Tak FC-100 - a few questions :)

[BGazing]

Interesting. You opted for it because your refractors are shortish, or because prism version was out of stock? I believe BBHS silver is even more expensive than the Zeiss prism variant...

[Stu]

I use a BBHS but in the T2 design. Good enough for all but the biggest 2". I don't really notice vignetting even on a 50mm 67 degree. Shorter optical path and lighter.

[BGazing]

1 minute ago, Stu said:

I use a BBHS but in the T2 design. Good enough for all but the biggest 2". I don't really notice vignetting even on a 50mm 67 degree. Shorter optical path and lighter.

No, I meant avoiding prism because of the medium focal length.

T2 can be configured into a 1.25 diagonal with proper adapters, I understand. Never tried the modularity, my 2 inch dielectric clicklock is a pain to dismantle (those small little things which fix the clicklock...aargh.

[Piero]

27 minutes ago, BGazing said:

Interesting. You opted for it because your refractors are shortish, or because prism version was out of stock? I believe BBHS silver is even more expensive than the Zeiss prism variant...

Not sure whether the Zeiss prism variant is cheaper when you add the clicklock and nosepiece. Actually the BBHS prism diagonal (which is Zeiss too) is a bit more expensive than the silver one. 

 

I opted for the BBHS silver mirror diagonal because:

1) it received a very favourable review by W. Paolini.

2) My Tak does not show any trace of spherical aberration, and it is suggested by some people that prism diagonal slightly overcorrect (which can be a benefit for slightly undercorrected optics as the prism would help balance spherical aberration).

3) Based on Baader's admin comment on the Baader-planetarium website (page: 2" BBHS prism diagonal), Baader reported that a prism might help when the first diffraction ring showed some red colour. In my Tak there is no red colour in the first diffraction ring in either inward or outward focus. 

4) After reading many comments on high quality prism vs mirror diagonals (dielectric and Vernon silver), it seems to me that the Baader Zeiss T2 prism slightly reduces light scatter and promotes the red shades on Jupiter. The BBHS silver mirror diagonal was also shown to increase the red tints on Jupiter, so to me the main difference appeared to be in this marginal increase in light scatter in the BBHS silver mirror vs the Zeiss prism. This is not enough to convince me to strongly support the prism over the silver mirror diagonal, though. Having observed with the BBHS for a while and also used a TV Everbrite dielectric diagonal, to my eye small particles of dirt depositing on the mirror and eyepiece quality affects more in terms of light scattering than the material making these two diagonals. 

5) Discussing red colour again, it seems to me that prisms are praised by members because of their "ability" to exaggerate the red colour tone, and therefore reveal Jovian's features a bit better. Whilst this is highly praised by planetary observers, nobody seems to discuss the downside of this effect on targets which might not respond well to this effect. I'm not in a position to discuss this due to my lack of experience, but I believe it would be interesting to have an extended comparison between diagonals on DSOs with coloured tints (e.g. extended and planetary nebulae) and see how contrast is affected. In terms of colours, the BBHS silver mirror is neutral (it's a mirror in the end!) and is able to show more red colour because of the larger reflectance range (390 to 2000nm) compared to standard dielectric mirror diagonal. The silver layer helps too I believe, but not so much as the Vernon silver diagonals were not reported to increase the red tone on Jupiter as far as I am aware.  

6) Comments by members on other forums and here, owning both the BBHS silver diagonal and the T2 Zeiss prism did not indicate enough evidence (actually any..) to make me favour one between the two. 

7) Finally, cost.. My BBHS silver mirror diagonal cost £330 new, a bit cheaper than the BBHS prism diagonal. 

[Piero]

1 hour ago, Stu said:

I don't really notice vignetting even on a 50mm 67 degree.

I believe you meant 40mm 67 deg. 

The field stop in a 50mm 67 deg should be around 58mm, and given the aperture of 35mm in the T2 Baader diagonal, vignetting should be well noticeable! Also, a 50mm 67 deg would require a 3" focuser! 

Edited January 20, 2018 by Piero

[Stu]

43 minutes ago, Piero said:

I believe you meant 40mm 67 deg. 

The field stop in a 50mm 67 deg should be around 58mm, and given the aperture of 35mm in the T2 Baader diagonal, vignetting should be well noticeable! Also, a 50mm 67 deg would require a 3" focuser! 

Thanks Piero, I actually meant 40mm 68 degree, a TMB eyepiece. My apologies, my fingers are clearly getting more sausage-like every day!!

[Piero]

24 minutes ago, Stu said:

Thanks Piero, I actually meant 40mm 68 degree, a TMB eyepiece. My apologies, my fingers are clearly getting more sausage-like every day!!

No problem!  

Out of curiosity, how's the 40mm TMB at the edge with your Tak?

There was one 40mm TMB in the classified earlier this year (maybe the one you picked up?), and although I was interested, I decided not to buy it because I was not sure how much astigmatism was visible in the last 10% of the FOV. Not having slower telescopes, it was a gamble for me. Its light weight is a great advantage though. 

[Alan White]

On 1/20/2018 at 11:07, Piero said:

Oh my oh my, that looks great Piero.
Feeding my want monster (Scope, mount, tripod and EP) with such images, really 
 

[Piero]

1 hour ago, Alan White said:

Oh my oh my, that looks great Piero.
Feeding my want monster (Scope, mount, tripod and EP) with such images, really 

Thank you Alan.  

It was pointing to M81 and M82. Lovely sight!

[BGazing]

On 20/01/2018 at 15:03, Piero said:

No problem!  

Out of curiosity, how's the 40mm TMB at the edge with your Tak?

There was one 40mm TMB in the classified earlier this year (maybe the one you picked up?), and although I was interested, I decided not to buy it because I was not sure how much astigmatism was visible in the last 10% of the FOV. Not having slower telescopes, it was a gamble for me. Its light weight is a great advantage though. 

40mm SW Aero/TMB clone is not that superb  on the edges in C8, so I assume it is not great in a lower f/l Tak  either. But it is a good, transparent eyepiece, and when I am using it I am usually not looking for the edges, but at nebulas. There are some notable exceptions...and yes, it is not Nagler 31, but it is very light.

 

 

[Stu]

31 minutes ago, BGazing said:

40mm SW Aero/TMB clone is not that superb  on the edges in C8, so I assume it is not great in a lower f/l Tak  either. But it is a good, transparent eyepiece, and when I am using it I am usually not looking for the edges, but at nebulas. There are some notable exceptions...and yes, it is not Nagler 31, but it is very light.

 

 

That's right, it does get a little scruffy towards the edge. I've not done any particular assessment if it, as like you I mainly use it filtered for nebulae for which it is very good.

[Axunator]

On 22.1.2018 at 01:00, Stu said:

That's right, it does get a little scruffy towards the edge. I've not done any particular assessment if it, as like you I mainly use it filtered for nebulae for which it is very good.

My Paragon 40 clone (SW Aero ED 40) was astigmatic enough at the edges in my FC-100DF that I eventually made the switch to Pan 41 - despite twice the weight and thrice the price. To me it was worth it, as the Tak + Pan 41 combo makes a truly splendid wide-field scope. But I can understand why someone would prefer the much lighter and more compact Paragon, especially since 90% of the field is really, really nice. 

[AstroSylv1]

On 20/01/2018 at 12:07, Piero said:

it's 2", but I have to say that given its size I expected it to be heavier (it's 451g).  

Hello Piero,

I am wondering, I use a Berlebach UNI 18 tripod, and a SkyWatcher Extension pilar from my old EQ5, it weights a ton, but it is very stable... do you think the UNI 19 with its pinion/rack column is just as stable ? For sure it must be lighter... I wonder how it compared in vibration damping, and on stability... I also have an AYO mount as well as the SW AZ GTi... I also wonder if the new Skywatcher small extension tube is providing the same stability as the super heavy, longer extension column...

Anyone knows if it is possible to convert a UNI 18 into a UNI 19 (if the column exists as a spare part ?) ??

 

Many thanks

[Piero]

Thank you Aki for your comment.  

I have a 35 Panoptic which is regularly used with my Tak and the 3 deg FOV it delivers are very nice. I'm sure your 41mm shows a lovely picture too, and the slightly larger FOV should help with very extended targets like the Veil, Orion's belt, and Alpha Persei moving cluster. 

[Piero]

2 minutes ago, disciplus55 said:

Hello Piero,

I am wondering, I use a Berlebach UNI 18 tripod, and a SkyWatcher Extension pilar from my old EQ5, it weights a ton, but it is very stable... do you think the UNI 19 with its pinion/rack column is just as stable ? For sure it must be lighter... I wonder how it compared in vibration damping, and on stability... I also have an AYO mount as well as the SW AZ GTi... I also wonder if the new Skywatcher small extension tube is providing the same stability as the super heavy, longer extension column...

Anyone knows if it is possible to convert a UNI 18 into a UNI 19 (if the column exists as a spare part ?) ?? 

Many thanks

 

Hello Sylvian, 

In my opinion the central column in the UNI 19 works really well. With my AYO II and Tak DF on top, fully extended legs and central column, vibration damping was just less than 1 second under windy conditions. When legs and central column are fully retracted, vibration damping is a fraction of second. When legs are fully retracted and the central column is fully extended, vibration damping is still less than 1 second (0.5s?). There is a bolt near the central column lever. That bolt can block the central column completely. I only use it at high power for maximum stability. 

I believe you can transform a UNI 18 into a UNI 19, but you need to replace the tripod base completely (so you only keep the legs). The central column and the tripod base seem to form a single component. I'd suggest to send an email to Marion at Berlebach. He will certainly help you. 

Piero

[iPeace]

3 hours ago, disciplus55 said:

do you think the UNI 19 with its pinion/rack column is just as stable ?

Berlebach describe it as helical gearing which acts as an automatic column brake. It's very stable.

[AstroSylv1]

Thanks all...

[F15Rules]

On 21/01/2018 at 22:28, BGazing said:

40mm SW Aero/TMB clone is not that superb  on the edges in C8, so I assume it is not great in a lower f/l Tak  either. But it is a good, transparent eyepiece, and when I am using it I am usually not looking for the edges, but at nebulas. There are some notable exceptions...and yes, it is not Nagler 31, but it is very light.

 

 

I recently acquired the TS ED 40mm version (says Paracor on it).

I really like it. No, it's not an XW 40mm (and who DID snag that mint beauty of Roger Vines' for £399 on UKABS last week??!!), but it's sharp to about 85% out on my FS128. I use a driven eq mount so a little edge distortion doesn't bother me for the objects I use it on. A lovely 69 Deg field at 40mm showed me a wonderful view of the double cluster at the weekend, real 'diamonds on velvet' style.

Mine is also light for its' size and quite nicely made. The rotating eyecup is a useful comfort feature..Recommended.?

Dave

[AstroSylv1]

Sorry for the XW 40, I was stupid enough to trade mine months ago, thinking I could live without it, and I was wrong, I had to find one again... sorry sorry...

[Piero]

I think the XW 40 is probably the only eyepiece I would get to replace my 35 Pan. Very remote chance though! 

[AstroSylv1]

Here is a DL on SW AZ GTi + EQ5 extension column and UNI 18, very stable and super heavy...

 

[jetstream]

9 minutes ago, disciplus55 said:

Here is a DL on SW AZ GTi + EQ5 extension column and UNI 18, very stable and super heavy...

 

What is the settling time of this set up?

[GavStar]

28 minutes ago, disciplus55 said:

Here is a DL on SW AZ GTi + EQ5 extension column and UNI 18, very stable and super heavy...

That is some tripod and pier to set the az gti on ? 

Imo the worst thing about the az gti is the small single bolt to hold the dovetail bar - a safety screw is definitely needed! 

 

Edited January 23, 2018 by GavStar

[Piero]

28 minutes ago, GavStar said:

That is some tripod and pier to set the az gti on ? 

Imo the worst thing about the az gti is the small single bolt to hold the dovetail bar - a safety screw is definitely needed!

I installed two M8 safety bolts on each side of my dovetail (which it seems exactly like Sylvian's one). 

Also, they perfectly for hanging weights, balancing the scope at every altitude when heavy eyepieces are used. 

[AstroSylv1]

Good idea Piero, I will have a look at that too...

settling time is good, but I still haven’t pushed magnification since mid October due to the horrible weather conditions... :-( but it is anyway less than a second.