help for a complete beginner!

[Qualia]

Shavy,

For Lunar work, most magnifications offer up something to be amazed by. Low powers help frame the Moon, mid-range frames craters and seas and mountain ranges and high-powers help tweak out subtle features like terraces, tiny craters, ray grazes etc.

For Jupiter, I typically use mags between 140x to around 200x. I have gone to 250x on a number of occassions but generally find I'm working between 180x to 200x in the 10" and between 140x to 160x in the 4".

For Saturn - Again I have found 140x to over 200x useful mags to play around with. You can go higher, but a lot will depend on the night's atmospheric conditions.

For Mars, I figure Jupiter is about 3x the size of Mars and to see Jupiter nicely is, say, at around 200x which means that for me to get a 'similar' view of Mars I need 600x. Well, I'm just not going to get that kind of viewing quality. So, I figure a compromise is needed, say, around 250x which still means seeing conditions will have to be very good. As such, I haven't found Mars a particularly giving planet..

With that said, now comes a word of caution. A 5" f/5 is not an ideal planetary scope. Being of such a short focal length, it relies on very short focal length (FL) eyepieces to gain significant magnification. A longer FL telescope allows one to use longer FL eyepieces, which in turn would give one more eye relief making viewing a more comfortable possibility.

As you'll appreciate, magnification is equal to the telescope's FL divided by the EP's FL. So, if I wanted to enjoy Jupiter, for example, at around an average night's viewing of 140x to 160x in the 5" f/5, I'd need an eyepiece of around 4mm to 4.5mm. I often view Saturn around 160x to 200x, so if this were the same for you, we'd need FL EP's around 4mm to 3.3mm.

I know that other members like Ronin, for example, will have a lot more experience here, so it would be great to hear what is said, but having never owned a 5" f/5 and looking solely at the numbers,  I'd recommend either:

• don't buy any new eyepiece and save for a bigger aperture scope (6" plus is where I feel planetary gets interesting).
• a zoom eyepiece of decent quality of between 3-6mm (expensive option).
• a decent Barlow which in effect helps double your EP collection whilst giving you the choice of buying a little longer FL eyepiece (say an 8mm giving you a hand in viewing DSOs and lunar work) and retaining its longer eye relief;
• a 60º field EP of around 4mm which due to its wider field will be easier to track your object and finally
• an ortho of around the same focal length. 

Just looking at the numbers, I figure that if you want to do some serious planetary viewing, you will be pushing your system and eyes. You have a beautifully crafted wide-field scope and these telescopes can look at planets all the time but I think it is always helpful to the soul and mind to have reasonable expectations of what is realistically possible.

Hope this helps a little.






 

[shavy65]

Thanks for the info Rory.

Qualia, thank you, this info is appreciated. I`m most interested in planetry observation, after reading your advise I realise my scope has it`s limits. I`d still like to utilise my scope to get maximum potential.

I see a 4mm (x163 mag) may be pushing it for my poor scope (unless as you say there`s perfect conditions) ....I do have a descent x2 barlow though so this was leading me to purchase either a 7/8mm EP, which I could barlow on the odd occasion if possible,

is there any obvious holes in my plan or does this sound feasible?

So, going on everyone`s advice I think I`v narrowed it down to either :-

1.25" 7.5mm 58 Degree TMB Planetary II eyepiece    £40

OR

1.25" 8mm BST Explorer Dual ED eyepiece Branded "Starguider"     £49

 Anyone any thoughts on these choices?

Thanks again

[rory]

Shavy if your quite new to the stargazing hobby you'll find as I did that either of those e / ps would do you well. Skies the limit ( skies unlimited) use to let you try and send it back if you found it unsuitable ! I don't know if that is still the case , perhaps someone else can confirm.

I

[Helite]

Shavy if your quite new to the stargazing hobby you'll find as I did that either of those e / ps would do you well. Skies the limit ( skies unlimited) use to let you try and send it back if you found it unsuitable ! I don't know if that is still the case , perhaps someone else can confirm.

I

Yes Alan will still allow you to take them and try and send back if you are not happy.

Never tried the TMB planetary eyepieces but have used the ones that were branded "TMB designed" and sold under various other names but think I prefer the BST explorers/Starguiders.

[shavy65]

Thanks for advice people. I`ve went for the BST Starguider from Skies unlimited on ebay. Looking forward till delivery....and a cloudless night!
Cheers,

Shavy

[Swedeman2013]

Keep in mind Jupiter can be so bright from the sun that details tend to get washed out, I find a blue filter helps and getting that " sweet spot" in your eyepiece is critical.