13190 replies to this topic

[lumos]

Yes, shouldn't be a problem.

Thank you so much. That makes a huge difference.

[Caddman]

I just acquired a FCT-100 with FCT-100 reducer. Other than a tiny smudge on the lens (the seller told me about it prior to the sale), it appears to be in really nice shape. The focuser is buttery smooth. I'm currently trying to figure out how to attach a camera to it. I have a diagram. Once I figure out the thread size coming off the reducer, it's just a matter of coming up with the attachments for the 77mm back focus. 

I also have an earlier version of the FSQ-106. I'm looking forward to doing a side by side comparison of the two scopes, both visually and photographically.  A friend of mine has the same camera that I do. So, I can do an apples to apples comparison.

[leviathan]

Congratulations and looking forward for comparison !

[Kitfox]

I just acquired a FCT-100 with FCT-100 reducer. Other than a tiny smudge on the lens (the seller told me about it prior to the sale), it appears to be in really nice shape. The focuser is buttery smooth. I'm currently trying to figure out how to attach a camera to it. I have a diagram. Once I figure out the thread size coming off the reducer, it's just a matter of coming up with the attachments for the 77mm back focus. 

I also have an earlier version of the FSQ-106. I'm looking forward to doing a side by side comparison of the two scopes, both visually and photographically.  A friend of mine has the same camera that I do. So, I can do an apples to apples comparison.

Welcome to a small club; you have a very nice scope there. It is a completely different scope from the FSQ, but should complement it very well in your collection.

 

I have the 4 FCTs from 76 up to 150, and intend to hang onto them quite a while!  Still looking for an old 65, and don’t expect to ever see a 200, but who knows?

Edited by Kitfox, 16 May 2025 - 03:21 PM.

[cavecollector]

For anyone wanting to upgrade their tripod, I just purchased the large Takahashi wood tripod and it is really nice! So many clever design features too, an absolute joy to use. I know these things are crazy expensive,  but they're extremely well made and Takahashi has invested a ton of time on perfecting every aspect of the design. It's well worth the investment. 

[helpwanted]

For anyone wanting to upgrade their tripod, I just purchased the large Takahashi wood tripod and it is really nice! So many clever design features too, an absolute joy to use. I know these things are crazy expensive,  but they're extremely well made and Takahashi has invested a ton of time on perfecting every aspect of the design. It's well worth the investment. 

What mount is on the tripod ?

[cavecollector]

An EM-200.

[Caddman]

Welcome to a small club; you have a very nice scope there. It is a completely different scope from the FSQ, but should complement it very well in your collection.

 

I have the 4 FCTs from 76 up to 150, and intend to hang onto them quite a while!  Still looking for an old 65, and don’t expect to ever see a 200, but who knows?

Nice! I'd love to get my hands on a 150.

I have the newer FCT-65 with the reducer.

[lumos]

I wonder if someone could be so good as to help me with my misunderstanding. I am just setting up my new TSA-120 for imaging. My ordered flattener and extender are not yet in stock so they just delivered the bare scope. I have taken off the stock focusser and replaced it with the Primaluce Esatto 3. I looked up the back focus distance for the TSA-120 (not flattened, reduced or extended), probably more accurate to say focal point distance and got a figure of 230mm. I am testing during the day on distant trees and I kept adding spacers until I could get focus. I finally managed to achieve focus with what I would say was a distance of 320mm from the edge of the threads where the focusser attaches. Now 230mm seems about right compared to the other Taks, so is it calculated  from a different reference point, such as the end of the stock focusser. Or would it have been 230mm had I been focussed on infinity but 320 for near point.

 

Either way it has been a nice day out for 9 lucky spacers. I am measuring from the Primaluce adapter that is screwed onto the OTA, and has an optical thickness of 2mm. I measured to the sensor in the 2600mm (12.5mm behind the front face of the camera with the tilt adjuster off).

 

Any way, please let me know my clownish error.

[james7ca]

If you know the subject distance you can calculate the difference in focus position between that subject and infinity using the simple, thin lens formula.

 

From the internet

 

To calculate the focal length of a thin lens, use the thin lens equation expressed as 1/do + 1/di = 1/f, where do is the object distance, di is the image distance, and f is the focal length.

 

Rearranging to solve for "di" (or 1/di).

 

1/di = 1/f - 1/do

 

f = 900mm (for TSA-120 since 7.5 x 120mm = 900mm)

 

At infinity you get do = infinity and thus 1/di = 1/f - zero (effectively). So, di must be/is equal to the focal length (f).

 

So, if the "do" is 100 meters or 100 * 1000mm/m = 100,000mm

 

1/di = 1/900 - 1/100000 =  0.00110111...

 

And, taking the multiplicative inverse of the above 0.0010111... you get 908.17mm from 1 / 0.0010011.., so an increase of 8.17mm over the focus position at infinity (900mm).

 

Then, if you were at 25 meters you'd get 1/900 - 1/25,000 = 0.00107111... and a multiplicative inverse of 933.61mm, an increase of 33.61mm.

 

etc.

 

Pretty simple when using a calculator and explained more at this website:

 

 https://study.com/sk...e from the lens.

Edited by james7ca, 17 May 2025 - 12:23 PM.

[lumos]

If you know the subject distance you can calculate the difference in focus position between that subject and infinity using the simple, thin lens formula.

 

From the internet

 

 

Rearranging to solve for "dl" (or 1/di).

 

1/di = 1/f - 1/do

 

f = 900mm (for TSA-120 since 7.5 x 120mm = 900mm)

 

At infinity you get do = infinity and thus 1/di = 1/f - zero (effectively). So, di must be/is equal to the focal length (f).

 

So, if the "do" is 100 meters or 100 * 1000mm/m = 100,000mm

 

1/di = 1/900 - 1/100000 =  0.00110111...

 

And, taking the multiplicative inverse of the above 0.0010111... you get 908.17mm from 1 / 0.0010011.., so an increase of 8.17mm over the focus position at infinity (900mm).

 

Then, if you were at 25 meters you'd get 1/900 - 1/25,000 = 0.00107111... and a multiplicative inverse of 933.61mm, an increase of 33.61mm.

 

etc.

 

Pretty simple when using a calculator and explained more at this website:

 

 https://study.com/sk...e from the lens.

That is so helpful. I would have been fumbling around in the dark tonight removing spacers. As my do is around 25m and my focusser is currently almost fully racked it I will now remove 42mm of spacers and remember to get focus under the stars I will be racking out around 8.39mm.

 

I owe you a huge debt of gratitude.

[james7ca]

That is so helpful. I would have been fumbling around in the dark tonight removing spacers. As my do is around 25m and my focusser is currently almost fully racked it I will now remove 42mm of spacers and remember to get focus under the stars I will be racking out around 8.39mm.

 

I owe you a huge debt of gratitude.

Okay, but while the above should be exact for a thin lens note that the TSA-120 isn't really a "simple, thin lens" and thus these values are probably only approximate, but likely good enough to get you started.

[lumos]

Okay, but while the above should be exact for a thin lens note that the TSA-120 isn't really a "simple, thin lens" and thus these values are probably only approximate, but likely good enough to get you started.

So noted, but I should add that you are some 6000 miles from me so the chances of my turning up at your doorstep to complain are slight.

[dan_hm]

I have the newer FCT-65 with the reducer.

Have you had a chance to image with it? Mine and everyone’s I’ve seen has really bad optical defects. Been waiting on Tak to get back to me on the issue.

[leviathan]

I read somewhere that FSQ line is discontinued ? Are they going to replace them with a newer version ?

[plyscope]

The latest version is available in the UK.

 

https://www.firstlig...-refractor.html

[SandyHouTex]

The latest version is available in the UK.

 

https://www.firstlig...-refractor.html

If you could order it from Japan, it would be 4021.09 Euro, $4481.37 USD, or 3380.53 British Pound.  Based on the FLO 6845 Euro.  Assuming I did the conversions right.  It's 654,000 yen in Japan. 

Edited by SandyHouTex, 17 May 2025 - 07:54 PM.

[Emanuel]

I read somewhere that FSQ line is discontinued ? Are they going to replace them with a newer version ?

 

Yes, they will.

Check out the video from Astroworld, specially from 1:17:00.

Its a long video, but well worth to see it, You get a real description of the Takahashi telescopes capabilities and how they are manufactured.

Really cool. I know i`m waiting for that to happen

 

https://www.youtube....h?v=wlM4HFBosN4

[Emanuel]

Have i showed a picture of my prrrecious ?

 

 

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[lumos]

I managed to grab some first light with my new TSA-120 last night. I was too impatient to wait a week for my reducer so I just went ahead. I did not have time to work on guiding, autofocus or even shoot any calibration frames as one of my beagles came in covered in blood so I just left the TSA doing whatever it was doing and I spent the night in the hospital. When I got back at dawn I saw there was complete cloud cover but I I threw what I had at WBPP. First here is the set up complete with messy cables.

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[lumos]

Now here is the aberration inspector on the RGB channel combination but nothing else done at all. To my eyes the stars are acceptable right to the edges. remember I have not tuned the focusser and I have no idea what the guider was doing.

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[lumos]

Here is a rough edit as I did not want to waste too much time until I had some flats and darks. Strangely it looks really dark as a highly compressed jpg. The question I have for you all is should I cancel my order for the flattener?  Would I reduce the overall length of the OTA assembly as the new backfocus would be 117.4mm rather than my current 280mm.

 

By the way, how would you stop the filter wheel striking the tripod? Should I add even more spacers?

 

Thanks so much for any advice.

 

Edit: Sorry, I realise that I am using spacers in two different contexts. I mean the riser blocks that the rings sit on to move the OTA away from the saddle.

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Edited by lumos, 18 May 2025 - 10:00 AM.

[lumos]

Of course a random single sub is more revealing but I am delighted with this wonderful instrument so far.

 

Frankly I am amazed that all those spacers I had to add to achieve focus has not introduced significant tilt. It looks, quite frankly, ridiculous.

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Edited by lumos, 18 May 2025 - 07:05 AM.

[Dean J.]

Yes, they will.

Check out the video from Astroworld, specially from 1:17:00.

Its a long video, but well worth to see it, You get a real description of the Takahashi telescopes capabilities and how they are manufactured.

Really cool. I know i`m waiting for that to happen

 

https://www.youtube....h?v=wlM4HFBosN4

I wonder when the FSQ-106 replacement will come?  It will be interesting to see what they come up with.  In the video Chris Montemayor implied that it would be an upscaled version of the FCT-65 triplet.  So, maybe a FCT-100 or a FCT-110 triplet?

[25585]

If you could order it from Japan, it would be 4021.09 Euro, $4481.37 USD, or 3380.53 British Pound.  Based on the FLO 6845 Euro.  Assuming I did the conversions right.  It's 654,000 yen in Japan. 

FLO is £ not €.