Am I doing something wrong with my 8-inch dobsonian telescope?

Question

I bought an Orion XT8 after messing around with a hand-me-down refractor (no more details than that, except that I think it was a Meade or Bushnell, and I doubt it cost more than 100 or 150 bucks new) for several years. I have the 25mm eyepiece that it came with, and I also bought a "zoom" lens that I think goes from about 4 to 25mm. 

I live about 3 miles outside of a mid-sized city. The sky is black to the south, north, and west; it's light-polluted to the east. I've also taken the scope to places where the light pollution is minimal (all of the stars of Cancer were easily visible, if that means anything). 

I'm kind of disappointed. I wasn't expecting Hubble-style images or anything, but... now I can see two red bands around Jupiter, three on a good night. Saturn is more or less the same white blob as in the refractor, except that the rings are tilted more this year and I can see Titan and probably some of the other moons. The only feature I'm really pleased with is the Orion Nebula. Andromeda was a big sigh. 

I read tales of people using scopes like mine from, I don't know, NYC or something, seeing better than what I'm seeing. Talk of Great Red Spots and Cassini Divisions and whatnot. Great Red Spots and Cassini Divisions seem like a pipe dream to me, since I can barely see the equatorial bands and rings at all. 

As near as I can tell, the collimation is fine. So... am I doing something wrong?

REXS · Accepted Answer

No 1 - You have to forget Hubble, you may still have unreal expectations as to what a telescope can do. The Great Red Spot can be the same color as the background (it ain't "great" and "red"). You sometime see the dent it made in the band next to it then you can just make it out.

No 2 - You have to train your brain.It does not see planet detail off the bat. Look over several nights and look on good night (for you its gonna be a muggy night when all the "heat" is held down where you are). Its rising heat that causes bad seeing.

No 3 - Check Collmination.

No 4 - Its a short (f/5.9) mirror, so if they are going to sell you a screwed up mirror that would be that one. Short FL is harder to figure than longer FL. Go to an astronomy club, find the telescope guru, and have him/her check the mirror.

No 5 - A zoom eyepiece is crap --> worst of all worlds. Get a better fixed FL eyepiece and/or get a barlow. No telling what that scope can do till you use a decent eyepiece. Go to an astronomy club and barrow their eyepieces.

At 8" you should be seeing more detail, your problem may be some of the above.

? · Answer

IMHO, Aperture is King. So go for the largest aperture ... The eight" reflector. That you may get a tight first-class eight" reflector on a dobsonian mount from both Orion Telescopes or Meade. Dobsonian mounts are handy to transport, handy to gather and convenient to make use of for the period of staring at classes. Setup time from vehicle to watching is about 60 seconds ... No kidding. Avoid equatorial mounts are goto scopes they may be just to complex for a opening user. Consider me i do know. I possess a goto which i love but it surely took many weeks to grasp and most folks should not have that variety of endurance. I furnished a link below to Orion but do checkout probably the most different companies. Meanwhile you could additionally checkout your neighborhood astronomy club. They are going to even have some pleasant recommendations on what to look for in a telescope. The last hyperlink under is to a organization that presents superior optics in a telescope.

jimmymae2000 · Answer

I'm guessing there is something drastically wrong with the primary mirror. I built an 8 inch about 50 years ago and at 60 power could see a great deal of detail on Jupiter and could see saturn OK but it appeared much farther away.

Am I doing something wrong with my 8-inch dobsonian telescope?

3 Answers