Design: 12.5 inch Dobsonian operating at f/5.Description: Large reflector on a Dobsonian mount. It ships with two Plossl eyepieces, a moon filter, and 7x50 finder scope along with premium Pyrex mirrors (standard). The PDHQ is the premium model which also includes 96% reflectivity coatings on the mirrors and an excellent 2" JMI Crayford focuser.
ordered this premium Dobsonian from Discovery on November 20, 2000. It
arrived in the subsequent millennium, March 31, 2001. Good things are
worth waiting for. As it turned out, I did not miss a lot of viewing days
during that time. On the few crisp, cool late fall evenings we had in
Wisconsin last year, I enjoyed getting out and using my Orion SVD 90. That's a
lot of fun until the middle of December when the bone marrow finally freezes
over, about the same time as Lake Geneva does, and stays frozen like the lake
until at least April. There was only a handful of clear nights during that
time this winter any way. All in all, the long delivery time wasn't much of a
had decided on the Discovery 12.5" for all the right reasons. Also
because the Discovery ad featured a modest, but very intriguing young lady
climbing a telescope. It was subsequently pointed out to me that she was
standing on a step ladder, but that was not what I originally saw looking at the
"right" reasons I mentioned are all listed in Discovery's their
informational literature. Enhanced aluminum coatings on both primary and
secondary mirrors. Discovery Telescopes optical facility manufactures and
claims it tests its Premium Pyrex optics to the highest standards.
"Premium" optics means a 94% reflectivity, compared to the industry
standard 89%. Discovery does not use mass produced, spot checked, imported
duty metal (not wood) mirror mount, welded construction for tube
ventilation. Collimating doesn't require tools. Exclusive oversized
adjustable tube bearings advertised for precise balance and ultra smooth motion.
High quality Dobsonian mount crafted from strong, lightweight Baltic Birch
PDHQ is the most professionally attractive looking of the comparable products,
in my opinion. You can say what you want about the Starsplitter or the
Starmaster quality, they look home-made to me. They are a lot more expensive.
From what I hear, Discovery makes a really fine mirror. I don't think the
optics could be significantly better. Check me on that.
doesn't offer a 12.5". As much as I like Orion, none of Orion's products
are really comparable to this. I went through a lot of soul searching in
settling on a 12.5" and the decreased portability over a smaller Dob.
Discovery makes the same 'scope in a 10", which would have been less
expensive and lighter, with an f/6 vs. an f/5. That would be desirable
because less coma, greater contrast and smaller central obstruction. A
10" is only 64% of the aperture of a 12.5" though. I'm big and
healthy. Damn the torpedoes, full speed ahead.
PDHQ was delivered on a semi, and needed it. It was a large shipment, costing
$114. It came largely pre-assembled in four, very large boxes. Unpacking
contents was a trip, the Jackals cackles. The packaging was quite well thought out, tight and secure. The size was really impressive. Definitely worth the price of admission. In removing the tube, stand, bearings and mirror from the packaging, one is extremely impressed. One wonders how one could get so much cool stuff for only a grand, or so. It should easily cost $1,500. All the assembly needed is to tighten the four pieces together, and BAM, one has a BIG telescope.
at the fringe. In fact, I had also chosen the 12.5" because I thought
I could transport it diagonally in the back of my Ford conversion van. I
had build a mock-up to test the fit but it seemed to be about an inch too long.
What to do. I talked to Discovery, and they had a couple of inches
to work with and were able to shorten mine one inch from spec. Low and behold,
it fits diagonally as needed!
cautions. The objective mirror comes wrapped in lens paper adhered with
masking tape. Bad. In trying to pick off a tape remnant, I inevitably (for
me) touched the surface of the mirror with a finger. A hair net like device made
of lense paper and elastic would work better, in my opinion. Also, the
bearings need to be attached with the screws, which hold the Formica strips, on
the top. Until I figured this out, the bearings were bumping over the
screws as the scope moved in altitude. All in all, its really an
impressive and handsome piece of equipment to receive and assemble.
Other than that, set up went breezily. My daughter helped with the balancing, which went normally. I read in a review of the 10" f/6 version of this scope that heavier eyepieces and equipment mounted on the front require extending the balance of the scope downward, blocking movement toward the zenith. This is definitely not a problem with the 12.5" f/5 scope, the heavier mirror providing the counterbalance necessary without additional extension. I can lean it over backwards from zenith w/no problem. I presume it would not be a problem with the larger versions, either.
The price went up a little after I ordered mine. It doesn't matter. This product is easily worth $500 more than it sells for. I don't know how they make a living grinding these things out for the $1,249 they now cost, with all the nonsense they have to put up with. Replacing the sliding door in my kitchen is going to cost $1,500! I optioned the Crayford focuser which now comes standard. I would have preferred a collimating eyepiece in place of one of the ubiquitous no-name Plossls. Or nothing. They're becoming as numerous as packing foam. Discovery, if you want to really shock the industry, include a University optics orthoscopic or Konig or a collimating eyepiece instead. I'd also prefer a right angle finderscope.
only real complaint is that the focuser is mounted too low on the arch of the
tube. Looking down the throat of the tube, it is mounted at about 80
degrees from the top. This results in the eyepiece being too low when looking
other than at near zenith, and requiring a crouch. I would rather stand
over the eyepiece, looking down and it would be more suitably mounted at about
25 degrees from the top. The problem can be corrected by rotating the tube
in the mounting bearings, but this would require some disassembly and
reassembly, which I'm not up to. Also, Discovery usually mounts the focuser on
the right side of the tube as you use the scope. I specially requested it
to be on the left side as you use the scope, because I get the eastern sky from
my back yard and I like to push on the tube rather than pull. That worked out.
There is no point in my going into the optical quality of this 'scope. It's good beyond my ability to be critical. I haven't the expertise to do so; one can find it elsewhere. It's top of the line. Suffice to say, I can't wait to get out to the dark!
by Jay Mack - Zedoc@techheadnet.com
- Twin Lakes, Wisconsin