Jupiter from suburban Adelaide ?

[mr.sneezy (Martin)]

I have a 127mm Newtonian (Celestron EQ127) and a very old 60mm Tasco refractor. Jupiter is very bright and prominent right now so I've looked at it a few times with both scopes.
I thought I'd see some of the darker bands on the surface with the bigger diameter scope, but I can't. Is that normal for Jupiter from typically light poluted suburbs ?

[Coen]

In recent time the contrast on Jupiter's disk has dropped off. I've noticed the bands are not as dark as they used to be for example and others have commented on the fading (in the sense of contrast) of the red-spot.

Also recently the seeing has been poor which does not help matters much either.

Still, grab yourself some timings of the eclipses, occultations, and transits (both shadow and moon) of the four principle satellites as they are good to watch as they do their dance with Jupiter. With your 127mm you should not have any dramas seeing a number of these events.

A few weeks back I had the 120mm refractor and was showing folk (school viewing night) Jupiter and fortuitously Callisto was on the edge of the disk with it just being visible with aid of a filter and patches of good seeing. Then it gradually went off the planet and appeared next to Jupiter. The kids and parents thought it was pretty cool. In fact the telescope spent most of its time on Jupiter because so many wanted to see it. He is the king and respect must be paid.

[bmitchell82 (Brendan)]

in relation to your question, yes you should be able to see the bands easily with the scope you have. the next question i have to ask you have you collimnated the scope? being a newtonian or reflector will kill your contrast faster than a train hitting a rabbit!

[mr.sneezy (Martin)]

Originally Posted by bmitchell82

in relation to your question, yes you should be able to see the bands easily with the scope you have. the next question i have to ask you have you collimnated the scope? being a newtonian or reflector will kill your contrast faster than a train hitting a rabbit!

Yes, I've learned how to collimate it. Built a combination tube for doing that.
This scope has a correction lens in the focuser and I wonder now if I should remove it to collimate it, even though it looks OK doing a star diffraction test.

[bmitchell82 (Brendan)]

you have one of them... they are a challange even for the experienced to align... ide definately recomend that you remove the barlow lense to align the main mirror. the other thing is to use a laser to get the angle of the secondary right, as you might have it decent to eye but if the angle isn't right for the secondary to primary tilt, your pushing 5h17 up a hill.

Im just a little confused if your just begining in this hobby or you have done it for a while as a star test im still getting my head around what all the different patterns mean and im learning very quickly what it all means because its the only tool i have for getting everything spot on for astrophotography. and are you using a barlow to magnify the star to see the airy diffraction rings?

[multiweb (Marc)]

Originally Posted by bmitchell82

you have one of them... they are a challange even for the experienced to align... ide definately recomend that you remove the barlow lense to align the main mirror. the other thing is to use a laser to get the angle of the secondary right, as you might have it decent to eye but if the angle isn't right for the secondary to primary tilt, your pushing 5h17 up a hill.

Im just a little confused if your just begining in this hobby or you have done it for a while as a star test im still getting my head around what all the different patterns mean and im learning very quickly what it all means because its the only tool i have for getting everything spot on for astrophotography. and are you using a barlow to magnify the star to see the airy diffraction rings?

I just follow this simple rule as a guide: F/5 use a 5mm eyepiece, F/10 10mm or similar. Defocus slightly on both sides. Out focus always looks better than in focus for me.

[bmitchell82 (Brendan)]

I have read information stating other wise. its not about your f number as much as your size of your mirror/lens for me to get good airy rings i need a 5x power mate good seeing and a 20mm ep that expands the rings so you can see them clearly

[mr.sneezy (Martin)]

Originally Posted by bmitchell82

Im just a little confused if your just begining in this hobby or you have done it for a while as a star test im still getting my head around what all the different patterns mean

Yes I'm closer to a newbie, but I understand optics 'reasonably' well. I'd love to invest in better gear, but I only get the urge to go see some stars for a couple of hours a year.
I have at least ten other hobbies too, the lowest ranked time wise is astronomy.

The star diffraction test I do with a 9mm EP and just de-focus slightly then look at the uniformness of the pattern. Round is good (for me), squashed to one side or comet-like is bad (very). The scope is F8 BTW.

I suspect that although the 127mm is giving much more light than the old 60mm refractor, it's resolution is perhaps rubbish. Oh well, if an alignment with the correction lens removed proves useless I can always rat the hardware off it and rebuild it with a real parabolic mirror. Another guy here has done that, and it sounds like my style too...

[Rigel003 (Graeme)]

Your 127 mm should show the cloud bands clearly. If you are just taking the occasional casual look, you also need to be aware that the visibility of surface detail is very much dependent on the state of our atmosphere. There are some nights when Jupiter just appears an unfocussed mess in any telescope and the odd rare night when you can suddenly see a lot more detail. You might just have been unlucky with your timing.

[mr.sneezy (Martin)]

Originally Posted by Rigel003

There are some nights when Jupiter just appears an unfocussed mess in any telescope and the odd rare night when you can suddenly see a lot more detail. You might just have been unlucky with your timing.

Thanks, that sounds like good advice. I'll try another night or two.