Max magnificationg for galaxy viewing

Trying to get a consensus of opinions here:
Based on your experiences, what is the optimum magnification you use for observing details in galaxies? Also, what magnification and AFOV do you find most useful for locating them?

Also trying to get a consensus of opinions on the EP type you find best for viewing galaxy details : orthoscopic, Plossl or what? Thanks........Mike

Depends on what galaxy--

Milky Way--about 1 power.
Andromeda--About 7 to 10 (binoculars)
After that--depends on the night, and on the galaxy. I would say most observing is done at aobut 40 power.

Alex

Since you specifically stated that you wanted to observe "detail" in galaxies, I'd encourage you to try the highest magnifications that seeing conditions and the aperture of your scope will allow.
While many galaxies are "nice to look at" at low power, they take on a whole new demension at higher powers.
I'm fortunate enough to have a huge (28") StarStructure for deep sky observing and have found 300X - 400X to be a "sweet spot" for most galaxies (at least in this particular scope).
Try pushing your scope until you reach the point of diminishing returns.

Mike,

As Clifton mentioned, magnification is a function of aperture. Exit pupil, however, is not. I typically use exit pupils of 2.7mm (162x) to 1.7mm (259x) and sometimes 1.3mm (324x) when using the ASH 17" f/15 classical Cassegrain to observe galaxies. Obviously, these are not galaxies of large apparent size.

Having a large telescope with a drive permits high magnifications to be employed, when required, in this pursuit.

Dave Mitsky

As to your second question, many DSO observers prefer high quality wide-field or super wide-field eyepieces like the Tele Vue Panoptics and Naglers, the Meade UWA line, the Pentax XW (and now defunct XL), and so on, because they often are using undriven Dobs. A simpler design like an ortho may actually provide a marginally better view but the small apparent field of such a design is a bit of a drawback for DSO observing. For planetary observing, small apparent fields are not necessarily troublesome.

Dave Mitsky

You should read what Roger Clark, an expert on vision and deep-sky observing, has to say on this topic at http://clarkvision.com/visastro/m51-mag/index.html

There's also an excellent discussion by Mel Bartels at http://www.bbastrodesigns.com/aa/visual.html

A quote from the above:

"John Dobson was the first large aperture observer to point out the advantages of high magnifications. Al Nagler, and Brian Skiff, among others, have recommended high magnifications. By increasing magnification, you are decreasing sky background brightness, and making the object larger in apparent size, both crucial to detectability. For small extended objects, you may exceed the old double star observers' rule of 50x per inch of aperture."

The section on sensitivity and contrast at http://www.mailbag.com/users/ragreiner/eyeperception.html is worth reading.

In case you don't know, the easiest way to determine exit pupil is to divide the focal length of the eyepiece by the f/ratio of the telescope it's being used with.

Dave Mitsky

Galaxies come in different sizes and shapes. The galaxies of the NGC3190 group in Leo are so small that they can be overlooked at low magnification (40 - 60x). As Dmitri points out, it is a good idea to play with different magnifications to see what gives the best view. For the 3190 group, it will alomst certainly pay off to increase to 100x or more depending on aperture.
Even for the larger galaxies, like M101 and M33 increased magnification will be beneficial. I'm often amazed when I see how much darker the sky background becomes. But I prefer to keep the magnification low enough to keep the whole galaxy within the field of view.
For galaxies with high surface brightness and obscuring clouds, like M82 and M108, I sometimes use the highest magnification I have. And even for a galaxy with a relatively low surface brightness like NGC891 in Andromeda, the equatorial dust band is difficult to see with 63x magnification (12.5-inch scope), but becomes easy with direct vision at 167x.

Inge S

Hello:
It's interesting that you ask. I have both as 12.5" dob and a 12.5" cassegrain on a german equatorial mount. They both have the same light grasp, but I find myself seeing more details in the cassegrain. I believe this is becuse I can use higher powers since I don't have to worry about the faint fuzzy drifting out of the field while switching eyepieces and refocusing. For a detailed look at galaxies, i tend to use a 17mm Nagler, which gives about 280x and an 82 degree AFOV. The wide AFOV is useful in case I didn't center up on the galaxy well when I had the wider field eyepiece in, and to see more of the surroundings. For planetary observations, I'll use a Plossl since it'll give better contrast than the Nagler, but for the faint fuzzies I like the wider field of view. Naturally, this assumes that the galaxy will fit in 0.3 degree FOV. It is fun to look at some of the larget galaxies (M33, NGC253, etc.) at such high power to pick put details in them.

Cheers
Mike Connelley