Binovue refractor setup recommendations
Posted 14 September 2019 - 03:24 PM
1) buy a 2” diagonal w/ high hat 1.25” adapter and use the binovue with the 2x amplifier. This seems like the simplest solution (and cheapest), but of course I would be stuck at higher powers (which I do most my observing at anyway, but might be nice to have close to native focal length every now and then) and seems a bit overkill weight wise, since I currently don’t own any 2” eyepieces. Haven’t since I went down the bino road.
2) get a Baader t2 diagonal (thinking the bbhs mirror version), 1.25x glasspath, and thread the binovue directly into the diagonal. Would allow for more mags if I also got the 1.7x, and would be lighter weight.
Thinking I’m leaning towards option 2, but does anyone have experience with this setup, or any issues I should be aware of? Still a bit unclear on how the glass paths connect, do they just “sit” under the t2 thread like a thin washer, or do they screw in somehow? Do I need anything like the quick change adapter to make this work?
Thanks in advance for any insight, I know binoviewers can be a bit fiddly, and hopefully can learn from others experience with what setup works best.
Posted 14 September 2019 - 07:08 PM
For your application, the GPC would sit inside the top of the diagonal and the T2 coupler on the Bino Vue would then screw over the top. The GPC for the Mark V and for the Maxbright is the same housing, but the lenses are removed and filipped based on the BV. For you, the GPC would be turned the same as for the Maxbright (there is a little decal on the side that tells which direction the lens is supposed to face).
As for will it will work, I suggest that you download the Maxbright Owner's Manual. Be aware though that the Maxbright as a 110mm light path, and you would need to add about 20mm to these figures for the Televue because I think the light path is more like 130mm for that unit.
The 1.7x GPC only gives about 1.5x or so but it only buys you about 34mm of inward travel. The mirror has a much longer light path than the T2 prism so that needs to be factored in as well. I do not have experience with your scope, but my guess is that the BBHS is going to be to much light path for the TSA 120 but I don't know how much back focus you have to work with.
The BV has about 130mm, and the BBHS diagonal will have about 75mm of light path so a total of 205mm, The 1.7x GPC is going to take only 34mm from that, so you would still have 171mm of light path, and that is more than the back focus of must telescopes.
Now if you use the Baader T2 standard diagonal, the light path is only about 40mm, so total will be about 170mm, and subtracting 34mm for the 1.7x GPC, you would need 136mm. Since a typical 2" mirror diagonal is about 100mm, if you can reach focus with an eyepiece have have 36mm of focuser travel left, you might make it work. If you don't have this much left, then you are probably going to have to stay with the Televue 2x amplifier.
Posted 14 September 2019 - 07:21 PM
For solar, lunar, planets, you're in good shape. For deep sky viewing , I was underwhelmed simply because of the light loss due to beam splitting, in an already-small aperture.
With the FT focuser , I can do native BV'g with a Baader Amici T2 diagonal directly coupled to the Televue Binovue. When using a refractor for wide field I prefer Amici diagonal for correct image. After a few tries I found that an Ethos eyepiece gives a much better view for deep sky than BV at comparable magnification.
The photo shows the BV with 2x Powermate + Powermate T adapter instead of the 1.25" stock amplifier. Only because my focusers are 2". Does not provide a better or worse view than the stock 2x amplifier. This provides a superlative view of the planets and moon. The TSA 120 is one of the three "perfect" refractors, along with the TEC 140 and AP 130.
Posted 15 September 2019 - 03:58 AM
The TSA120 has 227mm of back focus from the end of the draw tube.
You can get an M72 > T2 adapter and have the diagonal attached directly to that adapter, then use Baader Quick Connect HD on top of the T2 diagonal to attach the BinoVue.....