More than 167x for planets?

[Chipela]

Hello,

I'm pretty interested in observing planets. The biggest magnification with my current gear is 167x which I have successfully used to observe Uranus and Jupiter. In both cases, I felt that the planet is a bit small in the view of the eyepiece. And that made me thinking of getting a shorter focal length eyepiece which would give me a magnification in the range 200x...250x.

But am I on the right track here? Would the jump from 167x to, say, 214x or 250x give me a more pleasing view? Or would I still feel that the planets seem small and the contrast, seeing related etc. issues would actually make the view worse.

I have also considered a planetary zoom, the Televue Nagler Zoom 3-6mm. However, that has a bit short eye relief and it would make my 4.5mm eyepiece obsolete. (I know that many planetary eyepieces have tiny eye relief but I'm a bit spoiled by the ~20mm eye relief my Televues have.    ) So if not settling for 167x, my current idea is to get another eyepiece on 3mm...3.5mm range (maybe they will introduce a 3mm DeLite soon  ).

Chipela

[John]

I use 200x - 320x in the planets with my 12" dobsonian when the seeing conditions allow. With your 6" you might find that 150x - 200x is more effective much of the time with 250x being worthwhile occasionally when the seeing conditions are very good. Jupiter does not respond to really high magnifications too well but Saturn and Mars are worth really boosting the power on, if the conditions allow (the most important bit !).

I've owned the Tele Vue Nagler 3-6 mm zoom on 3 occasions !. It's a great eyepiece but your Delos 4.5mm is a wee bit better again. In fact the Delos is practically as good as it gets so there is the 3.5mm Delos of course !

Perhaps have a think about the "3 C's" Conditions (seeing), Cooling and Collimation as well as eyepieces ?

[ronin]

167x to 200x is just about 20% extra in size, so if small now it is not going to suddenly fill the eyepiece.

I would expect the 150 to get to 200x, or 220x, but after that I suspect the image quality will drop off as quick as the magnification goes up. Especilly as you have a fast reflector, they are good but tend to produce a "softer" image and for planets you really want a sharp high contrast image. Just the way they operate, that central obstruction allows a big mirror but there are drawbacks.

Planets are a long way off, the closest Jupiter gets is just under 630 million Km and I doubt it is that close this time round, and the 150 is not exactly a big scope.

[niallk]

Hi - after the prerequisite 3 C's, have you considered trying binoviewing for planets? In my 250px, I tried a Baader Maxbright Bino, 2x TV 15mm plossls, and a 2.5x GPC: ~ 240x mag.

Please note that apparently not everyone gets on with binoveiwers, but fortunately I find it really good for detail on Jupiter, Saturn, Mars, Moon, sunspots, etc.

[michael.h.f.wilkinson]

I am not sure binoviewing is a good option on the Newtonian we are talking about. The 150PDS may not have enough inward focus to allow binoviewing. My old 6" F/8 allowed me to go to 150-180x but beyond the conditions needed to be near perfect to get any gain. My C8 allows 200x more regularly, and 254x and 290x are useful under good conditions too.

[Moonshane]

Just so you have a realistic understanding of approximate size in the eyepiece, here's a sketch of Mars I did at about 180x with the apparent (real) size in the eyepiece shown as the little 'pea' to the right. The detail visible with prolonged 'staring' though is often quite surprising, even with such a small image. Jupiter is larger and therefore easier to see more detail on and even at 150x you'll get good levels of interest if you look for a while. Seeing comes in and out of sharpness with our water vapour filled atmosphere so be patient.

[niallk]

I am not sure binoviewing is a good option on the Newtonian we are talking about. The 150PDS may not have enough inward focus to allow binoviewing. My old 6" F/8 allowed me to go to 150-180x but beyond the conditions needed to be near perfect to get any gain. My C8 allows 200x more regularly, and 254x and 290x are useful under good conditions too.

Thanks - that's a very important point re reaching focus.

I can only vouch for my own EP & scope combos. I had trouble with focusser travel in my 15" and was initially dismayed (thought I'd have to get a second set of shortened trusses) - but thankfully I can substitute my Powermate for the GPC and it works.

[Chipela]

Just so you have a realistic understanding of approximate size in the eyepiece, here's a sketch of Mars I did at about 180x with the apparent (real) size in the eyepiece shown as the little 'pea' to the right. The detail visible with prolonged 'staring' though is often quite surprising, even with such a small image.

Amazing visualization of the real apparent size and on the other hand how much detail can be seen!

Thanks for all the answers. I decided not to rush into buying any higher power eyepieces for now (yeah, yeah...  ) but will spend time with the 4.5mm / 167x to learn to get most out of it!

[dweller25]

Hello Chipela,

In my 5" refractor I use :-

x180 on Jupiter

X200 on Saturn

X250 on Mars

The minimum magnification that will show the most detail for your scope is x1.3 the aperture, so thats x190 for your scope

[Yearofthegoat]

Last winter I got one night of truly fantastic views of Jupiter through my 150P-DS and 3.2mm BST Starguider. A still, clear night and cold into the bargain, around -1. Scope was frosted when I came in but Jupiter had kept me out way longer than I should have, despite being blimmin' frozen.

No such luck yet this year, but that's more to do with the permacloud we've had lately (which seems like it just might be ending...?)

HTH

[Tomjo59]

There is an old rule-of-thumb that the 'best' magnification to use on the planets is about equal to the aperture of your scope, so x167 would be about right for your SW 150.

This comes with the usual caveats about good seeing conditions, allowing adequate cooling down time, good collimation etc.

Even after years of observing the planets, I am still surprised at how much better I can discern detail on the planets at lower magnifications, and thus smaller image size. Seems counter intuitive. Experience counts for a lot though, learning to 'train' the eye to pick out details.

[Chipela]

Even after years of observing the planets, I am still surprised at how much better I can discern detail on the planets at lower magnifications, and thus smaller image size. Seems counter intuitive. Experience counts for a lot though, learning to 'train' the eye to pick out details.

Thanks for encouraging words! The 150PDS and it's limiting magnitude is what I have so it's good to hear that observing with less magnification is not necessarily a bad thing.

Speaking of which, I observed the moon this night and unlike other times, decided to start with 17.3mm (43x) instead of the usual 9mm (83x).

I was very pleased with the view! Moon looked crisper than I had ever seen. And since it's apparent angle was smaller than with 9mm, it was easier to see it as a whole. And yet, I was able to see so much detail even if the detail was smaller. The quality of the EP might also have had an effect although the X-Cel seems to be a fine EP.