Posts Made By: Tom Hole

Got a new grill and a new lawn mower. Wife says the vacuum just blew up. Been a great spring so far.

Looking for something that will last and suck for a long time. I've had 4 vacuum's since I got married 15 years ago. My wife vacuums a lot.

Leaning towards a Miele right now. Test drove the Blue Moon today and it is quiet and sucks a golf ball through a garden hose. Pricey, but if it lasts 12 years, it will pay for itself.

Thoughts?

Tom

I was setting up for the ISS transit of Jupiter tonight and decided to play around with the off axis mask I built for my solar filter for my 11" Starmaster. It's a 4.5" OA hole.

1. Without a doubt, I prefer the presentation without all that diffraction stuff going on. A much more engaging view.

2. Without a doubt, there was a great deal more detail visible on Jupiter without the mask than with it. Seeing was a 4 of 10. I have a 16% CO in this f/5.6 Starmaster. This was no contest.

So, I have a question: Anyone know where I can get an 11" APO?

I am definitely going to try out curved spider vanes. I want to get that unobstructed look. I know about the spread out diffraction and all that, but I am in this hobby for my own (and as many kid's as I can find) enjoyment, and I REALLY enjoyed that unobstructed, accurate color view. Anyone put curved spider vanes on an 11", f/5.6, 1.83" secondary Starmaster?

Tom

"Until you understand the nature of how the BN are designed and why, you might want to use more caution. Otherwise it becomes necessary to clean up afterward."

Welcome to the crony club, Levente. Say something negative about a Siebert product and you get to see Harry's "anyone who isn't with me is against me" paranoia.

BTW, Harry, us customers get to say whatever we want and speculate about all manner of things. One of the nice things about freedom of speech. I can't supress your drivel and you can't tell customers (your customers, no less) to shut their pie holes. Ain't it great?

Tom

When will the feature that allows us to have forum posts emailed be available?

Tom

8) Saw this at Lowes today and thought it might be a great bino chair:

http://www.lowes.com/lkn?action=productDetail&productId=18646-81075-FTS696A



$69. Looked a bit flimsy for my 215 lbs frame, but I might go pick one up just to try it out. Fully reclines with a little head rest. It was very comfortable. Only thing I wish it had was a roatating base. Then it would be perfect. Ok, a cup holder and pizza warmer and maybe a juggy girl.

Tom

I just finished reading this article that was just published here on astromart:


http://www.astromart.com/articles/article.asp?article_id=30

Thought I'd go see how it applies to binoviewers.

I put the Denk II's in with the low power dual arm power switch. Should give me 1.23/1.67/2.11x magnification. I know my Starmaster's focal length is 1527mm and the mirror is 279.4 mm in diameter. I have accurately measured the mag of the power switch. I'll trust that TV makes ep's that match their advertised focal lengths. So, I went out and measured some exit pupils;

Eyepiece (mag factor): measured exit pupil (predicted exit pupil)

35 Pan (1x): 6.5 mm (6.41 mm)
24 Pan (1x): 4.5 mm (4.39 mm)

In the Denk II's w/ Power Switch

24 Pans (1.23x): 3.6 mm (3.57 mm)
24 Pans (1.67x): 2.5 mm (2.63 mm)
24 Pans (2.11x): 2.1 mm (2.08 mm)
13 Nags (1.23x): 2.0 mm (1.93 mm)

I'd say the ruler in front of the ep method is accurate to +- .1 mm.

Conclusion: There definitely is no physical vignetting of the light cone on axis.

So, where does it start vignetting? Well that was a little harder to nail down. Per the article, I slowly moved my eye to one side while watching the exit pupil. As advertised, it became elliptical as you moved off axis. At one point, I could see that the side of the ellipse towards the center of the ep was being cut off by something. I verified this in all directions. The point at which this happened was repeatable and measurable (well, kindof).

The only thing that I could kindof measure was the distance from the center of the ep to the center of the exit pupil at the time the vignetting occured. I don't know what this measurement means as Rick did not explain it in his article. Maybe it was pure coincidence that this distance was the same in both the 24 Pans and 13 Naglers (8-9 mm) and that this distance also happens to match the predicted 100% illuminated field size for this setup (9.4 mm).

I went ahead and put the 10.5 mm Pentax XL's in and they started to vignette just prior to hitting the field stop (maybe 2mm prior). That matches as well as the 100% field is still 9.4 mm and the 10.5 XL field stop is 11.4mm.

So, all of this matched up. If you wanna see if/where your binoviewers are vignetting, this'll do it. Measure the exit pupil diameter and see if that matches with predictions. If it does, the binoviewer is not cutting off the light cone at the center. Then slide that exit pupil out and see when the inside starts clipping. This takes some practice to get used to seeing it. It's not obvious at first. Measure how far out from center this happens (this is harder to be accurate) and compare that to theory. Mine seems to match right on for my Denks II's and power switch.

I am happier now that theory and observations have sorta matched up. Of course, I acknowledge that I could be dorked up and have it all wrong. If someone equally as boring as I (say Tom M, perhaps) could make the same measurements, we could get a second source of data.

Clear skies (yeah, tonight is clear),

Tom

Well, I got up early and went to work. Not to work, but to set up the Starmaster on the beach. Well, near the beach. On base the eastern view was over the Chesapeake Bay with no significant eastern obstruction. I started to set up at 0545 EDT next to a fellow club member who happened to work on base as well. About half the sun was visible above the low level fog over the bay. We continued to set up when Mike (the other guy) yelled over and said you could see Venus naked eye. My first reaction was, "yeah, right" but I looked (who wouldn't) and there was the sun, a deep red and huge on the horizon. And sure enough, there was a huge black hole in it. Holy crap! I did not expect to be able to see it naked eye (who would with all the horror stories and grave warnings) and I did not expect Venus to be that big. It was beautiful. Best view of the morning (and it was with 2 eyes . I had a look through my 12x36 binoculars and it was spectacular. This lasted about 2-3 minutes before the sun had risen enough so as to be too bright to view unfiltered.

We finished setting up our scopes. The anticipation fostered by that naked eye view was quickly followed by the frustration of not being able to find Sol. I usually use the shadow method, but the scope was horizontal and nary a shadow could be found. I searched and searched for what seemed like an eternity for that first view. Nothin', zip, notta. I decided to turn my Rigel on and hold my hand in front of it and get the sun in the rings. The sun was still very low and a simmering red-orange now. I got it lined up and looked through the 35 Pan (49x 1.5 deg TFOV, 11" scope) and there was the sun, barely visible. Had to cup my hands around my eyes and use averted vision (that seems whacky) to see it. Not a very good view, so we waited 10 minutes or so for Sol to brighten.

At about 0620, she was bright enough for the Starmaster, but I had to stick with the 35 Pan for a while as the 24 Pans in the binoviewer were too dim.

We all shared views and noted in awe how much bigger Venus was than what we were expecting. We shared stories of our loved ones coming out to look at such wonders as Andromeda, comet NEAT and any number of celestial showpieces and them commenting "is that it?" or "that's nice, dear". Anything less than Saturn on a perfect night at 400x does not impress my family. All we were really looking at was an orange disc with a hole in it. But the wonder and majesty of what we were looking at was not lost on any of us there this morning. Earth gets smaller every time I see something like that.

Anyway, about 0630, the sun was bright enough for the binoviewers. Put in the 24 Pans for 78x and a .84 deg TFOV. Now that's clean livin'. Going from squinting with the 35 Pan to opening both eyes up to a face full of sunshine was, well, great. Ya'll know what I mean. The view was easier and the fine details on the surface just jumped out at me. Now the majesty of the whole thing took on a whole new aspect. I was now in the image rather than looking at it. Lots of wows from the other folks that were there for the transit.

We watched Venus exit the solar disc. We were slightly disappointed that the tear drop effect was not as dramatic as we had built up in our mind's eye. But that didn't spoil the morning. We all yelled out at the exact moment that we thought Venus had exited the disc and all 3 yells happened at the same time. Then we packed up and went to work. Work that was made that much more enjoyable by the memories still fresh from that wonderful morning with Sol and Venus and friends who realized the significance of that entirely insignificant event. I'm still smilin'.

Clear skies,

Tom

Anyone else having an issue with this? I stopped getting forum posts via email on Fri/Sat. Just wanted to check before I bothered Herb. He seems busy.

Tom

http://www.astromart.com/classifieds/details.asp?classified_id=283511

That's a steal, by gosh.

Tom

I debated whether to share this with anyone, but I thought it might help the healing process :S

I bought a previously owned 11" Starmaster last Dec and it was a peach. Clearly bested my previous telescope and made me very happy. I knew I had the best 11" telescope I could afford. It fit me and my observing to at T.

Well, one day I was futzing around with something on the scope and placed one of my counterweights (a speaker magnet wrapped in duct tape) on the UTA to keep the nose down. At some point, I raised the UTA and heard the most awful sound I have ever heard in astronomy: the sound of a large metal object crashing into a Zambuto mirror. My heart sank, I went flush and thought I might faint like a sissy right there in the driveway. I looked in and saw the magnet laying on the mirror and a chink in the coating and a slight smudge to the side. A gross stain on a work of art, but maybe it was not as bad as it sounded. Here's the magnet:



Here's the aftermath:



I emailed Carl and asked if the damage was terminal. He said he couldn't evaluate it over the internet or phone, but he would be glad to have a look at it if I wanted to ship it to him. I decided to just put some black magic marker on the chip and see what the views were like.

After 4 months of using it, I decided that the views were not as good as when I first bought the scope. I also decided I could not stand looking at that chip every time I checked the collimation. So, I shipped it off to Carl, hoping for the best.

Yesterday, Carl sent me a note saying that the chip was too deep to fix and there was an area of local stress created that would need to be covered by a large black circle in order to mask its effects (a 1" diamter circle). Ack, barf. Basically, the mirror would make a good ashtray.

So, I get to decide whether to live with a 1" black circle on the mirror or get it replaced to the tune of $1,100. Stupid, stupid, stupid. I feel like a complete and utter buffoon.

Anyway, lesson learned and passed on. Read and heed. This was my first truss scope and my inexperience has proven quite costly. I do not work on the Starmster now unless the primary is covered. Hope it saves someone else. At least it wasn't a 24" ZOC mirror.

Tom