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Posts Made By: Todd Gray

March 14, 2004 09:02 AM Forum: Eyepieces

11 mm and 50mm Eyepieces

Posted By Todd Gray

I have an 8" f/6 1200mm focal length DOB. I have gottn hooked on 2" eyepieces, especially for viewing DSO's.
I am in the market for a 11mm eyepiece and a 50mm eyepiece with excellent FOV. With so many eyepiece selections out there my brain is about to explode(Did anyone see that movie Scanners?)Pound for pound I am looking for the best eyepieces out there, but there's a catch, I don't have the cash to go after the nice expensive eyepieces.
Can anyone help on deciding which eyepiece, and why, is best for my scope?
Thanks
On a budget
Todd

March 23, 2004 12:03 PM Forum: Equipment Talk

2x and 3x Barlow

Posted By Todd Gray

What kind of visual difference could one expect to see using the same eyepiece in a 2x 2" Barlow as in a 3x 2" Barlow? Would the visual difference depend on the eyepieces magnification? I tested 9mm, 16.8mm, 25mm, 30mm, and 42mm eyepieces quickly swapping them out with the 2x and the 3x Barlows. I could not differentiate between the two. I first looked at the orion nebeula, then Jupiter, and then on a street light with all 5 eyepieces. Did I just get a 3x barlow that is really only 2x or is the difference that negligable, and if so then why would one want varying magnifications in barlows? By the way my scope is 8" f/6 1200mm if that matters. I am realy confused.
Please Help,
Todd

March 28, 2004 01:46 PM Forum: Telescope Making

mirror making

Posted By Todd Gray

Hello,
I am currently considering grinding my own mirrors.
I would like to grind a 8" f/8 mirror first. Then if all goes well step up to a 12.5" f/6 or f/5. My question is plate glass vs pyrex, as well as how thick. The plate glass is cheaper and I have heard retains less heat than the pyrex (the thinner the glass on both types the better). Is it feesible for a novice to turn 3/4" or 1" plate blank into a mirror with wavefont 1/20 or better. I know the pyrex is sturdier and would not have to be climate controlled in the final stages like the plate glass, but from a pure optical stand point which is better???
I have also found a nice web site mirrorkits.com. Has anyone ever dealt with these people and are their mirrors or blanks up to par? I have also heard of quartz blanks and fused silica, what's the story with those? I am looking to create the best quality mirror possible. Any other suggestions or comments that will aid me in doing so is strongly encouraged.
Thanks
Todd

April 7, 2004 06:06 PM Forum: Telescope Making

12.5" mirror

Posted By Todd Gray

I am currently purchasing a 12.5" mirror that I will use to make a DOB. The manufacturer is charging me an extra $100.00 to have it made out of pyrex instead of plate glass. This will also cause the wavefront to go from 1/10 with plate to 1/15 with pyrex. My question is it worth the $100 to go with the pyrex or could I save some money with little or no optical sacrifice using more points on mirror cell? How much of the optics will actually be sacrificed?
Thanks
Todd

April 19, 2004 10:32 AM Forum: Eyepieces

9mm nagler vs 10mm speers-waler

Posted By Todd Gray

I am in the market for a wide FOV in the 9-11mm focal range. I would like to get the best EP but only spending $150. The new speers-waler 8 element 82' FOV is inticing for $129 but how would it stack up to a used 9mm nagler type1? Should I bite the bullet and purchase a type 6 for another $100+? Could I even find a type 6 used at this point?If so how does the speers-waler stack up to the type6?
Your thoughts
Thanks
Todd

April 20, 2004 06:23 AM Forum: Telescope Making

12.5" Mirror

Posted By Todd Gray

I have recently purchased a 12.5" f/6.7 mirror through Obsidian Optics. I got a great deal for pyrex wavefront 1/15 or better, which I guess is making me a little nervous. Has anyone out there ever dealt with this company or its' owner Mark Cowen? Just need a little reassurance as this was a big purchase for me.
Thanks
Todd

April 26, 2004 07:24 AM Forum: Eyepieces

4.8mm nagler vs 4mm radian

Posted By Todd Gray

I am currently in the market for 4mm EP. I have the opprotunity to spend around $100 for the nagler and $160 for the radian. Although the EP will be used primarily for planets I still would like the option of 82'FOV. Especially since my scope does not have tracking. I do not want to sacrifice clarity of view however and do not have the funds for a type 6. I hear something about ghosting in the 4.8mm nagler, a concern. On the otherhand I hear the only real difference between the two is FOV and 1 less element in the radians for a slightly brighter image. If most of the planets I will view are plenty bright enough and clarity is the main concern why would this matter? Please help me decide between the 2 EPs.
Thanks
Todd

May 15, 2004 07:38 PM Forum: Eyepieces

40mm-42mm EP

Posted By Todd Gray

Has anyone had the opportunity to compare and contrast the following eyepieces:
42mm Vixen LVW
40mm Pentax XL
40mm Meade SWA
40mm Celestron Axiom
Looking to purchase an EP in this focal range and want to know which one of these is the best?
Thanks,
Todd

August 5, 2004 07:41 PM Forum: Telescope Making

12.5" Dobsonian truss design

Posted By Todd Gray

I am trying to fabricate a 12.5" Dob out of alluminum. The poles I am using to make the truss are 3/4" and really thick walled, aquired from a friend who use to work for the phone company for free. I have seen several designs incorporating 6-8 poles at .055 wall thickness to creat a truss. Since my poles are probably 10x thicker I am worried about wieght and also contemplating a more radical design, but I still want my scope to be plenty stable(keeping in mind thermal expansion, euler buckling, sagging, air currents, etc...)
Does anyone out there know of a great website that shows different examples of truss designs?
The design c :S an be a simple diagram or GIF, I can always work out the kinks myself.
Any aid given will be greatly appreciated
Todd Gray

November 30, 2004 07:20 AM Forum: Telescope Making

secondary mirror size

Posted By Todd Gray

I am building a 12.5" f/4.7 scope that will be used for both ccd and visual. I am trying to decide on whether to get a premium 2.6" secondary or a not so nice 2.76"/2.9". We are talking about a difference of 1/20th pv wave for 2.6" and 1/10th pv wave for the others(maybe 1/15th). How much difference will there really be? Should I sacrifice size for quality?
Need help coming to a decision.
Thanks,
Todd Gray :S