PrestonE
scholastic sledgehammer
Reged: 04/29/05
Posts: 799
Loc: Houston,Texas
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Hi guys,
For the baffold design go and get Mike Jones CassDesign free software. Plugin your parameters and it will spit out the exact baffold criteria...
Regards,
Preston
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A few I enjoy,
and a few more in the works ;<)
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Mike I. Jones
Pooh-Bah
Reged: 07/02/06
Posts: 1093
Loc: Fort Worth TX
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Check with Rich Simons at Star Instruments before buying to make sure they get you the field flattener that matches your mirror set. I'm the guy that started Star doing field correctors by sending Rich Simons several ZEMAX designs. He and Paul Jones (no relation we know of) bought ZEMAX, Rich learned how to use it with help from me, and they took it from there.
Field flatteners are not one-lens-does-it-all systems. They have to be matched to a particular set of mirrors. Paul probably still has the data files on your set of mirrors, so Rich would know which field flattener would be best for them. Their field flattener costs are low because the non-recurring optical and coating tooling costs have been paid for. A custom lens like Preston needs has to be done from scratch, thus driving up the cost.
Mike
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56 mirrors, lenses, 16" f/6 Newt, 6" f/10 refractor, TOA-130S, Tinsley 5" f/15 Mak, 6" f/4 RFT, Coronado PST. Still to build: 24" f/10 Modified Dall-Kirkham, 10" f/26 Mak, 8" f/12 apo, spectrohelioscope, Herrig, Schupmann, and a new design you'll like.
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PrestonE
scholastic sledgehammer
Reged: 04/29/05
Posts: 799
Loc: Houston,Texas
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Hi Mike, Thanks for giving an understanding...I had tought to say that you started them on the design path...but thought you would if you wanted...
Best Regards,
Preston
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A few I enjoy,
and a few more in the works ;<)
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jasonharris
super member
Reged: 09/16/06
Posts: 137
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Hi all, I played around with a collimation bolt tonight.
A friend pointed me to a chinese telescope making forum where I spotted this design, you may have come across it before but as I am a relatively new atm'er it is new to me.
It is a pushpull bolt where the outer bolt screws in to the telescope back and the mirror cell sits on top of it. The center bolt goes through the back of the mirror cell.
To adjust, you unscrew the center bolt slightly and then turn the outer bolt to either raise or lower the cell. Once done the center bolt is tightened to make sure that the cell is pulled back firmly to the main bolt. I hope this explanation makes sense!
An allen key is used to turn the center and I will need to make up a different key which will fit in the slot of the large bolt to turn it.
Jason
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The bear
professor emeritus
Reged: 02/11/08
Posts: 726
Loc: rushville, indiana
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interesting bolt i see possibilties
doc
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Longitude -85.42786 Latitude 39.59153
when all else fails use duct tape "works for me"
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jasonharris
super member
Reged: 09/16/06
Posts: 137
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Yes, it did look quite nice, hence I am playing with the design.
I used a 16mm bolt and put an 8mm bolt through the center. I think it should be quite rigid when everything is tightened, it give me a better feeling then the mirror cell sitting on a spring. I dont think rcos use this method but I do think astrosib have a similar bolt on thier line of RC's. Here is a picture of the scope I got the idea from, I hope he will not mind.
Thanks,
Jason
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GuyFleming
member
Reged: 01/21/08
Posts: 23
Loc: Newcastle, Australia
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nice bolt idea - thanks for sharing Jason.
Thanks also to Mike for the inside info re flatteners. I'll follow that up.
guy
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The bear
professor emeritus
Reged: 02/11/08
Posts: 726
Loc: rushville, indiana
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looks awesome i like that color he chose for it very micely understated and would not attract much heat very nice indeed.
doc
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Longitude -85.42786 Latitude 39.59153
when all else fails use duct tape "works for me"
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jasonharris
super member
Reged: 09/16/06
Posts: 137
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I thought I would post a picture of his bolt. It is actually a little difference as it is in three parts, I am keeping mine in two.
He has taken the outer bolt and chopped it in two, turning the head in to a key. The rest of the bolt is then turned in to a large grubscrew which is turned by the original head but moves in and out while the bolt head does not.
This is really for aesthetic reasons so the collimation bolt doesnt seem to move in and out from the telescope back.
I think when you get the length of the bolt right it is only going to move a couple of millimeters anyway so it wouldnt be too far from flush..
My telescope back is too thin to afford his design so I need to keep it as one.
Hope it was interesting for you!
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jasonharris
super member
Reged: 09/16/06
Posts: 137
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Well my pieces from the foundry have taken a little longer then expected. At least I have seen them all and they should be heat treated mid week and in my hands for the weekend..
I decided instead to work on my router table. I started many months ago and just did the top. I decided this weekend I would finish it so I did a base, now I just need a door and drawers. So while it's not a telescope it is a valuable telescope building tool 
Jason
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jasonharris
super member
Reged: 09/16/06
Posts: 137
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OK, now I have finished building router tables I got a call to pick up my castings today !!
They are pretty heavy and a lot is going to come off with the machining. I knew this was going to happen but they were my first patterns to be cast and I didnt want to get too fancy ending up with something that cast a bit ugly because of my inexperience..
In the picture above next to the router table you can see a 16" faceplate for the lathe. It may be to small to mount one of the pieces on so I may have to get a 20" faceplate for this project..
They look a bit ugly now but as they are t6 ehat treated 6061 it will machine very nicely. I cant wait to take the surface off
Jason
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jasonharris
super member
Reged: 09/16/06
Posts: 137
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and..
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jasonharris
super member
Reged: 09/16/06
Posts: 137
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ok, so I couldnt help myself. Why wait until tomorrrow morning when I can just have a late dinner...
I put the back plate on and faced it off. I just need to bore out the center a little then I can face off the other side and put it on the mill to do the outside on the rotary table.
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PrestonE
scholastic sledgehammer
Reged: 04/29/05
Posts: 799
Loc: Houston,Texas
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Quote:
OK, now I have finished building router tables I got a call to pick up my castings today !!
They are pretty heavy and a lot is going to come off with the machining. I knew this was going to happen but they were my first patterns to be cast and I didnt want to get too fancy ending up with something that cast a bit ugly because of my inexperience..
In the picture above next to the router table you can see a 16" faceplate for the lathe. It may be to small to mount one of the pieces on so I may have to get a 20" faceplate for this project..
They look a bit ugly now but as they are t6 ehat treated 6061 it will machine very nicely. I cant wait to take the surface off
Jason
Hi Jason,
Ugly??? They are beautiful, and just think how much machine work you saved by haveing these cast first...
What does he charge per pound to cast the aluminum and then heat treat it for you??? If you don't mind my asking.
Great looking machine work also...
Best Regards,
Preston
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A few I enjoy,
and a few more in the works ;<)
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jasonharris
super member
Reged: 09/16/06
Posts: 137
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Thanks Preston. The guy charges me $22 new zealand dollars per kilo which is ~$7.8USD per pound. This includes everything fromthe point he takes the pattern and hands you back the heat treated cast.
its a lot cheaper then plate when you only get what you need.
\Jason
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JanM
professor emeritus
Reged: 03/07/05
Posts: 626
Loc: Sheffield UK
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Looking good Jason, glad to see work has resumed. Interesting idea regarding the collimation screws thanks for sharing that.
Jan
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- AP 130 EDF
- Trifid-2 SA-6303E-C2, SXV-M7
- AP 900 GTO3
- Observatory Progress - Just the roof left
Website - http://www.pbase.com/janmclare/
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PrestonE
scholastic sledgehammer
Reged: 04/29/05
Posts: 799
Loc: Houston,Texas
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Hi Jason,
Replying from Amsterdam...Those prices are similar to our USA prices...
A Good friend and I spent almost 3 weeks in northern Mexico down toward Mexico city, looking at out sourcing castings and machine work...
We purchased property and are starting a business subcontracting parts made...
We just had 5 gray iron parts that were 10 kg each and paid US$1 per pound or about US$22 each...
Locally, they...if they, because of the oil bussiness in Houston...will give you a bid on castings or machine work...
It's 5 times the price and 9 months away....
Thus the reason for us looking in Mexico...
Still Looking very good...
Best Regards,
Preston
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A few I enjoy,
and a few more in the works ;<)
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jasonharris
super member
Reged: 09/16/06
Posts: 137
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Thanks Jan, hopefully I can keep up the momentum for a while.
Preston, next time I will make my patterns a lot closer to the final product. I would probably save 30% of the cost of the casting this way and even less machining to do..
Yesterday I got the sides of the backplate parallel and started to mill out for the fans..
I am mostly designing as I go so I need to figure out how I want to attach the camera/focuser on the back so I can drill and tap out some holes while it is all centered.
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GuyFleming
member
Reged: 01/21/08
Posts: 23
Loc: Newcastle, Australia
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Hi Jason
How do you find the turntable for those circular cuts with the mill? I say this because an experienced machinist I know did not recommend them for continous circular cuts with the mill. I assumed they can do a reasonable cut as long as the job is positioned well, secured and not rushed. It still looks ideal for a few circular cuts I need to make.
cheers, guy
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jasonharris
super member
Reged: 09/16/06
Posts: 137
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Hello Guy, well I guess it depends on what you want to use it for and if you try to overuse it.
My table is a 10" rotary table so my backplate hangs over it a bit. Its about as large as I would want to go on this table for this.
I only used it to do the milling on the outer edge where I couldnt do this on the lathe because of the four protruding edges. It was ok, the only thing your cutter will fight with is any backlash on the table. Make sure you are turning th table so that the worm is always driving the gear positively. If not you coould have some problems.
For the three circles for the fans I had these made in the pattern. To finish them I will use a boring head rather then the table.
I have since taken it off the table and put it back on the lathe to reduce the width of the outer ring. This would have been hard work on the rotary table and the finish would not have been as nice.
Your friend is right, if you have a lathe that will handle the job then its the best way. If you dont then it's a pretty reasonable alternative if you dont push it.
Jason
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