Takahashi FC-100 and FC-76 advice

[Commanderfish]

Has anyone used the Tak Vari-extender with any of these scopes? There appears to be a big difference in the pricing between the Vari extender and the newer Q extender.

Does anyone know what the difference is? I think the Q operates as a field flattener but I don't know if there's anything between the two.

[UKDiver]

On 03/05/2021 at 19:21, HollyHound said:

I’m happy to report that I (finally) managed to unscrew that blue extension... just had to settle it carefully on a large towel, grip the whole tube and silver end ring in one hand and the extension in the other and give it some welly 😬🤣

Does make the OTA much more flexible now 😃

Thanks for the advice, it gave me the confidence to keep persevering 👍

 

I bet that was a relief Gary.

It was for me!

Adrian

[HollyHound]

1 hour ago, UKDiver said:

I bet that was a relief Gary.

It was for me!

Adrian

At least you know now that it can be done... should you ever need too 😀

[UKDiver]

On 18/04/2021 at 08:02, mikeDnight said:

Congratulations on becoming a daddy to a brand new DC. I imagine you're pacing up and down the room with a cigar in your mouth - unlit of course as its healthier, in eager anticipation of the arrival of your new baby. Honestly, the DC is a jewel,  just keep your 2" visual back as short as possible as the DC focuser is a bit tight on inward travel. Having said that, I rarely had any problems reaching focus with mine, but I used only 1.25" eyepieces with the Tak prism, which has a very short light path. My DC proved to be my most used scope out of four decades of observing. The Moon will never cease to leave you in disbelief, while the planet's, when we'll situated, are stunning. DSO's I found to be unusually bright for a 4" telescope, but good dark adaption is still essential if you want to get the best out of it. It's upper magnification limit with perfect seeing will be around 120X per inch, so 500X on a good night, which can at times give some quite remarkable views of double stars. It will go higher without breaking down, but nothing's gained by doing so. I'm sure you'll enjoy experimenting to find what power suits each object. The fun you'll have will be hard to put into words I'm sure. Just relax and enjoy it! 😊

I can't achieve focus when using a 2x or 3x Barlow. I suspect this is evidence of the lack of inward travel. As I currently have the DC set up with the Tak prism, is it the removal of the green tube mentioned elsewhere that will enable focus?

How do you achieve 500x magnification?

[mikeDnight]

15 minutes ago, UKDiver said:

I can't achieve focus when using a 2x or 3x Barlow. I suspect this is evidence of the lack of inward travel. As I currently have the DC set up with the Tak prism, is it the removal of the green tube mentioned elsewhere that will enable focus?

How do you achieve 500x magnification?

I cant remember struggling to reach focus with a barlow in the DC. Takahashi offer a 2X barlow that goes before the prism, or can be used after the prism to give (i think) 1.6X. I tended to use a SW delux 2X or old 2X Celestron Ultima SV, usually attached to my binoviewer. I did struggle to get enough inward focus with the DC and a 1.25" Lunt Herschel wedge. I removed the green extension tube to reach focus at low power with my binoviewer without barlow.

With my DZ I get 500X with my Vixen 1.6mm high resolution eyepiece, and 1000X with a 2X barlow. That was fun!    With my DC I could get 474X with a 1.6X extender Q and 2.5mm Vixen LV eyepiece, which gave an impressive view of a large crescent Venus, as well as a subtly detailed view of a sub 5 arc second Mars. You don't need to buy an extender Q though, as there are barlows of similar amplification available at a fraction of the cost. Using a longer focal length barlow or power mate can give a comfortable alternative for reaching high powers. 

[UKDiver]

46 minutes ago, mikeDnight said:

I cant remember struggling to reach focus with a barlow in the DC. Takahashi offer a 2X barlow that goes before the prism, or can be used after the prism to give (i think) 1.6X. I tended to use a SW delux 2X or old 2X Celestron Ultima SV, usually attached to my binoviewer. I did struggle to get enough inward focus with the DC and a 1.25" Lunt Herschel wedge. I removed the green extension tube to reach focus at low power with my binoviewer without barlow.

With my DZ I get 500X with my Vixen 1.6mm high resolution eyepiece, and 1000X with a 2X barlow. That was fun!    With my DC I could get 474X with a 1.6X extender Q and 2.5mm Vixen LV eyepiece, which gave an impressive view of a large crescent Venus, as well as a subtly detailed view of a sub 5 arc second Mars. You don't need to buy an extender Q though, as there are barlows of similar amplification available at a fraction of the cost. Using a longer focal length barlow or power mate can give a comfortable alternative for reaching high powers. 

Sounds like I should have tried to beat HollyHound to the punch on the Vixen 1.6 that came up at the w/e. Still, plenty of time for another to come up perhaps.

The two Barlows I have are both Celestron. 3x X-Cel LX and 2x 'bog standard'. I think I'm out of the game for Tak extenders! So what might I be getting wrong? I tried a couple of smaller FL EPs in both Barlows and could not get to focus.

Edited December 6, 2021 by UKDiver

[mikeDnight]

1 hour ago, UKDiver said:

Sounds like I should have tried to beat HollyHound to the punch on the Vixen 1.6 that came up at the w/e. Still, plenty of time for another to come up perhaps.

The two Barlows I have are both Celestron. 3x X-Cel LX and 2x 'bog standard'. I think I'm out of the game for Tak extenders! So what might I be getting wrong? I tried a couple of smaller FL EPs in both Barlows and could not get to focus.

The Vixen HR's do seem to circulate from time to time, although I imagine they will eventually settle in the hands of those who find them most useful, and so become quite rare on the second-hand market. Tak do a similar, though more expensive alternative in their TOE eyepieces. I think the TOE's may have more elements and a slightly wider field?

I'm not sure why your DC isn't reaching focus with your barlow attached. Is there any chance you could post a pic so we can try and assess what the problem might be?

[UKDiver]

On 06/12/2021 at 22:37, mikeDnight said:

I'm not sure why your DC isn't reaching focus with your barlow attached. Is there any chance you could post a pic so we can try and assess what the problem might be?

Hi Mike,

Took me a few days to take a picture. I've not yet had an opportunity to try focusing again with this arrangement to confirm I have a problem.

Adrian

[mikeDnight]

1 hour ago, UKDiver said:

Hi Mike,

Took me a few days to take a picture. I've not yet had an opportunity to try focusing again with this arrangement to confirm I have a problem.

Adrian

Thanks for the pic Adrian. I haven't used that particular Celestron barlow, but my immediate reaction was to think the barlow has quite a long body, which makes me wonder if the problem lies with the barlow. Do you have another barlow that you could try? Does the scope with barlow reach focus with shorter focal length eyepieces?

[UKDiver]

4 minutes ago, mikeDnight said:

Thanks for the pic Adrian. I haven't used that particular Celestron barlow, but my immediate reaction was to think the barlow has quite a long body, which makes me wonder if the problem lies with the barlow. Do you have another barlow that you could try? Does the scope with barlow reach focus with shorter focal length eyepieces?

I've a 2x that is about 20mm shorter. I think I tried it too, but can't be sure now. So if conditions work for me, I'll give other combinations a go.

[jock1958]

20 hours ago, UKDiver said:

Hi Mike,

Took me a few days to take a picture. I've not yet had an opportunity to try focusing again with this arrangement to confirm I have a problem.

Adrian

Assuming you can reach focus with your 32mm plossl then I think the extended lightpath  of the barlow is the possible issue? 
I had problems reaching focus with my Tak FC-100DL & FS-60C and it was a case of experimenting with either removal or addition of extension tubes and visual backs etc etc.
Is it possible to remove the blue tube in front of your focuser and give that a go? 

Edited December 11, 2021 by jock1958

[UKDiver]

59 minutes ago, jock1958 said:

Assuming you can reach focus with your 32mm plossl then I think the extended lightpath  of the barlow is the possible issue? 
I had problems reaching focus with my Tak FC-100DL & FS-60C and it was a case of experimenting with either removal or addition of extension tubes and visual backs etc etc.
Is it possible to remove the blue tube in front of your focuser and give that a go? 

Removing that section is on my list to try. I know it's been taken off before, but it did not shift when I made a half hearted attempt.

[HollyHound]

21 minutes ago, UKDiver said:

Removing that section is on my list to try. I know it's been taken off before, but it did not shift when I made a half hearted attempt.

It certainly has been taken off before… it was a leap of faith at the time because it was quite  tight and I was worried about damaging it.

However, after assurances on here, I gave it a a careful but firm twist (holding the focuser is a small towel) and it turned.

I think you should be fine now, as I believe it might have just been a tight spot or even a bit of paint or similar that was binding the end. Second time I tried it, it came off much more easily… still tight, but it will turn 👍

Edited December 11, 2021 by HollyHound

[jock1958]

3 hours ago, UKDiver said:

Removing that section is on my list to try. I know it's been taken off before, but it did not shift when I made a half hearted attempt.

If the DC focuser tube is the same or similar to my FS-60 IE 2” diameter with just under 1.25” of travel then there will be frustrations at some point owing to this limitation. 
If you don’t feel comfortable removing the blue tube then a smaller barlow like the Baader 2.25x barlow which is fairly cheap and pretty good, there are more expensive options but won’t go into that just now 😬💵💵

Edited December 11, 2021 by jock1958

[mikeDnight]

I think that Tak expect Tak users to use Tak eyepieces, Tak diagonals and a Tak barlow or extender-Q. Then presumably all will work flawlessly.  Back in the real world, I've found the 2X SW Delux barlow to be excellent (and cheap). Removing the blue spacer tube may well require the use of the black extension tube, and so doesn't resolve all potential focusing issues. You'd imagine that by now Takahashi would have had the intelligence to notice there is a problem with the FC100DC, and shorten the spacer while increasing the length of the draw tube. It is possible to iron out most focusing issues by careful choice of eyepieces and reduces etc. I removed the 1.25" visual back and replaced it with a short Tak 2" back while using a SW low profile 2" to 1.25" reducer, which gave me a little more inward focus.

[jock1958]

3 minutes ago, mikeDnight said:

I think that Tak expect Tak users to use Tak eyepieces, Tak diagonals and a Tak barlow or extender-Q. Then presumably all will work flawlessly.  Back in the real world, I've found the 2X SW Delux barlow to be excellent (and cheap). Removing the blue spacer tube may well require the use of the black extension tube, and so doesn't resolve all potential focusing issues. You'd imagine that by now Takahashi would have had the intelligence to notice there is a problem with the FC100DC, and shorten the spacer while increasing the length of the draw tube. It is possible to iron out most focusing issues by careful choice of eyepieces and reduces etc. I removed the 1.25" visual back and replaced it with a short Tak 2" back while using a SW low profile 2" to 1.25" reducer, which gave me a little more inward focus.

Ha ha Mike you mentioned one of my expensive options the 2” visual back (£99 from FLO).I use this plus a Baader T2 prism diagonal with a 2” nosepiece which buys you precious in focus. I know others have gone further and splashed out on Feathtouch focusers . 

 

[StarryEyed]

27 minutes ago, mikeDnight said:

I think that Tak expect Tak users to use Tak eyepieces, Tak diagonals and a Tak barlow or extender-Q. Then presumably all will work flawlessly....

I think Tak know exactly what they are doing. Borg seem to be even more UNIQUE about things like this. But fair enough. 

[Andrew_B]

7 hours ago, mikeDnight said:

I think that Tak expect Tak users to use Tak eyepieces, Tak diagonals and a Tak barlow or extender-Q. Then presumably all will work flawlessly.  Back in the real world, I've found the 2X SW Delux barlow to be excellent (and cheap). Removing the blue spacer tube may well require the use of the black extension tube, and so doesn't resolve all potential focusing issues. You'd imagine that by now Takahashi would have had the intelligence to notice there is a problem with the FC100DC, and shorten the spacer while increasing the length of the draw tube. It is possible to iron out most focusing issues by careful choice of eyepieces and reduces etc. I removed the 1.25" visual back and replaced it with a short Tak 2" back while using a SW low profile 2" to 1.25" reducer, which gave me a little more inward focus.

In effect that's what they did with the FC-100DF.

My FS-60CB has the same focuser as the DC and while I can understand the engineering reasons for its short travel, it can be annoying at time to have to fiddle with adapters to reach focus with certain eyepieces or diagonals.  Having said that, the FT2025BCR on my other scope also needs an extension tube if I want to use my 1.25" prism rather than the 2" mirror diagonal which was a bit of a surprise. I found a really nice 50mm extension and 2" eyepiece adaptor for only 20 quid that matches the Feather Touch aesthetic perfectly but some people might object to having to spend extra money to get their diagonals and eyepieces to work when they've already shelled out so much for the focuser.

Tak obviously reuse components where possible so presumably they don't have a suitable focuser that's small and light enough for the DC but with a longer draw tube, and the next model up is the Sky-90 focuser in the DF and DZ. They could always design a new focuser but that's an expensive proposition, especially if it would only be used in that single model of scope.