Any experiences with Takahashi 60/76mm refractor telescope for terrestrial use? (1 Viewer)

[Passakorn]

I am not sure where should I ask this question. I just get the Takahashi fs60cb and a cq1.7x extender and also the fc76dc tube that I can convert this setup to be fs60 (355mm FL), fs60Q (600mm), fc76dcu(570mm) and fc76Q (950mm). Now I am using it with william optics durabrite diagonal and erecting prism (1.25”) along with the Baader 8-24mm(Mk3) zoom eyepiece.

With this setup the erecting prism gets me about 50-60m max for maximum focussing distance, and durabrite diagonal gets me to the infinity focus except for the 8mm focal length.

Now I am trying to find the cheapest solution (hopefully just buying some adapters) to make this setup reach infinity focus. I am wondering if anyone who has been using this setup could suggest what is the best and cheapest way to reach infinity focus.

Also I am wondering if anyone uses the televue 3-6mm zoom eyepiece? I was told that it is rather difficult to use but not sure why it is difficult except short eye relief and very small exit pupil at higher magnification. I am hoping that I can use 3-6mm EP with fs60 scope for very small form-factor terrestrial use and still have high magnification.

I have the nikon ED50 as a walking scope so I intend to use this Takahashi setup as a grab and go stationary base for terrestrial use and can also enjoy seeing the night sky. I test it in the fs60Q form-factor and the image quality is superb at 75X even with only 60mm scope. The image from the rest of the setups are superb too but the fs60Q provides the smallest form-factor setup to 75X.

thank you so much for any suggestions.

Passakorn

 

[jring]

Hi,

you need to get your eyepiece closer to the objective for infinfinity focus. Or you need a barlow to get the focal plane further out. I guess with the Baader 2.25x barlow you should be fine - and have higher magnification - but the setup with barlow and EP is fairly long...

Joachim

 

[Passakorn]

I tried the 2.25x barlow that comes with the 8-24 eyepiece and it makes the maximum focussing distant even shorter. Now I have no infinity focus at all. Hate to have to buy a new diagonal.

 

[Pepitogrillo]

I've used the Takahashi FS60C fit terrestrial, birdwatching... And contrast and sharp fantastic... but a great CA and not waterproff, uff!! Very very Delicat!!!
PG.

 

[Passakorn]

Here are my setup today. Diagonal reaches infinity focus up to about 70x with superb image quality but bad for low level bird as have to bend the neck badly. Erecting prism does not reach focus yet.

 

[Mark9473]

I would look for a shorter visual back on the end of the focuser.
Or if you're very brave you can cut a bit off your OTA...

 

[Mark9473]

I forgot to mention, the Baader Mk.IV has a slightly more favourable focus position than the Mk.III. Whether that is sufficient for you to reach infinity focus is hard to predict.

 

[Pepitogrillo]

What model is this Takahashi?

 

[Passakorn]

In the photo it is an FS-60CB. I add the CQ1.7x onto it.

 

[Passakorn]

I bought this adapter to shorten the distance and now it can focus with an erecting prism. The new issue is the minimum focus is about 10m without adding extension ring.

 

[Mark9473]

With your current set-up, how many mm of travel range do you have left on the focuser with the scope set to infinity focus?

 

[Passakorn]

Just try tonight. With erecting prism, at infinity focus it still has about 10mm left. It works with a 2.25x barlow too but the barlow introduces very strong CA to my eyes. Note that now it is an fc-76duc form factor.

 

[Mark9473]

You could add a 8 mm spacer ring in your visual back to achieve a little closer focus distance. I'm not sure how much difference it will make. There's a formula to calculate but I don't have it on my phone.

Another thing you could try: if the eyepiece holder can be removed on that diagonal, then it can be replaced by a helical focuser that would put the eyepiece further back when you need close focus.

 

[DRodrigues]

For image erectors to astro telescopes, have a look at Image erectors for Astro-telescopes
The modified Omegon would focus for sure, at least without the extenders.