Posts Made By: Thomas Dey

I just read Walter's experience there and can indeed see where it would perform nicely as a rich field. 7mm pupil at 12X mag would be very comfortable and not push the "diffraction limit" at all. I still have a finder made like that with a lens jammed in a PVC tube and an ancient Edmund's unmounted Kellner used at very low mag. It's one of the best finders I ever had! So try it to see if it's worth using! Tom Dey

Thanx to all for those product and technique tips! I've degreased and regreased all sorts of cold-weather gear over the years. It completely amazes me that so many precision devices from the factory use the crappiest lubricants imaginable! I recently got a new portable emergency generator. Very nice except near impossible to start in sub-zero weather...just when needed most! I had used the recommended SAE 10/30 motor oil. My neighbor (skilled auto mechanic) sighed and said to replace that crap with a good synthetic. Did that and it works fine now. My conclusion is that many gizmos are designed and built by people who NEVER lived in a cold climate. I once had a very nice Chevy Lumina. It was a great car EXCEPT the damned wipers would get completely encased in a giant icicle in that gutter at the bottom of the windshield. The retard engineer clearly lived in, oh, L.A. or some bastion of the differently-abled.

I worked Physiological Optics at the Boynton Center for Visual Science at the the U of Rochester, so am kind of into this stuff. I no longer remember the vergence specs for bono instruments, but it is pretty relaxed...which is to say that our eyes are fairly accommodating to merge LR images. Telescopic Binoculars or course suffer misalignments quite often --- especially the cheaper ones, which are notorious for poor as-delivered alignment and also tend to lose it easily. And with most binos, drop them and they can of course go way off. About the only ones that can take rough use are the mil-hardened ones, and even there, the USN "Opticalman" Billet guys were servicing them all the time. Your description is Exactly what misaligned binos would do - you accommodate but look away and now must readjust to direct view. So yours are marginal at best and really need servicing. BTW, everyone has some "natural prism" twixt their eyes - which means that All of us are straining just a bit to verge LR. This is quite normal unless it gets to be TOO much and then eye strain or inability to comfortably verge results. This is why binos are always aligned using a good collimator that is big enough to accommodate both objectives at the same time. We had a 29-inch collimator for that at work. Not a cheap Coulter mirror but a custom Ritchey that cost a cool Million! What I LOVE about my Zeiss binos is that the collimation on all of them is downright perfect! You should experience no eye strain using binos. SEND THEM BACK ASAP! Also worth getting your vergence checked by an optometrist - they might do it at no cost and tell you whether your eyes need some "prism." Tom Dey

Oh! A follow-up, Robert: The vergence coalignment requirement is Proportional to magnification! So 20x80s MUST be collimated 3 times as well as 7x50s. This really stresses the tolerances on Everything that effects collimation (that center hinge pin used for pupil separation, the alignment and stability of the prisms, etc.) and affects your discomfort! It's really asking a lot of the mechanicals that comprise the binos. that's why the big ones are so temperamental and why the super-high mag ones rely on user-adjustable vergence. The JMI reflective binos (from the 6 inchers to the huge 16-inchers) therefore do (indeed Must!) provide motorized adjustments. Whew! Tom Dey

Nuts, it's snowing here and getting late. Maybe tomorrow. I'll keep the scope and camera ready to use! Thanx for the tip! Tom Dey

Yeah, I see what you mean, their regular price is $3990 which would give $3591 at 10% discount. If they mistakenly keyed in $2990 it would show $2691 - so sure seems a slip-up. It's still a good deal at $3591 though! Rikki is going to get a lot of calls. They certainly can't sell it at $2691 without taking a big loss on every one! The 2691 would be the fair heavily uese price on Amart for a beat up one! Tom Dey

Interesting! I've used filters since before they were sold! (Worked at B&L as a coater operator starting in 1965 and was soon designing and making my own with their permission and blessing) Big perk was access to spectrophotometers of course so I could immediately measure what I had made and check the cut-on and cut-off as it varies with angle (and therefore F# feeding it!) The very NB filters tend to suffer if the feed is too "fast." I later measured a bunch of commercial astro filters, mirror coatings and Star Diagonals; found some terrible leamons among them - see attached images of pages 1 and 32 from my Y2012 report on Star Diags. P1 is the intro and p32 is the tech summary. If Astromart would like the whole thing to put in Reviews or whatever...I'd be happy to oblige. These and many other papers are unpublished and entirely my own work. I also have a comparable paper where I measured spectral throughputs of commercial eyepieces and found coating problems with some. Tom Dey

Here is the image of the summary page. Tom Dey

Cary at Optic Wave Laboratories (http://www.opticwavelabs.com) does superior enhanced coatings and often has bargain price sales. He also refigures mirrors quickly and does free testing. He did two 16-inchers for me, including refiguring one. Fast service and friendly! For BIG mirrors, Evaporated Metal Films (www.emf-corp.com) does a fine job. I visited their shop and they put enhanced Al on my 29-inch and may do my 36 later. I just got 1st (actually 2nd) light on my 29 and it is spectacular! M51 as a BLATANT field-filling pinwheel staring straight at it! I did coatings years ago so have a lot of respect for these guys... Tom Dey

I think the responders didn't quite catch what you said here. The LASER COLLIMATOR would indeed give a faux return from a specular back side. We experience that sort of thing all the time when doing pre-alignments of the Spatial filters for Interferometry in Aerospace applications. And some of those mirrors are SO precise (front AND back) that an in-process uncoated optic will give one or more false signatures. One easy trick is to just wet or even breathe on the back side...then its false signature will be the one to momentarily disappear. Nother trick is to put peelable "strip-coat" on the back, which elims it's faux return. yet another (that we used in production on thousands of parts) get giant sheets of High Contrast Sterolith Film, expose to light, process to opaque black, wet in soapy water and adhere it to the back of an in-process test mirror. The wet gelatin index matches AND adheres to the back, rendering it absentee for short duration of the test. Peel off and use on the next part. A few such films will last a whole shift (hundreds of tests). Use another the next shift. We tested tens of thousands of mirrors this way and it greatly reduced cost. We had previously been spray painting the backs black for testing and then stripping the paint later before coming up with that! The Test Set was of course fully-automated for so many parts, so we couldn't screw around too much or take too long. Like I said - your responders seem to have missed your comment regarding the "laser collimator." Anyone reading this---if you want a REAL challenge...ponder trying to align and then USE a multi-arm white-light interferometer! The coherence length is fractional wave over arms that are feet (or miles) long! PS - we STILL haven't detected Gravity Waves...sigh! Tom Dey – optomanic Tom