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GShaffer
Carpal Tunnel
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Reged: 02/28/09

Loc: Bogart, Ga USA
Re: 8" f/15 refractor project new [Re: rwiederrich]
      #3668569 - 03/08/10 09:11 PM

Probably dont need the rotation but I like the idea, sort of a gatling gun effect

9" tube....Real telescopes are white....real rings are black unless they have diamonds attached

I did order a set of 4" MOONEYES stickers for each side of the dew shield if that helps your sense of novelty lol....


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mikey cee
Postmaster
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Reged: 01/18/07

Loc: bellevue ne.
Re: 8" f/15 refractor project new [Re: GShaffer]
      #3668742 - 03/08/10 10:56 PM Attachment (70 downloads)

What the hell is a mooneye? Real custom telescopes are green. If it comes white you have to abide by that fact.:pMike

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rwiederrich
Goldfinger
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Reged: 11/17/05

Loc: Always Dark skies of Belfair W...
Re: 8" f/15 refractor project new [Re: GShaffer]
      #3669284 - 03/09/10 08:58 AM

Quote:

Probably dont need the rotation but I like the idea, sort of a gatling gun effect

9" tube....Real telescopes are white....real rings are black unless they have diamonds attached

I did order a set of 4" MOONEYES stickers for each side of the dew shield if that helps your sense of novelty lol....




I'll be interested in seeing how you handle the induced rotation issues with several spotters.

I'll let the *white* comment slide by...simply because you and I both know that isn't so......

Keep up the good work......

Rob


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rwiederrich
Goldfinger
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Reged: 11/17/05

Loc: Always Dark skies of Belfair W...
Re: 8" f/15 refractor project new [Re: mikey cee]
      #3669317 - 03/09/10 09:13 AM

Quote:

What the hell is a mooneye? Real custom telescopes are green. If it comes white you have to abide by that fact.:pMike




You made a very good point....*If it COMES white*.
Real homemade refractors are always green.....

Because the maker...makess it so...
The 12" at Griffith park is green.....Palomar is green(well its a reflector). Your Brandt beauty.....

Any way...it looks like we are still in the minority.

Rob(green is the new white)


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Jeff B
Carpal Tunnel
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Reged: 12/30/06

Re: 8" f/15 refractor project new [Re: rwiederrich]
      #3669381 - 03/09/10 09:47 AM

Quote:

Quote:

Probably dont need the rotation but I like the idea, sort of a gatling gun effect

9" tube....Real telescopes are white....real rings are black unless they have diamonds attached

I did order a set of 4" MOONEYES stickers for each side of the dew shield if that helps your sense of novelty lol....




I'll be interested in seeing how you handle the induced rotation issues with several spotters.

I'll let the *white* comment slide by...simply because you and I both know that isn't so......

Keep up the good work......

Rob




With regards to the torque induced by the finders & other accessories, in my case a 4" F10 achromat. That's what the counterpoise weight system does, it balances the off axis torque induced by those accessories. With big diameter tubes, that torque is considerable and applies added stress to the RA and DEC gear trains if not compensated for. Also, the rotating rings for the main scope would be useless without the counterpoise weights as the accessories would always want to rotate themselves down to the bottom. You'll notice on my design, I space them out from the tube a ways to give them more counter-torque. Then I put the weights on a sliding bar so that I can balance the scope when swapping out various eyepieces and especially the bino viewer. I left a stub shaft sticking out a couple of inches from the aft most support bracket. I attach a weight there that just happens to be the same weight as the binoviewer. So when I attach the binoviewer I simply remove that extra weight.

With regards to the rotating rings themselves, well...I LOVE THEM!! Getting easy access to any of the finders or the 4" scope for wide field views no matter what I'm looking at or where I am in the observatory is simply a matter of grabbing the handles on the back plate and rotating the tube around. They also allow me to rotate the accessories out of the way when I go to close the roof. They were a bit pricy but well worth the extra bucks IMO. BTW the rings are held to the main tube with ten, 3/8" nylon bolts.

With regards to the color white, well in my case I wanted powder coating and the only vendor who could do a tube of that length offered only black, red, yellow, blue, green and...white. Hey for only $150, which included the dew shield, I took good old white. I was thinking of a nice pearl metalic but my auto body buddly wanted over $800 to do a proper job of it. Besides powder coating is tough as nails so when I went to slide the rings over the tube, there were NO scratches and NO ring rashes from the accessory clamps.



Jeff


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rwiederrich
Goldfinger
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Reged: 11/17/05

Loc: Always Dark skies of Belfair W...
Re: 8" f/15 refractor project new [Re: Jeff B]
      #3669473 - 03/09/10 10:38 AM

Quote:

Quote:

Quote:

Probably dont need the rotation but I like the idea, sort of a gatling gun effect

9" tube....Real telescopes are white....real rings are black unless they have diamonds attached

I did order a set of 4" MOONEYES stickers for each side of the dew shield if that helps your sense of novelty lol....




I'll be interested in seeing how you handle the induced rotation issues with several spotters.

I'll let the *white* comment slide by...simply because you and I both know that isn't so......

Keep up the good work......

Rob




With regards to the torque induced by the finders & other accessories, in my case a 4" F10 achromat. That's what the counterpoise weight system does, it balances the off axis torque induced by those accessories. With big diameter tubes, that torque is considerable and applies added stress to the RA and DEC gear trains if not compensated for. Also, the rotating rings for the main scope would be useless without the counterpoise weights as the accessories would always want to rotate themselves down to the bottom. You'll notice on my design, I space them out from the tube a ways to give them more counter-torque. Then I put the weights on a sliding bar so that I can balance the scope when swapping out various eyepieces and especially the bino viewer. I left a stub shaft sticking out a couple of inches from the aft most support bracket. I attach a weight there that just happens to be the same weight as the binoviewer. So when I attach the binoviewer I simply remove that extra weight.

With regards to the rotating rings themselves, well...I LOVE THEM!! Getting easy access to any of the finders or the 4" scope for wide field views no matter what I'm looking at or where I am in the observatory is simply a matter of grabbing the handles on the back plate and rotating the tube around. They also allow me to rotate the accessories out of the way when I go to close the roof. They were a bit pricy but well worth the extra bucks IMO. BTW the rings are held to the main tube with ten, 3/8" nylon bolts.

With regards to the color white, well in my case I wanted powder coating and the only vendor who could do a tube of that length offered only black, red, yellow, blue, green and...white. Hey for only $150, which included the dew shield, I took good old white. I was thinking of a nice pearl metalic but my auto body buddly wanted over $800 to do a proper job of it. Besides powder coating is tough as nails so when I went to slide the rings over the tube, there were NO scratches and NO ring rashes from the accessory clamps.



Jeff





Jeff I'm so glad you piped in.....

Yes..counter weighting the spotters is a necessity with rotating rings...as you clearly pointed out.

However...I've taken the approach that I located my spotters at 90deg to each other...kinda countering themselves. You've done so well in your example..and it can be used as a guidepost. Since tube rotation isn't an issue for me....counter balancing is done via the simplest way..I could think.

As far as color.....any large refractor is beautiful..in any color. I don't clamp... I bolt. the only ring marks if any will be by the main tube rings. And they won't be seen cuz the scope *Lives* there clamped in them.

Your scope is as awesome as they can come.....

Rob


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GShaffer
Carpal Tunnel
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Reged: 02/28/09

Loc: Bogart, Ga USA
Re: 8" f/15 refractor project new [Re: mikey cee]
      #3670051 - 03/09/10 02:35 PM Attachment (66 downloads)

Allow me to elucidate The largest ones are 4" tall. Mooneyes is now a automobile performance parts company but I believe they got start making the old popular "mooneyes" wheel covers that were real popular 40 yrs or so ago.




Quote:

What the hell is a mooneye? Real custom telescopes are green. If it comes white you have to abide by that fact.:pMike




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GShaffer
Carpal Tunnel
*****

Reged: 02/28/09

Loc: Bogart, Ga USA
Re: 8" f/15 refractor project new [Re: rwiederrich]
      #3670101 - 03/09/10 02:52 PM

Two sets of counterweights....one set ahead of the rings that can be slid from just behind the dewshield to just infront of the front rotating ring. Doubles as rotational counter balance and can be moved back and forth for front to rear balancing also. If I need additional weight to offset a change in the rotation balance but need to keep the front to rear the same I will add one weight to each end.....Should make for a very versitile setup.

Jeff Blazey gets the credit as I stole the concept from his setup Thanks Jeff.....

Another set at the rear which also can be slid back and forth from just behind the rear rotating ring to just in front of the focuser. Also accomplishing two purposes like the set in the front.

Quote:

Quote:

Probably dont need the rotation but I like the idea, sort of a gatling gun effect

9" tube....Real telescopes are white....real rings are black unless they have diamonds attached

I did order a set of 4" MOONEYES stickers for each side of the dew shield if that helps your sense of novelty lol....




I'll be interested in seeing how you handle the induced rotation issues with several spotters.

I'll let the *white* comment slide by...simply because you and I both know that isn't so......

Keep up the good work......

Rob




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GShaffer
Carpal Tunnel
*****

Reged: 02/28/09

Loc: Bogart, Ga USA
Re: 8" f/15 refractor project new [Re: GShaffer]
      #4309922 - 01/12/11 05:17 PM

Have resumed work on the project and been thinking on the baffel system and how to construct it.....Obviously being a f/15 8" its going to be a rather long scope.

Finally had a brainstorm after thinking for a while on a pic of John Pons baffle system for his 11" that Daniel Mounsey sent me a pic of.....

Carbon Fiber arrow shafts used as spacers between the baffles, baffels made out of thin aluminum plate with a triangle configuration of the arrow shafts as spacers. Can easily cut them to length, glue in the inserts you would normally screw the broadhead into and use a piece of threaded rod to connnect them with the baffles sandwiched between the ends.....

Super light, strong, already nice and dull black ....will have 5 baffles and once assembled can just be slid into the tube and anchored at the ends.....

Cant think of a reason this wouldnt work well.....thoughts?....Anyone done it?


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Dick Parker
scholastic sledgehammer
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Reged: 08/17/07

Loc: Tolland, CT and Chiefland, FL
Re: 8" f/15 refractor project new [Re: GShaffer]
      #4310014 - 01/12/11 05:46 PM Attachment (57 downloads)

It is not necessary to get that elaborate. I have made baffles in a similar fashion for my 6 inch f/15. I used plywood disks though and wood stringers. Small screws held the disks to the stringers. Very simple, very light. See attached photo. I did paint the assembly flat black before I inserted it into the tube, but I thought showing the baffle system before paint might be more useful. You could improve upon this slightly by trimming the ID of each disk into a thin edge.

If your main question about "..anybody done this.." is more directed toward the concept of making baffle disks on stringers that you slip into a tube, Yes, it has been done and I highly recommend it.

Dick Parker


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rwiederrich
Goldfinger
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Reged: 11/17/05

Loc: Always Dark skies of Belfair W...
Re: 8" f/15 refractor project new [Re: Dick Parker]
      #4310067 - 01/12/11 06:04 PM

My 5 baffle ring/stringer was 13ft long and slit nicely into the tube of my 12" OTA. It doesn't need to be secured because it rests up against the back plate...and since it is firmly placed and the scope aims high...it isn't going anywhere. However...I cn easily grab it and slide it out if need be..after I remove the cell adapter from the tube.

Rob


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Sean Cunneen
Let Me Think
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Reged: 08/01/07

Loc: Blue Island Illinois
Re: 8" f/15 refractor project new [Re: rwiederrich]
      #4310247 - 01/12/11 07:14 PM

Stringers are the way. You can't see them from the tube and you have precise control making them square. Baffles that you press fit or screw in to attach can look slightly off unless your lucky...




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Jeff B
Carpal Tunnel
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Reged: 12/30/06

Re: 8" f/15 refractor project new [Re: Sean Cunneen]
      #4311209 - 01/13/11 08:20 AM

With a larger instrument, tube currents are an issue. The warm air can pile up and spill over the baffle and into the light path. so I've adopted a best practice of "ventilating" my baffles. This is basically leaving a small gap between the tube and baffle OD, which allows the warmer air to cling to the tube wall and not pond or pool behind the baffles. There are many ways to do this. One of the simplest with the stinger arrangeement is to simply allow the stinger to stick out from the baffle OD a bit, thus creating the desired gap between the tube ID and baffle OD. Also, this makes assembly into the tube very easy as the baffles tend to self-center and you're only sliding them in along stingers instead of the baffle ODs. With a long & large baffle array, sliding them in on the baffle ODs can be a challenge as each baffle adds its own friction against the tube wall. This couple with the fact that the tube will not be perfectly round at some points along its length can make baffle installation with that design a very fustrating and tense experience.

And don't forget the PICTURES (!!)

Jeff


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GShaffer
Carpal Tunnel
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Reged: 02/28/09

Loc: Bogart, Ga USA
Re: 8" f/15 refractor project new [Re: Jeff B]
      #4311286 - 01/13/11 09:03 AM

Thanks guys.....I had considered using wood but want the scope to remain as light as possible....the carbon graphite shafts and thin aluminum sheet for the baffles seemed the best solution.....

Jeff B....I had not considered this regarding the tube currents so I will put some thought into that....thanks!


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Mirzam
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Reged: 04/01/08

Loc: Lovettsville, VA
Re: 8" f/15 refractor project new [Re: GShaffer]
      #4311438 - 01/13/11 10:19 AM

I think you would want a pretty close fit of the baffle rings to the tube, but not so tight as to make it difficult to insert the baffle assembly. The reason for this is to avoid leakage of low angle reflected light around the outer edges of the baffles. If you build an assembly that is too loose you will see what I mean (been there already).

JimC


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Darkenergy426
journeyman


Reged: 01/10/11

Re: 8" f/15 refractor project new [Re: Mike I. Jones]
      #4311750 - 01/13/11 01:02 PM

The optic world lost out, but I'll bet that the lawyers didn't.

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rwiederrich
Goldfinger
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Reged: 11/17/05

Loc: Always Dark skies of Belfair W...
Re: 8" f/15 refractor project new [Re: Jeff B]
      #4311793 - 01/13/11 01:19 PM

And as one can recall..that is the very design I utalized for my 12" tube. It is(IMV) a must to allow heat access..and as you accurately described, it permits 3 points of contact instead of the entire OD of the individual rings.

It worked for me that's for sure.

Rob


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rwiederrich
Goldfinger
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Reged: 11/17/05

Loc: Always Dark skies of Belfair W...
Re: 8" f/15 refractor project new [Re: GShaffer]
      #4311800 - 01/13/11 01:22 PM

Visit my yahoo site..*Homemade refrator telescopes* and check out the images of what I did for my 10"f/15.
Jeff B has some images there as well of what he did.

Rob


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Jeff B
Carpal Tunnel
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Reged: 12/30/06

Re: 8" f/15 refractor project new [Re: rwiederrich]
      #4311876 - 01/13/11 02:01 PM

Thanks Rob!

And even more helpful hints:

I usually use a fully illuminated field spot at focus of ~35-40MM and I don't recommend using the IDs of the focuser drawtube or the diagonal nose to set the spot size. Those restrictions can create a bit of scatter as they typically are not "knife edge" and they are behind the baffling, who's mission is to absorb stray light.

Rather, I use one of the stops about 30-50% back from the lens to set the spot and , even though the other stop ID's have been calculated for a certain axial position, I actually position them a couple of inches behind where they should be. But why he asks? Well even knife edge baffles have scatter and if you position them exactly where the calculations say they should go, that means their IDs are touching the light cone and the small scatter from their IDs can intrude. Backing them up a couple of inches from their "ideal' location removes them and their scatter from the light path.

TAH DAH.

Jeff


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rwiederrich
Goldfinger
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Reged: 11/17/05

Loc: Always Dark skies of Belfair W...
Re: 8" f/15 refractor project new [Re: Jeff B]
      #4312182 - 01/13/11 03:50 PM

Quote:

Thanks Rob!

And even more helpful hints:

I usually use a fully illuminated field spot at focus of ~35-40MM and I don't recommend using the IDs of the focuser drawtube or the diagonal nose to set the spot size. Those restrictions can create a bit of scatter as they typically are not "knife edge" and they are behind the baffling, who's mission is to absorb stray light.

Rather, I use one of the stops about 30-50% back from the lens to set the spot and , even though the other stop ID's have been calculated for a certain axial position, I actually position them a couple of inches behind where they should be. But why he asks? Well even knife edge baffles have scatter and if you position them exactly where the calculations say they should go, that means their IDs are touching the light cone and the small scatter from their IDs can intrude. Backing them up a couple of inches from their "ideal' location removes them and their scatter from the light path.

TAH DAH.

Jeff




You're so smart.

Rob(Did I teach you that?)


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