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stivesstargazer

10mm or 20mm eyepiece?

14 posts in this topic

Hi all,

i recently got a celestron astromaster 114 eq newtonian. It has come with 2 eyepieces a 10mm and a 20mm. This might sound a dumb question but apart from 10mm what are the differences between the two, which is best and when to use one over the other any help gratefully recieved..

many thanks Peter

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Your scope has a focal length of 1000mm so the 10mm eyepiece gives 1000/10=100x magnification and the 20mm gives 1000/20=50x. The 20mm also gives a larger field of view than the 10mm. For Deep Sky objects like clusters use the 20mm and for the moon and planets use the 10mm eyepiece (swap and change as you see fit). Hope this gets you started.

Edited by Bizibilder

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Sky objects like clusters use the 20mm and for the moon and planets use the 10mm eyepiece.

Agreed. The 10mm will give you nice close up views of the Moon and planets. For other objects that are further away but much bigger...............the 20mm will give good views. You dont want close up views of nebulae etc. To admire those you need to take a step back in magnification and see the wider image.

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Basically the 10mm gives twice the magnification of the 20mm.The 10mm is best used for looking at the moon and planets. The 20mm is best used for star clusters, nebula and galaxies because it gives a wider field of view. In the future you will probably want to upgrade your range and type of eyepieces. There is plenty of information on SGL about eyepieces.

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Thanks all, that has cleared that up..

With the scope that i have, what can i realisticaly hope/try to see as a total beginner when we have a clear night.One step at a time where should i start,i would love to see some new planets is that realistic as a newbie??

Thanks Peter

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Thanks all, that has cleared that up..

With the scope that i have, what can i realisticaly hope/try to see as a total beginner when we have a clear night.One step at a time where should i start,i would love to see some new planets is that realistic as a newbie??

Thanks Peter

Saturn and Jupiter will be on show. They really are show stoppers.

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The Moon is an obvious target and is coming nicely into view just after sunset (clouds permitting!) Venus is low in the south west just after Sunset (can't miss it it's really bright!). Jupiter is due south and quite high up (and bright) in the evening sky. SAturn and Mars are early morning objects at the moment.

The Pleiades is a good target for your scope (M45 is its other name) as well as M42 in Orion and M32 in Andromeda.

If you download "Stellarium" you can see, in a pretty realistic way, what is visible in the sky at any time.

PS: DON'T even attempt to look at or near the Sun! - You can buy perfectly good and safe filters - but for the time being just DON'T!!!

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Certainly realistic. Firstly if you download Stellarium Stellarium it will show you a realtime virtual sky so you can find where to look for planets etc. You will definately be able to look at Jupiter and its moons and probably Mars.

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Thanks again for rapid answers, Venus and Jupiter oh that would be amazing, been checking every half hour but still really cloudy.

Thanks for the sun advice bizibilder ill steer clear,,is eye safety because of my inexperience the reason for for avoiding it?

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Thanks for the sun advice bizibilder ill steer clear,,is eye safety because of my inexperience the reason for for avoiding it?

Yes its safety. You will know what a magnifying glass focusing the suns rays onto paper or a leaf can do - it burns a hole and often sets them alight. Imagine that many times multiplied with a telescope and happening to your eye in a split second :D

Nothing to do with experience - just never look at the Sun with any optical aid (including binoculars).

It is possible to get special filters which make it safe - these are the ones that cover the whole front of your scope and NOT the ones that screw onto the eyepiece - avoid the latter like the plague.

Safety note ends :)

Edited by John

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i hope we get some clear nights soon. i just got a skyhawk 114 for christmas. got a couple of breaks in the cloud on christmas night so got a view of jupiter and its 4moons, didnt see any details as the 'seeing' wasnt that great but still nice to see for the 1st time, plus got nice views of m45 and m42. plaiedes is defo my fav so far.

so good luck with your scope and lets hope for clear skies.

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It also depends on conditions, sometimes the views with your 10mm will be washed out.

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