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Something for nothing: Celestron C90

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#2351 Sarkikos

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Posted 20 April 2019 - 09:15 AM

I seem to recall some old saying about a picture is worth a thousand words...  shrug.gif

 

Bob F.  smile.gif

But that does depend on the picture.

 

:grin:

Mike


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#2352 johnhudson922

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Posted 13 June 2019 - 12:12 PM

Would this scope be a good way to get into Planetary astrophotography? I have a Canon 6d, not great for this, but can use BYEOS to run it all. I like the focal length...



#2353 Jaimo!

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Posted 13 June 2019 - 08:51 PM

Would this scope be a good way to get into Planetary astrophotography? I have a Canon 6d, not great for this, but can use BYEOS to run it all. I like the focal length...

While it it possible to do planetary imaging with the C90 (see LINK) the limiting factor with the C90 is aperture.  If you have a mount and you have the camera...  I'd recommend stepping up to a 127mm Synta Mak (Celestron, Orion, SkyWatcher) they can easily be found in the classifieds for ~$200.  I do enjoy imaging with the C90 because of the challenge, just like the name of this thread, I like to try and show that imaging can be done inexpensively.  Also, you might want to look into a dedicated planetary camera, the ZWO cameras seem to be leading the pack...  and the 120mc can be had for $150.  Go to the Solar System Imaging and Processing forum and look around, it is a wealth of information.  This video is informative, and his series on planetary imaging is very good.  But if you have any specific question about the C90 this is the place, do not hesitate to ask.

 

Clear Skies,

Jaimo!


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#2354 Messierthanwhat

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Posted 11 July 2019 - 09:10 AM

At 1250mm, the C90 Mak is also a bit short for good planetary imaging. I've tried mine on Jupiter a couple of times recently, using my Canon T2i in 640x480 "movie crop mode" (See Jerry Lodriguiss's article here). In that mode, the planet covers roughly 70x70 pixels. Using AutoStakkert2! and GIMP's "wavelet-decompose" sharpening, the best image I've managed to produce (attached) is not very exciting.

 

MVI_9686_pipp_pipp.jpg

I also tried the wavelet sharpening function of Registax 2, but it seemed to add more artifacts than the GIMP filter. Since that effort, I took some time to do very careful collimation, and notice huge improvement in image quality from just the tiniest nudges of the screws. But my schedule and the Arizona monsoon skies have not cooperated to give me a chance to try again. 

 

According to Jerry's article, the 6D also has a 1:1 live view mode that would, as I understand it, produce an image of the planet the same size, but just in a wider field of view. But it would require capturing the live view with a computer, rather than on the card. 


Edited by Messierthanwhat, 11 July 2019 - 09:14 AM.


#2355 Adun

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Posted 12 July 2019 - 09:58 PM

At 1250mm, the C90 Mak is also a bit short for good planetary imaging. I've tried mine on Jupiter a couple of times recently, using my Canon T2i in 640x480 "movie crop mode" (See Jerry Lodriguiss's article here). In that mode, the planet covers roughly 70x70 pixels. Using AutoStakkert2! and GIMP's "wavelet-decompose" sharpening, the best image I've managed to produce (attached) is not very exciting.
 
attachicon.gif MVI_9686_pipp_pipp.jpg
I also tried the wavelet sharpening function of Registax 2, but it seemed to add more artifacts than the GIMP filter. Since that effort, I took some time to do very careful collimation, and notice huge improvement in image quality from just the tiniest nudges of the screws. But my schedule and the Arizona monsoon skies have not cooperated to give me a chance to try again. 
 
According to Jerry's article, the 6D also has a 1:1 live view mode that would, as I understand it, produce an image of the planet the same size, but just in a wider field of view. But it would require capturing the live view with a computer, rather than on the card.

 
 
From my post #8754628 on page 88 of this thread taken with a C90 and RT224 camera, and inexpensive SVBony 2x Barlow:
 
Jupiter image with C90 and IMX224

 

Saturn image with C90 and IMX224

 

Mars image with C90 and IMX224

 
Your Canon T2i has 4.3um pixels, which according to calculators (meant to help people match FLs/barlows/cameras), produces 0.71 arcsecs per pixel at 1250mm, which indeed is not great for planetary imaging, but it's not the fault of the 1250mm FL of the C90. 

 

One has to balance the pixel size, FL, aperture/resolution, and atmospheric seeing. Most people use barlows for planetary imaging, and choose carefully (between 1.5x, 2x, 2.5x, etc) to achieve this balance.

 

It's hard to find a 90mm telescope with longer FL than the C90, so I'd argue that in the 90mm class, the C90 is likely one of the better options for planetary imaging.

 

Did you use a bathinov mask? How did you achieve the best possible focus? 

How many (filtered, good) frames are stacked in your image? I got a real jump in quality when I went from dozens of frames to ~2000 (but be careful and keep videos shorter than the limit imposed by the planet's own rotation, and the az-mount field rotation).


Edited by Adun, 12 July 2019 - 10:02 PM.

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#2356 Orion68

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Posted 12 July 2019 - 10:24 PM

I had an orange c90 and was glad to re-sell it.
G

I had the same experience. Mine was way out of collimation so the images were pretty bad. Could not see any way to collimate it myself so I sold it to someone who insisted he could fix the collimation. Don't know if he succeeded or not.



#2357 Messierthanwhat

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Posted Yesterday, 12:43 AM

 
 
From my post #8754628 on page 88 of this thread taken with a C90 and RT224 camera, and inexpensive SVBony 2x Barlow:
 

 

 

 

 
Your Canon T2i has 4.3um pixels, which according to calculators (meant to help people match FLs/barlows/cameras), produces 0.71 arcsecs per pixel at 1250mm, which indeed is not great for planetary imaging, but it's not the fault of the 1250mm FL of the C90. 

 

One has to balance the pixel size, FL, aperture/resolution, and atmospheric seeing. Most people use barlows for planetary imaging, and choose carefully (between 1.5x, 2x, 2.5x, etc) to achieve this balance.

 

It's hard to find a 90mm telescope with longer FL than the C90, so I'd argue that in the 90mm class, the C90 is likely one of the better options for planetary imaging.

 

Did you use a bathinov mask? How did you achieve the best possible focus? 

How many (filtered, good) frames are stacked in your image? I got a real jump in quality when I went from dozens of frames to ~2000 (but be careful and keep videos shorter than the limit imposed by the planet's own rotation, and the az-mount field rotation).

Thanks for the input. I guess blaming the C90's FL is a matter perspective, and it makes just as much sense to blame the camera. Since both are what I have, and I don't yet find planetary exciting enough to justify additional expenditure, I should probably just blame myself.

 

I did use a Bahtinov mask to focus on Antares, then slewed over to Jupiter. And the stack was of 40% of a little over 2600 frames. I have three different 2X Barlows, but when I tried imaging with any of them in place, the image seemed to degrade badly. That is, without a Barlow, my live view in movie crop mode looked much like the final result posted. With any of the Barlows in place, it really just looked like a muddy mess.

 

I am looking forward to another try since I was able to visibly improve collimation with very little effort. I got some really sharp lunar closeups the night I did the collimation, but just haven't been able to find time for another stab at Jupiter.



#2358 Adun

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Posted Yesterday, 09:53 PM

Thanks for the input. I guess blaming the C90's FL is a matter perspective, and it makes just as much sense to blame the camera. Since both are what I have, and I don't yet find planetary exciting enough to justify additional expenditure, I should probably just blame myself.

 

I did use a Bahtinov mask to focus on Antares, then slewed over to Jupiter. And the stack was of 40% of a little over 2600 frames. I have three different 2X Barlows, but when I tried imaging with any of them in place, the image seemed to degrade badly. That is, without a Barlow, my live view in movie crop mode looked much like the final result posted. With any of the Barlows in place, it really just looked like a muddy mess.

 

I am looking forward to another try since I was able to visibly improve collimation with very little effort. I got some really sharp lunar closeups the night I did the collimation, but just haven't been able to find time for another stab at Jupiter.

 

For planetary imaging, I definitely need a 2x Barlow with the C90, and my camera has even smaller pixels than yours, so I'd say you need to find a way to use the Barlow.

 

It sounds like you added the Barlow after having already focused with the bathinov on Antares. If that was the case, you must focus with the Barlow on.




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