Best Telescope for viewing planets

[johninderby]

Or if you want a really big Mak ?

http://apm-telescopes-englisch.shopgate.com/item/32393331

[Trikeflyer]

That’s not the kind of big Mak I could afford! Besides there’s no fries with it ?

[John]

Imagine the cool down time on that thing if it's above outside temp ?

[johninderby]

Just now, John said:

Imagine the cool down time on that thing if it's above outside temp ?

You’d have to put it out a week before. ?

[bluesilver]

22 hours ago, Paul73 said:

Agreed. I had a 120 ED refractor. The planetary views were very very sharp, but image scale is a bit of an issue. Atmospheric turbulence should be less of an issue with the planets high, so I’d sacrifice a little bit of sharpness for the bigger image.

Paul

Just out of curiosity,  was the image that you got from this 120 Ed refractor much smaller that that from the Dobsonian,  or are the image sizes all about the same size regardless of the size of the telescope,  So roughly,  the image size from the 120 Ed refractor is about the same size you see though the 10 inch or 16 inch dobsonian?

[John]

1 hour ago, bluesilver said:

Just out of curiosity,  was the image that you got from this 120 Ed refractor much smaller that that from the Dobsonian,  or are the image sizes all about the same size regardless of the size of the telescope,  So roughly,  the image size from the 120 Ed refractor is about the same size you see though the 10 inch or 16 inch dobsonian?

Image size depends on the magnification used. With aperture you get a brighter image with potentially more detail within it but the image scale (ie: the angular size of the planet in the eyepiece) remains the same so Jupiter at, say, 250x looks the same size in the eyepiece with my ED120 and my 12 inch dobsonian.

 

[Piero]

If the seeing is stable I would go for more aperture, as long as this is still manageable of course. 

The planetary views I had with my 8" skywatcher Dobson in Italy were all substantially better than the views I had using my Tak 100 here in Cambridge, UK. Both under good seeing conditions. (Feel free to argue).

Regarding smaller apertures working better than larger apertures when the planets are low, in my opinion this has nothing to do with the aperture, assuming the optics are properly cooled down. To me it has more to do with the way the optics are mounted. Heavier optics weigh more. If the mirror cell does not well support the mirror when this is inclined, you have a minor but noticeable miscollimation. I notice this on my 8" skywatcher dobson too, when pointing few degrees above the horizon. That is why Glatter's slings and similar exist.

[Paul73]

I found that the ED120 struggled to reach the same magnifications as longer fl scopes. Can’t fault the image quality though. Could just be my eyes.

However, when observing in the UK, you seem to be mostly magnifying turbulence......

Paul

[Louis D]

The best planetary views I've had have been through 12"+, f/5+ Dobs with super-premium primary mirrors such as from Zambuto or Lockwood.  They excel at putting all the photons in the correct locations to bring out low contrast details better than your typical mass produced mirrors sitting alongside them at star parties.  This all assumes well above average seeing which you should get in Australia.

[Stu]

If you do move to a 16" dob, then one thing you can experiment with is aperture masks. I viewed through @Moonshane's scope once as I already mentioned, and in the poor seeing conditions he put an 170mm aperture mask on to see if it stabilised things. This is basically a mask cut and positioned so that it sits between one quadrant of the secondary spider, and effectively gives a 170mm unobstructed aperture scope. The smaller aperture cuts through the seeing better and you also dont get diffraction spikes.

This was quite a few years ago, and as I recall the views through the smaller aperture we indeed more stable and 'easier' to view. Ultimately the full 16" showed more detail and more saturated colours, but you had to wait longer for periods of better seeing when the image stabilised and you could enjoy the views.

I suspect that with the planets at high altitude as they are at your location you would be able to enjoy full aperture viewing with a large scope with excellent results. You should be able to push the magnification significantly higher than we can on the UK with them so low in the sky.

[jetstream]

On 09/05/2019 at 01:03, dweller25 said:

Your 10” Newtonian will outperform both of these scopes.......

I remember asking a similar question as the OP and your response was the same- and absolutely correct (thanks BTW). The 10" dob is Vg for planetary/lunar and the 15" better again.

 

[dweller25]

1 hour ago, jetstream said:

I remember asking a similar question as the OP and your response was the same- and absolutely correct (thanks BTW). The 10" dob is Vg for planetary/lunar and the 15" better again.

 

Your welcome sir 👍🙂

[bluesilver]

Thanks for relies,   pretty well answers most of my long questions.

It was appreciated.

Thanks.

 

[Waldemar]

Don't forget that longer fl telescopes, which are better for planetary vieuwing, also need a sturdier (better) mount, because small movements have a huge impact... 

[Louis D]

6 hours ago, Waldemar said:

Don't forget that longer fl telescopes, which are better for planetary viewing, also need a sturdier (better) mount, because small movements have a huge impact... 

Or a step ladder to reach the eyepiece in the case of large Dobs.  An f/5 is considered a longer focal length by today's Dob standards:

Whereas a 28" f2.7 does not require a step ladder most of the time:

[bluesilver]

The shorter focal length looks more user friendly,  but looking at more of something you don't have to design and build like in the last photo.

I guess it is finding a happy spot in between how tall you want the Dobsonians,  i think around 16 inches would be getting near the limit without needing a ladder.

 

[Louis D]

2 hours ago, bluesilver said:

The shorter focal length looks more user friendly,  but looking at more of something you don't have to design and build like in the last photo.

I guess it is finding a happy spot in between how tall you want the Dobsonians,  i think around 16 inches would be getting near the limit without needing a ladder.

 

My 15" f/5 is just usable without a ladder up to about 75 degrees altitude for this 5' 8" old timer.

[johninderby]

Thing to remember the best telescope is the one you will actually use not one you can’t be bothered dragging out and setting up so before getting the big scope think about how much it will be used. Big scopes come up for sale quote often with the seller saying hardly ever used.

[Sunshine]

I use my 150 Skywatcher Mak for planetary and Lunar fun, you take one look at Saturn through a 180 Mak and you won’t look back, love the scope, I’ll be buried with it.