Telescope Question

[DanDorsh]

My girlfreind and I have recently gotten very intrested in Astronomy and have some questions about our telescope and its capabilities. We are getting used to where certain planets and stars are in the sky, but we can't get very good views of the planets with our telescope. We get them into focus but want a better image. We are using a Meade EXT-70 and have been debating buying a barlow lens for it. The part number is #124 2X Barlow Lens 1.25 Inch for ETX 70. Can any one tell us how much of a difference it might make by getting this or if we should buy something else instead without getting a new telescope? The eye pieces we use are a 25mm and 9mm. The info about this says it will double our power. If this is true how well (roughly) should we expect to see the planets with this telescope?

[crosscountry]

this link my help


http://www.weasner.com/etx/buyer-new...etx70_acc.html




PLEASE, PLEASE do NOT buy a barlow lens. If you think viewing now is inadequate, you'll really dislike the barlow.


at 70mm, your scope is set to see bright planets and the moon. with a solar filter you could even observe the sun.

To view the planets best, look on a dry dark night away from the city lights. (that also makes for a good mood with your girlfriend )

if you live in a place that's dusty or hazy often, wait until after a rain. Then the atmosphere is cleanest and best for viewing.

Really though, the best time to observe is after midnight, when the thermal pockets of air have subsided. unless you live in the city, then they never go away.

[Maksutov]

Welcome to the BAUT!

(hmmm, first time I've typed that...)

Anyway, you should consider upgrading your eyepieces. My understanding is the eyepieces supplied with the Meade 70mm are marginal. Try Googling for Plössl and other eyepieces mentioned in the link provided by crosscountry.

A good Barlow will not improve a poor eyepiece.

Plus you need to remember your objective is only 70mm in diameter. There's only so much one can see with a small 'scope.

Meanwhile, may you have clear, steady skies!

[Yorkshireman]

Agree with crosscountry and Maksutov, your money is better spent on a Plossl eyepiece with a smaller focal length - say a 6mm, which will deliver you 59X - that getting a barlow that will simply magnify the imperfections in the supplied eyepieces. You've got a great telescope, so it's worth spending on an eyepiece that will do it justice.

In terms of images, you might be able on a good night - at the limit of the capabilities of the telescope - to see the Cassini division in the rings of Saturn. Spotting the gap between the rings and the planet itself should be a doddle. You should be able to spot the equatorial cloud bands of Jupiter as well.

[crosscountry]

even a 6mm may be too much magnification. But that's my opinion. My 6in Dob loses resolution at that magnification (1200mm focal length/6mm = 200Xmag)

My 10mm is usually the smallest with which I observe. The moon is the only thing I can see well with the 6.4mm

[aurora]

Might also ask which planet(s) you've looked at so far.

With Mars rising in the early evening now, and getting brighter, perhaps that is the planet you were looking at. Be aware that Mars is small, and you will never see much detail on it (you have to train your eye to get much from viewing it, takes practice and patience).

I've seen lots of people who were disappointed the first time they looked at Mars with a telescope.

[DanDorsh]

Thanks for everyones help on this. So far we have seen Venus and Jupiter in the early evening, Mars later at night, and a little while back we saw Saturn. I will look into getting a Plossl eyepiece. I think maybe I was expecting to see much greater detail than is possible through this telescope or I wasn't in focus. Will I have a chance at seeing the polar ice caps on Mars or not? Do you think this telescope is capable of seeing Uranus and Neptune? Once again, thanks for helping us out. Astronomy has always been something I've wanted to learn and ever since I graduated from college, I have taken it up as a hobby. We still have much to learn.

[DanDorsh]

Which one of these Meade series 4000 eyepieces would be best sutied for me to view planets in the greatest detail. The link cross country sent me said that user liked the 26mm. Yorkshireman said to go with a 6mm and cross country said that might be to much. What is everyones opinion between these eyepieces and what difference should I expect between them when actually viewing? Once again, THANK YOU SO MUCH FOR THE HELP!!!

http://www.meade.com/catalog/meade_4...es_4000_02.htm

[Yorkshireman]

DanDorsh, what's your focal length? My answer was based on thinking your telescope had a 350mm focal length like the ETX-70 in this ad here. If that's right, you should be able to go up to even a 4mm Plossl without getting to diminishing returns from your 70mm objective lens. You'll get diminishing returns above about 140X mag - basically magnifying the blur.
crosscountry's scope has a longer focal length, so the same eyepiece in his scope will be delivering a lot higher magnification. (Apologies if I'm telling you what you already know here, by the way.)
You should be able to glimpse the Martian polar caps near the opposition in October. It will depend very much on the seeing conditions that night.
Uranus should be spottable, I don't know about Neptune.

[crosscountry]

yep, Uranus, if you can find it should be visible. It's a green circle among points. Good luck finding it; it took me quite a while.

[DanDorsh]

How much better quality are these Plossl eyepieces than the ones shipped stock with my telescope? I do have the specs yorkshireman specified so my choices are listed on this link:

http://www.meade.com/catalog/meade_4...es_4000_02.htm

You're pretty sure that if i buy the 6.4mm Super Plossl it will work well? The author on this site said his best results came from:

#140 - Meade Instruments Series 4000 2x Apochromatic Barlow Lens 1.25"
and a
Meade series 4000 plossl eyepiece - 26mm 1.25"

http://www.weasner.com/etx/buyer-new...etx70_acc.html

Do you think I should buy 6.4mm eyepeice and no barlow lens? Sorry if I am sounding repetative. I just don't want to waste money on accessories that will be blurry. Thanks.

[crosscountry]

In my experience, the barlow was a waste of money. But we have different telescopes with different focal lengths.


Of course the barlow is relatively cheap (not the meade version).

They claim it doubles your eyepeices. that is a true claim.. the 26mm will look like a 13mm and so on.




Think about this, how much do you want to spend...? What are you trying to see? Put those two factors together and buy what fits.

[DanDorsh]

I just want to see the cloud patterns on Jupiter and the rings of saturn as clearly as i can for this telescope. The money is not really an issue.

[Maksutov]

Thanks for everyones help on this. So far we have seen Venus and Jupiter in the early evening, Mars later at night, and a little while back we saw Saturn. I will look into getting a Plossl eyepiece. I think maybe I was expecting to see much greater detail than is possible through this telescope or I wasn't in focus. Will I have a chance at seeing the polar ice caps on Mars or not? Do you think this telescope is capable of seeing Uranus and Neptune? Once again, thanks for helping us out. Astronomy has always been something I've wanted to learn and ever since I graduated from college, I have taken it up as a hobby. We still have much to learn.

Uranus is a marginal unaided-eye object. Neptune can be seen in astronomy-grade binoculars. Therefore both planets will be readily visible through your 70mm scope. Pluto is out of reach for you, due to its faintness. You would need an objective of about 200mm minimum to have a chance at glimpsing it.

In general re Uranus and Neptune, the key to finding them is knowing where they are and the star patterns around them. There are many online astronomy sites that will provide you charts of the various star patterns with which those two planets may be found.

One of these sites is Heavens Above.

Here is its chart re the current location of Uranus.

Here is where Neptune is at.

Heavens Above is also a great source for predicting satellite sightings. Give it a try.

[aurora]

As to whether you had the scope in focus, were you able to get the stars to appear as points?

If the stars appear as small points, then the fuzzyness in the planet is due to the Earth's atmosphere or the optics being used.

[Yorkshireman]

How much better quality are these Plossl eyepieces than the ones shipped stock with my telescope? I do have the specs yorkshireman specified so my choices are listed on this link:

http://www.meade.com/catalog/meade_4...es_4000_02.htm

You're pretty sure that if i buy the 6.4mm Super Plossl it will work well?

I'm reluctant to give firm recommendations simply because I don't have a Meade ETX-70, I haven't personally tested out these eyepieces. On a clear night you find me peering through a Helios 4.5" reflector. I'm going really on general principles for what a telescope of your spec should be capable of.

But in my experience, manufacturers put cheap eyepieces in with their telescopes. You probably have what's called an MA eyepiece, which is OK, but a Plossl is a superior design (it's also a bit more expensive). You get what you pay for, a Plossl of the same focal length as your existing eyepieces will give you a better image quality.

It's good to have a range. If you already have 9mm and 25mm eyepieces, consider getting a 6.4mm for high magnification planet spotting. Again, you'll find me swapping and changing 3 eyepieces quite often to get different views of the same thing.

This page gives a pretty good explanation of tthe different types of eyepieces you can get. Choosing Eyepieces for your Telescope .

[DanDorsh]

I Want To Thank Everyone So Much For All The Information You Posted To Help Me Out. I Have Alot Better Of An Idea To What I Should Get. Thanks Again.

[Charlie in Dayton]

Ballpark rule of thumb...

Usable magnification = aperture X 2 (if in mm) or 50 (if in inches).

The ETX-70 is a 70mm aperture, therefore max usable magnification = 140, which would be a 2.5mm eyepiece.

The more utilitarian formula takes into account bad seeing conditions...

Usable magnification = aperture X 1.5 (if in mm) or 38 (if in inches)

Usable magnification here comes to 105x, attainable with a 3.5 mm eyepiece. Since these are few and far between, a 4mm eyepiece gives you 88x.

Your problem here is not magnification, it's aperture. There are binoculars out there with more than a 70mm aperture. You want a bigger light bucket, to allow you to view dimmer objects. The narrow aperture isn't compensated for with the focal length (f5).

Something of the Dob persuasion, 4.5" or more to start with, is suggested.

You might have to do a little diggin' and scratchin', but those Celestron eyepiece kits are still out there...
4 / 6 / 9 / 15 / 32 mm Plossls, a 2x Barlow, six eyepiece filters (#12 Yellow, #21 Orange, #25 Red, #56 Light Green, #58A Green, and #80A Blue, along with a neutral density Moon filter). I rounded my set out with a 25mm, a 40mm, and a variable polarizing filter.

The general responses here make sense...don't Barlow a cheap eyepiece. Get a better one.

If affordable, get a larger aperture scope.

Shorter focal length = wider field of view = views of large areas of sky.

Longer focal length = narrower field of view = planets and small areas of sky...you won't get a whole constellation/asterism, and maybe not even a whole cluster.

[Titana]

Hi just wanted to give a little more help. Just in case you dont know, the apeture ( in a refractor ) is the diameter of the ( front ) object glass, or the diameter of the mirror (in a reflector), which is the light colecter. The eyepeice does all the actual magnification. The bigger the apeture the greatter is the amount of light available to the eyepeice, and a high magnification can be used. That is to say as mention by Charlie, your usable magnification would be aperture x2 if in mm and x50 if in inches. That is, 70mm x 2 = 140 (2.5mm) which means that the object will be enlarged 140 times as compared to the naked eye view. You can use a higher magnification, but the image will be so faint that it will be quite useless...

Titana....................

[dougreed]

hi, I noticed you said price is not a problem, then maybe look at some "tele-vue" eyepiece info. Definitly high $$$, but many say worth it...see-ya