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Discovery DHQ 6 Inch Dobsonian

 


 

Price:  $339.00

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. 

 

The Review

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 epithets.

Mechanics and Design

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.

 The 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.

Finder

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.

Supplied Eyepieces

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.

Field Use

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 campstool.

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  great experience.

Submitted by Larry Janowicz - hijano@bright.net - Black River Astronomical Society