Lunt 60 / binoviewing. And cold weather, and tube currents.

[Tony G]

Just bought a lunt 60 b600. What binoviwers, and eyepieces are a good combo? Today was my 3rd time out with no success so far but after a 3.5 to 4 hour equilibrium due to it being 20 degrees out side the full disk finally come on band. I was stressin pretty hard for a while as one whole side was washed out. I thought cold and tube currents was the issue as I could tell by the edge of the eyepiece had a rolling boiling thing going on, but wasn't sure how critical. 3.5 hours it took! Just throwing that out there for someone else's first experiences. Im already ready for a double stack too. I'm so glad It come onband almost to the edge. I've read of sweet spots even in pt models and was afraid that's what I had. My favorite view was with a 25mm eyepiece. Small full disk I could take it all in at once with a really consistent view.

[alanjgreen]

Hi tony,

i use baader markv binoviewers with my Lunt 60. I need a 1.7x glass path corrector (bit like a Barlow) fitted to the bino for the scope to be able to reach focus.

In the binos I then use pairs of 24mm and 19mm eyepieces (remember that the 1.7x gpc turns these into effective 15mm and 12mm)

There is a picture of my setup on page3 of the thread "show us your solar observing kit". I will paste a link ...

Cheaper binos will be fine but you will need a glass path corrector or Barlow to reach focus for sure.

You can also try your existing eyepieces with one eye in the binos to find the view you prefer BEFORE you splash out on the 2nd eyepiece to make a pair!

Alan

[alanjgreen]

6 hours ago, Tony G said:

. I was stressin pretty hard for a while as one whole side was washed out. I thought cold and tube currents was the issue as I could tell by the edge of the eyepiece had a rolling boiling thing going on, but wasn't sure how critical.

Tony,

it sounds to me like you are using too much magnification. I find x30 to x45 is the best range for a sharp clear view. What eyepiece size were you using?

The lunt60 has a sweet spot as you mention, it is a large sweet spot but nevertheless it is a sweetspot!

Next time out, start with a 14 or 15 mm eyepiece, the sun will be smaller and will fit into the sweet spot. It will be easy to get a sharp focus at this magnification. Get a feel for the view, are the problems you describe above gone?

Then try a 12mm (the best power for the lunt60) in my view. Again, most or all of the sun will be in the sweet spot.

if you go below 12mm then you will not get the whole sun in the sweet spot and you will have to accept that the bit you are not interested in will look worse than the bit you have in the sweet spot.

the edge broiling you describe is happening because the sun is low in the winter sky and the earths atmosphere is thick down there. It will not be there on days where the conditions are better or as the sun rises higher in the sky as the year progresses...

if you do double stack then the sweet spot will be smaller still. But within that spot you will get much more detail if you double stack the full 60mm. Double stack 50mm does not give as good a view as double stack 60mm and you should do some research to avoid disappointment.

Hope this helps,

Alan

[Floater]

1 hour ago, alanjgreen said:

Cheaper binos will be fine but you will need a glass path corrector or Barlow to reach focus for sure.

Be careful with that: I tried a 'cheap' Revelation binoviewer and it simply would not reach focus. Checked with suppliers (Telescope House) and they agreed that I had tried everything possible - including TV 2.5 Powermate - and that I should just return the binoviewer for refund.

[alanjgreen]

18 minutes ago, Floater said:

Be careful with that: I tried a 'cheap' Reveleation binoviewer and it simply would not reach focus. Checked with suppliers (Telescope House) and they agreed that I had tried everything possible - including TV 2.5 Powermate - and that I should just return the binoviewer for refund.

Tony,

therefore, post which binos you are thinking of buying before you buy them to confirm that someone's successfully using them with a lunt60 and then you can discover which gpc or Barlow you will need as well.

the revelation must have a long light path. The advantage of the baader maxbrights or markv is that you can use the T2 system to get them attached directly onto the blocking filter saving precious mm of light path. Also notice that my baader focuser is narrower than the default Chinese jobby! You did try pushing the blocking filter draw tube all the way into the focuser I assume? Mine is all the way in when I use my binos.

Alan

[Tony G]

Yes! Thanks everyone. I've always wanted binoviewers. Never looked through any!!  I found 25mm was my favorite view. 15mm was better detail in plague areas and onband full disk. The 25 was just more constantly steady. 

[alanjgreen]

Thats right Tony. Its too easy to use too much magnification on the sun. Its so close to us and so big that it realy does not need it.

Lower magnification takes the atmospheric conditions out of the equation too.

 

[Tony G]

Also meant to ask about the double stack. The image is super bright, How much will a double stack 60 cut back the brightness? I've read people say it's dim, but man it sure is bright with a single. I'd like to dim it down a bit but not sure how really.

[alanjgreen]

7 minutes ago, Tony G said:

Also meant to ask about the double stack. The image is super bright, How much will a double stack 60 cut back the brightness? I've read people say it's dim, but man it sure is bright with a single. I'd like to dim it down a bit but not sure how really.

The 60mm double stack is slightly dimmer, but nothing that you really notice. The prominences on the edge are usually the first thing to go with a dim image and I have no issues with those at all.

There are plenty of posts around from folks who found the 50mm double stack caused a dim image - then you have the faff of keep taking the double stack on and off.

Its usually just a case of "getting your eye in" (give it time to adjust). Usually after a min or so, if you look back around the disk then more stuff is noticeable that you misses the first time. I usually need to loosen the pressure a tiny amount as the initial attempt turns out to be slightly too much.

Your eyes will adjust to the brightness in a few seconds

 

 

[Solar B]

I don't think that your size of BF will lend itself easily to Binoviewing .... it's not impossible but normally a larger BF is required 

to help prevent vignetting ... if the image does appear a little too bright then try putting a filter onto the EP or even onto the nose piece

of the BF (polariser eg) I've done this a number of times with different HA scopes / set ups.

Re a good EP I have normally found the simpler to be the better but try and experiment with as many as you can to decide what suits 

you the best and I personally wouldn't rush into DSing but recommend becoming fully conversant which your scope first .... I can 

however understand that many do wish to DS their units to achieve the greatest detailed surface views but if you must then why not

try buying a used 50mm first or even better try someone' else's DS unit.

Brian 

[Peter Drew]

On my 6" F10 PST mod all I use at the eyepiece end is a 5mm blocking filter, a basic Revelation binoviewer with a basic Skywatcher 2x Barlow front lens unit screwed into the nosepiece. This presents a long effective focal length so eyepiece pairs of 40mm and 32mm are the most used. The Barlow increases the field of view somewhat and the whole field is pretty much on band. OK, I can't see the complete solar disc but that no more bothers me than not being able to see a full lunar disc as it is the high resolution detail that interests me. On a good visibility day the results are outstanding.  

[Moonshane]

I thought I might struggle with BVs with my 100mm PST mod as I use the original PST BF5. However, I was delighted to find that despite not getting full disk with a 15mm plossl (67x), I do get full disk with my 18mm BCOs (94x) and 25mm Plossls (68x) and even more surprisingly my 32mm BCP (52x). I am not quite sure how this works to be honest but the BVs seem to provide a wider field for the BF5. My point I suppose is that if you can try someone else’s BVs you might be surprised.

[Tony G]

On 2/6/2017 at 05:00, Moonshane said:

I thought I might struggle with BVs with my 100mm PST mod as I use the original PST BF5. However, I was delighted to find that despite not getting full disk with a 15mm plossl (67x), I do get full disk with my 18mm BCOs (94x) and 25mm Plossls (68x) and even more surprisingly my 32mm BCP (52x). I am not quite sure how this works to be honest but the BVs seem to provide a wider field for the BF5. My point I suppose is that if you can try someone else’s BVs you might be surprised.