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Posts Made By: Doug Walton

March 31, 2004 05:17 AM Forum: CCD Imaging and Processing/Solar System

Re: Canon 300D question

Posted By Doug Walton

Red flags - sounds too cheap. I'd be concerned that it would be non-USA warranty, or a return that had something wrong with it, or a demo, or some other kind of silliness.

June 19, 2004 09:32 AM Forum: Equipment Talk

EP Question...

Posted By Doug Walton

I need some opinions and information regarding eyepieces. My details are:

1. 14.5" dob with Zambuto mirror, tracking (which lets me really study stuff in the center of the FOV).
2. I mostly do medium-high mag viewing, such that the range of 18mm down to 4mm covers me pretty well. For wide-field, a 35mm Panoptic works really well for my uses, but I'd be interested in options that are less expensive and as good or better.
3. I wear glasses, and I have a slight astigmatism that means that I usually have to view through them.
4. I've owned and used a set of Radians in the 18mm to 4mm range for several years (I sold them a while back). I also owned a Pentax 7mm that I bought a few years back. I liked the Radians a lot.
5. I'd give up a little FOV for extra sharpness, contrast and/or cost.

My questions are:

1. Are Radians still the best way for me to go?
2. Pentax has a new EP series out, but they're expensive. I figure they may be a slight bit nicer than Radians - true?
3. Is there a low-cost EP option out there (with adequate eye relief) that would give me great results (at least as good as Radians)?

I don't want to bugger up a great scope with so-so EP's - I'm want truly excellent views. And I want the EPs to work really well for lunar, planetary, and DSOs. grin

Thanks for your opinions!


July 13, 2004 08:29 AM Forum: Deep Sky Observing

M51 with binocs?

Posted By Doug Walton

Last night was unexpectedly clear and steady for a while at about 1 AM here on the souther shore of Lake Superior. And it was nice and dark.

I pulled out the 10x50 binocs and was scanning around the sky, and my eyes weren't really that dark-adapted yet. M13 was surprisingly obvious - it almost looked like I could make out some distinct stars in the fuzzball. I thought "Hmmm - I wonder if I could see M51.". So over I went, and I'm about 95% sure that I could see it. And it wasn't that difficult of a find either. It was an elongated faint fuzzblob that seemed to have the right size/shape, and it seemed to be in the right place based on my star charts.

Does it surprise anyone that M51 could be picked off by binocs, or is this relatively common and not a big deal?

Thanks, Doug

July 28, 2004 01:11 PM Forum: Equipment Talk

Eyeglasses, Astigmatism, and EPs

Posted By Doug Walton

I'd like to get some clarification on the assertion that short focal length (i.e. high power) EPs allow you to not use your glasses, even if you have an astigmatism.

At what point does this principle take effect? Assume a 14.5" f/4.3 dob for this example. Can I expect to be able to use a 3-6 Nagler zoom without my glasses, and not have my astigmatism affect the view? (That would be about 317-528x without a Paracorr, with exit pupils going from 1.2 down to .7)

Is there a formula relative to exit pupil that gives an answer? Is it variable based on the amount of astigmatism one has?

Thanks, and if I need to provide more info, let me know. Obviously, I'm wondering if I should buy a 3-6 Nagler zoom - it doesn't have enough eye relief for use with glasses, but it has plenty without.


December 10, 2004 09:45 AM Forum: Equipment Talk

Looking for info on Tom Mittler scopes and mirrors

Posted By Doug Walton

I'm looking for info on this fellow's scopes and mirrors. He makes assertions about the quality of his mirrors ("as good or better than Zambutos"), and I'd like to hear if anyone has actually used one of his mirrors (or has solid second-hand info) and has opinions or related thoughts on them.


January 10, 2005 02:51 PM Forum: Equipment Talk

Cooldown Rates: 12.5" ... 2" vs. 1.6"

Posted By Doug Walton

How much more slowly does a 2" thick, 12.5" primary cool down when compared to a 1.6" version? Assume passive cooldown, well-ventilated mirror box, cooldown from, say, 40 degrees to 10 degrees. A lot longer? A little bit? I'm used to waiting maybe 45 minutes to an hour for a 12.5" 1.6" thick mirror to cool to the point where the images start getting good. I know that a rear-mounted fan would accelerate things...


January 10, 2005 02:57 PM Forum: Equipment Talk

I keep seeing great images from Celestron 9.25's..

Posted By Doug Walton

Are these essentially the best mass-produced SCTs out there for planetary and lunar viewing? (Let's limit our discussion to SCTs in the 8"-12" range, since aperture might start to win out once we get to 14"). It seems like every time I see 9.25 images, they're astounding.

It would be interesting to put a 9.25 up against, say, a 10" high-end reflector in the f/6-f/7 range, and see what conclusions are reached for visual use on planets, lunar, and doubles.


January 23, 2005 11:02 AM Forum: CCD Imaging and Processing/Solar System

February 21, 2005 06:11 AM Forum: Birding Optics and Photos

Ultravids vs. Duovids vs. Swar. ELs

Posted By Doug Walton

I've got a very, very nice pair of Pentax DCF SP 10x50's.

I'm wondering how much nicer one of the three binos listed above might be (in the 8x42 range - I may move away from 10x50's into something with a wider FOV and a bit more stability).

Are the Duovids as sharp/contrasty as the Ultravids? (The 8x-12x feature might be kinda nice to have.) How do the Swarovski 8.5x42's compare to both of them? I'm interested in personal experience/opinions, and I'm mainly looking at contrast/sharpness/edges, since I'm assuming that CA and color are reasonable in all of them. I live pretty far from any kind of store where I could go and try them out, so educated opinions and anectdotal info ends up being quite useful.

PS: I did do a comparo between my Pentax DCF SPs and the Swarovskis maybe two years ago, and despite the difference in magnification/FOV I wasn't able to justify the difference in cost, even though there was improvement and lust with the Swarovskis. I might be able to swing it now. :-)


June 16, 2005 06:43 PM Forum: Equipment Talk

Best 2" O-III Filter?

Posted By Doug Walton

Previous posts didn't leave me with conclusive information. I'm wondering if anyone has reached a strong opinion about the Televue O-III versus the current Lumicon O-III. Assume a good dob in the 12"-16" range.