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Lawrence Parchman

Sculptor Galaxy (NGC 253)

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Posts Made By: Alex McConahay

May 2, 2007 02:29 AM Forum: Beginning Astronomy?

flexible couplers for RA drive

Posted By Alex McConahay
what kind of mount?

Alex

May 5, 2007 12:58 AM Forum: Equipment Talk

Counterweight

Posted By Alex McConahay
Jay,

In a properly designed and executed Dob, there is no counterweight needed.

A Dob is supposed to be engineered such that the secondary (eyepeices and finders and all) and primary assemblies balance perfectly on the bearings.

However, that is harder to do than to say. And it gets really hard if you have a variety of things to add up there in the secondary. A simple plossl weighs a whole lot less than a binoviewer with two 31 Naglers. So--the real answer to your question is....it should take no counterweights with your standard eyepiece arrangement. But practically speaking, it may be easier to add weights as needed than to adjust the Dob in any other way when changing the setup or if it does not balance right in the first place.

(Before those with weight down on the primary box go off on me, I will concede that you can get a shorter scope some times by adding weight down below, but.....)

Alex

May 9, 2007 01:45 PM Forum: Equipment Talk

Cotton for cleaning mirror

Posted By Alex McConahay
The issue is not whether it is surgical, but whether it contains something it should not. Many "Cotton balls" are part polyester--and that may cause problems when you use alcohol.

So, call it 100% cotton, and it will be easier to find.

Alex

May 17, 2007 06:36 PM Forum: Equipment Talk

Premium Focuser or Electronic Focus?

Posted By Alex McConahay
For Visual I prefer the faster focusing manual method. For Astrophotography, I prefer leaving it to the electronic.

Alex

May 20, 2007 12:24 AM Forum: CCD Imaging and Processing/Deep Sky

LRGB question

Posted By Alex McConahay
Actually, I think you have made some assumptions here that are not valid.

You want the L shots taken when the object is at its sharpest--closest to zenith. This is because the job of the L shots is to be sharp and define the detail.

Your color shots, being binned, are not meant for sharpness, and so can be taken when the object is a little lower in the sky.

SO, you are actually most likely to take your color shots early and later in the evening, and your luminance when the object is straight overhead.

Alex

May 21, 2007 12:18 PM Forum: CCD Imaging and Processing/Deep Sky

Draco Trio

Posted By Alex McConahay
Looks good. I'm adding to my target list.

Alex

May 21, 2007 07:59 PM Forum: CCD Imaging and Processing/Deep Sky

M13 and more...

Posted By Alex McConahay
Very well done!

Alex

May 28, 2007 07:45 PM Forum: Equipment Talk

Book recommendation

Posted By Alex McConahay
I go away for five days and look what happens!!!

Star Hopping for Backyard Astronomers--Alan MacRobert
and
Turn Left at Orion by Brother Consa.......(I can't dig it out right now)

are a must for planning star hops for this type of thing.

Alex


May 29, 2007 01:52 PM Forum: Digital SLR AstroPhotography

DSLR's with picture preview

Posted By Alex McConahay
I understand Fuji is about to put out a Medical and Police work camera that has infrared sensitivity---but I cannot recall if it has live viewscreen.

Alex

June 4, 2007 01:28 PM Forum: Deep Sky Observing

Declination and Galaxy details?

Posted By Alex McConahay
Height above the horizon is a lot more important than declination. If you are looking at something low in the sky seeing will be worse, light pollution will be worse, and this will detract from dark skies, surface brightness, and all.

Of course, declination will determine the height above the horizon. Alpha Centauri (granted, not a Galaxy) is a spectacular object from the Southern Hemisphere. But it ain't much from here in SOuthern California. The LMC also has lots of detail from Tahiti, but is invisible from here.

So, in itself, declination has nothing to do with how a galaxy looks. But taken with your latitude, it has a lot to do with it.

Alex

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