Posts Made By: William Rose

Hi Nicolas,
Just some thoughts: I believe Bill Vorce (scopehead) sells several Meade .965" EPs in his "store" on EBay very inexpensively.
The TAK .965" EPs are superb, especially for the price. I'm fortunate enough to own several CZ O- Othros. In anything but the best optics you can't tell the difference between the CZ & TAK .965" EPs. If you run across them, the Zeiss AUS Jena .965" EPs are an excellent buy for the quality. I picked up 2 recently for about $65.00 each.
If you're emotionally tied to the Circle T EPs they do show up on A'Mart and I've seen a couple on EBay recently. For the price they're good glass.
Hope you find something that works well for you.
Clear Skies, Bill

Hi Dave,
I don't believe you can do that using RA & Dec.
I'm assuming you know what the stars are if you have the co-ordinates. Do you have the list of stars Sky Tour has for alignment? (came with the Sky Tour) I would think you could find a couple from this list within view to enter.
I think I'm missing something here but not sure what. I've found the list of alignment stars supplied with my Sky Tours is braods enough I can always find a couple stars to use for alignment.
Clear Skies, Bill

Thanks to Adam for the Precision Parts thought, they have offered to make adapters.
I also have a lead on adapters from Clavé. A bit pricey but if anyone needs an adapter, send me an email and I'll pass on what information I have.
Clear Skies, Bill

Sorry I've been out of town for the Memorial Day weekend.
I wasn't sure if it's legal to post another dealers website or not so I omitted it from the original post. If this isn't legit here my apologies. Here's the page I found through a Google search: http://www.tar-palantir.com/po.htm
I did receive an email from Stew Squires indicating he had not updated the pag in awhile and the Pentax SMC ED eyepieces are no longer available except used.
I'm still a bit confused if these are different from the Pentax SMC Ortho's but from the kind response posted here it sounds like they're one in the same. If I find out differently I'll let you know.
Clear Skies, Bill

Hi Allen,
Re: I'd appreciate your suggestions for a wide-field scope that would complement (and maybe piggyback on) a C9.25, primarily for visual work. I'm thinking about a Televue NP101, with a reasonable aperture and wide FOV, but I'm open to suggestions.

I have a C9.25 on a CG-5 (Dual Drive) mount with Vixen Wooden legs. I also use a TV Genesis on it occasionaly. Both work fine for visual but it's a bit nore than the mount can handle for Astrophoto work.
The NP101 is a Great scope. I bought an NP-127 which I love. Only thing I'd probably replace it with is an A-P 130 StarFire. Hope that helps.
Clear Skies, Bill

Hi David et al,
Sorry to come in late on this thread. There have been a couple discussions recently on this topic. One of the better ones was on [email protected] in late May/early June.
Chris is correct that the 1.5 to 2mm value comes from the Maksutov publishings in the 1920's through 1940's.
Maksutov published his findings based on his own visual observation and testing. Hopefully his eyes were good! Average? Who Knows.
Note this value is based on the Central Vision vs Averted Vision Rods & Cones of the eye.
From the posts on the ZOC group:
"For Maksutov's eye...best resolution comes at around 1.5mm pupil size...a bit over 2 arcminutes. At 5mm pupil size it's down to almost 4 arcminutes. (From personal experience of various eye exams where my pupils have been dilated or constricted...big pupils, 7 - 9mm, give horrible images, but 1.5 - 2mm is awful sharp.)"
"Maksutov goes on to show how the data from this table can help one actually determine what magnification/exit pupil/scope aperture is really needed to resolve a given angle. (Note: Maksutov did these test's on an optimum brightness artificial double star. If he made the double star brighter or fainter...his resolution ability dropped.)"
Continued in part 2

Continuation - Part 2
"Maksutov also made studies of angular resolution of faint objects, i.e. transitioning from central/foveal vision to averted/rod cell vision. Keeping pupil size constant at 5mm, he lowered brightness of his test target. The best resolution, as stated above, was a bit less than 4 arcmin. At the lowest detectable light levels (threshold of detection)...resolution was down to 2 degrees, repeat, 2 degrees."
"I have briefly summarized a small bit of what Maksutov took pages to carefully, thoroughly cover. This is a complex subject. (And I have not addressed contrast sensitivity at various light levels or size/spacing of test targets.) Maksutov ends his section with this appeal:
"It’s especially important to know how to apply the theory discussed above when designing new optical instruments: consumer, military, geodetic, etc., so that they are equipped with the best eyepieces for their given observing tasks. But we are powerless to give any strict guidelines until there appears statistically reliable material on the resolving power, aberrations, and inhomogeneities of the average observer’s eye. Therefore I must repeat my appeal from 19 years ago to astronomers, who are most able to undertake such studies: “test your eyes’ performance and report to the author your objective and thorough findings!”"
There's a WHOLE bunch more in the thread, excellent reading. My Thanks to the Carl Z. Group!

For whatever reason ZOC used FedEx to ship my mirror to me. (Just arrived yesterday).

Floyd Blue said:

I intend to ship my Zambuto mirror and other parts to Florida. I just checked today on charges and insurance as well as time in transport issues with all three of these. USPS wins hands down in all categories as well as have no limits on proper packaged fragile items. The costs is about 1/3-1/2 by shipping USPS Priority vs, UPS and Fedex ground plus much faster transport. Insurance charges with Cerified mail ammount to $19 on $1600 worth of insurance. Weight of 20# total price of $55.80 for the package with insurance and cetified protection. You can send it overnight for the same amount that UPS or Fedex wants for ground.

Hi Chet,
As Dan has indicated the main problems with a longer Focal Length EP I won't repeat his observations. I can tell you that a 45mm Silver Top, 1 1/4" and a 40mm SW Konig, 1 1/4" suffer the same malady in a MCT of this aperture. The first decent Focal Length that doesn’t give you Tunnel Vision and have a gray spot with the 90mm MCT I tried was a 35mm Clave 1 ¼” (which has a narrow FOV) and a 32mm UO Konig 1 ¼”.
A 36mm ‘Super Wide Plossl’ I tried showed very minor signs of a dark center although teh "Tunneling" wasn't objectionable.
My guess it that you could get away with a 40mm Ortho with minor issues but a 40mm Plossl might cause problems.
I’d go for the Spotting Scope or a small refractor. I just picked up a Meade 277, 80mm Refractor (Object by Vixen in those days) with Table tripod, diagonal, case, etc. for about $85.00 shipped. With a TeleVue 1 ¼” diagonal and TV eyepieces it’ll match any achromatic out there and is Much better than my $300+ Leopold shooting scope.
Cheers, Bill

Hi Nils,

I believe the complaint about vignetting comes from the use of the Big Barlow with Panoptic eyepieces. With some of the Panoptics (35mm & 27mm. 22mm I think also) it does slightly vignette. That's why TV makes the 'TeleVue Panoptic Barlow Interface'. Personally I don't have a problem with eye relief since I don't wear glasses. Can't say as I've ever tried comparing the Big Barlow and Powermate as far as eye relief.
I haven't noticed any vignetting with the Powermate and Naglers but then I can't remember that there's any vignetting with the Panoptic and the Powermate.
The TeleVue Panoptic Barlow Interface definately helps with the 35mm & 41mm Panoptic but then addition of a 17mm and 22mm eyepiece eliminate the need for either.

Clear Skies, Bill

Nils Schoultz said:

Thanks for the advice, Bill. It sounds as if you think the powermate would give a better image than a 2" barlow. I've never been clear whether or how a powermate is better than a barlow - if (big if) the barlow does not cause vignetting in an eyepiece, I don't understand why a 4-element powermate would give better star images than a 2-element barlow. But your real experience counts for more than speculation, so I think I will go with the powermate unless someone else convinces me otherwise.
thanks again,
Nils