Posts Made By: Hinrich Eylers

Nevermind the 11mm exit pupil, ideal for 8-year olds

I just had a reason to see my Celestron's base openened at my dealer's (not their fault, mine) and there also saw a corresponding Meade ... let's just say I am even more glad now that I have a NexStar GPS, not a LX200GPS. Before that, I was already extremely happy with the optical and mechanical performance. Plus, make sure you carry either scope a few feet before you buy it!

Also, go look in the respecive Yahoo groups what people are complaining about.

http://groups.yahoo.com/group/NexStarGPS/messages
http://groups.yahoo.com/group/LX200GPS/messages

I would get two batteries - one 10 Ah or better to power only the scope ... Nexstars are sensitive to voltage fluctuations and turning other equipment on and off isn't going to help that. I have a 7Ah for a NX11, and it just barely doesn't last the whole night dusk to dawn ... so that's why 10Ah or better

And, one bigger one (like the 19Ah or even more) to run the laptop and dew heater and whatever else off. This one is nice with more than one plugin. A 19Ah will run just a laptop about 8 to 10 hours.

If one of those batteries has lights and other gizmos, that's nice but not necessary. Both of my batteries are jump-start packs containing sealed lead acid batteries and do have lights, and I usually use the red light to clean up. I doubt I'll ever use them to jump my car though

Forgot one (this ought to be good too):
Myth: Red light is best to preserve night vision.
Reality (I shouldn't have called it Truth): Light intensity is more important than color. Thus, the best light to use is *green*, because a much lower light intensity can be used to still be able to see.

http://lvaas.org/flashlight.html (RED IS DEAD... GREEN IS KEEN)
http://www.corvus.com/kniffen.htm
http://www.flashlightavenue.com/colorguide.html (now there's a scientific source )
but, arguing for red,
http://www.aoa.org/clincare/aviation-night.asp saying that exactly because the eye is so insensitive to red, red doesn't even stimulate the scotopic vision (but goes straight to photopic system (cones)).

Honestly, this one I'm not sure about. Did anyone experiment with this (i.e., didn't just always use red because that's what everyone else doesn?)

Technically (per Zeiss, but I'm sure there's slightly other definitions out there), an achrochromat corrects chromatic aberration such that two colors concide in the focal plane with the effect that the other colors aren't that far off any more. How far depends on the scope; a good achromat can show very little color already in the main part of the spectrum, but at the extremes it's very hard to get close - thus the violet hues in achromats.
The apochromat corrects the chromatic deviations from the ideal image plane (the secondary spectrum) to the extent that "overall image quality is no longer limited by the secondary spectrum," i.e., the lens is nearly ideally color corrected (whatever that means). *In practice* that usually means that the lens is corrected for three colors, although that doesn't necessarily have to be true - an excellent achromat could, by that technical definition, be called an apochromat, and could possibly require only two lenses (I guess that's what they sometimes call semi-apo?). Then again, some apos are four-lensers.
Using excellent glass (like ED) or multiple lenses doesn't necessarily qualify a lens as apo, and possibly not even as achromat if badly enough designed .. And, technically no refractor can ever be completely free of chromatic aberrations (unless it had an infinite number of lenses), although obviously the definition of an aop means that they are negligible as they should be ..

That all said, there's hardly a way to spend more $$ per aperture than on an apochromatic refractor - the reason being that them chromatic aberrations are just a bummer to get a handle on especially once you get past a few inches aperture and to make an apo, you need to get (maybe) four, (usually) six, or (sometimes) eight generally full-aperture diameter glass surfaces near-perfectly right.

Anyways, the APO crowd I'm sure will agree (even with me ) that the intended primary application of an apo is high magnification viewing of brighter solar system objects, which is where you really can reall tell the difference between apo and achromat. Maybe double stars, too, but I'd argue it doesn't matter that much there. For what you want to do - quick grab and go, widefield viewing, prime focus photography - I would say a good achromat like the AT1010 will do practically as nice a job, for a lot less money. And if you want really good planetary views - well, you already have a big dob

I use a ST80 (much cheaper than a 1010 in all aspects) for just that purpose, and if I stay away from the Moon, Jupiter, Saturn, Venus, and a couple of bright stars it delivers wonderful images up to about 80x-100x magnification, at which point you run out of light on most objects anyways. I just use my 11"er for the high mag stuff. I think you'll love the AT1010, but if you want to make yourself feel good, look through a good achromat first at a star party.

Don't be too disappointed that your Nagler and Panoptic won't focus. They'd vignette brutally if they did After the focal reducer, a 2" eyepiece makes little sense.

But - fourth option, medium price (about $50-$60) for 1.25" eyepieces: buy a 2"-to-SCT adapter and a standart 1.25" SCT visual back (SCT-1.25"), and sandwich the reducer in between AFTER the diagonal. It won't be f6.3 any more, though, more like f7 or f8 or so, but it will focus.

I'd say go with the 2" filter and screw it into the front of the diagonal, that way it'll work for all eyepieces.

There's really no separate maximum power for using a well-made filter, other than running out of light.
The UHC is more versatile, the OIII better for some objects. See this discussion: http://www.cloudynights.com/howto/filters.htm

Finally, also consider this filter: http://www.astrovid.com/Astronomik%20Filters_files/Astronomik%20Filters.htm (I'd rather link you to Anacortes, but Herb apparently doesn't sell these?). Prices are comparable to the Lumicon, but the filter material/coating is reportedly more durable and the glass is polished better as well.

Ed ... did the 3" look "more pleasing" than the 8" or 16" when *all* had the same magnification?

I say it's indicative of the quality of everything else reported where we don't happen to know better ... unfortunately.

Every time anyone publishes something where I do have some outside understanding it's way off ... so why would it be any better in the other cases?

Maybe I don't understand what you're after, but the max field diameter for wide field viewing would be a tad under 1.25" or 2" depending on eyepiece format and yes, there would likely be some vignetting at least for the 2" field, as the light cone 3.5" away from the focal plane (i.e., at focuser entrance) is about 2.4 inches wide and your focuser probably isn't. (BTW, at the secondary, it's about 3.1 or so inches)