Star gazing at Saturn...

[Steve Swancott]

Hello all

Just out of curiosity, dark skies no LP, with a skywatcher 200 and 4mm eyepiece what will saturn look like?

Thanks

Steve

[houston]

4mm may be too much mag for sharp image, used 10mm with 2x barlow a view times in same scope and not as good as 10mm on its own, moves through field of view very fast as well so forever nudging scope to keep up! Id say 6, 7, or 8mm would be max.

[Steep]

I have difficulty using a 5mm in my 10" dob, it's needs very good seeing to offer it's best views. I'd think a 4mm would be pushing it in an 8" as well unless you have very clear skies.

[todd8137]

I think you ,would be on the very limits of your scope,1200 divided by 4 =x300 thats really pushing it for UK skies even on a brill night i found image scale on my 300p was not great people will disagree with me but reflectors are not that great forplanets imho

pat

[ian_j_kirk]

as above, Thats a bit too much power. I have the same scope and i suggest using the 10 mm also. Image may be slightly smaller but you will see more detail as the image won't be fuzzy or lacking contrast.

[Steve Swancott]

Ok thanks for the advice. What do you mean 'too powerfull for the scope?' Will the image just not come into focus? And what would be ideal to use a 4mm on?

Thanks again

Steve

[Steep]

To give you an idea Steve, where I live the sky is very seldom steady at high altitude, moisture in the air and heat rising cause the shimmering effect that Patrick Moore used to call 'jellyfish skies'. My 5mm eyepiece on the 10" dob intensifies that effect to the point where viewing planets and stars can become impossible, the 5mm should be nicely within the range my scope can handle but the weather says otherwise. On the other hand my 10mm gives fantastic views most of the time and Jupiter for example is much sharper and clearer with it even on a 'bad' night than I've ever seen it with the 5mm.

[umadog]

Ok thanks for the advice. What do you mean 'too powerfull for the scope?' Will the image just not come into focus? And what would be ideal to use a 4mm on?

Thanks again

Steve

No, 300x isn't too powerful for the scope. Most telescopes will be able to churn out 30x to 40x per inch. A scope with good optics (and plenty of these Asian scopes are good) will get to 50x per inch so an 8" Dob with excellent optics will get to 400x. However (big however) the atmospheric stability will always limit what power you can use. Most nights 200x is the limit largely irrespective of aperture. You know you've hit the seeing limit because when you go beyond it the image will look worse.

There's an interesting point about aperture, actually, and this is that smaller scopes perform better when the seeing is bad than substantially larger scopes. It's quite uncanny: I've been out on a bad night trying to split a 2 arc second double star with my 18" and failed. If I mask down the scope to 7" the double splits cleanly. On nights of better seeing, this difference disappears. That's obviously not something that concerns you directly, but it's interesting to know. So if the seeing limit is 200x for your 8", then your mate's 12" is also at the same limit.

[John]

One thing is for sure, like all planets, Saturn will look better the longer you observe it.

Seeing good planetary detail requires a number of factors to come together; the seeing conditions, the scope being cooled and in collimation, a decent eyepiece, the "right" magnification and a trained eye. Spending time on it is a very important contributor to achieving that last one. At first the details visible might be reasonable but the longer you look, the more your will see. The eye seems to train itself to pick out the subtle details, as the seeing allows, over a longer session. "Subtle details" can include the Cassini Division in the rings which does not always jump out at you, even with large aperture scopes.

Saturn seems to "take" higher magnifications than are used on Jupiter but these need to be added incrementally and you need to allow yourself time to get adjusted to teasing the finer detail out from the planet.

[blueroom]

One thing is for sure, like all planets, Saturn will look better the longer you observe it.

Seeing good planetary detail requires a number of factors to come together; the seeing conditions, the scope being cooled and in collimation, a decent eyepiece, the "right" magnification and a trained eye. Spending time on it is a very important contributor to achieving that last one. At first the details visible might be reasonable but the longer you look, the more your will see. The eye seems to train itself to pick out the subtle details, as the seeing allows, over a longer session. "Subtle details" can include the Cassini Division in the rings which does not always jump out at you, even with large aperture scopes.

Saturn seems to "take" higher magnifications than are used on Jupiter but these need to be added incrementally and you need to allow yourself time to get adjusted to teasing the finer detail out from the planet.

That's a very interesting post there John, I'm going to bear this in mind next time I'm looking at the planets

[brantuk]

Also don't forget it's much better if your eye is totally dark adapted which takes about 20mins - and if your observing location is pitch black dark.

[Steve Swancott]

So in a way would it be pointless investing in a 4mm eyepiece? Or just not for as close celestrial objects?

[cgarry]

Also don't forget it's much better if your eye is totally dark adapted which takes about 20mins - and if your observing location is pitch black dark.

I always thought dark adapted eyes are bad for planets as that stops you seeing the colours...

Chris

[blueroom]

I think a 6mm EP would be better.

[houston]

How about 8mm with 2x barlow and if you cant use it much you still have the 8mm and the barlow to use with the rest of your eyepieces.

[bingevader]

I think a 6mm EP would be better.

Me too!

Works very well from my back garden.

Cheers

[LukeSkywatcher]

I tend not to go more than 8mm when observing planets. Ive used an 8mm EP with scopes from 90mm,130mm and 200mm and 8mm EP just seems to be the happy number for me. 6mm would probably be OK on nights of great "seeing".

The only time i have used a 4mm EP was one night a couple of years ago when the conditions were the best i have ever known. The Moon was about 60% full, so i used my 4mm Celestron Omni to observe the Moon. This was using my 130mm reflector. Best view of the Moon i have ever had. I felt like i was in orbit around the moon.

[umadog]

I always thought dark adapted eyes are bad for planets as that stops you seeing the colours...

Chris

Yes, they're bright so you don't need to be dark adapted. You see colour and sharp detail on planets: that stuff is mediated through your higher resolution cone pathways rather than the rods. Just try looking at Jupiter after dark adapting for an hour: it's unpleasant for a few seconds until you adapt. Some planetary guys claim that looking at a bright light periodically will help with Jupiter observations. Perhaps it does but I can't see why it should, since when you look at Jupiter your eye will automatically light adapt to the appropriate level and stay there. Still, the bright light thing is worth experimenting with.

[blueroom]

We had lovely clear skies last night and I waited till about 1.30am when Saturn was quite high in the sky and I was blown away by how stunning it was

The best view was through my 8mm BST but even through a 25mm it was still impressive! I could see one of its moons (don't know which one) and could just about make out the Cassini division if I looked long & hard enough

[SteveNickolls]

Have you tried this? http://www.12dstring.me.uk/fov.htm

Cheers,

Steve

[Steve Swancott]

Thats great cheers

[Steve Swancott]

Completly random (ish) can you see the whirlpool galaxy in good conditions with an 8 inch?

[Siriusmeg]

Yes - but as a faint fuzz with 2 cores. Seen it several times and this is about as good as it gets

[starman1969]

I looked at Saturn with a fellow astro member's 200p last night. I don't know what the mag was but the Cassini Division was in & out. It did take a fair bit of viewing to see the detail. The seeing was average.

[Qualia]

I find Saturn very hard to observe. No matter the seeing conditions, it always feels like it is trying to keep something secret from me. Saturn is a very mysterious jewel of the night sky.