10mm Viewing and 20mm Viewing !!!HELP!!!

[AstroJacob]

    Hello, my name is Jacob I love astronomy and astrophysics. I lost my old to an accident and I recently purchased a smaller telescope until I can buy a better one. I purchased the Celestron 70 Portable scope.

Before I state my problem I will list the specs of the telescope so you can help me without looking it up.

SPECS:

Optical Design Refractor Aperture (mm) 70 mm (2.76 in) Focal Length 400 mm (16 in) Focal Ratio 5.71

I have one eyepiece for it currently which is a:

- 10mm

I am currently ordering the 20mm eyepieces because I think it will resolve my issue BUT I am coming here to verify.

Whenever I try to look at planets through my telescope with my 10mm eyepiece I can see nothing but blur, until I zoom out and focus it. After that all I see is a start nothing more. I know I am looking at the planet ( Jupiter ) but I can never zoom in enough to actually see it.

Now my question is, is this because I need to have a 20mm eyepiece to see the planets? I have heard I do because it will focus the light do to the fact my telescope is so small but I want your guys help! please answer!

[RikM]

I don't think a 20mm eyepiece will help view the planets, but it may be a good idea to get one anyway. With eyepieces, the smaller the number, the higher the magnification. You can calculate magnification by deviding the focal length of your scope (400mm) by the fcol length of the eyepiece (10mm). 400 / 10 = 40x and 400 / 20 = 20x, so a 20mm will give you a lower magnification and a wider fled of view. Good for 'finding' planets but for satisfying views you will need higher magnification.

With your telescope, something around 5 or 6 mm would be good, but you will need to get your eye very close to the eyelens to look through one of those. It may be more comfortable to get a 2x Barlow lens and use it with your 10mm to increase the magnification.

Regarding your difficulties viewing Jupiter, it sounds like you don't have enough travel in the focuser to bring the eyepiece to focus. Have you got the star diagonal in place? You may need to use this to reach focus.

[AstroJacob]

Whenever I use the 10mm lense and try to view Jupiter once I focus it looks like this ( http://imgur.com/mdrtLT5) forgetting the excess space and focusing on the start bit. When I turn the focus up to try and "zoom" it just blurs out and looks all weird,

[Qualia]

If the image you've linked to is correct, it looks more like a star than Jupiter. In my small 76mm, Jupiter at around 100x looks more like this:

Just as Rik mentions, a 3" 400mm like my own 3" 480mm isn't going to be 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 gives 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 and as a general rule of thumb for these kind of smaller scopes, in my experience the aperture won't let you go much beyond 4mm or 3.5 mm.

So, if I wanted to enjoy Jupiter, for example, in you 70mm f6 at around an average night's viewing of 100x, say, I need an eyepiece focal length of around 4mm. So, just as Rik suggests, the 20mm will be a lovely finding eyepiece and the 10mm will give a little more umph but for viewing Jupiter, you should be using something around 6mm to 4mm.

If you were wanting to do planetary observations, typical recommendations for the 3" f/5 might include: i) a zoom eyepiece of decent quality of between 3-6mm ii) a decent Barlow which in effect helps double your EP collection whilst giving you the choice of buying a little longer FL eyepiece and retaining its longer eye relief; iii) a 60º field EP of around 4mm which due to its wider field will be easier to track your object and finally iv) an ortho of around these focal lengths (something which might be tricky).

As you can appreciate, a 3" f5 isn't so much designed for planetary and lunar viewing as it is for low magnification views of star fields, open clusters and larger objects like the Veil Nebula. It can also be coverted - with the necessary filters in place - into a decent white light solar scope.  Nevertheless, this does not mean you cannot enjoy viewing planets like Venus, Jupiter, and Saturn. I do it all the time with my little 76 and have just as much fun as I do with the mightier 10"  . 

If you haven't already, download Stellarium which will indicate where Jupiter is and on your next night of viewing, see what you come up with.

I look forward to hearing your report and if you have any problems, please don't hesitate in letting us know

Welcome to SGL, Jacob

[-Aldebaran-]

Correct me if I'm wrong but it sounds as if your using your focuser to "zoom" into Jupiter for more magnification.

Whenever I try to look at planets through my telescope with my 10mm eyepiece I can see nothing but blur, until I zoom out and focus it. After that all I see is a start nothing more. I know I am looking at the planet ( Jupiter ) but I can never zoom in enough to actually see it.

The zoom -in/zoom-out your mentioning is the magnification required to make the observing object larger/smaller, which is the sole purpose of different focal length eyepieces (a 10mm is twice the magnification of a 20mm for example).

You mentioned getting Jupiter focused in your 10mm, that was down to focus alteration only as you cannot increase/decrease magnification with the focuser wheel using only one eyepiece.

Your image of Jupiter looking more like a star may be due to lack of magnification and other "external factors"

As stated above , your scope has a short focal length and will require a very short focal length eyepiece to get observable magnification, which in some respects is not always manageable.

A barlow lens will aid with this in compliment with your 10mm.

[Lowjiber]

Jacob, let me reiterate a few of the points made above...

1.  You are confusing "zoom" with focus.  To "zoom", one needs a zoom eyepiece that literally changes focal length when adjusted.  With a fixed focal length eyepiece, you're "stuck" with the magnification that it provides based on the simple math pointed out above... it's either in-focus, or it's not.

2.  A fast focal ratio scope like yours (f/5.7) will never provide the kind of view(s) you seem to expect on planets.  It is much better suited to viewing wider targets (like M45)... framing the entire object in the field of view.  If you want to view planets, you will simply need a scope with a very slow focal ratio (say >f/10).  Those scopes will provide views that will meet your apparent expectations.

3.  Buying a 20mm eyepiece, while nice to have, will not "solve" your problem.  Period.

Respectfully, and wishing you clear skies...

[AstroJacob]

Thanks guys! I appreciate the feed back. If you guys know any good scopes I can buy because I have a $500 budget saved up from working. If you can list any nice telescopes I could purchase for $500 or less please do!

[LukeSkywatcher]

    Hello, my name is Jacob I love astronomy and astrophysics. I lost my old to an accident and I recently purchased a smaller telescope until I can buy a better one. I purchased the Celestron 70 Portable scope.

Before I state my problem I will list the specs of the telescope so you can help me without looking it up.

SPECS:

Optical Design Refractor Aperture (mm) 70 mm (2.76 in) Focal Length 400 mm (16 in) Focal Ratio 5.71

I have one eyepiece for it currently which is a:

- 10mm

I am currently ordering the 20mm eyepieces because I think it will resolve my issue BUT I am coming here to verify.

Whenever I try to look at planets through my telescope with my 10mm eyepiece I can see nothing but blur, until I zoom out and focus it. After that all I see is a start nothing more. I know I am looking at the planet ( Jupiter ) but I can never zoom in enough to actually see it.

Now my question is, is this because I need to have a 20mm eyepiece to see the planets? I have heard I do because it will focus the light do to the fact my telescope is so small but I want your guys help! please answer!

I'm assuming your scope is the Celestron 70mm Travel scope?.

If so, this scope is designed to be a wide field scope which gives very pleasing views of constellations, star clusters and even the Moon. It really isnt designed for observing planets although this is possible if you buy a sturdier tripod to mount it on. 

If i remember correctly, this scope comes with a 10mm and a 20mm (or 25mm eyepiece). As such the 10mm is useless. Its not going to give wide field views. The 20/25mm works better.

For observing planets with the scope, you need to invest in a better tripod (i use a Horizon 8115) and then you should be able to use the 10mm eyepiece to observe Jupiter,Saturn,Mars etc.

To be brutally honest, its not a scope built for planetary observing. I use mine now purely for solar observing.

[AstroJacob]

Yea I know that I just purchased the telescope while I saved for my new one I am purchasing, I only payed a very small amount for it because I bought it off a friend who didn't use it.

[ronin]

What is it that you want a scope to do or have?

The problem is that you can and will get told every option possible, also everyone wants a scope to do everything - which is again somewhat none realistic.

If £500 is the maximum and full amount then keep $100 for accessories, meaning around $400 on scope and mount. If the idea is $500 on scope and mount and then you save and buy an extra eyepiece monthly then mention that approach.

If $500 is the MAX then make it clear, strange that scopes suggested start out at budget then rise and rise and rise in cost.

Are you happy with a manual dobsonian?

They provide the biggest aperture for the cost.

Do you want an equitorial for potential use in the imaging arena?

Imaging means motors either at the start or eventually.

An SCT is reasonable but I suggest one of those as a goto, the delivered field of view is narrow and manually finding and tracking is therefore troublesome.

[Lowjiber]

I always tell new folks two things about buying their first "real" telescope...

1.  When it comes to refractors, junk usually stops above 70mm.

2.  When it comes to Deep Space Objects (DSO), aperture rules... and Dobs rule aperture.

Presently, you sound like you need an Eq mount like a hog needs a songbook.  Many beginners usually throw in the old "I may want to do astrophotography in the future." argument.  I submit that at your current budget, you won't be doing any AP for quite a while anyway, as that aspect of our hobby is largely mount-dependent at a price far beyond your current budget.  There's plenty of time (and money) for that down-the-road.

Get a Dobsonian mounted 8" (or greater) scope.  It will be within a reasonable budget and serve your visual needs for years to come.

[RikM]

I always tell new folks two things about buying their first "real" telescope...

1.  When it comes to refractors, junk usually stops above 70mm.

2.  When it comes to Deep Space Objects (DSO), aperture rules... and Dobs rule aperture.

Presently, you sound like you need an Eq mount like a hog needs a songbook.  Many beginners usually throw in the old "I may want to do astrophotography in the future." argument.  I submit that at your current budget, you won't be doing any AP for quite a while anyway, as that aspect of our hobby is largely mount-dependent at a price far beyond your current budget.  There's plenty of time (and money) for that down-the-road.

Get a Dobsonian mounted 8" (or greater) scope.  It will be within a reasonable budget and serve your visual needs for years to come.

Sound advice.

[LukeSkywatcher]

Sorry, i missed the bit when you asked advice on a new scope for $500. I was merely pointing out the limitations of the 70mm travel scope regarding your observing of planets. You are in the States.........

There are quite a few other Americans here on SGL. If i remember correctly, when buying scopes in the states, you are kind of left with 2 choices........Celestron or Meade. Most other brands seem to need to be imported from Europe. Also i think you have to contend with state line laws and taxes etc?. It makes buying a scope in USA sound like a small hill to climb. 

If i am wrong about this then you have a nice budget for an 8" Dob or bigger (remember to save some cash for accessories). 

A Celestron SCT is a nice scope but $500 will only get you a 4" model (if buying new).

$1=€1 euro pretty much right now so i'm working on this.

Best bang for buck would be a Dob.........if you can manage one. They aint exactly small or light but have a huge amount of people who use them and love them and have no issues with carrying/transporting them.

[Lowjiber]

Sorry, i missed the bit when you asked advice on a new scope for $500. I was merely pointing out the limitations of the 70mm travel scope regarding your observing of planets. You are in the States.........

There are quite a few other Americans here on SGL. If i remember correctly, when buying scopes in the states, you are kind of left with 2 choices........Celestron or Meade. Most other brands seem to need to be imported from Europe. Also i think you have to contend with state line laws and taxes etc?. It makes buying a scope in USA sound like a small hill to climb. 

If i am wrong about this then you have a nice budget for an 8" Dob or bigger (remember to save some cash for accessories). 

A Celestron SCT is a nice scope but $500 will only get you a 4" model (if buying new).

$1=€1 euro pretty much right now so i'm working on this.

Best bang for buck would be a Dob.........if you can manage one. They aint exactly small or light but have a huge amount of people who use them and love them and have no issues with carrying/transporting them.

Since the OP is buying in the US, there are several good outlets available. Without a doubt, the GSO Dobs sold by OpticsSmart (Apterua Branded) are the most popular.  They come modified with roller bearings in the Az, leveling feet, flocking, etc.

Here's a link: http://www.opticsmart.com/

You won't find a better person to deal with than David Giles, the owner of Opticsmart.  Their scopes are often out of stock, but many are willing to wait, as they're hyper-tuned before leaving the store.  Give him a call.

[jetstream]

Dob...one of these from BH Photo would be nice, great vendor this place and only $355.00.

http://www.bhphotovideo.com/c/product/1141702-REG/sky_watcher_s11610_8_traditional_dobsonian.html

[Lowjiber]

Dob...one of these from BH Photo would be nice, great vendor this place and only $355.00.

http://www.bhphotovideo.com/c/product/1141702-REG/sky_watcher_s11610_8_traditional_dobsonian.html

Being from Vegas, I'll double-down on Gerry's comment about B&H Photo.  They usually have good prices, and their service is excellent.