGB matrix delivers better dynamic range, color and higher resolution than my Lodestar X2C for the same sub exposure time (based on my unscientific tests).

 

Hiten



#79 MartinMeredith

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Posted 25 September 2015 - 04:42 PM

Hi Mark

 

Thanks. The NGC 7331 + Fleas were captured with my Skywatcher 8" f/4 Newtonian and Lodestar X2 mono via LodestarLive, mounted on an AZ-EQ6 in alt-az mode. I used live dark subtraction, adjusting the black and white points, brightness and contrast online during the data capture, and I'm pretty sure I used x^0.25 compression to prevent the core burning out. Skies were not particularly great at SQM 18 with a quarter moon (I can get down to 20.6 here on a moonless night at the back of the house, but these were shot at the front where there's quite a bit of illumination from street lamps in the village). No wind to speak of for a change. I reckon seeing was not too bad judging by a shot of Stephan's Quintet I looked at on the same evening which showed a lot of faint detail. NGC 7331 is quite bright though.

 

Martin



#80 mclewis1

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Posted 25 September 2015 - 08:39 PM

Hiten,

 

I meant X2c ... I'd only compare a color sensor with another color sensor.

 

I'd love to see the raw images compared between the two cameras ... taken side by side, 10, 20, and 30s exposures ... no stacking. 



#81 Astrojedi

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Posted 26 September 2015 - 12:07 AM

Mark,

 

I don't have my X2C with me right now but I posted some comparison stacks with the X2C earlier in the summer. See here: http://www.cloudynig...-8se/?p=6746787

 

While these are 5s exposures I also tried 10s exposures. Since the purpose of this thread is to understand what is possible in terms of EAA with an Alt Az mount I have limited the exposures to what my NexStar mount can handle.

 

In all instances I could not achieve the same dynamic range as with the ASI224. In my view the sensors have similar QE but due to lower read noise  shorter exposures are possible with the ASI224.

 

If you are able to do 20s+ exposures I found the difference largely diminishes. With my AVX at 30s-45s exposures the results are pretty similar (but need to keep in mind that the ASI has a higher resolution, a more obstructive RGB matrix and much smaller pixels)

 

-Hiten 


Edited by Astrojedi, 26 September 2015 - 12:11 AM.


#82 DonBoy

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Posted 27 September 2015 - 05:24 PM

 

My second question was if the 25 frames really needed, if you see a noticeable improvement between stack 20 and stack 25. With my Lodestar I don't see any improvement after the third or fifth frame. You may have already answered this on this thread. If the ASI is, indeed, noisier than the Lodestar, than a larger stack may be beneficial to smooth out all that noise.

 

Thank you,

--Dom

I generally try and keep the stacks to a minimum and look to get away with 5 to 10 stacks and this works fairly well when broadcasting.  But I deliberately took a 20 stack set of M103 to show the improvement over a 5 stack

 

M103-15SG250G50-082615-5stack.jpg

 

M103-20STK-15SG250G50-082615-20stacks.jpg

 

The full resolution of these images can be found here:

 

https://www.flickr.c...57656927157919/

 

https://www.flickr.c...57656927157919/


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#83 MartinMeredith

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Posted 28 September 2015 - 06:23 AM

Great shots of M103 Don. The improvement is more noticeable on the full resolution images, at least on my monitor. In a broadcasting context I can see that the 5 stack is more than adequate (esp. to get across the colour contrasts) but the 20 stack does a good job of clearing up the background noise and eliminates potential faint stellar false candidates. When looking for fainter objects e.g. QSOs, or measuring the limiting magnitude, longer stacks have some advantages.

 

BTW, I find the colour balance to be a little on the green side but maybe that's my monitor. 

 

Martin



#84 DonBoy

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Posted 28 September 2015 - 11:52 AM

Tnx Martin for your comments.  The green tint isn't as apparent to my eyes so would you be so kind as to take the higher resolution image and adjust tint as an example of what you would feel color balance should be and post it here if that's an OK thing to do. And would you possibly look at the rest of the high resolution ASI224 album in Flickr and comment on the color balance.

 

https://www.flickr.c...57656927157919/

 

There is no auto color balance in the software used to capture these images so depending on which of three monitors I'm using will obviously effect the color balance of the captured image, which were captured via the 'Save' button in AstroToaster.  I also noticed that the lower resolution images which were downsized from iPhoto to be ever so  slightly different than the Flickr higher resolution images.



#85 MartinMeredith

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Posted 28 September 2015 - 12:09 PM

I'm no colour expert. This is just a central crop adjusted with the Adjust Color option of Preview on the Mac. I've just turned the temperature down to the lowest setting (I think it could go lower -- still too green for me, but I ran out of adjustment). This is based on a comparison with a few of the better looking images on the web which show mainly electric blue with a few orange stars sprinkled in. It would be interesting to see how others' monitors show it.

 

m103_crop.png

 

In any case, I'm hoping to observe this and a few other clusters in Cas tonight to evaluate OSC vs RGB so will see what I can get too...

 

Martin 

 

BTW, the images in the gallery look well-balanced in the main to me.


Edited by MartinMeredith, 28 September 2015 - 12:10 PM.


#86 DonBoy

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Posted 28 September 2015 - 01:10 PM

It does look like the temperature of these captures could have been made cooler.   Thanks for pointing that out and taking the time to give me an edited example.  

 

As to monitors my MacBook Pro seems to have the best color rendition compared to my other two larger monitors.  Next time I'll try to be more accurate in my color balance.   One tends to be more tolerant (less fussy) when broadcasting, and half the time I forget to click the shutter (save button), so I'm glad I have these few images.



#87 mclewis1

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Posted 28 September 2015 - 02:30 PM

I prefer the color balance in Don's original image. 

 

I agree that the majority of images floating around do show more intense blue stars but something has always bothered me about those images ... it's almost like we are seeing only intense blue or orange/red stars in these clusters, nothing in between. I recognize that in some clusters that may indeed be the makup of the types of stars (only young blue and older red) but it seems to show up in more and more images.

 

For example I have seen more of this in other DSO images (not just in open or globular cluster). So while I may buy that many star clusters have this specific (young/old) distribution I'm having a harder time believing it when I see in the general population of stars.

 

I have a hunch we are seeing something caused by the spectral sensitivity of the cameras and the aggressiveness in image processing methods rather than what is "really" there (if we could stand and look at things with our naked eyes).

 

Just call me a color skeptic I guess.



#88 Don Rudny

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Posted 28 September 2015 - 02:49 PM

I agree with Mark, but I do think it was a bit green as Martin pointed out.  I downloaded Don's image into Neb 3 and used the auto balance tool and got this.  I could see just a slight change.  Not sure how this works, but it does seem to give a good balance on most things I try.

 

Don, hope you don't mind us tinkering with your already great image.

 

DB's M103.jpg


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#89 DonBoy

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Posted 28 September 2015 - 03:03 PM

 

I agree with Mark, but I do think it was a bit green as Martin pointed out.  I downloaded Don's image into Neb 3 and used the auto balance tool and got this.  I could see just a slight change.  Not sure how this works, but it does seem to give a good balance on most things I try.

 

Don, hope you don't mind us tinkering with your already great image.

Don,  I don't mind in the least.  I appreciate everyone's efforts and comments.   I'll have to try that feature in my copy of Nebulosity.   I find that adjusting color is not a stable and repeatable in FC and using AstroToaster without a histogram doesn't make it any easier.   I've used oaCapture on the Mac and it takes a bit of tweaking to get a fair white balance manually but setting the red and blue adjustments to auto doesn't seem to work to my liking.  I've noticed that in terrestrial images that the color never matches what I see with my eye vs. the ASI224.  Adjusting the blue and red just never gets it 100%. 



#90 Astrojedi

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Posted 28 September 2015 - 03:15 PM

Don,

Not sure if you used a LP filter for this image. I have found that certain filters throw off the color more than others.

 

Hiten



#91 DonBoy

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Posted 28 September 2015 - 03:18 PM

Hiten, I used an Idas P2 LPS filter for the ASI224 images.  It is one of the few with a fairly neutral color response.



#92 MartinMeredith

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Posted 28 September 2015 - 05:54 PM

Colour balance is a tricky one for sure. If you look at the DSS coloured images such as this one of M103, the clusters do tend to be dominated by blues and oranges though.

 

M103_SDSS.png

 

I was really struggling tonight to pick up any blue under a nearby full moon… though orange was not a problem. Here's a central crop of M103 with the Lodestar X2 mono and Baader RGB filters (4 x 15s in each)

 

M103_RGB.png

 

I was a bit surprised as the same kit has delivered good colours e.g. this fragment of M7

 

M7fra.png

 

Anyone know whether strong moonlight is more likely to differentially affect the colour response of RGB filters? Sorry for taking the thread slightly off-topic too but the matter did come up and all data helps...

 

Martin



#93 Howie1

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Posted 29 September 2015 - 10:07 PM

AstroJedi and DonBoy, you guys have answered my yearnings ... just gotta go get the zwo and FC!

 

I have a neck and back injury which as I have gotten older has played up more and more, so I have downsized more and more scopes. Now using a lightweight and quick to setup 6SE AltAz. Have been using other vid cams for 5 years, but never really happy with the blocky stars and bloated cores and serial converters and grabbers and such all over the place.

 

Then I only recently saw AT demo'd on NSN. That is what got me thinking! If there are great results from a Canon EOS with 60 sec stacked and auto rotated images in AT, I wondered what some of the 825 sensor cams could do and in my googling came across this thread. 

 

Top job guys!

 

I am not looking for CCD quality shots, but I would like better star sharpness and colours than what I get with vid cams. And I do not care one hoot if I have to wait a couple of minutes while watching shots stack up and the image coming to life (so to speak) while that happens. Live viewing (EEA) for me is seeing a decent image while still out in the field at night - IE not processing the images at home well after the night out.

 

So I was going to update the 4 yo video camera, and was hunting down latest offerings of those. But given the reasonable price of the ASI224 I am going to give it a go.

 

So, you guys rock. Thanks.

 

Howie



#94 Astrojedi

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Posted 30 September 2015 - 02:03 AM

Howie, you will enjoy the camera... works well on an Alt Az mount... best of luck and feel free to reach out if you have any questions.



#95 Astrojedi

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Posted 30 September 2015 - 02:10 AM

Dom,

 

Here is the M27 using a stack of 5x35s frames with my AVX. Very similar to the earlier version that used shorter 10s exposures.

 

Ultimately, need to accumulate a certain number of photons. The low read noise of the camera allows very short exposures without losing dynamic range. After about 5 subs the noise is also pretty well mitigated.

 

Edit: some context on conditions... the seeing was maybe slightly better to the other night, also the moon was out (nearly 90% disk) but in the East (the other side of the sky). But overall similar conditions.

 

Hiten

 

M27 5x35s.jpg


Edited by Astrojedi, 30 September 2015 - 12:26 PM.

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#96 Don Rudny

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Posted 30 September 2015 - 11:49 AM

Here's some encouraging news from Paul Shears, developer of LL, now Starlight Live.  His program would be great with the ASI224.  A Mac version, too.  May have to wait a while though.

 

http://stargazerslou...-v11/?p=2767749



#97 Dom543

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Posted 30 September 2015 - 12:48 PM

Thank you Hiten for not forgetting my question.

 

It is interesting to compare the 175 sec total and 250 sec total captures. The comparison of the two images more than answers my question whether there is a significant improvement between 200 and 250 sec.

 

I understand that some people like to leave stacking on all the time, while they are on the same object and I have nothing against that. I, personally, am a minimalist type. When travelling alone, I ask for hotel rooms with twin beds and sleep in only one of those. When I am not distracted by other things, I turn off stacking as soon as see an image that I like. Fearing that an airplane flying through or a hiccup by the mount would destroy it.

 

Thanks again for taking the time to shoot the second image and satisfy my curiosity.

 

Clear Skies!

--Dom


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#98 Astrojedi

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Posted 30 September 2015 - 07:57 PM

Dom, in my view there is no right or wrong approach to EAA. Enjoyment of this hobby is ultimately a very personal experience and everyone should be free to experiment and find out what works best for them.



#99 Howie1

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Posted 01 October 2015 - 06:59 PM

Howie, you will enjoy the camera... works well on an Alt Az mount... best of luck and feel free to reach out if you have any questions.

Thanks Hiten. Ordered ASI224 yesterday. Should be delivered early next week. About to download FireCapture and start mucking about with that. Already have AT and have used it so at least that's one thing out of the way on the learning curve.  Cheers

Howie.



#100 Relativist

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Posted 04 October 2015 - 05:36 PM

Martin,

 

I agree, that's a good example of what happens overtime with such stacking. For example, often in the observing/eyepiece forums there are discussions of observing the same object for long periods of time to study and to see deeper and deeper. Such stacking practice is equivalent to that IMO in that the changes become subtle from frame to frame, or moment to moment, but the overall effect is significant.




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