For ST 120, the key is the OEM focuser. It is way too long. I cannot reach focus at all if I want to use 0.5x focal reducer with NVD Micro or NVD PVS-7. Once you replace it with GSO linear focuser, everything works out with plenty room to spare.
PVS-7 w/ 2" reducer? Is it your diagonal holding you back?
Posted 28 November 2015 - 09:00 PM
cw00, do me a favor if you can. Which GSO linear focuser are you using and can you measure the length of the focuser body? For instance, the Orion 120ST focuser body, from where the focuser attaches to the scope to where the tube enters the focuser is 3.5 inches. How long is your GSO focuser?
There is one GSO linear for a 96.6mm flange and one for a 112.5mm flange, I believe the 112.5mm is the most direct fit for a 120ST, but am not sure. Am also not sure if both body lengths are the same. It looks like the 96.6mm diameter one might be shorter.
Any info would be greatly appreciated. Thanks
Posted 28 November 2015 - 09:21 PM
I think my linear bearing (TS Monorail) uses the 112.5mm. I think the 96.6mm are for fitting on the ST80
Posted 30 November 2015 - 02:57 AM
Here is side by side comparison between Orion ST120 stock focuser and GSO linear focuser.
Orion stock focuser, 5.7 inches from where the focuser attaches to the telescope to where the diagonal would attach to the focuser (on the top, not attached to ST120);
GSO linear focuser, 3.5 inches (attached to the ST120).
Using GSO linear focuser, you will need an extension tube for some eyepieces without focal reducer.
Posted 30 November 2015 - 03:09 AM
From GSO linear focuser page on ScopeStuff website:
- Adaptor Ring for Crayford Refractor Focuser on 3.8" ID Tubes (ED80, ED100, 102mm Skywatcher, Celestron, Orion, Konus, etc)
- Adaptor Ring for Crayford Refractor Focuser on 4.4" ID Tubes (120mm Skywatcher, Celestron, Orion, Konus, etc)
- Adaptor Ring for Crayford Refractor Focuser on 5.4" ID Tubes (150mm Skywatcher, Celestron, Orion, Konus, etc)
- Adaptor Ring for Crayford Refractor Focuser on 5.125" OD Tubes (Meade AR5, Antares 1208, 12012, etc.)
- Adaptor Ring for Crayford Refractor Focuser on 6.175" OD Tubes (Meade AR6, Antares 1529, etc.)
So the 112.5mm flange is for ST120.
Posted 30 November 2015 - 04:03 AM
Mine is put on a little different. Still uses the collett of the original focuser then the adapter. Not quite as short as yours. Which is why it comes out 4.3" instead of 3.5"
I don't need an extension for regular focus and only about 8mm room to spare with reducer. But it works.
Posted 30 November 2015 - 02:00 PM
Thanks cw00, and VDN, always. That picture really shows the difference. I will have to consider that GSO, looks like you have a 96.6mm GSO with a ring adapter, or am I seeing that wrong? I was pretty sure the 112.5mm was a direct fit, what I can't tell for sure is if the 112.5mm and 96.6mm bodies are the same length, would want to get the shorter one or the 112.5mm if the bodies are the same length.
Will continue to look at the focuser and diagonals. I can't get two of my diagonals apart on the eyepiece side so I'm wondering if I should take a chance on torquing the whole diagonal out or look for another diagonal.
Oh well, experimenting continues. Thanks a lot for the focuser info, I could not find body length info (or schematics) on any of them, but that picture shows plenty.
Posted 30 November 2015 - 02:25 PM
Sorry I should have provided the following info too. Again, from Scope Stuff website:
The Refractor Linear Bearing Crayford Focusers have 2" travel, the flange outside diameter is 3.4" to fit 3.5" OD tubes, drilled and tapped for three M4 screws. Weighs 1.9 lbs. Minimum in-focus length from scope tube to 2" barrel is 3.6".
Posted 30 November 2015 - 04:58 PM
I wanted to show the difference in the way we have the linear bearings mounted too
Posted 30 November 2015 - 07:10 PM
Gotcha. It's very helpful to see these things, I'd probably be shooting for something along the lines of what cw00 has going, if I even need to. I did achieve focus with a 45° diagonal and 0.5x reducer, but it's not as nice, theoretically not as bright, as my other diagonals. But my other diagonals don't want to come apart so I am debating messing with them further, don't want to tear them up trying to get them apart. Already broke a strap wrench trying to take one apart and am not sure about getting a stronger strap wrench and maybe torquing the entire diagonal out of shape.
The experiment continues and the focuser info is very good. It's always nice to have options. Pathetically dreary weather for about the last five nights anyway, no rush to ruin a diagonal that I can't even take outside and experiment with, yet.
Posted 30 November 2015 - 08:03 PM
Yes, scopestuff has this as mentioned by cw00:
Adaptor Ring for Crayford Refractor Focuser on 4.4" ID Tubes (120mm Skywatcher, Celestron, Orion, Konus, etc)
its easy to add extensions for use without reducer if needed. I might get one of those adapters too and take the collet off to get that breathing room. This might be a solution to using a BV with no OCS and two micro housings too. Seriously considering getting a matching micro housing and taking tube out of my M942 monocular, putting it in a Micro housing, and try a Williams Optics or similar BV. Wouldn't get to use use a reducer with a binoviewer but F/5 still fast and wide.
My Litton M942 could then be modified like cnoct's M944 with a gain pot and use a variable gain MX11769 tube that is in most PVS-14's.
Much later down the road of course. No more purchases for me for a little while.
Posted 30 November 2015 - 08:59 PM
You might want to consider an Arcturus Binoviewer because "2. There are no setscrews used on these binoviewers. The eyepieces are held in place with self centering brass compression rings. Brass will stand up to the weather much better and the self centering design keeps the eyepieces in good collimation with no off-axis bias." Am pretty sure the WOs and Celestron types use set screws so that makes the Arcturus a cut above. YMMV, but you should check it out.
Eddgie can tell you all about the BVs, but think he got rid of his Arcturus for other reasons. Am pretty sure a BV would work great in a 120ST, if you can get focus in the opposite direction, probably.
Posted 30 November 2015 - 09:05 PM
Getting a matching pair of NVD Micro ULT for binoviewing in a telescope or for use in a bino scope will be a dream setup.
Posted 30 November 2015 - 10:02 PM
Well, these won't be matching tubes, but I would put the weaker tube on dominant eye side so they match up better. I think the 1.25" nosepiece on the micro would be fine for use in a BV. Even though 27mm fl eyepiece, they are only 40° AFOV. The 21mm clear aperture should be close enough to get a good view. Given that it is a shortening of 2.2" using the scopestuff adapter plate and linear bearing focuser over the OEM length, It just might be enough to not need an OCS with BV.
Would cost me an ultra housing and the adapter plate is all plus a lower cost BV. Probably a better view than AT72ED with two eyes working on a beam split 120mm
Just thinking out loud on this though. We will see if I can do it at some point. My monoculars do not come to focus in my binocular telescopes with the short helical focusers, but this might be a neat solution. Would be neat if I could get it to work in the 6", but think that would be a stretch without cutting tube.
Posted 30 November 2015 - 10:35 PM
That sounds wild. I didn't understand what you were getting at until cw00's post #38. Sometimes when I first read your posts they are too much for my tiny brain, and my large brain too.
If you had the controllable gain you spoke of that would probably also help to match tubes, in essence. That setup might even give you some of the 3d effect that many BV users experience, doubtful, but who knows. The whole idea sounds like NV BV nirvana.
Outrageously cool idea, but would it work? And although I don't consider night vision stuff to be that expensive when compared to many an eyepiece collection and telescope setup, that would be expensive if you started from scratch.
Can't over recommend two-eye viewing, especially with regular scopes.
Edited by outofsight, 30 November 2015 - 10:36 PM.
Posted 30 November 2015 - 10:52 PM
Oh the variable gain would be a separate thing entirely. Variable gain is a neat way to lessen noise by turning gain down.
What I meant was that I already have a micro with mx10160 tube that is high performance. I also have a MX10160 tube I would take out of my M942 monocular. At that point I would have a tube to put in a micro housing ($550). With purchase of Micro housing and putting that less high performance tube in it that I just took out of the Litton M942, I would at that point have two NVD Micros, one high spec, one less than high spec. I put the high spec to my weak eye and the less than high spec to my dominant eye, and would probably not notice much difference in tubes, allowing easier merging. Then I change adapters to scopestuff adapter ($44) and have a 120ST that is 2.2" shorter than OEM 120ST. I buy the less expensive BV's (approx $199) and use the two micros in it in the configuration mentioned - weaker tube to dominant eye, stronger tube to weaker eye - and get close to matched pair.
In theory anyway.
Sometimes I think about stuff too much. Haha.
Would be very expensive to start from scratch to get all that. I'm most of the way there though.
Edited by Vondragonnoggin, 30 November 2015 - 10:53 PM.
Posted 01 December 2015 - 12:32 AM
Oh yeah, I got the basic idea as soon as I read cw00's post. Just thought the variable gain might help with tube matching in some way, but yeah, I don't know what gain does on these things because I don't have one with gain control. There might be some other filter ways, or something, to help the tubes to match. Or you might find that the tubes are close enough already with the eyes' and brain's ability to compensate for stuff. It's something you'd just have to try and mess around with.
But the basic idea, when I got it it really hit me like WOW, because I really like binoviewers and have always had at least one since I started having any quality telescopes. I suppose that's part of why I don't consider NV overly expensive because I think in terms of a Denkmeier and that will immediately set you back the cost of a nice scope or a decent night vision device.
When I got the concept it just blew my mind. Even though a PVS-7 is bi-ocular, I think what you're talking about might be substantially better, and not just in terms of tube resolution, etc., but in terms of eye independence and whatever else is entailed - I have no full idea because it's just something that would have to be tried.
Also, when it blew my mind and I brought up expense I was immediately thinking of a perfectly matched system with NVD Micros. To really try it out you'd want an optimal system. I like the PVS-7 a lot, but if I could get closer to what I've seen through some BVs with high resolution NV... Something I'd want to see and try.
I hope you can check out something along those lines in the next year or so. Even if it doesn't meet the highest expectations you'll have fun trying. The basic concept sounds like a very promising idea and if it pans out in the 120 you can probably figure out something for the 6". Definitely something to consider and you're already more than half way there!
Edited by outofsight, 01 December 2015 - 12:33 AM.
- Vondragonnoggin likes this
Posted 01 December 2015 - 12:49 AM
I believe I have seen pics posted of jdbastro's BV and both pairs of NVD Micro's and pairs of Collins I3's. Not sure if he had shortened tube for that fast a focal ratio though. That's the guy taking amazing video and pics with both white phosphor and green phosphor. He had matched tubes I believe too. Very high spec matched tubes. Was droolworthy on the pictures of the devices. When he buys devices, he doesn't go budget, he goes best. I'm more budget oriented, but if I could go best, I would. Ahhh, someday maybe. Once the current devices I have get all used up....
That could possibly be never of course. One thing about having several devices and rotating use, is that you extend the life of the device by less use.
Or I could sell off some to get better, but I so rarely sell items. The only gear I have ever sold since starting the hobby was a package deal for AP when I decided AP wasn't for me and too much work, not enough fun. All the rest I have kept. Sold a dob too that wasn't getting used, but that is what got me into refractors thankfully. Dob was fun but I am a smaller scope enthusiast due to back injuries.
I admire his methodology though. He goes for getting best results. Even viewing locations. The proof in the pudding too. I think some of the best night vision stills of astro objects I have seen. The time taken to capture details with his equipment being mere fractions of what it takes with dedicated rigs imaging hours. Knows his equipment well and gets the most out of it too.
I am more the quick and dirty route to lazy astronomy but see a ton.
One thing I really like about reading about others gear and techniques, is that it is so varied that anyone reading wanting to start has a good chance of finding something they like.
One reason I am thrilled with seeing others liking the 120ST. It has been giving me great results and as a bonus, is completely easy setup and highly portable. Now can have some others knowing exactly what I am seeing too.
Edited by Vondragonnoggin, 01 December 2015 - 01:04 AM.
Posted 01 December 2015 - 01:20 AM
Thanks cw00 for pics and links too. I might just have to copy that setup. Great find on scopestuff adapter!
When I started the thread, really thought it was diagonal helping and in my case it was slightly, but the focuser and which adapter you use really is what will do it. The short scopestuff adapter would make any diagonal a viable match.
Posted 01 December 2015 - 10:41 AM
Well, looks like I better order the scopestuff adapter. I'm a step closer to my theory. WO BV's came up in classifieds for a good price. I bought them.
Posted 01 December 2015 - 11:00 AM
Pulled the trigger on scopestuff adapter just now....
Posted 01 December 2015 - 05:26 PM
I've seen that first thread and didn't think too much about it, probably 'cause I just wasn't thinking and probably 'cause it wasn't connected to a telescope and I just barely knew anything about NV at the time.
But that second thread and that last post, #12, by jdbastro, that's the stuff. Will look at that thread very carefully, especially since, I think, jdbastro says Cnoct may have a better idea with a PVS-7, but I don't see how it could get much better than that last picture. Thanks VDN.