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Posts Made By: Keith Lawson

June 15, 2005 05:37 PM Forum: Equipment Talk

One For Roland Christen

Posted By Keith Lawson
After looking at the responses to my questions I'm beginning to get the feeling that the poor amateur astronomer is left at the mercy of manufacturers concerning the optical quality of their compound instruments. I know that gross errors are easily identified, but getting an actual wavefront analysis seems to be beyond the "average guys" ability as far as having the right equipment is concerned. Everyone can do a ronchi test as well as the star test but as Roland has stated in his articles, the star test can be easily misinterpeted on compound instruments and the ronchi seems useless as well leaving the poor telescope owner with no where else to go as far as knowing the quality of the instrument he owns.

September 21, 2005 04:31 AM Forum: Equipment Talk

Vandenberg Sunset Launch Thursday

Posted By Keith Lawson
I'm glad you posted this. I will be looking for it Thursday evening. It's been a while since I have seen one of those. They are quite spectacular!

November 2, 2005 02:38 AM Forum: Equipment Talk

Mass Produced Truss Dobs

Posted By Keith Lawson
My, my..... Looks nice for a mass produced scope.... 8)

November 25, 2005 07:20 PM Forum: Telescope Making

Tube material vs. cooldown?

Posted By Keith Lawson
Hi,

Looking back on all the newtonians that I have owned over the past 30 years my opinion is that the tube issue has been blown well out of porportion. Since the majority of telescope tubes are oversized (to eliminate thermal issues because the currents tend to stick to the walls) one should begin to look at the optics as the main source of tube currents.

Aluminum will cool to ambient temperature 99 times faster than glass. Under the night sky aluminum tubes will be close to the ambient temperature. The real cause of tube currents is the primary mirror. A simple out of focus star test will show where the currents are coming from in any newtonian telescope. In my experience it has always been the primary mirror. This is why most of my newtonians were cooled. I have used fiberglass, phenolic, steel, wood and aluminum for tubes. It never made much of a difference what I used. The tube decision was based on the telescope design and what was availiable at the time.

If you are into deep sky-low power views, don't fret yourself over tube materials but if you are into high power lunar planetary, multiple star observing, consider cooling the scope. In my research I found that 1/2 degree temperature difference in 36 inches of air is equal to 1/4 wave error.

Keith

December 22, 2005 05:57 AM Forum: Eyepieces

Planetary eyepieces??????? 2nd posting

Posted By Keith Lawson
I'm currently testing the Burgess/TMB planetary 9mm, 6mm, and 4mm in a 7" F/9 Apo and 5" F/15 Achro. So far I'm impressed with their performance. I have used Orthos, Plossls, and the like over 30 years. This is the first time that I can remember being this impressed with eyepieces. The stars are pinpoint to the edge of a 60deg AFOV. I'm finding the images crisp and clean with lots of contrast. It's kind of like looking through a high end ortho with an increased field of view and lots of eye relief. The cost is only 99.00 each. If they come out with different focal lengths in the future I will not hesitate to buy them. The testing continues 8) Just my two cents worth.

January 28, 2006 11:16 PM Forum: Equipment Talk

New Meade MAX Mount

Posted By Keith Lawson
Another Pic. My 178ED would go nice on this 8) Ahhhh..... Dreams wink

January 31, 2006 06:08 AM Forum: Refractors

FS-128...... value

Posted By Keith Lawson
Go to the Amart classifieds and do a search for "TAK FS-128" This will give you a general guideline as to what they are selling for smile

February 2, 2006 01:29 AM Forum: Eyepieces

Antares Elite Plossls

Posted By Keith Lawson
I have the complete set. I think they are excellent and underrated. I never used them in a F/4.5 telescope but they have worked very well in a 6" Mak, C8, C11, 6" F/8 Achro, 7" F/9 APO, and 12.5 F/6 Newtonian. Some may consider the 7.5mm and 10mm to be a little tight on eye relief but the eye relief is the same as any other plossl or ortho. I use Burgess/TMB planetary eyepieces now for my high power views but the 7.5mm and 10mm Antares were my choice for lunar/planetary/multiple star views before the Burgess/TMB's. I bought the Antares to replace a set of orthos I was using at the time. It was a good choice. Hope this helps.

February 11, 2006 04:15 AM Forum: Telescope Making

Converting an f/8 to an f/16

Posted By Keith Lawson
Go with a built-in barlow. Put the barlow before the diagonal mirror. This would reduce your secondary, and increase you image scale by a large amount. Off-axis coma is improved. I built one using a 10" F/6 primary back in 94. I still have the machined barlow/diagonal. The major diameter is 1.5". It will work with a scope up to 12" F/6. I can post a picture of the barlow if you are interested.

February 18, 2006 01:32 AM Forum: Eyepieces

OK, the subject has been beaten to death!

Posted By Keith Lawson
Thanks Floyd for putting some control on that thread. I was afraid to stick my opinion in there for fear of being shot at wink When I ask for opinions concerning certain products that I'm considering for purchase I value the opinions of actual end users of the product.

For eyepieces, the users scope info is important as well since what may work well in a 8" SCT at F/10 may be horrible in a F/4.5 DOB.

I've been using telescopes long enough to remember the "joy" of using a good Ramsden eyepiece. In a 6" F/8 scope they work quite well. BTW, I have the 4mm, 6mm, and 9mm Burgess/TMB eyepieces (the 5mm is on order) and find them to be superb lunar/planetary performers in my Meade 178ED. The 6mm was the 1/2 price model.

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