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Main
Date: 07 Jul 2007 20:21:36
From: goodnigh
Subject: Eyepiece issue
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Just got a 10" Dob with 2" Crayford focuser.
My current eyepieces are 5mm, 7.5, 10, 25 and 40mm
in 1.25" size. Is there any reason to buy 2" eyepieces.
If so, what size would you buy first?
The scope has a 1200mm focal length at f4.7.
mike
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Date: 08 Jul 2007 19:26:57
From: Mark D
Subject: Re: Eyepiece issue
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Hello Mike, Others have brought up good points, it would be best to
first sample some eyepieces in 2" through other similar size, and focal
length scopes at a local star party.
Usually, in every club there's an eyepiece geek, with all the expensive
gizmos-eyepieces.
(I tend to fit that description myself.
It is perhaps an unknown at this point, if your own eyes have
astigmatism? For some, such as myself, some low power 2" eyepieces
through an extremely fast focal length scope such as yours might produce
a comatic field of little fan shaped stars.
Perhaps a better suggestion, and advice, would be to fill gaps in your
1-1/4" collection first?
One good benefit with 2" eyepieces with a fast undriven Dob, will be
wider true fields of view, thus giving you more enjoyable viewing time
before needing to nudge the scope to track.
As others here know, even a small collection of two, or three boutique
2" Eyepieces such as Televue Panoptics, or Naglers will easily exceed
the price of the scope itself. The decision of $$$$ expenditure will
have to be your call. Mark
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Date: 08 Jul 2007 18:01:33
From:
Subject: Re: Eyepiece issue
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Hi Mike, you need to buy a 31mm Nagler type 5 together with Paracorr
coma correction lens. You will never regret these $1000 spend
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Date: 09 Jul 2007 01:28:28
From: goodnigh
Subject: Re: Eyepiece issue
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<johannes@trostweb.net > wrote in message
news:1183942893.109577.66230@x35g2000prf.googlegroups.com...
> Hi Mike, you need to buy a 31mm Nagler type 5 together with Paracorr
> coma correction lens. You will never regret these $1000 spend
>
$1000 wow.
I am sharing resources with the Mustang project and
the laser projector project. That will have to wait.
Thanks for your input.
mike
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Date: 12 Jul 2007 08:06:02
From: Bob G.
Subject: Re: Eyepiece issue
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On Mon, 09 Jul 2007 01:28:28 GMT, "goodnigh"
<goodnigh1@mindspring.com > wrote:
>
><johannes@trostweb.net> wrote in message
>news:1183942893.109577.66230@x35g2000prf.googlegroups.com...
>> Hi Mike, you need to buy a 31mm Nagler type 5 together with Paracorr
>> coma correction lens. You will never regret these $1000 spend
>>
>
>$1000 wow.
>I am sharing resources with the Mustang project and
>the laser projector project. That will have to wait.
>Thanks for your input.
>
>mike
>
=============
A RUST tang...Project? oh my...
While I am not a Dob Guy nor a Rust tang type I do have to
congratulate you on having two great hobbies... Astronomy however is
by far the less expensive of the two...$1000 sounds like a lot for a a
Paracor and a Nagler and it is...(BTW I prefer Pentax XW's and SCT's)
but really not much in comparison with the cost of OEM car parts or
the cost of having a bumper re chromed .. Good EP's "work" in all
scopes buy one and keep it for life...
Bob G
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Date: 08 Jul 2007 11:23:39
From: canopus56
Subject: Re: Eyepiece issue
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On Jul 7, 11:26 pm, laura halliday <marsga...@hotmail.com > wrote:
> The no-cost way to find out what's right for you is to
> attend a star party, as others have mentioned. You
> can look through their eyepieces (preferably on your
> scope) and decide for yourself.
Laura, do you feel that there is any coma or aberration issues using 2
inch eyepieces on a fast f/4.7 lightbucket? Is the sweet spot large
enough? I haven't notice much with my 50mm 2 inch e.p. - Canopus56
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Date: 07 Jul 2007 22:26:47
From: laura halliday
Subject: Re: Eyepiece issue
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On Jul 7, 1:21 pm, "goodnigh" <goodni...@mindspring.com > wrote:
> Just got a 10" Dob with 2" Crayford focuser.
> My current eyepieces are 5mm, 7.5, 10, 25 and 40mm
> in 1.25" size. Is there any reason to buy 2" eyepieces.
> If so, what size would you buy first?
> The scope has a 1200mm focal length at f4.7.
Obviously there is *some* reason to buy 2" eyepieces,
or telescopes would not have 2" focusers, and manu-
facturers would not make 2" eyepieces to go in them. :-)
Two inch eyepieces are for wide field views, the ones
that make you feel like you're looking out the window of
an interstellar space ship. 2" Erfle eyepieces are a good
compromise for good views at a reasonable cost, but,
especially for fast scopes (f4.7 is fast), the very best
views come from fancy (expensive) eyepieces.
My first 2" eyepieces were Antares 52mm and 36mm
Erfles. I have since added a 40mm Pentax XW, and a
22mm Nagler Type 4. The latter two are brutes with grit-
your-teeth-and-try-not-to-scream-too-loudly price tags,
but the views are spectacular. Both are heavy enough
that they might actually upset the balance of your Dob.
The no-cost way to find out what's right for you is to
attend a star party, as others have mentioned. You
can look through their eyepieces (preferably on your
scope) and decide for yourself.
Laura Halliday VE7LDH "That's a totally illegal,
Grid: CN89mg madcap scheme. I like it!"
ICBM: 49 16.05 N 122 56.92 W - H. Pearce
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Date: 08 Jul 2007 13:59:42
From: goodnigh
Subject: Re: Eyepiece issue
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"laura halliday" <marsgal42@hotmail.com > wrote in message
news:1183872407.112370.208240@d30g2000prg.googlegroups.com...
> On Jul 7, 1:21 pm, "goodnigh" <goodni...@mindspring.com> wrote:
>> Just got a 10" Dob with 2" Crayford focuser.
>> My current eyepieces are 5mm, 7.5, 10, 25 and 40mm
>> in 1.25" size. Is there any reason to buy 2" eyepieces.
>> If so, what size would you buy first?
>> The scope has a 1200mm focal length at f4.7.
>
> Obviously there is *some* reason to buy 2" eyepieces,
> or telescopes would not have 2" focusers, and manu-
> facturers would not make 2" eyepieces to go in them. :-)
Unless to fool the unsuspecting amateur into buying more
expensive equipment they don't know how to use :-)
> Two inch eyepieces are for wide field views, the ones
> that make you feel like you're looking out the window of
> an interstellar space ship. 2" Erfle eyepieces are a good
> compromise for good views at a reasonable cost, but,
> especially for fast scopes (f4.7 is fast), the very best
> views come from fancy (expensive) eyepieces.
>
> My first 2" eyepieces were Antares 52mm and 36mm
> Erfles. I have since added a 40mm Pentax XW, and a
> 22mm Nagler Type 4. The latter two are brutes with grit-
> your-teeth-and-try-not-to-scream-too-loudly price tags,
> but the views are spectacular. Both are heavy enough
> that they might actually upset the balance of your Dob.
The Dob has a tensioning system so weight is not a problem.
I buy most of the products from Orion since I get a discount
and their retail outlet is a ten minute drive.
They sell some 2" eyepieces that cost more than scope, Wow!
The Dob was a good deal since it came with two 9x50 finder scopes
and mounting brackets plus two focusing assemblies, rack and pinion
and Crayford. Go figure.
On a different note, the primary mirror cell is pre-drilled and tapped
for a fan. Would you recommend one.
I appreciate your advice.
mike
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Date: 09 Jul 2007 00:44:45
From: Richard Amirault
Subject: Re: Eyepiece issue
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"goodnigh"
(snip)
> The Dob has a tensioning system so weight is not a problem.
(snip)
A tensioning system is not a replacement for a properly balanced scope.
Many folks attach weights on the "bottom" half of the tube when using heavy
2" eyepieces. If you go this route try not to attach the weights to the same
side of the scope as the focuser. If you do .. you may find that the scope
is balanced when pointed to the horizon, but when pointed at the zenith it
is not.
To properly balance a dob you'll need to attach the couterweights on the
bottom on the opposit side of the focuser. An adjustable rail .. or magnetic
weights .. can help to "fine tune" the balance for different eyepieces.
--
Richard Amirault
Boston, MA, USA
http://n1jdu.org
http://n1jdu.org/Fandom/science.htm
http://www.youtube.com/watch?v=J7hf9u2ZdlQ
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Date: 09 Jul 2007 01:14:11
From: goodnigh
Subject: Re: Eyepiece issue
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"Richard Amirault" <ramirault@verizon.net > wrote in message
news:1yfki.6254$t05.299@trndny09...
> "goodnigh"
> (snip)
>> The Dob has a tensioning system so weight is not a problem.
> (snip)
>
> A tensioning system is not a replacement for a properly balanced scope.
Actually, the tensioning system works quite well in keeping
the scope motionless yet easy to move.
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Date: 07 Jul 2007 16:38:02
From: Ben
Subject: Re: Eyepiece issue
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> But again, these decisions best made on the gut-level by looking
> through the e.p.s of your colleagues at star parties.
>
> - Canopus56
I have enjoyed using 2" EP's on occasion. It's a bit like observing
through a small television screen.
The only caveat I can offer pertains to the fact that as you get older
your pupil may not expand enough to accomodate the larger exit
aperture of a 2" and the star points become distorted.
My 32mm (1.25") was just fine when I bought it but as I am approaching
mid-sixties the star images are becoming progressively more
peculiar.
Ben
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Date: 12 Jul 2007 07:56:57
From: Bob G.
Subject: Re: Eyepiece issue
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On Sat, 07 Jul 2007 16:38:02 -0700, Ben <bet71743@netzero.com > wrote:
>
>> But again, these decisions best made on the gut-level by looking
>> through the e.p.s of your colleagues at star parties.
>>
>> - Canopus56
>
>I have enjoyed using 2" EP's on occasion. It's a bit like observing
>through a small television screen.
>
>The only caveat I can offer pertains to the fact that as you get older
>your pupil may not expand enough to accomodate the larger exit
>aperture of a 2" and the star points become distorted.
>
>My 32mm (1.25") was just fine when I bought it but as I am approaching
>mid-sixties the star images are becoming progressively more
>peculiar.
>
>Ben
==============================
Ben makes a good point... BUT in the case of the OP I would honestly
replace his current 25 and 40 mm 1.25 eyepieces with 2" eyepieces .
I also am in my mid 60's and I use a SCT but all my eyepieces avove 25
mm are 2" ones,,, just a much nicer view ... That said my
inexpensive 26 mm (Antates Eclipse) is absolutely horrible in a
frineds 10" Dob...(it sup[osily is a Q70 clone) my 31 mm Proxima is
fine and ..f/4.7 requires a much better EP than a slow f/10 SCT... we
will not
At some point I developed a taste for low power observing...and a 2"
EP just makes LOW POWER much more rewarding...FOR ME !
Bob G.
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Date: 07 Jul 2007 16:06:27
From: canopus56
Subject: Re: Eyepiece issue
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On Jul 7, 2:21 pm, "goodnigh" <goodni...@mindspring.com > wrote:
> Just got a 10" Dob with 2" Crayford focuser.
> My current eyepieces are 5mm, 7.5, 10, 25 and 40mm
> in 1.25" size. Is there any reason to buy 2" eyepieces.
I own a similar scope - a fast 10 inch Newt - but have only invested
in a couple of the high end eyepieces. In terms of visual observing,
there isn't much of anything you cannot accomplish with your 1 1/4"
set that you will be able to accomplish with a 2 inch set. But the
views, using high-end 2 inch or wide-angle 1 1/4 high-end eyepieces,
that I have seen in the scopes of others never cease to impress me.
It's largely an asthetic verses price point trade-off question - $200-
$300 of a really great view or $50 for a so-so smaller TFOV view, but
more money in your pocket to buy other goodies.
The easiest way to make that inherently gut-based decision is to go a
star party at your local club and look at targets through various high-
end e.p.s.
I own one 50 mm Antares 2 inch - which I use for the ultra-low
magnification "shuttle view port" view. On the other end of the
scale, I have a 4mm TMB e.p. (1 1/4 barrel) (about $100). The low-end
of the focal length scale is where I really feel you get the biggest
bang for a dollar invested. Expensive low focal length e.p.s give a
high-magnification view that is easily seen to be better than a cheap
4mm e.p. Between 15mm and 30mm, high-end 2" or wide angle 1 1/4"
e.p.s, IMHO, slighty improve the quality of the image relative to mid
and low-end e.p.s. What incremental benefit that they really provide
is a slightly better image over a much wider, visually more pleasing,
true field of view. So, between 15mm to 30mm, in a pinch, you can
accomplish the same observing - just in bits of TFOV.
So, I would say put your money first in areas that are inherently
covered better by high-end 2" or wide-angle 1 1/4" e.p.s. - the
ultra long focal length (the highest 1 1/4" e.p. fl is 40mm) - or the
low-focal length e.p.s. - e.g. 4mm, 5mm and 6mm. Others here will
have differing and equally valid opinions.
But again, these decisions best made on the gut-level by looking
through the e.p.s of your colleagues at star parties.
- Canopus56
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Date: 07 Jul 2007 23:36:50
From: goodnigh
Subject: Re: Eyepiece issue
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"canopus56" <canopus56@yahoo.com > wrote in message
news:1183849587.058219.92150@57g2000hsv.googlegroups.com...
> On Jul 7, 2:21 pm, "goodnigh" <goodni...@mindspring.com> wrote:
>> Just got a 10" Dob with 2" Crayford focuser.
>> My current eyepieces are 5mm, 7.5, 10, 25 and 40mm
>> in 1.25" size. Is there any reason to buy 2" eyepieces.
>
> I own a similar scope - a fast 10 inch Newt - but have only invested
> in a couple of the high end eyepieces. In terms of visual observing,
> there isn't much of anything you cannot accomplish with your 1 1/4"
> set that you will be able to accomplish with a 2 inch set. But the
> views, using high-end 2 inch or wide-angle 1 1/4 high-end eyepieces,
> that I have seen in the scopes of others never cease to impress me.
>
> It's largely an asthetic verses price point trade-off question - $200-
> $300 of a really great view or $50 for a so-so smaller TFOV view, but
> more money in your pocket to buy other goodies.
>
> The easiest way to make that inherently gut-based decision is to go a
> star party at your local club and look at targets through various high-
> end e.p.s.
>
> I own one 50 mm Antares 2 inch - which I use for the ultra-low
> magnification "shuttle view port" view. On the other end of the
> scale, I have a 4mm TMB e.p. (1 1/4 barrel) (about $100). The low-end
> of the focal length scale is where I really feel you get the biggest
> bang for a dollar invested. Expensive low focal length e.p.s give a
> high-magnification view that is easily seen to be better than a cheap
> 4mm e.p. Between 15mm and 30mm, high-end 2" or wide angle 1 1/4"
> e.p.s, IMHO, slighty improve the quality of the image relative to mid
> and low-end e.p.s. What incremental benefit that they really provide
> is a slightly better image over a much wider, visually more pleasing,
> true field of view. So, between 15mm to 30mm, in a pinch, you can
> accomplish the same observing - just in bits of TFOV.
>
> So, I would say put your money first in areas that are inherently
> covered better by high-end 2" or wide-angle 1 1/4" e.p.s. - the
> ultra long focal length (the highest 1 1/4" e.p. fl is 40mm) - or the
> low-focal length e.p.s. - e.g. 4mm, 5mm and 6mm. Others here will
> have differing and equally valid opinions.
>
> But again, these decisions best made on the gut-level by looking
> through the e.p.s of your colleagues at star parties.
>
> - Canopus56
Well put Canopus56!
Thanks for your insight.
mike
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Date: 07 Jul 2007 16:44:00
From: Dennis Woos
Subject: Re: Eyepiece issue
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"goodnigh" <goodnigh1@mindspring.com > wrote in message
news:kBSji.4988$tj6.1471@newsread4.news.pas.earthlink.net...
> Just got a 10" Dob with 2" Crayford focuser.
> My current eyepieces are 5mm, 7.5, 10, 25 and 40mm
> in 1.25" size. Is there any reason to buy 2" eyepieces.
> If so, what size would you buy first?
> The scope has a 1200mm focal length at f4.7.
>
> mike
>
Look at this eyepiece calculator:
http://televue.com/engine/page.asp?ID=107
and, if you spend some time studying the results, you will understand a lot
more about eyepiece selection.
Dennis
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Date: 07 Jul 2007 22:04:19
From: goodnigh
Subject: Re: Eyepiece issue
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"Dennis Woos" <dpwoos@gmavt.net > wrote in message
news:138vuoiqe3ebnd1@corp.supernews.com...
> "goodnigh" <goodnigh1@mindspring.com> wrote in message
> news:kBSji.4988$tj6.1471@newsread4.news.pas.earthlink.net...
>> Just got a 10" Dob with 2" Crayford focuser.
>> My current eyepieces are 5mm, 7.5, 10, 25 and 40mm
>> in 1.25" size. Is there any reason to buy 2" eyepieces.
>> If so, what size would you buy first?
>> The scope has a 1200mm focal length at f4.7.
>>
>> mike
>>
>
> Look at this eyepiece calculator:
>
> http://televue.com/engine/page.asp?ID=107
>
> and, if you spend some time studying the results, you will understand a
> lot more about eyepiece selection.
>
> Dennis
Ok, thanks for the URL. Very useful.
Now what would you buy for a first and only lens?
mike
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Date: 07 Jul 2007 21:46:31
From: Dennis Woos
Subject: Re: Eyepiece issue
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"goodnigh" <goodnigh1@mindspring.com > wrote in message
news:D5Uji.5022$tj6.1978@newsread4.news.pas.earthlink.net...
>
> "Dennis Woos" <dpwoos@gmavt.net> wrote in message
> news:138vuoiqe3ebnd1@corp.supernews.com...
>> "goodnigh" <goodnigh1@mindspring.com> wrote in message
>> news:kBSji.4988$tj6.1471@newsread4.news.pas.earthlink.net...
>>> Just got a 10" Dob with 2" Crayford focuser.
>>> My current eyepieces are 5mm, 7.5, 10, 25 and 40mm
>>> in 1.25" size. Is there any reason to buy 2" eyepieces.
>>> If so, what size would you buy first?
>>> The scope has a 1200mm focal length at f4.7.
>>>
>>> mike
>>>
>>
>> Look at this eyepiece calculator:
>>
>> http://televue.com/engine/page.asp?ID=107
>>
>> and, if you spend some time studying the results, you will understand a
>> lot more about eyepiece selection.
>>
>> Dennis
>
> Ok, thanks for the URL. Very useful.
> Now what would you buy for a first and only lens?
>
> mike
>
The bottom line is that inexpensive Plossls arguably work as well as the
most expensive eyepieces on axis, and within the limits of their fovs and
eye relief. What you get by paying more (assuming you spend your money
wisely) is mostly wide fov, better performance off-axis, and eye relief. You
must decide for yourself what attributes matter to you, and how much you are
willing and able to pay to push them. My advice to you is not to buy
anything, but rather attend star parties/observe with others, borrow
eyepieces, and learn how different eyepieces and eyepiece designs address
these issues.
Dennis
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Date: 08 Jul 2007 13:03:13
From: goodnigh
Subject: Re: Eyepiece issue
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>> Ok, thanks for the URL. Very useful.
>> Now what would you buy for a first and only lens?
>>
>> mike
>>
>
> The bottom line is that inexpensive Plossls arguably work as well as the
> most expensive eyepieces on axis, and within the limits of their fovs and
> eye relief. What you get by paying more (assuming you spend your money
> wisely) is mostly wide fov, better performance off-axis, and eye relief.
> You must decide for yourself what attributes matter to you, and how much
> you are willing and able to pay to push them. My advice to you is not to
> buy anything, but rather attend star parties/observe with others, borrow
> eyepieces, and learn how different eyepieces and eyepiece designs address
> these issues.
>
> Dennis
Ok, makes sense. Midrange eyepieces work as well as the more expensive
models on axis.
I will ignore your advice, not to buy, and buy a case in which to carry the
OTA.
Need one of those.
mike
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