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Posts Made By: Stuart St. Clair

June 27, 2002 10:03 AM Forum: Telescope Making

Whiffle-Tree Mirror Cells

Posted By Stuart St. Clair

I have heard of the whiffle-tree mirror cell design as an improved alternative to a sling system. Does anyone know of any web sites that show this design? Does anyone have any thoughts on which design is better, or whether there are other better designs? This is for a 12.5" f/5 mirror.

August 9, 2002 12:17 PM Forum: Deep Sky Observing

Observing Site Near Cottonwood, Arizona?

Posted By Stuart St. Clair

I am planning a trip to Arizona next spring, probably in April. By then, I should have my 12.5" dob finished. I saw a website for Dead Horse Ranch state park near Cottonwood, Arizona. They have camping with showers, which is important for my wife. I don't know Arizona very well, even though I was born there. Is that a good area for observing the night skies? Will it be cold there in April? Does anyone have any other campground suggestions in Arizona? We will probably be there a week or more, so we want something with plenty to do in the daytime also, like hiking, exploring interesting towns, etc. Thanks for your help.

October 4, 2002 07:35 AM Forum: Telescope Making

UO Spiders

Posted By Stuart St. Clair

Can anyone tell me how good are the UO Spiders. Are they easy to adjust for collimation? Do they hold collimation well? Do they have any vibration problems? They are much lower in price than some of the other manufacturers, but you usually get what you pay for. Thanks.

October 9, 2002 12:56 PM Forum: Eyepieces

Siebert 2" Ultra Plus 27.5mm

Posted By Stuart St. Clair

Has anyone tried this eyepiece? Do you have any comments on performance? I am thinking of buying it for a 12.5" f/5 dob that I am building, as well as for my 8" f/6 dob. Thanks.

October 22, 2002 10:16 AM Forum: Eyepieces

Siebert Ultra EPs vs. Radian or Pentax

Posted By Stuart St. Clair

Has anyone done a comparo between the Siebert Ultra EPs and something like a Radian or Pentax XL? Specifically, I am thinking of buying the 13mm 1.25" Siebert Ultra, and I am wondering how it compares against a 14mm Radian or Pentax. The reason I would prefer the Ultras, other than price, if they provide comparable performance, is that they are lighter, which will be an issue with the 12.5" f/5 dob I am building (the lightweight design tends toward top-heaviness). Harry Siebert told me by e-mail that his EP would outperform the Radian or Pentax, but I am wondering if any of you can give me your opinion based on actual use. Thanks.

October 22, 2002 12:30 PM Forum: Equipment Talk

Collimation with Star Test

Posted By Stuart St. Clair

Can someone point me to a good description of collimating with a star test, either on the web or in a book? I've got the collimation with a Cheshire eyepiece/sight tube down, but I need to take the next step. Thanks.

October 23, 2002 06:38 AM Forum: Equipment Talk

Siebert Ultra EPs vs. Radian or Pentax

Posted By Stuart St. Clair

I posted this on the eyepieces forum but didn't get much response, so I will try here. Has anyone done a comparo between the Siebert Ultra EPs and something like a Radian or Pentax XL? Specifically, I am thinking of buying the 13mm 1.25" Siebert Ultra, and I am wondering how it compares against a 14mm Radian or Pentax. The reason I would prefer the Ultras, other than price, if they provide comparable performance, is that they are lighter, which will be an issue with the 12.5" f/5 dob I am building (the lightweight design tends toward top-heaviness). Harry Siebert told me by e-mail that his EP would outperform the Radian or Pentax, but I am wondering if any of you can independently verify or refute this claim based on actual use. Thanks.

October 28, 2002 07:21 AM Forum: Telescope Making

Sizing Secondary Mirror

Posted By Stuart St. Clair

I am using the Newtonian Telescope Design Planner available on the web to design my 12.5" f/5 lightweight dob. For sizing the secondary mirror, you have to select the desired minimum 100% field illumination, either measured as a diameter in millimeters or as an angle in arcminutes. They suggest a minimum 6 millimeter or 13 arcmin 100% field illumination. My question is: what value should I use? Of course, I will have a 2" focuser and low power widefield eyepieces. Any help will be appreciated.

October 31, 2002 10:41 AM Forum: Telescope Making

Optical Expert Needed in Fresno, California Area

Posted By Stuart St. Clair

I am looling for a mirror maker or other optical expert in the Fresno, California area to evaluate a 12.5" f/4.8 primary and secondary that are being shipped to me for evaluation before purchase. My telescope structure will not be finished for a few months, so I don't have a telescope to mount the optics in for testing.

November 4, 2002 02:53 PM Forum: Telescope Making

Kydex Alternative Wanted

Posted By Stuart St. Clair

I am making a light baffle to place across from the focuser on the secondary ring (it's not a cage, just a single ring). Kriege and Berry suggest using Kydex. Does anyone have a suggestion for an alternative material that will work as well and maybe be easier to find? Thanks.