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Posts Made By: Allen Tracht

June 10, 2005 03:42 PM Forum: Equipment Talk

Standard Eyepiece Mechanical Specs

Posted By Allen Tracht

Does anyone have accurate OD and filter-thread specs for making custom accessories? I thought there was a table somewhere on the web, but I can't find it.

Allen

June 23, 2005 07:13 PM Forum: Equipment Talk

Best DSC pointing model

Posted By Allen Tracht

Of the various DSC computers, is there a real difference in how easy they are to perform alignment, and how sophisticated the alignment model is.

For example, with a very rough polar alignment, my G11/Gemini doesn't need the initial OTA aim to be precise, but the Argo Navis manual says that the OTA should initially be accurately aimed to be perpendicular to the polar axis or accuracy will suffer.

Among them, are any notably better at developing an accurate pointing model that includes real-world imperfections in the mount such as non-orthogonality and backlash over the meridian?

Finally are there computer-based (either hand-held or laptop) solutions that are better?

I look forward to your replies. Thanks.

Allen

June 29, 2005 04:28 PM Forum: Telescope Making

Interesting Tools

Posted By Allen Tracht

Here's a vacuum pen that may be useful when handling small optics: http://www.ares-server.com/Ares/Ares.asp?MerchantID=RET01229&Action=Catalog&Type=Product&ID=82304

Typically, I've seen these for $35-$50+.

Also, they have a bending machine that might be useful in making custom tube rings. It's expensive ($95), but it might pay for itself in one or two uses:

http://www.ares-server.com/Ares/Ares.asp?MerchantID=RET01229&Action=Catalog&Type=Product&ID=81356

Caveat: I haven't used these tools, but I am intrigued.

July 11, 2005 08:55 PM Forum: Equipment Talk

Kick the habit

Posted By Allen Tracht

I'm getting less and less pleased with cigarette-lighter plugs for 12V power. They just seem to lose contact at the most inopportune time, like in the middle of a public star party. Does anyone have experience with more reliable types? It would be great if they include both in-line (both parts on the wire) and panel-mount, and that are reasonably water-resistant (in case they're lying in the wet grass).

-- Allen

July 13, 2005 04:37 AM Forum: Equipment Talk

Shrinking a Telrad (long brainstorm)

Posted By Allen Tracht

It would seem that the Telrad could be made about 2-3/4" shorter if the battery pack were replaced with something smaller. Then the entire unit could be shortened to eliminate the now-empty space.

The battery pack could be replaced with a small linear regulator for use with external power (which you might have anyway for a dew heater), or a coin cell, which might only last 1/5 as long, but still should be good for days of use.

This might take some delicate surgery, especially if you want to maintain the quick-release feet (at a reduced spacing), but it seems possible.

I envision cutting the body just in front of the attachment of the reticle assembly, and just behind the front feet and then joining the parts. I may leave a little extra length for the pulser.

Why would I attempt such a thing? Well, I really like the Telrad: it's reticle is relatively large, well calibrated, and has little parallax. It's also reasonably priced for its quality. Furthermore, several useful accessories are for it: solar finders, right-angle mirrors, and pulsing.

I could also envision removing most of the base until it is barely thick enough to the Telrad feet.

The Telrad won't ever be svelte, but perhaps these changes would make it less awkward.

Good idea? Bad idea? Let me know. Also, do you know an appropriate adhesive for reattaching the parts?

Allen

July 20, 2005 03:48 AM Forum: Equipment Talk

Solar H-alpha Bandwidth

Posted By Allen Tracht

In other threads, the 1.5-Angstrom bandwidth solar H-alpha filter (from Thousand Oaks) was described as a "prominence-only" filter, unable to see many of the surface details. Obviously, its bandwidth is too large. However, is there really a visual advantage in going from 0.9 to 0.7 to 0.5 Angstroms?

How does the new Thousand Oaks filter (rated at a bandwidth of 0.9 Angstroms) on a 4-5" refractor compare to the PST (rated at <1.0 Angstroms)?

Allen

July 21, 2005 03:18 PM Forum: After Dark

Sponsor Page Usefulness

Posted By Allen Tracht

I'd like to be able to use the sponsor page to find astronomy gear, but the current format gives no hint as to the products or services supplied by the various sponsors. A new format, providing more information, would probably make sponsorship more valuable both to the shoppers and the sponsors.

My immediate ideas include either grouping sponsors by the types of products or services they supply, or by using more pages to add a short description of each (or do both). Of course, you may have a better way to provide this info.

Allen

July 26, 2005 10:15 PM Forum: After Dark

Space Shuttle

Posted By Allen Tracht

Is there a sight that gives visibility/position of the shuttle?

August 22, 2005 09:31 PM Forum: Equipment Talk

Daytime DSC

Posted By Allen Tracht

If possible, I like to get my DSC aligned before dark. With my G11/Gemini, I can do a rough polar alignment (using a compass), and then "go to" the Sun (with a filter) for my first alignment object, and then the Moon for my second. At that point, I'm usually well enough aligned to get the bright planets in my scope well before dark. This is especially good P.R for public star parties.

Unfortunately, the G11 is less portable than I like, so I've put together a TV-101 on a DiscMount DM-4 w/ Sky Commander. Much more portable and I don't miss the tracking at moderate powers. But I do miss the Gemini's alignment capabilites. Sky Commander's 2-star method is just not in the same league.

Do any of the other DSC computers have such Gemini-like abilities? Or are there even PC-based systems that can do this?

Allen

August 27, 2005 01:53 AM Forum: Eyepieces

Evepiece Simplification

Posted By Allen Tracht

It's raining out, so I'm trying to organize and simplify my eyepiece collection. To my surprise, I still find a few holes in my lineup so I'll probably have to trade one here or there to make things work.

Major considerations:

1. Use what I have. Free up some eyepieces for sale if possible, trade if necessary, but avoid spending more money.

2. Have enough eye relief to keep my glasses on, if possible. This, along with the previous consideration inhibits me from getting short focal-length Naglers.

For my FS-128 on a G-11, I propose:
55 Plossl (46 mm field stop)
35 Panoptic (39)
22 Panoptic (25) or 17 Nagler T4 (24)(opinions?)
12 Nagler T4 (17)
8, 5 Radians (8, 5)
3-6 Nagler zoom (2.6-5.1)

I also propose to use the same eyepieces on a 16" F4.5 (F5.2 w/ Paracorr), except for the 55 Plossl if the central obstruction is bothersome.

My TV-101 on a DiscMount is my travel scope. The mount works best if the eyepiece weights (w/ adapter as needed) are similar so I propose:
55 Plossl (46 mm field stop, 1.13 lbs)
24 Panoptic (27, 0.51 w/ 0.75 = 1.26)
12 Nagler T4 (17, 1.01)
8 Radian (8.3, 0.6 w/ 0.75 = 1.35)
3-6 Nagler zoom (2.6-5.1, 0.33 w/ 0.75 = 1.08)

I look forward to your comments.

Allen