Posts Made By: Doug Scobel

Ed, I would say that it’s neither good nor bad – it just is. People have more disposable income now, so at the high end you’ll see the results of those who have the most to spend. But in no way does that take anything away from those who have to do everything with less. Yes, you are right – our results depend on what we are willing to spend, but it has little to do with money.

Like me. All of my equipment is homemade, the 6-inch f/8 (w/homemade primary) I made while in my early teens, the 13-inch f/4.5 dob (with refigured primary) that I’ve had now for nearly 20 years, a homemade barn-door camera platform, and the 8-inch f/8 (also with homemade primary) I just completed this past summer. No drives, no equatorial platforms, no thru-the-scope photography, no goto, no digital setting circles, all visual. Yet I’ve logged over 700 deep sky objects (not counting double stars), observed all the planets, observed sunspots, observed lunar and solar eclipses, observed, sketched, and photographed several comets, made several observations and sketches of Mars, photographed auroras, done wide-field sky photography, and I am closing in on the Herschel 400 list using only finder scope and star charts. You can see some of what I’ve done (along with other Lowbrows using ordinary equipment) strewn about the Lowbrows’ web site here: http://www.umich.edu/~lowbrows/astrophotos/

But does someone posting fantastic photos made with expensive equipment that they purchased rather than made somehow diminish what you or I have done by more modest means? No way. Yes, they can do things that I can’t do, but I can say the same about them. Frankly, I enjoy immensely the amateur images seen recently in S&T – they are truly amazing in many cases!

I think there’s room in this hobby for everyone – old or new school. It’s still the same subject. And I think that’s good.

Best regards,
Doug (old school) Scobel

I see that Orion is selling their Epic ED-2 eyepieces again, only $70.00 each. Does anyone have any direct experience with them, good or bad? I’m contemplating the 7.5mm, for use in an 8-inch f/8 (218x). I need the eye relief (glasses) and I’m working with a shoestring budget.

Thanks,
Doug Scobel

A lot has been written about baffling Newtonian reflectors, but I’m wondering if it is overkill in most cases. The attached picture is a scale CAD drawing I made of my 13.1-inch f/4.5. The tube has an ID of 16”. The blue arc at the left represents the front surface of the primary mirror, radius of curvature 117 inches. The short blue line at the right is the focal disk 58.5 inches from the primary, which I arbitrarily set to 1 inch diameter. The black lines represent light rays that just hit the outer edge of the focal disk. The yellow lines are normals to the mirror’s surface, about which these focal plane edge-grazing rays are reflected.

As you can see from the diagram, there are no light rays that can reflect off the inside of the tube (red lines), strike the primary mirror, and end up in the focal disk. If they do reflect off the inside of the tube, then they’ll miss the focal disk. In other words, no part of the inside of the tube is visible from the focal plane. All such rays would have to reflect twice off the inside of the tube, which is no biggie. Simple flat black paint would be fine – even at 5% reflectance, two reflections would result in only .0025% of the light reaching the focal disk.

Am I looking at this correctly? If I am, then putting annular baffles inside the tube do nothing. But, I think it would be advantageous to add a baffle at the open end of the tube to prevent seeing the sky itself.

FWIW, I did the same analysis of my 8-inch f/8 with 10 inch ID tube with the same results.

Any thoughts?

Doug Scobel

I braved the sub-zero temps (it was -8 F by 8:00 pm) and observed Comet C/2002 T7 LINEAR Saturday evening. Definitely brightening. Here's my observation notes and sketch.

Doug Scobel

My suggestion is that you get the most basic of star charts, or even a planisphere, so that you can find out for yourself that this is the most recognizable asterism in the northern sky, namely the "Big Dipper", which is part of Ursa Major, not Andromeda. You are going to have a hard time finding your way around the sky with your big binocs without charts.

...how fortunate we are that the plane of Saturn's orbit is inclined to that of Earth as much as it is. If the relative inclination was more like ours and Jupiter's, then we'd never get much of a view of it's rings.

Lucky us!

I finally observed comet C/2001 Q4 (NEAT) last night (12-May-2004) through haze, patchy clouds, and light pollution. In 8x40 and 10x50 binoculars it was surprisingly bright, with a very short tail, maybe half a degree that I could actually see, pointing away from the already set sun. I quickly set up the 13” in the driveway and at low power it was a very large and bright fuzzball. The nucleus is very concentrated and bright, almost star-like, even at 200x. The coma looked to me to be very broad and fan-like, as if it were extending into a tail (which I assume was there but sky conditions weren’t letting me see it). The short tail was more apparent in binoculars.

Here in the upper Midwest we've gotten into the summer weather pattern already. Warm, humid, hazy, and clouds, and scattered thunderstorms, especially late afternoon and evening. If only we could get a really clear night, I’m sure it’s spectacular. But at least I finally saw it.

Yippee!

Doug Scobel

Here's a shot I took of comet C/2001 Q4 (NEAT) last Sunday night, around UT 03:30 May 17. I was at Lake Hudson State Rec Area, in SE Michigan. Taken with my trusty ol' Olympus OM-1 with 100mm lens on my homemade barn door drive. Exposure is 10 minutes @ f/2.8 on Kodak Max 400 film, under about mag 5.9 skies. This is pretty close to the way it looked through 10x50 binoculars.

Sorry about the poor quality of the scan. I scanned the negatives on a Kodak "Photo Ditto" machine at my local department store, then saved the pics to a floppy disk. The machine says "Hi-Res" photos, WRT pics put on a floppy disk, but they lie. Each jpeg was a measly 20kb - not exactly "Hi-Res". Even with all the crap viewing SW on the disk (that I don't need), there's over 800 kb left on the disk! What were they saving it for? All they'll let you put on the disk is 5 images, which is what I had. I'll never do that again. Don't waste your money and time.

Doug Scobel

Observed comet Q4 NEAT from my driveway last night. Considering the nearly first quarter moon and my light polluted skies, it was still a nice view. It was hard to get the contrast right, especially the faint, wispy portion of the tail - it was much fainter than I have it here. Enjoy.

Doug

I don't see a lot of traffic on this forum but here goes. I recently acquired a Nikon Coolpix 800 and want to use it afocal with my Radians. I’m wondering what would be the best adapter to use. Televue sells one, but it requires a 2” focuser which I can’t use on my 8”, which has a 1.25” focuser. Scopetronix has one – does anyone have any experience with it? Are there any other choices or recommendations?

Thanks,
Doug