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Captured by
Douglas Rollain

M20 Trifid Nebula in LRGBHa

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Posts Made By: dan hilts

April 16, 2013 12:54 AM Forum: Off Topic Discussions

Nice Utah Star Scene

Posted By dan hilts
If you pause the playback, it shows for a lot longer. Nice sky.

dan

May 28, 2013 11:04 AM Forum: Equipment Talk

2" diagonal internal restriction issue

Posted By dan hilts
The true restriction is the inside of the nosepiece on the diagonal. In all cases, the light cone tapers from the front edge of the nosepiece to the eyepiece field stop. This distance is about 4" so there is considerable amount of taper of the cone. The light cone also has to pass the length of the focuser tube as well before it gets into the diagonal so this too can be a real restriction. If the focuser tube is 4" long, there is a total path length inside the focuser/diagonal that is 8" long. A similar situation exists in SCTs with the baffle tube.

In a 4" f6 scope for example, the widest maximum fully illuminated field is only 20mm or so at the eyepiece field stop.

hope this helps,
dan

June 27, 2013 10:42 AM Forum: Eyepieces

a rather oddity

Posted By dan hilts
The magnification of a Barlow is defined by the formula M = 1 + (x/f) where x is the location of the final image behind the lens and f = Barlow focal length.

The final image must be at the eyepiece field stop when the everything is in focus so it seems you have two eyepieces with considerably different locations of the field stops, one towards the end of the eyepiece barrel, and one much further up inside the barrel. You can easily check this by using the eyepieces without the Barlow and noting the difference in the focuser position with each eyepiece.

Variable Barlows do so by changing the distance where the final image is formed, similar to what you have done using extensions. It is also common to change a Barlow's magnification in a refractor by placing the Barlow in front of the diagonal instead of after the diagonal.

Hope this helps,
dan


September 4, 2013 04:31 PM Forum: Home Observatories

Indirect lightning damage

Posted By dan hilts
Yep, sure looks like something let the smoke outta that chip.

Often surge damage will simply cause a transistor or other device in an IC to become near dead short. Once that happens, the unit's power supply will provide enough juice to create the heat that causes the volcano. Either way, it won't work any more.

dan

October 3, 2013 04:05 PM Forum: AstroMart FAQ

Rate someone with no deal

Posted By dan hilts
That has been my understanding. If goods/money do not change hands, no rating is to be given.

dan

December 12, 2013 03:13 PM Forum: Astro-Physics

Visit to Chile

Posted By dan hilts
Nice report. Thanks for sharing. I have yet to get to the southern hemisphere but it is on my bucket list. Maybe I need to move it up in my priorities.

dan

January 12, 2014 02:13 PM Forum: Eyepieces

Paul Rini

Posted By dan hilts
Mr. Rini has posted some items for sale on CN as recently as two months ago. As far as I know he has not been in the eyepiece business for a number of years.

dan

March 11, 2014 02:14 PM Forum: Off Topic Discussions

Calif Gas Prices To Go Ballistic

Posted By dan hilts
That's a bit of doom and gloom speculation. Other parts of the world already deal with significantly higher gas prices than the US. Here in Canada a US gallon is about $5.50 and for services like deliveries, freight, and postal service, it is a lot further between markets than it is in the US.

The article states, "will lead to price increases of at least 12 cents a gallon immediately." I see that kind of price variation everyday, often more. Last night gas was $1.25/L, this morning $1.32/L. That's about $.28/gallon fluctuation, everyday, and even more on holidays.

You need to be more concerned about the rising cost of food. You do have to eat.

dan

April 3, 2014 03:28 PM Forum: After Dark

eyepiece projection

Posted By dan hilts
A Barlow requires a significant amount of in focus. If it is working, I suspect your eyepiece should work.

Is there a possibility that you have removed the diagonal? If so, try it with the diagonal back in place. That may make the difference.

dan

April 24, 2014 05:31 PM Forum: LUNATICS

Are you sitting down? You are going to like this!!

Posted By dan hilts
Nicely done. We were completely clouded out for this event. Glad you got to enjoy it and glad you shared it.

dan

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