10491 replies to this topic

[starman876]

Everyone in Florida drives like a maniac!

 

-drl

Tell me.  They pull out right in front of you. Must be that retired attitude.  

[starhunter50]

bit weird , to say the least, but im working on other problems first, like star roundness, and its not the vanes, the orioginal ones were horrible shadows.

So i have to master collimation first.  see M13.

 

[starhunter50]

Here is Vega...the secondary flares are caused by my mirror clips,  im working on that too.

 

[deSitter]

Here is Vega...the secondary flares are caused by my mirror clips,  im working on that too.

 

flar.jpg

 

As expected, the offset vanes instead of radial are producing a very complex diffrection pattern. All, is there a simple program that can convert any entrance pupil geometry into a diffraction pattern?

 

-drl

[Cavs56]

I finally had a semi-clear night and got to spend some time with my 4 inch 15.5 Jaegers build. Optics are excellent and I liked the Criterion mount, very smooth. I had it on a pier I built using the Criterion Dynamax legs. It was not sufficient a 10 to 15 mph breeze was moving the telescope. Not much but I would prefer zero. I had the old pier from the Criterion so I mated it to a Meade field tripod I had. Should be much better I can also adjust the height now. I used a piece of round aluminum stock. Drilled three holes to mount it on the tripod then drilled and tapped three more through the pier. I like it. I will have to get three moving skates for the tripod it’s heavy.

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[deSitter]

I finally had a semi-clear night and got to spend some time with my 4 inch 15.5 Jaegers build. Optics are excellent and I liked the Criterion mount, very smooth. I had it on a pier I built using the Criterion Dynamax legs. It was not sufficient a 10 to 15 mph breeze was moving the telescope. Not much but I would prefer zero. I had the old pier from the Criterion so I mated it to a Meade field tripod I had. Should be much better I can also adjust the height now. I used a piece of round aluminum stock. Drilled three holes to mount it on the tripod then drilled and tapped three more through the pier. I like it. I will have to get three moving skates for the tripod it’s heavy.

 

Skinny piers are just inherently unstable and the worst way to mount a long refractor. I have no idea how this idea gained footing. You need some tall, very stiff wooden legs and a very sturdy spreader with tight locking to the legs.

 

-drl

[Kefka1138]

Upgraded my rails to ADM/Losmandy for improved stability. So much more stout than the original Viven setup. 

 

Edited by Kefka1138, 08 May 2025 - 07:08 PM.

[clamchip]

Today I vacuumed my ETX-90 optical tube.

I wasn't quite sure how to attack it with it's thick layer of dust.

If I blew it off with compressed air I'd probably blow a bunch inside.

Water would have turned it to mud.

So I got out our canister type house vacuum with brush head and

it cleaned it off well. Good suction better than my shop vac.

I then followed with a soapy sponge.

Next I DPAC tested it and found it almost undetectably overcorrected

just exactly the same correction as my other ETX-90.

I'm finding Mak's are ether under or over corrected, so rare to find a

jail bird. I own two with jail bars, my Jaegers Astele 150 and my ETX-125

and yet they all are magnificent at the eyepiece. The Maksutov is a

mysterious design.

 

Robert

Edited by clamchip, 08 May 2025 - 11:50 PM.

[deSitter]

Today I vacuumed my ETX-90 optical tube.

I wasn't quite sure how to attack it with it's thick layer of dust.

If I blew it off with compressed air I'd probably blow a bunch inside.

Water would have turned it to mud.

So I got out our canister type house vacuum with brush head and

it cleaned it off well. Good suction better than my shop vac.

I then followed with a soapy sponge.

Next I DPAC tested it and found it almost undetectably overcorrected

just exactly the same correction as my other ETX-90.

I'm finding Mak's are ether under or over corrected, so rare to find a

jail bird. I own two with jail bars, my Jaegers Astele 150 and my ETX-125

and yet they all are magnificent at the eyepiece. The Maksutov is a

mysterious design.

 

Robert

 

f/14 is getting fast for a spot Mak with spherical optics. Nevertheless mine is authentically "diffraction limited" as they used to say. it's definitely not as good as my 90/1400mm achromat (Sears 6345). It's about par with my 90/900mm achromat, which is a very good lens.

 

-drl

[clamchip]

I love the Mak, it's quickly becoming my favorite design.

Somewhere I read,  "don't be surprised if intra and extra star test patterns are not the same."

I think I'm seeing this during DPAC testing too and we are supposed to ignore it. "Nature of

the beast."

 

Robert

[deSitter]

I love the Mak, it's quickly becoming my favorite design.

Somewhere I read,  "don't be surprised if intra and extra star test patterns are not the same."

I think I'm seeing this during DPAC testing too and we are supposed to ignore it. "Nature of

the beast."

 

Robert

 

Same here. As close to a perfect scope as can be imagined.

 

-drl

[deSitter]

f/14 is getting fast for a spot Mak with spherical optics. Nevertheless mine is authentically "diffraction limited" as they used to say. it's definitely not as good as my 90/1400mm achromat (Sears 6345). It's about par with my 90/900mm achromat, which is a very good lens.

 

-drl

 

I should say, the latter comment regards only spherical correction. The ETX90 is a far better telescope because it is colorless. That is the most amazing thing about the Mak - despite having a massive singlet lens in front, it is basically perfectly apochromatic.

 

-dlr

Edited by deSitter, 09 May 2025 - 12:57 AM.

[deSitter]

Skinny piers are just inherently unstable and the worst way to mount a long refractor. I have no idea how this idea gained footing. You need some tall, very stiff wooden legs and a very sturdy spreader with tight locking to the legs.

 

-drl

 

I should say more here. The short tripod + pier has a fatal weakness - when there is force on the scope, the entire mount and scope and pier flexes at the point where the pier connects to the tripod. There is no way that can be stable under any circumstance. With legs that go all the way to the mount head, force on the scope is transmitted to the legs tangentially. Flexure is impossible.

 

-drl

[Cavs56]

The best mount I have used is a Vixen alt-az with an 80mm and a 90mm telescope. No vibration. I use the slow motion cables as I am viewing and it is perfectly smooth. My Unitron 150 has some vibration not much but it is still there. It is better if placed in grass. It also has a lot more mass than an 80 or 90mm telescope. I have an early Vixen Polaris mount I am going to put on the pier still deciding how to mount it. I think I will use it alt-az. My issue with the pier was wind. So possibly it is the telescope and mount. Weather is finally improving so I’ll be out again tonight.

[cavedweller]

I should say more here. The short tripod + pier has a fatal weakness - when there is force on the scope, the entire mount and scope and pier flexes at the point where the pier connects to the tripod. There is no way that can be stable under any circumstance. With legs that go all the way to the mount head, force on the scope is transmitted to the legs tangentially. Flexure is impossible.

 

-drl

I discovered this with the CI-700 tripod extension. Adding a few inches between the legs and mount head produced a flexure I could not tighten up. I did not notice it much with the C6R, but the 178 was wobbling 30 seconds after every touch. 

[apfever]

I should say more here. The short tripod + pier has a fatal weakness - when there is force on the scope, the entire mount and scope and pier flexes at the point where the pier connects to the tripod. There is no way that can be stable under any circumstance. With legs that go all the way to the mount head, force on the scope is transmitted to the legs tangentially. Flexure is impossible.

 

-drl

A little strange on the wording but not much. "...tangentially. Flexure is impossible."     

Flexure is possible even if the numbers are perfectly rigid in design. That is in the Materials Science. I don't think we want to go into wood vs. aluminum vs. steel and so on.

Lets stick to the design aspect. The biggest problem with our tripods is the attachment of the legs to the hub. Never mind if the hub goes to a pier or directly to the mount or even if your scope is bolted flat to the hub. For some reason the scope people have missed the tripod boat from beginner level to Unitrons. Surveyors seem to get it right. 

 

A tripod leg should spread out as much as possible from ground to hub. Ideally the leg sides (rails) should spread out to where they touch the rail of an adjacent leg. Our tripod legs should form a geometrical HEXAPOD for rigidity. Look at surveyor tripods where a leg's rails are closer to another leg than themselves. The top of the leg is WIDE. The distance from one leg rail to another leg's rail is SMALL.  Considerably older telescopes seem to be better and getting a grip on it.

 

Check out this spindly 5' tall tripod with rude and crude bolt up construction and large diameter hub. It has thin electrical conduit tubes (totally tubular is another discussion, groovy).  The top of the legs almost touch each other, a hexapod configuration. I drop this on a grabby surface like a concrete driveway - No spreader or center ties - and it is Rock Solid. It is Freaky Sharp (rigid) to put Chas to shame. I use it for a demo and watch people put there hand on the top and try to move it around. Then I watch them do it again and sometime more, with a big grin or chuckle. It's funny rigid. My 1927 B&L tripod gets the idea, not perfect but substantially better than average.  

 

A hexapod is perfectly rigid numerically and it shows in reality. It STRUTS it's stuff. (so sorry for that one, had to do it, just hit me)

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[apfever]

Why oh why telescope tripods went to this rotten concept just blows my mind. The tops of the legs are close to themselves and far from adjacent legs. It's not stable, it allows wobble. "Wobble" is a rotational force, it's not tangential.  It's easier and cheaper to build, especially for rectangular legs. 

A hexapod will resist all 6 directional forces, the three dimensions of 'tangential' and the three dimensions of torque. You can't beat it for a tripod. 

I used to teach a lot of those books in college but that was 35 to 40 years ago. Don't ask for the numbers or derivations, I'm beyond a brush up now. The concepts are correct. 

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Edited by apfever, 09 May 2025 - 09:01 AM.

[deSitter]

A little strange on the wording but not much. "...tangentially. Flexure is impossible."     

Flexure is possible even if the numbers are perfectly rigid in design. That is in the Materials Science. I don't think we want to go into wood vs. aluminum vs. steel and so on.

Lets stick to the design aspect. The biggest problem with our tripods is the attachment of the legs to the hub. Never mind if the hub goes to a pier or directly to the mount or even if your scope is bolted flat to the hub. For some reason the scope people have missed the tripod boat from beginner level to Unitrons. Surveyors seem to get it right. 

 

A tripod leg should spread out as much as possible from ground to hub. Ideally the leg sides (rails) should spread out to where they touch the rail of an adjacent leg. Our tripod legs should form a geometrical HEXAPOD for rigidity. Look at surveyor tripods where a leg's rails are closer to another leg than themselves. The top of the leg is WIDE. The distance from one leg rail to another leg's rail is SMALL.  Considerably older telescopes seem to be better and getting a grip on it.

 

Check out this spindly 5' tall tripod with rude and crude bolt up construction and large diameter hub. It has thin electrical conduit tubes (totally tubular is another discussion, groovy).  The top of the legs almost touch each other, a hexapod configuration. I drop this on a grabby surface like a concrete driveway - No spreader or center ties - and it is Rock Solid. It is Freaky Sharp (rigid) to put Chas to shame. I use it for a demo and watch people put there hand on the top and try to move it around. Then I watch them do it again and sometime more, with a big grin or chuckle. It's funny rigid. My 1927 B&L tripod gets the idea, not perfect but substantially better than average.  

 

A hexapod is perfectly rigid numerically and it shows in reality. It STRUTS it's stuff. (so sorry for that one, had to do it, just hit me)

 

That's the way to do it. But I was speaking specifically of big long refractors and the necessary stout mount head necessary. 

 

The Meade field tripods have widely space pivots which mimic the widely split yokes on these legs.

 

Narrow splits allow side-to-side flexure but are better for big refractors than a short tripod under a short pier.

 

-drl

[tim53]

Tell me.  They pull out right in front of you. Must be that retired attitude.  

Florida State Trooper (after pulling a motorist over for speeding):  Son, I've been waiting for you all day!

Motorist:  I'm sorry officer, I got here as fast as I could!

[Bomber Bob]

A hexapod will resist all 6 directional forces, the three dimensions of 'tangential' and the three dimensions of torque. You can't beat it for a tripod.

 

Would wide leg spacers at the top make the tripod hub that much more expensive than conventional designs?

 

I assumed the reason was to brace the sliding center leg, since a few of the fixed-height tripods had wider top spacers...  and, if the leg tops touched, that would make tightening the top bolts trickier...

 

At the eyepiece, I'm mainly concerned with damping time at medium & high powers.  More than a couple of seconds... is annoying for visual; and, a PITA for planetary imaging.

[Bomber Bob]

This is an old CG-5 hub sitting on one of my tripods:

 

CG5 hub 01.jpg

 

Here's an 826 (or 628) Meade mount.  I drilled and tapped a hole and added in a long bolt:

 

826 mount 01.jpg

 

The 826 mount fits perfectly onto the CG-5 hub:

 

826 mount on CG5 hub.jpg

 

I initially thought that the post on the CG-5 mount would interfere, but it doesn't.  It helps to stabilize the 826 mount.

I like it!  I wonder how my Meade StarFinder would do on a Mizar ShortPod (metal legs) or CX-153 (solid wood legs) carrying my Meade 826 OTA??  I want a fold-up solution before we leave The Swamp -- not gonna take any pedestal mounts to our next place... EXCEPT maybe just 1 for Displays.

[Garyth64]

I like my pedestals. I have the 4" x 24" pedestals and mounts for the 826s.  But these won't go to any outreach events because they are AC. (even though I have a converter for my battery.)

I have 5 other pedestals.  They are 4-1/2" cast iron and are 48", 37", 24", and 18".  Different heights for different scopes and mounts.  The 18" one I made last year when I put the 826 on my CGEM mount.  I've used the pedestals for my 5" refractor and an 8" CC I had with a CGEM mount.  The taller ones, with different mounts, I've used for my 3" refractors.

But they are heavy to put in and out of the back of the SUV.

So then I have my wood tripods.  They are different heights too.  Depends on the mount and scope I want to use.  The 5" refractor is right at home on a tripod with an old CG-5 mount.  The 5" will also ride well on the 826 mount on the tripod I used today, and very well on the CGEM.

Lately for outreach events, I've been using the 4' tripod with a CG-5 mount with one of the 3" refractors.

 

I have too much stuff.

Edited by Garyth64, 09 May 2025 - 03:16 PM.

[clamchip]

I was about to take my new ETX-90 outside when I noticed a small problem.

The eyepiece holder that sticks out of the control box was crooked. I said to

myself, "that's ugly, I hope it's nothing serious."

The eyepiece holder is aluminum and pressed into the plastic control box.

It would not budge with my paws so I placed a long 26mm Meade Super Plossl

in the holder and it give me the leverage I needed and torqued it back straight

again.

Something to remember when you go over one of these ETX, check the

eyepiece holder is on axis. I just happened to notice it.

The 26mm I mentioned above I just finished cleaning it. It came with the scope

and I decided to take it apart to look at the clamchip. The eyepiece has two

cemented doublets facing each other with a spacer between. Wouldn't you

know it, of all the rotten luck, a clamchip on each pair. This blow is what crooked

the eyepiece holder, and also destroyed the mount.

 

Robert

Edited by clamchip, 09 May 2025 - 03:40 PM.

[deSitter]

I was about to take my new ETX-90 outside when I noticed a small problem.

The eyepiece holder that sticks out of the control box was crooked. I said to

myself, "that's ugly, I hope it's nothing serious."

The eyepiece holder is aluminum and pressed into the plastic control box.

It would not budge with my paws so I placed a long 26mm Meade Super Plossl

in the holder and it give me the leverage I needed and torqued it back straight

again.

Something to remember when you go over one of these ETX, check the

eyepiece holder is on axis. I just happened to notice it.

The 26mm I mentioned above I just finished cleaning it. It came with the scope

and I decided to take it apart to look at the clamchip. The eyepiece has two

cemented doublets facing each other with a spacer between. Wouldn't you

know it, of all the rotten luck, a clamchip on each pair. This blow is what crooked

the eyepiece holder, and also destroyed the mount.

 

Robert

 

Yes I believe the back port is also pressed into the ABS plastic. It would probably be best to remove it completely and re-glue it.

 

-drl

[Bomber Bob]

I like my pedestals.

 

Me, too!  They're not as stable as my best tripods; but, for Displays, they have a smaller footprint.  I put a good bit of work into my Short & Tall Meade StarFinder pedestals, and I like that they are simple, cordless, with good visual tracking.  I can see bringing the Tall MSF indoors, and putting the Mogey 3" F14 on it; or, putting the Dakin 4" F10 on the MSF, and the Mogey on the Mizar KAISER (resembles some antique EQs).

 

Gonna part with my Mizar SP in the near future -- the Kenko NES is more capable.  I have the AR-1 on the ShortPod; and, it carried my RV-6 OTA -- barely.  I bet the CX-153's short fixed-height wood tripod could handle the 826 OTA + MSF.  My Goal is to hold on to the 826 for as long as I can set it up...