2nd Light on a Tak FC-100 DC - testing 2" vs. 1.25" mode.

[SuburbanMak]

Well that was the most fun I've ever had on a night of dodgy skies (astronomically speaking). 

I'd been keeping a hopeful eye on the Met office cloud cover forecast for the last couple of days and for a time it looked as though Winchester would get a few clear hours tonight. There was a sheet of cloud set to bisect the country NW-SE and heading in from the West as the night wore on and as of this morning they were still saying I'd stay on the right side of that from around eleven through most of the night.  Inevitably this got revised to a forecast that had me under cloud the whole time.   So as the sky, which had been miserable all day here, rapidly cleared while I was on my last of many Zoom calls today, I resolved to get out as soon as dusk fell and snatch whatever views I could.  

I was up for some serious, scientific equipment testing - not "playing with my new toys" at all, as some around here may have playfully  put it...

I had no particular objects in mind, more of a gear test, figuring out what works best from an eyepiece perspective in my lovely new Tak FC-100 DC.  I'd taken delivery yesterday of a 2" Baader Clicklock visual back and was keen to find out how the 'scope would work in 2" mode - in particular with a Stella Lyra 30 mm UFF, giving a FoV of 2.8 degrees - massive compared to my familiar Mak 127.   I then wanted to check out if I could achieve focus with all my other eyepieces in this format.   

Everything screwed together as planned, I plugged in my TS Optics 2" Dielectric diagonal and a quick test through the window on my handily placed reference church spire 1/4 of a mile away looked like focus travel (which is very short on this 'scope) would be in the zone. The diagonal and 30mm UFF make for quite a lump of extra weight so I rebalanced the scope, requiring about 5 inches shift of the balance point back toward the focuser. I tested the new weight on the AZGTi and it slewed about quite nicely but was groaning a bit lifting the focuser end back up after steep elevation, hmm....

When I actually got outside the only thing I could pick out of the high cloud was Mars, and yes, focus was achieved with the 30mm UFF. Next up the Baader Zoom and, whilst noting how fast Mars has got to be a really tiny disc again, I confirmed I could reach focus across its range. So far so good - 2 inch mode working nicely.  I've somewhat blown my budget of late so widefield short FL eyepieces are on the Christmas list, for the time being I will be Barlowing to achieve higher powers.  With the Baader Hyperion Zoom 2.25 Barlow, the 24-8mm Zoom turns into a  (roughly) 10.7-3.5mm eyepiece giving magnification up to 208x in the f7.4 FC 100 DC.   Only problem was, with the 2" Diagonal in I couldn't achieve sufficient in focus. Hmm again. 

Same story with my 1.25" Hyperion 24mm 68 degree  (part of the problem could be that I need a lower profile 1.25" converter - I can't find the one that came with the diagonal which did slot in closer buying an extra 10mm or so of in-focus). 

Dinner & child ferrying duties intervened and when I was able to get back out it was both properly dark and largely cloudy.  Nevertheless the Pleiades was available high-ish to the SW above the roofline and its always my reference FoV object when playing with Eyepiece combinations both in the real world and on Stellarium.  The Stella Lyra delivered a nice view, flat to the edge and setting the cluster in its rich background field. I compared with a Baader Hyperion Aspheric 31mm and, although the view on axis bright, contrasty and maybe more stunning than the Stella Lyra, the "edges" still begin 1/3rd of the way into the field. I think it may be time to move this one on to someone who has a big long focal length SCT where I am sure it would work really well!  

I noticed that the additional weight of the 2" diagonal and chunky 30mm EP, coupled with the longer tube-overhang from the clamshell compared to 1.25" mode, was contributing to more vibration and general wobbliness.  Not terrible, but noticeable.  I am after all running this on an AZGTi which with all this gear on board is heading more toward its weight limit of 5kg and fighting the greater moment. I'm also on the lightest of the Berlebach tripods. Hmm again. 

My new Morpheus 12.5mm came to focus nicely however and gave a really lovely view of Almach despite the haze and its dodgy position just above the roof line - colour contrast was great and the presentation of doubles in the Tak is stunning, little balls with perfect diffraction rings, very satisfying! 

Cold by this time I went inside for a cuppa and a think, not quite as blown away by the views in my new Tak as I had been first time around.   

Maybe the TS Mirror diagonal is not quite up to the sharpness of the 1.25" Tak Prism, maybe the extra weight & imbalance, maybe that the 2" set-up doesn't quite look as pleasing to my eye - combination of factors, but I decided to go back to the 1.25" back and Tak Prism, rebalance the 'scope and head out for another session and a peek at the rising moon. 

Everything immediately worked better. A bit sharper, better balanced and much better damped and most importantly all my eyepieces able to reach focus. The Baader Classic Ortho 18mm was just running out of back focus but its so light that there's no problem in just clamping it a little further up the barrel to give the travel you need.  The Barlow functioned amazingly well in this format with all EPs including the Zoom - so I have magnification up to 208x sorted for the time being and really clean star images, I shall be revisiting a lot of doubles in the coming sessions!  

There was cloud everywhere but chasing the holes Mizar, Castor and Algieba all were just superb, so bright and tight.  

The Moon too looked superbly crisp, (I will figure out exactly what I was looking at later) - best view in the Morpheus 12.5 both in its natural state (59x) and Barlowed (133x). Hugely immersive, what a fab eyepiece, that Christmas list is getting pretty heavy! 

In the end the cloud did defeat me, but a great session despite the iffy skies and a good decision for now on 2" vs 1.25" given the mount & eyepiece combination I have today. Effectively I am giving up 0.6 degrees of FoV ( I can still get 2.2 degrees which as a Mak user is HUGE!) and benefit from all that sharpness, lightness and stability with the Tak prism. It also looks a bit nicer too, not that that's important obviously.

While writing this, I noticed that there's another gap in the cloud, I wonder if it's getting too late to...

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Edited March 11, 2023 by SuburbanMak

[Littleguy80]

Great report and interesting results in 2” mode. The moon pic is fab and no doubt doesn’t do justice to the views through the eyepiece  

[SuburbanMak]

Thank you! Yes, the pic is just an iPhone snap wobbling over the eyepiece. 

I think the 2” finding is peculiar to my using the AZGTi/Report 312, it’s just pushing a lightweight setup a bit too far. 
 Also the TS 2” diagonal is not quite in the same class as the Tak prism (I could see the slight difference in sharpness) so taken together it just feels to me like 1.25” is the best way to go with what I have right now.  Figure out the focus travel thing, add a beefier mount and an optimal 2” diagonal and I’m sure the ‘scope itself would be equally amazing in 2” mode. 

[jetstream]

@SuburbanMak Excellent report.

For you to notice the difference in sharpness immediately, the difference is significant IMHO. I have zero doubt that when you get a high spec 2" diag  the views will equal the Tak prism. Baader BBHS comes to mind.

Congratulations again for owning this fine telescope.

Gerry

[JeremyS]

I agree with Gerry, the 2-inch BBHS is wonderful. But there’s plenty of time to build up to that. Enjoy it in 1.25 inch mode for a while. Much easier on your AZ GTi.

It will take a while to find out how you enjoy using the Tak best. And you will need some long clear spells for that.

[jetstream]

@SuburbanMak your scope might also show up differences in sharpness between eyepieces once you get playing around - its the excellent optics in the scope that will show this.

 As Jeremy says -no rush to get a bunch more stuff though, you have an excellent prism diag and nice EP's.

[Stu]

@SuburbanMak nice, interesting report. Like you I found the AZGTi could take the FC100DC but was a little on the limit.

Regarding back focus, the Tak has a little trick up its sleeve, revealed in these threads. Should help you out.

As a compromise between 1.25” and 2” diagonal I normally use a T2 BBHS mirror diagonal. It has a shorter optical path so saves distance, but can actually take most 2” eyepieces. Technically it does vignette the widest of them but our eyes are not that sensitive to this so I don’t normally notice.

Have fun!

[SuburbanMak]

7 hours ago, jetstream said:

@SuburbanMak Excellent report.

For you to notice the difference in sharpness immediately, the difference is significant IMHO. I have zero doubt that when you get a high spec 2" diag  the views will equal the Tak prism. Baader BBHS comes to mind.

Congratulations again for owning this fine telescope.

Gerry

Thanks Gerry - it’s not that views with the TS were bad, just not quite the “ahh!” moments I was getting with the Tak prism.  Sky conditions were quite poor too. Another one for the Christmas list! 

[SuburbanMak]

@jetstream - indeed no rush, it’s fab as it is for now and there’s years of upgrades to plan & enjoy! 

[SuburbanMak]

6 hours ago, JeremyS said:

And you will need some long clear spells for that.

Thanks @JeremyS Amen to that!  
Recommendations for the BBHS coming in from all sides - it goes on the list next to all those Pentax & Morpheus EPs, Binoviwers, Herschel wedge etc etc  

[SuburbanMak]

Thanks @Stu really helpful. I have to say there is an absolute goldmine of information in here on this ‘scope!  An added benefit given all this cloud  
 

 

Edited March 11, 2023 by SuburbanMak