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M87 jet seen at F10 but not F2

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#1 descott12

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Posted 28 April 2019 - 11:21 AM

Hello all,

I typically use my HyperStar and have great results usually. However, after multiple attempts to view the jet (on multiple nights and different conditions), I failed to see it.  On both attempts with same camera but at F10, I was able to see it. Last night's view is not great as the cloud's were rolling in but it was immediately visible even before stacking.  Anybody else have the same issue? Does the jet simply need more magnification to view?

 

This tiny cropped image was taken with my Evo 8 + 294 MC at F10. Exp 6.5 seconds, gain 487, Total time 2:29. Note the real high gain. It didn't show up well and SC alignment was failing with a lower gain.

 

 

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Edited by descott12, 28 April 2019 - 11:21 AM.

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#2 DSO_Viewer

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Posted 28 April 2019 - 11:39 AM

Hello all,

I typically use my HyperStar and have great results usually. However, after multiple attempts to view the jet (on multiple nights and different conditions), I failed to see it.  On both attempts with same camera but at F10, I was able to see it. Last night's view is not great as the cloud's were rolling in but it was immediately visible even before stacking.  Anybody else have the same issue? Does the jet simply need more magnification to view?

 

This tiny cropped image was taken with my Evo 8 + 294 MC at F10. Exp 6.5 seconds, gain 487, Total time 2:29. Note the real high gain. It didn't show up well and SC alignment was failing with a lower gain.

It might be because the focal ratio using f/2 makes the focal length too short to see the jet since M87 is small to start with.

 

Steve



#3 pyrasanth

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Posted 28 April 2019 - 12:07 PM

It is possible that at F2 your capturing so much light with a small image scale that the jet is being lost in the glare of everything else. If you have PI try a masked stretch on one of the subs to see if the jet is there.


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#4 ngc7319_20

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Posted 28 April 2019 - 12:18 PM

The jet is only 1 arcsecond wide, so anything that can't resolve 1 arcsecond is going to lose it in the glare of the star light.



#5 OleCuss

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Posted 28 April 2019 - 01:00 PM

At F/2 you are grossly under-sampled with that camera.  There will be a lot of detail missed because of that under-sampling but if you aren't looking for the fine details you may never notice.

 

At F/10 you are over-sampled which means you have a little more read noise than is idea but with a low-noise sensor like the IMX294 it likely isn't enough noise to be noticeable.

 

Congrats on a nice image at F/10!

 

Note that the short focal length is not why it is not seen.  Your potential resolution of the OTA is determined by the aperture, not by the focal length.  But, as noted, under-sampling will decrease the potential resolution of the OTA/camera combination.

 

If you were to use an IMX183 (which has much smaller pixels) at F/2 you might see the jet.


Edited by OleCuss, 28 April 2019 - 01:04 PM.

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#6 descott12

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Posted 28 April 2019 - 02:02 PM

At F/2 you are grossly under-sampled with that camera.  There will be a lot of detail missed because of that under-sampling but if you aren't looking for the fine details you may never notice.

 

At F/10 you are over-sampled which means you have a little more read noise than is idea but with a low-noise sensor like the IMX294 it likely isn't enough noise to be noticeable.

 

Congrats on a nice image at F/10!

 

Note that the short focal length is not why it is not seen.  Your potential resolution of the OTA is determined by the aperture, not by the focal length.  But, as noted, under-sampling will decrease the potential resolution of the OTA/camera combination.

 

If you were to use an IMX183 (which has much smaller pixels) at F/2 you might see the jet.

Very interesting. Thanks for the explanation. That makes alot of sense. I have a 178 mono that I will try it with next.



#7 descott12

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Posted 28 April 2019 - 02:33 PM

I calculated images scales:

Evo 8 at F10 with the 294 (4.64 um pixel) is 0.47 arc-sec/pixel

Evo 8 at F2 with 294 is 2.36 arc-sec/pixel.

 

If the jet is only 1 arc-sec wide as post #4 above states, then this makes alot of sense. Very cool when the calculations actually prove themselves out in the real world.

 

If I use my 178 MM  with 2.4 um pixels, then the image scale will be 1.22 at  F2. Still might not be good enough but it is closer.



#8 OleCuss

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Posted 28 April 2019 - 05:25 PM

Good show that you get it!!!

 

It is something which people all too often forget about when choosing and using cameras so maybe a quick review is in order.

 

When working with the concept we need to think in terms of Arc-seconds Per Pixel (APP).  This is sort of a self-explanatory term in that our calculated/equipment version is about the number of arc-seconds of the sky each of your pixels will "see" with your telescope.

 

It is easy to forget that this is a mathematical concept which doesn't necessarily meet reality when you are out under the skies. . .

 

The concept of "sampling" which we tend to use is at least roughly based on the Nyquist Theorem.  I think Starizona gives one of the best explanations of this theorem:  https://starizona.co...harold-nyquist/  There are some people who swear that the Nyquist Theorem is the end-all and be-all and must dictate where you go.  I think of the theorem as being worth keeping in mind as a ROT (Rule-Of-Thumb) but we should feel free to range outside its dictates.  I'm one of those who believes that the Nyquist Theorem is technically inappropriate to astrophotography but that it is still a useful ROT with which to work.

 

The net effect is that we tend to think of needing a "box" of 2x2 or 3x3 pixels in the camera which is devoted to imaging each hypothetically pinpoint star.  With fewer pixels you end up with technically unnecessarily blocky and/or smeared stars/details.  This is under-sampling because you are using too few pixels to "sample" each star.

 

If you use more pixels than is strictly necessary in order to "sample" each star you also degrade your image.  This is because each and every time each pixel is "read" there is associated "noise".  This noise increases statistical uncertainty as to what is signal and what is not.

 

So if you used a 4x4 block of pixels to image/sample a star instead of just a 2x2 block of pixels?  Well, this would mean you used 4x4=16 pixels to image the star instead of 2x2=4 pixels.  Since 16/4=4, you used 4 times as many pixels to sample/image the star and that means 4 times as much read noise.  If 2x2 pixels would have been enough, then 4x4 pixels means an unnecessary 4-fold increase in noise.

 

Since one can reasonably construe AP as being almost solely about developing a great SNR (remember that means Signal to Noise Ratio), unnecessary noise is something to avoid and that means over-sampling should be avoided.

 

Calculate your sampling by doing the following:  203x(pixel size in microns)/(focal length of the OTA in millimeters).  So if you are using a camera with 4.63 micron pixels and an OTA with a 2000mm focal length?  203x4.63/2000=0.47APP.

 

Simple, right?  Well, it turns out that the reality is messy which is why you shouldn't necessarily get too excited about this under a lot of conditions.

 

  1. Assuming that the Nyquist Theorem is roughly applicable (not a bad assumption even if not perfect), you have to remember that the stars tend to twinkle.  That's because we're getting refraction from atmospheric turbulence which among other things is actually changing the apparent position of the star in the heavens.  When you are doing a 20-minute sub-exposure this means that the star's light is getting spread around a bit.  That alone will tend to make the star appear to be something other than pinpoint.  So we have to consider the "seeing" in our location which is probably closer to 1.5-2 arc-seconds for most of us - and means that we should expect our stars to appear to have an apparent diameter at the focal plane of our OTA of 1.5-2 arc-seconds.
  2. Even if a target such as that jet is only 1 arc-second wide it doesn't mean that you cannot image it if your seeing and/or your sampling is a bit worse than 1 arc-second, You may still be able to tell that the feature is there but it won't be just 1 arc-second and will thus be an inaccurate portrayal of the target feature.  "Inaccurate" does not necessarily mean "bad" when you are trying to make a pretty picture or are just trying to detect an object.
  3. Even if you have your sampling just right for the OTA, camera, and conditions you may be sabotaged by your mount.  If your mount is jerking around over a 20-minute sub then your mount will be distorting your star's shape and size over that sub-exposure.  Fortunately, most of us in this sub-forum are reducing our exposure to this problem by doing relatively short exposures.
  4. Even if everything else is done perfectly, the processing may turn out to be an issue.  It may be that the computer processing algorithms are tending to spread out your stars - there is some discussion about this.  And even if you aren't having an effective increase in APP of the stars during post-processing, it turns out that because of the way in which a file format such as TIFF handles the data you end up with data smeared out a bit (FITS doesn't do that).  If you believe the processing is an issue then over-sampling may be helpful.
  5. If your OTA doesn't have great optics then the star's light may be aberrated at the focal plane and this will tend to make the star occupy more pixels.
  6. If your display won't display all the pixels you are trying to see, then there may be limited value to proper sampling.  So let's say you are trying to display an un-zoomed 4K image of your target on a 640x480 monitor you aren't going to see much detail anyway and you could be grossly under-sampled without ever being able to tell the difference.  If you have a great 4K image with great sampling being displayed on a 4K display which is 20 feet away from you - you won't see the finer details anyway and you shouldn't be bothered.  This forum limits the size of the image you can display which means that you can only show limited detail if you aren't showing an un-zoomed portion of that big, beautiful image (but you can link to a larger image so this really isn't a big deal).
  7. If your camera is built around a modern low-noise CMOS sensor, your read noise may be so low that even major over-sampling may add very little to the overall noise level of the image.  So the SNR hit from over-sampling may be negligible.

Some other things to think about?

 

Planetary AP is all about using lucky imaging at long focal lengths and with the system clearly considered to be over-sampled.  It actually works pretty well with our modern CMOS sensors. . .

 

CMOSImager is being developed by CygnusBob and I believe will someday be bundled into Kstar:  https://www.cloudyni...1/#entry8918799  The idea is to get very sharp images through the use of very short exposures and very precise autoguiding and processing.  It is not really very fast imaging as it stands right now but with lots of computing horsepower and bandwidth this could some day be of interest to us.  Right now it is an Apple computer project and I cannot try it out.

 

If one considers the fact that over-sampling with a modern CMOS sensor has little impact on the SNR, one might think that there is no down-side to over-sampling.  This is not necessarily the case depending on your goals.

 

So let's assume you were using the Hyperstarred 8" SCT with an IMX183 camera?  Even if it gives you sampling which you find to be quite good, you are also talking about a whole lot of data to process.  I can remember someone did a really nice image of M1 (IIRC) using hundreds of short sub-exposures.  It took several days for the computer to get through all the stacking.  The point being that a huge amount of data means a huge amount of storage space and a huge amount of time processing.  That wouldn't mean you couldn't do OAP (Observational AP) of a target with the IMX183 and the Hyperstarred 8" SCT, but you might want to locate the target and then define a small ROI (Region of Interest) and thus collect much less data to process.

 

One other thing to keep in mind although it doesn't apply too strongly to what most of us do.  Those who are doing CAP (Conventional AP) will sometimes change their sampling in the process of their LRGB imaging.  They may get their luminance with lots of sampling in order to get their detail.  But then for the color (RGB) they may bin the system with reduced sampling because putting in the color just doesn't need as much detail.  The key for us is that for some things we just don't need that much detail.

 

So yes, there is a lot going on with sampling.  Avoiding under-sampling and over-sampling is an appropriate goal but sometimes it is difficult to sort out exactly what is over-sampling or under-sampling for a given situation.  Nyquist gives us a good ROT to use but we shouldn't be too concerned about staying strictly within the typical constraints it would seem to impose.


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#9 OleCuss

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Posted 28 April 2019 - 05:29 PM

I forgot to mention an obviously important detail.

 

By the ROT we tend to aim for a calculated APP which is in the range of 1/3 to 1/2 of the "seeing".


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#10 Astrojedi

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Posted 29 April 2019 - 09:58 AM

In my experience the Hyperstar is best suited to observing large diffuse objects such as nebulae which benefit the most from a fast focal ratio. Small bright objects like the M87 jet, planetaries etc. need high resolution and do well with slower focal ratios also.

 

The HS is not suited for high resolution imaging for a few reasons:

1. Image scale i.e. arcseconds / pixel - you need oversampling for high resolution imaging

2. Fast focal ratio can saturate pixels very fast for such bright objects if you are not careful

3. Very sensitive to collimation at F2

4. Not diffraction limited

5. Diffraction from wires other surfaces increases light scatter


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#11 saguaro

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Posted 29 April 2019 - 11:01 AM

I was able to see the jet by zooming in on it with SharpCap. I used my 8-inch SCT @F/4 (Meade 3.3 focal reducer) with 385MC camera and Evolution Alt-Az mount, and SharpCap Pro live stacking with master dark. I used Gain 300, and 30 frames at 10 seconds each. Pixel scale is .9 arcsec/pixel. Here is the zoomed and cropped image:

 

M87-and-jet.jpg


Edited by saguaro, 29 April 2019 - 11:13 AM.

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#12 descott12

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Posted 29 April 2019 - 11:11 AM

I was able to see the jet by zooming in on it with SharpCap. I used my 8-inch SCT @F/4 (Meade 3.3 focal reducer) with 385MC camera, and SharpCap Pro live stacking with master dark. I used Gain 300, and 30 frames at 10 seconds each. Pixel scale is .9 arcsec/pixel. Here is the zoomed and cropped image:

 

attachicon.gif M87-and-jet.jpg

Very nice view. The jet is very well-defined. With your dark skies and the correct pixel scale, I am not surprised. I am going to try again with a different camera in the next few days.


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#13 DSO_Viewer

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Posted 29 April 2019 - 11:57 AM

At F/2 you are grossly under-sampled with that camera.  There will be a lot of detail missed because of that under-sampling but if you aren't looking for the fine details you may never notice.

 

At F/10 you are over-sampled which means you have a little more read noise than is idea but with a low-noise sensor like the IMX294 it likely isn't enough noise to be noticeable.

 

Congrats on a nice image at F/10!

 

Note that the short focal length is not why it is not seen.  Your potential resolution of the OTA is determined by the aperture, not by the focal length.  But, as noted, under-sampling will decrease the potential resolution of the OTA/camera combination.

 

If you were to use an IMX183 (which has much smaller pixels) at F/2 you might see the jet.

Sorry, I am just a newby at this and my suggestion was wrong by suggesting it was possible the focal length. When I mentioned focal length, I obviously know that aperture determines the focal length. I will just leave the advice and sit back on the sideline and have CN experts like yourself to provide the help.

 

Steve  


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#14 mclewis1

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Posted 29 April 2019 - 12:47 PM

Steve, You weren't wrong. Many of us reading your post also assumed the same aperture scope.


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#15 OleCuss

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Posted 29 April 2019 - 01:31 PM

Sorry, I am just a newby at this and my suggestion was wrong by suggesting it was possible the focal length. When I mentioned focal length, I obviously know that aperture determines the focal length. I will just leave the advice and sit back on the sideline and have CN experts like yourself to provide the help.

 

Steve  

Sometimes getting it wrong and being corrected is how we learn.

 

I've certainly made many mistakes and I'm sure I will do so many times in the future.  Even when I make mistakes it can be helpful to others because when someone corrects me, they are also correcting those who are making the same mistakes.

 

So I'd recommend you not stop.  Some of us may be jerks at times but pay no heed to those inclined to abuse you.  Just keep on keeping on and learn and help others both through your triumphs and your mistakes!

 

And yes, when you know both your aperture and your focal ratio you then know your focal length.

 

And yes, assuming good optics, the sole optical factor which determines the potential resolution is the aperture and nothing else.  But when you start hooking up cameras for imaging it gets much more complicated. . .

 

Tiny pixels tend to be associated with more read noise per pixel and less dynamic range.  These limitations mean that we tend not to have great interest in the shortest of focal lengths if we are trying to get great sampling.  The sensor limitations might give poor SNR and dynamic range making imaging difficult even if you could technically capture all the detail which is available if you were operating with the same aperture but a much longer focal length.

 

Our systems may be pretty good, but they are never ideal!



#16 descott12

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Posted 29 April 2019 - 10:00 PM

Cloudy, soupy sky but I tried capturing the jet with my mono 178 at F2 using Hyperstar. This combo had a more favorable image scale and I was able to capture it...just barely. However, I am amazed at how well the 178 did with fine details on other objects such as the Mark chain and M101.  I always just assumed my 294 MC PRO was "the best" camera but it really proves that there is no best camera and you have to match your camera to your optics and your target.

 

EDIT: SharpCap Exp 11.5 seconds, Gain 316, Total exposure: 2:51 minutes. No flats or darks

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#17 GaryShaw

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Posted 01 May 2019 - 09:42 AM

Hi Dave

Thanks for posting the image - it is really impressive to see, especially now understanding what it is and its importance in verifying general relativity.

 

I’m just beginning EAA and hope you’ll forgive a few naive questions:

 

1. Is the 11.5 sec exposure the ‘sub’ exposure and the 2:51 (2 hours, 51 minutes) the total of stacked 11.5 second exposures? 

2. I have a 5.5” Schmidt Newtonian F/3.6, and just started running a 294mc camera. Does your experience suggest I’d be better off with a .5 reducer getting me down to F/1.8 in trying to capture the jet. Also, I’m on an AZ mount so 11.5 seconds might be stretching it a bit on exposure so I’d probably want to drop the sub exposure time and go for longer overall integration time. Does that make sense?

3. If I could run at F/3.6 without the reducer, I’d have a larger image of M87. Would this help in seeing the jet, especially with some zoom within Sharpcap?

 

Any thoughts or suggestions would be welcome. I’ve been following the M87 saga pretty closely since watching the NSF News conference announcing the Horizon Team’s image of the black hole.

cheers,

Gary



#18 descott12

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Posted 01 May 2019 - 09:51 AM

 

Hi Gary, 

 

1. Is the 11.5 sec exposure the ‘sub’ exposure and the 2:51 (2 hours, 51 minutes) the total of stacked 11.5 second exposures? 

>> yes 11.5 second sub exposure but the total is 2 MINUTES, 51 seconds. Not 2 hours. EAA is all about really quick stacks. Usually around 3- 5 minutes or less. I sometimes run for 10-15 minutes to pull out some detail but usually not.

 

2. I have a 5.5” Schmidt Newtonian F/3.6, and just started running a 294mc camera. Does your experience suggest I’d be better off with a .5 reducer getting me down to F/1.8 in trying to capture the jet. Also, I’m on an AZ mount so 11.5 seconds might be stretching it a bit on exposure so I’d probably want to drop the sub exposure time and go for longer overall integration time. Does that make sense? 

>> The big thing that I learned in this thread is that image scale really is important. With my ASI 294 at F2 on my Evo 8, the image scale was too large to capture this fine detail.  I think the faster f ratio is always a huge help so I always do EAA at f2 but the image scale is also very important. The second picture I posted was with a 178 MM which had a more favorable image scale and I was able to capture the jet at f2 with this camera, but not with the 294. The 178 MM is also monochrome, so I think that helped alot. In fact, I will probably start using this camera ALOT more for galaxies which are mostly monochrome anyway.

 

Regarding your scope: f3.6 is already very fast - try it and see what you get. 

 

 



#19 OleCuss

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Posted 01 May 2019 - 10:04 AM

The Comet Catcher has a nominal focal length of 510mm (it will vary a bit with that sled focuser).  With the ASI294 you are under-sampled.  Using a focal reducer will worsen the under-sampling (and your vignetting).

 

Another thing to remember is that you could have your OTA at the right rotation so that the heavy diffraction spike could coincide with the jet (but your probability of not having that happen is fairly good).

 

If you want a good probability of seeing the jet with your focal length, the best thing to do it would be to get a camera with much smaller pixels.  This, however is a rather expensive thing to do for a single target.

 

I would be interested in seeing what you could get, however, if you used a Barlow with the Comet Catcher and that camera.  Increasing the effective focal length would seem logically to reduce the under-sampling and might get you something useful.  I'd be a little worried about it, however, because that sled focuser is not (IMHO) the most robust of systems. . .

 
 
 

Edited by OleCuss, 01 May 2019 - 10:16 AM.


#20 cshine

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Posted 01 May 2019 - 10:43 AM

This is a very interesting target and I've included it in the May Challenge to see how much jet detail we can tease out. Astrojedi and others have set the bar pretty high already. Hopefully this will be a fun and educational group exercise. 


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#21 GaryShaw

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Posted 01 May 2019 - 12:04 PM

 

The Comet Catcher has a nominal focal length of 510mm (it will vary a bit with that sled focuser).  With the ASI294 you are under-sampled.  Using a focal reducer will worsen the under-sampling (and your vignetting).

 

Another thing to remember is that you could have your OTA at the right rotation so that the heavy diffraction spike could coincide with the jet (but your probability of not having that happen is fairly good).

 

If you want a good probability of seeing the jet with your focal length, the best thing to do it would be to get a camera with much smaller pixels.  This, however is a rather expensive thing to do for a single target.

 

I would be interested in seeing what you could get, however, if you used a Barlow with the Comet Catcher and that camera.  Increasing the effective focal length would seem logically to reduce the under-sampling and might get you something useful.  I'd be a little worried about it, however, because that sled focuser is not (IMHO) the most robust of systems. . .

 
 
 

 

Hi OleCuss:

 

Thank you for your insights.

 

I wish there were a way to readily determine the likelihood of over/under sampling in a given scope/camera scenario - similar to the way some quick math determines FOV and image scale (resolution) based on sensor and pixel sizes factored in with scope focal length. I read all the above on sampling and I guess I need to read it a few hundred more times to grasp it in a useful way.

 

My CC has the sled fixed in about the midpoint of its travel and I'm using a SvBony helical focuser which is a vast improvement. I'm thinking the diffraction spikes are an even less likely issue since the CC's secondary is suspended directly from the sled focuser and there's only 1 secondary mirror support.

 

If we ever see the night sky again here, I'll be giving M87 a try and will test your barlow suggestion. Given the CC and 294 combination results in 1.9 a-s/pixel, a 2x barlow would effectively reduce that to about .95-1.0 a-s/pixel.  Someone above said the jet was 1 a-s wide so....maybe with a barlow, it could nearly resolve the jet.

 

I was intrigued by Dave's comment about imaging galaxies with a monochrome camera with smaller pixels. Any opinion on whether the 178 would be a decent match for the CC? Its sensor is smaller than the 294 but it's pixels are almost half that of the 294 - similar effect of the .5 barlow without the photon loss of the barlow.

 

BTW, JGraham has pointed out that his CC and the 294 are a perfect match and I've been amazed by the images he's captured with it. It would be great to find another 'perfect match' camera with a smaller pixel size.

 

Cheers!

Gary



#22 OleCuss

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Posted 01 May 2019 - 03:01 PM

I would contend that there is no perfect match between OTA and camera.  There is always a compromise being made and the key is to make the compromise which best suits your purposes.

 

How you want to observe, what you want to observe, your skill level, your mount, your seeing conditions, your monitor, your viewing distance, your budget. . .  All of those things in addition to the characteristics of your OTA and camera are important.

 

One camera may be the best compromise for everything and then you change your target and a different camera might be better.

 

But the IMX294 cameras make a whole lot of people very happy on a lot of targets with a substantial variety of equipment.

 

 

And yes, if I still had a Comet Catcher and decided I wanted to image with it, I think that the IMX178 cameras would be contenders for the position on the focuser.  But I'd also be considering the IMX183 cameras  which may be a little better in some ways and a little worse in others.

 

Yup!  One diffraction spike with the Comet Catcher.  So you don't have spikes you have one very fat diffraction spike (singular).  This is no problem for some, but some individuals have found that sufficiently objectionable to move them to put one or more items across the corrector plate to make more diffraction spikes.  That is more pleasing for some and doesn't look as much like an aberration.

 

FWIW!



#23 GaryShaw

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Posted 01 May 2019 - 03:16 PM

Thanks again OleCuss:

 

I added a single bar across my corrector plate after seeing that JGraham did that in order to get nice 4 directional spikes...It works!

 

See the attached cropped and zoomed in image of Spica:

 

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  • Spica_zoomed and cropped.png

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#24 GaryShaw

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Posted 01 May 2019 - 03:29 PM

Here's a link to John's Comet Catcher information and thoughts about the scope:

 

https://www.cloudyni...e/#entry9322841



#25 adg

adg

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Posted 16 May 2019 - 04:24 PM

This thread is extremely interesting to me as a newcomer to CN!

 

 

I am a visual (eyepiece) observer with an old achromatic refractor, currently planning to invest $$$ to switch to EAA.

 

 

My planned gear/setup for EAA:  An 80mm f/6 ED apo refractor and a ZWO ASI 294MC Pro camera (plus a good EQ mount for going on to AP in the future as well; I will make a separate "equipment advice" post about this).

 

 

My planned gear above is meant mostly for wider field deep sky (FOV 2.3 x 1.6 degs, image scale 2 arc secs per pixel), but it would be great to have something that can also detect the M87 jet.  Dave's results in this thread show that my planned setup will not be able to show the M87 jet.

 

 

But I still wonder:  Can the M87 jet can be detected through an 80mm f/6 scope if I use a finer pixel camera such as the ASI 178MM, as done by Dave?  (ASI 178MM camera + 80mm f/6 scope --> image scale = 1 arc sec per pixel.)

 

 

Main question:  Can the M87 jet be detected in an EAA setup with a 80mm f/6 scope and a sufficiently fine-pixel CMOS camera?

 

 

However, I am afraid that aperture may be an issue (as noted by OleCuss).  The resolving power of an 80mm aperture is 1.5 arc secs (theoretical best), while for Dave's 200mm scope it is 0.6 arc sec.

 

 

If the M87 jet is only 1 arc sec wide, may be an 80mm scope is simply unable to detect the jet, even under the best conditions?  Or may be the "diffraction spread" may make it easier to detect the jet?  As this is a very close situation, perhaps the most likely answer is that seeing conditions will determine if the jet can be detected?

 

 

I understand that the "proper" solution for viewing the M87 jet is a bigger scope.  But (in the spirit of this thread) it would be nice to know more about some exact optimal EAA gear combinations that can just detect the jet, at least under good conditions.

 

 

Also, knowing the answer will help me choose my initial EAA gear.


Edited by adg, 16 May 2019 - 11:09 PM.



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