Posts Made By: Rod Kaufman

David,
Iam sorry to learn your widefield eyepieces from Adorama aren't working well for you. They are the same as the Orion expanse eyepieces but are sold under the pro-optic label. I have the 6mm version and it works quite well in my 16" Astrosytems truss dob. Other amateurs have rated it highly in excelsis.com where eyepieces and other equipment is evaluated.
The pentax eyepieces,although pricey,are virtually free from distortion and a 14mm unit should work well in your dob unless the optics are not collimated or some other problem exists in your scope. Less expensive eyepieces such as the widefield Russel 19mm may work well but the edges will be soft.(I just purchased and tried a 1.25 version of the Russel 19mm eyepiece in my scope and it works well for a erfle design). The celestron axiom eyepieces in 15mm or 19mm are relatively inexpensive but have good contrast and high light transmission but the edges will exhibit astigmatism in your scope.

David,
I think it would be preferable for you to link up with a local amateur group in your home town of Houston. This would save you the hassle of shipping the eyepieces and you could probably pop them in and out of a fast dob during a star party and see if the eyepieces are at fault. In addition, you could probably borrow a premium eyepiece from someone at a star party and try it your scope and then compare it with your own eyepieces. It sounds like your scope is collimated although I would recommend a laser in addition to a chesire eyepiece. Finally, use a good 7mm eyepiece and look at the in and out of focus images of polaris(since it hardly moves)and see if the diffraction patterns look similiar. If so, your optics are probably collimated and performing well. Give it a try.

James,
I agree with Jeff. It seems like you have astigmatism from an overly tightened mirror clip. I am not sure of the means by which your mirror is held in the cell but make sure the clips or retainers or screws do not impinge upon the mirror. Lining the mirror clips with cork sheeting will prevent the problem of the mirror shifting around if you are concerned about excessive play between the mirror and it's retainer.

I have some comments regarding the application of various eyepieces relative to performance issues on the planets.
Over many nights of observations on Jupiter and Saturn with a Discovery 12.5" dob and an 16" Astrosystems dob, I attempted to discern subtle differences in performance among the eyepieces in my collection.
I have general comments that may be of benefit to some amateurs, First, I am convinced that a battery of eyepieces are necessary to obtain the maximum amount of detail, color variation,and resolution. However,cost effectiveness is an important issue as expensive eyepieces do not necessarily equate to the best performing eyepieces. After re-reading the cloudy nights review on planetary eyepieces and reflecting back on my recent experiences, I have recognised that some relatively inexpensive eyepieces can outperform more expensive units on specific details on the planets. For example, I found that my seibert 7mm eyepiece gave the best overall resolution on the rings of Saturn as compared to my pentax XL, UO ortho and ultima eyepieces. The difference was not subtle but rather obvious. I found that a 7mm pro-optic eyepiece gave the best color rendition on the globe of Saturn with the Pentax unit close but not as good. The overall contrast between the rings of Saturn and the globe was best in the pentax and UO orthos, giving that nice optical snap every amateur loves to see. The ultimas were also very favorable in this regard.On Jupiter, the differences were apparent but more subtle. I found the pentax eyepiece and the UO orthos to give highly resolved details of the belts, bands and festoons. Color variation was more difficult to discern but the pro-optic widefield 7mm unit and the pentax XL were quite close with perhaps the pentax revealing the best color fidelity. The ultimas were also good in this regard,and also quite good in resolution but not quite as good in revealing subtle color variations.
I would like to read comments from other amateurs who have applied a variety of eyepieces in the observation of the aforementioned planets over many hours with similar instruments. Perhaps some kind of a consensus of opinion or at least a trend of recommenmded use of eyepieces for various surface details may start to be realized. Up to now, it's been pretty much, "this eyepiece is better than another". It just doesn't work that way, in my opinion.

Jay,
I have a JMI mini-max on one of my dobs. The most frequent causes of "encoder error" in my experience are: 1.Low battery--a 9 volt lasts about three full observing nights of about 8 hours per night or less and it's "encoder error" on the scroll line. 2. Faulty cable--most likely at the encoder pin connections. Try a new cable with a new connector. 3. Make sure your unit is set to the proper mount and not on dob or alt/azimuth setting. 4. There may be a bad encoder. I would check the battery, pin connectors and encoder settings on the max and then call JMI and ask to speak to the tech. She walked me through a procedure over the phone and we identified a bad pin connector as a cause of encoder error when I encountered the problem a few years ago. My unit has worked fine after installing a new cable. I hope this helps.

I have found my Discovery 12.5" mirror cell doesn't hold collimation because the springs in the mirror cell allow a small but significant amount of movement as evidenced by migration of the laser dot from the center of the doughnut to the top of the doughnut on the primary as the scope is moved from the horizontal to vertical planes. I believe virtually all such cell designs will produce this de-collimation effect when used with full-thickness mirrors. The "fix" is borrowed from an old Telescopics mirror cell-design which incorporated three locking screws with nuts that pass through the rear supporting plate to the plate that supports the mirror and are screwed-down after the wing nuts are adjusted for collimation. I drilled four holes through the back-supporting bars of the Discovery cell and passed the screws to the back of the plate that supports the mirror and tightened them after collimation. This effectively stopped the de-collimation. I believe the de-collimation problem is un-recognized by other amateurs and is probably a universal problem. I also think this explains why Ed Ting could not resolve Delta Cygni with a test 12'5" Discovery scope in the Novenber Sky and Tel review; his scope was de-collimating as he moved it but he didn't know it.

Floyd,
I know how you feel--I have two weeks off from clinic duties at this time and I had hoped to do more observing. Nevertheless, happy holidays to you, your wife, Randy and all of the other guys in the Bakersfield group and all of the other amateurs.

Most used eyepiece in my collection: Pentax 10.5mm XL.

Guy,
It doesn't surprise me. Some people are ignorant and don't bother to read their instruction manuals. I bought a celestron 4.5" goto from Costco for my daughter and looked at the celestron website and noted much of it was devoted to identifying which end was the eyepiece end!
When I had my 16" truss dob at Mt Pinos, Ca last January, some people identified it as a snow-making machine!

Floyd,
Nice job on the DSC installation on your 12.5" dob. Another fine example of your work.