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caheaton
super member
Reged: 05/26/09
Posts: 159
Loc: SW Ohio
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Hello, last night I spent a few minutes observing Jupiter with my XT10 (first light, new scope). The scope is still in need of collimation, and Jupiter wasn't at it's best (being only 20 degrees above the horizon), but still, I swore I saw a dark gray spot, about the size of the great red spot in the northern equatorial belt. The spot was just beyond (as Jupiter rotates) the central meridian. The time of my observation was a little after 10:00PM EST (0300 UTC). Did anybody else notice this feature or were my eyes just playing tricks on me? Conditions weren't the best. I was using barlowed 9.7mm Plossl at the time (247x) and Jupiter was mostly fuzzy but at times would clear up and present a better image.
Craig
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starrancher
professor emeritus
Reged: 06/09/09
Posts: 620
Loc: Northern Arizona
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Quote:
Hello, last night I spent a few minutes observing Jupiter with my XT10 (first light, new scope). The scope is still in need of collimation, and Jupiter wasn't at it's best (being only 20 degrees above the horizon), but still, I swore I saw a dark gray spot, about the size of the great red spot in the northern equatorial belt. The spot was just beyond (as Jupiter rotates) the central meridian. The time of my observation was a little after 10:00PM EST (0300 UTC). Did anybody else notice this feature or were my eyes just playing tricks on me? Conditions weren't the best. I was using barlowed 9.7mm Plossl at the time (247x) and Jupiter was mostly fuzzy but at times would clear up and present a better image.
Craig
Hi Craig ; Although the 10 incher is perfectly capable of handling magnifications well beyond 247X , I believe you would be rewarded with a much better view retaining a hard line detailed Jupiter by leaving the Barlow out of the equation & using the 9.7mm natively yielding a magnification of 124X . In my experience , this is the approximate magnification that I find most reliable in producing the most pleasing views of Jupiter . On a rare night of good seeing , it can be pushed successfully beyond that before suffering image degradation , but I find this to be a rare night with exceptional seeing only .
Dave
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LXD75 AR5
LXD75 SN8
Series 4000 Plossls
Misc. other stuff
Fort Rock , Az .
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Dean Norris
sage
Reged: 11/05/08
Posts: 431
Loc: Santa Cruz, Ca
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Craig, I saw this spot last Friday night. Your timing of this marking matches up pretty well with what I expected for last night. Check out this, Spot/Festoon on Jupiter, in this same forum. I was going to look at it last night but clouds prevailed. I'm glad you saw it and thanks for posting your observation.
Dean
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1971 10" Cave Newtonian F/6
MoonLite CR Focuser Telrad Finder 8x50 finder
TV 40mm, 32, 20, 7.4, Meade 6mm, UO 5mm, Meade 2x Barlow
7x50 Binoculars
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Dean Norris
sage
Reged: 11/05/08
Posts: 431
Loc: Santa Cruz, Ca
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Dave, I think that is good advice on the magnification for Craig's scope. I use 154X on fair nights and 208X on better and higher on exceptional evenings. I have only had 2 times this season that 307X was used effectively on Jupiter. When I added a primary fan to my scope this improved the performance significantly. It was an easy and inexpensive addition for my scope. Oh and I almost forgot, an apodizing mask is a great tool to improve the image on Jupiter and other planets.
Steady skies, Dean
--------------------
1971 10" Cave Newtonian F/6
MoonLite CR Focuser Telrad Finder 8x50 finder
TV 40mm, 32, 20, 7.4, Meade 6mm, UO 5mm, Meade 2x Barlow
7x50 Binoculars
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Sarkikos
Pooh-Bah
Reged: 12/18/07
Posts: 1071
Loc: Suburban Maryland
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Dean,
Do you use your fan the entire time you are observing or turn it off after the 10" Newt has cooled-down? I usually leave it on for the whole observing session. I've tried observations of Jupiter with the fan on, and momentarily with the fan off, and didn't notice any difference, once the scope has acclimated. I know, though, that some observers say the fan can produce vibrations, which even if you don't notice them, can degrade the image.
Mike
P.S.: On nights of average seeing, I observe Jupiter at 200x or less, when the seeing is good 300x, and rarely about 400x. On nights of bad seeing, I don't bother looking at all. I hear some amateurs bump their scopes up to 500x, 600x and more. That would be torture to me. At those ridiculous magnifications, I would mostly see the floaters in my eyes and any dust in the optical train. Exit pupils much below about 1 mm are not a pleasant experience, IMHO.
That is another reason why larger aperture is better for planetary observation, but I never hear it mentioned: the larger the aperture, the larger the exit pupil will be at higher magnifications.
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Celestron 10" f5 Newt on 1stBase (DSO)
Zhumell 8" f6 Newt, Bosma 6" f12 MCT (NSO)
6" f5 Newt, 130ST, 4.5" f4.4 Ball w/GLP, ST80 w/Crayford (RFTs)
C4-R (NSO/DS)
90mm f13 MCT (Luna/DS)
SkyMaster 25x100, 15x70
Zhumell 20x80
Barska XWA 10x50, 8x40
OptiView LPR 10x50
Const View 2.3x40
BV-125C
CG5, 2 drv / CG4, 2 drv, wood legs, ScopeStuff saddle / CG3, 1 drv
SV AZ / 501HDV on Bogen 055XB / P+ on Oberwerk
QuikFinder, Telrad
Orion Dynamo Pro 12, Dew-Not
Have GLP and not afraid to use it!
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Sarkikos
Pooh-Bah
Reged: 12/18/07
Posts: 1071
Loc: Suburban Maryland
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Craig,
I think the term "Great Red Spot" is a misnomer that is a legacy of the time when the spot actually was both Great and Red. Now it is merely dull pinkish or salmon-colored, or even grey, as you say. It is only "great" in the sense that it is large. When I first started observing Jupiter in the 1970's, it was indeed a bright, obvious RED.
Mike
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Celestron 10" f5 Newt on 1stBase (DSO)
Zhumell 8" f6 Newt, Bosma 6" f12 MCT (NSO)
6" f5 Newt, 130ST, 4.5" f4.4 Ball w/GLP, ST80 w/Crayford (RFTs)
C4-R (NSO/DS)
90mm f13 MCT (Luna/DS)
SkyMaster 25x100, 15x70
Zhumell 20x80
Barska XWA 10x50, 8x40
OptiView LPR 10x50
Const View 2.3x40
BV-125C
CG5, 2 drv / CG4, 2 drv, wood legs, ScopeStuff saddle / CG3, 1 drv
SV AZ / 501HDV on Bogen 055XB / P+ on Oberwerk
QuikFinder, Telrad
Orion Dynamo Pro 12, Dew-Not
Have GLP and not afraid to use it!
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Dean Norris
sage
Reged: 11/05/08
Posts: 431
Loc: Santa Cruz, Ca
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Mike, I've noticed that after the mirror cools down that the fan can actually degrade the image. I have seen this on the warm nights of summer primarily. On the cold winter nights the fan usually runs the whole time. When observing Jupiter if the view degrades it can be readily seen on the image of the moons. When this happens I can slow the speed of the fan down since I use a variable voltage converter that enables me to decrease voltage to the fan. On some nights the fan is set to the lowest setting barely blowing on the mirror. On other nights the temperature continues to fall which means the fan will be set at a higher rate.
I will add a indoor outdoor digital thermometer on the back of the mirror to monitor mirror temperature v.s. the air temp. That way I can adjust it accordingly without totally relying on the visual image.
I use elastic bands to attach the mirror to the scope. I haven't had any problems with fan vibrations.
Steady Skies, Dean
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1971 10" Cave Newtonian F/6
MoonLite CR Focuser Telrad Finder 8x50 finder
TV 40mm, 32, 20, 7.4, Meade 6mm, UO 5mm, Meade 2x Barlow
7x50 Binoculars
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