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Help with Nexstar eyepieces

Celestron eyepieces beginner
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#1 jvb1


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Posted 10 July 2020 - 06:17 AM

I’m new to all this and would appreciate some help with eyepieces.  I have a Nexstar 6SE that will be used for occasional backyard moon and planet gazing.  Work and family commitments mean my partner and I get very little time to use the telescope (just twice in one year so far since we got it!) so I can't justify spending on a huge collection of EPs.  All I want is a high magnification EP for moon/planets and a lower power EP for more distant stuff to improve on the cheap 25mm plossl that came with the telescope. I’m considering a 7mm EP for moon/planet watching, but having read various forums some people say a 7mm EP would be great with a 6SE, others that a 7mm EP would be terrible with the 6SE.  So could someone please give me a straight answer: will I get decent views (for a complete amateur) of the Moon, Saturn and Jupiter from our backyard with a 7mm EP or won’t I, and if I won’t, could you back that up with reasons why I won't?  Finally, if the consensus is that a 7mm EP wouldn’t be suitable, would a 9mm EP be okay with the 6SE?


Many thanks and stay safe everyone.

#2 sg6



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Posted 10 July 2020 - 06:55 AM

6SE so 1500mm focal length, f/10.

My thoughts 30mm plossl, 18-20mm, 12mm, 10mm, 8mm.

30 for wide and alignment should deliver around 1 degree view.

18-20 for a bit middle field around 0.5 degree.

The 8, 10, 12 for the higher end - 3 because if the 8mm is too much the 10mm might be OK and if not the 12mm should.


8mm will give 190x(ish).


Later the draw of a 7mm or 6mm will arise and may work, but would I expect only work once a month even just once every 3 months - especially the 6mm. And have to ask is it worth it.


Which ones is down to budget and practicallity.


The other way is Saturn needs 120-150x, Mars is likely just out of 6SE ability for surface detail in most nights. So in some ways the 8mm is more then enough. Assumes it works.

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#3 Migwan



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Posted 10 July 2020 - 07:55 AM

How much power you can use on a given night depends on seeing and how bright the object is.  

An f10 SCT can handle a 12.5 more often than a 9 and a 9 more than a 6.5.   Even though good seeing can be somewhat rare up here due to the jet stream, I would not want to miss out on those higher power views when they are available.  On average, your seeing is probably better than mine.  


I think the most common high power EP progression for SCTs is 12.5-13, 9 and 6.5.   A 12.5-13 and an 8 might be a nice budgetary compromise to consider.   On that note, maybe something like an AstroTech 8mm Paradigm.   



Edited by Migwan, 10 July 2020 - 07:56 AM.

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#4 spongebob@55



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Posted 10 July 2020 - 10:17 AM

Two things that will effect your high power seeing.....  1.  Collimation and 2. Seeing. 


Have you checked your collimation?   It must be very very good for high power and will make a huge difference on high power objects.

Seeing must also be good.


I have a 6SE and I have a 7, 8 and 10mm high power eyepieces.   I have mostly average seeing.   My scope is very well collimated and is always temperature acclimated.   I can use the 10mm just about all the time on the moon.  The 8mm a lot and the 7mm only when seeing is good.   For me, the planets will make it more difficult to use anything more powerful than the 10mm.


One thing you could do after you check your collimation, is to get an inexpensive ~$45 used Celestron or equal 8-24mm zoom and use it for a while and see how it works under your conditions and scope.  That way, you'll know for yourself how the higher powers work on different objects.  It can also be resold so you'll get your money back.


Good luck.


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#5 PolyWogg


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Posted 10 July 2020 - 11:09 AM

I echo SpongeBob's comments (and who ever thought I would write such a statement?).


In my view, the debate over a 7mm is not a "real debate" for technical use. Officially, a 6SE has its highest useful magnification of 354x, which is between 4.5 and 4mm. So, yes, technically, you can use anything up to that point.


However, as SB said, unless you have fabulous seeing, anything under 8mm is questionable for your ability to use it on any given night. It's just too much power for the size of our scopes and the normal seeing conditions.


My son and I have SEs, his a 4 and mine an 8, and we can both handle up to about 200x magnificaiton without too much distorition. With my 8SE, if I got to 250x (with 8mm), it has to be a REALLY calm night with cool air. In the early fall, it's possible. In July? Not likely. If I use his 6mm, that takes me to the max limit of a 6SE (350x) and I can't use that almost ever, everything looks like the planet's inside an aquarium.


If you want to choose between an 10, 8 or 6 for the 6SE, take a peek at www.astronomy.tools and see what the theoretical difference is for your scope (choose FOV calculator, Jupiter, 6SE, and a 10mm EP or 8mm EP or 6mm EP). You'll be able to see what the difference will be in the scope IF YOU HAD PERFECT CONDITIONS. You may decide 10 is awesome and 7 is your ambitious one. Or 9 and 7 instead of 10/8/6. I don't worry about collimation that much, SCTs are pretty stable, but seeing and lighting affect a lot for me.


I wouldn't say you CAN'T use a 7, so much as you might not WANT to use a 7 for a given night.


If you want to talk WHICH style of EP to get, that's a whole other kettle of fish.



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#6 jvb1


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Posted 10 July 2020 - 09:15 PM

Thank you everyone.  Seems the consensus is that a 7mm won't get much use, so that's off the list and I should think about an EP with slightly lower power.

Polywogg - good point about the style of EP, but I'm thinking about a Celestron EP (might as well keep everything simple and in the family).

Spongebob - I've taken your suggestion about a zoom EP onboard. I've heard they can be tricky for novices (me) so that might be a purchase in the future, but for now I'll stick to a static EP I think.

With that said, I guess my options are either an X-Cel 9mm or a Luminos 10mm. They get favorable mentions in forums and seem reasonably priced.

Do any of you have experience with either of these and would I be better off with one compared to the other with my 6SE? I'm leaning towards the X-Cel as it has better eye relief (and it's about $30 cheaper) but if anyone has some solid advice I'm listening...

Thanks again.


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