Posts Made By: Ron Oehlert

It won't get any older really, maybe by just a moment is all. Couldn't resist- why don't you just try it since you already have it. Ron

Any Barlow is simply a negative focal length lens, named after the Englishman that 1st proposed using as such centurys ago. The Further the lens is from the eyepiece or imaging chip, the greater the magnification factor. This occurs due to the Barlow lens effectively changing the objectives' focal length into an apparently much longer focal length. The new focus point will vary somewhat depending on the barlow-to-imaging chip (or eyepiece) dimension.

Refractor or reflector objective lens makes no matter to the Barlow. Apply same as you did before. Whether 2X, 2.5X or 3X is selected kinda depends on your eyepiece collection & the multiplications vs duplications a Barlow yields & what you want. Example: if you had 25mm & 12.5mm eyepieces, a 2X Barlow only provides one additional magnification (25mm plus 2X Barlow = 12.5mm or a duplication of existing eyepiece) while a 3X Barlow with those same eyepieces allows two different additional magnifications (25mm & 12.5mm with 3X Barlow = 8.3mm & 4.1mm).

You do not need them. If you were observing Jupiter you should easily be able to discern when a feature was on the planets' Central Meridian (midway across planets' disc) & so likewise you should easily be able to discern where the center of your field of view IS without use of crosshairs; slight de-centering is obvious. A low-power eyepiece in the main telescope will then enable centering its' view for more powerful eyepieces in turn. I find crosshairs distracting & I've not used crosshairs in my finders for over half a Century with no aiming slowdown or inaccuracy whatsoever.

Jupiter is not well-placed now for good viewing (too low to the horizon = shimering images = loss of detail). But Jupiter IS the largest planet yet is still small in a telescope view due to the very great distance (always). Over time, repeated viewing under good seeing conditions (a steady atmoshere) will train the eye-brain to see finer detail in these small objects. Only the Moon will present a big picture in a telescope, but the Moon as viewed with the un-aided eye presents similar to the best telescopic views of planets & as such can be used as a trainng aid for seeing greater planetary detail. IOW repeated viewing of the Moon without telescopic aid shows more detail than the 1st such glance & the same holds true for telescopic planetary viewing. Plus for each moment of steady viewing during a session, your brain will remember what it saw so the next steady moment affords slightly more detail to be observed; continued watching reveals more detail over time altho those moments of good seeing may be fleeting. Jupiter was better-placed for viewing last Fall & will be so-placed again next Summer. However, Mars is right now coming into its' best viewing since 2 years ago & in another month or so will again become too small for another 2 years, so concentrate on Mars now & practice that eye-brain recognition of detail in small objects (& Mars will be at best 1/3rd the diameter of Jupiter = smaller still in a telescope regardless of magnification). By Spring, Saturn will replace Mars as the planet to watch with Jupiter again sharing observing during the Summer. The magnifications you now have are ample & even sometimes too much for most Atmosheric *Seeing*. Yet as mentioned, a 12mm with the Barlow would fill the gaps in power you now have plus a 25mm to 30mm would provide good deep space views of star clusters & finally a 20mm to fill in the gap between the 25 & your 15mm for increased magnification of Deep Sky objects. In the past, the 20mm focal length eyepiece was often a Wide-Field type with the remainder of the set similar to your plossls & such a set would serve you well. Then you'll likely find that your 9mm, Barlowed or not, is rarely used but nice to have on those RARE nights of excellent *Seeing*. With a similar focal length telescope as yours, a 20mm eyepiece & 2.4X Barlow are my most-used magnifications & Always what is in the scope to begin with, until I see what the night's Seeing might permit.

My venerable Edmund mount & syncronus clock drive have exhibited no problems in near zero temps for either visual or long-exposure film photography. My problem was eyelids sticking to eyepieces. However, if you are worried, simply do not plug in the drive & use Manual tracking instead; simply nudge the scope when object moves to edge of view for another pass = very convenient up to 200X. The Edmund drive clutch is a piece of leather between aluminum & brass plates, tension is easily adjusted via thumb screws & rarely requires re-adjustment regardless of Season, drive gears are brass gear & steel worm lubricated with ordinary Household 3&1 oil. Scope is a 6" f/8.

You have just discovered what Auctions are for; to allow the Market to set price.

For my planetary preferances, none has enough aperture.

I used to, as a former active member of the ALPO (Association of Lunar & Planetary Observers) I was a contributor to the Luna Incognita Project of the 1980's that helped map the Moons' South Pole Region & thus completed mapping of the Moon. An area about the size of Colorado that had insufficent photography during the Apollo missions due to not being sun-lit, nor had been previously visible from the Earth since Galileos' time due to cyclic librations, finally presented itself for occasional viewing. For several years I contributed detailed drawings & high-resoluton film photographs while concentrating on the regions least observed due to pre-dawn time windows & low Winter temperatures & had my work published in the ALPOs' quarterly Journal for distribution to professional Astronomers worldwide. This was the region NASA has more recently sent missions to for water-ice exploration (vital to any future manned lunar base station). My fellow Amateurs' efforts in mapping the last uncharted region of the Moon was a cover-story feature in Sky & Telescopes' 50th Aniversary issue of November, 1991. I'm very proud of this accomplishment. Even today, backyard Amateur contributors to ALPO are a mainstay in on-going planetary research & monitoring.

Since no one has replied, I'd say they are fine if the light is On. They are Not hand-warmers. I've no experinece with the Kendrick, but years ago S&T had DIY Dew Removal construction articles using small electronics resistors (such as available from Radio Shack) wired in a series string & placed around objectives or eyepieces; battery powered. Those small resistors cannot withstand any heat you could actually feel without failing. The purpose of dew removal systems is to maintain ambient temperature, not actually heat up the optics (that would create distorted images due to convection currents on the optical surface; which is why reflector owners use fans). Only surfaces Colder than the surrounding air will cause dew formation & that is what dew heaters are supposed to avoid instead of warming sufaces up higher than ambient temps. So, rather than feel them with your hands, observe if dew is forming or not to evaluate their effectiveness.