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Posts Made By: Ron Oehlert

June 15, 2015 09:17 AM Forum: Reflectors

Restoring a Criterion RV-6

Posted By Ron Oehlert

You remove the drive housing cover and then loosen the three spring-loaded clutch plate pressure screws until RA axis rotates freely. Then adjust balance weight(s). Once balanced, re-tighten the pressure adjust screws such that tube may be hand-slewed but drive tracks correctly (too loose can allow drive slippage in use with mis-tracking a result). Once clutch friction is set to your satisfaction under the stars (trial over several nights; temperature can affect final preference), replace cover. BTW, I have a 6" f/9.3 Criterion Deluxe Observatory Dynascope and an 8" f/7 Criterion RV-8. Also, the same technique applies to vintage Meade, Cave, Parks, etc drives with enclosed clutches.

June 28, 2015 10:09 PM Forum: Sports

US Open Coverage On Fox

Posted By Ron Oehlert

You sit and WATCH golf tournaments on TV? I can't even get excited about playing golf (which I have when younger), would rather be bored at the Ballpark where I can at least enjoy a Beer and Hotdog during the event, heh. BTW, my 96 year old Mother watches golf on TV, so I can appreciate the affliction even if I don't understand it. Per Fox's sports coverage, their Baseball coverage also is poor compared to the others; alas they are the telecaster for the local team.

July 2, 2015 10:01 PM Forum: Telescope Making

Aperture Fever

Posted By Ron Oehlert

Per the biggest scope you presently have, my later-production Meade 10" Starfinder came with a 2.3" diagonal which effectively made it a 9" f/5 with the focal plane 10" (edit: this should be 11" distance rather than 10") from the secondary as it was set-up. A 2.6" diagonal is the minimum size necessary with such a set-up (a 2.6" diagonal was in in the original early 1990's 10" Starfinders) so I replaced the stock diagonal with same; the 2.6" here provides full illumination on-axis with an unnoticeable 1/2 magnitude fall-off at the very edge of a low-power 2" barrel eyepiece or corners of full-frame 35mm film. A larger diagonal in this case wouldn't really benefit light-wise photographically or visually, but would detrimentally increase the central obstruction for planetary or Lunar observing (high-resolution planetary viewing really demands a tracking mount or platform). While my scope's original Meade mirror had a good figure with slight astigmatism and performed well, it now has a Swayze-figured primary and Antares 1/30th wave 2.6" secondary; that extra light in the airy disk really shines on all objects, making faint deep-sky clearer as well. I've self-made several mirrors in the past and suggest your 10" would be a good starter size; perhaps eventually re-figure it yourself if a re-figure is warranted after star-testing when it returns from the coater. The grinding is not that skill-demanding (just lot of work) but figuring a really large mirror I do not recommend for the very first attempt. And BTW, any mirror 6" or larger gathers plenty of light un-coated for night-time Star-testing or even viewing the Moon and Saturn to check it's figure before coating, likewise for mirrors with deteriorated coatings.

July 3, 2015 10:49 AM Forum: CCD Imaging and Processing/Solar System

Six planets

Posted By Ron Oehlert

Neptune, Jupiter and Mars are excellent!

July 3, 2015 03:38 PM Forum: Beginning Astronomy?

Way Overboard... and tackled everything wrong.

Posted By Ron Oehlert

Hello Matthew, I've been a contributing member of the ALPO (Association of Lunar and Planetary Observers) and also enjoy the Deep Sky. For me a 6" f/8 reflector was my primary instrument for years while I raised three sons and today I enjoy the views thru 10" f/4.5 or 8" f/7 reflectors, either of which would also have served splendidly in place of the 6". Aperture rules where high-resolution planetary or lunar viewing is desired as well as Deep-Sky; bigger gives brighter, higher contrast and greater resolution regardless of the target (except the daytime sky turbulence allows no real benefit to aperture for solar observing). A driven & steady mount which holds the image centered is almost mandatory for the planets if you want to glimpse their fine surface detail and also is nice for powers over 100X on Deep-Sky. So for your next instrument, consider a larger reflector in the 6 to 10" range; 6" f/8, 8" f/6 or 10" f/4.5 are about equally portable in that they easily fit into most vehicles and are not un-manageable per weight. I easily carried my 6" German equatorial on my hip out the door and around the yard.

July 27, 2015 08:24 AM Forum: Eyepieces

Vernonscope Zoom 15X-50X Eyepiece

Posted By Ron Oehlert

Why not give Don a phone call (he answers)? Likely it was a short-offering import like their 20mm and 32mm wide angles of the 1980's. My own set includes the screw-can Brandons, 2X & 3X canned Dakin Barlows, both the above-mentioned wide angles and a 1/2" fl Vernonscope Erfle in the Vernonscope laminated formica case from the 60's-70's.

January 29, 2017 08:38 PM Forum: Equipment Talk

Coulter Odyssey 10.1" modifications

Posted By Ron Oehlert

Hi, I have what started out as a 10" f/4.5 Meade Starfinder from the 1990's. About the only thing left of the original scope today is the tube and mirror mounts, but the original mirror (now re-figured) beat the planetary views of a perfect-optics 8" f/7 Cave Astrola side-by-side on more than one night despite suffering from astigmatism originally (so my mirror was not great, either). The greater Aperture trumped the better yet smaller Cave, so you can get more out of your scope with the mirror it has. A Barlow or Tele-negative lens (different words for the same thing) should be used with a good eyepiece if the best planetary or lunar high-power views are desired, because using a Barlow with a fast focal-ratio Newtonian-design mirror like yours and mine flattens the field and narrows the light cone, similar to a Cassegrain design (which are fabled as planetary-purposed scopes). Since a Barlow doubles (or triples) the magnification of any eyepiece used alone, a useful medium-power eyepiece can then also provide higher power when used with the Barlow. Accurate focus at the fast focal-ratio or your or my scope is critical with no real lee-way outside of that, so a good focuser is vital for glimpsing fine planetary or lunar detail, and such ability also improves deep-sky views especially when higher power is used on objects like globular clusters or planetary nebulae. I use a vintage Sky-micro 2" helical/rack & pinion which allows coarse and fine adjustments. Any modern unit that provides for fine adjustment will do what you want; an ordinary rack & pinion focuser can prove frustrating attempting to fine-adjust such unit via their relatively coarse gearing. A helical or rotating thread focuser allows such fine movement and so helical 2" to 1.25" adapters used with a coarse 2" focuser are also excellent for your need. You will want a 2" barrel 32mm focal length eyepiece for the widest-field views of the stars & Milky Way fields and perhaps a 20mm or 16mm wide-field eyepiece for Deep-Sky too plus a 12mm or 10mm and a Barlow for higher power planetary and lunar scrutiny. If your local Seeing conditions permit greater magnification, then condider shorter focal length eyepieces. My own local Seeing rarely allows greater than 200X or so on the planets or Moon regardless of whether a 6" f/8, 8" f/7 or 10" f/4.5 s used. Changing the focuser involves drilling mounting holes for the new focuser and maybe enlarging the focuser hole in the tube to accommodate the new focuser; easy to do with the cardboard tube you (and I) have (BTW, that cardboard tube does not introduce air currents due to it's insulating ability, so is better than you might imagine). Also measure focuser height to ensure the new unit will reach focus; if necessary to accommodate a new focuser, the easiest method is to re-position the mirror up (or down)the tube to move the focal plane if necessary. Just drill new holes for the mirror mount in the appropriate place. Used focusers from the classifieds are the least cost.