Takahashi FC-100DC debut (and diagonal problem)

[PGM]

Hello,

Well, yesterday was inauguration day for my Tak! ? ...and also for me as a scope operator.

The full set-up I used consists of:
- Takahashi FC-100DC (stock, but no finder scope)
- Takahashi clamshell + Vixen plate
- Berlebach Dovetail Clamp with Pressure Shoe
- Giro Ercole
- Gitzo GT5533S tripod
- Baader T-2 Amici Prism Diagonal BBHS
- Baader BGO 18mm / 6mm
- Celestron X-Cel ED Barlow 2x

I purchased this Baader T-2 Amici Prism Diagonal BBHS because I love the Moon so much that I can justify having a dedicated diagonal just for it. However, I do intend to get a second-hand Baader T-2 Zeiss Prism BBHS when I find one for sale in excellent condition.

The BGOs 18/6mm are the only EPs I have at the moment, but I have a few gems on the way (TV Panoptic 24mm, TV Plössl 8mm, Pentax XW 7/5/3.5mm).

The clouds that had lasted for many days were mostly gone but seeing was far from great. Just as I was starting to extend the tripod legs, one of them came completely off, along with some inside parts. This problem stole valuable time (and calm!) from me, but was eventually fixed with the help of two SGL members, as posted in another topic.

So now the whole set-up was ready to go, with a BGO 18mm on the spot. I pointed in the Moon's general direction, took a peek, adjusting the focuser... nothing. I checked the diagram on the manual, and concluded I needed to take out the aux. ring adapter because I was using a diagonal. Did that, took another peek, changed EPs... still nothing. I remembered reading a few posts about light path issues, so assumed this might be one of those problems (which I still don't fully understand, to be honest). So I decided to go Japanese-style, removing the diagonal, adding the aux. ring, to look directly through the tube.

By this time, the Moon and Mars were already low, and seeing was not helping either. I pointed the 18mm at the Moon, took a peek... and there was Luna upright in all its glory! ? I could see the unstable air waving in front of it, but still, very clear, and obviously closer than with my binos (even if not as convenient!). Very nice indeed.

Time was of the essence, so a few minutes later I searched for Mars, and this was much trickier than I expected, because I have no finder scope. I have some knowledge of where many objects and constellations are, but I'm just a beginner and so the reversed image orientation and the first-time handling of the mount were harder than expected. Many times I found myself searching aimlessly. Still, all part of the experience curve, I'm sure. I eventually found Mars with the BGO 18mm, and also Sirius, Rigel, and a few other stars, but many other targets were impossible to find and identify - most were also too high in the sky to look without a diagonal (at this time I was breaking my neck and back doing yoga stances on the ground ?). The BGO 6mm was almost impossible to use. I enjoyed using it briefly on the Moon, but could not use it on anything else. I tried focusing a star on-axis with the 18mm, tightening the mount's clamp, and exchanging to the 6mm without shaking the scope (other than unscrewing the Tak focuser's ring), but no success, could not see a thing with the 6mm. I'm certainly doing something wrong...

Ok, now back to my Amici diagonal. According to Baader's website, it has a 47.5mm optical length. Can anyone please explain what I need to make it work?

Lastly, regarding the controversial Takahashi lens cleaning. Some topics on SGL and CN mention that the manual indicates alcohol is to be completely avoided, which some members attribute to a wrong translation from Japanese. My Tak is brand new, so maybe the manual has been corrected/updated - it has no mention whatsoever about alcohol.
Care & Maintenance highlights:
- large hand blowers are recommended;
- canned air is strongly disapproved;
- "Use pure cotton swabs slightly moistened with lens cleaner and gently remove any dirt"

Well, clouds are back today. Hopefully they'll clear for 46P tomorrow night...

Thanks for looking!

[Stu]

Great setup PGM! Just a few teething problems to sort.

When you say you saw nothing with the prism in the light path,  could you see a bright refocused moon or just darkness? I'm guessing it was more a finding issue,  best get at least an rdf sorted so you can find things more easily then go from there. You should at least see bright moonlight through the eyepiece even if way out of focus. 

You with get there.

[PGM]

6 minutes ago, Stu said:

Great setup PGM! Just a few teething problems to sort.

When you say you saw nothing with the prism in the light path,  could you see a bright refocused moon or just darkness? I'm guessing it was more a finding issue,  best get at least an rdf sorted so you can find things more easily then go from there. You should at least see bright moonlight through the eyepiece even if way out of focus. 

You with get there.

Thanks.

When I used the diagonal, the sky was not completely dark yet, so I could definitely tell apart the dark blue sky and a completely defocused whitish surface (which I took for clouds, but later on guessed it was the Moon). It was just completely out of focus, like a white wall.

[mikeDnight]

Did you have the extension tubes attached? If so, you'll need to remove them. The set-up should look like the attached picture when a diagonal is used. In this mode the scope should focus pretty much all 1.25" eyepieces. You might like to try and focus on the distant horizon before you aim it at the night sky, at least until you've acquired a finderscope of some sort. 

It's interesting that you say the latest user manual makes no mention of alcohol! 

Great scope by the way!! 

 

[Highburymark]

It will just be a question of finding the right adapters to allow you to reach focus with the diagonal. One of the features of the Takahashi focuser is very limited travel, which means you need to get the spacers/adapters right. 

[PGM]

1 hour ago, mikeDnight said:

Did you have the extension tubes attached? If so, you'll need to remove them. The set-up should look like the attached picture when a diagonal is used. In this mode the scope should focus pretty much all 1.25" eyepieces. You might like to try and focus on the distant horizon before you aim it at the night sky, at least until you've acquired a finderscope of some sort. 

It's interesting that you say the latest user manual makes no mention of alcohol! 

Great scope by the way!! 

 

Hi Mike,

My DC did not look like that! I used adapters 81+15+14+46+diagonal, and you seem to be going without part 81 - if I'm seeing it right. Can the manual be wrong? That's great news, I'll try that tomorrow! Too cloudy tonight...

 

 

[PGM]

2 hours ago, mikeDnight said:

It's interesting that you say the latest user manual makes no mention of alcohol! 

None I could find ?

 

[PGM]

2 hours ago, Highburymark said:

It will just be a question of finding the right adapters to allow you to reach focus with the diagonal. One of the features of the Takahashi focuser is very limited travel, which means you need to get the spacers/adapters right. 

How does one calculate the right parts? I was planning to give the Tak focuser a chance before getting a FT focuser, but this might settle it.

[mikeDnight]

Yes, it seems to be 81 that might be throwing your focus too far out. 15 should screw directly onto the draw tube and all should be well. I don't know why Takahashi insist on supplying these adapters. I'm sure it would be simpler and cheaper to just have a longer draw tube. 

[mikeDnight]

7 minutes ago, PGM said:

How does one calculate the right parts? I was planning to give the Tak focuser a chance before getting a FT focuser, but this might settle it.

Trial and error works for me! 

[mikeDnight]

There is no doubt in my mind that the feathertouch is far superior to the Tak focuser, but it is pricey.  Having said that, the Tak microfocuser isn't that cheap either, but I've found it more than adequate for my own needs. If I ever had the spare funds I would definitely consider a feathertouch replacement, as the telescope itself is definitely worth it. 

[PGM]

48 minutes ago, mikeDnight said:

Yes, it seems to be 81 that might be throwing your focus too far out. 15 should screw directly onto the draw tube and all should be well. I don't know why Takahashi insist on supplying these adapters. I'm sure it would be simpler and cheaper to just have a longer draw tube. 

Mike, it worked! Thank you! I noticed a small opening in the clouds, hurried to get everything in place and there was beautiful Luna in-focus and fighting the clouds ?

So just in case this helps someone else, the manual's DC diagram does seem to be incorrect - the diagonal branch should come before part 81, ie:
- w/ diagonal: 15+14+46+diagonal+EP
- w/o diagonal: 81+16+15+14+46+EP

So simple, and yet I never would have tried going against the manual. Lesson learned.

I can't thank SGL enough for the help I've been getting...

[mikeDnight]

On 15/12/2018 at 18:38, PGM said:

None I could find ?

 

Tak have definitely removed the alcohol warning so perhaps it was a mistranslation after all!?

Below is the original info from page 19 of  the user manual.

[Cleetus]

Assuming no accidents then it will be many years before you need to clean the lens. Dust can be removed by using a very soft make up brush.

[mikeDnight]

Bought in March 2015, I've cleaned my objective three times, getting rid of pollen and dew spots. Happily the coatings haven't slid off or been wiped off, and the lens still looks immaculate thanks to my trusty Caloclean - Solvent free - optical lens cleaning spray and cleaning cloth.  

[Cleetus]

Never experienced those problems Mike. All the years I've owned telescopes I can honestly say I have never had a pollen problem. I guess it may be dependent on where you live. Dew? Again, maybe I am lucky but, apart from a light misting once or twice, never had a dew covered lens. 

[mikeDnight]

Hi Cleetus,

I have a large privet hedge that surrounds my garden, and where I live there's a large park, plus woodlands and fields to my west and north extending for miles, so lots of grass etc. It's probably the privet hedge though that's the real problem. The dew spots are only minor and the FC lens has never completely sewed over. My larger refractors in the past all dewed over quite regularly, possibly due to me living close to a river.

[Highburymark]

On 15/12/2018 at 18:55, PGM said:

How does one calculate the right parts? I was planning to give the Tak focuser a chance before getting a FT focuser, but this might settle it.

I used the Tak focuser for two years (fitted with optional MEF fine focus). It was absolutely fine for normal loads (though I use mostly light eyepieces - Panoptics, Delites and Nagler T6s, with a T2 diagonal). I upgraded to a Feathertouch because I needed something more robust to handle a night vision stack, and heavy Baader binoviewer/Herschel wedge. It is simply superb - though I've been slightly shocked how far prices have gone up at many retailers since I ordered mine in the summer. So if you do consider an upgrade, shop around. You might still find one at the old price. And remember you do need to factor in an adapter, which isn't included in the advertised price on some websites.

Edited December 18, 2018 by Highburymark

[PGM]

I wonder if any Tak FC-100D owners could help me with yet another focusing problem. Previously I could not bring any eyepiece to focus, but @mikeDnight told me to remove the #81 adaptor and that solved it completely. Now I purchased a barlow (Celestron X-Cel ED Barlow 2x) and I can't achieve focus. I've tried with and without the #81 adaptor.
Any suggestions?

[John]

48 minutes ago, PGM said:

I wonder if any Tak FC-100D owners could help me with yet another focusing problem. Previously I could not bring any eyepiece to focus, but @mikeDnight told me to remove the #81 adaptor and that solved it completely. Now I purchased a barlow (Celestron X-Cel ED Barlow 2x) and I can't achieve focus. I've tried with and without the #81 adaptor.
Any suggestions?

Usually with a barlow in place, you need to find a bit more inwards focuser travel to reach focus. Is that your problem - lack of enough inwards focuser movement ?

The X-Cel ED barlow goes betwen the diagonal and the eyepiece I believe - is that where you are putting yours ?

Edit: could you post a photo of the focuser end of your scope as you have been using it so that we can double check on the componants. The Tak diagrams are all well and good but it's not all that clear which adapter is which.

 

[jock1958]

On 17/12/2018 at 14:22, mikeDnight said:

Bought in March 2015, I've cleaned my objective three times, getting rid of pollen and dew spots. Happily the coatings haven't slid off or been wiped off, and the lens still looks immaculate thanks to my trusty Caloclean - Solvent free - optical lens cleaning spray and cleaning cloth.  

I’ve had my 100DL less than a year and I’ve cleaned it once already (pollen & dew spots)

 

[jock1958]

2 hours ago, PGM said:

I wonder if any Tak FC-100D owners could help me with yet another focusing problem. Previously I could not bring any eyepiece to focus, but @mikeDnight told me to remove the #81 adaptor and that solved it completely. Now I purchased a barlow (Celestron X-Cel ED Barlow 2x) and I can't achieve focus. I've tried with and without the #81 adaptor.
Any suggestions?

Hi there. I went through similar issues with my 100DL and eventually arrived at the sweet spot using a TS optics 35mm extension tube and now all my 1.25” eyepieces including my Baader 2.25” Barlow arrives at focus.

I trod the same path as @mikeDnight ‘trial & error’

Theres an excellent thread on this forum that might be worth looking at, Tak FC-100 - a few questions  my input starts about pages 11 or 12.

Attached pic of the stock extension tube (which I don't use now) and the TS optics 35mm if that’s of any help.

Edited January 13, 2019 by jock1958

[Pig]

I must have been lucky with my DF as all my eyepieces work fine with or without the VIP Barlow, I have not tried using the extension but I do have a couple of click-locks in the light path that give a little extra length (all 2” configuration).

 I have no issues with focussing with or without the micro focusser unless I go very high mag (+400 X) when lunar observing then the micro helps. Mind you the DF has a more robust focusser being a 2”.

Using the Quark was a close call and I was only left with a couple of mm inward travel to spare ☀️

 

Edited January 13, 2019 by Pig

[PGM]

On 13/01/2019 at 10:21, John said:

Usually with a barlow in place, you need to find a bit more inwards focuser travel to reach focus. Is that your problem - lack of enough inwards focuser movement ?

The X-Cel ED barlow goes betwen the diagonal and the eyepiece I believe - is that where you are putting yours ?

Edit: could you post a photo of the focuser end of your scope as you have been using it so that we can double check on the componants. The Tak diagrams are all well and good but it's not all that clear which adapter is which.

 

Hi John, sorry for the delay, I thought I had already answered.
Yes, diagonal » barlow » EP.
That's right, I'd need more inwards movement. Anyway, I have 7 EPs, so I'm giving up on barlows for as long as I keep the stock DC focuser. I hate the idea of having to screw/unscrew adapters while watching something.

 

[Nakedgun]

The short-throw focuser on the DC can make finding the right combination a trying experience. Diagonals from different manufacturers will not all have the same focal length, nor will all barlows. I found this shorty barlow to be helpful. To use a "regular" length barlow I have to change extension combos.  An observing associate with a variety of ep/barlow/diagonal choices can save some time and aggravation.