Barlow lenses

I'd appreciate a bit of advise on Barlows. I've got a WO Megrez 90 APO,
which can accept either a 2" or 1.25" Barlow; what would be best ? I only
have one eyepiece - a WO zoom. I am hoping that the Barlow will allow me to
see Jupiter and Saturn a little better (i.e. increase the image size). Any
recommendations (image quality is more important than price) ?

Thanks,

Pete K

"BillyPIg" wrote in message
news
I'd appreciate a bit of advise on Barlows. I've got a WO Megrez 90 APO,
which can accept either a 2" or 1.25" Barlow; what would be best ? I only
have one eyepiece - a WO zoom. I am hoping that the Barlow will allow me
to see Jupiter and Saturn a little better (i.e. increase the image size).
Any recommendations (image quality is more important than price) ?

I get better results with Powermates than ordinary Barlows, but there
is a significant cost difference. For a cheap-but-good 2X Barlow,
you could try a TAL 2X. Note that 2" units are a *lot* more expensive
and are normally used with 2" eyepieces or for imaging with large
sensors, to reduce vignetting. I recommend you join a local astronomy
club, if you haven't already - then you may be able to try a few out
to see what works best with your scope, before spending any cash. )

HTH,
--
Rob (~52N, ~1W)

Rob,

Thanks for the suggestion. I'll take a look.

Pete K
"Rob" wrote in message
...

I get better results with Powermates than ordinary Barlows, but there
is a significant cost difference. For a cheap-but-good 2X Barlow,
you could try a TAL 2X. Note that 2" units are a *lot* more expensive
and are normally used with 2" eyepieces or for imaging with large
sensors, to reduce vignetting. I recommend you join a local astronomy
club, if you haven't already - then you may be able to try a few out
to see what works best with your scope, before spending any cash. )

HTH,
--
Rob (~52N, ~1W)

Joey

Your short focus refractor requires very short focus eyepieces to
provide adequate powers for most uses. I tend to use a 15mm or 10mm
eyepiece with my Vixen 90 on Saturn and Jupiter. At f/11 and 1000mm
focal length it provides slightly higher powers for the same eyepiece
than yours. You are restricted to about 80x with your present zoom. I
average around 100x on the planets and the Moon with my 90mm.

I'd look for a second hand Barlow at http://www.astrobuysell.com/uk/
to give you some experience of higher powers at relatively low cost.
A 2x Barlow will give you much greater flexibility in magnification
even if you find you rarely use the top power available.

The seeing conditions usually set the upper limit on the power you can
get away with. Though you are still limited with your present top
power of somewhere around 80x. If you can find something like a Meade
4000 2x Barlow in 1.25" size you'll then be able to decide at your
leisure whether you need to "upgrade" later on.

Seeing fine planetary detail is a skill developed by practice. You
should still be able to see quite a lot with your present highest
power. Even at powers as low as 30x you should be able to see the
belts of Jupiter and the shadow of Saturn on the rings. Seeing the
Cassini Division all the way round is a bit of a struggle at that low
power though.

Chris,

Thanks for the information and advice. I think I will probably opt for a
reasonable performance lens initially and then decide whether I think it
merits the additional outlay for a top of the range model at some later
date. I discovered that the BBC Sky at Night maggie has just reviewed some
Barlows, so I'll probably go for one of those.

I can make out the bands on Jupiter, but not the Cassini division, but I
think the problem is with my eyes, rather than the optics.

Cheers,

Pete K


"Chris.Bee" wrote in message
...
Joey

Your short focus refractor requires very short focus eyepieces to
provide adequate powers for most uses. I tend to use a 15mm or 10mm
eyepiece with my Vixen 90 on Saturn and Jupiter. At f/11 and 1000mm
focal length it provides slightly higher powers for the same eyepiece
than yours. You are restricted to about 80x with your present zoom. I
average around 100x on the planets and the Moon with my 90mm.

I'd look for a second hand Barlow at http://www.astrobuysell.com/uk/
to give you some experience of higher powers at relatively low cost.
A 2x Barlow will give you much greater flexibility in magnification
even if you find you rarely use the top power available.

The seeing conditions usually set the upper limit on the power you can
get away with. Though you are still limited with your present top
power of somewhere around 80x. If you can find something like a Meade
4000 2x Barlow in 1.25" size you'll then be able to decide at your
leisure whether you need to "upgrade" later on.

Seeing fine planetary detail is a skill developed by practice. You
should still be able to see quite a lot with your present highest
power. Even at powers as low as 30x you should be able to see the
belts of Jupiter and the shadow of Saturn on the rings. Seeing the
Cassini Division all the way round is a bit of a struggle at that low
power though.

On Apr 29, 8:26*pm, "BillyPIg" wrote:
Chris,

Thanks for the information and advice. *I think I will probably opt for a
reasonable performance lens initially and then decide whether I think it
merits the additional outlay for a top of the range model at some later
date. *I discovered that the BBC Sky at Night maggie has just reviewed some
Barlows, so I'll probably go for one of those.

I can make out the bands on Jupiter, but not the Cassini division, but I
think the problem is with my eyes, rather than the optics.

Cheers,

Pete K

The Cassini Division is easiest to see (of course) when the rings are
at a much higher angle. Look to the right and left at the ansae (ears
or handles) where the blackness of space is beyond the rings. Once you
can see the division there you may be able to follow the division
round to the front where it is far more difficult. The seeing
conditions are important. There are occasions when the division is
hard to spot with Saturn looking all fuzzy. Avoid looking over roofs
which have been heated all day by the sun. Or heated all day and night
by the central heating in winter. As the Saturn images in the link
below show the rings are at a very difficult angle at the moment to be
able to see the division. Patience will be rewarded as the rings open
out. The higher you can catch a planet in the sky the better too.
Usually anything below 30 degree altitude is a fuzzy blob from my
viewpoint. The best view I ever had was at -6C with snow underfoot a
blindingly bright moon and Saturn high overhead.

http://ceastronomy.org/tramakers

Chris,

Thanks for the view tips. I'll give it a go.

Pete K