Telescope eyepieces and newbie equipment

[GFAJ1]

Hello everyone!
I have recently been interested in astronomy!I have been observing the moon with some binoculars and want an upgrade to see better and more!I want to spend from 150 to 350$!I am thinking the the celestron powerseeker 130Q or the astron master 90 eq in both cases I also wanna buy a barlow lens and an adjustable 4-20mm eyepiece to focus and look at the plantes in some detail!I am mostly intereseted in viewing planets and some occasional deep-sky objects when I make small trips to the countryside!Any thoughts on these models!?Any recommendations on telescopes?!1

[Lady Fraktor]

Hello GFA, both telescopes will get you started though the 90 may be a bit better for planetary/ lunar viewing.
The 90mm being f/11 does not really need a barlow to start with. High power views can be achieved with a 5mm or 6mm eyepiece.

The 130mm will give some good views but not as good on the planets at f/5

[Thefatkitty]

Hi GFA, welcome! I'm with Gabrielle, I think the 90mm would be the better of the two for what you want to observe. I don't know about the mount for it though; looks a little overwhelmed.... Still, it gets good reviews, and it seems you can even hook a DSLR up to it and get some Moon shots: https://www.amazon.com/Celestron-21064- ... B000MLHMBM

Either way, be interested to hear what you get!

All the best,

[Refractordude]

There are a lot of bad reviews for the Celestron Astromaster AZ and EQ mounts. I read that the Celestron reflector Powerseekers are hard to collimate, because of the design. I could be wrong about the Powerseekers. I like the Meade Infinity 102mm refractor as a beginner scope. With a budget of $300 you can get a #8 yellow filter for the planets, and a few upgraded eyepieces.

[Don Alvarez]

There are a lot of bad reviews for the Celestron Astromaster AZ and EQ mounts. I read that the Celestron reflector Powerseekers are hard to collimate, because of the design. I could be wrong about the Powerseekers. I like the Meade Infinity 102mm refractor as a beginner scope. With a budget of $300 you can get a #8 yellow filter for the planets, and a few upgraded eyepieces.

The Powerseeker 127 is the only one that uses the Jones-Bird Design. The other reflectors in their starter lines (PowerSeeker, Astromaster) should be traditional Newtonians, though the 114 is a long tube and will probably be extremely unstable on the EQ1 mount.

I also endorse the Meade Infinity series for beginners.

[GFAJ1]

Thank you all for your help!I think I will get the astromaster 90EQ with agood 4 mm eyepiece!That should allow me to get some decent views of the planets right?!I would go meade but they are very rare in my country

[Lady Fraktor]

Thank you all for your help!I think I will get the astromaster 90EQ with agood 4 mm eyepiece!That should allow me to get some decent views of the planets right?!I would go meade but they are very rare in my country

Actually no it will not help
Telescopes and your eyeballs have a maximum power that they can be used up to.
Then there is the issue with the atmosphere that we need to look through which limits how much power we can actually use at a given time.
The highest power views with the 90mm will be with a 5.5mm or 6mm eyepiece, BUT telescopes are not about high powers.
You will find that the telescope will work best at lower powers such as a 10mm or 11mm eyepiece with this one.
Understand though that a 11mm eyepiece in this telescope is still considered a high power eyepiece.
A 5.5mm or 6mm would be considered a extreme high power and if the sky conditions are not perfect (which they rarely are) all you will be doing is blurring out any detail on the object you are trying to view.

[GFAJ1]

So i do no need another eyepiece?What about a barlow lens?Thanks

[Lady Fraktor]

A barlow lens is not needed very much with these telescopes due to the long focal length.
The stock eyepieces will get you out viewing but the telescope will benifit from a upgrade of a decent Plossl or two.
A 10mm or 12.5mm and 25mm will be good and give you some better views.

There is a article in eyepiece forum at the top on how to pick eyepieces for your telescope.

[GFAJ1]

Ok I will be sure to read it thanks a lot

[GFAJ1]

OK so the Astromaster 90 EQ has a focal length of 11 or 1000mm with an aperure of 90 mm Minimum useful magnification is 90/5=18x
Maximum useful magnification is 90-180(in top notch conditions)
1000/18 = is f/55mm maximum eyepiece
100/100(to average it out) is f/10mm minimum eyepiece
is my math right?
Does that mean that anything beyond a 10mm eyepiece is useless?

[Lady Fraktor]

A good usable starting range for the 90mm would be between 32mm for maximum low power and a 11mm for very high powers.
A eyepiece that equals the telescope focal length 11 in this case, gives you best resolution and magnification.

IF THE SKIES COOPERATE and seeing and transparency are excellent then you can use higher powers that will let you go to a 0.5mm exit pupil which would be a 5.5mm eyepiece in this case.
Once you have spent time learning how to use the telescope and reading the local sky conditions you can start using higher powers.
Until then very high powered eyepieces will be seldom used, with experienced observers they are still seldom used unless looking at the lunar surface.

[Bigzmey]

OK so the Astromaster 90 EQ has a focal length of 11 or 1000mm with an aperure of 90 mm Minimum useful magnification is 90/5=18x
Maximum useful magnification is 90-180(in top notch conditions)
1000/18 = is f/55mm maximum eyepiece
100/100(to average it out) is f/10mm minimum eyepiece
is my math right?
Does that mean that anything beyond a 10mm eyepiece is useless?

If you are into planets and Moon on a good night you could push 90mm F11 scope closer to 200x, so 5-7mm EPs could be used on occasion. But as Gabby says you should start at lower power and work your way up.

[Sky Tinker]

This kit and this listing?

https://www.planitario.gr/thleskopio-as ... -90eq.html

I have a Meade "Polaris" 90 EQ , and it's great...

It has a far better focusser, of metal, than that of the Celestron "AstroMaster" 90EQ which is of plastic. It's also a bad design. I know because I have the "Astromaster 70EQ, and with that same wonky focusser...

kit4.jpg (47.63 KiB) Viewed 2646 times

I would try my best to avoid any of those Celestron kits. This Sky-Watcher 90/900 refractor kit would be a much better value, and for less...

https://www.planitario.gr/skywatcher-90-900-az3.html

In any event, for any of those kits, you will need a proper, star diagonal for use at night.

By the by, for only 10 € extra, you can get this... https://www.planitario.gr/dobsonian-6.html

This would be a great value as well... https://www.planitario.gr/dobsonian-truss-130mm.html

Hold off on buying any eyepieces and accessories until you decided upon a kit.

[Refractordude]

This kit and this listing?

https://www.planitario.gr/thleskopio-as ... -90eq.html

I have a Meade "Polaris" 90 EQ , and it's great...

kit2.jpg

It has a far better focusser, of metal, than that of the Celestron "AstroMaster" 90EQ which is of plastic. It's also a bad design. I know because I have the "Astromaster 70EQ, and with that same wonky focusser...

kit4.jpg

I would try my best to avoid any of those Celestron kits. This Sky-Watcher 90/900 refractor kit would be a much better value, and for less...

https://www.planitario.gr/skywatcher-90-900-az3.html

In any event, for any of those kits, you will need a proper, star diagonal for use at night.

By the by, for only 10 € extra, you can get this... https://www.planitario.gr/dobsonian-6.html

This would be a great value as well... https://www.planitario.gr/dobsonian-truss-130mm.html

Hold off on buying any eyepieces and accessories until you decided upon a kit.

Those Celetrons do have bad mounts, but can he get the Skywatcher 90mm refractor or 102mm Meade infinity refractor in Greece? If he can, then that is the way to go/purchase. The Meade will do better for deep space objects.

[Sky Tinker]

This kit and this listing?

https://www.planitario.gr/thleskopio-as ... -90eq.html

I have a Meade "Polaris" 90 EQ , and it's great...

kit2.jpg

It has a far better focusser, of metal, than that of the Celestron "AstroMaster" 90EQ which is of plastic. It's also a bad design. I know because I have the "Astromaster 70EQ, and with that same wonky focusser...

kit4.jpg

I would try my best to avoid any of those Celestron kits. This Sky-Watcher 90/900 refractor kit would be a much better value, and for less...

https://www.planitario.gr/skywatcher-90-900-az3.html

In any event, for any of those kits, you will need a proper, star diagonal for use at night.

By the by, for only 10 € extra, you can get this... https://www.planitario.gr/dobsonian-6.html

This would be a great value as well... https://www.planitario.gr/dobsonian-truss-130mm.html

Hold off on buying any eyepieces and accessories until you decided upon a kit.

Those Celetrons do have bad mounts, but can he get the Skywatcher 90mm refractor or 102mm Meade infinity refractor in Greece? If he can, then that is the way to go/purchase. The Meade will do better for deep space objects.

A 90/900, has, a 900mm focal-length. That's a reasonably low 28x with a 32mm Plossl. In addition, the vast majority of deep-sky objects are small. You may be thinking of the physical length of the tube. That is what it is, and with an apochromat perhaps out of the question.

The mounts of these entry-level kits are not inherently bad, although they can certainly benefit from a bit of DIY work. They are of metal, and that's a good thing right off the bat. Rather, it is the mating of a telescope that is a bit too large for the mount that is bad. In many cases, the manufacturers provide only mounts that get the telescope up off of the ground, and little else. Synta is particularly bad about doing that. For example, my Meade 114mm f/8 Newtonian/EQ kit comes with an EQ-2, whilst Celestron's equivalent is not an exact equivalent, the mount being an EQ-1 instead.

At present, we do not know what type of mount the OP prefers or requires. Perhaps they'll chime in on that aspect. Also, it is only natural that those first starting out want to see everything fairly well with a single kit...

https://www.astroshop.eu/telescopes/mea ... az/p,45380

The AZ-3 mount of that kit supports the telescope adequately, but the mount is problematic.

This mount may be slated to replace that of the "Infinity" series; the "StarPro"... https://www.astroshop.eu/telescopes/mea ... az/p,59588

It's newly-arrived on the scene; "the new kid on the block".

But we don't know what sort of fees would be incurred in shipping one of those kits to the OP.

[Bigzmey]

GFA, will you buy your telescope from a local store or on-line? If on-line can you provide the link? This way we can help you to select the best scope for your money.

[Baurice]

A good usable starting range for the 90mm would be between 32mm for maximum low power and a 11mm for very high powers.
A eyepiece that equals the telescope focal length 11 in this case, gives you best resolution and magnification.

IF THE SKIES COOPERATE and seeing and transparency are excellent then you can use higher powers that will let you go to a 0.5mm exit pupil which would be a 5.5mm eyepiece in this case.
Once you have spent time learning how to use the telescope and reading the local sky conditions you can start using higher powers.
Until then very high powered eyepieces will be seldom used, with experienced observers they are still seldom used unless looking at the lunar surface.

I generally agree and have sometimes pushed the magnification to over 300x (nearly 500x on odd occasions) but then I use a Maksutov and not a standard Newt or achromat. An APO would also work well beyond the normal limit. As you say, this only works under great conditions on very bright objects.

I once pushed a 60mm achromat to 600x magnification and it made Venus look like a comet!

[Lady Fraktor]

I have used ludicrous high powers on lunar features and double stars, even stacking barlows but the list of objects this works with are very, very small unless you are just pushing the magnification for fun.

[DeanD]

This is a fascinating area of discussion and theory. You can go to "ludicrously high powers" (I have looked at Jupiter at 816x with my 102mm scope!), but the maximum resolution for a 90mm scope as given by the Rayleigh criteria is around 1.5 arc seconds for green light (ie: 134/D with D in mm). see: https://www.telescope-optics.net/telesc ... lution.htm

This means that once you are operating at high enough power to resolve two point sources (ie: stars) that are 1.5 arc-seconds apart, then any higher power will make the point sources seem bigger, but not give any more detail. For a 90 mm scope this would be in the order of 180x (ie: 0.5mm exit pupil). Even on nights of wonderful seeing and with an excellent scope going higher than this would be a bit like magnifying an image past the point where you see the individual pixels. Plus of course once you have an exit pupil smaller than around 0.5mm it is more likely that you will see "floaters" in your eye than extra detail through the telescope! 816x with a 102mm scope (as I mentioned above) doesn't really achieve much: it is really just mucking around!

However, the Rayleigh criteria for maximum resolution is about point sources. A linear source is a different beast altogether. With the naked eye we can see (for example) electrical lines that may be only 10mm thick over a kilometre away. This is around 2 arc-seconds with (daytime) pupils that are around 2mm. The Rayleigh limit for a 2mm objective lens is around 70 arc-seconds!

To use another example, I have glimpsed the Enke division in Saturn's rings with a 100mm scope. This is a maximum 4800km wide at a distance of around 1.2 billion km: or about 0.08 arc-seconds wide! The maximum Rayleigh resolution for a 100mm scope is 1.3 arc seconds...
So, with experience and on a really good night if you are looking at extended and bright objects like the moon or planets with linear features you may find going higher will give more detail. However, the contrast will drop too so it needs to be a very bright object to benefit from extreme power.

Bottom line for GFAJ1 is that a 5mm eyepiece will get occasional use, but 10mm and 20 or 25mm will get much more!

- Dean