Mirrors, diffraction spikes, and clarity

[The Warthog]

I have two telescopes, one a Meade 4.5", and the other a Tasco 4.5". I have been using the Tasco exclusively since I bought it, because the views at high magnifications are so much better than the views in the Meade. I have put this down to the possibility of the Meade having a spherical mirror, and the Tasco a parabolic one. This is partly because I can get the stars in the Tasco focused down to better points than in the Meade, at high (225x) power. I can also consistently see the bands of Jupiter in the Tasco.

Now I am wondering to what extent some of this difference may be caused by the fact that the Meade has a three-armed spider, and the Tasco only one arm? The Tasco would certainly not produce diffraction spikes the same way the Meade does, and spikes do interfere with viewing at high power.

Anybody's guess?

[Astroman]

Interesting....How thick are the respective arms as seen by incoming parallel light? Three vane spiders are generally very thin, >1/16" while the "stalk" used by Tasco is thicker ~1/8".

I'll assume collimation is not the problem, nor is pinched optics. I'd think the spiders wouldn't make the overall difference you describe, but spherical v. parabolic might. Something you could try would be looking through a narrow band filter-OIII, H Alpha or a photometric filter would be best, (UBVRI). Or, a simple Ronchii test would show any problems.