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Posts Made By: Larry Stedman

December 20, 2004 06:51 AM Forum: Eyepieces

Eyepiece selection: Spacing, rules of thumb?

Posted By Larry Stedman

I've read different "rules" for selecting a set of eyepieces--e.g.,

1) low, medium, and high power

2) exit pupils of 4mm, 2mm, and 1 mm (e.p. = eyepiece f.l./ scope f.l.)

3) spacing them (& a barlow) so that each has a magnification of 1.4-1.5x the next one.

What do you recommend, and what is the spacing of your most used eyepieces?

If someone were buying a set of 3 eyepieces and a barlow, what would you recommend as to their spacing?


February 27, 2005 06:40 AM Forum: Eyepieces

Televue eyepieces corrected to f/4??

Posted By Larry Stedman

While Televues are certainly better than many (most) eyepieces, that doesn't meant they produce "sharp to the edge" and "pinpoint" images across the entire fov in *fast* scopes. For example, while a 22mm Panoptic is markedly better than an old Celestron 20mm Erfle in a dob at f/5.4, there is still noticeable coma and field curvature in much of the outer portions. sad

I think it is important to stress this because otherwise less experienced observers may rush out to buy expensive $$ high-end eyepieces thinking they will work miracles. A lot depends upon the observer's standards, their sensitivity to distortions, how fast their scopes are, their eyesight, the eyepiece's field of view, and collimation.

I found that a 21mm Pentax did just as well as the Pantopic, cost a bit less, & had better eye relief for eyeglass wearers. 8O

And, if one is willing to sacrifice the wider field of view, but still have more than a Plossl, the 22mm Epic is quite good for little money. (Admittedly, though, many find the Epic's 20mm eye relief too much.)

April 20, 2005 05:25 PM Forum: Equipment Talk

Dob to truss conversion-- who to contact?

Posted By Larry Stedman

Have a superb Discovery 10" f/4.5 scope. Great images, fast cool down, yada, yada, yada... but it's a monster, big and H-E-A-V-Y, and fills up too much of the car. I'm looking for someone to convert it to a truss (well, considering, ruminating about having someone do it...)

Alas, Rob Teeter is temporarily out of the biz, attending to senior year of college and then grad school (what's that, a life of his own? I thought he was ours).

Anyone else you can recommend?

Also, what do you think about the following weight goal?

I'd like it converted such that the heaviest component would be no more than [COLOR="Red"]15 pounds[/COLOR]. I think it's doable given that Tom Noe packages a 10" f/5 Teleport in a 30 pound total package. I'd be hoping to end up with, say, a 15 pound rocker, a 15 pound mirror box, and a10 pound secondary cage. Doable or not? What sayest thou?

April 23, 2005 11:28 AM Forum: Coronado-Lunt-DayStar Solar Filters

PST and Nexstar 80GT? Camera tripod?

Posted By Larry Stedman

I see where Don has used a replacement slider bracket to mate the PST to an 80GT mount.

Is there anyway of mounting the PST to the 80GT mount directly without that? I.e., some padded circle or grip ring that would fit within 80GT's own?

Alternatively, does the PST mount directly to a camera/video tripod? How stable or awkward is that compared to using the 80mm on a tripod?

Are there 40mm tube rings available to attach the PST to such a tripod? Which would allow for balancing?

Are those old add-on slo-mo controls for tripods useful in such an arrangment? I have a set I thinking of selling, but maybe I should keep it for use with a PST...

Appreciate any light that can be shed (pardon the pun!)

May 14, 2005 07:10 AM Forum: Coronado-Lunt-DayStar Solar Filters

PST First-light: 10 reactions, tips for beginners (LONG)

Posted By Larry Stedman

I truly enjoyed my first two sessions, each lasting a full half hour or more... I was able to easily see several prominences develop and one brighten; another move farther away and change shape and fragment. It was fascinating.

I found the following:

1) I had read about the PST's sweet spot" and became worried that would mean only a narrow, tiny area at the center of the fov would give crisp views... and that one could not really expect to see an entire disk and prominences. Well, I rapidly discarded those concerns! One can center the entire disk in the fov and still see prominences crisply.

2) It is really important to fine-tune both the focusing and the tuning to get the best views. While tuning can alternately enhance prominences and surface detail (including dark filaments), one can also set things to show both simultaneously.

3) A dark hood (black tee-shirt), draped over the head and eyepiece end of the scope, helps immensely. It can be the difference between a glary, diffuse view, and a crisp, dramatic one.

4) Low eye-relief eyepieces help as they make you put eyeball close and hence block extraneous daylight. High eye-relief eyepieces (which I normally use without problem) can produce kidney beaning or blackouts perhaps because one's pupil is smaller during the day.

5) Although I was initially dismayed by its limited eye relief, the supplied 12mm Kellner works well, and combines well with a low-end 2x barlow for higher power views.

6) Other eyepieces that gave crisp views were RKEs alone and barlowed. (A 12mm orthoscopic worked well, too.) My favorite 8-24mm zoom, barlowed, covered mags well and allowed easy mag changing... but the eye relief & blackouts were often too much.

7) Be prepared for a huge amount of turning of the focus knob when adding a barlow. Know, in advance, whether the barlow requires in or out focus. Generally, I found it easiest to leave a barlow in all the time. (Parfocal eyepieces make good sense with the PST.)

8) I found that a slo-mo control add-on to a camera tripod was really helpful for repositioning the Sun.

9) As with other astro observing, one gains skill over time (even within an hour!), knowing where to look, how to focus and tune.

10) Beware of one other thing... it's addicting.

Alas, it's cloudy today!

June 11, 2005 06:02 AM Forum: Eyepieces

Orion Stratus eyepiece review! What's the catch?

Posted By Larry Stedman

A short but sweet non-technical review of the Stratus line has appeared here. Apparently, they produce crisp views even at f/5.

The only drawback mentioned was that the 2" barrel portion is short, so be careful with it. Otherwise, the review glowed with praise.

So... what's the catch?

I don't know, but I'd like to see a follow up with an f/4.5 of f/5 dob... and some comparisons with Radians and orthos on planets or Pentaxes and Panoptics on DSOs...

If they are as good as stated, then Televue will finally have some real competition. And their prices may have to be reduced!

July 23, 2005 05:39 PM Forum: Equipment Talk

Perils of Trying a Radian...Or How to Add a Set Screw to an Astroscan?

Posted By Larry Stedman

Made the mistake of trying a Radian in my Astroscan. Loved the views.

Now I must figure out a way to add a set screw to the focuser tube so that if the 'Scan were to droop or rotate unexpectedly, it doesn't dump the TV. (For those unfamiliar with the 'Scan, the focuser tube, which is metal, has no screw to lock an eyepiece in place.)

Even better would be a replacement tube with set screws (so that my lack of handiwork skills doesn't destroy the original tube). Tried to swap it with an extender tube that had set screws, but that's designed to fit inside a 1.25" tube not replace one.

Any ideas? Suggestions? Anyone done anything like this?

August 12, 2005 05:22 AM Forum: Eyepieces

Burgess/Back planetary eyepieces??

Posted By Larry Stedman

Stumbled upon the part of the Burgess Optical web site where the new 60 degree, 20mm eye relief, Pentax-like eyecup, planetary eyepieces were described. Only $99.

Designed by Thomas Back with a link to a yahoo group posting by him about the design. They sound incredible.

Are these out yet? Any judgments? How do they compare to the Radians, the most similar eyepiece out there vis-a-vis the specs? How are they on DSOs?

August 12, 2005 10:38 AM Forum: Eyepieces

2" 26mm Burgess SWA-- what is the fov?

Posted By Larry Stedman

The Burgess Super Wide Angle 26mm 2" lists a fov of 72 degrees.

Wondering if anyone has measured the actual fov...

I'm asking because I've found that the fovs for some other 2" eyepieces are less than specified. For example, the 32mm Burgess is listed as 72 degrees, yet measured 65. The 30mm 1rpd listed as 80 degrees, measured 70. The 26mm GSO/GTO is stated as having 70 degrees, measured 58. These are approximate, based on star field widths. (For comparison, using the same technique, a 21mm Pentax had exactly the 65 degree fov it is supposed to.)

I'd like a 2" eyepiece in that focal range with good fov, 20mm eye relief for glasses, and for not a lot of greenbacks. (E.r. rules out 24mm Pan; $$ rules out 27mm Pan.)

August 13, 2005 03:19 PM Forum: Equipment Talk

Radian camera adapters with other eyepieces?

Posted By Larry Stedman

Interested in comments about the Radian camera adapter... can anyone compare it to the scopetronix digi-t system?

Also, are there other lines of eyepieces that it works with? For example, Ultimas or Epics? That is, eyepieces for which the dig-t system doesn't work.