Focus Help for the Tak.

[leon]

Hi All,

This is to the people that own a FSQ Takahashi, 106, 102, or similar.

Now with my FSQ 106, imaging is great, visual is fine straight throug with crisp focus, however i cannot for the life of me get any comb of diagonal and Ep to focus at all. :shrug:

I use the Takahashi Diagonal with a 22mm Naglar EP, cant focus, then i try the WO Diagonal with the same EP, again cant get focus. :shrug:

As i said straight through with no diagonal is fine.

Could anyone who ownes one of these scopes, please suggest what may be a good combo, i also have the Extender Q, and extension tubes, plus all other accessories.

Thank You.

Leon :thumbsup:

[JohnG]

Hi Leon

Is it not enough inward focus or not enough outward focus ?

My combination with the FS-102 is fine using a TeleVue EverBright 2" diagonal and any eyepiece. :shrug:

Cheers

JohnG

[Dennis]

Hi Leon

You said you can focus okay straight through with an eyepiece for visual use.
You also said that when you add a star diagonal, you cannot focus.

This would indicate that due to the increased light path from inserting the diagonal, you cannot rack the focuser far enough inwards to obtain focus.

Does the focuser have a screw on extension tube that you can unscrew and remove? If it does, then this may provide you with more inward focus for a star diagonal?

Cheers

Dennis

[leon]

Hi John, Dennis, yes it is inward focus that i cant get it dose not travel far enough before it stops.

It makes no difference which EP i use, from Naglar 22mm, or pentax 10 and 14mm, just dont know.

leon

[jase]

The FSQ-106N is a different beast to the FS-102 when it comes to visual work. To reach focus with "any"* 2" diagonal on the FSQ you need to use the Extended Q(60) and Adapter Q(62). This is due to the limited back focus.

* Will still depend on eyepiece used.

See Extender Q parts listing attachment.

[JohnG]

Hi Leon

Have you tried using a 2" or 3" extension tube BEFORE the diagonal, that should take the focus out far enough to allow a bit more focus intravel.

I know in Japan they are used primarily in a straight through configuration, the use of a diagonal is frowned upon, therefore when Tak made these scopes they did not allow enough in focus travel, I believe that all newer Taks have a shorter tube for this purpose (using a diagonal).

Cheers

JohnG

[jase]

JohnG is on the money. As he mentions you need to use an extension tube, which is the Adapter Q before the diagonal.

Indeed, the newer Taks are shorter to get around this. The new FSQ-106ED for example has had the back focus increased to 178mm.

[JohnG]

Thanks Jase

I had a similar problem with the FS-102 when using the CAA and the 350D at Prime Focus, it only needed to travel in another 2mm or for focus, had to remove the CAA for everything to work.

Funny though, the CAA and the Tak Reduce work fine in combination. :shrug:

Cheers

JohnG

[leon]

Thanks Guys,

I have the system chart, and also the extension tube, but this makes no difference, when using the WO 2" diagonal, and the 22mm EP, the travel is just not enough,

But as John said, it works great, straight through, anyway it dosn't matter, I'm not really visual, and prefer to take images, actually that's what i really got the Tak for.

But i thought it might be nice to have a look once in a while, thanks for your help and suggestions.

Cheers Leon :thumbsup:

[Dennis]

Hi Leon

My Vixen 4' f9 refractor came with a (removable) black anodised extension tube which screwed into the (fixed) focuser tube. I had to unscrew and remove the black anodised extension tube in order to come to focus with a diagonal. For straight through, I screw the black anodised extension tube in and the eyepiece then comes to focus.

From what you describe, it appears that you do not have some sort of extension tube already attached, and you are mating the accessories with the main, fixed focuser tube?

Therefore, the only way to “get the image” further outside the focuser, so that a star diagonal could be inserted, would be to use some kind of lens? Do Takahashi make such an accessory? No doubt it would be expensive!

Cheers

Dennis

[leon]

Yes Dennis they do, it's the Extender Q1.6x , this used with the extension tubes suppiled with the unit is supposed to get it to visual work, at about F/9 compared to F5, which it is now.

I still have to wait for one part to come from Claude in SA, but it is said that the scope will focus nicely the way it is at F5 using the Takahashi Diagonal that i have, but it wont. :shrug:

The truth be known i may be doing something wrong, like i said i dont do much visual, i'll have another play tonight and see if i cant get it right.

Cheers Leon, And thank you for you advice. :thumbsup:

[Dennis]

Hi Leon

I just downloaded the FSQ-106 manual from Texas Nautical and it describes visual use with a 1 ¼ inch diagonal (Page 11) and a 2 inch diagonal (Page 12).

My reading of this is as follows:

1 ¼ inch diagonals
The FSQ-106 appears to have a compression ring focuser into which a 1 ¼ inch diagonal can be fitted.
A 1 ¼ inch diagonal has a relatively short light path through it, so it appears that it can be used with an eyepiece and you should get focus.

2 inch diagonals
A 2 inch diagonal has a much longer light path through it, so it appears it cannot be used visually unless you have the following optical train as described in the FSQ-106 Extender System Chart on Page 12:

Multi-Adapter Ring (8)
Visual Adapter (10)
Extender-Q (60)
Adapter-Q (66)
Diagonal Mirror (74)
2 inch eyepiece (48)

I don’t why Takahashi have all these fiddly bits and pieces – it makes life difficult compared to the ubiquitous SCT accessory systems.

WARNING:
The manual also indicates that there is an optical element very close to the focuser compression ring – so be very careful about inserting eyepieces or diagonals with a long 1 ¼ inch sleeve, otherwise the end of the sleeve may hit the glass – ouch!

Cheers

Dennis

[leon]

Yep, Dennis, your spot on, I have worked from this system chart as well, and the only bit i'm waiting on from Claude is the No 66 that screws onto the Extender Q. i have all the others, as i use some with the CA35 and wide T-mount for the 5D

Your right, why they have so many bits is beyond me too, it gets very confusing.

Thanks for the trouble you went to to check it out, maybe when the other bit arrives all will be well.

Leon :thumbsup:

[Dennis]

Hey Leon

No worries – its good practice for when I begin investigating what obscure Tak adapters I will need for my Mewlon 180, in order to use the Tak Flattener/Corrector for my SBIG ST7E ccd camera!

Cheers

Dennis

[Stephan]

Hi Leon,

It may sound silly but how do you use your Takahashi 2-inch diagonal?

Do you use the 2"-sleeve or do you screw it in and use the #76 adapter (as shown in the system chart here)?

Stephan

[leon]

Stephen, the native Tak diagonal screws onto the rear of the scope.

The problem has all been sorted now, with the help of some IIS members, it took a while but all is good.

Thanks Leon

[74tuc]

Leon,

If my memory serves me correctly - there may be a reason for the limited inside travel. The last lens in the petzval may be quite close to the back so you may damage the final lens if you push the draw tube in too far.

Jerry.:)

[leon]

Yes Jerry the rear lens is very close, and trust me, i am very aware of it's existence, and make doubly sure that all is well, thanks for you suggestion, we would not wish to do that lens any harm. :scared:

Leon :thumbsup: