Jump to content


Photo

Just received an Odyssey Compact. Need some help..

  • Please log in to reply
35 replies to this topic

#26 wfj

wfj

    Apollo

  • *****
  • Posts: 1193
  • Joined: 10 Jan 2008
  • Loc: California, Santa Cruz County

Posted 10 June 2011 - 06:12 PM

Check out:
http://www.cruxis.co...ecalculator.htm

What I meant was two (or three) brackets with a bearing point along the side, positioned at a point midway up. If the mirror was flat, it would be at half the thickness of the mirror.

The point of the tape around the periphery of the mirror would be to restrict the movement of the mirror - just like mirror clips. And like them, the idea is to not have any force incident on the mirror in the normal operation of the scope, thus they don't distort the mirror. The normal load path is through the bearing surfaces ONLY. The clip/tape is to secure so that if inverted, the mirror doesn't fall out.

Do not recommend a tight ring around the mirror of firm material as thermal expansion might bind and buckle. Another approach is to use a edge support strap.

Do more research on cell design. You need to understand more.

I'm thinking of a low profile design (my mirror is further back in the tube, requires it) out of 3/8" square extruded aluminum in two T sections joined with collimation screws. Three bars with pivots in center and nylon pads at ends. Two outrigger brackets support the edge through a nylon bearing as a single point of contact. Tape surrounding mirror as in the original cell - that doesn't bother me.

Other links:
http://www.cloudynig.../fpart/all/vc/1
http://www.cloudynig...56/Main/2800258

#27 Mirzam

Mirzam

    Skylab

  • *****
  • Posts: 4449
  • Joined: 01 Apr 2008
  • Loc: Lovettsville, VA

Posted 11 June 2011 - 07:22 AM

Here's a 6-point cell that I made for a 12.5-inch scope. It shows the edge supports and clips well. In this case there are 4 supports because the scope is on a equatorial mount. The edge supports are at 90 degree intervals and have nylon bolts positioned at the mirror edge center of gravity (about half way up the edge).

JimC

Attached Files



#28 Mirzam

Mirzam

    Skylab

  • *****
  • Posts: 4449
  • Joined: 01 Apr 2008
  • Loc: Lovettsville, VA

Posted 11 June 2011 - 07:24 AM

I must say though that the original cell that came with your telescope looks like it was thoughtfully constructed.

JimC

#29 George S

George S

    Lift Off

  • -----
  • Posts: 4
  • Joined: 18 Nov 2009

Posted 11 June 2011 - 12:08 PM

You probably have this already,JMI has a document section on their website. I hope this helps.

http://jmitelescopes.../max_manual.pdf

#30 wfj

wfj

    Apollo

  • *****
  • Posts: 1193
  • Joined: 10 Jan 2008
  • Loc: California, Santa Cruz County

Posted 11 June 2011 - 02:20 PM

I must say though that the original cell that came with your telescope looks like it was thoughtfully constructed.

JimC


My criticism of it would be just the "slop" and "flop" aspects in its concept of "edge support". One could also improve the ventilation as well.

#31 Dan F.

Dan F.

    Explorer 1

  • -----
  • Posts: 92
  • Joined: 05 Jul 2010
  • Loc: Kalamazoo, MI

Posted 11 June 2011 - 03:37 PM

@Jim, I wonder if I can / should just fix the current cell and use that for now instead of constructing a new one (which I am also fine with).

@George, thanks. I actually found this the other day and proceeded to confirm that the system is working properly.

@wfj, from what I'm hearing it seems I'm going to need some guidance / directions in either dealing with this current cell or constructing a new one. Some things I understand, others I have yet to understand :grin:

#32 Mirzam

Mirzam

    Skylab

  • *****
  • Posts: 4449
  • Joined: 01 Apr 2008
  • Loc: Lovettsville, VA

Posted 12 June 2011 - 07:13 AM

Hello Dan,

A 6-point cell can be built with one trip to the hardware store. Here's picture of one that I use for my 14-inch. The mounting plate is honeycomb aluminum panel but could just as easily be wood. A little flexure in the mounting plate does not matter. Note the use of box channel (and a lot of little nuts and bolts) to build the support frame.

JimC

Attached Files



#33 Dan F.

Dan F.

    Explorer 1

  • -----
  • Posts: 92
  • Joined: 05 Jul 2010
  • Loc: Kalamazoo, MI

Posted 12 June 2011 - 09:04 AM

Jim, thanks for the photos. I like the previous design that you posted before this one. But I have a question. When I see cells such as yours, I see no silicone...I thought using silicone was the best way to mount the mirror. Is either method fine?

On another note, I just noticed on my coulter cell that the cardboard triangles used for the nine point were flexing to the point that the mirror essentially rests on the mounting posts rather than the points. Would aluminum strips eventually do the same thing with the eight pound mirror, and if so, would it be better to use square tubing like you do in your designs?

#34 Mirzam

Mirzam

    Skylab

  • *****
  • Posts: 4449
  • Joined: 01 Apr 2008
  • Loc: Lovettsville, VA

Posted 12 June 2011 - 11:01 AM

I didn't notice that your triangles were cardboard! Definitely not a good thing to be resting on the mounting posts. Aluminum sheet, thin steel or wood will work well. I like the simplicity of the box channel design but a mirror as light as yours will not tax things too much.

Incidentally, properly designed 6-point cells are usually superior to nine point cells for small mirrors. This is based on finite element analysis. See for example:

http://www.atmsite.o...ells/index.html

For my travel scopes like the 14-inch, I take the mirrors out and so do not use silicon. The 12.5-inch scope uses mirror clips that do not quite touch the mirror surface but will keep it from falling out if tilted down. This scope is permanently mounted.

JimC

#35 Pulsar345

Pulsar345

    Lift Off

  • -----
  • Posts: 1
  • Joined: 21 Jan 2013

Posted 21 January 2013 - 05:07 PM

I know this is an old thread but could you post some pix of these mods, and maybe the best place to source teflon pads. Thanks

#36 Glen A W

Glen A W

    Viking 1

  • -----
  • Posts: 941
  • Joined: 04 Jul 2008
  • Loc: USA

Posted 22 January 2013 - 10:26 AM

A great thread anyhow. It always amazes me how scopes fit the times. A scope like the Odyssey just takes me back to 70s-80s observing. Let us know how much fun you have been having with it. GW






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics