[Aavso-photometry] Re Alt-AZ imaging

[Jim Roe]

Brad Walter wrote:
> There is another issue besides field rotation that I have noticed with any
> tracking system for dob (I looked at the website in your e-mail). The alt-az
> corrections are not smooth and continuous. The corrections are made in small
> but clearly visible steps. This is just fine for visual work, but even with
> a field de-rotator, it won't work for imaging. 

That might be true for some alt-az drives (and the tscope in
particular), but it is not true of all.  My experience with LX-200s in
alt-az mode shows no jumping and I've seen published images from other
alt-az scopes that look just fine.  See

<http://www.ghg.net/akelly/2292larg.jpg>

for an example with 19 (nineteen!) four-minute exposures (in various
filters) stacked.

Jim Roe
Wentzville, Missouri

Incidentally, that 80 cm telescope is about to be put back in service in
Missouri. :-)