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Jupiter does not look good in my 8" f6.

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#26 spencerj

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Posted 12 June 2019 - 08:20 AM

I am at 43N latitude.  Yesterday was pretty windy (all day and into the evening) and the seeing forecast was not good.  It was a series of gray blocks in both CSC and Astrospheric, but it was clear so I set up my 5" refractor on my deck.  I didn't really plan for it so there was zero cool down time.  I took a look and it wasn't that bad.  GRS was around back, but I was seeing some decent detail in the bands.  One of the moons was just off the face of the planet so I decided to hang around and see if it was going to go in front or behind the disc. 

 

Best views were at about 200x.  Jupiter is pretty big right now since we are days from opposition (been meaning to look up the exact angular size) so the image scale was pretty decent.  As I was waiting to see how things would play out with the moon off the face, I noticed a dark spot in one of the equatorial belts.  In moments of better seeing, that spot sharpened up into a small, perfect circle.  Turns out another moon (Io) was crossing the planet as well.  Twenty minutes later, the second moon (Ganymede) was crossing the planet.  It had been a while since I lucked into a completely unknown-to-me double shadow transit.

 

I watched the spectacle for another 45 minutes or so with the refractor really getting acclimated and putting up stunning images.  I was able to follow Ganymede onto the planet and see the disc easily, just ahead of the shadow.  Kept trying to see Io on the face of the planet and maybe did a couple of times, but very fleeting and nothing I could hold long enough to say for sure even though the shadow of Io was very clear and distinct an visible 80%+ of the time.  Being near opposition, the shadows are very close to the moons, but that still didn't help with Io.  The size differences between the shadows of the two moons was very obvious.  Ganymede was noticeably larger.                

 

The moral of the story is . . . take a look.  If it is clear and Jupiter is out, set something up and take a look.  Who cares if it is too low in the sky this year or if the sky on a particular night doesn't look perfect?  The more opportunities you give yourself the more you will see.  


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#27 Stephen Kennedy

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Posted 12 June 2019 - 03:24 PM

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.

When I normally observe Jupiter I use the moons' appearances rather than surface detail on the planet itself to determine when I have reached the best possible focus.  Here in the Sacramento area, out latitude is about 38 degrees North which I think is considerably higher than Tampa.  In all honesty, I have not spent much time observing Jupiter or Saturn this year because they are so close to the southern horizon it really is not worth the effort. 


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#28 areyoukiddingme

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Posted 12 June 2019 - 03:52 PM

I would have had to agree with everything I've heard in this thread about cooling and tube currents and whatnot. But not anymore. . . at least not for one scope:

 

I now have an 8" F7 with a thin quartz primary, and this thing is ready to go faster than my 80mm refractor.

 

I'm finding that I can get very good views of Jupiter immediately with approx 10-15F temperature deltas.

 

Yes, it gets better with time, but it's surprisingly good right off the bat. If the sky is steady, I see thin band details in the temperate zone of Jupiter. This to me is one of the markers of excellent optics, as it seems the detail gets lost in light scatter from lesser optics.

 

It's housed in a 10" aluminum tube, and I have a rear-blowing fan that helps things along.

 

I bought all the parts off a guy who was going to use it to image, and realized it was not right for that. It gets mounted alt-az style on a Skytee mount on a CG-5 tripod.

 

I'm a convert to thin quartz primaries because of this scope. I had heard of people saying that these primaries only need a boundary layer fan to get good results, and I'm finding that is very much consistent with my experience.



#29 Sketcher

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Posted 12 June 2019 - 04:48 PM

As others have basically stated:  You have to work at getting the good planetary views.  This means collimation and thermal issues should not be ignored when using a Newtonian.

 

Your latitude and Jupiter's declination make things even more difficult, but not necessarily impossible.  My own latitude is a bit more northerly than Boise.  That means Jupiter is a bit lower in my sky.  Yet, along with the (inevitable) poor nights, I've had my fair share of decent nights.

 

On one night Jupiter showed a fair amount of detail in a 6-inch f/6.5 achromat -- the GRS; various belts and zones, some with structure within them.  On a subsequent night I used a 5-inch apochromat (with essentially 'perfect' optics), and the view was worse -- due to less cooperative seeing conditions.   On the third night, with the 5-inch again, I was seeing more detail than I had seen previously with the 6-inch.  Seeing conditions had improved over the previous 5-inch attempt, permitting that scope to perform closer to it's peak capability.

 

Some nights just aren't good for planetary observation -- especially when the planet doesn't rise much beyond 20 degrees (at its highest) above one's south horizon.  But if one doesn't give up, if one gives it a try on each clear opportunity, one might just (eventually) get lucky with seeing conditions.  At such times, one will want their telescope to be precisely collimated and thermally settled.

 

An unfortunate truth is:  We can't just plop down our telescopes and expect to see a wealth of fine detail in Jupiter's clouds.  There are too many variables that can get in the way.  Our "job" is to tame as many of those variables as we have power to tame; but even then, sometimes one or more of the remaining variables set up roadblocks for us -- and we have to try again on a different night.

 

One more thing (that may be unnecessary to mention):  It's better to observe Jupiter around the time when it's highest (due south) in your sky in order to maximize your chances of cooperative seeing conditions.  This practice comes with no guarantees, but it improves one's odds of having a successful Jupiter observing session.

 

If astronomical observing were easy, some of us would have dropped it long ago for something more challenging.  Part of the pleasure (for some of us) comes from our attempts (sometimes successful, sometimes not) in overcoming the difficulties that nature places in or paths.


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#30 CHASLX200

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Posted 12 June 2019 - 05:43 PM

When I normally observe Jupiter I use the moons' appearances rather than surface detail on the planet itself to determine when I have reached the best possible focus.  Here in the Sacramento area, out latitude is about 38 degrees North which I think is considerably higher than Tampa.  In all honesty, I have not spent much time observing Jupiter or Saturn this year because they are so close to the southern horizon it really is not worth the effort. 

I have not done much with both planets as well. The little disk are great to check collimation. 


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#31 jayrome

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Posted 14 June 2019 - 01:35 PM

I was observing Jupiter last Saturday and my spot is at 46 degrees north latitude. Not great views of Jupiter but not bad. That being said seeing conditions were good and my scope was well collimated once I got out there.

Saturn sucked tho lol.gif lol.gif lol.gif


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#32 KLWalsh

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Posted 15 June 2019 - 09:18 PM

A reminder: If you wear progressive lens eyeglasses while observing, images through an eyepiece will likely look distorted.
If you really need glasses, get single-prescription lenses for looking through the eyepiece.

#33 stargazer193857

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Posted 19 June 2019 - 02:59 AM

I took the 8" out again. Jupiter was at meridian. Still looked bad. The moons were pinpoints in the 24mm but coma shaped in the 5.5mm. I know coma does not magnify, so that means the collimation is off.

Collimating is much easier with a laser, but the batteries died. I'll get some, since I also need them for my shop clock.


...

I did stumble on the ring nebula for the first time though. It was a ring in the 24mm. Blew up nicely in the 5.5mm.

...

Also, my friend seems to have lost the Allen wrench I gave him for this scope. So, I can just try the 6" f5, which is much easier to collimate with dob knobs.

Edited by stargazer193857, 19 June 2019 - 03:23 AM.


#34 stargazer193857

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Posted 19 June 2019 - 03:11 AM

A reminder: If you wear progressive lens eyeglasses while observing, images through an eyepiece will likely look distorted.
If you really need glasses, get single-prescription lenses for looking through the eyepiece.


I don't need glasses except to appreciate the value of a paracore. Even then, my vision is only corrected to 20/20. I wish it were 20/8, but oh well. I'm better off than some.


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