From: Willie Strickland <cwskas@earthlink.net>

Date: February 21, 2010 3:26:30 AM MST

To: Astro_IIDC@yahoogroups.com

Subject: Re: [Astro_IIDC] Mars with a 74" reflector!!!!!!!

Thanks Jim for sharing the photos.  It must have been quite a good time, even if the results didnt turn out as well as you wanted.

I really enjoyed seeing the mosaic of scope images.  Do you know who made this scope?  I am also curious how long the mirror/dome had been cooling before you shot your frames.  Did you view visually?  Did you check collimation on a defocused star?  Do you have an estimate of the seeing value, perhaps from frames shot using a star?  Did you focus using a star?

Just curious about the circumstances.

I have found that on the 24" here, collimation and focus are quite critical, just as it is on smaller scopes.  I suppose even more so.  Also, I always let the mirror cool for at least 30 minutes before attempting to image.  That is sometimes not enough.

Our site/scope is definitely seeing limitated. The best I have personally observed was just under 2 arcsec, but expected seeing for us is probably more like 3-4 arcsecs.  I am trying to develop a method that I use each night I am there to capture a history of the seeing, but I havent really nailed anything down yet.

Thanks again,

Willie

On Feb 20, 2010, at 12:55 PM, Alan Friedman wrote:

Thanks for this fascinating look at and through a large aperture telescope. Tell us more about the night and about the instrument. Did you observe visually at all?