Increasing power from an 8mm...worth it?

[SacRiker]

Last night I was able to get some great views of Jupiter with my 8mm EP. Would the views in my scope be even better with a 4 or 5mm EP? I have the XT8 Dob.

[g30rg313]

I don't see why not.  I have managed 250x magnification on my scope viewing Jupiter.

[g30rg313]

Just now, g30rg313 said:

I don't see why not.  I have managed 250x magnification on my scope viewing Jupiter.

Probably safer to stick to 5mm ep though rather than push it too far.  Unless you're feeling adventurous haha

[dweller25]

It depends on your seeing condition, here in the UK I rarely go above a 5mm in my 8" F/6 as seeing does not support anything higher.

[SacRiker]

I'm too inexperienced to judge the seeing conditions...but it was mostly crisp in the 8mm. If I get a 5mm, does anyone have good recommendations? I was looking at the Celestron X-Cel since I have that in a 25mm and it seems good. 

[Jimtheslim]

I have 10" dob, f/4.7. I've recently had decent views of Jupiter but with my 6.4mm plossl which seemed a lot better than my x-cel 8mm. You could go for higher mag, but I think you'll have to pick your eyepiece carefully and be content with only using it very occasionally. I find myself going back to my 12.4mm plossl for the most pleasing views which is only around 100x mag. I had been tempted to go down to a 5mm, but knowing what the seeing is like most of the time I am going the other way and looking for a nice 10mm.

[Paul73]

The 6mm is my most used planetry eyepiece in my fl1200mm Dob. If you get out of town with some nice steady air, a 5mm would work well (this is very rare in the UK!).

Paul

 

[SacRiker]

3 minutes ago, Paul73 said:

The 6mm is my most used planetry eyepiece in my fl1200mm Dob. If you get out of town with some nice steady air, a 5mm would work well (this is very rare in the UK!).

Paul

 

What 6mm do you have?

[Charic]

XT8 f/5.9 call it f/6 so a 6mm will match the capability of your scopes aperture providing a 1mm exit pupil at 200x power, going to a 12mm although a  lower power, should provide better detailing from a 2mm exit pupil! All based on the telescope's numbers?

I have pushed to 5mm (240X)  and even 3.2mm (375) on the Moon but you'll need to track quicker and have good or perfect seeing conditions at the higher powers.

All very well going higher powered, but you`ll soon loose/degrade the detail and contrast below a 6 mm, unless you up the stakes with more aperture!

[brantuk]

Agreed - I'd be tempted to push it with a 4mm if you get clear skies - no reason why an 8" won't go up to 300x in good seeing. You'll soon know what "seeing" is once you've had a go with higher mags. The best seeing is in the still cold of winter when it's dark and the air is clear and transparent.

What ruins it is heat hazes when Earth gives off heat and makes the target appear to wobble. Or thin whispy high level cloud which blurs things a bit. Looking a the horizon you have to make your way through denser atmosphere than straight up. And on a humid day when there's a lot of moisture in the air everything goes blury in the eyepiece.

You'll soon pick it up though the more you get out with the scope - but I'd certainly try a 5mm or 4mm in your neck of the woods. Over here - I can count on one hand the number of times I've gone above 200x in 6mths.

 

[SacRiker]

10 minutes ago, brantuk said:

What ruins it is heat hazes when Earth gives off heat and makes the target appear to wobble.

Thanks for the info. I did notice there were a few times last night when I noticed this wavy motion in the air. Here in my area of California we are entering the HOT season (gets to 105 at times during midday) and so I could see this becoming a real issue.

[iPeace]

I have the wrong type of scope to be of any real help, but by coincidence the most crisp views of Jupiter I've had were with an 8mm eyepiece... I did of course downshift via 6mm to 4.7mm, greedy for more detail, which I got, but at the expense of some of that lovely crispness...

[Charic]

.....drop a coin in the deep end of a swimming pool and it almost disappears due to the currents and waves, but check in the early hours of the morning when its flat calm, and you'll probably determine which side of the coin your looking at?

Looking aloft is no different, but not only that, your  now magnifying everything upto  200x more than your eyes  would normally see when viewing certain objects .  The thermal currents in the air, the density, the dust, thin cloud, there's so much against us I   often  wonder why I try to look in the first place, but once you have seen that fleeting moment of calmness, and sometimes its only  for a few seconds during your whole session, and Jupiter pops up in perfect focus, pin sharp detail,  a pencil point dot shadow of the Moon Io ( pronounced eye-oh!) then you will know you have had perfect conditions. I`m nearly 3 years here, and have witnessed Jupiter in all its glory only ONCE!. patience, timing and the right conditions really do pay off.

When observing Jupiter I'll settle for  6, 8 or 12mm, all depending on which one gives me the best detail. The Starguiders I have give me 60° afov and better eye-relief for my eyes against a previously loaned and tested 8mm TeleVue Plossl.
If you were to 2x Barlow your 15mm TeleVue, you may notice/experience  a little more eye-relief at about 10mm,  this alone can help visually,  its  also more comfortable to use than the 8mm EP with its  6mm eye-relief.

Its the little things that can sometimes make the biggest difference,  but only your eyes can discover this. 

Edited May 15, 2016 by Charic

[iPeace]

Aaaaaaaaaaaaaaaaaahhh-men!

[scarp15]

Quite as mentioned, a 5mm and 4mm will be useful to you but work your way there incrementally and make your next purchase a 6mm. A 6mm and 8mm will be highly complementary with your f6 8" dobsonian and this new addition will receive a good deal of use on a variety of subjects. A high end option of course will be a 6mm delos.

[dweller25]

I am a planetary observer and my most used eyepieces (in order) in the 8" F/6 are :-

1. 6mm TV Radian (x200)

2. 7mm Pentax XW (x171)

3. 8mm Vixen LVW (x150)

4. 5mm Pentax XW (x240)

Edited May 15, 2016 by dweller25

[John]

It's worth noting that, generally, Jupiter does not respond as positively to higher magnifications in the same way that other targets such as Saturn, Mars and the Moon do.

I think this is due to the nature of the features in Jupiter's atmosphere that we are trying to see which are contrast variations rather than sharp shadow / light differences.

Under really good conditions the giant planet can give more at really high powers but generally I've found "lifting off the gas" a little delivers better feature definition.

Even with my 12" scope 180x-220x is usually optimum for Jupiter.

Edited May 15, 2016 by John

[Piero]

Don't forget to properly collimate and cool down your telescope. These two are critical when medium/ high powers are used. Even with the perfect seeing and very good eyepieces, a telescope won't perform well if not collimated and cooled. 

You can test your seeing on double stars (e.g. you should see distinct concentric diffraction rings when defocusing with a high power ep - this is also a test for collimation btw) or on the Moon (the surface is steady at high powers, therefore no wobbly). A 6mm will be very useful most of the time. A 5mm or a 4mm will be more useful with Saturn or Mars than Jupiter. I would get a 6mm now and then if you think your seeing is good, a 5mm later. If you don't wear spectacles and don't mind a 50 deg fov, a nagler zoom 3-6 might be another option. I never looked through one, but many people seem very happy with it.

[jetstream]

This zoom and the barlow might work well.

https://www.firstlightoptics.com/baader-planetarium/baader-hyperion-zoom-eyepiece.html

[SacRiker]

Thanks everyone for the information. I'm going to likely go with the 6mm...I'll report back on how it all works out. I'm really looking forward to getting some good views of Saturn in June (can't stay up until 2am at the moment!).

[Jimtheslim]

6 hours ago, SacRiker said:

Thanks everyone for the information. I'm going to likely go with the 6mm...I'll report back on how it all works out. I'm really looking forward to getting some good views of Saturn in June (can't stay up until 2am at the moment!).

which 6mm are you going for?

[Paul73]

17 hours ago, SacRiker said:

What 6mm do you have?

I have the Vixen SLV 6mm. It is only 50° Fov. So plenty of nudging needed, but the clarity and contrast are top rate. They are about £100 new. 

I did consider an upgrade to a  Delos (a range that I love). But the general consensus amongst the knowledgeable SGL folks was "why bother?".

Paul

[glowjet]

Often regarded as one of the best eye pieces for planetary work were the Orthoscopics, you may pick up a s/h 6mm of the Circle T brand to try, or one of the Baader MC, although discontinued, still highly regarded, but seem to be as rare as rocking horse droppings to get hold of nowadays

[t0nedude]

With my Vixen Fluorite, my usual high power on Jupiter was 5mm (184x) I only used to go 300x or more when I was trying to pick out moon transits, to resolve the discs. At that power I usually lost some details on Jupiter though..unless the seeing was fantastic.

Edited May 16, 2016 by t0nedude

[Louis D]

I've been using a 5.2mm Pentax XL for nearly 20 years now for high power views, but it's way too much power for Jupiter.  Low contrast details just "mush" together.  I prefer to back off to a 10mm Delos.  If I go with my much larger dob, I can get to higher powers, but at the same exit pupil.  There's something about the 1.7mm to 2mm range that works best for Jupiter.

My 7mm Pentax XW isn't much better on Jupiter than the 5.2mm XL, either.  I've yet to find its object niche.  Good eyepiece, but not the best for any object that I've found so far.

I do use the 5.2mm on globular clusters to help break apart their cores.  They look like slowly twinkling sparkles of light most nights.  I also use it on the moon to observe the smallest features my scope can resolve.

I also have a 3.5mm Pentax XW, but that is just too much power for the focal ratios I have.  The exit pupil is around 0.6mm which just shows the numerous floaters in my eyes quite well.  I do occasionally get a good view with it, so I'm holding onto it for now.

Look for used Vixen LV eyepieces.  People are dumping them for $60 to $75 here in the states, yet they are just as sharp, well corrected, high contrast, and glare free as the XL/XW and Delos in their 45 to 50 degree fields of view with 20mm of usable eye relief.  They are also available in a wide range of focal lengths below 10mm.