Yesterday in post 10 I told the topic starter, MattJ, that I would try to look at M13 and give an objective comparison, boy do I regret that. When it's said that a picture is worth a thousand words, boy does that ever apply to some things in trying to compare some viewing equipment.
MattJ referred to this comparison of Obsession telescopes, probably a good start on comparing those scopes, but probably not a good comparison for people, in general, because of seeing, alone. Last night was a real PITA in terms of the weather and getting a chance to view, and then the seeing was atrocious. Jupiter, for reference purposes, looked more like a dull star, still one of the brighter ones where I live, but not its usual bright self. Different locations and seeing make comparisons hard.
So I'll take back everything I said yesterday, well not everything, I'll boost that magnitude difference to 7 or 8, and drop the images look the same reference (I should add, I've seen clusters that look like those images, but M13 sure didn't last night). Please take the magnitude difference with a large grain of salt, but it's not exactly untrue.
Here's my dilemma with a valid magnitude quantification, I realized this almost immediately last night, and fortunately GlennLeDrew already spelled it out in post 23; it's the invisible versus the visible. Or, for me, can I get to an acceptable image from where I'd have no image or an image not worth looking at. If you click on the link and look at M13 in the available pictures, and looking at the typical 8" or the 12.5" Classic and looking at the very outer edge of those and picking the faintest star you can see, I couldn't see that.
With a regular EP in a 12", F/4.9 Newt, M13 showed up as nothing. It didn't take me long to realize that if I had a 24" scope I would still see basically nothing. 4 x 0 = 0. It would be basically nothing, an unacceptable image. With a PVS-7 there was an immediate acceptable image, but not as dense as any of the Obsession images. Then I got to thinking that those images are what you see under some nice conditions, if at all, and that they probably had some time exposure aspect to them, I don't know for sure.
Also, the NV is an EP, I can't just change magnification by changing my EP, I don't have any other NV of different native focal length. I should have just stuck with Ed(dgie) on "double the aperture" or anybody who said, "such comparisons are complicated." The problem with all such comparisons is that we'd have to be at the same place, at the same time, comparing as best we could.
Now, why did I say magnitude 7 or 8, or 9 for that matter. Because I went from basically no image to a quite acceptable image, I don't know how to rank that accept to say that 1 compared to 0 . . . It wasn't really zero, but if you were a person who lacked knowledge, or if I set the scope up and pointed it to M13 last night and said, "Look at that," the reply would have been "look at what." It was as asymptotic to zero as anything I've ever found (as a matter of fact just finding it was my major achievement of the night, I knew a zenith goto might be a problem).
But enough of trying to quantify magnitudinal differences. Here's what I know for sure. If I doubled my aperture and got four times as much light, it wouldn't hurt but it still wouldn't show as well as one $1200 or $1300 PVS-7. Eddgie put out an ad for a PVS-7, he mentioned that it can help with light pollution. I barely knew anything about NV, though I did have a Gen 1 (probably really a Gen -5) device, you couldn't tell if it was on or off. I researched for a few minutes and talked to Eddgie and researched for a few more minutes and then said I'll send you some money and you send me that PVS-7. It's worked out great.
I strongly recommend regular telescopes first (so that you have something to plug your NVD into, kidding). However, if you live in bad light pollution, then you have to try NV or imaging. They both have their good points and bad points, if you want to see things right away, then it's NV. Imaging and NV can both be expensive. I'd say you can get into imaging cheaper to start with, but it can easily climb to as much as NV, or more. NV, probably about $1500 for a decent start, and add a few filters. They can both be complex or intimidating to the uninitiated, but NV gets the clear nod for simplicity and directness. They can both have focusing problems, not exactly news with any telescope stuff. Etc.
The magnitudinal or other differences, maybe hard to quantify and spell out. The real difference, immediate and awesome.
Edited by outofsight, 26 May 2017 - 08:56 PM.