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Lawrence Parchman

Sculptor Galaxy (NGC 253)

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Posts Made By: Jarad Schiffer

July 21, 2004 07:20 PM Forum: Equipment Talk

What to sell, What to Keep?

Posted By Jarad Schiffer
I agree with Floyd, except that you should sell the FS102 to me.... grin

Jarad

August 4, 2004 01:33 PM Forum: Equipment Talk

6.5 inch APO ???

Posted By Jarad Schiffer
The description of "works like an APO" in the body is fair, but I think calling it an APO in the heading is a bit deceptive... APO usually refers to refractors, the DGM should be called an unobstructed reflector or Off-Axis (OA) reflector, as DGM properly calls them.

Jarad

August 8, 2004 09:58 PM Forum: Equipment Talk

Portability of 18" Starmaster

Posted By Jarad Schiffer
I had one of these - I doubt it would fit in an accord. I used a subaru outback and a saab 9-3 hatchback for it. You can measure yourself - the scope needs 2 30"x30" squares if you remove the mirror cell, and 1 30x30 square if you leave the cell in (but then it is taller....).

Jarad

August 30, 2004 01:12 PM Forum: Equipment Talk

Things you'd like to see....

Posted By Jarad Schiffer
A focuser for fast dobs with a Paracorr lens built in to the drawtube. Essentially, the lens assembly of the photo-visual paracorr threaded into the bottom of the drawtube. It would save some weight and in-travel issues compared to putting the paracorr into the focuser. If it was done right, it might even be able to use the 1.15x barlow effect to make the focuser effectively lower profile and allow a smaller secondary to be used.

Jarad

September 1, 2004 01:27 PM Forum: Equipment Talk

Telescope sizes: inches vs. mm

Posted By Jarad Schiffer
As Nigel from Spinal Tap would say:

"But inches are bigger!"
8)
Jarad

September 9, 2004 01:19 PM Forum: Telescope Making

Dob equatorial platform

Posted By Jarad Schiffer
Chris -

Go to Cloudy Nights, and look in the Reflectors forum. There is a group there getting together to build a set of platforms (saving money by buying and machining in bulk). One of the memebrs ia machinist, who will be doing the cutting, and another is skilled with electronics and will be doing the controllers.

Jarad

September 20, 2004 08:09 PM Forum: Eyepieces

LOW POWER WIDE FIELD

Posted By Jarad Schiffer
That sounds kind of funny to me - the Panoptics are usually pretty sharp to the edge. You might want to try someone else's 35 Pan in your scope next time you are at a star party. If theirs is noticeably better, you might want to send it back to TV for repair.

Assuming it's not a defective eyepiece, I am not sure what you are seeing. My 35 Pan does pretty well to the edge in a 14.5" f4.3 with a paracorr (effectively f4.95). Is it uniform all around the edge? If it is noticeably worse on one side, your objective might be out of collimation (unusual for an AP, but possible, and correctable). Actually, the diagonal could be out of collimation too (more easily correctable). How little distortion are you talking about?

Jarad

September 22, 2004 07:29 PM Forum: Telescope Making

calculating seconday size

Posted By Jarad Schiffer
Download Newt 2.0. Do a google search for it, it is a free program by Dale Keller. Depending on your tube size and focuser, 1.83 is probably about right for general use. You could get away with one size down (1.52" I think) if you use a relatively narrow tube or UTA and a low profile focuser, but you may notice some vignetting in low power wide field eyepieces. If you plan to really concentrate on planets it might be worth it, but 1.83 is already below 20% so it will still do well on planets with that (and I have a 10" f5.6 with a 1.83" scope that does quite well on planets).

Jarad

September 23, 2004 06:53 PM Forum: Telescope Making

Help with a 14

Posted By Jarad Schiffer
Here are a few suggestions:

First, most stepper motors use 4 wires. There is one set of 4 in the picture you posted, so I would check them first. Second, if you have access to a voltmeter or better yet to an oscilloscope, I would try checking each wire for voltage and/or pulses when you press the buttons on the Dec controller. Third, can you see where each of those wires is going? I.e. do some of them coem from the controller, go to the motor, etc? Last, see if there are any markings on the motors themselves - they are probably steppers that Starliner bought from a someone (Hurst, maybe?). If you can identify the motor, you can contact that company to get the wiring diagram for driving it, and hopefully figure out which input wires go where. Last, can you see where each of those wires is going?

Hope this helps,

Jarad

September 28, 2004 08:11 PM Forum: Equipment Talk

How heavy is Too Heavy???

Posted By Jarad Schiffer
Usually the load capacity listed for a mount is the OTA only, not the counterweights. The other factor to take into account is the tube length. You will have no problem with a 13 lb, 6" SCT or MCT on a GP mount. A 13 lb 6" short FL refractor or reflector will probably be okay, but approaching the limit. A 13 lb 6" f15 achro will probably overload it (too much leverage, you will get more vibration).

Jarad

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