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JB97

New to sky watching

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Hi I'm new to having a telescope I just got a AstroMaster 70AZ for my birthday a few days ago and was wondering what I can buy to improve my experience looking at planets such as Mars and Satrun, I noticed I can see the planets but if I try to zoom in the picture get weird and out of focus with my 10mm eyepiece and my 20mm, even with that issue I get a nice view of stars.

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Hi, welcome and Happy Birthday.

First off, you must realize that you cannot "zoom in". How "big" everything appears (magnification) is not determined by the large rotating knobs on either side of the scope - they are only for adjusting the focus. The magnification you get is determined by the combination of the focal length of the scope (basically the length of the tube, 900mm in your case, but be sure to look it up for yourself) and the focal length of the eyepiece you are using (either 20mm or 10mm). To know the magnification, you divide the focal length of the scope by the focal length of the eyepiece. So you get either 900:20 = 45x or 900:10 = 90x. You use the focuser to get the view as sharply focused as you can with the eyepiece you are using, and that's it.

So a shorter eyepiece will give more magnification. However: it's not entirely that simple. When you increase the magnification, stuff gets bigger, but also gets fuzzier. How fuzzy it gets depends on how much light your scope can gather. A scope that gathers more light will keep the fuzziness further down at higher magnification - in other words, a scope that gathers more light allows you to see more detail when using a shorter eyepiece. The amount of light your scope gathers is determined by the size (diameter) of the lens up front (this size is also called 'aperture') - in your case 70mm. The only way to gather more light than your scope does is to use a different scope, one with more aperture (a bigger front lens). So your scope will never be able to gather more light than it does. But don't worry about this, you just need to get used to it.

There is a simple "rule of thumb" to follow, which says that the maximum useful magnification of your scope is 2x the aperture. So in your case, according to this rule, you should not try to get more magnification that 2 x 70 = 140x. Go above that, and the view will most likely be too fuzzy to enjoy. So you could consider getting a shorter eyepiece in order to get more magnification (you do the math to determine how short you can go). But for now, don't rush in to this. Just get used to using your new scope, learn to get the best focus you can, enjoy looking at what you can see. This is a patient business!

Look around here on SGL and the interwebs to find out what you can actually expect to see. It doesn't get very large and detailed through a telescope; the amazing pictures you sometimes see are (obviously) made using cameras and they work differently than our eyes. So remember it's not about getting up real close - none of us can do that, really.

You might want to read this:

http://www.scopereviews.com/begin.html

Enjoy your new scope, and have fun!

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Hi JB, welcome. Excellent advice above and don't forget: what you see through your scope won't be like the pictures on some of their adverts.

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The 70AZ is a refractor if I recall, cannot remember the focal length or f nu,mberso bit of a guess there. Found it = 70mm, 900mm, f/13, looks a useful scope to get started with.

Possibly the biggest aspect is to start applying a bit of thought.

Planets: Jupiter needs about 60x to 70x to see the banding on it  As magnification if scope focal length divided by eyepiece focal length that means about 12mm eyepiece (900/12 = 75x). Saturn I have found needs more, further away and smaller, and 120x is about just enough, that is a 8mm eyepiece (900/8 = 112x). Mars will always be a small disk as it needs higher magnification then the scope will deliver. So basically just accept the limitations.

To improve things you are really looking at starting an eyepiece collection. I do not use a barlow, prefer to use individual eyepieces so I will talk along those lines. I would expect the scope to deliver a maximum of about 100x, a 9mm eyepiece, meaning Saturn at 112x is pushing your luck a bit.

Eyepieces really are dependant on budget. There are reasonable plossl's by GSO and Vixen around £30 each new some appear used however, next up are the BST Starguiders at £49 a piece. Will stop there are I doubt you are thinking of £150 eyepieces on the scope.

Other objects try the globular clusters, M13 in Hercules is the obvious, think M5 a nd 2 or 3 others are around. Also consider double stars, easy to work through a selection, Mizar and Alcor in the Plough is almost an eye test (ot was  once), Almaak and Albireo are 2 others. Search "coloured double stars delaware", nice little list of about 20.

Load up Stellarium, get your location in. Set the time (F5) and press F4 set the DSO magnitude to 6 (lots disappear) and you re left with the brighter things that are floating around up there. Get a cheap samll notebook from Wilkinsons to write thing in - say 3 or 4 of the Globular clusters.

Learn the constellations, if someone say try M1 in Lyra you first have to be able to identify Lyra, know the basic constellations is important.

Add your location, very very helpful to people. As said mainly apply some thought to it all, and ask. We like the simple questions, usually we can answer those ones.

 

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Hello and a warm welcome to the SGL. Lots of good advice already given. The main thing is to enjoy your new hobby.

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Hi and welcome, there are various free programs that will show you what you can expect to see through various scopes, one that I like is called 12Dstring, the link is  www.12dstring.me.uk. You can go to the drop down box for your scope ie Celestron and pick your model 70AZ, then pick from an assortment of eyepieces, the image you see is what can be achieved. However the images are colored which you will not see, also the clarity will vary depending on the seeing conditions, on 12Dstring the images shown are at the very best seeing conditions and the darkest skies, so don't expect to see exactly what is shown, as these are a guide only. Check it out, it is a bit of fun to play around with.

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18 hours ago, iPeace said:

There is a simple "rule of thumb" to follow, which says that the maximum useful magnification of your scope is 2x the aperture.

 You mention ' maximum useful' but at twice the aperture,  I find this almost impossible without several  issues?  Desirable would be a better word, or 'dream-on' as  another?
  
As rules go, I now work on the principle that the aperture itself, is  a safe guide to the ' maximum practical limit' of a Newtonian telescope, and I  can work from there, using the focal ratio as a guide to using  and selecting  my first  high powered eyepiece, in order to achieve this practical limit. Going beyond this 'practical  limit' the image only  degrades,  along with a reduction in the field of view.

Twice the aperture is  desirable, wishful,  but to me, just theoretical,  Its just so hard to achieve, especially here in the UK, and if  anywhere  near achievable, then  my viewing conditions will  have  been mint!
So under normal viewing conditions, the size of the Aperture is a good suggestion as to the  practical power of the telescope, and if using a Newtonian, by multiplying  the telescopes focal ratio by the entry pupil of your eye,  you can use this as a guide to your low powered eyepiece, as there is a limit to low magnification,  due to the Newtonian design,  refractors are not limited in the same way, as they don't have a secondary mirror? Any magnification from the lowest to twice the aperture now becomes 'useful'  to me and anything else...........bonus!

I note, looking at the 70AZ's  manual,  that  it recommends (another general rule, x50-x60?)  that x60 power, per inch of aperture,  gives this telescope a useful magnification of x168!!!!........really!

Scopes bigger than mine may fare  better,  and with less power, due to the increase in their apertures, affording  greater light gathering ability providing  brighter more detailed imagery, but with smaller apertures like mine and below, we just have to make do, and hope for better, but at what cost, size....the list goes on!

JB96.......enjoy what you have for now, there's little you can really do to improve its physical performance, except for one?........ try looking at the targets you study now, only from a much darker site! you will be amazed at the difference when you have no light pollution around, and as you learn more, and find your way around, you'll may wan't to consider an  early upgrade,  or wait till Christmas/Birthday?

There are limits, and for some folk, pitfalls with certain telescopes?  its not until some time later that we realize them?   I upgraded from my first scope in less than a week! but it was not gifted too me, so not an issue?  If I ever get a chance to test a 250mm or 300mm Skyliner side-by-side in my back yard, and the difference is outstanding, then I will lose the present scope in favour of the new one! If not, this one may last a lifetime!

Edited by Charic
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5 hours ago, Charic said:

 You mention ' maximum useful' but at twice the aperture,  I find this almost impossible without several  issues?  Desirable would be a better word, or 'dream-on' as  another?

As stated, it's a "rule of thumb", quite appropriate in the context of this sub-forum as directed towards a new astronomer with a new refractor of this type.

Not meant to be a declaration of universal truth to experienced astronomers.

:happy11:

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Hi everyone I have purchased Celestron Astromaster 130 Eq scope. What planets can i be able to see with it???

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@Charic are you sure that you are not just hitting atmospheric effects as the point where magnification ~ aperture? My 8" dob certainly has the legs to go past 200X if the atmosphere (including the bit insdie the tube!) allows it and I doubt that the optical performance is any difference to yours. With a smaller scope I would think that you will be able to hit the limits of the scope itself much more easily which is where the 2X aperture could come into play. 

@JB97 as stated above you need to change eyepieces in order to change magnification. Ronin's suggestion of BST Starguiders is an excellent one. They are very good eyepieces at a relatively cheap price.

@Anand P S You should be able to see Venus, Mars, Jupiter and Saturn quite easily, if/when they are visible If you download Stellarium and set it to your location you will be able to get a good idea of what is currently visible. You will not be able to see individual rocks on the Moon as they are far too small.

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5 hours ago, iPeace said:

As stated, it's a "rule of thumb", quite appropriate in the context of this sub-forum as directed towards a new astronomer with a new refractor of this type.

Not meant to be a declaration of universal truth to experienced astronomers.

:happy11:

I agree, it was just my take  on how I interpret the ' rules ' 

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4 hours ago, Ricochet said:

My 8" dob certainly has the legs to go past 200X if the atmosphere (including the bit insdie the tube!) allows it ..........

 

Mine does too! I push to x375  on the Moon using my 3.2mm,  but not much else gets such a high magnification, but my take is, if you take the scopes data plate (F-1200 A-200 f/6 ) then a 6mm Eyepiece provides x200 and 1mm exit pupil. Pushing far beyond this capability,  will ultimately  suffer image degradation, unless I/you,  use a bigger aperture. I'm  using the scopes data as a reference to its  practical design capability. My usable range is from x375 - x375. 5!  The most used range is between x150 ~ x100.

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Thanks everyone your a big help I'm still not use to things just yet but I'm enjoying seeing Saturn and the stars each night I see something new.

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