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Jupiter fireball?

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#1 skyskan

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Posted 17 June 2019 - 11:21 PM

After upgrading my scope last year, I made serious effort to upgrade eyepieces and diagonal.  

 

I went out to my favorite site which is sitting above 2000 meters in a quite dry region.  The site is very dark and moon was not there.  Seeing was very good that day. 

 

I brought my LightSwitch 8" and took out ES  11mm/82 degree. 

 

I started observing Jupiter around 22:00 when it was still pretty low above horizon.  It was not perfect but I was able to see some details and it was pretty good.  I came back to Jupiter around 1:00 when it was hitting near the highest elevation of the day expecting really nice view.  But Jupiter turned into a giant fireball with very bright four moons.  It was just glowing whitish yellow disk with no detail at all.

 

I have made many trips to this place with my Celestron NexStar 130 SLT and never had this problem.  Well, all my eyepieces were from very inexpensive kit back then.

 

It felt like trying to read text on bright computer screen with fully dilated eye.  I even made a joke to a friend that I just discovered a white hole or witnessing the planet turning into a star.

 

What was I doing wrong here?   Should I use filters?



#2 scadvice

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Posted 17 June 2019 - 11:24 PM

Did you check for dew on the primary and or corrector? Even the ES?


Edited by scadvice, 17 June 2019 - 11:25 PM.

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#3 skyskan

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Posted 17 June 2019 - 11:30 PM

Did you check for dew on the primary and or corrector? Even the ES?

No, but I did not really have to.  When I went back to Albireo and M13 after fireball Jupiter, it was perfect and I was blown by the improvement of the image over the old eyepieces with old diagonal. 



#4 johnpd

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Posted 18 June 2019 - 12:30 AM

Jupiter is extremely bright now. When Mars, Jupiter, and Saturn are at opposition, it helps to have a filter to cut down the glare. I was using a 4" refractor and resorted to a .25 ND filter to really bring out the detail. Someone else mentioned in another thread that the full Moon can be affecting the view as well.

 

JohnD


Edited by johnpd, 18 June 2019 - 12:32 AM.

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#5 Asbytec

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Posted 21 June 2019 - 08:21 PM

 

I brought my LightSwitch 8" and took out ES  11mm/82 degree. 

 

...

 

It was just glowing whitish yellow disk with no detail at all.

 

...

 

What was I doing wrong here?   Should I use filters?

Jupiter is too bright because you are using too low magnification. At 2030mm focal length, your 11mm ES provides 185x (23x per inch) and ~1mm exit pupil. This is supposed to be near the best magnification for seeing detail, but this is not true. You can and probably need to, if seeing permits (and even if it doesn't), up to about 40x per inch and maybe more.

 

You should be closer to 320x and 0.6mm exit pupil for the best view. At this magnification Jove will be somewhat dimmer because of it's larger image scale with a fixed amount of light gathering power. The inverse square law. Plus, the exit pupil is the final aperture to the eye providing a small relative aperture on your retina.

 

Jupiter may be dim enough at 320x, if not try some more magnification. Plus you will see more of it's low contrast detail at larger image scales. Even if seeing doesn't permit, wait for it. However, if seeing is bothersome, and it can be unpleasant to look through, you might try a filter. I'd recommend a light neutral density filter. I dislike the "false" color of color filters. 

 

I had the same problem a few nights ago, even at 300x in my 8" Newt. A few nights before Jupiter was seen through a thin cloud and looked good even in not great seeing. More recently, Jupiter was in clear skies and it was too bright causing irradiation on my eye. I could have used more magnification but I am currently limited to 300x by a 6mm TMB and a 1.5x Barlow.  


Edited by Asbytec, 21 June 2019 - 08:24 PM.

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#6 skyskan

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Posted 21 June 2019 - 11:01 PM

Oh, wow!

I did not think of the mag power at all.  I always thought anything above 300X would be bad for 8" and my tripod mount. 

Thank you very much for the tip.

 

I am planning two night star gazing next weekend.  I am going to bring my 8mm and 5mm. 

I think 0.5mm exit pupil might be too small though.....  What do you think?



#7 Dave Mitsky

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Posted 22 June 2019 - 02:19 AM

Was poor seeing (atmospheric steadiness) part of the problem?



#8 Asbytec

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Posted 22 June 2019 - 03:38 AM

I think 0.5mm exit pupil might be too small though.....  What do you think?

It might be too small, it may not be. You just have to try it. If you begin to loose detail because Jupiter is becoming too dim for our mesopic vision, then you've gone too far. Back down one notch. If not, stay there or push it up a notch. You might be able to push closer to 400x and still be alright. In any case, 300x is certainly not too much for an 8" aperture for lunar and planetary viewing. The 8mm offers 250x and the 5mm at 400x with 0.5mm exit pupil. Try them both and see.

 

In my 6" I use 240x (0.6mm) all the time, but find 300x (0.5mm) is too much. Conversely, I find 300x (0.6mm) is not enough, It's still too bright in my 8". I really suspect I might be better off at higher magnification. If you have a Barlow, maybe you can find something around 300x or a bit more. If not, hit it with 250x and a light filter. 

 

As Dave Mitsky is asking above, sometimes folks drop down in magnification to get below the seeing effects for a steadier image. The trade off is Jove will be brighter, maybe too bright. It depends on your preferences and what level of detail you want or are able to see on a given night. Seeing will obliterate small detail much of the time, anyway, but so does a very bright image as you indicated in the OP. Not much you can do about seeing (except ensuring your OTA is thermally stable), but you can do something about the image brightness. Wanna tone that down, but not too far. Just right is where you wanna be.  


Edited by Asbytec, 22 June 2019 - 03:53 AM.

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#9 Special Ed

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Posted 22 June 2019 - 06:44 AM

I don't know the OP's location but if Jupiter is way down low, that's not going to help with the seeing.

 

I usually keep a dim light on in my observatory when observing Jupiter so I don't get too dark adapted--that helps with the glare at lower magnifications.  I guess some people have LP do that for them.


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#10 skyskan

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Posted 22 June 2019 - 11:39 AM

I don't know the OP's location but if Jupiter is way down low, that's not going to help with the seeing.

 

I usually keep a dim light on in my observatory when observing Jupiter so I don't get too dark adapted--that helps with the glare at lower magnifications.  I guess some people have LP do that for them.

 

I am at about 47.3 north Jupiter was about 20 degree high.  Maybe that is not high enough..

A few more years, it will become high again

LP “filter” and cloud “filter” give me mixed fieelings.  We do not like it, but helps us sometims ....



#11 skyskan

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Posted 22 June 2019 - 11:43 AM

Was poor seeing (atmospheric steadiness) part of the problem?

I thought the seeing was good, but it was not great around 20 degree altitude.



#12 Dave Mitsky

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Posted 22 June 2019 - 01:25 PM

Jupiter is currently shining at magnitude -2.6.  I observed the transits of Europa and the GRS last night from the Naylor Observatory at 40.1 degrees north using a 12.5" Newtonian and a 17" classical Cassegrain.  The seeing was not particularly good so I used less magnification that I normally would have.  I also stopped the 17" down to 14".  I didn't notice any unusual brightness while observing the planet.

 

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#13 Miranda2525

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Posted 01 July 2019 - 07:58 AM

Jupiter is too bright because you are using too low magnification. At 2030mm focal length, your 11mm ES provides 185x (23x per inch) and ~1mm exit pupil. This is supposed to be near the best magnification for seeing detail, but this is not true. You can and probably need to, if seeing permits (and even if it doesn't), up to about 40x per inch and maybe more.

 

You should be closer to 320x and 0.6mm exit pupil for the best view. At this magnification Jove will be somewhat dimmer because of it's larger image scale with a fixed amount of light gathering power. The inverse square law. Plus, the exit pupil is the final aperture to the eye providing a small relative aperture on your retina.

 

Jupiter may be dim enough at 320x, if not try some more magnification. Plus you will see more of it's low contrast detail at larger image scales. Even if seeing doesn't permit, wait for it. However, if seeing is bothersome, and it can be unpleasant to look through, you might try a filter. I'd recommend a light neutral density filter. I dislike the "false" color of color filters

 

I had the same problem a few nights ago, even at 300x in my 8" Newt. A few nights before Jupiter was seen through a thin cloud and looked good even in not great seeing. More recently, Jupiter was in clear skies and it was too bright causing irradiation on my eye. I could have used more magnification but I am currently limited to 300x by a 6mm TMB and a 1.5x Barlow.  

I respectfully disagree here. I've seen a lot of detail on Jupiter only using 135x and 155x. Local seeing conditions are KING when it comes to what kind of magnification one can use. Also waiting for planets to get to the highest elevation they culminate at for the night. If a Newtonian, there's a lot more to it...But he is using an SCT, which also needs cooling even more...When nights allow, I rarely go over 200x on Jupiter, which my local seeing conditions allow most of the time. It's a rare night when I can go to 300x or over because of my seeing conditions. It could also be his mirror, which could have a rough surface, etc. So many factors involved which needs to be addressed by testing and elimination...

 

IMO, a binoviewer is best on planets when all has been tweaked and aligned...


Edited by Miranda2525, 01 July 2019 - 08:09 AM.

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#14 Miranda2525

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Posted 01 July 2019 - 08:01 AM

I am at about 47.3 north Jupiter was about 20 degree high.  Maybe that is not high enough..

A few more years, it will become high again

LP “filter” and cloud “filter” give me mixed fieelings.  We do not like it, but helps us sometims ....

There lies your problem.


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#15 skyskan

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Posted 01 July 2019 - 12:14 PM

I respectfully disagree here. I've seen a lot of detail on Jupiter only using 135x and 155x. Local seeing conditions are KING when it comes to what kind of magnification one can use. Also waiting for planets to get to the highest elevation they culminate at for the night. If a Newtonian, there's a lot more to it...But he is using an SCT, which also needs cooling even more...When nights allow, I rarely go over 200x on Jupiter, which my local seeing conditions allow most of the time. It's a rare night when I can go to 300x or over because of my seeing conditions. It could also be his mirror, which could have a rough surface, etc. So many factors involved which needs to be addressed by testing and elimination...

 

IMO, a binoviewer is best on planets when all has been tweaked and aligned...

How long should I cool down the scope?  I usually set it outside for 2 ~3 hours before observing.   


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#16 Asbytec

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Posted 01 July 2019 - 01:58 PM

You should cool it until signs of thermal issues, such as a signature heat plume, are gone. Depending on conditions, this may never happen and some form of active cooling or insulation is needed.

As Miranda points out, poor seeing at low altitude is likely your main problem. Maybe coupled with thermal instability. Scopes perform best when thermally stable and well collimated in the best seeing possible.

Miranda, we can agree to disagree. No doubt you've seen great detail at low magnification and with bino viewing. I've seen Jove at these magnifications and agree it looks nice, and I kind of understand the benefit of using two eyes. But simply a function of our eye, it requires sufficient magnification to detect small bright low contrast detail.

Jupiter has a wealth of it. Some of which is lost to seeing and thermals, but also at insufficient magnification. And sometimes irradiance on the eye can blot out detail when Jove is too bright. The answer, again, is a smaller exit pupil and higher magnification. Or a filter. IME...

Regards.

Edited by Asbytec, 01 July 2019 - 02:08 PM.

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#17 Miranda2525

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Posted 01 July 2019 - 02:19 PM

How long should I cool down the scope?  I usually set it outside for 2 ~3 hours before observing.   

Let's see. 

 

You have an 8" SCT. The only proper way to really cool those types of telescopes is with these:

 

https://www.astrosho...eade-8-/p,44537

 

How long to cool for?  I am not 100% sure, as I do not own an SCT, but I would guesstimate at 1-2 hrs.


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#18 Miranda2525

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Posted 01 July 2019 - 02:20 PM

You should cool it until signs of thermal issues, such as a signature heat plume, are gone. Depending on conditions, this may never happen and some form of active cooling or insulation is needed.

As Miranda points out, poor seeing at low altitude is likely your main problem. Maybe coupled with thermal instability. Scopes perform best when thermally stable and well collimated in the best seeing possible.

Miranda, we can agree to disagree. No doubt you've seen great detail at low magnification and with bino viewing. I've seen Jove at these magnifications and agree it looks nice, and I kind of understand the benefit of using two eyes. But simply a function of our eye, it requires sufficient magnification to detect small bright low contrast detail.

Jupiter has a wealth of it. Some of which is lost to seeing and thermals, but also at insufficient magnification. And sometimes irradiance on the eye can blot out detail when Jove is too bright. The answer, again, is a smaller exit pupil and higher magnification. Or a filter. IME...

Regards.

I agree with you on those points.


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#19 skyskan

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Posted 04 July 2019 - 09:52 PM

I was able to go out last night.  It was cloudy and seeing was not so great, but there was no or very little could around Jupiter.

 

At 184X, it was a bright disk with very faint stripes.  When I put on the Meade 6.5mm (312x) that I borrowed from my friend, the glow was a lot less and surface features started showing up.  It was very blurry and jiggly, but it was not fiery disk and I was able to see more surface features.

 

Yes it was dimmer and blurry, but more visible.

 

I took out my iphone and took a shot through the lens.  Please excuse the picture quality.  It came out a lot blurrier than what I saw.  Also, I do not have any astrophotography knowledge or experience. 

 

jupiter_s2.jpg

 

I learned that from where I am with current altitude, it is difficult to observe Jupiter with Hubble clarity smile.gif.  Also, I learned about using more mag for better planetary observing.  I though I should never go near 300x, but it was more than OK and very enjoyable.

 

I think I could use the friend's Meade 6.5 for now, but I am going to get ES 6.7 or Baader 6.5.

 

Thank you fellow stargazers for sharing the insights.


Edited by skyskan, 05 July 2019 - 01:11 AM.

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#20 Miranda2525

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Posted 05 July 2019 - 06:07 AM

I was able to go out last night.  It was cloudy and seeing was not so great, but there was no or very little could around Jupiter.

 

At 184X, it was a bright disk with very faint stripes.  When I put on the Meade 6.5mm (312x) that I borrowed from my friend, the glow was a lot less and surface features started showing up.  It was very blurry and jiggly, but it was not fiery disk and I was able to see more surface features.

 

Yes it was dimmer and blurry, but more visible.

 

I took out my iphone and took a shot through the lens.  Please excuse the picture quality.  It came out a lot blurrier than what I saw.  Also, I do not have any astrophotography knowledge or experience. 

 

attachicon.gif jupiter_s2.jpg

 

I learned that from where I am with current altitude, it is difficult to observe Jupiter with Hubble clarity smile.gif.  Also, I learned about using more mag for better planetary observing.  I though I should never go near 300x, but it was more than OK and very enjoyable.

 

I think I could use the friend's Meade 6.5 for now, but I am going to get ES 6.7 or Baader 6.5.

 

Thank you fellow stargazers for sharing the insights.

Congratulations Skyskan!  Unfortunately none of us can observe with Hubble clarity, lol. 

 

Your picture is an excellent starting point for many better ones to come. I am happy you got to see it better and have a picture to show others. waytogo.gif flowerred.gif


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#21 happylimpet

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Posted 05 July 2019 - 06:38 AM

Dew wouldnt do that. Being too bright wouldnt do that - people observe Jupiter with much larger telescopes.

 

Telescope cooling issues can do that, but if it was delivering good images earlier, it wont be that. Telescopes get better acclimated through the night, not worse.

 

Its just poor seeing, related to the low altitude probably. It comes and goes.  The other night, with Jupiter at ~17degree altitude, I had a surprisingly good view and called my girlfriend out to watch Europa sliding off the disk. In less than a minute it went from a highly detailed view to an insane swirling blob twice the size it should be...which was annoying...10 minutes after she went back into the house it went back again to sharp normality. The atmosphere is dynamic.


Edited by happylimpet, 05 July 2019 - 06:39 AM.

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#22 Asbytec

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Posted 05 July 2019 - 06:40 AM

Yea, I agree...my cell phone astro photography skills are severely lacking. I'm sure the image was much nicer. 

 

I forgot to mention I tried a neutral density filter at 240x and did not like what I saw. Less detail...


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#23 Asbytec

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Posted 05 July 2019 - 09:39 AM

I was out under variable conditions recently. As Miranda said, Jupiter is quite impresive near 240x. I didnt hit at 180X or so. I tried magnifications all the way to 600x putting my focal extender through first light.

The views ranged from bright and crisp at 240x to large and soft at 600x. Best was closer to 240x at 330x. At about 400x is began to soften. Again, its the same nice image we see at 200x, so the degradation happens on the eye as we lose photopic sensitivity. Best image, IMO, happens at about 0.6mm exit pupil and larger to a point.

Here's another tidbit I just found out. Jupiter magnified 200x is about the size of our fovela. Its our vision sweet spot. Not sure that means anything, really, just interesting. We tend to look around larger objects, anyway, focusing on smaller portions of it.

Edited by Asbytec, 05 July 2019 - 09:41 AM.

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#24 sanbai

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Posted 05 July 2019 - 12:54 PM

I would say that one have to experiment with all tools available: eyepieces, filters, masks...

It's not a good strategy limit yourself to a certain magnification just because exit pull is X or because is more than Y times the diameter of the scope.

Test what's best, and enjoy the views. I'be seen in my last sessions that I could push more than expected.

Regarding color filters, your eye can adapt to the color shift quite well. That's the white balance.

If the problem is seeing (or lack of temperature equilibration), it should be easy to identify by the turbulence.
Recently I saw Jupiter like boiling due to this two factors!
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#25 Asbytec

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Posted 05 July 2019 - 06:19 PM

I agree, Santiago. You can certainly test different magnification to see what's best. That's the strategy I employed observing Jove from 240x to 600x the other night. In doing so and in years past, I found something near 0.6mm to be best in the best seeing conditions available to us locally (usually Pickering 7/10 or better). It may be 0.4 or 0.8mm exit pupil on a given night. Or less, but rarely more magnification. I use 0.6mm exit pupil, which itself is an approximation, because I have no idea whether 0.55 or 0.62 is best. But, it'll often be somewhere in that ball park. 

 

One reason I engage these conversations, other than sharing my experience, is the idea of "image breakdown". Folks may get the wrong impression about having a poor optic if Jupiter "breaks down" at higher magnification, but that is not always true. Some of the image break down is physiology and no fault of the scope, it's caused by the small exit pupil. I assert if your image is fine at 1mm exit pupil, at a sufficient magnification to really see a poor optic, then your image is fine at 0.5mm exit pupil, too. It's the same fine image we saw at lower magnification. If Jove is soft up at higher magnification, it's probably also too dim to see well. The problem is likely our own visual acuity at small exit pupils when our eye is operating at a very small relative aperture near 0.6mm f/35 or 0.5mm f/40. And that is perfectly normal for many folks. 

 

As Miranda mentioned above, I see a great Jupiter at about 200x, give or take. But, while experimenting years ago, I noticed I was seeing a bit more at slightly higher magnification toward 0.6mm exit pupil where Jupiter is still just bright enough to register some color and some additional bright low contrast detail. Much above that and the image begins to dim affecting our own physiological acuity. For some, that may happen at 0.5mm or higher for an increasingly smaller number of sharp eye observers with above average acuity. I urge folks to try a bit more magnification and see, if not back down one notch and see, and so on.

 

But, the points are, if Jove is soft up that high, not to fret your scope necessarily being a poor sample. Also, you certainly get very sharp and apparently high contrast views at lower magnification, but you can gain something at a bit higher magnification. The eye likes both a bright and a large image, trick is to find that big bright image with magnification available to you. And it's often not going to be at 25x per inch rule of thumb, unless limited by seeing, rather at somewhat higher magnification if one is amiable to observing whatever seeing conditions prevail. 

 

If Jupiter is a "fireball", that implies it's too bright and higher magnification (small exit pupil as the arbiter of image surface brightness) might be in order. Even in large apertures, Jupiter has right about the same surface brightness at the same exit pupil in all scopes large and small. 


Edited by Asbytec, 05 July 2019 - 06:27 PM.

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