Posts Made By: Ed Moran

First a C90, then:

C8
Orion XT8
NexStar 11

now a Discovery 12.5" PDHQ.

Oh yeah, I just picked up an 80mm f/5 shorty on A-Mart...

It looks great! You might want to make sure you have some more material on hand, you'll probably be getting a few requests from other Pentax owners!

Ed

P.S I'm going to Mt. Pinos on Sunday, and next Saturday too. Maybe I'll see you there...

Thanks everyone, for the advice and links!

I see that I have several choices...I'll wait until the fever subsides to make a rational decision

"Rational decision", yeah, right...who am I trying to kid?

"Are there cheaper alternatives to 24 Pan that work just as good? (As good in 80% of FOV is not good enough.)"

If you mean a very wide angle afov with a 1.25" barrel at around a 24mm focal length, probably not. If you mean the same true field of view as the 24mm Pan but are willing to accept a longer focal length, anyone of the premium 5 element modified plossls with a focal length around 30mm-35mm(Ultimas, Ultrascopics, Parks Gold Series, etc.) will give you sharp to the edge of the fov (limited only by the curved focal plane of the SCT design), high contrast images at a more reasonable price.

"Do you feel there are any magnification gaps here?"

Not really. Although if you have a good barlow, you might substitute a 16mm T5 for the 13mm T6 since a barlowed 24mm Pan would give you a 12mm option.

"Finally, how do the three work with reducer/corrector?"

There shouldn't be any problems with that. The 24mm Pan with the r/c will give you about 1.3 degrees tfov, un-vignetted (assuming an f/10 8" SCT), about the maximum possible for you. The 13mm and 9mm T6's would work equally well, but I only used my r/c with my longest focal length eyepieces, trying to stretch the true field of view to the limit. When using shorter f/l eyepieces I was aiming for higher magnifications only.

I've observed a few times with a 24mm Pan in an 8" f/10 sct and thought it worked very well. Sharp, high contrast, most pleasing.

My two cents worth:-)

Ed

jean bruno said:

I would like to know if I buy the Nagler 31 mm for a C11 is the better choice for Deep Sky Objects

We need a few more details before we tell you how to spend your hard earned money , but here are my thoughts.

For a f/10 11" SCT, assuming performance is a priority versus cost...

Large DSO's like M42, Double Cluster, M31, large open clusters, etc., your best choice might be the 41mm Panoptic, giving you 1.0 degree tfov versus about .85 degree for the 31mm T5. You're limited to about 1.0 degree tfov (un-vignetted) anyway, but you might as well use it all.

Medium sized objects like the Swan, Lagoon and Trifid nebulae, larger galaxies and the larger globular clusters really shine in a 22mm or 17mm T4, or perhaps the 20mm T5.

Ed

Here's a pic of mine (well, it USED to be mine... 8)

It's not all the way up, only about 3-4 turns.

Thanks Linton and Don!

The tools should arrive next week so I'll get the chance to try the techniques you've suggested.

Thanks again,

Ed

Darlene,

Have you tried Mars Previewer II? A Google search should find it for you quickly. It really helps me identify Martian surface features...

Ed

A very nice, professional-looking installation

I'll bet you can't wait to try it out!

Ed

Another way to visualize the problem (for me) was to imagine the scope pointed at an object located on directly on a line of Right Acension when that line is directly, perfectly overhead. The object, for the sake of the discussion, is 45 degrees above the horizon. If I rotate the scope in azimuth _exactly_ 180 degrees (using the encoder output for reference) it should then be pointing at that same line of RA, but on the other side of the sky. But with my 3/16ths offset it would actually be off by at least .25 degree, and probably twice that amount because the scope, having rotated 180 degrees, is now an additional 3/16ths off.

I could be completely wrong about this, of course , but the math seems reasonably correct to me. Comments and/or corrections are welcomed!

Ed