Design: 6 inch Dobsonian operating at f/8.Description: Medium reflector on a Dobsonian mount. It ships with two Plossl eyepieces (25mm and 10mm) and a 6x30 finder scope.
I have been an active amateur for over
twenty five years and owned about
15 scopes in this period ranging
from modest home brew Dobsonians to a 3.5” Questar. In addition I have had
numerous opportunities to use other scopes of all sizes and types ranging from
2.4” to 14” in size and from AP to Tasco on the manufactures end. In the
past several years I downsized my collection to retain the only some smaller
more portable scopes but realized I got too zealous in these efforts. I decided
to get back a little aperture (with portability) and, after a little homework (
which included a make vs. buy decision), elected to purchase a 6” Discovery
DHQ. Thus far I think I made a very good decision.
The scope was received in five business days
from the order date and arrived in perfect condition. Assembly was easy and
rapid, but I’ve been down this road several times before. The instructions
included, in my opinion, would be clear enough for any rookie to follow without
need to use four letter
They are some nice touches to the Discovery
scopes. The ground boards have a nylon bushing to prevent enlargement of the
central bolt hole for the azimuth axis. In addition there is a center teflon
pad, bored through to accept the bolt, that absorbs the weight over this part of
the mount. Azimuth motions were good right from the box , but I found that a
single slim washer from a milk jug placed over the center teflon pad improved
the motion to excellent. A washer cut from a thicker jug proved to be a bit too
much - so it was pretty close to perfect right from the factory.
The altitude motion was equally smooth and
the scope can be adjusted for balance by using the sliding bearings, which are
standard for the DHQ models. My personal preference was not to be bothered by
having to adjust bearings when eyepiece weight changes dictated the need. To
avoid this problem I set the bearings in a best balance position with a common
eyepiece and then installed tension springs on the bolt for each bearing
(Sears Hardware was my source). The spring tension can be adjusted if
needed via turnbuckles attached to the opposite ends of the springs. The
turnbuckles themselves fasten with a hook to screen door handles located on each
side of the rocker box. The handles are also serve to transport the base. This
arrangement gave me exactly what I desired.
focuser has some of the smoothest motion I had ever experienced from a
“non-premium” model. This appears to be the same model they use in their
8" DHQ scopes. I can detect no image shift. I did note that the focuser
tube came quite close to jutting into the optical path. This might present a
problem with some eyepieces but I have had no problem with several different
types that I have used with the scope so far. This includes TV Plossls, both old
and new Celestron silver top Plossls, generic Orthoscopics ( real close
though!), Brandons, and Meade RG Erfles)
I ordered the standard plate glass mirror.
The mirror cell allows for quick sufficient cooling and permits easy adjustment.
The scope arrived in almost perfect
collimation. However, I decided to give it some fine tuning and ran into the
usual problems I have experienced with trying to adjust a secondary on less
expensive units. This takes some time and patience and might be the biggest
challenge facing a “newbie”. It always seems that every time you to try to
lock in on your adjustment another bolt/setscrew loosens a little.
The only other adjustment I made to the
stock assembly was to add some Protostar black flocking opposite the focuser and
near the mirror.
The 6x30 was acceptable. No problems with
reaching focus and the eye relief
permits use when wearing glasses. There is edge aberration but not enough that
it bothered me.
Acceptable. Not terrific, but better than
the types I've seen provided on some other models. It's also nice to get two
focal lengths standard with the scope.
Nice to have a “bigger” scope that fits
in a Prism. The mount rides in the passenger seat and the tube fits nicely in
the rear. The size of the scope
also permits my 6-foot frame to view zenith to horizon while seated on
The optics proved to be a very good value
for the money. On steady nights
after reaching thermal equilibrium the images snap right into focus. I cannot detect any significant aberrations. Planetary images
are quite pleasing and comparable to what I have seen in 3 other quality 6”
reflectors I have used/owned. In this category I include an older Meade mirror
in custom tube assembly, a vintage Criterion Dynascope, and a handmade mirror by
an experienced ATMer. It surpassed three other 6” commercial Newtonians for which I was able to check
collimation and use for a longer period of time than just casual observations.
On good evenings with steady seeing I was
able to boost the magnification to over 400x for some work on tougher doubles (
less than 2.0”separation and/or 2 to 3 magnitude differences). The images held
very nicely but I was even more surprised that I was able to track these stars
without too much trouble using a small dob mount. Other experienced members in
my club who have viewed through this scope have all been favorably impressed
with the image quality.
I think Discovery is offering a very good
product in a starter scope range if mine is an example of a typical production
model. I might advise potential buyers to also consider their 8” DHQ –
aperture is king after all – since the weight is still reasonable, the mount
is the same size, and tube length the same. But for those who need to pinch
pennies or really want or need a smaller scope,
the 6” DHQ should give a purchaser a
Submitted by Larry
Janowicz - firstname.lastname@example.org
River Astronomical Society