Posts Made By: Ron Harper

Since I only saw it once for sure, I cannot answer your question. But, my one time was through a 12x80 finder scope. The 20" dob it was riding on failed to show it. You've got to get WAY out in the country for this one!
Ron

Bill,
Oh dear me, I would personally NEVER have removed an objective from a scope, taken it apart, touched a surface of glass with any chemical, much less RUBBED it with KIMWIPES(I think I'm going to faint here), nor attempted reassambly nor collimation.

Seriously, sometimes scopesmanship takes gumption. Pretty often in fact, for me. I applaud all you did. The lens, though prized, is the toughest part of the scope!

I live in New Mexico. Could my lens get dehydrated?
Ron

If all the coating on that surface was gone, you'd probably suffer a loss of 4% of total light throughput. If you removed 0.01% of it, which would be very obvious and ugly looking, you'd loose 3%x.01%=.0004% of throughput, not measurable, much less noticeable. The outer surface is the most benign place to increase reflection, since the reflected light goes back out into the universe, instead of bouncing around in the scope eventually to your eye. 80mm f/5 scopes are so much fun! My bro-in-law has one. We put a 22 Panoptic on it and have a ball, the images are just about perfect!
Ron

Inge,
Thanks for the reminder of details that can be seen in these objects. They really are varied and interesting. Some fit more than one category almost equally well. In fact your scheme could provide grounds for endless arguments! But, thinking about these categories as I observe will add to the fun.

Planetaries are good deep-sky targets for a large scope in town, because they take magnification and resist light pollution quite well, and don't require excellent seeing to look good. I have not observed them much for a while, and will drag my 14-inch dob out on the next nice night.

The death of a star. I can't help but wonder if there were planets, perhaps life.
Ron

Inge,
If the trip to the Canary islands will be made on a regular basis, there's a way that would save a lot of trouble, cost less than high technology, and probably result in a better telescope. But, it entails risks, and sacrifices of some of your personal control of matters.

Have Tscopes build a structure for your mirror, and ship it to where you stay. That would cost about $1500 I guess. Then, just take the mirror back and forth when you travel. This would require a little help from the innkeeper, but if you're a regular customer he would probably store it for you. It wouldn't take up much more space than a lawn mower. It would be good collateral for him, in fact.
Ron

Gerry,
Truss. My experience is with 6" tube, 10" truss, 14" tube, and 20" truss, and I see the difference. None of my scopes is fan-ventilated, and fans might diminish the difference. But it looks to me like whether you let the warm air coming off the mirror escape naturally or help it along with fans, tubes are at a disadvantage, because they tend to trap it.
Ron

Steven,
A firm answer is impossible without knowing your scope's geometry, that's why you need to do the ray tracing yourself. But my experience may shed a little light.

I converted my 6" f/8 to 2" eyepieces a few years ago. I wanted to keep the diagonal as small as possible, so I used the lowest-profile focuser I could find, which turned out to be a helical model, and inched the focuser as far from the primary as possible so the eyepieces would just reach focus at the lowest setting. Just for kicks, I tried my original 1.25" diagonal, and obviously no way it was big enough, since the field with a 46mm field stop 2" eyepiece was basically plumb dark.

I then followed the recommendation that 70% illumination at the edge of your widest field was a good thing to shoot for, used web software, "Newt" I believe, which came up with a 1.6" diagonal. I ordered and installed it and am mostly satisfied.

Under a dark sky, vignetting isn't noticeable. You're looking in the middle, and wouldn't know it if a star on the edge was dimmed slightly. But, under a bright sky, with the 5mm exit pupil provided by this 40mm eyepiece, there is no escaping seeing that the skyglow is dimmer at the edge of the field. This is a little bit disturbing.

So 70% is fine for dark sky, but you might want to aim for something like 85 or 90% if your sky is always bright and you think this effect would bother you.
Ron

When I first got my scope, there were a couple of weeks before I got a diagonal, and I observed straight-through. I finally made up my mind which diagonal to buy, and figured when it arrived I'd have a big shoot-out and see what these Japanese guys were up to. Never happened. I slipped it in, said "good grief" in relief, and never looked back! For what it's worth, I saw no difference. The neck bone connected to the, eye bone.
Ron

Baker Marine and Captain's Nautical are authorized Fujinon repair services, and might could help you out, too.
Ron

Herbert,
I am right by you on this smokin' object! I live at 36 deg north at 7000 feet, and can see down that way fairly well. Not long ago I went to a place with a good southern horizon and explored this area. I'd sit in a lawn chair with a 10x50 binocular, and when I thought I saw something, check it out in my 6-inch Newtonian set up. Then I'd check the chart to see what it was. Some fun, huh?

The find of the night was 2477. A bright circular blur in the binocular, and the near twin of M37 in the scope. It even contained the curiously common bright red member. I also noticed curving dark lanes, sort of like in 7789.

Tonight I discovered to my delight that I can see it from my backyard, and that with a mere 16x70 binocular, I can glimpse sparkly things in there with averted vision.

But, a question. I've seen this listed as both a globular and an open. It's pretty much round, I guess, but looks open to me. Do you know for sure it's "open"? I guess a smart astronomer with a Hertzsprung-Russell diagram of the stars could make the scientific decision.
Thanks,
Ron