Image of the day

Captured by
Douglas Rollain

M20 Trifid Nebula in LRGBHa

About Astromart

My Account

New to Astromart?

Register an account...

Need Help?

Posts Made By: Jim Nelson

November 14, 2003 05:16 PM Forum: Equipment Talk

XT10 Collimation ?

Posted By Jim Nelson
The XT scopes are center-marked on the primary mirror - they have a small circular decal.

I wouldn't spend too much time debating the merits of various methods of collimating - any method is vastly better than NOT collimating. The XT6 is more forgiving of poor collimation, but the XT10 (which is F4.7, I think?) will certainly benefit greatly.

December 5, 2003 04:07 AM Forum: Equipment Talk

Powermate v. Barlow

Posted By Jim Nelson
For visual use at least, the main benefit is with long focal length EP's (the inspiration for the Powermate was the 'Panoptic Interface' to use when barlowing the 2inch Panoptics; I believe the powermate is essentially a barlow + interface in a single package).

I've had a Meade short barlow (not so great), a Meade #140 Barlow (much better), and now use a 2.5x Powermate. The PM outperforms the Meade 140 barlow by a noticeable but not huge margin, even though I don't use long f.l. ep's with it. The Ultima, however, is reportedly an even better unit than the Meade, so I assume the difference between the Ultima and a Powermate with mid-to-short f.l. ep's is going to be awfully slight.

January 28, 2004 05:07 PM Forum: Equipment Talk

first scope - getting close - need help

Posted By Jim Nelson
I've bought many "seconds" from Orion - not a telescope, admittedly - and have never been able to fault the item in the slightest. Note, these "seconds" could get snapped up at anytime, so don't dawdle too much.

I can't comment based on personal experience on any of these specific models. The 90mm gets good reviews and is a major bargain, but the 120 is a decidedly more capable scope and mount (but much heavier and bulkier).

January 28, 2004 05:24 PM Forum: Eyepieces

TV Plossls/Powermates: Poor Man's EP Set?

Posted By Jim Nelson
I've toyed with your solution in the past as well, but never got the 5x PM. I think it makes a lot of sense - your eyepiece focal lengths are close together, but that helps with the planetary powers...

It's those planetary powers that mess up any simple eyepiece plan, isn't it?

Although I think it's a good solution, have you used those high powers on an undriven dob? Depending on the dob, 240x-300x with only a 50 deg field might be a bit of a chore - but then getting widefield options at high powers gets expensive.

That's my babble on the topic.

January 31, 2004 03:21 PM Forum: Eyepieces

UO Ortho - Eye Relief Question

Posted By Jim Nelson
Yes, 4mm is right. That's about 1/6th of an inch.

The 5mm Ultrascopic is different from the Ultima, in that it's essentially the 10mm Ultrascopic with a built-in 2x barlow; eye relief is the same as the 10mm (about 7mm, if I recall correctly).

The Ortho may have slightly more eye relief, but not much more, than the 5mm Ultima.

Helix (one of the sponsors on the web page) knows the specs of all the U.O. eyepieces they sell.

February 4, 2004 04:34 PM Forum: Equipment Talk

An aperture question - refractors and dobs

Posted By Jim Nelson
I don't think that anyone's addressed the "Does one or two inches actually make a big viewing difference"?

If that's a leap from a 3inch to a 4 or 5 inch, then yes, it makes a significant difference. The difference between my old 70mm scope and a 100mm refractor is dramatic, for example, and that's just over 1 inch difference.

A 3inch scope has only 75% of the resolving power and about 1/2 the light gathering power of a 4inch scope; 60% of the resolution and 36% the light gathering of a 5 inch scope. These are noticeable, even big, differences.

If you're talking about the difference between a 15inch and 16 or 17inch scope, you're talking about hardly noticeable differences.

Small APOs are great for photography, convenient, give great views of doubles and planets that are pleasing even under less then perfect seeing conditions, capable of widefield viewing of extended deep-sky objects, and are "cool".

Worth the money? Moot point, I don't have the money. But I like checking out other people's.


February 4, 2004 04:49 PM Forum: Deep Sky Observing

No sky in Michigan

Posted By Jim Nelson
I'm in the east of MI, and my scope has done nothing but accumulate dust since...when? November? A brief clear patch around Christmas time coincided with a time when I was a) away from home scopeless and b) stricken with a bad case of the flu.

Yes, I'm bitter.

February 6, 2004 05:38 AM Forum: Eyepieces

When to Get a 2" ?

Posted By Jim Nelson
Well, it's never a "must", it's just if you're satisfied with the largest field of view you can get with 1.25" eyepieces. I'd love to have 2 inch capability for my 6" f8 newt. The biggest field of view I can get is about 1.4 degrees with 1.25 eyepieces; not really big enough for the Pleiades, for example. I can see the North America Nebula from good skies with a filter, but can only check out a portion of the "coastline" at a time.

Large fields of view are necessary for large objects (how about the Hyades?), make finding things easier, and are inherently beautiful - sweeping a 4 degree field of view through the Milky Way with a 4 inch refractor is one of my more memorable observing experiences from last summer.

The "need" for two inch eyepieces definitely gets more intense with big scopes and long focal lengths. But if you desire a 3 degree field of view, than any scope much over about 500mm focal length will need 2 inch capability; if you want at least a 2 degree field of view, any scope much over about 800mm focal length will need 2 inch capability.

February 12, 2004 07:50 PM Forum: Deep Sky Observing

McNeil's Nebula

Posted By Jim Nelson
How cool is that! When you wrote "new nebula", I didn't quite realize it meant *new*.

February 13, 2004 05:02 PM Forum: Equipment Talk

80mm Binoculars vs Orion ST80

Posted By Jim Nelson
I feel like the minority voice here, but I'm not a big fan of big binoculars. I do like them, but they've never seemed too necessary to me *in addition to* something like an 80 Rich field refractor, which is far more flexible.

A nice pair of small hand held binoculars are far more useful for quick looks and scanning fields before star-hopping with a scope. I'm also in the minority view that thinks tha 10x50's are a bit "too much" - a little too hard to hold steadily. 7x50's, or even 8x42's, are a littler nicer. But I'm not a big guy.

On the other hand, there was a nice trick mentioned in a S&T letters section a year or so ago about using a swivel-headed attachment on long handle as a quick "prop" for steady views with heavy binoculars. A few dollars at a hardware store and *now* I can easily see Jupiter's moons in my 10x50's, and split Albireo, etc.

Funding Member

Sponsors


View all sponsors

Search