Is image problem due to mirror?

Doc wrote:
I've been experimenting with a Meade 5" reflector, and find that the
Moon looks incredible, but when looking at Mars, with anything of
greater mag power than the 25mm eyepiece such as a 9mm or 4mm, the
image even at sharpest focus I can manage has traces of an
irregularity most noticeable around the edges, sort of like an
impressionist painting.

Is this likely caused by imperfections in the mirror being magnified
or something else?

It could be:

o Seeing/atmosphe Much more of an effect at high mag. How high was Mars?

o Eyepieces: If they (9 mm, 4 mm) came with a 5" reflector, they are
likely of low quality.

I'm using a new 8" SCT (cleaned and collimated at the factory two weeks
ago) on Mars and with my skies I'm having trouble getting sharp views
most nights using excellent EPs. OTOH .. one early morning in early
July, I was able to take my 5" SCT to 300x and get some really good views.

So it could easily be that conditions do not support the magnification
you are using.

Phil

"Phil Wheeler" wrote in message
...
Doc wrote:
I've been experimenting with a Meade 5" reflector, and find that the
Moon looks incredible, but when looking at Mars, with anything of
greater mag power than the 25mm eyepiece such as a 9mm or 4mm, the
image even at sharpest focus I can manage has traces of an
irregularity most noticeable around the edges, sort of like an
impressionist painting.

Is this likely caused by imperfections in the mirror being magnified
or something else?

Try it out on other planets, Mars is a bit awkward due to it's low position
in the sky. However, I got some nice views with my Tal 100R last night,
even with the light pollution I have to put up with.

Keep to something like the 9mm you are using.

Martin

"Phil Wheeler" wrote in message
...
Doc wrote:
I've been experimenting with a Meade 5" reflector, and find that the
Moon looks incredible, but when looking at Mars, with anything of
greater mag power than the 25mm eyepiece such as a 9mm or 4mm, the
image even at sharpest focus I can manage has traces of an
irregularity most noticeable around the edges, sort of like an
impressionist painting.

Is this likely caused by imperfections in the mirror being magnified
or something else?

Try it out on other planets, Mars is a bit awkward due to it's low position
in the sky. However, I got some nice views with my Tal 100R last night,
even with the light pollution I have to put up with.

Keep to something like the 9mm you are using.

Martin

Try using a barlow instead of a higher power eyepiece. Thais increases
relative focal length and helps with what you're describing. Used this
arrangement on my coulter 10" worked great.

Phil Wheeler wrote:
Doc wrote:

I've been experimenting with a Meade 5" reflector, and find that the
Moon looks incredible, but when looking at Mars, with anything of
greater mag power than the 25mm eyepiece such as a 9mm or 4mm, the
image even at sharpest focus I can manage has traces of an
irregularity most noticeable around the edges, sort of like an
impressionist painting.

Is this likely caused by imperfections in the mirror being magnified
or something else?


It could be:

o Seeing/atmosphe Much more of an effect at high mag. How high was
Mars?

o Eyepieces: If they (9 mm, 4 mm) came with a 5" reflector, they are
likely of low quality.

I'm using a new 8" SCT (cleaned and collimated at the factory two weeks
ago) on Mars and with my skies I'm having trouble getting sharp views
most nights using excellent EPs. OTOH .. one early morning in early
July, I was able to take my 5" SCT to 300x and get some really good views.

So it could easily be that conditions do not support the magnification
you are using.

Phil

Try using a barlow instead of a higher power eyepiece. Thais increases
relative focal length and helps with what you're describing. Used this
arrangement on my coulter 10" worked great.

Phil Wheeler wrote:
Doc wrote:

I've been experimenting with a Meade 5" reflector, and find that the
Moon looks incredible, but when looking at Mars, with anything of
greater mag power than the 25mm eyepiece such as a 9mm or 4mm, the
image even at sharpest focus I can manage has traces of an
irregularity most noticeable around the edges, sort of like an
impressionist painting.

Is this likely caused by imperfections in the mirror being magnified
or something else?


It could be:

o Seeing/atmosphe Much more of an effect at high mag. How high was
Mars?

o Eyepieces: If they (9 mm, 4 mm) came with a 5" reflector, they are
likely of low quality.

I'm using a new 8" SCT (cleaned and collimated at the factory two weeks
ago) on Mars and with my skies I'm having trouble getting sharp views
most nights using excellent EPs. OTOH .. one early morning in early
July, I was able to take my 5" SCT to 300x and get some really good views.

So it could easily be that conditions do not support the magnification
you are using.

Phil

On 22 Aug 2003 05:05:17 -0700, (Doc) wrote:

I've been experimenting with a Meade 5" reflector, and find that the
Moon looks incredible, but when looking at Mars, with anything of
greater mag power than the 25mm eyepiece such as a 9mm or 4mm, the
image even at sharpest focus I can manage has traces of an
irregularity most noticeable around the edges, sort of like an
impressionist painting.

Is this likely caused by imperfections in the mirror being magnified
or something else?

I have a 6" Newton reflector, at the beginning of the month, I had
more or less the same problems, and couldn't decide if the fault was
the scope, the eyepiece or the seeing conditions, or even heat haze
(living in London trying to find a dark sky, is like trying to find
Lord Lucan).
However I bought a couple of new eyepieces, Meade 9mm and 4mm Plossl
ones, and a minus violet filter.
Using the 4mm Eyepiece, a 3x barlow and the minus violet filter,
cleared up this fringing, BUT only when mars was above 15 degrees,
below that i have to fight heat haze and sodium street lighting.

I got the best views so far early this am, could quite clearly see
Both icecaps and the equatorial region, and I suspect I saw Deimos,
sadly i couldn't hold it long steady long enough (and that
magnification, even the effort of focusing is enough to knock it off
axis) to confirm it.

As Both Neptune and Uranus are in the same part of the sky, I looked
at both of those prior to viewing mars, and again, it seems the
combination of the new eyepieces and the new filter have taken that
fringing away.

Saturn should be somewhere around 8-10 degrees above the horizon at
around 01:30 tomorrow in gemini somewhere around the moon, and I am
hoping to get a good seeing tonight, and see if this same set up
clears up the fringing i usually get from Saturn.
I would also love to try this on Jupiter as well, but sadly Jupiter is
in the same sky as the sun at this time of year

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On 22 Aug 2003 05:05:17 -0700, (Doc) wrote:

I've been experimenting with a Meade 5" reflector, and find that the
Moon looks incredible, but when looking at Mars, with anything of
greater mag power than the 25mm eyepiece such as a 9mm or 4mm, the
image even at sharpest focus I can manage has traces of an
irregularity most noticeable around the edges, sort of like an
impressionist painting.

Is this likely caused by imperfections in the mirror being magnified
or something else?

I have a 6" Newton reflector, at the beginning of the month, I had
more or less the same problems, and couldn't decide if the fault was
the scope, the eyepiece or the seeing conditions, or even heat haze
(living in London trying to find a dark sky, is like trying to find
Lord Lucan).
However I bought a couple of new eyepieces, Meade 9mm and 4mm Plossl
ones, and a minus violet filter.
Using the 4mm Eyepiece, a 3x barlow and the minus violet filter,
cleared up this fringing, BUT only when mars was above 15 degrees,
below that i have to fight heat haze and sodium street lighting.

I got the best views so far early this am, could quite clearly see
Both icecaps and the equatorial region, and I suspect I saw Deimos,
sadly i couldn't hold it long steady long enough (and that
magnification, even the effort of focusing is enough to knock it off
axis) to confirm it.

As Both Neptune and Uranus are in the same part of the sky, I looked
at both of those prior to viewing mars, and again, it seems the
combination of the new eyepieces and the new filter have taken that
fringing away.

Saturn should be somewhere around 8-10 degrees above the horizon at
around 01:30 tomorrow in gemini somewhere around the moon, and I am
hoping to get a good seeing tonight, and see if this same set up
clears up the fringing i usually get from Saturn.
I would also love to try this on Jupiter as well, but sadly Jupiter is
in the same sky as the sun at this time of year

www.airporttransfers.biz
Fixed price transfers
from all of Londons airports
Hotel Directory
Tourist Guides
Call us on 0700-AIRTRANS or +44-(0)870-7777-647
Gatwick, Stansted, Heathrow, Luton
we cover all airports and docks