Maxbright IIs on FS-128

[Stu]

I had a play around with different bits of kit tonight and using a x2.6 GPC in the top of the Baader Zeiss T2 Prism and it came to focus with loads to spare in the FS-128.

I had a short view of the Moon, with rather grubby eyepieces but all looked good. I cleaned the eyepieces and by the time I came out it had clouded over. Another time.

[mikeDnight]

 I see uou finally bought that goat Stu, or perhaps managed to get your mower repaired. It looks good anyway, especially with your 128 soaking up the Moon beams. I've never used a GPC and wonder if there's any noticeable advantage over a barlow, other than the barlow giving greater amplification?

I've been enjoying observing the Moon at low power over the last few nights using the FS128 and Maxbright ll's, but without a barlow. There's something quite beautiful about a low power moon through a binoviewer. To reach focus without a GPC or barlow I connect the Maxbright directly to the prism. The images below show my 25mm Parks Gold, but using the Baader adapters on the Tak draw tube, even my 35mm's come to focus with a little travel left.

Edited May 31, 2023 by mikeDnight

[Stu]

Thanks Mike, looks great. I understand that a GPC corrects for the aberrations caused by binoviewers so should result in less CA etc. no sure if it is a visible effect though. I often use both a GPC and a Barlow (AP Barcon) and see no degradation from either.

I’m waiting for stock of the necessary adaptors currently so am limited to 1.25” with the longer light path of the standard setup. I will replace the focuser sometime soon too, with apologies to all Tak genuine only fans 🤣. The stock focuser doesn’t quite do it for me in terms of fine focusing.

Cloudy today, but the forecast looks good beyond that.

[Highburymark]

I find the GPCs are very high quality. I use the 2.6x permanently in my solar scope (TV85) and 2.6x and 1.7x for binoviewing the Moon and planets. Apart from the quality, correction for CA and SA, they are also perfectly designed to fit into the T2 system. But I do wonder if much of the reason they correct for aberrations is because they are simply slowing the system down, just like any barlow. So in a relatively slower scope like the FS128, any advantage might be marginal? TBH, I find little difference between using GPCs, AP Barcon, VIP and Powermate - have never noticed any problems with any of them.

[Stu]

9 hours ago, Highburymark said:

they are also perfectly designed to fit into the T2 system.

It’s a little embarrassing, and I’d ask you not to tell anyone else (😉), but until recently I didn’t realise that the GPCs screwed into the top of a T2 prism or mirror! I had always used them screwed into the binoviewer or another adaptor, so I’m pleased I read a thread on here which let me know how I should be doing it!

[John]

I really ought to give binoviewing another try I think.

My 130mm LZOS is ideal for the purpose having an extension tube that can be pushed in so BV's come to focus without the need for a barlow / transfer lens or whatever they are called.

I might actually be able to see some cloud structure on Venus using 2 eyes ! 🙄

 

[F15Rules]

13 hours ago, Stu said:

Thanks Mike, looks great. I understand that a GPC corrects for the aberrations caused by binoviewers so should result in less CA etc. no sure if it is a visible effect though. I often use both a GPC and a Barlow (AP Barcon) and see no degradation from either.

I’m waiting for stock of the necessary adaptors currently so am limited to 1.25” with the longer light path of the standard setup. I will replace the focuser sometime soon too, with apologies to all Tak genuine only fans 🤣. The stock focuser doesn’t quite do it for me in terms of fine focusing.

Cloudy today, but the forecast looks good beyond that.

As you know, Stu, I use the same setup shown in Mike's  photos..and I know you're  planning to get the same adapters when available..

The photo below shows my FS128 using the Baader Adapters, with Maxbright IIs and a pair of Tak Abbe 12mm orthos, at perfect native focus with no barlow or OCS and probably about 12mm or more of spare infocus left.

The MEF3 microfocuser is fitted to the standard 2.7" Tak focuser assembly, and the small black microfocuser fine focus knob can be seen to the right of the silver aluminium standard right hand side knob in the photo below.

I find the Tak MEF3 microfocuser retrofit upgrade to be excellent, and I understand that users of the More Blue equivalent microfocuser rate it highly as well.

I've never used a Feathertouch, although their reputation speaks for itself: I simply couldn't afford the c £1k I believe one would cost including adapter for my FS128, nor do I feel any such additional investment would be worth any potential gain I might get.

I'll watch with interest though if you buy one and will be interested to hear your thoughts😉👍..

Dave

 

Edited May 31, 2023 by F15Rules
Additional text info

[Stu]

Actually managed some decent views this evening before the cloud settled in. The seeing still wasn’t brilliant, but it was certainly allowing the detail to come through. Schröter’s Valley was as good as I’ve seen it for a long while, etched in sharply with the twists and turns clearly visible. Aristarchus was showing plenty of detail within the crater, on the wall and the crater floor where it was illuminated. Very nice!

[Highburymark]

On 31/05/2023 at 21:01, John said:

I really ought to give binoviewing another try I think.

My 130mm LZOS is ideal for the purpose having an extension tube that can be pushed in so BV's come to focus without the need for a barlow / transfer lens or whatever they are called.

I might actually be able to see some cloud structure on Venus using 2 eyes ! 🙄

 

If you do decide to give it another go John, I’d suggest trying something like the Maxbright II, with decent eyepiece holders. I have wondered in the past if many unsuccessful attempts to binoview are hampered by poor eyepiece collimation. I’d suggest starting with low power and comfortable eyepieces on the Moon or a daytime target, and taking things slowly to train your eyes on easy targets. Ideally it would be best if you could find an experienced bv observer to help you - and let you use their kit. I’m sure with the right gear and guidance you would see binoviewing in a new light.

[Franklin]

My new Maxbright II's can reach focus in the SD115s, F/7.7, 890mm fl but I either need the 1.7x GPC between diagonal and binoviewer or the 1.25x GPC between diagonal and scope. Unfortunately I can't get native focus with this set up and that's using the Baader 32mm T2 prism with direct connection, short of chopping down the ota of course but that is NOT happening. Being able to get native focus with the big Tak FS128 is an excellent result and I am not at all jealous.

[Franklin]

On 30/05/2023 at 22:50, Stu said:

I had a play around with different bits of kit tonight and using a x2.6 GPC in the top of the Baader Zeiss T2 Prism and it came to focus with loads to spare in the FS-128.

If you lose the clicklock and directly fix the Maxbright II to the diagonal you will save loads of focus judging by your pictures.

Edited June 2, 2023 by Franklin

[Stu]

10 minutes ago, Franklin said:

If you lose the clicklock and directly fix the Maxbright II to the diagonal you will save loads of focus judging by your pictures.

Thanks Tim. Yes, I think there is more playing around to do. One thing to bear in mind is that my main use of binoviewers is for high power lunar and Solar viewing, and to achieve that I often use both a GPC and a Barlow with longer focal length eyepieces to achieve the power. I’m less bothered about lower power views as I tend to prefer the star images in a single widefield eyepiece.

[F15Rules]

55 minutes ago, Franklin said:

My new Maxbright II's can reach focus in the SD115s, F/7.7, 890mm fl but I either need the 1.7x GPC between diagonal and binoviewer or the 1.25x GPC between diagonal and scope. Unfortunately I can't get native focus with this set up and that's using the Baader 32mm T2 prism with direct connection, short of chopping down the ota of course but that is NOT happening. Being able to get native focus with the big Tak FS128 is an excellent result and I am not at all jealous.

Hi Tim,

Can you post a close up picture of your 115s with MB II's in place?

From your last post to Stu I'm assuming that you too have removed any clicklock from the optical train from in front of the T2 prism?

It's that area where I have saved the most consumption of in focus..the parts I needed to get were this one..

..the Tak Adapter M72/M68 (part#2558230) and Baader Tak Ultrashort clamp (part#2458196).. these, according to Baader, have a combined optical length of 22mm..

...now, there is this adapter

https://www.baader-planetarium.com/en/accessories/adapters-imaging-accessories/eyepiece-clamps/baader-2"-four-in-one-adapter-m68-(zeiss)--2.7"-(a.p.)--m60-(vixen)--m56-(synta).html

which may do the job for your Vixen..according to Baaders specs, this adapter has a total optical length of 24mm - just 2mm more than the parts I use on my FS128..and I have about 12mm infocus to spare natively with my set up.

Got to be worth looking  into Tim?

On the T2 prisms, its worth mentioning that the Baader Specs state that the T2 Zeiss BBHS prism (which I use) has an optical length of 38.5mm and a free aperture of 34mm.

By contrast, the ordinary T2 prism has an optical path length of 35mm, so 3.5mm LESS than the T2 Zeiss BBHS unit, but a free aperture of 32mm, ie 2mm LESS than the T2 Zeiss  BBHS unit..

..so, the Zeiss prism takes up 3.5mm more in-focus than the standard T2 prism, but will vignette long focal length eps less than the standard T2. This matters more if you use low power long FL eyepieces for binoviewing, but less, if like Stu, you use high powers more often. 

Hope that makes sense!🙂

Dave

[Franklin]

Here you go Dave, a couple of pics of my bino set up. I don't think it's possible to get any closer, apart from saving a few mm by using the Vixen stock visual back, but having just a couple of set screws it's not really man enough for the bino plus eyepieces imo. I have an APM compression ring, three screw on which holds solid but adds about 5mm over the Vixen. Like this, the 1.25x GPC in the diagonal top leaves me about 10mm short but placing it before the diagonal gets the focus. I've now got a 1.7x GPC as well which works great after the diagonal, which I kind of knew, as that's what I used when I had the original Maxbright.

It would be nice to use the bino's at native but unfortunately Vixen didn't think of this when they put their ota's together, not like the Taks with their removable focus extension tubes.

Either way I'm over the Moon with my kit at the moment, the Maxbright II is very impressive and a big improvement with their clicklock holders and cleverly designed focusers over the originals. The SD115s is and has been my dream scope for quite a while as you know.

 

IMG_4148.CR2 IMG_4149.CR2

[Franklin]

On 31/05/2023 at 19:24, Stu said:

but until recently I didn’t realise that the GPCs screwed into the top of a T2 prism or mirror! I had always used them screwed into the binoviewer or another adaptor,

Regards this, you must be careful which way around the GPC is placed, so much so that Baader supply two versions each of the 1.25x and the 1.7x. One each for placing up in the binoviewer and one each for placing down in the T2 diagonal. You can flip the element over yourself and it's quite easy if you have a lens spanner. The two different positions of the GPC means that it will be reversed and it's important to get it the correct way around. Suffice to say, the convex side of the GPC needs to pointing sky-ward in either instance.

[F15Rules]

Cheers Tim.

I can now see that you have the shortest possible light path on your setup. That's a shame that you can't bv native, but the overall fabulous features of your SD115S mean it's not at all a major setback.

Thanks for sharing the photos!

Dave

[Franklin]

Here it is now out cooling, waiting for the Moon!

 

IMG_4152.CR2

[JeremyS]

Is there any reason why you are sharing your photos as attachments, Tim @Franklin?
Makes it a bit of a hassle to view.

[Franklin]

Just now, JeremyS said:

Is there any reason why you are sharing your photos as attachments, Tim @Franklin?
Makes it a bit of a hassle to view.

Tee-Hee Jeremy. Yes, I was just wondering that myself and I now realise my Canon 600D was still set in RAW format from the other night when I attempted to take some astro-pics!

It is now back on JPEG and here you are.