Collins Electro I3 Piece
Posted 01 February 2006 - 02:38 AM
Posted 01 February 2006 - 03:40 AM
I've had my I-3 (Gen-4) for about a year now. I use it with a Borg 101ED, a Borg 125ED (both at f6.4), and my 13" T-scope. I have not used it with filters (I have O-IIIs and UHCs), but never considered that they would add to my enjoyment with the I-3.
I have found using the I-3 to be simply breathtaking, especially here in Michigan where the skies are rarely perfect, and one needs to milk out the most of any semi-clear night. The I-3 lets me see much more, and much more clearly, than what my scope and eyepieces permit.
My simplest test has always been viewing M13 for resolution of the stars. I find that with my 101ED, on a good night with averted vision, I can make out many individual stars. With the I-3, I can "see" all the stars on any night with my 3" WO fefractor - clearly and without any effort. The views with the T-scope are truely unreal! The same goes for most any other object, especially M57. Although I cannot make out the extended detail of many galaxies, I find that I can much more easily spot them (seeing their core) with the I-3, than with averted vision in the T-scope.
In my experience, I have never found a reason to want to use a filter with the I-3, but I'm always open to suggestions.
Up in the clouds of Michigan for the past 4 months!
Posted 01 February 2006 - 08:01 PM
I can dream, can't I?
Has anybody had any experience in mounting an NVG to a scope, the way the military has done. The way to beat a Collins I3 is with a 3rd or 4th Gen night vision goggle attached to the scope, it would seem. I'm sure that somebody has tried it.
Can I attach my binovieweer to the Collins I3?
Posted 01 February 2006 - 10:16 PM
Phil, I think the whole point of the I 3 is to apply the most modern technology directly to our astro needs. The vast majority of night vision scopes and ALL of the cheap ones are using technology that is behind Collins by one or two generations. The current "thin film" technology will probably not be superceded for a long time, and I'm too old to wait for a price reduction. If it makes my little 85 refractor act like an eight or ten inch scope, all the better, because I just don't want to lug a big scope around any more.
In a way, I feel priveledged to even try this product since its cost is greater than the combined value of my scope and mount. I am glad, however, that Bill Collins gives 30 days to evaluate allowing a complete refund for returned products. He said during our conversation that he has not had one of the newest generation units returned. I anxiously await its arrival and my field tests.
Posted 01 February 2006 - 11:49 PM
the results of my experiments can be summarized by saying
pay attention to how much near infrared is passed (> 650
nm) if you want satisfactory enhancement. The I3 enhances
near infrared wavelengths 10,000x more than blue wavelengths.
Sodium (yellow) streetlights are a major source of light
pollution, and filtering them out with a deep red/infrared
pass filter (block <600 nm, pass >600 nm) will help contrast
a lot in the city or suburbs unless there's also a lot of
incandescent lights nearby (which emit broad spectrum light
pollution, especially (unfortunately for the I3) in the
infrared). A relatively inexpensive Meade red color #25A
filter (or better yet, a #29 or a #70 filter) works well.
So does a Meade O-III filter (but not a Lumicon O-III due
to its infrared blocking).
I have experimented with narrow-band interference filters
around the H-Alpha and near-IR wavelengths (656 nm +/- 40
nm, and 700 nm +/-80 nm) and found them lacking when used
with the I3. They cut too much of what meager light is
there to begin with in smaller scopes.
Posted 02 February 2006 - 02:32 AM
Posted 02 February 2006 - 02:26 PM
such is the mirror diagonal. If the coatings on the
diagonal are interference coatings (AP MaxBrght, TeleVue
EverBrite, or the like) the coatings effectively act as a
near-infrared filter. Above 700 nm these diagonals pass
almost no light so are inappropriate for I3 use.
Regular oxide-protected aluminum coated diagonals are
excellent infrared wavelength reflectors and should be the
type used with the I3 eyepiece.
Posted 02 February 2006 - 08:49 PM
Posted 03 February 2006 - 03:55 AM
When Gary first told me about the diagonals, I was in the same boat as you are. WO could not get me the info at that time (last spring). But Vic at Stellarvue, sent me info about his dialectric diagonal. It shows a very level light transmission curve up to 700, and I surmised that it very likely continued from there.
When I looked into this, Gary told me that: "I've heard that some dielectric diagonals block infrared transmission (i.e. they act as a filter). Just verify with Tim what the diagonal's reflectance graph by wavelength looks like. If it reflects well from 400nm to 900 nm you're good to go."
I hope this helps,
Posted 03 February 2006 - 05:33 AM
Al Nagler personally verified for me at NEAF last year that
TV's "Everbrite" dielectric (not their "regular" or "enhanced")
diagonal has a sharp drop-off above 700 nm, and that this
was characteristic of dielectric (interference) coatings
used on diagonal mirrors. You may want to push Vic a bit
harder to get the actual data above 700 nm.
GeezerGazer, any diagonal that is not described as
"dielectric" should be OK. "Enhanced" is OK if it's
enhanced by the type of overcoat on the aluminum.
AP's "Maxbright" is a dielectric and is not good for
Posted 03 February 2006 - 09:08 AM
You're probably right about the dielectrics. What I neglected to say to Geezer is that I've avoided the whole issue by using an inexpensive WO diagonal.
Posted 08 February 2006 - 12:31 AM
Thanks so much for this very specific info. Gary, you are right... I would never have considered my diagonal as a filtering device. Is there anything else I need to know about the I 3 before it arrives? I'm all ears... ah, eyes... you know what I mean!