103 replies to this topic

[jrazz]

I just placed an order for the second OTA so...

[Scott99]

I just placed an order for the second OTA so...

wow....great idea.  So how do you deal with the mechanics?  Are you going to order the special prism diagonals for them?   For me to try a binoscope I think it would have be something like two Tak FC100's

[TEK]

I've seen Kunama's photo before and was very envious.

 

For reference, here are the online weights for the various bare OTAs that have been mentioned:

 

FC-100DF --- 8.6 lb  (DC is a bit lighter but by the time you add a Feathertouch it's probably closer to a DF)

TSA-120 --- 14.7 lb

TOA-130 --- 27.1 lb 

FS-152 --- 23.0 lb

 

TSA really does hit a sweet spot for aperture vs weight.  I absolutely love mine.

 

For the ultimate lightweight binoscope, the DF starts to make more sense though.

Edited by TEK, 18 September 2024 - 01:34 PM.

[Souldrop]

I just placed an order for the second OTA so...

Im looking forward to reading/seeing updates! Should be a pretty amazing setup imo

[ris242]

   

 

Sell you DC, buy a DZ, or a TSA 120 which you get with a FT focuser already fitted.  https://www.firstlig...08-adapter.html

Over 5000 quid for a TSA?

 

I would be tempted to sell everything and get a TEC 140 instead.

[John Huntley]

My TOA-130 is staying, but my APM LZOS 130mm F6 might be up for sale to go toward buying a night vision device. I am glad you found a buyer John, UK ABS has some great refractors that stay unsold for ages.

I'd had two people interested in the scope for over a year, both of whom kept in touch in case I decided to part with it. They approached me in the 1st instance so I didn't need to advertise it. I met the new owner when I delivered the scope and we chatted for a couple of hours over coffees etc. It is good to know that the instrument is with an new owner who appreciates it and will use it 

[jrazz]

wow....great idea.  So how do you deal with the mechanics?  Are you going to order the special prism diagonals for them?   For me to try a binoscope I think it would have be something like two Tak FC100's

I ordered a set of EMS which would take care of that.

More concerning is the backfocus needed. Not sure how I'll handle that yet. I'd love to keep the focusers as they are. Might need to shorten something though.

[Souldrop]

I ordered a set of EMS which would take care of that.
More concerning is the backfocus needed. Not sure how I'll handle that yet. I'd love to keep the focusers as they are. Might need to shorten something though.

If you remove the green section between the focuser and the ota you should be fine with a short visual back. Things may be tight if you got the ULs with helicoids.

[jrazz]

Can I just remove it? Is it the same thread?

That would be super awesome.

 

I have a feeling I might need to replace the focusers.

 

 

Scratch that, it's totally removable! Thanks!!! This means I probably won't need to replace the focusers... Unless the tube vignettes badly and then I'm back to square 1.

Edited by jrazz, 18 September 2024 - 07:20 PM.

[Souldrop]

If my measurements of the dc focuser are close and my math is right you need right at 17” between the objective cell and the threads of the focuser to ensure no vignetting. Even if you have some vignetting I personally would wait until you had some time on it to see how noticeable any vignetting may be in use.

ETA: above number assumes focuser is racked all the way in.

Edited by Souldrop, 18 September 2024 - 07:55 PM.

[jrazz]

I think you beat me to it.

 

It should be fine as I see it... Worst case I buy some FT focusers... Woe me.

Honestly, I might even slum it and get GSO focusers

 

 

Yeah, if I can keep the DC focusers I'll be a very happy camper!

 

Thank you! This is awesome help!

[norvegicus]

Oh my.  I will probably replicate this, or approximate it.  How are you building the cradle?

[RAKing]

Thinking about upgrading the focuser... I recently sold the TOA (very happy about that) but now I want to make the DC the best telescope for me.

 

I am completely lost with the options in the Feather Touch lineup. Any recommendations? I want to keep the optical path short to allow a possible future EMS binoscope.

 

I am sorry you sold your TOA, but I sold mine for the same reason, so I understand why you did it.  I have a beautiful FC-100DC and upgraded it to an FT focuser a few years ago.  I bought the less-expensive DC model because I was planning to upgrade the focuser from the start.  It works great and I think you have a good plan.

 

I do have an extra 1" FT Riser in my focuser train.  I was worried about the 2.5" focuser clipping the light path, but it worked out okay.  If you remove the riser, you might want to try the FTF2020BCR focuser instead.  You should still have plenty of drawtube travel with the 2-inch drawtube.  I use a 1.25x Baader GPC in my BV unit and it works fine with the FT setup I have.

 

The FT is a great addition to the Tak and makes this little jewel a world-class instrument!

 

Ron

 

 

[jrazz]

Oh my.  I will probably replicate this, or approximate it.  How are you building the cradle?

Clue: PPA+CF

[norvegicus]

Clue: PPA+CF

I thought that might be the case.  I will use PC+CF if I do this.   Should be stiff enough, and so cheap to do, and we can add custom ginsu stuff...

[Lagrange]

Over 5000 quid for a TSA?

 

I would be tempted to sell everything and get a TEC 140 instead.

A TEC 140 is £9200 over here so it's a big step up in cost from even the UK price of the TSA-120.

 

If I was in the market for a TSA I'd probably buy it from the Far East for half the price.

[Deadlake]

Clue: PPA+CF

As anyone tried building a carbon cradle to keep the weight down?

[jrazz]

That's part of what I'm trying to achieve. I'm using an aluminum Losmandy plate with 3D printed rings. Should be pretty light. FEA tells me it should be plenty stiff - similar to aluminum rings in fact and hopefully more temperature stable. Not sure about final geometry yet. I'll post somewhere here once I figure it out.

[Scott99]

That's part of what I'm trying to achieve. I'm using an aluminum Losmandy plate with 3D printed rings. Should be pretty light. FEA tells me it should be plenty stiff - similar to aluminum rings in fact and hopefully more temperature stable. Not sure about final geometry yet. I'll post somewhere here once I figure it out.

So you're just going to mount the two OTA's on a big plate next to each other and use the EMS diagonals to position the eyepieces....interesting

[jrazz]

No, there's going to be some 3D printed structure/cradle there to hold them together. The plate is the backbone. There's also a 1" aluminum rod used as a handle as well. I'm not completely happy with my design yet. Still need to perfect it.

[Scott99]

No, there's going to be some 3D printed structure/cradle there to hold them together. The plate is the backbone. There's also a 1" aluminum rod used as a handle as well. I'm not completely happy with my design yet. Still need to perfect it.

very interesting!   Maybe there's a business opportunity there?    If it turns out well, you could go into production......I never thought about it, but these DC refactors are ideal for this.  The ultra-light weight is just what you'd want to make a manageable bino-scope and 4 inches is a good size - should be as bright as 5-incher refractors on DSO's I would think.

Edited by Scott99, 19 September 2024 - 02:21 PM.

[jrazz]

Yeah, I've long ago decided that I will share my 3D printed designs. I don't have the patience to make a business out of if

 

I absolutely love my FC-100DC. Roger Vine said it's the best value and I think he's absolutely right. If my BT-100XL/SD is anything to go by, this should be really good.

 

I should say I'm far from the first person to make a bino-scope out of these. Maybe I'm different because I prefer the DC to the DF or DZ but honestly, you could just as easily take an AT EDL or EDT 102 and make a killer binoscope. The most important part is the erecting diagonals. 

[Highburymark]

No, there's going to be some 3D printed structure/cradle there to hold them together. The plate is the backbone. There's also a 1" aluminum rod used as a handle as well. I'm not completely happy with my design yet. Still need to perfect it.

Good luck - look forward to hearing how you get on. Do you expect to be able to use them at single DC magnifications - ie, at 200x and above on the planets and Moon on good nights, or might collimation issues compromise things? It’s probably clear already that I don’t know anything about binocular telescopes, though I know the smaller, faster APM-type instruments have more modest maximum powers.

[jrazz]

The EMS erecting systems allow for on the fly adjustment which solves the main problem of high magnification binoculars: collimation.

I certainly hope I’ll be able to use them up to 300x. That’s my goal.

[Scott99]

The EMS erecting systems allow for on the fly adjustment which solves the main problem of high magnification binoculars: collimation.

I certainly hope I’ll be able to use them up to 300x. That’s my goal.

it sounds very cool - didn't I read that the EMS diagonals are being discontinued?  This may be the last chance to do this. 

 

Wasn't there a small astronomy company making binoscopes on request out of any telescopes?  in New Jersey I think?  And then they went out of business some years ago.  It looks like TEC will make you a binoscope as well, but only large and expensive ones given their smallest model is a 140FL...here's TEC"s page -

 

https://www.telescop...lar-telescopes/

Edited by Scott99, 19 September 2024 - 01:01 PM.