18 replies to this topic

[Mike Hosea]

Eye relief for Plossls is about 0.7 times the focal length of the eyepiece. So your 25mm probably has about 17-18mm of eye relief, and your 10mm Plossl probably has about 7mm. Note that if you use a Barlow to "create" a shorter focal length eyepiece from a longer one, the eye relief of the eyepiece is maintained (or increased just slightly in some cases). So if you had a 2.5x Barlow, your 25mm and the Barlow would make a 10mm replacement with about 18mm of eye relief. Or you could buy an 18mm orthoscopic and a 2x Barlow. There are so many possibilities now, it's difficult to know where to begin.

[Tom L]

Jean, were you uncomfortable with the 25mm plossl or only the 10mm? If you were fine with the longer eye relief eyepiece, then you can begin to understand your comfort level. Remember that your son will have a different comfort level than you do. Also, do you wear glasses and if you do, do you use them when looking through the eyepiece?

[Derek W]

Yes, you will be able to see color in Jupiter...

Usually it's kind of a pale almost salmon like color. You should be capable of seeing the great red spot and all that fun stuff.

You see more detail and a larger disk the higher you go magnification wise, naturally. Seeing conditions usually limit how much magnification the planet can take.

If you spent most of your time viewing Jupiter with the 25mm piece, then it would seem smaller, and with less detail available.

It's the same way with my 10inch dob. (in fact, mine brings in too much light at times, thus making Jupiter too bright and not well viewable - sometimes a 6 inch will out perform larger counterparts)

Anyhow, look at barlows if you want to continue using plossls. There are eyepieces out there designed with much more eye relief, though they can get pricey quickly depending on what you're looking at.

[matt]

Jean, are you from France or Canada or Belgium or somewhere?

I second the question about the eye relief on different eyepieces. You should be able to look ok through the 25mm whatever happens. Having trouble looking through a 10mm can be frustrating, yes.

The barlow is a solution; another which I prefer (it avoids the handling of the barlow, etc) is long eye-relief eyepieces. They come in all flavor in prices, from the wide-field Televue Radians ($240 new, ouch) to the Vixen Lanthanums (about $100) to budget items such as the Celestron Xcel, Orion ED... I think Skywatcher also makes some (all the budget ones seem to come frmo the same Chinese source). They're not as sharp as the Radians but worth a try, they run between $50 and 80. I used several
Vixen Lanthanums, and maybe they were not as sharp as the Radians, but they definetely were the most comfortable eyepieces I've ever used. As usual, I suggest you pick a used one on Astromart to try - it will cost you less and if you don't really enjoy the eyepiece you can put it back for sale without losing much money.

[Craig Simmons]

The Vixen Lanthanums are good EPs. The 6mm I use has 20mm of ER. A little bit narrower FOV than plossls though. The stock 10-9mm EPs that come with scope aren't that great. I never use mine except with an cheap ST80 scope I use for terrestial viewing.

The size of Jupiter depens on the EP you're using. You want an EP in your scope that gives you 180X or more for a really good view which is a 6mm or a barlow/EP combination that produces the same magnification. A barlow will preserve the ER of an EP.

You might want to look at wide angle EPs like the Stellarvues. Very good ER. At f/8 you there are quite a few WA EPs in shorter focal lengths out there you could use.

http://www.stellarvu.../eyepieces.html

[erik]

color is very subtle on all astronomical objects, so don't expect to see brilliant, vibrant colors. you have to really tease the color and detail out. a barlow sounds like your best bet for getting a more comfortable view. plossls have poor eye relief in the shorter sizes, and the 10mm that came with your scope isn't the best quality, although the 25mm should be fine. certain types of ep's also have longer eye relief, but blacking out can be a problem with some of those, and i find that more annoying than short eye relief. start with the barlow and see how that works for you...

[Victor Kennedy]

Jean, the Pentax XLs and the new XWs (so I hear; I only have experience with the XLs) have very good eye relief. They are also excellent in other respects.

[dgs©]

I believe Vixen Lanthanums and Orion Lanthanums are the same critters, check on pricing between the 2 before buying. They are likely a good choice, next higher probably Radians. I think you should see some color in the two darker belts on either side of Jupiters equator. It won't be bold color... it looks kind of rusty in my 8" scope. Please note here... the longer you look at an object in the eyepiece, the more you will eventually be able to see detailwise. The "Great Red Spot" hasn't been too terribly red in recent times... it's more a salmon or pinkish and hard to distinguish. Also, the GRS isn't always facing Earth... Jupiter rotates once in something like 10 hours vs. our 24. So you have to look on the right day in the right time window to see the GRS. Check skyandtelescope.com for more detailed info on when you can see the GRS. It also shows the moons and which one is who and when they (or their shadows) will pass across the face of Jupiter. That is really neat to watch.
I believe your understanding of the top three factors is spot on.
Keep looking up... you will see lots of amazing things.

[Derek W]

Aperature is much much more important for viewing DSOs.

It isn't nearly as important for planets. At 6inches of aperature, you'll do just fine on jupiter.

Magnifications and eye pieces make a lot of difference in the way the planet will appear. I hear you can get up to 175x pretty regularly..and after that, it starts getting more dicey. (it is true that smaller aperatures don't have the high end magnification abilities of larger aperatures - but you very very rarely get near that max)

[pollux]

I use Skywatcher's Ultra Wide Angle series of eyepieces


4 focal length - 20mm, 15mm, 9mm, 6mm (I have ALL of them)

Reasonable price (45 CDN - 55 CDN each)
Good view angle (66 degree)
Good eye relief (20mm approx)

[Tom L]

Pollux, do you get any kidney beaning (blackouts) with any of these EPs?

[erik]

since i'm assuming that jean's scope is a newtonian, collimation could also be an issue. also, the scope needs to cool down a bit before viewing planets at high power. even a 6" mirror will probably need at least a half hour to cool down, more if it's very cold outside. the orion shorty plus or celestron ultima barlows are very good, and reasonably priced at around $70. for ep's, the ultima and orion ultrascopics are the best planetary ep's for the price (around $85), and offer better eye relief than plossls, and without the blacking out that is so common with the "wide field" ep's, such as the celestron x-cel, orion epics, etc. the 7.5mm ultrascopic is one of my favorites, and would give you 160x in your scope.

[pollux]

Pollux, do you get any kidney beaning (blackouts) with any of these EPs?

Yes, the 9mm one has the most serious blackouts. And you need to keep your head moving to find out the seeing spot.

I used to have a few Vixen long eye relief eyepieces (LV series) and they too have the same problem.

I guess all long eyerelief eyepiece suffer this problem

[F.Meiresonne]

Yes, but the LV 15 mm has it only very slight. I guess that the kidney beaning effect gets worser as the barrel gets longer, is that so or am i wrong in that assumption?

[pollux]

Oh, forgot to mention the Vixen LV eyepieces I had are 4mm, 2.5mm. They all are tall

[Mogster]

I've got the 9mm Vixen LV and I really like it. It seems very easy to look through and comfortable to use. The eye positioning seems fairly non critical.

If I have other people looking through my scope I stick the LV on, thy never fail to see what I've got lined up. It surprises me that people say the LV's are hard to look through, I've never found that.

[F.Meiresonne]

I've got the 9mm Vixen LV and I really like it. It seems very easy to look through and comfortable to use. The eye positioning seems fairly non critical.

If I have other people looking through my scope I stick the LV on, thy never fail to see what I've got lined up. It surprises me that people say the LV's are hard to look through, I've never found that.

On the contrary, the LV's are the easiest to look trough!!! On star party's they'll do a great job!