Re: [APML] Re:I'm Feeling a Flame Getting Ready ...

["Andy Wallace" <andywallace@home.com>]

Roland--

 

I'm a rank amateur compared to many of the folks in this group but I have a few personal thoughts. First, many in this group consider this a film group, not CCD. Do your thoughts regarding resolution apply to high quality hypered film as well as CCD?. Secondly, and this is just my opinion, high quality refractors in the 4" to 6" range are the ideal photo instruments, especially when coupled to a mount of the quality you produce.

 

 Why doesn't everyone go that route??--long waits for delivery and relatively expensive scopes (although I think  yours are a bargain considering their quality). And, of course, some think the vital link in the quality astropic chain is the mount, not necessarily the optics which among various top end brands might be separated by a wave or two. Bobby, for example, uses the AP 1200 mount--which seems fairly sturdy :-).

 

Andy

----- Original Message -----

From: Chris1011@aol.com

To: astro-photo@seds.org

Sent: Saturday, February 24, 2001 10:50 AM

Subject: Re: [APML] Re:I'm Feeling a Flame Getting Ready ...

Did anyone compare the M42 image taken by Ray with a 4" aperture? He has two,
one taken with normal filtering, another with H alpha filter.

My question would be what direction will astrophotography take now that there
are wide field CCD imagers coming on board? Would a small, highly refined and
well corrected optical system do as good a job as a large brute force
telescope?

The question is not academic. I have perused scores of web sites for
outstanding images taken with CCD equipment. Most images show resolution on
the order of 4 arc seconds, even with scopes of 20"+ aperture. Few go below 4
arc sec on deep sky detail, although there are some. Even a 4" aperture is
capable of resolving 1 arc second, so what exactly is the advantage of brute
force (large scopes needing ever larger mounts to hold them). Is it light
grasp? Theoretically, an F5 system should place the same density of an
extended object on the detector in the same amount of time.

For stars, a scope with twice the aperture should have 4 times the light
intensity. However, if a scope of twice the aperture concentrates the light
of a star over twice the area, is not the light per unit area the same as
that of the smaller aperture? I understand that visually there is a gain, but
can a small aperture with higher inherent resolution compete with a larger
instrument?

Roland Christen