[When to Re-Coat Mirrors?]

I've landed and operated an ASA N12 astrograph in rural New England (US) since 2008, in an area with very little air pollution. How do I know whether the mirrors need re-coating? Or should this be done just as a matter of principle after more than 10 years?

Thanks, Bob Gillette

[looking for reliable small USB hub]

I've long used an inexpensive powered seven-port hub from Sewell in the US and three active USB extension cables to connect my observatory to my cabin about 10 meters away.

 

Bob

[QSI 5/6xx wsg on ASA N series Newton]

Hi Ralph,

 

I probably could correct the vignetting with flats, but lacking any other reason, I've never bothered with flats. Laziness, I guess.

 

Bob

[QSI 5/6xx wsg on ASA N series Newton]

Ralph,

 

Yes, I use a QSI 583wsg with 31 mm Astrodon filters on my N12, with the SX Lodestar guider (the only one that will fit with the ASA adapter.) I like the results very much, although I do see some vignetting at the corners. I just crop it out.

 

Bob

[diffraction spikes - "double" reflection on bright stars, Newtonian]

Pavel,

 

Your collimation, with CCDI error measurements between 2.9" and 4.6", is good, but not quite as good as Jim Fly's tools can make it. You should aim for 2" or less.

 

Maybe it's my eyes, but I still see nothing amiss with your diff spikes. I zoomed in and put a straight-edge on the screen. Looks to me like they line up.

 

Myself, I try to avoid huge bright stars in imaging. They're distracting.

 

Bob

[Old Forum]

...or just leave the old Yahoo site readable on line for a few months. If anyone has an unresolved issue, they can start a new thread here with reference to the old one (or Michael can import it on request, as he suggests.)

 

Bob

[diffraction spikes - "double" reflection on bright stars, Newtonian]

Pavel,

 

What am I missing here? The diff spikes on the bright star in your initial post look perfectly normal to me. Small spikes on less-bright stars indicate not bad collimation.

 

I use Jim Fly's tools on my N12, and usually achieve error between 0 and 2 arc-seconds. (It's very helpful, BTW, to have the primary mirror rotated so the adjustment screws align with the points of the target triangle.)

 

Best,

 

Bob

[Comet PANSTARRS - 4 May]

I'm slightly embarrassed to be the first to post a comet image here -- it's not in Gerald's league -- but in any case here's what PANSTARRS looked like in Cepheus, just above the trees in New Hampshire at about 03:00 on 4 May.  QSI538wsg on an ASA N12; L=4 min 1x1; RGB 3 minutes each, 2x2.

 

Larger image is here: http://tinyurl.com/cx6yewu

 

Thanks for looking,

 

Bob Gillette