Posts Made By: Kevin Beebe

>>Anyone ever make rotating rings for a scope?

No, but I met a guy at the Oregon Star Party who had made a 10" and 16" with a rotating upper cage. I tried it out and it worked quite well.

His truss poles connected to a ring. Then the upper cage assembly was attached to this ring with rollers tensioned with springs and teflon spacers for bearings. The upper cage assembly was kept centered with the kydex baffle, which lapped over the ring.

Kevin

Wow, Vladimir! This is very interesting. Does this mean we (I have an f/4.5 and and f/5 newt) should all get Feathertouch focusers? Sounds like trying to focus a fairly fast telescope is a "hit or miss" situation.

Also makes me wonder about all the telescope reviews saying that objects "snap" into focus.

Kevin Beebe

When you use the 40mm eyepiece with the 8" f/4 scope the exit pupil is 10mm (40mm/4). Since the pupil of your eye will probably only dilate to 5mm to 7mm, you can't see the entire field of view at once.

A formula for maximum EP focal length is the f/ratio of your telescope x the maximum pupil diameter of your eye.

As for why you had problems with the 40mm in your ETX, I don't know. But I had similar problems with a Televue 40mm plossl in an f/10 SCT. I think it was too much eye relief. I don't wear glasses and it was hard to hold my head at the correct distance from the EP.

hope this helps a little.
Kevin

"Does it work to just say the focuser is just sqrt(2) farther away?"

Yes. That's the general idea anyway.

"Are there other considerations I need to make? "

Well, your focuser will take up more space because it will be tilted at 45 degrees. So to keep it out of the light path you must add 1/2 the width of the focuser to the height of the focuser. (or account for the distance some other way, like the thickness of the "tube")

Kevin

Sam,

Thanks for the Great idea. Where did you get this stuff? Is it available at the local hardware store or do you have to get it mail order at McMaster-Carr, or someplace?

I use a 16mm Nagler T6 the most, by far. But, if I could find a 20mm NagT5, it might win out.

I really liked the 40mm UO MK70 in my SCT, with and without the focal reducer. Sorry, but I haven't tried the others.

I have a 7mm, 12mm, the 5-8mm zoom, and a 24mm Speers Waler. I have also owned a 10mm and a 14mm, but sold them. I also have Nagler 7mm T6 and T1, and a 9mm T6. My telescope is an f/4.9 Newtonian.

In some limited testing, I have come to the opinion that the 7mm outperforms the 7mm Naglers (heresy), and the 10mm was extremely close to the 9mm Nagler in image quality. The 12mm SW is also very good and I would like to compare it to an 11mm T6 or 12mm T4 when I get a chance. The SW 9-element series are a step above the 8-element series, and as you go to longer FL, the image quality suffers considerably. I thought the 24mm was an excellent EP in my SCT, but on faster scopes the astigmatism at the edge of field is annoying.

The problem with the SW EPs is the size, IMO. I think they are six inches long and over 2" in diameter. They are a great value and I haven't been able to bring myself to sell them. Especially when they are the best in their focal range of the EPs I have tried. I have not tried any of the Meade UWA (except the 14) and only a couple Pentax (mid-range) so take my opinions with a grain of salt.

Hope this helps.
Kevin

Does anyone know where to get more caps when you lose them?
Thanks,
Kevin

Hey, I like your pole to upper cage connections. It's always interesting to see the creative ways people come up with. I just used the ones from Moonlight, but modified them a little.

Kevin