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Jupiter does not look good in my 8" f6.

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#1 stargazer193857

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Posted 11 June 2019 - 01:07 AM

I can barely see the bands, and the moons don't focus to pin points. The outdoors is 10 degrees cooler than outside, and the mirror is 22mm thick, no fans. I rolled the scope out, waited 20 minutes, and saw no improvement. In the past I've seen 3 overlapping planets in this scope and in an 8" SCT. I defocused a moon and saw enough dynamics to suggest thermals or maybe atmospherics is an issue. Up in southern Idaho.

What I will say though is 86x is good for finding, slow drift, and decent sized planer, a good all around mag in a Meade 82 deg eyepiece.

Low resolution views like this are one of the reasons I don't observe much. I have seen a few good planetary views in this scope, so I know the glass is good. I did not check collimation. I also was not wearing my glasses for astigmatism.



#2 Lognic04

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Posted 11 June 2019 - 01:10 AM

You just answered your questions. Wear your glasses, SA is corrected by focusing not Stig. Let it cool for at least an hour, and collimation is essential!!!
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#3 db2005

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Posted 11 June 2019 - 01:38 AM

My old 6" f/8 Newt needed an hour outside before performing well, and I always prefer to take my C8 outside 1 or 2 hours prior to observing.

 

If you have eye-astigmatism you might want to consider using long eye relief eyepieces to allow you wearing eyeglasses comfortably while observing. Personally, I need at least 20 mm of eye relief to observe while wearing my eyeglasses. To name a few eyepieces that have 20 mm eye relief: Vixen SLV, Pentax XW, Televue Delos and Televue Delite. If you don't want to wear eyeglasses while observing, you could take a look at Televue's Dioptrx which correct for astigmatism and are attached on top of Televue's eyepieces.

 

You will absolutely need to pay attention to collimation of your scope. If the scope is out of collimation the effect can easily be mistaken for astigmatism and will seriously hurt performance.

 

Many owners of large scopes have experiences similar to yours: The large scope isn't enjoyable for quick grab-and-go observing because it needs too much time to acclimatize, and is too-high-maintenance and/or too high weight to be genuinely portable for grab-and-go observing. So my grab-and-go scope isn't a Newt or my C8 but a 81 mm APO on a light mount. Small refractors don't have the same problems with cooldown and thermals, and are less sensitive to poor seeing.


Edited by db2005, 11 June 2019 - 01:38 AM.

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#4 ngc7319_20

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Posted 11 June 2019 - 02:39 AM

Jupiter must be very low in the sky -- near the horizon -- from Idaho.  That is certainly not helping.  What you describe is pretty much the views I had in a 24 inch last week, while viewing from similar latitude.  Couple bands and thats about all.

 

If you have dark skies, try something over head instead -- M13, M51, etc.  


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#5 Kyphoron

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Posted 11 June 2019 - 03:06 AM

#1 Collimation

#2 Cooling of the mirrors

#3 Sky Conditions 

 

1# If your scope is not collimated no matter what you do even cooling the mirrors wont help. Take the time each time you set up to collimate your scope. The better its collimated the sharper your views will be.

 

2# Cooling the mirrors is also very important, I have a thermometer with a sensor taped to my primary that shows sensor temp and air temp. So when I see both readings the same or close to the same I know my mirror is cooled. If you don't have cooling fans I would get some, otherwise you will need to set up at least an hour before you observe maybe more.

 

3# If your seeing or transparency is bad no matter what you do you will not have great views. If all the above is done and you are still getting bad views then forget planets and look at DSO's and try planets on another night. Before you even start observing, look up. If the stars are twinkling its not going to be a good night to observe planets. Also, many friends have reported less than great seeing conditions due to the Canadian wildfires.

 

So with all that said, if you have done everything that you should be doing try another night. If you are observing with a friend and they are getting good views in a reflector and you are not then its a mirror issue. Either recoating or refiguring or maybe a simple cleaning.


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#6 happylimpet

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Posted 11 June 2019 - 03:34 AM

Sounds like mainly low altitude combined with a probable jetstream, and also insufficient cooling.


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#7 BGRE

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Posted 11 June 2019 - 04:26 AM

You just answered your questions. Wear your glasses, SA is corrected by focusing not Stig. Let it cool for at least an hour, and collimation is essential!!!


SA is not affected by adjusting the focus!!!
Only the defocus term is affected.

#8 sg6

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Posted 11 June 2019 - 04:56 AM

I can barely see the bands, and the moons don't focus to pin points. The outdoors is 10 degrees cooler than outside, and the mirror is 22mm thick, no fans. I rolled the scope out, waited 20 minutes, and saw no improvement. In the past I've seen 3 overlapping planets in this scope and in an 8" SCT. I defocused a moon and saw enough dynamics to suggest thermals or maybe atmospherics is an issue. Up in southern Idaho.

What I will say though is 86x is good for finding, slow drift, and decent sized planer, a good all around mag in a Meade 82 deg eyepiece.

Low resolution views like this are one of the reasons I don't observe much. I have seen a few good planetary views in this scope, so I know the glass is good. I did not check collimation. I also was not wearing my glasses for astigmatism.

Ignoring cooling, mainly as never sure how great an effect it has - things may not be 100% ideal but would I expect be better since expansion of glass is not that great. The problem is either mirror, eyeballs, or expectations.

 

I say mirror as you say the moons are not pin points. They should be.

Check the collimation, then use your glasses - will say I have astigmatism but don't use mine when viewing. Everything seems OK maybe I lose a little definition but my choice.

 

Expectations - Jupiter is low, but higher for you then for me, 15 degrees Alt here. Check the weather detail - jetstream etc, try meteoblue site for the cloud layers. Quite often there can be a slight high level layer that manages to look absent but destroys detail.

 

Next in expectations is the scope is a newtonian, and you have secondary diffreation patterns that will go through the center of a target. Assuming 4 vanes then Jupiter will be sat where they all meet - the center. Those diffraction patterns will knock a planet down in quality. DSO's are dimmer overall so less of a problem, but a planet will suffer.

 

Try if possible 100x or 120x as comparison. Thought is that Jupiter is bright so you could be getting loss of detail through the brightness of one part swamping another. That doesn't explain the moons not being points however.

 

What eyepieces are you using. Wide is good to find but somewhat oddly planetary eyepieces tend to be narrow. People sacrifice field for central definition.



#9 CHASLX200

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Posted 11 June 2019 - 05:16 AM

Jupiter may never look good for many of ya living way up north. Even in FL it is too low.


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#10 Jon Isaacs

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Posted 11 June 2019 - 05:25 AM

Ignoring cooling, mainly as never sure how great an effect it has - things may not be 100% ideal but would I expect be better since expansion of glass is not that great. The problem is either mirror, eyeballs, or expectations.

 

Thermal equilibrium is critical.  It's not so much the shape of the mirror, it's the tube currents and boundary layer,  convection currents rising from mirror that disturbs the image.  It's like looking through a mirage.  San Diego has a very mild climate, I figure it takes a minimum of an hour for my 10 inch dob to get close to thermal equilibrium, and that is a seal back fan cooling the mirror.  

 

I say mirror as you say the moons are not pin points. They should be.

 

Stars will not be pinpoints if the scope is not cooled.  Stars will not be pinpoints if the scope if the seeing is not stable.  Stars will not be pinpoints if the scope is not collimated. 

 

Boise is 11 degrees north of San Diego.  Jupiter transits at 35 degrees here, that means in Boise it is never more than 24 degrees above the horizon.  To have decent views of Jupiter at 24 degrees (or less), it takes some pretty super seeing.  

 

With a Newtonian, good planetary views require preparation, that means paying attention to collimation and thermal equilibrium.  And then one just has to hope for decent seeing.  With Jupiter so low for northern hemisphere observers, that means observing it as close to culmination as possible.  

 

Sunday night, I was back from two weeks in high desert where the seeing is generally so so but the skies are dark and clear.  I set up my 4 inch refractor. very nice views of Jupiter.  About 11 pm, I decided to setup my 10 inch Dob.  Something I almost never do, I always set it up and start the cooling process before sunset. But with the stable seeing, I was ready for some more aperture.

 

As fate would have it, the power cord to the fan had failed.  I was foiled at every attempt to get power to the fan.  The power converter worked but for some reason there was no power outside.  I tried a 12 volt-110 volt inverter to run the converter off the battery pack.  The inverter was dead.  No fan. 

 

The views were still decent but the stars were not sharp and clean they way they would have been had the scope had been fully cooled.  

 

You can't be lazy when it comes to getting the good planetary views with a Newtonian. 

 

Jon


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#11 Kyphoron

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Posted 11 June 2019 - 05:50 AM

I 100% agree with Jon's statements. If you don't put in the time to get things right on your Dob you will never get the views that you want. Yes its simple to set up a Dob but there are steps you need to follow to get it to give you optimal views. If you don't follow these steps don't blame the scope, blame yourself.


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#12 dave brock

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Posted 11 June 2019 - 05:54 AM

SA is not affected by adjusting the focus!!!
Only the defocus term is affected.


He's meaning you can refocus the scope to suit your eye's focus but not your eye's astigmatism.
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#13 Barlowbill

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Posted 11 June 2019 - 08:54 AM

I had my 8" Dob out two nights ago.  I always try to give Bubba a couple of hours outside to get warm and fuzzy.  Or cooled off, as the case may be.  Jupiter's moons were great.  Pinpoints.  Jupiter...not so much.  Very small and bands barely visible.  I could detect some coloring but not much.  It reminded me of previous views of Mars.  Very small.  That same night, and again last night, I tried the ETX90-AT.  Again, very small and just a touch of color.  Moons visible but tiny.  I attribute the poor view of Jupiter to its lower position and possibly seeing.  There were times when thin clouds were visible but there may even have been clouds that were very thin which I could not easily detect.  I will keep checking Jupiter just to see if it improves but I don't hold out for much improvement.  Spend your time on something else.  I will say this for the little Meade 3 1/2" scope.  It is killer on the moon.  I started recently when it was just a sliver of a crescent and again last night.  Amazing clear views.  I tried 5mm and 3.2mm Astro-Tech Paradigms and both were clear as could be.  2X Barlowed the 5mm and it was still clear as a bell.  No clouds there!


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#14 stargazer193857

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Posted 11 June 2019 - 12:52 PM

I once glimpsed the great red spot, years ago, best view I had in any scope. It was in my 4.5" f8 reflector on a cold winter night after20 minutes of cooling. The tube was painfully cold. I was using a 6mm or 4-5mm Huygen eyepiece, dead center of view. How was the view so good? Only thing that makes sense was it was at the meridian and was at least 45 degrees up.



#15 gordtulloch

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Posted 11 June 2019 - 01:23 PM

It isn't a great Jupiter or Saturn apparition this year, won't get higher than 20deg here (Canada) or even 25deg in the early evening til August and that's pretty crappy. Your scope could be cooled perfectly collimated and otherwise flawless and they'll still look like smears.



#16 spencerj

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Posted 11 June 2019 - 01:35 PM

Jupiter is tough this year.  With my Dob, I have a difficult time finding a location in my yard where Jupiter gets above the trees.  With my refractor, I can set up on my deck and have a better angle, but I am on a deck.  Still had great views of Jupiter with both scopes last week. 

 

The night I had the 12.5" Dob out the GRS was around the back, but in moments of stable seeing, the detail in the bands really popped.  Had an 8mm eyepiece which gave me 225x with a 1.2 mm exit pupil.  Jupiter was a decent size and very bright.  Tried a 5mm eyepiece, but the seeing just wasn't supporting it and the view was a bit soft.  I preferred the sharper view at lower magnification.  I really need a decent 6-7mm planetary eyepiece.

 

The night I had my 5" refractor out the GRS was about at the meridian and was really quite a sight.  I was set up on my deck which is tough, but the tripod and mount are really solid and I was the only one out there.  I used both a 4mm eyepiece for 195x and a 5mm eyepiece for 156x.  The image was not as bright as the Dob the night before, but when the seeing settled the image was just etched on a perfectly black background.        

 

I do look forward to seeing Jupiter and Saturn higher in the sky in a few years, but even this low they are definitely worth the effort.  Like everyone is saying, pay attention to cooling and collimation.  Those are items you can control so you are ready when the seeing cooperates.  Even if those moments are fleeting.



#17 gordtulloch

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Posted 11 June 2019 - 02:16 PM


. Also, many friends have reported less than great seeing conditions due to the Canadian wildfires.
 
Seeing or transparency? I can't see how seeing would be impacted by smoke, but transparency would be, big time. That being said I always thought my best views of the planets were when they were high in the sky on a stinking hot night with utterly still, hazy skies.


#18 NorthernlatAK

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Posted 11 June 2019 - 02:25 PM

We have some fires in alaska as well.While transparency was affected as expected, seeing also was lower than expected. My cleardarksky chart said decent seeing but it looked like boiling soup through the ep. I immediately packed up the scope. Forget Jupiter for me this year, it's only 12° above horizon at meridian. I tested my seeing on the moon at 45° and it was rippling at only 48× mag! (8"dob)

#19 havasman

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Posted 11 June 2019 - 04:15 PM

I can barely see the bands, and the moons don't focus to pin points. The outdoors is 10 degrees cooler than outside, and the mirror is 22mm thick, no fans. I rolled the scope out, waited 20 minutes, and saw no improvement. In the past I've seen 3 overlapping planets in this scope and in an 8" SCT. I defocused a moon and saw enough dynamics to suggest thermals or maybe atmospherics is an issue. Up in southern Idaho.

What I will say though is 86x is good for finding, slow drift, and decent sized planer, a good all around mag in a Meade 82 deg eyepiece.

Low resolution views like this are one of the reasons I don't observe much. I have seen a few good planetary views in this scope, so I know the glass is good. I did not check collimation. I also was not wearing my glasses for astigmatism.

It's unlikely to be the scope that's the root cause of a poorer image than an experienced observer might expect.



#20 Sky Muse

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Posted 11 June 2019 - 06:22 PM

Jupiter may never look good for many of ya living way up north. Even in FL it is too low.

You're at 27° N.  Here at 34° N, the planets are noticeably lower, but not that bad, and certainly lower than where you are.



#21 GeneT

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Posted 11 June 2019 - 08:18 PM

My old 6" f/8 Newt needed an hour outside before performing well, and I always prefer to take my C8 outside 1 or 2 hours prior to observing.

 

If you have eye-astigmatism you might want to consider using long eye relief eyepieces to allow you wearing eyeglasses comfortably while observing. Personally, I need at least 20 mm of eye relief to observe while wearing my eyeglasses. To name a few eyepieces that have 20 mm eye relief: Vixen SLV, Pentax XW, Televue Delos and Televue Delite. If you don't want to wear eyeglasses while observing, you could take a look at Televue's Dioptrx which correct for astigmatism and are attached on top of Televue's eyepieces.

 

You will absolutely need to pay attention to collimation of your scope. If the scope is out of collimation the effect can easily be mistaken for astigmatism and will seriously hurt performance.

 

Many owners of large scopes have experiences similar to yours: The large scope isn't enjoyable for quick grab-and-go observing because it needs too much time to acclimatize, and is too-high-maintenance and/or too high weight to be genuinely portable for grab-and-go observing. So my grab-and-go scope isn't a Newt or my C8 but a 81 mm APO on a light mount. Small refractors don't have the same problems with cooldown and thermals, and are less sensitive to poor seeing.

Great post!


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#22 gwlee

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Posted 11 June 2019 - 09:04 PM

Jupiter is very low in the sky these days. It peaks for me after midnight at about 28 degrees above the horizon, and I am at latitude 38N, so I am looking through all the muk near the horizon and can’t see much detail. 

 

I believe your latitude is higher than mine, so Jupiter is even lower and viewing is probably worse where you live.

 

Jon in San Diego is at about 32N latitude, about six degrees lower latitude than me, so Jupiter is six degrees higher for him than me, so viewing of Jupiter is probably a bit better for him due to his latitude. Comparing a star near Jupiter to a star near the zenith will help you determine if this is the source of your problem. 

 

Of course, you need to be cooled, collimated, and wearing your eyeglasses to get the best out of your scope, but you just have to live with your latitude. Tonight, I am using a small refractor, so I don’t need to be concerned about collimation, and cooling is a much smaller concern, but I must give up 2/3 of the resolution of your, 8”f6 to get these benefits, so you are much better equipped for viewing Jupiter tonight as long as you are cooled and collimated. 


Edited by gwlee, 11 June 2019 - 10:53 PM.

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#23 gwlee

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Posted 11 June 2019 - 11:21 PM

I once glimpsed the great red spot, years ago, best view I had in any scope. It was in my 4.5" f8 reflector on a cold winter night after20 minutes of cooling. The tube was painfully cold. I was using a 6mm or 4-5mm Huygen eyepiece, dead center of view. How was the view so good? Only thing that makes sense was it was at the meridian and was at least 45 degrees up.

The red spot rotates with the planet, so it won’t  be visible unless you happen to catch Jupiter when the red spot is facing our way. The red spot doesn’t seem all that red these days, but an 8”f6 is usually enough scope if the seeing isn’t too bad, and the seeing is usually better the higher the elevation. 


Edited by gwlee, 12 June 2019 - 12:08 AM.


#24 Stephen Kennedy

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Posted 12 June 2019 - 06:04 AM

I can barely see the bands, and the moons don't focus to pin points. The outdoors is 10 degrees cooler than outside, and the mirror is 22mm thick, no fans. I rolled the scope out, waited 20 minutes, and saw no improvement. In the past I've seen 3 overlapping planets in this scope and in an 8" SCT. I defocused a moon and saw enough dynamics to suggest thermals or maybe atmospherics is an issue. Up in southern Idaho.

What I will say though is 86x is good for finding, slow drift, and decent sized planer, a good all around mag in a Meade 82 deg eyepiece.

Low resolution views like this are one of the reasons I don't observe much. I have seen a few good planetary views in this scope, so I know the glass is good. I did not check collimation. I also was not wearing my glasses for astigmatism.

In my 210 mm (8,3") F/7,7 Newtonian the moons do not focus to a pinpoint, they focus to 4 clearly defined small disks when the seeing conditions are good.  A  good Newtonian reflector in this aperture class should be able to resolve the 4 main moons of Jupiter into disks with adequate viewing conditions.  The problem is that Jupiter is at such a low latitude this year and the years to come that it is unlikely any telescope in northern latitudes will be able to see a clear view of Jupiter and its moons. 


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#25 CHASLX200

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Posted 12 June 2019 - 06:07 AM

In my 210 mm (8,3") F/7,7 Newtonian the moons do not focus to a pinpoint, they focus to 4 clearly defined small disks when the seeing conditions are good.  A  good Newtonian reflector in this aperture class should be able to resolve the 4 main moons of Jupiter into disks with adequate viewing conditions.  The problem is that Jupiter is at such a low latitude this year and the years to come that it is unlikely any telescope in northern latitudes will be able to see a clear view of Jupiter and its moons. 

I have no problem seeing all 4 moons as diff size clean disk with my 8" F/6. I use the moons to touch up collimation if it needs it.


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