Viewing the planets

[milkyjoe]

Hi all.

Sorry if this is old ground, but...

I was wondering what the best type of scope is for viewing the planets are their moons. I can't help wonder if I have the wrong type for the job, my f/5 refractor is OK, but being a fast scope does not give me the detail I want. Obviously there are ways to increase the focal ratio such as using a barlow lens, but the main problem with them is that the more magnification they provide, the less light and detail they show.

Would I be better off with a mak cas, with these being a much slower scope they should provde the high mag detailed views without the aid of a barlow that I am after?!

Thanks in advance.

Richard.

[John]

I think you are thinking along the right lines - a long focal length scope is more suitable for planets and a maksutov-cassegrain is ideal, portable and relatively affordable. Slower (eg: F/10) refractors are also good but they are harder to mount steadily because of the tube length.

The problem with the fast achromatic refractor that you have now is i) the inevtiable chromatic abberation does obsure planetary details somewhat and ii) you need very short focal length eyepieces or a powerful barlow to get to high power.

[russ]

Totally agree with John, a Mak Cass would be your best bet. You can pick up the 90 tube quite cheap and mount it happily on your existing EQ1. It may have less aperture than the Startravel 102 but will comfortably out perform it on anything solar system related.

Funny you should mention your Startravel though. I was out with the kids last night for a totally unexpected obs session. We were observing Jupiter with our selection of scopes. I bought my youngest a Startravel 80 as its small and lightweight. Never really had a decent view of the planets with any of my Startravels but he's happy. But i remembered last night that i had bought a 'fringe killer' filter from the Astroboot and never used it. Wasn't expecting much but ended up being quite surprised. It couldn't clean up all the chromatic abberation but it had a good stab at it. And with good focus we had a much better view of Jupiter and a surprising amount of detail. Although still nowhere near as good as the Orion Optics 150 f5 newt.

[russ]

I notice there is a Skymax 90 in the Astroboot for £20. Missing the mounting foot, finder shoe and focus knob. But a mounting foot would only be £6, the finder shoe £5 and there is plenty of ETX focus knobs in the astroboot for a few quid. No idea if they fit but for £35 (ish) you could have a Skymax 90.

http://www.scopesnskies.com/AstroBoot

[milkyjoe]

Thanks for that Russ.

OK, I've got the ota, 8x20 2 hole finder, qr finder shoe and sw focuser knobs. I can't find the mounting foot! I take it this is what I need to attach the ota to my eq1 mount, yes? :-\

Regards

Richard.

[russ]

A medium dovetail would do. Just drill two holes in the tube and bolt it on. Although getting it onto the EQ1 would then be the problem. I'll have a look round for some ideas.

[brianb]

Don't forget that you also need aperture to resolve detail.

IMHO there is no doubt whatsoever that the best "bang per buck" for planetary / lunar viewing is delivered by a longish focus Newtonian scope - mounted on a equatorial mount with manual slow motions to make it easy to track the objects as the skate across the sky at highish magnifications. Something like the Skywatcher Explorer 150 PL is ideal for the beginner, not expensive, reasonably portable and big enough to show real detail on Jupiter, Saturn and Mars (the phase of Venus is very easy but the surface markings are very difficult for any scope, whilst seeing surface details on Mercury, Uranus or Neptune is out of range of a beginner's scope).

Newtonian reflectors have essentially no aberrations close to the optical axis (which is where you observe planets) and the longer focus types, working at f/8, are easy to collimate and allow budget eyepieces to perform well ... unlike the f/5 scopes which demand expensive, high quality eyepieces to achieve their performance potential.

[russ]

Rather than a mounting foot, another option maybe some tube rings? The scope can then be bolted straight to the EQ1. Not sure which size tube it is though

[milkyjoe]

Thanks Russ and Brian.

I quite like the idea of a mak due to it's portability, and it means I can take it on holiday with me. The ota is the 90mm version as you stated previously Russ. Can you buy tube rings in this size, I assume you can? lol

Richard.

[russ]

You can buy 90mm tube rings but i'm not sure the Skymax 90 tube wouldn't be closer to 100mm. In which case you already have a set of rings on your Startravel 102.

One thing i didn't notice but have now i re-read the ad, it's missing the 1.25" visual back as well. Not sure how easy it would be to track one down. There's probably a good chance people who have upgraded their Skymax's to a SCT thread have the original visual back knocking about and so maybe worth posting a wanted ad.

But something to consider because pretty quickly the cost will jump from £20 to £70-80.

[milkyjoe]

Hmm... I can't see in the ad that the visual back is missing?! lol

[russ]

It's the last part about the eyepiece adapter being missing