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This is a diagram I created years ago that gives the formula for the baffle diameter at any point down the tube. You need to know the back aperture DL (slightly less than the 7.75" front aperture) and back focal length BFL (123.375"), and decide on an unvignetted field width "d" (0.75" to 1" is probably about right). The formula gives the baffle ID "DB" at any point down the tube.

4-5 equally spaced baffles are probably adequate. For your 8" f/15 the first baffle would start about 5-6" back from the objective, and the last baffle would be about 12" forward of your focuser base.

Mike

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Mike...you posted this formula and diagram on my website AFTER I designed and built my baffle system for my 10"f/15.

I used 1" field width when I designed my system on the floor of my shop......

I also used 5 baffles along with the baffles within my focuser body. No baffles within the draw tube(over kill I think).

PLus...my thinking is that because the tube is 2" larger then the objective(1 full inch completely around)...I would be able to control stray light better...along with the thermal venting built into each baffle.

Your drawings are extremely helpful.....

Rob

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1st set of parallax rings arrived yesterday....AP single speed new style focuser arrived today. Bar stock for the 42" dovetail is in route.

Still searching for some 9 to 9.5" parallax rotating rings.....just missed a set too dang it.....

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Oooo the toys are comin in....

You know...the rain and cloud gods just don't get it when folks like to build their own scopes...so I predict a super first light....

Rob

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Should they be evenly spaced along the tube or is there a specfic pattern that works best?

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Why do you want rotating rings? Are these for a large finder or guide scope?

Jim

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Should they be evenly spaced along the tube or is there a specfic pattern that works best?

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Greg,
If you want to efficiently baffle a refractor without installing additional and unecessary baffles, the baffles will not be evenly spaced. I have built several refractors including 8", 10" and 11" and have used the following method:
http://www.berfield.com/baffles.html
Of course it doesn't hurt to add more baffles if you want to, but it won't increase the control of stray light.

Regards, Stan

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Try Parallax Instruments.

JimC

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Contacted Joe @ parallax and my sliding counter balance weights search is over.

Been reading up on the paperwork that came with the lens.....

Norman Remer design scaled to 8" using Schott glass, BK7 and F-2. Figured by Muffoletto Optical sometime prior to Verne Muffoletto's death in 1986.

Included were

Axial Ray Trace in 3 colors
Axial plots with 3 colors
Spot Diagrams in 3 colors (4 angles 0.0, 0.1, 0.2, 0.3 degree)
The program for both axial plots
Data showing ray height on each surface.

Lots of data to study if I knew what I was looking at lol

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It's good to know the data on your objective.

What *kind* of sliding counter balance are you getting from Parallax? (Any pix?). I built both of mine using lead weights cut to fit against the tube. I have yet to mount the forward one in hopes the weight of the objective and its adapter tube cell will be adequate.

I'll add it if need be.

Rob

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Was looking at the ones Jeff Blazey has on his 11" in the pics at your yahoo site and contacted him. He pointed me to Joe and the rest is history. Pics are:

http://groups.yahoo.com/group/HomemadeRefractorTelescopes/photos/album/1594999745/pic/list

He used copper water pipe and I am using stainless rod for the slide but the weights will be the same.

My 1"x4"x42" bar stock for the dovetail arrived and it surprised me how heavy it is.....Realized am I now pretty sure I wont be manhandling this thing into the saddle all in one piece

More likely installing the dovetail with the rings open and then sitting the OTA in it as I have seen others doing with these long scopes.....

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Was looking at the ones Jeff Blazey has on his 11" in the pics at your yahoo site and contacted him. He pointed me to Joe and the rest is history. Pics are:

http://groups.yahoo.com/group/HomemadeRefractorTelescopes/photos/album/1594999745/pic/list

He used copper water pipe and I am using stainless rod for the slide but the weights will be the same.

My 1"x4"x42" bar stock for the dovetail arrived and it surprised me how heavy it is.....Realized am I now pretty sure I wont be manhandling this thing into the saddle all in one piece

More likely installing the dovetail with the rings open and then sitting the OTA in it as I have seen others doing with these long scopes.....

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Oh..I see..you used the tube ring design..like Jeff's.

Yes and then you attach the extension for the slide bar.

Stainless bar will be quite heavy compared to either copper pipe..or like what I used steal pipe.

I made my counterweights to be extremely low profile to be in line with the over all design of my scope.

Does Parallax make the weights along with the rings..or are they a seporate item you need to buy from someone else?

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As far as I know Joe makes the weights.....I was planning to use the copper pipe method too but Joe said he had some smaller diameter stainless rod that wouldnt weigh too much....I do want them to stand off a bit from the scope to help offset the rotational torque induced by having a couple more scopes mounted on the main OTA since it will be in rotating rings.

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Was looking at the ones Jeff Blazey has on his 11" in the pics at your yahoo site and contacted him. He pointed me to Joe and the rest is history. Pics are:

http://groups.yahoo.com/group/HomemadeRefractorTelescopes/photos/album/1594999745/pic/list

He used copper water pipe and I am using stainless rod for the slide but the weights will be the same.

My 1"x4"x42" bar stock for the dovetail arrived and it surprised me how heavy it is.....Realized am I now pretty sure I wont be manhandling this thing into the saddle all in one piece

More likely installing the dovetail with the rings open and then sitting the OTA in it as I have seen others doing with these long scopes.....

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Oh..I see..you used the tube ring design..like Jeff's.

Yes and then you attach the extension for the slide bar.

Stainless bar will be quite heavy compared to either copper pipe..or like what I used steal pipe.

I made my counterweights to be extremely low profile to be in line with the over all design of my scope.

Does Parallax make the weights along with the rings..or are they a seporate item you need to buy from someone else?

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Got ya. Rotational torque can be a problem with rotating rings. I assume they are secured by way of nylon bolts.

I've successfully used my many spotters on my 6"f/15 and they never caused an issue to have to use rotating rings.

I'm assuming your tube will be 9"~10" OD. Will you go typical white with black rings...or try something *NOVEL* and paint it something different? Have you mentioned recently what you will be using for your mount?

I can't wait for the images to start coming in so we can see your fine project coming to furitian.

Good luck.

Rob

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