Posts Made By: Steve Lathrop

Here is what I want to be able to do (for instance)...

From a good dark site, using easy direct vision, see:

Spiral structure in M51;

Spiral arms of M81;

Dust lane of M104;

Spiral structure of M33.

Have seen all these with averted vision and/or lengthy observation using a TV-102. Now I want to see them RIGHT THERE.

What is the least expensive scope which would permit someone to do this?

Could it be done with a Starmaster 11 or 14.5? Need something bigger?

Something less expensive that could do the job?

Any comments?

Steve

Seems like there are a lot of achromats out there in the f8 to f10 range. Would it improve things to stretch a mass produced achromatic objective to f12. How about a 90 mm f12 achromat with a 2-inch focuser on a simple alt-az mount as a first scope, supplementary scope kind of offering.

What should it cost? Could this be a price/performance sweet spot?

I'm looking for something to interest a really bright 8-year-old nephew who has expressed an interest in the sky. I think collimation would be a bit much, so a Dobsonian is out. This imaginary scope is what I would like to find.

Steve

I have a TV 102. I'm particularly intererested in hearing from anybody who has an apo refractor of about 800-1000 mm focal length.

Have you used the 26 Nagler T5? Have you used the 35 Panoptic? Have you compared them?

I already know what the numbers suggest with regard to magnification and field stop. What I would be pleased to hear about are subjective impressions in reference to particular views.

Steve

Has anybody got experience with the CG-5 mount and the RA motor drive? Not concerned with GOTO, but would like to know if this mount could work for non-telescopic film photography using a 350 mm telephoto.

Another use would be high-power (297x) visual observation of planets and the moon using a TV-102.

Suitable?

Steve

Anybody have any opinions on whether someone might be as well served with the TAK as the AP?

Steve

I am thinking about supplementing my 4-inch APO with some kind of Dob, to better observe galaxies. At my location the best conditions just barely disclose the milky way. A casual observer would never notice it.

Although I can locate quite a few galaxies with the 4-inch, I can't really observe most of them. Based on what I read here, I assume a dob of some size will make a big difference on those. Is a 12.5 Starmaster, or similar, going to be big enough to make a major difference on these targets under these conditions?

Taking it the next step: I can't see M101 at all unless I go to a dark site. Is that likely because my sky background is brighter than anything in M101, and therefore a dob wouldn't see it either, or might a 12.5-inch dob actually reveal galaxies that are totally invisible to my 4-inch because of light pollution? (I know the dob would show galaxies that are too faint for the 4-inch under dark skies, but this is a different question, focusing specifically on faint objects being totally washed out by light pollution).

Finally, please notice that these are not questions about whether aperture wins, or wins under light polluted skies, or wins when you can stand an egg on end during the equinox. I stipulate to all that. I just hope some of you can maybe provide specific answers to the questions above.

Thanks for any help,
Steve

I'm thinking of buying a Dobsonian, maybe a Starmaster 11, Teleport 10, or Tscope 13. One big question is this: I live about 100 miles from dark skies, and about a 6-hour drive from really dark skies. I probably do the 100-miler 10 to 15 times a year. Longer trips might even be multi-day drives to the southwest from New England, stuff like that, once or twice a year. I drive a standard pickup, so there's room on the seat if the scope isn't too big, or I could put a shell on the bed.

The question is: can any precision Dobsonian be expected to stand up to that kind of repeated jostling, wear and tear. Would this be expecting too much? Should I maybe just continue as a happy refractor user?

Steve

Anybody care to say at about what magnitude the diffraction spikes in a 14-inch Dob become a visual non-factor?

Steve

I find exit pupils kind of confusing.

Seems like you can project an image of what you are observing by positioning a piece of paper at the proper eye relief distance for the exit pupil.

You can have an exit pupil so large that your fully dilated eye can't take in all the light.

You can have an exit pupil so small that tiny stuff in your eye interferes with your view.

One optical expert on this forum has written that the only thing the size of the exit pupil affects is brightness.

I don't see how all that can be true together.

Can someone please explain how the exit pupil and the eye interact, with a word or two about what changes and why when the size of the exit pupil changes?

Thanks for any help,

Steve

Any comments on what equipment is necessary to observe Sirius' companion?

Has anybody seen it with an XT-8 class Dobsonian?
A small achromat?

Steve