Hi Todd,

I thought you might find my notes this past year of some interest.

Observations and notes on 4 inch Apo refractors:

My first 4 " APO refractor was a Genesis SDF.   I purchased it second hand in
1995.  My first choice  would have been the AP Traveler but due to the long
wait and the relatively high cost at the time I elected to start with the
Genesis SDF while I saved.  I journeyed along the way and ran into a C102F and
a 94 Brandon.  The only popular one I’ve not used is the Takahashi.

Genesis SDF

A great scope but its size at about 32" was very long for a fast f/5.4 scope.
The two element ED objective is an f/12 making it a much longer scope than the
Traveler at 19".  A two element, one of which is flourite,
corrector/flattener, gets the scope down to f/5.4. The newer TV 101 uses the
same configuration but as I understand it, better color corrected.  I didn’t
own any of the better TV eyepieces at the time to fully exploit this scope’s
capabilities.   This was a scope that was exceptionally well made.  I owned a
Super C8 Plus, an RV-6, a C-6 and a 80mm Brandon prior this scope.   The
Genesis was in another league in terms of precise construction and quality of
materials.

Star testing showed nice concentric rings on either side of focus.   The scope
provided very sharp, mostly color free images.   When the stars were taken out
of focus, a little green color was evident as well as occasional hint of color
on stars and the limb of the moon.   M13 split nicely but the I found the
light gathering to be a touch short, as it was only a 4" scope.   But one
can’t help but think that the extra two elements would rob a bit of light or
detract some contrast, even if it was just one’s imagination.   Hale-Bopp and
Hyakutake were around and I used this scope to observe them on many nights.
The lowest power eyepiece I had at the time was a 35mm Ultima.   It would not
come to focus with the TV 2 inch diagonal and the TV 2 to 1.25 inch adapter.
It lacked sufficient "in-travel".   By attaching the 2" - 1.25 inch adapter
to the drawtube and using a Celestron 1.25 inch diagonal I was able to get the
35mm Ultima to focus.    Along with the Celestron diagonal came a bit of
astigmatism.

I mounted this on a Super Polaris mount and found it to be portable set-up but
no more so than a C-8.   I had ok views of Mars but never really had good
seeing.   The moon was very nice in every way, sharp and contrasty.   The
views of the comets were very nice but surprisingly I found that in my
suburban setting,  my C-6 newtonian with the f/5 mirror provided better wide
field views with the 35mm Ultima.  The comet was brighter, just enough so to
make it more impressive.    High power views favored the Genesis but I spent
most of my time focusing on the wide field views of the comet and other deep
sky objects.

I always eyed a 3.5 inch Questar growing up but was way out of the budget.  So
I was easily tempted by the ads for the new Meade ETX and decided to buy one.
While it’s amazing how small and light the ETX was, the performance was even
more so, super impressive.   Keeping up with the Genesis on some days.   I
decided that the relatively bulky Genesis SDF did not serve my needs as well.
I had a wide field scope, the C6 that I preferred for wide field deep sky and
I had an ultra portable 3.5 inch that was perfect for carrying around the
backyard looking for openings between trees for viewing the moon and planets.
My RV-6 had better images all the way around and my C-8 was doing a good job
well.   Consequently I sold the Genesis SDF with the intention of getting a
compact AP Traveler someday.   In all fairness to the Genesis SDF, my findings
are somewhat subjective as I didn’t have another 4" apo on hand to compare
side to side.
 

Brandon 94
 

As Travelers were hard to come by, I imagined that the only other short scope
would be the 94 Brandon.
It turns out that it is around 24 inches but with the dew cap removed it’s
more like 20, making airline portable with a bit of work.   The prices were
about half of the Traveler as well.

This scope has excellent star tests but with a full moon partially in the fov,
I noticed a curved flare line
that comes and goes as you move the field.   I painted the edges of the
drawtube that was left chrome!  I then noticed that all the inside screws and
nuts were also left shiny so I blacken them as well.

Having done some minor painting my notes say:

Overall performance was very nice with wide field views and high power
available.   Low power with a 35panoptic gave 3.6 degrees and 19x.    I can
see slight green on the edges of the moon which detracts from performance.
High power views were better than ETX even with a shorter focal length, which
forced the use of a barlow.   Using a TV 3x barlow I was able to get 219x w/ a
9mm,  282x with a 7 and 143 with a 13.8mm.

It is a relatively heavy, solid scope.   Compact but heavy compared to say a
C5 or an ETX type of  construction.   The SPM mount provides a solid platform
to work with.   It weighs in at 8 lbs according to an old ad but the heavy
2inch diagonal makes it seem heavier than the much longer, larger C102F tube
assembly with a 1.25 inch diagonal.   The focuser is so, so but was improved
by using a teflon disc around the pinion.   I also noticed that rotating the
sliding drawtube created slight misalignment at certain points.   The set
screws should be at opposite each other in this particular scope for perfect
alignment.

1/25
Images of Saturn were very good after the seeing quieted down.  BeeHive
cluster was beautiful as was Pleiades with the 35 Panoptic.   Wide pin point
stars yet I’m bothered by the fact that contrast is not as good as the C102F.
More to come as I improve the baffling.
 
 

SP- C102F

This scope turned out to be a huge surprise.   The condition I received it
gave me pause.  There was a thick layer of dust on the lens and scratches on
the ota and tripod in many places.   The star tests were not great,  "falling
apart" effect on one side of focus, not unlike the 6/90 Astronomy report.
After carefully getting the lens clean,  the images were crisp, sharp and
contrasty with no color that was detectable.  Not like the 94 Brandon’s
occasional hint of green on the edge of the moon when slightly out of focus.
This scope was not of the same quality construction as a Genesis but certainly
well made.    A real benefit of the less robust construction was the light
weight.   It was so light that you can easily carry it with one hand.   Now if
only a Traveler was made like this instead of as an over built work of art
(I’m probably the only person to complain about the AP Traveler being made too
well).

The lunar detail is amazing but on one occasion when comparing to an AP
130EDT, it seemed to be affected more by seeing conditions.  Unusual to see
more waviness of images on a four inch versus a five.   Saturn is crisp,
coming to focus with a nice "snap".   But inch for inch this is as good as
I’ve seen.

 
3/4/98
Clear skies, at last.   Took out the ETX, 94 Brandon and C102F.   The moon was
at about 1/3 phase.

The ETX showed very nice views at low power but the field of view is narrow
with 35mm eyepiece.  Quickly pumped up the power.  Easily handled 180x with
7mm Nagler.  Using a 2x Orion barlow and a 9mm Nagler got me to 280x.  Still
decent but the best views were at 140x w/ the 9mm without the barlow.
Crispness of image is nice here.  At 7mm, 180x it is still very good and
sometimes preferable.

Next the 94 Brandon.  Beautiful wide field views and contrast, pin point
stars.  Clearly superior to the ETX as one would expect.  The 3x Televue
barlow and 9mm got to 219x.   Crisp contrast, like ETX at 140x.   Taking it up
to 282x w/7mm we still get a very nice view of the moon close-up.  This is the
reasonable limit as best views were had with 9mm at 219x.   At this point it
is clear that the 94 Brandon is a step up both in wide field and high power.
I would think that an ETX owner upgrading would be satisfied with this
upgrade.

Now the C102F.   I’m always shocked at how incredible the views are through
this instrument.  The contrast of dark and light is so great, you almost can’t
believe it’s natural.   I say to myself that I think it is better than the
Genesis SDF by a large margin.   It wouldn’t  surprise me if it betters the
Traveler.   Using 7mm at 128x is the start, very dark and light contrast.  3x
TV  barlow and 13.8mm gives me 195x.   9mm gives me 299x and 7mm 385x.
Easily handles 385x but the 9mm at 299x is probably the preferred view.   With
the 7mm I start to see floaters in my eye. At 95x per inch the C102F is still
very impressive.

Best view of the night is  140x ETX,  219x 94 Brandon, 299x C102F.

5/7/98  shootout
 

Very steady air, the Moon with the ETX with 2x barlow and 7mm got it to 355x,
or 100x per inch!.  Still pretty impressive views.  I can see as much detail
in Gassendi as my last view with poorer seeing and the AP 130EDT.  Contrast is
very good, resolution is excellent.   Using a .63 reducer and 2inch diagonal
the ETX showed excellent wide field views as well.  I remind myself to leave
the fork mount home and take an altaz mount with a tripod on my next trip.

I had been looking forward to checking out the performance of the 94 Brandon
as I spent some time lining the drawtube with black velvet.    Looking down
the drawtube while pointing at a bright light source showed a fair amount of
diffuse light reflecting from the drawtube walls.  To make the final touch a
teflon donut disc from a fishing reel drag was placed between the pinion and
the rack of the focuser.

Exquisite images,  higher contrast and resolution than ever before. I feel a
strong sense of accomplishment that the Roland Christian triplet now finally
has a decent housing to maximize it’s potential.  A 3x Barlow, 7mm, 9mm and
13mm.   Next the C102F, I didn’t think that it could get much better than my
views with the 94 Brandon.   But it is,   brighter, more resolution .   About
an 8mm difference I think in aperture.   But it’s just that aperture.  Before
it was a question of color, lack of contrast, etc.

I decide that the Brandon is an excellent scope but gives up a bit of aperture
to the C102F.  Globulars are really not good with either one.  But since I can
always get another Vixen flourite I decide to sell the C102F.    I figured
that the newer ones have a better 2inch adapter than the Lumicon adapter that
I’ve been using which seems to push the focus out about an 1 ¼ inch too far.
The 94 Brandon is no longer available so I decide to keep it.  Plus this one
has fantastic correction.
 
 

AP Traveler 105EDT

As I had a 130EDT and just received my 130EDF, I decided to trade my 130EDT
for a Traveler as no 155EDFS were to be had.    In fact it’s hard enough to
get a hold of any used AP’s so with one on hand it seemed better to just swap
out for another one.   That’s how I got hold of a Traveler.

This scope is better built than most of the other scopes that AP was making
during the "EDT" period as opposed to the newer EDF formulations.    The main
difference is that the tube assembly has machined baffles rather than
separately inserted baffles.    The newer EDF scopes all have machined baffles
and are a bit heavier as a result (there I go with the weight again).  The
workmanship is superb all around and is actually a jump up from the TV Genesis
SDF.   I didn’t expect that.
 

Optically I am still in the evaluation phase but it seems that the Traveler is
every bit the equal of the Vixen 102F at high powers.   The contrast is
superb, most likely due to superior baffling.   The low power views are great.
The size of the scope is nice and compact at 19 inches with the sliding dewcap
in the closed position.   I’ve had excellent views of Jupiter with this scope
as well as the Brandon this summer as my notes indicate but a conclusive
opinion will have to wait.
 

Thanks for reading.
Jae Park