Tak FC-100 - a few questions :)

[Highburymark]

I was a bit surprised when I received the Tak micro focuser for my FC-100DC. It's a very rudimentary package, particularly considering its price. But once fitted it is a very valuable tool and works well - particularly at high magnification. 

I bought my FC from Lee at Green Witch - excellent service and a nice guy too.

[John]

5 minutes ago, jabeoo1 said:

Thats handy, well I will double check the zoom in the 2" diagonal for you anyway to see where in the travel range it comes into focus.  I will post my findings tomorrow.   Thinking about it, the light path in a 2" diagonal is no different to the light path in a 1.25" diagonal?  Just the free aperture?  I may be wrong!

It should do with no issue. 

2" diagonals do have a longer light path than 1.25" ones. I think the average 2" diagonal has an LP of around 100mm-110mm wheras with a 1.25" it's around 75mm. The exact figures vary with the brands and whether a mirror or prism is employed.

 

 

Edited July 23, 2017 by John

[Piero]

1 minute ago, jabeoo1 said:

Thats handy, well I will double check the zoom in the 2" diagonal for you anyway to see where in the travel range it comes into focus.  I will post my findings tomorrow.   Thinking about it, the light path in a 2" diagonal is no different to the light path in a 1.25" diagonal?  Just the free aperture?  I may be wrong!

That'd be fantastic!  Thanks again! 

As far as I understand, the required light path for a given eyepiece to reach focus is independent of 2" and 1.25" diagonals or straight view. The light path in a 2" diagonal is longer than the path in a 1.25" diagonal. So the 2" diagonal will require more inward focus travel (inward difference = 2" diag light path - 1.25" diag light path). 

[Piero]

6 minutes ago, ollypenrice said:

For visual use I rather like the clamshells. They are quick to open and close and give lots of fast and easy fore-and-aft travel for balancing. (They might come up second hand because some imagers have found them not to hold the tube in perfectly constant alignment, which can spoil the guiding. This is not an issue in visual observing.)

I have also found Ian King to be an excellent retailer.

Olly

Thank you Olly.  

Do you know where how much a cradle (95mm) weighs? I am looking for this info on the internet but so far no success..

[jabeoo1]

27 minutes ago, John said:

2" diagonals do have a longer light path than 1.25" ones. I think the average 2" diagonal has an LP of around 100mm-110mm wheras with a 1.25" it's around 75mm. The exact figures vary with the brands and whether a mirror or prism is employed.

 

 

Cheers John for the correction, its much appreciated.

[Stu]

TS are quite good at listing the optical length of different components.

[jabeoo1]

Piero, 

I have just tested my TV Zoom in the DF.  It will not come into focus even with the longer light path of the 2" Diagonal.  With the draw tube fully extended it requires around 10mm extra back focus.  See image of eyepiece set proud into diagonal to make up the difference.  

I also found that by having the extension tube in,  it added too much back focus meaning I could not get enough in focus ! This meant adding or removing the extension tube between high power & lower powers (Yawn)

I have not used the set up for a while as I take time out during the long summer days.  Its triggered my memory as to why I took the route to resolve this by buying a few accessories.  The 47mm Baader extension will allow me to gain focus with all my EP's without the draw tube being at the extreme end of its travel (in or out). 

Back along when I had a different eyepiece range it worked okay.  Everything is solvable, & as with many aspects of this hobby, when you change one thing it can have a knock on effect to how other things work.  

Having settled on 3 eyepieces & going about ironing out the niggling issues so its slick will be proven worthwhile.  In the next few days I am tweaking a few things and will add the findings here for you so you can make an informed decision.  

 

Edited July 23, 2017 by jabeoo1

[Piero]

Thanks for the info! Well, the good thing is that it can be solved!   

Your 47mm Baader extension is very interesting. I have a spare Baader 1.25" nosepiece and 2"/T2-to-1.25" adaptor which can be used as mini-extension tube if needed as a temporary solution.

[Piero]

50 minutes ago, jabeoo1 said:

Piero, 

I have just tested my TV Zoom in the DF.  It will not come into focus even with the longer light path of the 2" Diagonal.  With the draw tube fully extended it requires around 10mm extra back focus.  See image of eyepiece set proud into diagonal to make up the difference.  

I also found that by having the extension tube in,  it added too much back focus meaning I could not get enough in focus ! This meant adding or removing the extension tube between high power & lower powers (Yawn)

I have not used the set up for a while as I take time out during the long summer days.  Its triggered my memory as to why I took the route to resolve this by buying a few accessories.  The 47mm Baader extension will allow me to gain focus with all my EP's without the draw tube being at the extreme end of its travel (in or out). 

Back along when I had a different eyepiece range it worked okay.  Everything is solvable, & as with many aspects of this hobby, when you change one thing it can have a knock on effect to how other things work.  

Having settled on 3 eyepieces & going about ironing out the niggling issues so its slick will be proven worthwhile.  In the next few days I am tweaking a few things and will add the findings here for you so you can make an informed decision.  

 

Thinking more about, did you check this in day time or extract it from observation notes? 

I'm asking this because my eyepieces require more back focus in daytime because targets are closer. 

Edited July 23, 2017 by Piero

[jabeoo1]

Just now, Piero said:

 

Thinking more about, did you check this in day time or extract it from observation notes? 

I'm asking this because my eyepieces require more back focus in daytime because targets are closer. 

This is a daytime observation looking at leaves on a tree ~100 metres away.  

[Piero]

16 minutes ago, jabeoo1 said:

This is a daytime observation looking at leaves on a tree ~100 metres away.  

Okay, that could be the case. On my TV60, eyepieces require about 2cm extra back focus when I observe trees 50-200mt away.

If the zoom requires an extra cm to reach focus in daytime, I'd suspect that it might still work in nighttime (with the focuser tube almost all the way out). 

Edited July 23, 2017 by Piero

[ollypenrice]

3 hours ago, Piero said:

Thank you Olly.  

Do you know where how much a cradle (95mm) weighs? I am looking for this info on the internet but so far no success..

I don't, I'm afraid. But I've just picked up the clamshell belonging to Tom O'Donoghue's FSQ106 (resident here) and I can only say, 'not much,' as in 'seriously trivial.' Given that you can put it on a short dovetail and still have enough fore-aft movement for balancing I'd expect it to weigh in at less than a longer dovetail and rings.

Olly

Edited July 23, 2017 by ollypenrice
Added 'longer.'

[mikeDnight]

14 hours ago, jabeoo1 said:

Piero, 

I have just tested my TV Zoom in the DF.  It will not come into focus even with the longer light path of the 2" Diagonal.  With the draw tube fully extended it requires around 10mm extra back focus.  See image of eyepiece set proud into diagonal to make up the difference.  

I also found that by having the extension tube in,  it added too much back focus meaning I could not get enough in focus ! This meant adding or removing the extension tube between high power & lower powers (Yawn)

I have not used the set up for a while as I take time out during the long summer days.  Its triggered my memory as to why I took the route to resolve this by buying a few accessories.  The 47mm Baader extension will allow me to gain focus with all my EP's without the draw tube being at the extreme end of its travel (in or out). 

Back along when I had a different eyepiece range it worked okay.  Everything is solvable, & as with many aspects of this hobby, when you change one thing it can have a knock on effect to how other things work.  

Having settled on 3 eyepieces & going about ironing out the niggling issues so its slick will be proven worthwhile.  In the next few days I am tweaking a few things and will add the findings here for you so you can make an informed decision.  

 

That's interesting James. I thought the DF came with various extension tubes just like the DC does. It seems from your post that the DF doesnt have the Tak extension tubes, is that correct?

[jabeoo1]

9 minutes ago, mikeDnight said:

That's interesting James. I thought the DF came with various extension tubes just like the DC does. It seems from your post that the DF doesnt have the Tak extension tubes, is that correct?

I have one extension tube (70mm).  Bear in mind I bought used, so what I got with mine may not be exactly the same as the new package.  

[John]

My DL came with the long Tak 2" tube but I found that way too long for my eyepieces so I use the stock 2" drawtube adapter followed by a Baader 2" click lock followed by the Baader T2 Zeiss prism diagonal with a 2" barrel on the scope side and either a Baader 1.25"-T2 click lock for 1.25" eyepieces (obviously !) or a TS 2"-T2 adapter for 2" eyepieces. All my eyepieces come to focus, even the Leica ASPH zoom + VIP barlow !

The DL has the same 2.7" focuser as the DC and the Sky 90 I believe.

I know you are not considering a DL but I thought I'd just put my arrangement in the mix in case it's any use

Edited July 24, 2017 by John

[Piero]

No problem John! Any feedback is always welcome.

I thought that DL focuser were the same as the DF (and the Sky 90), not the DC.    I might be wrong though. Does it accept 2" eps directly or you need extra adapters? 

As far as I understand, the DF comes with a 70mm extension tube, but this is meant for imaging / straight view. (ref. https://www.cloudynights.com/topic/535739-takahashi-fc-100-dc-basic-questions/#entry7195864 )  

[John]

My bad - you are quite right, it's the DF that has the larger focuser.

Mixing me Taks up !

[mikeDnight]

This is the back end of my DC with its extension tubes. True Technology included the 2" adapter in my order without charge, though normally it would not be included with the DC unless ordered separately.

 

[Piero]

stunning! I like the focuser design! 

Edited July 24, 2017 by Piero

[Highburymark]

3 hours ago, mikeDnight said:

This is the back end of my DC with its extension tubes. True Technology included the 2" adapter in my order without charge, though normally it would not be included with the DC unless ordered separately.

 

More Tak green with the DC focuser - and even more if you go for the cradle!

 

[garryblueboy]

The DF comes with 70 mm extension but accepts 2" or 1.25 direct or via diagonal 

[Piero]

Those are beautiful! Great scopes guys!

 

@Highburymark 

Hi Mark, not sure but are you using a mini-Ercole mount and Gitzo tripod? may I ask you your thought about it, please? 

p.s. it looks very nice and sturdy.

[Highburymark]

16 hours ago, Piero said:

Those are beautiful! Great scopes guys!

 

@Highburymark 

Hi Mark, not sure but are you using a mini-Ercole mount and Gitzo tripod? may I ask you your thought about it, please? 

p.s. it looks very nice and sturdy.

Yes Piero - that's exactly my set up with all of my scopes now. They work together very well - particularly with light scopes like Taks - and I'm currently on holiday in Spain using them so they are great for travel. The Gitzo is particularly recommended - it's very light, and capable of a 25kg load. As I've said before though, they are expensive. I managed to pick mine up in a half price sale. So worth shopping around. The Ercole is also very capable. Last night I spent about an hour lying flat on the ground with the scope pointing vertically at Cygnus and Lyra, and it was steady as a rock. 

[Piero]

It looks lovely Mark!

How is tracking at high mags with the mini-Ercole? Do you need a counterweight? 

[Highburymark]

I do use a counterweight most of the time, but it still tracks pretty smoothly without. The counterweight also provides peace of mind that it won't tip over if the scope is accidentally nudged - always a danger with such a light tripod.