Posts Made By: Dan D DuBal

Don't forget to simply look (naked-eye), too.

Their aspects won't be very favorable, as these beauties will be hugging the south horizon, but you should spend some time with them -- perhaps with binoculars, as well as your unaided eyes:
Rigil Kentaurus and Hadar
Crux (upper reaches, including the Jewel Box)
NGC 3372 (Eta Carina nebula -- very early evening, if at all).

When I first noticed these southern wonders (in my youth, from extreme south Texas), I had a great appreciation for just "how far south" I was seeing. Even though their extremely low altitude diminished their splendor, the experience "tweaked" my celestial perspective.

Best wishes, Inge. You have several months now to become more and more anxious about your trip to Las Islas Canarias. 8)

Cheers.
-Dan

Jeff, considering your modest & humble telescope (Newtonian, yes?), that's an excellent image! North Polar blue haze, SPC, Hellas, Argyre -- lots of info there. Was this around 2:30am local time?

Dare I ask: can you give us a little more info about the mount itself? -Got a hunch that I'm going to be even more impressed after you tell us.

Thanks for sharing!
Cheers & best wishes.
-Dan

Very nice image, Peter -- even if it is your nemesis.

My most impressive view of the Zodiacal light was during the "other side of the calendar" (Spring) in 1998, during an astronomy/camping trip just west of the Canyonlands. The "cone" stretched up to ~45 degs. altitude, and the Pleiades seemed to be sitting on top of its "peak" (the Seven Sisters stranded atop a sandstone spire?). The Zodiacal Light was stunning and obvious even before the end of evening twilight.

My best view of the Light during Autumn was during an all-night road trip to Ft. Davis, Texas. Somewhere in central New Mexico, coincidentally (north of Roswell on US 285), I noticed a glow rising from the eastern horizon. Since it was far too early to be morning twilight, and since there were no size-able towns to my east, I was momentarily confused. Took me a couple seconds to realize what it was, as I'd been so used to seeing it's western/springtime apparition.

Thanks for sharing.
Cheers and best wishes.
-Dan

While coma is certainly at work here, astigmatism is likely overwhelming the patient's 14mm Epic cohort. The appearance of peripheral minimal-blur ("best focus") astigmatic star images is also conic or "comet shaped," albeit a more "spiked" or tuft-like flare (rather than the conic "smear" of coma). Here's an interactivity test which should demonstrate the presence of astigmatism in the 14mm cohort...

By alternately positioning the two playmates closer together and further apart (either side of their optimal play separtation), you should be able to more clearly observe the Epic's astigmatism. Resulting star images will alternately "squint" along perpendicular axes, on either side of that optimal play separation. If coma were the only condition (i.e. Epic not infected with astigmatism), this same test would show no evidence of the 90-deg. alternating squint distortion.

Your suspicion regarding comatic &/or astigmatic star images being more visible in the shorter cohorts (e.g. 14mm versus 22mm) is correct: you were likely seeing the affects of higher magnification of the distorted Airy disc.

The Radians' physical makeup prevents their being similarly affected by astigmatism, particularly within their torsos (relative to comparable Epics). This is simply a function of genetics. Astigmatism remains evident and visible, however, in the Radians' extremities.

The stronger appearance of the 14mm Epic's astigmatism (i.e. more advanced or widely spread than in its 28mm sibling) is a direct result of the patient Astroscan's inherent f/4.2 condition. Introducing the Barlow significantly modifies that inherent condition (effectively changing it to f/8.4). As such, the sibling 28mm Epic becomes more compatible, and the appearance of astigmatism is reduced. In other words, you changed the Astroscan -- not the 28mm Epic (hence the much-smaller degree of observed astigmatism seen in the 28mm sibling).

As for poor seeing conditions (much stronger dynamic distortions and defocus), they will not exacerbate the appearance of coma or astigmatism. Rather, said distortions will likely overwhelm and obliterate the appearance of comatic &/or astigmatic conditions.

Although the 14mm Epic's condition in incurable, it is stable and will not worsen. So long as he and the Astroscan get along (at least to your own eye), there's no reason they shouldn't continue to play together for the rest of their lives.

Cheers & best wishes.
-Dan

Hello, Malcolm.
When I chose my MK67, some years ago, one key reason was its design -- compact and relatively lightweight for its aperture. Another key aspect was its much-lower cost, relative to 4-inch apochromats. In terms of optical/visual advantages over such apochromats, the MK67's are admittedly subtle &/or minor (e.g. angular resolution). In other words, an MK67 or MK66 will not demonstrate a great and easily-visible advantage over a 4-inch apochromat. The apochromat's own advantages involve low-level contrast and hue saturation. Relative to a typical 4-inch achromat, the MK67's advantages are a little more obvious: no chromatic aberration, likely better optics, angular resolution). I consider my MK67 a viable "substitute" for a 4-inch f/12 apochromat.

One important consideration, of course, involves thermal conditions. Sharply falling temperatures will prove more problematic for a close-tube cassegrain. Likewise, a 150mm Maksutov will require more time for ambient cooling of its mass -- particularly its primary mirror and the secondary baffle tube). I'm sure you're aware of this, but I thought I'd mention it nonetheless.

Obviously, the advantage in bulk/weight is significant. In this regard, a new MK67 or MK66 may be a great alternative. (Incidentally, I'd likely choose the MK66 over the MK67, due to its more-versatile focuser mechanism. The MK67 is not as compatible with binocular viewers.) If, however, you're quite interested in a more significant optical advantage (one which is more readily visible at the eyepiece), a larger cassegrain may be a better choice -- either a 7-inch Maksutov or perhaps even a Celestron 9.25 optical tube assembly. A new 7-inch Mirage or Intes Micro is certainly more expensive (& bulkier/heavier) than an MK67 or MK66. The same applies to the C9.25. However, the additional aperture is certainly an advantage when conditions allow (good seeing). Excellent second-hand samples of 7-inch Maksutovs or Celestron 9.25s may indeed fall within your budget. Alternatively, you might consider a new 9.25/CG5 combination and perhaps offset some of the expense by selling one of the mounts.

Nutshell:
If the choice and budget were mine, I would try to find a second-hand 7-inch Mirage or Intes Micro, or a Celestron 9.25. If that search proved fruitless, I'd likely choose the MK67 or perhaps the Intes Micro MN56 (Maksutov-Newtonian). While not a large leap forward in aperture and visual impact, either Russian Mak would certainly please your eye when viewing the planets. In either case, the EQ3 would definitely manage the MK67 or MN56 with greater ease.

Cheers & best wishes.
-Dan

It is unlikely that an annual subscription to "Sky & Telescope" will be found for less than the publisher's rate of $42.95/year. Readership is very small, compared to typical newsstand magazines. Most newsstand magazines rely on many more advertisers who generate advertising revenue per issue. As such, the cover prices and subscription rates for those magazines are less important to their publishers' overall revenue. Significant rate discounts for most high-volume periodicals are not only widespread, but they are the norm.

If your budget allows, I recommend the 2-year or 3-year subscription rates for S&T. According to my recent renewal notice, the 2-year rate is $79.95, and the 3-year rate is $109.95.

Cheers & best wishes.
-Dan

Holy cripes!

THIS is one of your first attempts...?

I'm not easily boggled, Bart. However, you have indeed dropped my jaw.

OUTSTANDING work!

Cheers, best wishes, and don't you dare stop imaging.
-Dan

Great work, Zack. Don't you dare stop sketching!

I'm sure I speak for lots of other Astromarteers: we look forward to seeing many more sketches.

Cheers and best wishes.
-Dan

Ditto Steve.

The Baader, A-P, & Tele Vue dielectric-reflective diagonals' surfaces are extrememly hard & durable, and their reflectivity will not degrade via long-term oxidation. In my opinion, their higher costs should be considered more within that context, rather than any potential advantages regarding reflectivity &/or scatter at the wavefront. Premium prism diagonals should not be disregarded, either, but they are comparably expensive and not as versatile (not the best choice for fast scopes, due to potential chroma; plus they induce some spherical aberration as well).

Cheers & best wishes.
-Dan

I'm not aware of any right-angle RA-axis borescopes for polar alignment, but I wouldn't be surprised if there were a few made (perhaps for high-end &/or custom equatorial mounts). RA bore diameter and borescope aperture would be key factors. A relay lens or group might also be advantageous (again, depending on mount and scope dimensions/parameters).

Vixen's 8x50 right-angle "Polaris" finderscope -- found on older Celestron Ultima SCTs and also available as an accessory -- included a polar alignment reticle and illuminator. I believe it's now extinct. There may have been a few other finderscopes which utilized polar-alignment reticles, as well, but I don't recall any.

Cheers & best wishes.
-Dan