Sorry, I was late Mr teacher !!
Thermal attributes
Function:
Spotter,
Dedicated Scope,
Clipon
And yes some are multi-function, but usually were intended to be one first. But a classification of a thermal could include more than one selection in the attribute
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Price Band:
Under $5000
$5000 to under $10k
$10k plus
The under $5k band basically includes all the non-USA made units, the entry level thermal units, the chinese units, Eastern european units, etc.
The $5k to $10k block is the "mid market" band and includes all the trijicons and n-vision units including mostly their used pricing, though used can dip down below $5k as well.
People get "dazzled" by the MSRP shown pricing. Street pricing is totally different. Get on the phone with 3 dealers and make them an offer and be prepared to walk away. My first rule of negotiation "You can't negotiate if you can't walk away". Don't get wedded to one dealer. Keep your options open. Talk to them on the phone. You will learn from all of them.
The $10k plus band is the military crap. Not for everyone, but I am amazed at how many people are in this band. I said I would never be in that band ... until I was ... I had to borrow from myself and pay it back, with wife looking over shoulder checking !!!
... but then I went there again. If you have a job and can prioritize, you can get in to the over $10k band. It took me 18 months to pay back that first loan.
But I think we only need three bands. That's my humble opinion ... and it seems to nicely divide the market also.
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FOV vs Magnification
These are essentially trade-offs within the same space ... its more of one and less of the other. Pick your poison.
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Ergpnomics - this might be like "how hard is it to change batts in the field?" ... could be subjective
user interface - this is like button layout, menu layout ... some of this could get pretty subjective
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Size
Weight
Lens size - we usually don't have this. If you try to measure it what are you measuring? Its probably best if we skip this attribute.
Focal length (most of the mm we see are actually focal length, not lens diameter, they are different) these can be recorded if known, though they are not always known, in which case they are NA.
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Video - some thermals are much better at supporting video than others
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Battery packs - I'm pretty much in the "change em in the field" camp, but others like battery packs. Does this thermal support several options for battery packs or 1 option or no options ?
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Image - oh boy ... this is the most subjective of all ... but some people make purchasing decisions soley on their perception of the image of a unit (based on videos made to selll produce or at least selected from groups of videos to pick the best ones) ... other make decisions based on price and image perception. As I tried to indicate in earlier post, image is a multi-determined attribute and elusive as well.
I have a UTC-x it has a great image ... BUT ... one night ... that image might be outstanding ... truely impressive ... the very next night ... in the same spot on my land .. .doing the same activity ... that image could SUCQUE ... this is the total truth.
If this gathering rates thermals on image ... it will be for one night ... in one spot ... looking in one direction ? I think it will be a random crap shoot. But this one should be called "subjective" for sure.
In my experience their are three factors that go into image
Conditions
Operator experience+experience with that unit
The unit itself
For the most part, I think conditions contribute the most and of course they are highly variable.
After that, I think operator experience contributes the most. When I first went out with thermal I sucqued at optimizing my image. Now, 7 years later, I am 5000% batter at it. I turn the knobs and push the buttons continuously all night long, optimizing that image.
Next, operator experience with the unit contributes a lot. A few units are pretty danged fancy ... with as many as 6 different knobs or buttons that control image ... the COTI and the A55 are examples of those. I stil don't feel like I've mastered those two. Whereas the bulk of thermals I do, the trijicons, well all the BAE coreed devices and the FLIR cored devices and the pulsars ... I feel solid on those.
And believe it or not, I think the unit itself contributes the least to the image I see at a given moment, looking in a given diretion. Yup, that's the truth folks !
We can record the sensor resolution and the display resolution ... these will definitely be objective factors.
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Manual focus ... I've had ATN ODIN and numerous Trijicons with fixed focus ... and they worked great ... the breach and COTI also have fixed focus. But given a choice, I'd rather have manual focus and would pay extra for it. But for those of you wanting the lowest possible cost units ... looking for units that have fixed focus, could be useful.
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Head mountable ... some spotters and even one clipon (the SNIPE) are head mountable. Some of us think this is a useful attribute.
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Reliable/Rugged
There might be some objective and subjective aspects to this. Like I just T&Es a thermion XP50 and it was flawless. Another guy got one right around the same time and it was broke out of the box.
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Support - can it be fixed quickly ?? Again, this will be mostly based on experience. I'd rate my experience with Trijicon CS as A+ and my experience with ATN CS as C-
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So I hope I only forgot about 20 other attributes, but here ^^ is a start on making an attribute list.
I think these attributes fall into two different categories
Data/Objective: Length and weight for instance, find the numbers and write them down.
Subjective/Opinion: Like image of course
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For the Data/objective factors, I think we would write our REQUIREMENTS around these factors.
Like I want a clipon with a 60mm focal length and a manual focus, in the $5k to $10k price range .. that supports at least 8x on the day scope. And is rugged and reliable. And has at least a 1024 display on the back. And can be repaired in the USA.
(note I don't require 640 on the sensor and this is because I don't think that is essential, especially for a clipon. This DISPLAY is king!)
And I want collimation, i.e. optical wedge/risley prism so if I mount within tolerance no adjustments allowed or required. IPX7+
that ^^ is one requirment.
The next
A head mounted thermal, under $5k ... basically "what the breach should have been" unit. Ideally manual focus, but if fixed focus, then fixed focus farther out than the breach. I could PID a yote at 500yds with the ODIN. Needs a battery pack option. IPX7+
So we aren't rating the thermals on these objective attributes, we make them part of our requirements. We "rate" on the subjective elements.
Typing too much, gotta get back to the day job !!