[Lvas] Virgo Cluster Identification

Thu Mar 19 17:37:21 PDT 2009

Roger,

You have a very nice house and yard. Could do without the snow though!

Great notes on the smaller scopes. Back in the 60's, a 12" was a monster so I was quite happy to have my first home-built 8" Newtonian. It was probably the equivalent of what my 16" is now in terms of being right in the middle of the size range for amateur scopes.

Fred

From: drivester at hotmail.com
To: lvas at lvlug.org
Date: Thu, 19 Mar 2009 23:46:54 +0000
Subject: Re: [Lvas] Virgo Cluster Identification

Fred,

Thanks for the kind words regarding my sketches...however you have accomplished what I have been working on since 1994. The Herschel 400 list. It requires both notes and sketches. This is a very difficult project and some of the objects are very faint. You are now working on the H-ll list...very few observers get to this level. 

My excuse. Since I can't seem to leave my backyard many of the more southerly object's are invisible from my house. I have about 200 of the H-400 objects and have pretty much resigned from this endeavor.. I seem to have too many personal observing projects to continue this list. 

I have shown you my "humble observatory" before but I am going to send a picture of my house looking north. The pine trees are at the extreme northern part of my yard blocking most ambient light from that direction. As you will notice I have a pretty nice northern sky in the back. 

The little brown building is where I put my telescope after a night of observing. I have drawing tables, astro-chairs, sketching and note books, and too much other stuff to list. It is difficult carrying all of it back inside at 1:00 in the dark. In the morning following I will bring all my stuff back in by the light of day.

Regarding small scopes: Many years ago I always thought that the perfect two scopes would be a a 10-inch Equatorial, and a 4-inch EQ refractor...to use as a portable scope. I ended up with both of these scopes and the combination has worked very well for me. I was always intrigued at the things Walter Scott Houston was seeing with his "vintage" Alvin Clark refractor in his "Deep-sky Wonders" in S&T. He began writing this article in 1946 until his death in 1993. I believe my dates are correct.

I try to observe many of the objects that he saw and talked about all those years...using my 4-inch.

John Heller actually has the refractor that I would love to have. A relatively short focal length 127mm refractor of excellent quality. This would be an excellent double star scope as you could actually separate double stars under 1-arc second. The 1-arch second is an observatory standard regardless of the size of the telescope. 

Conditions do not often allow much better than this...especially if there is a significant difference in the magnitude of the primary and secondary. Dawes limit is based on two equal magnitude stars of 5.5 magnitude. The greater the difference in magnitude between the two the greater the degree of difficulty.

The formula is 4.56/Aperture of the scope...for equal stars both primary and secondary.  

A 5-inch = 4.56/5 = 0.9 with 5th magnitude equal stars. A 6-inch F/8 reflector of "superb" quality can be a challenging instrument to a 5-inch premium refractor.  

As we all know the light gathering capacity of a scope is directly proportional to the square of the aperture. 

A 4-inch scope squared is 16, and a 5 inch of course is 25.  
25/16 = or 1.56 more light gathering capacity of a 5-inch versus a 4. I could really use this extra brightness as compared to my 4-inch.

Some of you guys are smarter than me...please check my math. Do you agree? 

One thing to remember...a big scope will always out perform a smaller scope if both are of the same quality, and the same type of scope. The only advantage of a small scope is the sheer convience and the ease of set-up.

If I can only observe an hour or so it is much easier to set-up my 4-inch than my 10-inch. I will then select some of the WSH objects and see if I can resolve the same details that he spoke of for so many years. 

Roger Ivester

    I can see how it might be possible for a man to look down upon the earth and be an atheist, but I cannot conceive how he could look up into the heavens and say there is no God.      Abraham Lincoln

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