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Help getting ready for 2023 Planetary with a 9.25” SCT please

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#1 mayhem13

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Posted 20 February 2023 - 09:52 AM

Hey folks……so sold off the 14” goto Dob and staying focused on using my EQ mount and C9.25….the seeing here in the NE US doesn’t often support bigger apertures…..I’ve been at 12 and 14 dobs . I’d like to optimize my imaging train for this purpose by purchasing the right visual back, Barlow and Camera to match. 
 

So camera question up first obviously. I’ve been using the 224mc for 2 years now and it’s 3.7um pixels were a good match for the 14 Dob with 3x and 4x Barlows…..but I suspect there’s something out there that’s a better match with all the new cameras for planetary as of late. I’ve been focused on the asi585mc and the asi482mc. The tiny pixels of the 678mc are also intriguing. Curious to hear everyone’s thoughts and thanks!


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#2 norvegicus

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Posted 20 February 2023 - 10:13 AM

I didn't like the 482 with my C9.25, lots of plate solving failures, as the field was too narrow with that tiny sensor; even finding planets by hand was kind of a pain.  Also it was noisy and fiddly to get the cailbration frames right.  I sold it.  


Edited by norvegicus, 20 February 2023 - 10:14 AM.


#3 Oberon510

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Posted 20 February 2023 - 10:24 AM

Not sure how good the formula is but you may want to mix and match with CCD suitability calculator - ("https://astronomy.to...ccd_suitability'). My ASI071MC I find better than most planetary cameras but maybe that is just my fiddling with resolutions and binning. A cooled camera helps with lots of video work on the planets.

 

Good luck



#4 gfstallin

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Posted 20 February 2023 - 10:36 AM

I had good experience with the 678MC last fall with a C11 - haven't used it with the C9.25 but the focal ratio is the same. Removing the barlow from the equation was quite liberating and the field was generous by ASI224MC standards. It makes finding your target a little easier. Color saturation was a bit lacking, but easily fixable in post processing. Sensitivity in IR was great. 

 

George


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#5 Tulloch

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Posted 20 February 2023 - 05:02 PM

I still have great success with my ASI224MC on a C9.25" SCT using a 2.5x Powermate. However, I understand the appeal of the wider FOV with either the 585 or 678. Either camera would be a great option (as would the 224 wink.gif ). Con/Ittaku loves his 585 (Uranus-C) while Don/dcaponeii is doing great things with the 678...

 

Andrew


Edited by Tulloch, 20 February 2023 - 05:04 PM.

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#6 Borodog

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Posted 20 February 2023 - 05:47 PM

Highly recommend the 678.
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#7 mayhem13

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Posted 20 February 2023 - 09:46 PM

I’m thinking the 678 too. No Barlow needed I would assume? Reducing the ROI to the same as the 224 I wonder what the frame rate jumps up to?



#8 Jan_Fremerey

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Posted 24 February 2023 - 12:18 PM

So camera question up first obviously.

3.75 µm is good for an f/10 telescope without Barlow. I'm working with 2.4 µm at f/5 to full satisfaction.

 

CS Jan
 



#9 mayhem13

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Posted 24 February 2023 - 03:09 PM

3.75 µm is good for an f/10 telescope without Barlow. I'm working with 2.4 µm at f/5 to full satisfaction.

 

CS Jan
 

I went with the 678 and the 2um pixels.......5x pixel size for F ratio puts me right at the native F10 and if the seeing is ever exceptional, i have a 2x on hand. Thanks for the feedback!


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#10 Jan_Fremerey

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Posted 24 February 2023 - 06:35 PM

5x pixel size for F ratio

What should "5x pixel size for F ratio" be good for when 2x gives excellent results at more than 6x shorter shutter times and 6x higher fps for better suppression of seeing-related image blur and signal noise?
 



#11 Tulloch

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Posted 24 February 2023 - 07:05 PM

What should "5x pixel size for F ratio" be good for when 2x gives excellent results at more than 6x shorter shutter times and 6x higher fps for better suppression of seeing-related image blur and signal noise?
 

Jan's theory is not based upon side-by-side testing of barlowed/non-barlowed measurements in the field, has not been verified or even agreed to by other planetary imagers and is not recommended by experts in the field.

 

And despite previous asssurances that he would not be urging others to image at 2x pixel size, here we are.


Edited by Tulloch, 24 February 2023 - 07:05 PM.

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#12 Jan_Fremerey

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Posted 24 February 2023 - 08:26 PM

not recommended by experts in the field.

I won't convince experts, I just try to prevent newcomers from unnecessary expenditure.
 


Edited by Jan_Fremerey, 24 February 2023 - 08:26 PM.


#13 Mitchell Duke

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Posted 24 February 2023 - 08:51 PM

I won't convince experts, I just try to prevent newcomers from unnecessary expenditure.

There is a point where the higher fps has diminishing returns. Just think about it for a minute. You are taking the same image of the same object with little change.
Its a proven fact seeing is king not camera settings.
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#14 Kiwi Paul

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Posted 25 February 2023 - 12:22 AM

I think Andrew may have presented the math and how it has been simplified to the 5x rule with regard to the ideal f/ ratio ( if not Andrew then this background has been presented and discussed by others on a number of occasions I can recall).
Anyway I am happy to follow this guidance and do.
I was interested in the comment that Mitchell made above i.e. that “higher fps have diminishing returns”. I have often wondered about this and would use the reasoning that the distortion of the image through processes that degrade the image must, most of the time, occur at some typical rate for much of the time and with higher rates for lesser amounts of time. This would imply that there would be a limit to the usefulness of very high frame rates. If they start to exceed the typical rate of distortion then it would follow that many frames would be similar to the previous one.
Is this reasoning reasonable!!
Cheers Paul

Edited by Kiwi Paul, 25 February 2023 - 01:21 AM.


#15 mayhem13

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Posted 25 February 2023 - 04:52 AM

I think Andrew may have presented the math and how it has been simplified to the 5x rule with regard to the ideal f/ ratio ( if not Andrew then this background has been presented and discussed by others on a number of occasions I can recall).
Anyway I am happy to follow this guidance and do.
I was interested in the comment that Mitchell made above i.e. that “higher fps have diminishing returns”. I have often wondered about this and would use the reasoning that the distortion of the image through processes that degrade the image must, most of the time, occur at some typical rate for much of the time and with higher rates for lesser amounts of time. This would imply that there would be a limit to the usefulness of very high frame rates. If they start to exceed the typical rate of distortion then it would follow that many frames would be similar to the previous one.
Is this reasoning reasonable!!
Cheers Paul

I come from the long exposure side of things where the camera spec highlight is on full well depth and Qe where if the photons fill up a pixel and they spill over into the adjacent pixels that are dark or empty, the star ‘bloats’ and requires reduction in processing. I suppose the same can be said for areas of contrast where planets are concerned. Smaller pixels do fill up with photons faster and color cameras are more prone to spillover due to the arrangement of the bayer matrix. 
 

Maybe what Jan is suggesting is just an observation based on the fast optics used in his use case where at f5 there are 5x the photons hitting the sensor than at f10 instead of what we understand as a mere 2x due to the increase image scale. In this case, reducing the frame rate combined with larger pixels would in fact provide increased contrast. There’s also Qe to consider as well which will be a determining factor on contrast. 
 

I think there’s more analytical work to be done with lucky imaging and how those parameters work within the methods we use to capture planets. I suspect just as in deep sky AP, the REAL answers lie in analyzing the individual sub exposures or frames. But such analysis would be difficult in real case use as astronomical seeing is never consistent. One would need a consistent simulation of a light source with significant surface contrast to capture and analyze. 
 

When the seeing is poor and the target is jumping around, i increase the frame rate based on the observation…..but I can only increase that frame rate by increasing the gain if the histogram is given consideration.,…with an F5 scope this wouldn’t be necessary….or even at F10 compare to the F20 and higher we often use. Hmmmm……I feel like the real answer lies in those pixel well depths and Qe.


Edited by mayhem13, 25 February 2023 - 04:53 AM.

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#16 Jan_Fremerey

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Posted 25 February 2023 - 05:27 AM

This would imply that there would be a limit to the usefulness of very high frame rates. If they start to exceed the typical rate of distortion then it would follow that many frames would be similar to the previous one.

Please have a look at the slow motion demo of 6 consecutive frames extracted from a recent Mars video taken at 555 fps. There certainly is some essential difference between adjacent frames even at this rate as otherwise we would not notice mars image moving around on the camera grid.

 

CS Jan


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#17 Jan_Fremerey

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Posted 25 February 2023 - 06:01 AM

There is a point where the higher fps has diminishing returns. Just think about it for a minute. You are taking the same image of the same object with little change.

Please have a look at my previous post.



#18 Kiwi Paul

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Posted 25 February 2023 - 01:53 PM

Please have a look at the slow motion demo of 6 consecutive frames extracted from a recent Mars video taken at 555 fps. There certainly is some essential difference between adjacent frames even at this rate as otherwise we would not notice mars image moving around on the camera grid.

CS Jan

That’s an interesting point. The body of the planet does move around as you say. So perhaps the limiting frame rate is a lot higher than 555fps which few people would ever reach.
It has been an interesting discussion to follow.
Cheers Paul

Edited by Kiwi Paul, 25 February 2023 - 01:54 PM.

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#19 Jan_Fremerey

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Posted 26 February 2023 - 06:06 AM

Its a proven fact seeing is king not camera settings.

That's exactly what makes lucky imaging beneficial to high resolution astro imaging, i.e. by collecting short term exposures at maximum frame rates for optimum elimination of seeing related blur and signal noise.



#20 wargrafix

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Posted 27 February 2023 - 12:20 PM

Hey folks……so sold off the 14” goto Dob and staying focused on using my EQ mount and C9.25….the seeing here in the NE US doesn’t often support bigger apertures…..I’ve been at 12 and 14 dobs . I’d like to optimize my imaging train for this purpose by purchasing the right visual back, Barlow and Camera to match. 
 

So camera question up first obviously. I’ve been using the 224mc for 2 years now and it’s 3.7um pixels were a good match for the 14 Dob with 3x and 4x Barlows…..but I suspect there’s something out there that’s a better match with all the new cameras for planetary as of late. I’ve been focused on the asi585mc and the asi482mc. The tiny pixels of the 678mc are also intriguing. Curious to hear everyone’s thoughts and thanks!

gallery_218407_320_77785.jpg

 

The Celestron 9.25 is an incredible scope. Seeing is the make or break for planetary imaging


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#21 Tulloch

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Posted 27 February 2023 - 05:45 PM

I won't convince experts, I just try to prevent newcomers from unnecessary expenditure.

You will convince experts, but only with proof. Evidence. Results. Measurements.

 

Your theory is based on one simulation from one set of data. Collect more - much more.


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#22 Jan_Fremerey

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Posted 27 February 2023 - 07:04 PM

You will convince experts, but only with proof. Evidence. Results. Measurements.

Results: there is sufficient information with images on top of my website for measurement as well as comparison with published long-focus results from similar aperture under optimum seeing conditions.
 



#23 Jan_Fremerey

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Posted 28 February 2023 - 06:30 AM

You will convince experts, but only with proof. Evidence. Results. Measurements.

Measurements: Taking image resolution data from figure captions of Jupiter, Moon and M3 you may easily "measure" image detail by pixel counting.

 

Ju-Mo-M3_Mag6x.jpg

 

Pixel resolution is 0.15", 0.21" and 0.28", respectively.

 

CS Jan


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#24 Kiwi Paul

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Posted 28 February 2023 - 06:57 PM

Interesting. This does remind me of the looking through a sieve. Need to think about this some more.
Cheers Paul

#25 Jan_Fremerey

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Posted 28 February 2023 - 07:31 PM

looking through a sieve.

Dear Paul,

 

I should mention at this point that the above sieve patterns reflect the digital image structure which is much finer than the camera grid was in the above examples with 0.32", 0.39" and 0.39", respectively.

 

CS Jan
 




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