Build your own ? (1 Viewer)

thornlv · Oct 6, 2010

I wonder how easy it would be to build your own scope. The design does seem quite simple, a tube, the objective glass and the focuser. 2 of these components can be bought 'off the shelf' as it were (optics, focuser)

Or perhaps if you could have some extension on the ED80's tube, as I feel there is always too much strain on ext tubes when at minimum focus.I guess there is always a 'optimum range' that you would work to for min/max focus.

If you built your own you could design it to your own required specs.

alphan · Oct 7, 2010

thornlv said:
I wonder how easy it would be to build your own scope. The design does seem quite simple, a tube, the objective glass and the focuser. 2 of these components can be bought 'off the shelf' as it were (optics, focuser)

Or perhaps if you could have some extension on the ED80's tube, as I feel there is always too much strain on ext tubes when at minimum focus.I guess there is always a 'optimum range' that you would work to for min/max focus.

If you built your own you could design it to your own required specs.

Good idea. Unless you could make the extended tube as easily removable for portability and weight. Perhaps a bigger objective lens in front with an extension main tube going forward.

chris butterworth · Oct 7, 2010

thornlv said:
I wonder how easy it would be to build your own scope.

Theoretically it should be a piece of cake, but, practically - thats another matter ( alignment of the internal components would be a real headache )
I must admit that some things do sound fairly straight forward at first but then reality steps in.

Chris

p.s. If you do manage to "knock one up" don't forget to let us know :t:

C

Paul Corfield · Oct 7, 2010

Lots of people make their own refractors and there's not a lot to it. I used to make my own out of large diameter cardboard tubes and they always performed very well. There's some astronomy forums around and they have sub forums on the subject of telescope building. Get hold of a length of aluminium tube (cheap on ebay), flock the tube, add some baffles, a lens cell, a crayford focuser and assemble it.

Paul.

chris butterworth · Oct 8, 2010

Paul Corfield said:
Lots of people make their own refractors and there's not a lot to it. I used to make my own out of large diameter cardboard tubes and they always performed very well. There's some astronomy forums around and they have sub forums on the subject of telescope building. Get hold of a length of aluminium tube (cheap on ebay), flock the tube, add some baffles, a lens cell, a crayford focuser and assemble it.

Paul.

As I said " piece of cake". Lets have a look at it when you've finished. Better still see if you can digi-scope with it.
Good Luck, Chris

Paul Corfield · Oct 8, 2010

chris butterworth said:
As I said " piece of cake". Lets have a look at it when you've finished. Better still see if you can digi-scope with it.
Good Luck, Chris

There's a lot of photos in my gallery digiscoped with a cardboard tube refractor. I don't have to try and prove anything. Here's an example taken early in 2006 with a 50mm achromatic cemented doublet mounted in a cardboard tube, digiscoped through an eyepiece with an Oly C5050.

Paul.

alphan · Oct 9, 2010

Paul, how I wish Achromat scopes can always take nice crisp pics like that. Then I can order a bigger achromatic lens cell with higher FL and Objective to DIY my own refractor. Non ED lenses are so cheap compared to ED. Then I save on the hefty shipping cost and local sales Tax. I do harbor hope of getting an 8" mirror for DIY, not for birds but looking upwards.

Paul Corfield · Oct 9, 2010

alphan said:
Paul, how I wish Achromat scopes can always take nice crisp pics like that. Then I can order a bigger achromatic lens cell with higher FL and Objective to DIY my own refractor. Non ED lenses are so cheap compared to ED. Then I save on the hefty shipping cost and local sales Tax. I do harbor hope of getting an 8" mirror for DIY, not for birds but looking upwards.

Decent achromats take sharp enough photos, the only problem with an achromat is the chromatic aberrations.

On ebay an ED or slightly better 3 element apochromatic lens cell will be quite cheap, well under half what you would pay for a scope containing the same lens cell.

This 106mm Apo triplet here for example, only £435 which is a bargain I think.

Paul.

Musoman · Oct 9, 2010

alphan said:
Paul, how I wish Achromat scopes can always take nice crisp pics like that. Then I can order a bigger achromatic lens cell with higher FL and Objective to DIY my own refractor. Non ED lenses are so cheap compared to ED. Then I save on the hefty shipping cost and local sales Tax. I do harbor hope of getting an 8" mirror for DIY, not for birds but looking upwards.

Alphan, heres a fascinating bit of reading for you on Achro and Apo

http://www.brayebrookobservatory.org/BrayObsWebSite/HOMEPAGE/forum/Apo_vs_Achro.html

chris butterworth · Oct 9, 2010

Paul Corfield said:
There's a lot of photos in my gallery digiscoped with a cardboard tube refractor. I don't have to try and prove anything. Here's an example taken early in 2006 with a 50mm achromatic cemented doublet mounted in a cardboard tube, digiscoped through an eyepiece with an Oly C5050.

Paul.

Didn't mean it like that Paul ( alright, I may have been a LITLE bit sarky :t: ).
Excellent photo, and I stand humbled. Makes you wonder what the hell we've been paying out all that hard earned for!

Chris

alphan · Oct 11, 2010

Paul Corfield said:
Decent achromats take sharp enough photos, the only problem with an achromat is the chromatic aberrations.

On ebay an ED or slightly better 3 element apochromatic lens cell will be quite cheap, well under half what you would pay for a scope containing the same lens cell.

This 106mm Apo triplet here for example, only £435 which is a bargain I think.

Paul.

That one you link there, I too belief it's a good buy, but having just burnt a hole in my pocket, changing from MF Mirror tele to 200-500 Zoom and now the 80ED, I don't even dare look at the Triplets. May even get murdered for it LOL.

How much more improvement can you get between a ED double and Apo Triplet? Perhaps you will call it the cream of the cake, that's what makes cake a cake.

Musoman, thanks for the link. Just toying idea of a DIY build, in which case, will only try a achromatic lens beaten up with plastic pipes etc. If sucessfaul (which shouldn't be too hard), can try shooting at the nearby jungles.

etudiant · Oct 11, 2010

Skillful people with spare time can build excellent optical equipment at very low materials cost.
The full cost however should factor in the time spent, including planning and preparatory setup. Typically, that translates into a well below minimum wage equivalent, so these efforts are mostly hobbies or labors of love. No one else can afford the savings.

Paul Corfield · Oct 11, 2010

alphan said:
That one you link there, I too belief it's a good buy, but having just burnt a hole in my pocket, changing from MF Mirror tele to 200-500 Zoom and now the 80ED, I don't even dare look at the Triplets. May even get murdered for it LOL.

How much more improvement can you get between a ED double and Apo Triplet? Perhaps you will call it the cream of the cake, that's what makes cake a cake.

Musoman, thanks for the link. Just toying idea of a DIY build, in which case, will only try a achromatic lens beaten up with plastic pipes etc. If sucessfaul (which shouldn't be too hard), can try shooting at the nearby jungles.

You wont see a great deal improvement between the 80ED and a triplet and it's not the thing that attracts me to that lens on ebay. It's mainly the lens diameter and focal length that would be a nice step up from the 80ED.

For cheap achromats already mounted in plastic lens housings you can try Surplus Shed. I've tried a few of their lenses in the past and they suffer a bit with CA as far as photography goes but they are cheap for the size. OK for viewing with though.

Paul.

alphan · Oct 12, 2010

etudiant said:
Skillful people with spare time can build excellent optical equipment at very low materials cost.
The full cost however should factor in the time spent, including planning and preparatory setup. Typically, that translates into a well below minimum wage equivalent, so these efforts are mostly hobbies or labors of love. No one else can afford the savings.

I wonder why DIY or ATM are always more costly if not similar cost. But I will still try it one day for a few reasons:
1) shipping cost saving. The saving itself would buy me the tube with machining locally and a reasonable focuser.
2) DIY is in my blood, labor of love
3) different learning curve

alphan · Oct 12, 2010

Paul Corfield said:
You wont see a great deal improvement between the 80ED and a triplet and it's not the thing that attracts me to that lens on ebay. It's mainly the lens diameter and focal length that would be a nice step up from the 80ED.

For cheap achromats already mounted in plastic lens housings you can try Surplus Shed. I've tried a few of their lenses in the past and they suffer a bit with CA as far as photography goes but they are cheap for the size. OK for viewing with though.

Paul.

Any ED or Apo above 80mm are so costly and can really push me back. But if a good Achromat give a not too bad CA, then we can still use PP to handle it. A little bit more work but a nicer picture LOL

Smithhill · Oct 16, 2010

Lenses for Fab Scopes

Thronlv

In comparing the quality and cost of different lenses for telescopes an important consideration is the speed of the lens. The triplet sold by “great-eye” on e-Bay is f- 6.6. I am happy with the view from my f-7.5 80ED scope from Orion. I have attached an image from my first scope that was a fabricated 74mm f-8 achromat. The “IStar” site is selling quite a range of quality lenses in both quality specification and f-number. For example, people in astronomy many times prefer a large size achromat of perhaps 6 or 8 inches and speeds as low as f-12 or f-15 in order to get great magnification and sharp views. An Apo of that size would be many times more costly and offer little more in quality.

The reputation of the lens maker is also important. For example, the Jaegers Co. was well known for the quality of its lenses. Unfortunately their factory burned down in about 1970 and was not rebuilt. The lenses are still being sold however. I have a 4” f-8 that is about to be make into a scope.

Another consideration is if a lens cemented or air-spaced. The latter incorporates corrections for a flatter field that is not possible with a cemented lens. Of course good baffling is important in a scope to give contrasty views. Provision needs to be made for controlled collimation. Push-pull adjustment screws are fine. Some times they are provided in the mount. I suggest a collimation eyepiece such as sold by ScopeStuff. It has a frosted 45 deg. angle mirror to reflect outside light. Much easier to use than a laser.

So, in choosing a telescope lens be careful not to get one faster than the design allows for sharp seeing. The cost of the achromat used in the following digiscoped image was $10 from Surplus Shed, but I had to separate and re-cement it. Gene

http://www.PhotoShare.co.nz/PhotoShareGallery1/101684/109654/Q-EMa15B0171543_L.jpg

alphan · Oct 18, 2010

Smithhill said:
Thronlv

In comparing the quality and cost of different lenses for telescopes an important consideration is the speed of the lens. The triplet sold by “great-eye” on e-Bay is f- 6.6. I am happy with the view from my f-7.5 80ED scope from Orion. I have attached an image from my first scope that was a fabricated 74mm f-8 achromat. The “IStar” site is selling quite a range of quality lenses in both quality specification and f-number. For example, people in astronomy many times prefer a large size achromat of perhaps 6 or 8 inches and speeds as low as f-12 or f-15 in order to get great magnification and sharp views. An Apo of that size would be many times more costly and offer little more in quality.

The reputation of the lens maker is also important. For example, the Jaegers Co. was well known for the quality of its lenses. Unfortunately their factory burned down in about 1970 and was not rebuilt. The lenses are still being sold however. I have a 4” f-8 that is about to be make into a scope.

Another consideration is if a lens cemented or air-spaced. The latter incorporates corrections for a flatter field that is not possible with a cemented lens. Of course good baffling is important in a scope to give contrasty views. Provision needs to be made for controlled collimation. Push-pull adjustment screws are fine. Some times they are provided in the mount. I suggest a collimation eyepiece such as sold by ScopeStuff. It has a frosted 45 deg. angle mirror to reflect outside light. Much easier to use than a laser.

So, in choosing a telescope lens be careful not to get one faster than the design allows for sharp seeing. The cost of the achromat used in the following digiscoped image was $10 from Surplus Shed, but I had to separate and re-cement it. Gene

http://www.PhotoShare.co.nz/PhotoShareGallery1/101684/109654/Q-EMa15B0171543_L.jpg

Nice shot there. What achromat did you use for it. Apo or ED with bigger objective and FL always cost sky high. I was hoping to get a good achromat with higher FL to do controlled bird shots and get photoshop to take care of the CA.

What site is "IStar"?

Paul Corfield · Oct 18, 2010

alphan said:
What site is "IStar"?

Visit http://www.istar-optical.com/beta1/index.html

Paul.

Aegea · Oct 18, 2010

Paul (or anyone!)

Any comments on how a slow achromat (say f/10 or greater) would perform if used with a focal length reducer, particularly with respect to CA? I'm thinking of your comment about the use of the Miranda objective + Kenko TC in the thread on alternatives to barlows. I expect there's no free lunch, but I'd be delighted to discover otherwise.

Paul Corfield · Oct 18, 2010

Aegea said:
Paul (or anyone!)

Any comments on how a slow achromat (say f/10 or greater) would perform if used with a focal length reducer, particularly with respect to CA? I'm thinking of your comment about the use of the Miranda objective + Kenko TC in the thread on alternatives to barlows. I expect there's no free lunch, but I'd be delighted to discover otherwise.

I think the only good focal reducers are the ones that are designed specifically for a certain scope. The generic ones work but might not be sharp across the whole field of view.

My Miranda lens works quite well and the whole field of view looks flat but the sharpness isn't perfect. I tried it with a barlow today and I got the similar effect of reduction in the scopes focal length. If you don't crop the photo then it's perfectly acceptable but at 100% there is a slight loss in resolution. I'll post up some examples in the next day or so. Don't know how it would affect CA though.

Paul.

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