Eye Pieces.

For a beginner (like I am) with a new 114GT, I'd suggest the Celestron
eyepiece kit. For about $100 to $130 (I paid $104), you get five Plossl
eyepieces, a 2X Barlow, an aluminum clad and foam filled case, and seven
filters to play with.


Good idea.

jon

Jon Isaacs wrote:
Exactly why are these optimal? Since the Nextstar 114 GT has a 1.25 inch
focuser, 40-42 mm will have the same True Field of View as 32mm, for the
vast majority of situations, the 32 will provide better views than the
40-42mm eyepiece. Also a 32mm doubles with a barlow to a 16 which is a
nice.

I wonder if he might have read my most recent Astronomical Games, in which
one of the eyepiece sequences I propose (in conjunction with a Barlow) has
focal lengths related in the ratio 8 to 5, which is pretty close to what
he wrote. Of course, I also wrote that it's impractical to follow that
scheme exactly, for a variety of reasons.

On the other hand, he might not have read it at all.

Brian Tung
The Astronomy Corner at http://astro.isi.edu/
Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/
The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/
My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.txt

Jon Isaacs wrote:
Exactly why are these optimal? Since the Nextstar 114 GT has a 1.25 inch
focuser, 40-42 mm will have the same True Field of View as 32mm, for the
vast majority of situations, the 32 will provide better views than the
40-42mm eyepiece. Also a 32mm doubles with a barlow to a 16 which is a
nice.

I wonder if he might have read my most recent Astronomical Games, in which
one of the eyepiece sequences I propose (in conjunction with a Barlow) has
focal lengths related in the ratio 8 to 5, which is pretty close to what
he wrote. Of course, I also wrote that it's impractical to follow that
scheme exactly, for a variety of reasons.

On the other hand, he might not have read it at all.

Brian Tung
The Astronomy Corner at http://astro.isi.edu/
Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/
The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/
My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.txt

I wonder if he might have read my most recent Astronomical Games, in which
one of the eyepiece sequences I propose (in conjunction with a Barlow) has
focal lengths related in the ratio 8 to 5, which is pretty close to what
he wrote.

I started to read it, realized I was going to have to think a bit and so I
marked it unread and haven't gotten back to reading it.

My own take on eyepiece ratios is that it is like gearing in a car or truck.
The low gears/magnifications are pretty far apart but as one gets close to the
limit of engine/road/telescope/seeing, the gears/eyepiece focal lengths ought
to get closer together. This allows one to play around as one reaches the
limit and reach some sort of optimal choice.

I like something like 32 - 22 - 15 - 9 - 7.5 - 6 - 5 with a couple of barlows
in case I want to be stupid. This is for scopes F4-F7

jon

I wonder if he might have read my most recent Astronomical Games, in which
one of the eyepiece sequences I propose (in conjunction with a Barlow) has
focal lengths related in the ratio 8 to 5, which is pretty close to what
he wrote.

I started to read it, realized I was going to have to think a bit and so I
marked it unread and haven't gotten back to reading it.

My own take on eyepiece ratios is that it is like gearing in a car or truck.
The low gears/magnifications are pretty far apart but as one gets close to the
limit of engine/road/telescope/seeing, the gears/eyepiece focal lengths ought
to get closer together. This allows one to play around as one reaches the
limit and reach some sort of optimal choice.

I like something like 32 - 22 - 15 - 9 - 7.5 - 6 - 5 with a couple of barlows
in case I want to be stupid. This is for scopes F4-F7

jon

I (Brian Tung) wrote:
I wonder if he might have read my most recent Astronomical Games, in which
one of the eyepiece sequences I propose (in conjunction with a Barlow) has
focal lengths related in the ratio 8 to 5, which is pretty close to what
he wrote.

Jon Isaacs wrote:
I started to read it, realized I was going to have to think a bit...

Doggone that!

...and so I marked it unread and haven't gotten back to reading it.

Pshaw.

Brian Tung
The Astronomy Corner at http://astro.isi.edu/
Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/
The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/
My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.txt

I (Brian Tung) wrote:
I wonder if he might have read my most recent Astronomical Games, in which
one of the eyepiece sequences I propose (in conjunction with a Barlow) has
focal lengths related in the ratio 8 to 5, which is pretty close to what
he wrote.

Jon Isaacs wrote:
I started to read it, realized I was going to have to think a bit...

Doggone that!

...and so I marked it unread and haven't gotten back to reading it.

Pshaw.

Brian Tung
The Astronomy Corner at http://astro.isi.edu/
Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/
The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/
My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.txt

"John Morris" wrote in message ...
As a newcomer to the hobby I have recently purchased a celstron 114GT.
It arrived with 2 eye pieces 10mm and 25mm.
Iam thinking of buying a 4mm would this be alright for this 4.5" telescope?
Many Thanks,
John.

A 4mm will provide 250x in your scope. IMO, this is probably at the very
limit of the power the scope will support, provided the mirror is ok.
You would be better off getting a barlow which would give you (if it's
a 2x job) a 12.5mm and a 5mm eyepiece. 200x is still reasonable for
the scope. You might also consider a 32mm for your scope as this will
provide the largest FOV in the 1-1/4" focuser at reasonable cost.
You can buy 24mm eyepieces with fields almost as wide, and more power with
field is always a better idea, but the cost will be higher than a 32mm Plossl.
If you intend to use eyepieces shorter than say 7mm, make sure the collimation
of the scope is bang on. The results are worth it.
-Rich

"John Morris" wrote in message ...
As a newcomer to the hobby I have recently purchased a celstron 114GT.
It arrived with 2 eye pieces 10mm and 25mm.
Iam thinking of buying a 4mm would this be alright for this 4.5" telescope?
Many Thanks,
John.

A 4mm will provide 250x in your scope. IMO, this is probably at the very
limit of the power the scope will support, provided the mirror is ok.
You would be better off getting a barlow which would give you (if it's
a 2x job) a 12.5mm and a 5mm eyepiece. 200x is still reasonable for
the scope. You might also consider a 32mm for your scope as this will
provide the largest FOV in the 1-1/4" focuser at reasonable cost.
You can buy 24mm eyepieces with fields almost as wide, and more power with
field is always a better idea, but the cost will be higher than a 32mm Plossl.
If you intend to use eyepieces shorter than say 7mm, make sure the collimation
of the scope is bang on. The results are worth it.
-Rich

Anyone mention getting a good 6mm Ortho??
Clear, Dark, Steady Skies!
(And considerate neighbors!!!)