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Attempting Ceres with 8" Newt?

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#1 ImaLibra

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Posted 22 November 2017 - 11:45 PM

Hi all,

 

I bought a Zambuto 8" quartz F7 mirror because I am planning to shoot for Ceres this Jan-Feb. Ceres is in a prime position for me, and it won't be this good again for a loooong time, as far as I know from astronomical simulators. This Jan-Feb it will be passing the closest to earth with a maximum size of .86" and magnitude of 7 or something like that. Oh, and most importantly, it is very close to the zenith where I am (83 degrees or higher).

 

I have all the supplies needed to build the Newt OTA, but I have to work double-time to get it done on schedule....

 

The reason I bought the 8" mirror was that I understand, from reading, that even a small aperture scope can be quite powerful if the glass is good. I heard that if optics are medium or lower quality (mass-produced mirrors) then your image will be blurred, regardless of aperture size. Mass-produced IS good overall, but it's not as accurate, and you can get a dud. If the mirror isn't directing light properly, what's the point? I figured I would turn the 8" into my main astrophotography scope, since that is my passion. I figured, "why not try and build a scope that can do DSO (F7 is perfect for my DSO goals) AND even get the smaller planets? Basically, one scope to do it all. I'm sure i'm going to get an earful for saying thatlol.gif  Also, my mount can't handle anything over 10" aperture, weight-wise (EQ6R-Pro).

 

Anyway, I wanted to ask some of you more experienced imagers: What do you think I can expect? Need to clarify: I am NOT expecting to resolve any craters or anything like that. I don't even think that's possible with a 16", is it? That's another reason I avoided larger aperture...yeah, it gathers more light and resolution, but I just can't believe that those 8 extra inches would be enough to resolve craters on a sub-arcsecond object, especially with "okay" optics, right? 

 

Here is my main goal: An image of Ceres with very clean, sharp borders, not fuzzy or squared (pixellated) borders. Was planning on a MC camera with 2.4 micrometer pixel size. I just want an image with the least amount of blur. Do you think it is possible with 8"?


Edited by ImaLibra, 23 November 2017 - 12:22 AM.


#2 17.5Dob

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Posted 23 November 2017 - 12:22 AM

4"/ 8"/ 14" / 24" it's still only going to be dot, not a disk.

Just use a  50mm camera lens and call it good. It will look the same as one through the 8"



#3 ImaLibra

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Posted 23 November 2017 - 12:27 AM

4"/ 8"/ 14" / 24" it's still only going to be dot, not a disk.

Just use a  50mm camera lens and call it good. It will look the same as one through the 8"

I know what you mean, I know it is very small, but when I think of it as a dot I think just 4 pixels or something, like an individual star in a wide-field shot. However, I am pretty sure it is possible to get it bigger than that with a powemate.



#4 AstroBobo

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Posted 23 November 2017 - 12:54 AM

CN members here are making heroic efforts resolving a high contrast detail on Neptune with 12"+ telescopes and years of experience. I think you should start with Saturn and Jupiter first. Also see current Mars images and look for craters on a 5" size disk grin.gif


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#5 einarin

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Posted 23 November 2017 - 04:23 AM

I agree what others have said.

Here's one taken with C11 @ f/30:

https://www.britastro.org/node/1254


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#6 ImaLibra

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Posted 23 November 2017 - 09:44 AM

CN members here are making heroic efforts resolving a high contrast detail on Neptune with 12"+ telescopes and years of experience. I think you should start with Saturn and Jupiter first. Also see current Mars images and look for craters on a 5" size disk grin.gif

I have to say: It doesn’t matter how many people try to image Neptune. If they are living in a place where Neptune only gets 40 or 50 degrees above the horizon, there is little chance of getting a good image. That’s why I emphasized the zenith, because atmosphere will ruin any chance of a good image. At least the zenith gives the best odds. Also, I’ve successfully imaged Jupiter and Saturn only using manual knobs on a telescope.



#7 ImaLibra

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Posted 23 November 2017 - 09:45 AM

I agree what others have said.

Here's one taken with C11 @ f/30:

https://www.britastro.org/node/1254

Thanks so much for the link! It’s great to be able to see other attempts and have an idea of what to expect.



#8 happylimpet

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Posted 23 November 2017 - 09:50 AM

 

CN members here are making heroic efforts resolving a high contrast detail on Neptune with 12"+ telescopes and years of experience. I think you should start with Saturn and Jupiter first. Also see current Mars images and look for craters on a 5" size disk grin.gif

I have to say: It doesn’t matter how many people try to image Neptune. If they are living in a place where Neptune only gets 40 or 50 degrees above the horizon, there is little chance of getting a good image. That’s why I emphasized the zenith, because atmosphere will ruin any chance of a good image. At least the zenith gives the best odds. Also, I’ve successfully imaged Jupiter and Saturn only using manual knobs on a telescope.

 

Neptune at 28-29degrees altitude.

 

2017-08-06-0215_6-NJH-All-LD0,50-insane gamma_deconv.png

 

Yes, the zenith gives the best odds, but dont rule out lower altitudes.  Also, this was taken with a commercial skywatcher 300p (12"), costing £250 (Second hand). There are a few misconceptions floating around here.


Edited by happylimpet, 23 November 2017 - 09:50 AM.

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#9 ImaLibra

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Posted 23 November 2017 - 10:00 AM

I have an idea

 

I think i know a good way to test my telescope’s abilities.

 

Does anybody know of a double star with a .6 arcsec separation, or how to go about finding that information?

 

There is an article on Starizona that talks about limits of aperture and resolution, and I know that the author states that he had indeed been able to clearly separate a double star with a .6 arcsec distance with a 6" telescope. That would be the perfect trial.


Edited by ImaLibra, 23 November 2017 - 02:24 PM.


#10 ImaLibra

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Posted 23 November 2017 - 10:03 AM

 

 

CN members here are making heroic efforts resolving a high contrast detail on Neptune with 12"+ telescopes and years of experience. I think you should start with Saturn and Jupiter first. Also see current Mars images and look for craters on a 5" size disk grin.gif

I have to say: It doesn’t matter how many people try to image Neptune. If they are living in a place where Neptune only gets 40 or 50 degrees above the horizon, there is little chance of getting a good image. That’s why I emphasized the zenith, because atmosphere will ruin any chance of a good image. At least the zenith gives the best odds. Also, I’ve successfully imaged Jupiter and Saturn only using manual knobs on a telescope.

 

Neptune at 28-29degrees altitude.

 

attachicon.gif2017-08-06-0215_6-NJH-All-LD0,50-insane gamma_deconv.png

 

Yes, the zenith gives the best odds, but dont rule out lower altitudes.  Also, this was taken with a commercial skywatcher 300p (12"), costing £250 (Second hand). There are a few misconceptions floating around here.

 

Well, after seeing your post, I stand corrected grin.gif

 

That’s a very nice image for being so low in the sky. 

 

Happylimpet, regarding misconceptions, do you think it is possible to resolve Ceres, however small, into a very tiny disk with 8” and very good optics?


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#11 RedLionNJ

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Posted 23 November 2017 - 10:30 AM

The best (or one of the best) ways to demonstrate "resolution" of an object like Ceres (0.75 arcsec diameter and mag 7.2 in February) would be to take an approach similar to John's (linked above). Personally, I find John's result to be quite unconvincing for 2 reasons - the comparison star (Denebola) looks more like a streak than a point (or very small disk, due to wavelength and aperture limitations) AND it's significantly brighter than Ceres.

 

To emulate in a more convincing manner, I would wait for a period of very good seeing, then pick a nearby star of about the same magnitude (7-ish) and capture both Ceres and the star separately, but process identically. I would HOPE the resulting image shows a perfectly round Ceres somewhat larger than the perfectly round comparison star.  

 

Excellent seeing is far more of a factor than low or high elevation (although good seeing does appear to materialize more often at higher elevations).

 

Note Ceres will be around half the apparent diameter of Jupiter's Ganymede and only a little smaller than Io. Practice resolving detail on those, first. If you can produce detail from any of Jupiter's Galilean satellites, resolving Ceres should be easy.  But I still wouldn't be expecting much other than a tiny disk a little larger than a star of comparable brightness.

 

Good luck - and share the results!


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#12 happylimpet

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Posted 23 November 2017 - 10:38 AM

 

 

 

CN members here are making heroic efforts resolving a high contrast detail on Neptune with 12"+ telescopes and years of experience. I think you should start with Saturn and Jupiter first. Also see current Mars images and look for craters on a 5" size disk grin.gif

I have to say: It doesn’t matter how many people try to image Neptune. If they are living in a place where Neptune only gets 40 or 50 degrees above the horizon, there is little chance of getting a good image. That’s why I emphasized the zenith, because atmosphere will ruin any chance of a good image. At least the zenith gives the best odds. Also, I’ve successfully imaged Jupiter and Saturn only using manual knobs on a telescope.

 

Neptune at 28-29degrees altitude.

 

attachicon.gif2017-08-06-0215_6-NJH-All-LD0,50-insane gamma_deconv.png

 

Yes, the zenith gives the best odds, but dont rule out lower altitudes.  Also, this was taken with a commercial skywatcher 300p (12"), costing £250 (Second hand). There are a few misconceptions floating around here.

 

Well, after seeing your post, I stand corrected grin.gif

 

That’s a very nice image for being so low in the sky. 

 

Happylimpet, regarding misconceptions, do you think it is possible to resolve Ceres, however small, into a very tiny disk with 8” and very good optics?

 

 In truth, I couldnt say. It will be marginal! Probably just about, yes.

 

I would strongly advise a slightly larger aperture to considerably improve your results. Note that contrast wouldnt be super critical for this (ie Zambuto optics etc), youre simply trying to detect the size of the disc, so even a lesser quality optic should be fine as the post-processing can enhance the fine structure in your result even if a 'wash' of lower contrast exists. I would have said your best chance would be with a bigger, cheaper OTA. Note also that people have successfully used my scope (the 300p) on an EQ6, but its certainly pushing the limits.

 

Im quite sold on John S's Ceres results. I hope to repproduce them in due course.

 

And on that note, thanks ImaLibra for flagging this up! Hope its a northerly declination..... also, thanks for giving me an excuse to share my Neptune image!


Edited by happylimpet, 23 November 2017 - 10:40 AM.


#13 RedLionNJ

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Posted 23 November 2017 - 11:06 AM

For those who may not have looked ahead to next year's interesting oppositions - Ceres will be at approx Dec +30 and mag 6.9 at the end of January. Good times!


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#14 Mirzam

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Posted 23 November 2017 - 08:01 PM

Ceres will appear much like Europa, albeit somewhat dimmer and redder.  I was able to visually discern Ceres’ disc without difficulty at opposition with an 8” refractor.  I’m thinking that you should be able to get a disc, but no surface details with your proposed aperture.  Ceres’ surface does not have high contrast features, except for the very tiny white spots discovered by the Dawn mission. Even a much larger aperture is unlikely to reveal surface detail, although I’d love to see some amateurs try anyway.

 

JimC


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#15 ImaLibra

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Posted 23 November 2017 - 08:11 PM

 

 

 

 

CN members here are making heroic efforts resolving a high contrast detail on Neptune with 12"+ telescopes and years of experience. I think you should start with Saturn and Jupiter first. Also see current Mars images and look for craters on a 5" size disk grin.gif

I have to say: It doesn’t matter how many people try to image Neptune. If they are living in a place where Neptune only gets 40 or 50 degrees above the horizon, there is little chance of getting a good image. That’s why I emphasized the zenith, because atmosphere will ruin any chance of a good image. At least the zenith gives the best odds. Also, I’ve successfully imaged Jupiter and Saturn only using manual knobs on a telescope.

 

Neptune at 28-29degrees altitude.

 

attachicon.gif2017-08-06-0215_6-NJH-All-LD0,50-insane gamma_deconv.png

 

Yes, the zenith gives the best odds, but dont rule out lower altitudes.  Also, this was taken with a commercial skywatcher 300p (12"), costing £250 (Second hand). There are a few misconceptions floating around here.

 

Well, after seeing your post, I stand corrected grin.gif

 

That’s a very nice image for being so low in the sky. 

 

Happylimpet, regarding misconceptions, do you think it is possible to resolve Ceres, however small, into a very tiny disk with 8” and very good optics?

 

 In truth, I couldnt say. It will be marginal! Probably just about, yes.

 

I would strongly advise a slightly larger aperture to considerably improve your results. Note that contrast wouldnt be super critical for this (ie Zambuto optics etc), youre simply trying to detect the size of the disc, so even a lesser quality optic should be fine as the post-processing can enhance the fine structure in your result even if a 'wash' of lower contrast exists. I would have said your best chance would be with a bigger, cheaper OTA. Note also that people have successfully used my scope (the 300p) on an EQ6, but its certainly pushing the limits.

 

Im quite sold on John S's Ceres results. I hope to repproduce them in due course.

 

And on that note, thanks ImaLibra for flagging this up! Hope its a northerly declination..... also, thanks for giving me an excuse to share my Neptune image!

 

 

 

The best (or one of the best) ways to demonstrate "resolution" of an object like Ceres (0.75 arcsec diameter and mag 7.2 in February) would be to take an approach similar to John's (linked above). Personally, I find John's result to be quite unconvincing for 2 reasons - the comparison star (Denebola) looks more like a streak than a point (or very small disk, due to wavelength and aperture limitations) AND it's significantly brighter than Ceres.

 

To emulate in a more convincing manner, I would wait for a period of very good seeing, then pick a nearby star of about the same magnitude (7-ish) and capture both Ceres and the star separately, but process identically. I would HOPE the resulting image shows a perfectly round Ceres somewhat larger than the perfectly round comparison star.  

 

Excellent seeing is far more of a factor than low or high elevation (although good seeing does appear to materialize more often at higher elevations).

 

Note Ceres will be around half the apparent diameter of Jupiter's Ganymede and only a little smaller than Io. Practice resolving detail on those, first. If you can produce detail from any of Jupiter's Galilean satellites, resolving Ceres should be easy.  But I still wouldn't be expecting much other than a tiny disk a little larger than a star of comparable brightness.

 

Good luck - and share the results!

 

So I was thinking a bit more about planetary imaging... it is something I would definitely like to do, and I believe that large apertures are required. After more reading, I also don’t think I will be able to complete my Newtonian in time. I am one of the least technical people on here, so I don’t think that it will be possible...

 

I had a thought: I have already captured planets using hand-knobs and no motors. I find the path, lead the planet, let it drift, and lead it again, etc. I could also take still frames. Would a 16” dob be able to successfully operate sitting on a 35 degree angle wedge? How would the bearings take it? I was looking at a Meade Lightbridge. Is that considered cheap? $2k for 16”? I imagine it is a very heavy set-up. However, I thought of the other option: Would a Hubble Optics 16” work? I think it is 60 lbs in total. But, would the super-lightweight truss design have flexure issues? Would really appreciate the help. At the moment I have no OTA to image with.



#16 Bart Declercq

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Posted 24 November 2017 - 02:46 AM

Ceres should be easy enough to resolve using an 8" telescope, but you will need to take a reference image of a nearby star of similar magnitude (and preferably a reddish star, as that will more closely match Ceres's color) to confirm that you did.

 

For reference, in 2010 I managed to (barely) resolve Vesta using a 12" telescope - https://www.cloudyni...d-in-12-newton/ - in a way, Vesta is easier since it is not perfectly spherical, but it's significantly smaller, so you do need a bigger scope, an 8" wouldn't be able to.

 

I don't have the images lying around, but I did resolve Ceres way back when (around 2008-2009 I think) using a C9.25 SCT



#17 RedLionNJ

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Posted 24 November 2017 - 10:38 AM

> "I had a thought: I have already captured planets using hand-knobs and no motors. I find the path, lead the planet, let it drift, and lead it again, etc. I could also take still frames. Would a 16” dob be able to successfully operate sitting on a 35 degree angle wedge? How would the bearings take it? I was looking at a Meade Lightbridge. Is that considered cheap? $2k for 16”? I imagine it is a very heavy set-up. However, I thought of the other option: Would a Hubble Optics 16” work? I think it is 60 lbs in total. But, would the super-lightweight truss design have flexure issues? Would really appreciate the help. At the moment I have no OTA to image with."

 

I really wouldn't recommend a 35-degree wedge for this purpose. A Poncet-style platform would have much less tilt to it, but still allow for push-tracking in one dimension (RA) for a few minutes at a time. I haven't looked personally, but there must be an online calculator somewhere to guide you in relative dimensions for the important parts.  If you're not going to motorize it, it should be a fairly simple weekend project.

 



#18 Cotts

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Posted 24 November 2017 - 11:44 AM

Hi all,

 

I bought a Zambuto 8" quartz F7 mirror because I am planning to shoot for Ceres this Jan-Feb. Ceres is in a prime position for me, and it won't be this good again for a loooong time, as far as I know from astronomical simulators. This Jan-Feb it will be passing the closest to earth with a maximum size of .86" and magnitude of 7 or something like that. Oh, and most importantly, it is very close to the zenith where I am (83 degrees or higher).

 

I have all the supplies needed to build the Newt OTA, but I have to work double-time to get it done on schedule....

 

The reason I bought the 8" mirror was that I understand, from reading, that even a small aperture scope can be quite powerful if the glass is good. I heard that if optics are medium or lower quality (mass-produced mirrors) then your image will be blurred, regardless of aperture size. Mass-produced IS good overall, but it's not as accurate, and you can get a dud. If the mirror isn't directing light properly, what's the point? I figured I would turn the 8" into my main astrophotography scope, since that is my passion. I figured, "why not try and build a scope that can do DSO (F7 is perfect for my DSO goals) AND even get the smaller planets? Basically, one scope to do it all. I'm sure i'm going to get an earful for saying thatlol.gif  Also, my mount can't handle anything over 10" aperture, weight-wise (EQ6R-Pro).

 

Anyway, I wanted to ask some of you more experienced imagers: What do you think I can expect? Need to clarify: I am NOT expecting to resolve any craters or anything like that. I don't even think that's possible with a 16", is it? That's another reason I avoided larger aperture...yeah, it gathers more light and resolution, but I just can't believe that those 8 extra inches would be enough to resolve craters on a sub-arcsecond object, especially with "okay" optics, right? 

 

Here is my main goal: An image of Ceres with very clean, sharp borders, not fuzzy or squared (pixellated) borders. Was planning on a MC camera with 2.4 micrometer pixel size. I just want an image with the least amount of blur. Do you think it is possible with 8"?

  (See image scale calculator here: http://celestialwond...eScaleCalc.html  ) 

 

The very best planetary imagers in the world (Peach, Go et al.) routinely work at image scales more like 0.1" per pixel or even 0.05" .....  The former requires a focal length of 5000mm..  For your 8" f/7  you would have to use a 3.5x or 4x barlow.  

 

This would be a very challenging project for your scope/mount combination...  As focal length increases all aspects of imaging - vibration, wind, flexure, really narrow fields of view etc. etc., become much more problematic....But this hobby has lots of folks who push the envelope with success.

 

I'm encouraging you to carry on but to temper your expectations.....  

 

Dave


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