Orion 90mm AZ refractor - review, comparison, observing report

Orion Explorer 90mm AZ - review, comparison, observing report(s)

When I was in my teens and early 20's I had an interest in astronomy.
Starting off with a pair of 7x35 binocs I learned most of the summer
constellations. It was the family summer vacation to the bay of
Islands (MacGregor bay, northern lake Huron) that deepened my interest
in Astrononmy as a hobby. With the bulk of lake Huron the south, and
the area to the north sparsely populated, the night sky was pristine.
It was here that I got my first really good look at the milky way,
especially through Sagittarius. My brother and I decided we'd have to
get some sort of scope to check things out.

I eventually ended up ordering a pair of 11x80's binocs and a small
(5.5") fast reflector (from Orion). No regrets. The view of Andromeda
through the 11x80's was stunning, and this alone justified the
purchase as far as I was concerned. Many happy memories.

Well, that nice little reflector ended up getting stolen from my
parents back lawn, and I ended up selling the 11x80's to pay for rent
one month a couple years after purchasing it. Unfortunately the 11x80's
really only came into their own under a dark sky, which I seldom see
where I live (madison, wi). Too much light pollution.

That was close to 20 years ago now, but recently I got the desire to
purchase another scope (in addition to 7x50 binocs I have).
Looking through the latest Orion catalog was bewildering. So many
scopes to choose from! This time I wanted to try a refractor. I
was quite tempted by the 100 and 120mm refractors, but I decided these
were just too fast for a crown&flint doublet. I still wanted to use
the scope for planetary viewing. Also, I wanted an alt-az mount.
I think EQ mounts are more of a liability than an asset for visual
observing. Needlessly complex and heavy. So I eventually decided on
the 'Explorer 90mm AZ' from Orion. At f/10 I hoped the chromatic
aberration would be low enough for planetary viewing at higher
powers.

The scope was $300, and I also purchased a 40mm 'Sirius plossl' to
go with the two eyepieces that came with the scope (25 and 10 mm
plossls - 23x, 36x, 91x respectively). The entire package with
shipping came to about $375.00. Yes my budget was very limited. I
would LOVE one of one those ED or APO refracters (100-120 mm) but
considering how seldom I observe I have trouble justifying the price
(5 - 15x more than I paid).

I placed my order about a week and half ago, and feeling like a kid
before X-mas I very impatiently waited for it to arrive. It arrived
on August 30th. I took it out that night with a friend and his Intes
130mm Mak. I also took it out (all night) on Sept. 2, and a bit
last night (Sept. 3) and was able to compare it to a friends 8" Meade
SCT (scope circa early 80's).

The scope arrived well packed. The OTA was wrapped in vellum like paper
and a ouple of sheets of bubble wrap and double boxed. I had to take
a few pictures of the optics while they were still spotless and dust
free.

The Scope after I just set it up. The OTA is enameled aluminum. Note
that I had yet to install the 6x26 'correct-image' finder nor the 45
degree correct-image diagonal (A friend gave me one of his 90 degree
prism diagonals - a decent Japanese unit. I used this for all the
astro. observing. I have yet to try out the 45 degree diagonal that
came with the scope).
http://www.fractalfreak.com/astro/scope2.jpg

Picture of the objective. The few colored dots are hot pixels in the
camera. Lens is nicely coated with some sort of multi-coating. a light
green/purple cast:
http://www.fractalfreak.com/astro/scope1.jpg

The eyepieces. From left to right: 10 mm, 25 mm (these two came with
scope), 40 mm (ordered separately - this is the best eyepiece).
http://www.fractalfreak.com/astro/eyepieces.jpg

I'm not an equipment freak, so I'm not going to measurebate endlessly
on the quality of the OTA paint job or how well the focuser
works. Considering the price everything is excellent. The mount is
adequate - a little more plastic than I'd like to see, but it's nice
and light. The accessory tray mates to some plastic thingies on
the tripod legs, and the aluminum tripod legs are capped with plasic
feet and attach to the cast iron alt-az mount via some plastic end
bits and screws. Quite straightforward. The alt-az mount does
have some backlash when used in the field (handguided), but that's
what the slo-mo controls are for. Though they are screw based so
they've got to be reset periodically. Most of the time I didn't use
the slo-mo controls and simply guided the scope by grabbing its base
and moving it. I'm certain this mount will not be the most stable
in any sort of wind, but in the field, and at the magnifications used
( 150x ), it worked fine.

In the field the finder was easy enough to use. The long tube of
the refractor makes aiming a cinch, though near the zenith I
often found myself crouched down or on my butt while finding stuff,
and there is some neck strain involved. The mount does tend to
'break down' a bit while trying to look at stuff directly overhead.

On to how things look *though* the little beast. The scope
was not tested used under pristine skies unfortunately. Both locations
were quite suburban. The first site offered a good view of the the
south and west skies, and the second site, while still in the city,
offered a good view of the northern sky by virtue of being on the
southern shore of lake Mendota. ZLM was arounnd 5-5.5 and seeing
and transparency were average.

The first view through the 40mm eyepiece was excellent. I knew right
away the scope was good. I also had a friend along with his 130mm
Intes Maksutov Cassegrain (f/15?) - a fine little scope. So I was able
to get a second opinion and compare it to the Intes. The 40mm plossl
served up a solid degree of sky, and the view were surprisingly bright.
Stars looked great - round and tack sharp. We compared the views in
the two scopes using the 40mm eyepiece. The view in the refractor
offered more contrast. It was subtle, but the background sky was a tad
darker in the refractor, and the stars just looked a touch harder and
more pleasing. Surprisingly we found the refractor to be better at
DSO stuff - those faint fuzzy monochromatic critters. For example,
while looking at M27 we both thought the view in the refractor, while
not as bright as the Intes, offered just a bit more detail. It was at
higher powers that the Intes pulled ahead, with its greater aperture,
larger image scale, and lack of CA.

The views in the 25mm were still excellent, but just a touch of CA
began to creep in around the brightest stars. The 10mm plossl was
mediocre - it's eye relief and field of view were so-so, and it
added noticable chromatic abberation to things.

On to the observing list:

M13: Was nicely served in the little refractor, probably looking best
in the 25mm. It simmered with stars on the threshold of visibility,
and positively seethed with stars using averted vision.

M57: Lovely. The contrast was excellent, and compared to the background
stars it appeared to float 3-D like in front of them. Even in the 10mm
its ring shape was faint but evident looking straight at it, and
obvious using averted vision.

M71, M56: - these clusters were nice. Just a few of the outer stars
were resolved, but they looked distinctly granular, especially using
averted vision.

M31, 32, 110 (Andromeda and company): As one would expect this looked
best in the 40mm. Even large scopes show little detail in this object,
beyond being large and bright. I still think Andormeda looks best in
binocs.

M103 and other open clusters in Cassiopea - looked great at low power.

M81 and M82 - Not enough aperture to show much in these objects,
especially with them low in the sky. I swear I may have glimpsed
a dust lane or two bisecting the center of M82 using averted
vision though.

M27: The dumbell shape was easy to note, especially using averted
vision.

I'm not a big double star fan - at really high powers all you're
really looking at are interefernce rings. Still, Polaris was an
easy split at all magnifications, with its (9th mag?) companion
evident in the one o'clock position. Albireo was nice too, looking
best in the 40mm. Several of the multiple stars in Lyra were evident
as elongated and obviously not single stars, but I needed more power
to split them cleanly.

The pleiades were nice, just fitting the field the in the 40mm.

Mars. Mars was the planetary test, and this scope came through.
Using the 10mm (91x) Mars clearly showed its waxing disk, over
3/4's full. I played the game of planetary observing, waiting for
moments of good seeing to pour all my attention onto the trembling
little disk. Even in a large scope I wouldn't call the surface markings
on Mars high contrast. Despite the light violet fringing and tiny
size of the disk I was able to see surface details! I could make
out a broad distinct horizontal feature on the bottom half of the
disk, and a couple other dusky markings on the top half. The
polar cap winked in and out on the top of the disk (seeing
permitting) and it appeared to be ringed by a darker region. I was
transfixed, and spent a lot time looking at Mars. I needed higher
power. I think that with a higher power eyepiece (120-200x) and
perhaps a minus violet filter this little pup will make an excellent
plantary scope. I can hardly wait to gaze upon Jupiter and Saturn
with it!

Critical notes...

Color. This scope is a f/10 crown and flint doublet, so one would
expect some color fringing, and there was, but it was really only
obvious around the brightest stars (and Mars). Using the 40mm there
was essentially no false color, even on a star like Vega. Going
up to 25mm the beautiful charged blue of Vega became ringed with
an aura of deeper blue, but it was still not bad. In the 10mm
Vega was badly fringed. Looking at mars in the 10mm revealed
a considerable violet aura, extending over half the distance
radially as the planet itself - but it was quite faint and low
contrast features on the tiny Martian disk could still be seen (I
think much of the CA on mars may have been due to the eyepiece).
The CA was about was I was expecting. And on nearly all (fainter)
stars it's just not evident. This doublet does appear to be corrected
better in the reds than the blues. Blue stars had a slight green tinge
- for example all the Pleiades had a subtle but distinct green cast,
especially evident when comparing the view to the Intes or the
Meade SCT.

All and all I'm very pleased with this scope. I think considering the
price it's excellent, and it would hold its own (or likely exceed)
the view through any other 90mm scope out there.

-Eric B

Thanks Eric for your report
It is always useful.
Remain to digest all this ;-)

Thierry
http://www.astrosurf.org/lombry

wrote in message
oups.com...
Orion Explorer 90mm AZ - review, comparison, observing report(s)

When I was in my teens and early 20's I had an interest in astronomy.
Starting off with a pair of 7x35 binocs I learned most of the summer
constellations. It was the family summer vacation to the bay of
Islands (MacGregor bay, northern lake Huron) that deepened my interest
in Astrononmy as a hobby. With the bulk of lake Huron the south, and
the area to the north sparsely populated, the night sky was pristine.
It was here that I got my first really good look at the milky way,
especially through Sagittarius. My brother and I decided we'd have to
get some sort of scope to check things out.

I eventually ended up ordering a pair of 11x80's binocs and a small
(5.5") fast reflector (from Orion). No regrets. The view of Andromeda
through the 11x80's was stunning, and this alone justified the
purchase as far as I was concerned. Many happy memories.

Well, that nice little reflector ended up getting stolen from my
parents back lawn, and I ended up selling the 11x80's to pay for rent
one month a couple years after purchasing it. Unfortunately the 11x80's
really only came into their own under a dark sky, which I seldom see
where I live (madison, wi). Too much light pollution.

That was close to 20 years ago now, but recently I got the desire to
purchase another scope (in addition to 7x50 binocs I have).
Looking through the latest Orion catalog was bewildering. So many
scopes to choose from! This time I wanted to try a refractor. I
was quite tempted by the 100 and 120mm refractors, but I decided these
were just too fast for a crown&flint doublet. I still wanted to use
the scope for planetary viewing. Also, I wanted an alt-az mount.
I think EQ mounts are more of a liability than an asset for visual
observing. Needlessly complex and heavy. So I eventually decided on
the 'Explorer 90mm AZ' from Orion. At f/10 I hoped the chromatic
aberration would be low enough for planetary viewing at higher
powers.

The scope was $300, and I also purchased a 40mm 'Sirius plossl' to
go with the two eyepieces that came with the scope (25 and 10 mm
plossls - 23x, 36x, 91x respectively). The entire package with
shipping came to about $375.00. Yes my budget was very limited. I
would LOVE one of one those ED or APO refracters (100-120 mm) but
considering how seldom I observe I have trouble justifying the price
(5 - 15x more than I paid).

I placed my order about a week and half ago, and feeling like a kid
before X-mas I very impatiently waited for it to arrive. It arrived
on August 30th. I took it out that night with a friend and his Intes
130mm Mak. I also took it out (all night) on Sept. 2, and a bit
last night (Sept. 3) and was able to compare it to a friends 8" Meade
SCT (scope circa early 80's).

The scope arrived well packed. The OTA was wrapped in vellum like paper
and a ouple of sheets of bubble wrap and double boxed. I had to take
a few pictures of the optics while they were still spotless and dust
free.

The Scope after I just set it up. The OTA is enameled aluminum. Note
that I had yet to install the 6x26 'correct-image' finder nor the 45
degree correct-image diagonal (A friend gave me one of his 90 degree
prism diagonals - a decent Japanese unit. I used this for all the
astro. observing. I have yet to try out the 45 degree diagonal that
came with the scope).
http://www.fractalfreak.com/astro/scope2.jpg

Picture of the objective. The few colored dots are hot pixels in the
camera. Lens is nicely coated with some sort of multi-coating. a light
green/purple cast:
http://www.fractalfreak.com/astro/scope1.jpg

The eyepieces. From left to right: 10 mm, 25 mm (these two came with
scope), 40 mm (ordered separately - this is the best eyepiece).
http://www.fractalfreak.com/astro/eyepieces.jpg

I'm not an equipment freak, so I'm not going to measurebate endlessly
on the quality of the OTA paint job or how well the focuser
works. Considering the price everything is excellent. The mount is
adequate - a little more plastic than I'd like to see, but it's nice
and light. The accessory tray mates to some plastic thingies on
the tripod legs, and the aluminum tripod legs are capped with plasic
feet and attach to the cast iron alt-az mount via some plastic end
bits and screws. Quite straightforward. The alt-az mount does
have some backlash when used in the field (handguided), but that's
what the slo-mo controls are for. Though they are screw based so
they've got to be reset periodically. Most of the time I didn't use
the slo-mo controls and simply guided the scope by grabbing its base
and moving it. I'm certain this mount will not be the most stable
in any sort of wind, but in the field, and at the magnifications used
( 150x ), it worked fine.

In the field the finder was easy enough to use. The long tube of
the refractor makes aiming a cinch, though near the zenith I
often found myself crouched down or on my butt while finding stuff,
and there is some neck strain involved. The mount does tend to
'break down' a bit while trying to look at stuff directly overhead.

On to how things look *though* the little beast. The scope
was not tested used under pristine skies unfortunately. Both locations
were quite suburban. The first site offered a good view of the the
south and west skies, and the second site, while still in the city,
offered a good view of the northern sky by virtue of being on the
southern shore of lake Mendota. ZLM was arounnd 5-5.5 and seeing
and transparency were average.

The first view through the 40mm eyepiece was excellent. I knew right
away the scope was good. I also had a friend along with his 130mm
Intes Maksutov Cassegrain (f/15?) - a fine little scope. So I was able
to get a second opinion and compare it to the Intes. The 40mm plossl
served up a solid degree of sky, and the view were surprisingly bright.
Stars looked great - round and tack sharp. We compared the views in
the two scopes using the 40mm eyepiece. The view in the refractor
offered more contrast. It was subtle, but the background sky was a tad
darker in the refractor, and the stars just looked a touch harder and
more pleasing. Surprisingly we found the refractor to be better at
DSO stuff - those faint fuzzy monochromatic critters. For example,
while looking at M27 we both thought the view in the refractor, while
not as bright as the Intes, offered just a bit more detail. It was at
higher powers that the Intes pulled ahead, with its greater aperture,
larger image scale, and lack of CA.

The views in the 25mm were still excellent, but just a touch of CA
began to creep in around the brightest stars. The 10mm plossl was
mediocre - it's eye relief and field of view were so-so, and it
added noticable chromatic abberation to things.

On to the observing list:

M13: Was nicely served in the little refractor, probably looking best
in the 25mm. It simmered with stars on the threshold of visibility,
and positively seethed with stars using averted vision.

M57: Lovely. The contrast was excellent, and compared to the background
stars it appeared to float 3-D like in front of them. Even in the 10mm
its ring shape was faint but evident looking straight at it, and
obvious using averted vision.

M71, M56: - these clusters were nice. Just a few of the outer stars
were resolved, but they looked distinctly granular, especially using
averted vision.

M31, 32, 110 (Andromeda and company): As one would expect this looked
best in the 40mm. Even large scopes show little detail in this object,
beyond being large and bright. I still think Andormeda looks best in
binocs.

M103 and other open clusters in Cassiopea - looked great at low power.

M81 and M82 - Not enough aperture to show much in these objects,
especially with them low in the sky. I swear I may have glimpsed
a dust lane or two bisecting the center of M82 using averted
vision though.

M27: The dumbell shape was easy to note, especially using averted
vision.

I'm not a big double star fan - at really high powers all you're
really looking at are interefernce rings. Still, Polaris was an
easy split at all magnifications, with its (9th mag?) companion
evident in the one o'clock position. Albireo was nice too, looking
best in the 40mm. Several of the multiple stars in Lyra were evident
as elongated and obviously not single stars, but I needed more power
to split them cleanly.

The pleiades were nice, just fitting the field the in the 40mm.

Mars. Mars was the planetary test, and this scope came through.
Using the 10mm (91x) Mars clearly showed its waxing disk, over
3/4's full. I played the game of planetary observing, waiting for
moments of good seeing to pour all my attention onto the trembling
little disk. Even in a large scope I wouldn't call the surface markings
on Mars high contrast. Despite the light violet fringing and tiny
size of the disk I was able to see surface details! I could make
out a broad distinct horizontal feature on the bottom half of the
disk, and a couple other dusky markings on the top half. The
polar cap winked in and out on the top of the disk (seeing
permitting) and it appeared to be ringed by a darker region. I was
transfixed, and spent a lot time looking at Mars. I needed higher
power. I think that with a higher power eyepiece (120-200x) and
perhaps a minus violet filter this little pup will make an excellent
plantary scope. I can hardly wait to gaze upon Jupiter and Saturn
with it!

Critical notes...

Color. This scope is a f/10 crown and flint doublet, so one would
expect some color fringing, and there was, but it was really only
obvious around the brightest stars (and Mars). Using the 40mm there
was essentially no false color, even on a star like Vega. Going
up to 25mm the beautiful charged blue of Vega became ringed with
an aura of deeper blue, but it was still not bad. In the 10mm
Vega was badly fringed. Looking at mars in the 10mm revealed
a considerable violet aura, extending over half the distance
radially as the planet itself - but it was quite faint and low
contrast features on the tiny Martian disk could still be seen (I
think much of the CA on mars may have been due to the eyepiece).
The CA was about was I was expecting. And on nearly all (fainter)
stars it's just not evident. This doublet does appear to be corrected
better in the reds than the blues. Blue stars had a slight green tinge
- for example all the Pleiades had a subtle but distinct green cast,
especially evident when comparing the view to the Intes or the
Meade SCT.

All and all I'm very pleased with this scope. I think considering the
price it's excellent, and it would hold its own (or likely exceed)
the view through any other 90mm scope out there.

-Eric B