FC100DC with Binoviewers, no barlow

[marcus_z]

14 hours ago, Stu said:

I wonder if this section is removeable on the DC focuser?

Yes, it is removable! That's the extension I meant. I have to correct myself. It's 55mm long. Just unscrew it.

[Stu]

2 minutes ago, marcus_z said:

Yes, it is removable! That's the extension I meant. I have to correct myself. It's 55mm long. Just unscrew it.

Very handy, we might just have saved Mike the cost of a FeatherTouch

Anyway, two Taks met in the pub tonight, but I can't think of a punchline  

It seems that the proper adaptor, the A20-304 (I think!) is even shorter than mine, the 302. I think I prefer keeping the silver ring on the scope, but Gavin's does look rather shapely  

[Piero]

9 hours ago, Stu said:

Very handy, we might just have saved Mike the cost of a FeatherTouch

Anyway, two Taks met in the pub tonight, but I can't think of a punchline  

It seems that the proper adaptor, the A20-304 (I think!) is even shorter than mine, the 302. I think I prefer keeping the silver ring on the scope, but Gavin's does look rather shapely  

 

Okay, so... why did you two have your Taks in the pub?   Did they also want a pint?  

[GavStar]

18 minutes ago, Piero said:

 

Okay, so... why did you two have your Taks in the pub?   Did they also want a pint?  

Unfortunately it was cloudy so we had a pint. For some reason it seemed a good idea at the time to compare focusers ?

Hopefully they will both be used in their proper role for our club trip this evening to a dark site.

[Stu]

24 minutes ago, Piero said:

 

Okay, so... why did you two have your Taks in the pub?   Did they also want a pint?  

It was a meeting of our Astro group, very civilized place to hold it I think  

Not both mine unfortunately, Gavstar owns the other one and we did discuss making a binocular out of them  

[Peter Drew]

1 hour ago, Stu said:

It was a meeting of our Astro group, very civilized place to hold it I think  

Not both mine unfortunately, Gavstar owns the other one and we did discuss making a binocular out of them  

[mikeDnight]

11 hours ago, marcus_z said:

Yes, it is removable! That's the extension I meant. I have to correct myself. It's 55mm long. Just unscrew it.

Just wondering if by removing the spacer and moving the rack and pinion focuser nearer the tube, would the narrower DC drawtube cut into the light path?

[Piero]

2 hours ago, mikeDnight said:

Just wondering if by removing the spacer and moving the rack and pinion focuser nearer the tube, would the narrower DC drawtube cut into the light path?

I don't think this is a problem because the drawtube of this "DC shorty" will be out (and extended using extension tubes) to reach focus. 

How long is the DC drawtube? I think it is shorter than the DF (2.7"). We can measure the difference between this "DC shorty" and DF focuser and compare the length of drawtubes. 

Edit: see below

[Piero]

13 hours ago, marcus_z said:

Yes, it is removable! That's the extension I meant. I have to correct myself. It's 55mm long. Just unscrew it.

@Stu's measurements: "The full Tak focuser including extensions is  257mm to the end of the 1.25" adaptor. With the extensions removed and in 1.25" mode, it is 187mm to the end of the 1.25" adaptor"

=> The DC reduced Tak focuser with the extensions removed and in 1.25" mode, it is 132mm to the end of the 1.25" adaptor 

 

 

My measurements: "15cm, from the beginning of the focuser to the 1.25" adapter. 10.5cm if used in 2" mode."

DC drawtube length: 56mm (2.2")  (https://www.optcorp.com/takahashi-fc-100dc-f-7-4-fluorite-refractor-ota-fc-100dc.html)

DF drawtube length: 69mm (2.7")  (https://www.optcorp.com/takahashi-fc-100df-f-7-4-fluorite-refractor-ota-tfk-10110.html) 

=> The DC reduced Tak focuser without extension and in 1.25" mode is ~18mm (=150-132) shorter than the DF focuser in 1.25" mode.

=> The DC reduced drawtube will enter for an extra 5mm (=56+18 - 69) compared to the DF, when fully retracted.

If the maths is correct, I think you won't have issues at all with 1.25" eyepieces. Possibly no vignette with 2" eps either.

 

[mikeDnight]

Well I've done it and it still won't reach focus without a Barlow. It's almost there but the distant horizon is out of focus. Perhaps I could get a little more in-focus if I used the 2" adapter but I'd need a low profile 2" to 1.25" insert and I don't have one.

After all this jiggerypokery, I'm still wondering just how advantageous a binoviewer is going to be at low power? I'd rarely ever use it on dso's, or would I!?

[Stu]

That's a shame Mike. I guess with the Tak focuser you still end up losing backfocus to the adaptors whereas you can go straight into the FT with a 2" or 1.25" barrel.

Can you somehow lose the 1.25" parts and just get a 2" adaptor for the focuse and add a low profile 1.25" to 2" adaptor to the diagonal?

I only viewed a few objects when I tried it out, the conditions weren't good enough to reach a strong conclusion, will try again at the next opportunity.

[mikeDnight]

4 minutes ago, Stu said:

That's a shame Mike. I guess with the Tak focuser you still end up losing backfocus to the adaptors whereas you can go straight into the FT with a 2" or 1.25" barrel.

Can you somehow lose the 1.25" parts and just get a 2" adaptor for the focuse and add a low profile 1.25" to 2" adaptor to the diagonal?

I only viewed a few objects when I tried it out, the conditions weren't good enough to reach a strong conclusion, will try again at the next opportunity.

I could probably gain a further 20mm or so in-focus using my 2" adapter and a SW low profile 2" to 1.25 fit adapter. That would probably do it! I don't have the SW adapter but a know a nice man who has two, and he may lend me one.

As it stands I can still use all my eyepieces and binoviewer (with barlow), using the long extension tube supplied with the telescope for direct viewing. ?

[F15Rules]

On 8/16/2017 at 22:31, mikeDnight said:

Thanks Gavin & Stu. I'll have to psych myself up to invest in a FT. 

...or give Peter Drew a call

That's actually exactly what I did with my D&G F15 refractor..or rather, I got Moonraker to chop 130mm off the tube. Mind you, the tube was almost 2m long, so losing 5" off of that was quite welcome. It came to perfect focus with bvs in the Moonlight focuser I also installed, and I only ever needed an extension rarely for mono viewing, I think only 50mm at that.

But I'm not sure I'd do that to my FS128 tube though!

Dave

[F15Rules]

6 hours ago, Stu said:

It was a meeting of our Astro group, very civilized place to hold it I think  

Not both mine unfortunately, Gavstar owns the other one and we did discuss making a binocular out of them  

Now Peter Drew will be getting REALLY excited!

Dave

[Piero]

2 hours ago, mikeDnight said:

I could probably gain a further 20mm or so in-focus using my 2" adapter and a SW low profile 2" to 1.25 fit adapter. That would probably do it! I don't have the SW adapter but a know a nice man who has two, and he may lend me one.

As it stands I can still use all my eyepieces and binoviewer (with barlow), using the long extension tube supplied with the telescope for direct viewing. ?

 

The telescope looks very nice! It's a "Light DC/F" now!   

 

I just noticed that the Tak clamshell and focuser match with the colour of your kitchen!   

[mikeDnight]

1 hour ago, F15Rules said:

...or give Peter Drew a call

That's actually exactly what I did with my D&G F15 refractor..or rather, I got Moonraker to chop 130mm off the tube. Mind you, the tube was almost 2m long, so losing 5" off of that was quite welcome. It came to perfect focus with bvs in the Moonlight focuser I also installed, and I only ever needed an extension rarely for mono viewing, I think only 50mm at that.

But I'm not sure I'd do that to my FS128 tube though!

Dave

Hi Dave,

It could just be me, but chopping a Tak down would be sacrilege in my eyes. Once that beautiful tube has been butchered it becomes valueless to me, and I suspect many would feel the same way. All Taks sooner or later become collectable and hold their value very well, so it would be criminal to defile their beauty. But I know a man who would merrily take a hacksaw to it! ??

Your FS128 is a true classic. Keep it away from Peter! ?

[mikeDnight]

1 hour ago, Piero said:

 

The telescope looks very nice! It's a "Light DC/F" now!   

 

I just noticed that the Tak clamshell and focuser match with the colour of your kitchen!   

DC/F 

The kitchen walls are 'Wild Sage' or something like that. It must have been a subconscious thing, but its so close to the Tak green that if the scope didn't have a white tube I'd never find it. 

[Moonshane]

This is where T2  connectivity of the Baader systems come into their own.

[mikeDnight]

59 minutes ago, Moonshane said:

This is where T2  connectivity of the Baader systems come into their own.

Would you care to elaborate Shane? And, is it going to cost me?? 

[Moonshane]

Sure Mike. With the Baader Maxbright binoviewers and a T2  diagonal you could reduce your light path substantially. I lost about 80-90mm  on my pst mod allowing me to use the 1.7x  glasspath corrector rather than the 2.6x. It also allows me to get full disk at 70-100x. There are some pics in this thread. Not a cheap option though albeit effective.

 

 

 

[paulastro]

22 hours ago, mikeDnight said:

Would you care to elaborate Shane? And, is it going to cost me?? 

If you recall Mike, my new prism is a Baader T2 fitting and connects directly to the Baader Maxview Binoviewer after removing the 1.25/helical focus thingy from the front end. Hence, can use my  binoviewer without needing to use a barlow or other corrector.

[Stu]

It's a very good point, and my Baader Mark IVs also have a flange at the base allowing m to connect directly to a T2 Mirror or Prism by using one of the T2 Quickchanger rings. As Shane says, it does save a lot of optical path length.

[paulastro]

Sorry folks, should have mentioned I use a DL not a DC.

[Peter Drew]

On 8/18/2017 at 18:11, mikeDnight said:

Hi Dave,

It could just be me, but chopping a Tak down would be sacrilege in my eyes. Once that beautiful tube has been butchered it becomes valueless to me, and I suspect many would feel the same way. All Taks sooner or later become collectable and hold their value very well, so it would be criminal to defile their beauty. But I know a man who would merrily take a hacksaw to it! ??

Your FS128 is a true classic. Keep it away from Peter! ?

SW, Tak, Tasco, AP, Seben, Meade, it's jus another tube to me. As long as it makes a practical improvement, "off with its head".     

[Moonshane]

Don't you mean off with it's rear? ?