Focus Problem

[leon]

Hi All.

What would others suggest could be the problem,

As You know i have just got the Tak 106, and was keen to try it out, so decided to have a visual, put the Pentax XW14mm into the dedicated Tak Diaganol and started to rack it in till it stopped, no focus, just short of critical focus by about 5mm or so.

Well i thought that a bit strange, so decided to put in the 9mm Reticle to do the drift align, same thing, no focus, this time it was worse, and way out.

Well i pondered on this all day, and figured that there must be something wrong with the scope.

After much thought, i decide to fit the EP's in a straight line, no Diag, well perfect focus on all EP's. and crystal clear, so it's not the scope.

I came to the conclusion that it must be the barrel length of the EP's when used with the diag, the pentax Ep's only have 30mm and the reticle has even less at 22mm, hence worse focus than the pentax Ep's.

The barrel obviously dosn't go down the diag far enough, so it cant focus, because i have run out of focus inward movement

It must be stated however that the Takahashi Diag, is a totally differnt beast to the other types available. they actually screw onto the scope, actually everything screws onto the scope.

Has anyone come across this before, as it looks like i might have to change Ep's.

Cheers Leon

[TidaLpHasE]

G'day Leon, had a quick squizz on googles and found a couple of pages that should help you out,
http://72.14.253.104/search?q=cache:...lnk&cd=2&gl=au

Gee thats a long link

[jase (Jason)]

Leon, for any visual work on the FSQ-106N you will need the Extender-Q x1.6. Have you got this? The reason why you need this is there is insufficient back focus in its native F/5 mode.

The new FSQ-106ED does not require the Extender-Q x1.6 as the new design has increased the back focus by 178mm. This is sufficient to use with bino viewers etc.

You can pick up the extender-Q x1.6 from AEC for $400.

Another thing to consider is can you reach focus by removing the diagonal and simply inserting the eyepiece only. You will be viewing at an awkward angle, but reducing the back focus required. In fact, many Japanese observers don't use diagonals at all. They simply insert the eyepiece they want to use.

Indeed, everything screws onto the FSQ. This makes for a much firmer coupling of accessories compared to using set screws or compression rings. These are prone to expansion and can make equipment such as camers etc loose in their fitting or worse case fall out onto the floor.

[leon]

Thanks Jase, well the fellow i bought this from said he only used this scope for visual, and used the diag, plus a LE eyepiece 7.5 from memory he told me.

I do have the Extender Q, it came yesterday and i'm sure that will work, but i thought i would just try it the way he said he used it.


Actually Jase i like the way everything screws on, makes for a good firm fit, no risk of slipping off.

I'm not to fussed about the focus bit at F/5, as this is mainly going to be used for imaging anyway.

Thank You for your response, and thanks Trevor for the link.

Cheers Leon

[skies2clear]

Originally Posted by leon

Thanks Jase, well the fellow i bought this from said he only used this scope for visual, and used the diag, plus a LE eyepiece 7.5 from memory he told me.

Cheers Leon

Leon, I'm really quite surprised at this because I have XW's and Tak LE 7.5, and the difference in focus position is tiny, so I can't see how the Tak 7.5 would work in this scope, and the XW14 does not. I can't offer any other suggestions as I'm unfamiliar with your FSQ 106N,

I presume the XW sits in all the way in the eyepiece holder/diagonal?

Cheers

[leon]

Everything worked fine without the Diag, as i tried it out last night with a drift align, which, went very smoothly.

Only got half done and go to the meridian when the clouds nick off.

Anyway as suggested in the link that Trevor supplied it isn't that uncommon and has happened to others as well, i think it has all to do with the dedicated Takahashi Diagonal.

I have another Diagonal, so when the 2'' adapter for the Extender Q comes i will see how that goes.

Leon