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Lunt 60 DS -> Lunt 100 DS

Posted: Fri Jan 05, 2018 1:34 pm
by Robson87
Hello, I write because I'm considering an upgrade from my Lunt 60 double stacked with a Solarmax 60 type front etalon, to a Lunt 100 DSII which I could have at a good price.

I know that the views (I'll do 95% visual) in the Lunt 100 DSII will be better, but I don't know if they are so better to worth the extra money (the double of the Lunt 60 DS once sold).

The contrast in the Lunt 60 DS is superb and the sky behind is black, will I regret it with the DSII of the Lunt 100? I've read some serious ghosting problems about it, and others who say that the improvment between 100 SS and 100 DS is not so impressive as that one between 60 SS and 60 DS.

Another problem is that I would mount the Lunt 100 on a Nexstar Evolution, I think it will support the Lunt 100 but never heard any report about this possible setup.

Thank you in advance for any advice ;)

Re: Lunt 60 DS -> Lunt 100 DS

Posted: Fri Jan 05, 2018 5:22 pm
by Bob Yoesle
Compared to the 60, your resolution of detail with the 100 mm DSII is likely to mitigate any decreased contrast by using the DSII. If problematic, you can suppress the DSII ghosts with a B+W Kaesemann circular polarizing filter, at the expense of image brightness. You can also eventually double stack using the front mounted LS100F, which should work as well as your Lunt 60 with the SM60.

Re: Lunt 60 DS -> Lunt 100 DS

Posted: Sat Jan 06, 2018 12:35 am
by Robson87
Point is that the DSII unit should increase the contrast instead of decreasing it. But I don't know how much it will increase the contrast in comparison to the 60 DS (which already has a contrast that I really love).
I don't even know how much ghost there will be (but I can go and try it, even if the scope it's not close to me at all), and I have no idea of how much an eventual polarizing filter will further reduce the brightness. Because otherwise, if it doesn't worth it, I save money and I continue enjoying the 60.

Re: Lunt 60 DS -> Lunt 100 DS

Posted: Sun Jan 07, 2018 1:50 am
by GUS
I have a doublestacked LS60 with the 60mm front etalon, and also an LS100 with the DSII etalon. I love the view through the double stacked LS60, great contrast and black background.I also love the view through my single stacked LS100. I can't say the same about the DSII, the glow is annoying and detracts from the view. I do use a circular polarizer and the glow is completely suppressed, but the image is significantly dimmer. I have a range of blocking filters that vary in light throughput, and use the one that gives a brighter image and this works quite well. For what it cost, I think I would have been better off buying a Coronado 90mm front DS unit. As a side note, I can also use the DS 60mm etalon on my LS100 scope(with an adaptor), gives a great contrasted view with black background but you are then limited to 60mm aperture.

Re: Lunt 60 DS -> Lunt 100 DS

Posted: Sun Jan 07, 2018 4:01 pm
by Robson87
Thank you very very much GUS, actually I'm really undecided.
I know that 100mm will provide much more resolution, but I seriously love the contrast of the 60 DS.

The problem is that I can't keep both telescopes due to money, so I have to decide.

An idea could be taking the 100 SS and mounting for the moment te 60 DS unit on it, waiting for a future 90 DS unit.
The SS views will be better for sure; I don't know if the image quality will be the same between the 60/60 and the 100/60 in DS mode, but I imagine yes.

The other problem is that on CN I've read some users who claim that they tend to prefer SS views on 100mm, rather then DS with front unit of 100mm. It's sounds strange to me, on 60mm the difference between SS and DS is so obvious in favour of DS...

Re: Lunt 60 DS -> Lunt 100 DS

Posted: Mon Jan 08, 2018 11:49 am
by GUS
I'm not sure why, probably due to the longer focal length, but the 60DS filter produces a slightly better view at an equivalent magnification when mounted on the LS100 compared to the LS60 scope. I also had a Coronado richview 60DS filter which I used with both my scopes and that worked as good as the Lunt DS unit.
If you want an idea of what the ghosting on the DSII unit is like, just tilt the ghost image fully on your Coronado DS unit until it covers 3/4 of the sun, that's very close to the amount of glow you see. The LS100 SS has a very bright image, which allows high magnifications, and on good seeing days above 200x is possible, and proms and spicules at higher magnification show a fair amount of intricate details.
I know it's been stated on this forum and others that there is no difference to the amount of detail visible on proms in SS or DS, but in practice, especially with the LS100 SS, the proms just look better.
Regards to your decision on what to do, I can only say that in the last year with dwindling surface detail, and the sporadic appearance of proms, I've been mainly using the LS100 in SS mode, and occasionally( if there is a filament or small AR), the DSII or the 60DS units. The LS60PT only gets used if I want a quick look, or take it with me on holidays.

Re: Lunt 60 DS -> Lunt 100 DS

Posted: Mon Jan 08, 2018 12:46 pm
by Robson87
Thank you again GUS.

I have I think the last question:

How does the 60 DS performs in comparison (brightness, resolution and contrast) to the 100 DSII + circular polarizer?

Because apparently, if the polarizer suppresses the glow, the image should remain with black background, with the resolution of 100mm instead of 60mm, with the contrast of a double stack system, and with a brightness which may be lowered by a circular polarizer (but also the 60 DS has 2 ERF filters, one of which becomes not useful and reduces the light) but in front has the light of a 100mm instead of 60mm.

I definitely should try my 60 DS next to the 100 DSII...