Image of the day

From the
ATWB Customer Gallery

Venus transit

My Account

New to Astromart?

Register an account...

Need Help?

Posts Made By: Dan D DuBal

April 3, 2003 07:24 PM Forum: Equipment Talk

Long Eye Relief (LER) Eyepieces

Posted By Dan D DuBal

Hello, Peter.

I do know that the Orion Expanse and Skywatcher Ultra Wide eyepieces are indeed "siblings" (same manufacture). The LER eyepieces do have a little more eye relief (20mm for all), but the 13-to-17mm provided by the various Expanse/Ultra Wide units is likely sufficient for most applications (i.e. viewing without glasses).

I haven't been lucky enough to try *either* design (same goes for the ED-2 line), but I would expect them all to provide nice, comfortable views with reasonably good fidelity. Yes, f/5 will challenge most any eyepiece off axis, but these particular lines should still do a good job axially (central 60%-75% of their fields).

I'll likely try one or two from the Expanse and ED-2 lines, myself. If I like them, I'll definitely come back to the forums and say so.

I'm sure several Astromarters will chime in and share their own experiences and impressions with the ED-2s, Expanses/Ultra Wides, and the LERs. In fact, you might end up with a LOT more feedback than you ever expected! :-) Just enjoy it.

Best wishes and luck.
-Dan

April 8, 2003 03:56 PM Forum: Astro Binoculars

Broadband coatings

Posted By Dan D DuBal

There are too many factors to consider; a simple/pat answer may not be available. Aspects such depositional sequence, coating composition, method of deposition, preparation of substrate, presence or absence of a hardcoat, hardcoat *placement* (whether as overcoat or undercoat) -- all these will factor into how "hard" and/or scratch-resistant a series of AR coatings is. Heck, even the scratching agent and its interaction with the coating(s) can make a difference.

My understanding is that a well-applied MgFl film coating is harder than typical glass. Most oxide-based clear hardcoats are about as hard as (often harder than) quartz. However, "hardness" does not always strictly equate to scratch/abrasion resistance and/or deflection resistance. There's also the question of whether or not a given sleek or scratch actually exists on/within the coating(s) or *under* the coating(s) -- on/within the glass itself. Yes, it *is* possible for hard-coated glass to be scratched "despite" the coating itself (which may remain undamaged).

"Significantly" easier to scratch than a good MgFl coat? or a Pentax SMC?
No, not as long as sufficient care is taken. Most cleaning methods recommended for astronomical mirrors and lenses are safe and gentle enough for any/all readily available AR coating(s).

For what it's worth: I'm no more or less concerned about the AR coatings on my Sino-made 15x70s than about the coatings on my Fujinon 10x70s. I treat them equally gently and carefully.

Best wishes.
-Dan

April 10, 2003 10:49 AM Forum: Equipment Talk

DS-60 focuser

Posted By Dan D DuBal

No personal experience (beyond just seeing a few), but I believe the drawtube itself is also plastic -- I may be wrong about that.

Not sure if that's a big deal (for $10, it may not concern you at all), but I thought I'd mention it.

Best of luck, and let us know how things go.
-Dan

April 11, 2003 01:30 PM Forum: Equipment Talk

I-M Alter 603 vs. MK67 Deluxe

Posted By Dan D DuBal

Did you mean the MK67 (Crayford)? or the MK66 (moving primary)?

Hmmmm...

If you meant the MK66, then...:

Pick the one you feel is more aesthetically attractive (if you have a preference).

Pick one based on the finderscope. The Intes includes an illuminator port. Not sure if the Alter does. Alter's may be worse, optically (but hey, it's a finder).

The Alter includes Vixen-Synta mount rail. MK66 does not.

The Alter also includes an 18mm Erfle, 0.6X reducer/corrector (or a 2.4X barlow -- not sure if this is a dealer-specified option, or who includes what), and a 2-inch star diagonal.

Flip a coin.

Optically? No discernible difference at the eyepiece, given equivalent correction.

Ignore the wall "baffles" in the Alter. They add no optical advantage.

If you meant the MK67, then...:

The Alter is more versatile -- much better able to accomodate astrophotograpy.

Hope I didn't confuse the issue! :-)

Best wishes.
-Dan

April 12, 2003 01:08 PM Forum: Eyepieces

Premium zoom, affordable price?

Posted By Dan D DuBal

Hi, Dan.

I recommend Allister's review of the Leica, Nikon, Vixen LV, and Orion zooms, on CloudyNights.com.

The Nikon has higher transmission, is reasonably priced, very lightweight (comparatively), and quite sharp. What little (if anything) the Leica gives up in bulk, price, high-mag sharpness, and transmission, it makes up for with regard to "ease" of view and viewing comfort (not necessarily eye relief).

The old Orion Ultrazoom (discontinued) *is* quite sharp on axis and has won many fans for its value ("tunnel"-ish 35-deg. views at 21mm notwithstanding). Afov expands quickly as it zooms in. If you can find one of these, it's likely going to cost much less than the Nikon.

Allister preferred the Nikon and the Leica, overall.

The Pentax zoom is supposed to be nice, as well, although I've heard no claims that it's superior to the Nikon, Leica, or the Ultrazoom. It's huge and waterproof.

Best wishes.
-Dan

April 12, 2003 01:14 PM Forum: Eyepieces

Premium zoom, affordable price?

Posted By Dan D DuBal

-By the way...

Even the best zoom should be considered a general-purpose eyepiece, best suited for its ~3x versatility and convenience. Don't expect them to perform on par with good Abbes, Plossls, Konigs, XLs, Radians, etc., at any given focal length.

Cheers.
-Dan

April 22, 2003 11:19 PM Forum: DVDs and Music and Books That You Recommend

Ramblings

Posted By Dan D DuBal

You bet I've seen "Gregory's Girl" -- though not *nearly* as often as "Local Hero," which remains my all-time, without-a-doubt, not-even-close, bestest favorite movie.

If you love "Local Hero," may I assume you've also seen Tornatore's "Cinema Paradiso?" If not, I highly recommend it.

I envy your visit to the Scottish village and can only hope that it lived up to your expectations. So, PLEASE don't spoil the fantasy -- if your visit was ho-hum, just keep it to yourself! :-)

Cheers.
-Dan

April 25, 2003 10:46 AM Forum: Equipment Talk

Barlow effect on focus

Posted By Dan D DuBal

Unless I'm mis-remembering...

Standard Barlows used directly ahead of (or "beneath") an eyepiece will require that eyepiece be drawn further inward (towards objective/primary).

When used ahead of *both* a diagonal *and* an eyepiece, focus will be drawn further outward (away from objective/primary).

--At least that's what happens with my Ultima :-)

Best wishes.
-Dan

May 5, 2003 07:59 AM Forum: Equipment Talk

Which is the best scope?

Posted By Dan D DuBal

Inge, it sounds as if you and I agree with regard to the telescopes you mentioned. I'm not sure how important nebulae and galaxies are to *you,* but I do know that my foremost/primary/favorite viewing targets are the planets and Luna. The "dim fuzzies" are very nice, and I enjoy viewing them through telescopes at every opportunity. However, I *could* refrain from doing so without much "astro withdrawl." :-) I don't believe I could say the same about the planets. They *are* the reason I participate in this crazy hobby.

I've never been very enthusiastic about the various JMI systems, but I well understand their appeal, and I respect their designs/engineering. As for the PortaBalls, I can easily see myself owning one in the future.

Best wishes.
-Dan

May 9, 2003 08:17 AM Forum: Equipment Talk

Info on an old telescope. Edmonton Scientific

Posted By Dan D DuBal

Vintage is early-mid '70s.
Looks to be in *excellent* condition.

Let's hope some readers out there have more info (and maybe some literature).

Dare I ask what you spent? :-)

Best wishes.
-Dan