Posts Made By: James Barnett

At the suggestion of several Astromarters, I've offered to send the entire OTA back to D&G at my own expense for troubleshooting. I'll keep you posted as to D&G's response and any remedial efforts undertaken.

Thanks!

Jim

UPDATE: I sent the objective to D&G at Barry's request via UPS on Friday morning.

I will keep the group apprised of what happens remedially.

- Jim

Well, I have one of each. I have a Vixen 102mm achromat and a Takahashi 78mm APO.

They are both great. The 4" Vixen goes much deeper than the 3" Takahashi. On M13, for example, it is NO CONTEST. The Vixen resolves many more stars. Similarly, on M42, the Vixen shows much, much more nebular detail.

On Jupiter, however, the Takahashi has an edge. It cannot handle quite as much magnification, but shows finer belt detail. For instance, I watched a beautiful shadow transit a few nights ago in the Takahashi. Inky black obvious shadow clear as crystal in the tiny 3".

I suppose the choice depends on what you are going to be viewing primarily and whether portability is a factor. For DSOs and even general observing, go with a quality 4". For portability and lunar and planetary, the 3" APO would be my choice.

Stephen:

Funny you should post. Just last weekend I was dusting off my venerable Celestron Ultima 2000, and found that she was in need of collimation.

I use Bob's Knobs, and have collimated the scope a handful of times. I use it infrequently - usually when I have non-enthusiasts over for a "star party."

For some reason, I was having exactly issues you describe when attempting to collimate mine. If you can, collimation "best practices" suggest that you do so in straight through mode (no diagonal) with a moderately high power eyepiece on a defocused second or thrid magnitude star.

The problem I was having was as you described - I seemed to keep running out of room on the screws, just as things were looking close to collimated. Another issue I faced was the fact that I would get it to look collimated on one side of focus, but when I went to the other side of focus, it did not look collimated.

At any rate, I got frustrated, and switched scopes for the night. In the morning, I did a rough collimation by looking onto the tube and making sure the shadow of the secondary was concentric with the primary (it was not and a couple of careful tweaks later it was).

That night, I star collimated, and didn't have the issues I had the night before. Moral of the story: once you get things so far out of kilter that you are hittng the screw limits, it's probably better to rough center everything in daylight looking down the tube, then patiently recollimating the next night.

Some years back the Orion Skyquest (old version with GSO optics) beat a similarly sized Discovery in a Sky & Telescope 5 or 6 way 8" Dob head to head. I would not assume that a Discovery is a better scope than a stock GSO, much less one with refigured mirrors.

Unfortunately the S&T article now requires registration with SkyPub and a fee to access their archive, but my recollection is that the Orion and one other GSO clone (Hardin?) came in #1 and #2, with the Discovery finishing either #3 or #4.

Neither of these scopes is a "premium" dob, and based on positive user feedback for both scopes and reviews showing them to be competitive in quality and performance, I would buy the least expensive of the two and use the savings to make upgrades (Moonlite focuser, internal flocking, cooling solutions, etc.) to suit my tastes.

Hi John. I didn't buy one, but I looked at one before buying an Orion XT12i.

I really liked the Meade overall. It's beautifully built for the price. The model I looked at was a 12" deluxe with the "lazy Susan" style needle bearing on the groundboard. It had nice motions in both altitude and azimuth.

I didn't look through it, so can't comment on the optics on that unit, but web evaluations of the optics, which are by Guang Shen of Taiwan, have been very positive. These GSO optics are also used in other low cost Dobs such as Hardin, etc.

What made me ultimately choose against the Lightbridge came down to three things:

(1) At the time, they were packing them like crap and many buyers were on their second or third units because initial units and even replacements arrived with scratched mirrors due to the mirror cover coming loose during shipping and marring the primary. Supposedly this problem has finally been remedied with improved packing.

(2) The design of the aluminum altitude trunions didn't look like it would allow use of Digital Setting Circles easily. My suburban skies are about magnitude 4 at the Zenith, so I'm often forced to supplement my star hopping with some electronic assistance. That wouldn't be possible at least any time soon with the Lightbridge. Maybe someone will develop a commercial kit for adding an encoder and gear to the altitude trunion, but out of the box, you're star hopping only.

(3) For basically the same price, I was able to buy an Orion XT12 Intelliscope with the DSCs, and Pyrex mirror (The Lightbridge is BK-7), so for my requirements and observing conditions, the Orion fit a bit better.

Still, I think the LIghtbridge is an extremely good value for the right user (i.e., somone who needed easier portability). The XT series and GSO solid tube brethren in the 12" range are harder to transport in a compact car, though mine will fit in my Civic sedan.

Egads Floyd. I think it's contagious. I don't have a camera or my collection handy, but I do have an up-to-date list. Is there a cure? A 12-step program or something?

50mm Parks Plossl; 2”
40mm University Optics Konig MK-70; 2”
35mm Celestron Ultima
34mm Siebert Observatory Series; 2”
32mm Meade Research Grade Wide Angle; 2”
32mm Televue Plossl
28mm Meade Research Grade Orthoscopic
27mm Televue Panoptic; 2”
26mm Celestron (Vixen) Plossl
25mm University Optics Othoscopic
25mm Takahashi MC Orthoscopic; 0.965"
24.5mm Meade Series 4000 Super Wide Angle
24mm Televue Wide Field
24mm-8mm Vixen LV Zoom
21mm Pentax XL
20mm Meade Research Grade Wide Angle
20mm Meade Research Grade Wide Angle
18mm University Optics Orthoscopic
18mm Takahashi MC Orthoscopic; 0.965"
17mm Orion (Vixen) Lanthanum Superwide; 2”/1.25”
16.8mm Meade Research Grade Orthoscopic
16mm University Optics Super Erfle
16mm University Optics Konig II
15.5mm Meade Research Grade Wide Angle
15mm Celestron Ultima Wide Angle
14mm Meade Series 4000 Ultra Wide Angle; 2”/1.25”
12.5mm University Optics Orthoscopic
12.5mm Takahashi MC Orthoscopic; 0.965"
12.5mm Celestron Ultima
12.4mm Meade Research Grade Wide Angle
11mm Televue Plossl
10.5mm Meade Research Grade Orthoscopic
10mm Televue Radian
10mm Zeiss “aus Jena” Abbe Orthoscopic; 0.965”/1.25”
9mm Orion Ultrascan
9mm University Optics Orthoscopic
8mm Edmund RKE
8mm Orion (Vixen) Lanthanum Superwide; 2”/1.25”
7.5mm Orion (Vixen) Lanthanum
7.5mm Celestron Ultima
7mm Meade Research Grade Orthoscopic
7mm Meade Research Grade Orthoscopic
7mm Meade Research Grade Wide Angle
7mm University Optics Orthoscopic
7mm Televue Nagler Type 6
7mm Takahashi MC Orthoscopic; 0.965"
6mm University Optics Plossl
6mm University Optics Orthoscopic
5.2mm Orion (Vixen) Lanthanum
5mm University Optics Orthoscopic
5mm Celestron Ultima
4mm University Optics Orthoscopic
4mm Meade Research Grade Orthoscopic

Two answers, depending on price.

At $60, you can't beat University Orthoscopics. Flat fields, good contrast, better edge correction and eye relief than any of the Plossl-derivatives (Ultrascopics, Parks Gold Series, Ultima, Meade Series 4000, etc.). The only drawbacks are a slightly smaller AFOV at 45 degrees than the Plossl-types that range from 50 to 52 degrees, and moderate internal reflections on very bright objects at certain focal lengths.

At $80-100 I'd choose the Televue Plossls. I have or have owned Televue Plossls, Celestron Ultimas, Orion Ultrascopics and Parks Gold Series in various foca lengths, and to my eye the Televue Plossls are sharper, have better edge correction, offer better throughput and contrast, and are better built than the others. The only drawback is the fact that the Televues have a slightly smaller AFOV, but given the better edge correction than the others, I do't find the extra 2 degrees of soft AFOV valuable.

My absolute favorite mid range eyepiece is the 32mm Televue Plossl. Side-by-side with the 35mm Celestron Ultima, the Televue doesn't have the Ultima's bad habits of blackouts, field curvature, and soft edges. As focal lengths get shorter, I think the differences between the Televue Plossls and the others get less pronounced, but if I was going to own only one line, it would be the Televues.

Floyd Blue said:

I am interested in your impressions for the 34-36mm Siebert Observatory EPs.

Hi Floyd.

I have a 34mm Siebert Observatory Series that I use with a 12" f/4.9 dobsonian. It gives me just about the largest useful exit pupil for my tired eyes, and the 70 AFOV and long focal length make for a very large TFOV to boot.

On the A-F scale, I would give it a strong B+. I base this rating on the following factors:

The Good:

The FOV is flat. Nice and flat. Flatter and sharper at the edge than say a 27mm Panoptic.

Nice wide FOV.

Stars stay pinpoint to the field stop which is a generous 38mm.

The Not So Good:

Contrast isn't on par with the Panoptics by a long shot. I blame the coatings, which are fairly reflective. For example when you view a very bright object like Sirius, the reflection of the object off of your eyeball will re-reflect off of the surface of the eyelens and make it look like a tiny "companion star" dancing all around the object.

Price. At $200, it is not inexpensive. At $150 I would have given it an A-. At $200, for just a bit more money you can get some excellent second tier premiums like the Vixen LVWs.

Jim

Hi Jim.

FWIW, the 8mm Vixen (Orion) LVW (Superwide) is my favorite high power eyepiece on my 12" f/4.9 Dobsonian.

It has a nice, wide, flat field with good contrast and superior resolution edge to edge. Mine is the Orion model and on any given night it actually provides very slightly better contrast and resolution than my 10mm Radian on objects such as the E and F stars in the Trapezium.

The 8mm in particular is one of the best modles from the LVW (Superwide) line.

- Jim