First light with Lunt LS50

[Highburymark]

Coincidentally - after snaxmuppet's post yesterday - I am also going through something of a learning curve with my new Lunt. First of all, it's a couple of weeks since the telescope was delivered, but we've had almost continuous cloud, so have only used it three times - longest clear session no more than ten minutes.

Of all the eyepieces I've tried (plossls, Hyperion 10mm, Televues - so a decent selection), I've only been able to reach focus with a Meade 25mm Plossl and Pentax XF 6.5-19.5mm zoom - the latter providing much the better views. And that focus is only achievable with the focuser stretched to its limit. - as soon as I relax the focuser slightly I lose any crispness.

Then I've also had a similar experience with the pressure tuner. I unscrew it as the manual says (but don't hear any "popping" sound when the handle is released from the brass cylinder) - but I don't see any detail or features until the tuner is fully screwed in - at this point I have seen sunspots and a couple of small prominences which was great - but it was only when there was literally no thread left on the cylinder.

To try and improve the focusing, I did what snaxmuppet did yesterday, and pulled the diagonal out from the focuser a bit, but that made it worse - I could get no focus at all with the Pentax. I guess this trick doesn't work with the LS50 - as it's not suggested in the manual (whereas the LS60 manual does suggest it). There was also a post about the Lunt 50 from jabeoo on SGL last winter which said "the attached T-thread adapter needs to be placed between focuser and diagonal - this means back focus is achieved without the focuser being fully extended" - which I also tried, but obviously this had the same effect as moving the diagonal away from the focuser - so didn't work for me.

The fact that I've experienced one really good view (though I'm sure the scope is able to produce much more detail) makes me think that the problem is not with the telescope, but with the dimwit operating it. Plus there's the constant cloud, which means I have yet to enjoy a relaxed viewing session. But any advice would be gratefully appreciated.

[Hyperion76]

ok you should be able to achieve focus with the usual eyepieces down to 4mm so I am going to ak you whether or not you have tried focusing both ways as I have found that depending on eyepiece types you might be helped by fully rotating the focused in both directions to help you achieve focus ,

have you tried unscrewing the valve until it fully unscrews -remove it then re screw it meaning you have fully equalised the pressure?

You do not need the adaptor to achieve focus.

Is the 45 angle pushed fully into the connector? mine has a tendency to slip could affect focus

[Pig]

Mark,

The best advice with Solar observing is patience and of course the activity at the time of observing.

The best eyepiece I used with solar was the Vixen SLV at around 55 X mag (in my Lunt 60 this was the 9mm) The Leica zoom was also as good but is very expensive.

25mm sounds way to low a power in my opinion and this would have resulted in less satisfying views in the 60mm, considering 50mm isn't much different I am a little lost as to why you are using this low power. Select an eyepiece that will give you around 60 x mag.

I haven't used the helical focuser before but I would be tempted to experiment a little if I was you and simply adjust the helical focuser so it is somewhere in the centre of it range and then pull the diagonal in / out until you nearly achieve focus and then use the focuser to fine tune. 

I am sure the pressure tuner has the same effect as the tilt tune front etalon and has nothing to do with focussing, it simply changes the detail you see.

PM me if you need further advice.

Shaun

[Davey-T]

Don't know about the 50 but focussing on the 60 is easy to go straight past focus point, I should think the helical focuser makes it even harder so need to adjust very slowly

The pressure tuner needs to be screwed pretty much all the way in, something not very clear from the manual, I spent ages screwing mine in a fraction at a time when I first got it 

I don't use anything smaller than 32mm plossl in the 60 so 50 can't be much different.

Dave

[Pig]

32mm wow......... are the 50mm and 60mm that different ? I am stunned  

[Highburymark]

Thanks for all the advice. I will go through your suggestions methodically. But I have tried focusing fully both ways and unscrewed the valve fully. I only tried the 25mm as that was recommended as a starter EP. But all comments and suggestions appreciated.

[Hyperion76]

25mm is lacking in power but a12mm to 9 mm I find is great

[Highburymark]

Have gone up to 40x today with good views - but sharpest images with eyepiece at 15-19mm. Really nice prom and sun spots and more granulation in evidence. I'm having fun, so maybe I shouldn't worry about turning the focused and pressure tuner to extremes.

[Pig]

Its sounds as though progress is being made already  I wish I cold see the sun... completely grey here at the moment Mark but I might get a glimpse later this afternoon.

[Highburymark]

Ok - done more experimenting.

1. Can't get focus at all with Delos 17.3mm, Baader Hyperion 10mm and plossls under 12mm .

2. Can just get focus ( at one extreme of focuser ) with Pentax zoom.

3. Then can just get focus with the Panoptic - but that's at the other extreme of the focuser.

4, Then (joyously) the 12/15/20mm Meade plossls reach focus somewhere in the middle.

So my experience so far is that the cheapest EPs are much the easiest to use with this telescope - unless there's something wrong with the focuser?

I'm also coming to the conclusion that the pressure tuner may not be performing to its potential - have to tighten it as hard as possible before I get defined features, but even then not getting the results that some are describing on this site. Wondering whether it's a lack of grease on the piston/thread system - it doesn't seem to have any discernible grease, though it screws relatively smoothly.

Hmm........

[Lowjiber]

I have a Lunt 50 B/600.

Regarding the helical focuser...

It is a very poorly designed focuser. It will "hang up" to the point that you think you're at the end of its travel... but you're not. You should be able to achieve a range of about 15.5 Major tick-marks (10 + 5.5). While it gets better with use, it's a real problem when you first start using it.

Another way to tell if you've reached maximum range... when the focuser is at its max, there is a tiny phillips screw visible on the shaft next to the adjustment ring. If you don't see that screw, you need to continue cranking it out. (BTW: make sure that screw is tight.)

Regarding eyepieces. I regularly use my ES 82 deg 8.8mm with success.

Hope that helps.

[Highburymark]

I have a Lunt 50 B/600.Regarding the helical focuser...It is a very poorly designed focuser. It will "hang up" to the point that you think you're at the end of its travel... but you're not. You should be able to achieve a range of about 15.5 Major tick-marks (10 + 5.5). While it gets better with use, it's a real problem when you first start using it.Another way to tell if you've reached maximum range... when the focuser is at its max, there is a tiny phillips screw visible on the shaft next to the adjustment ring. If you don't see that screw, you need to continue cranking it out. (BTW: make sure that screw is tight.)Regarding eyepieces. I regularly use my ES 82 deg 8.8mm with success.Hope that helps.

Really appreciate the advice Lowjiber - thanks

[Highburymark]

I have a Lunt 50 B/600.Regarding the helical focuser...It is a very poorly designed focuser. It will "hang up" to the point that you think you're at the end of its travel... but you're not. You should be able to achieve a range of about 15.5 Major tick-marks (10 + 5.5). While it gets better with use, it's a real problem when you first start using it.Another way to tell if you've reached maximum range... when the focuser is at its max, there is a tiny phillips screw visible on the shaft next to the adjustment ring. If you don't see that screw, you need to continue cranking it out. (BTW: make sure that screw is tight.)Regarding eyepieces. I regularly use my ES 82 deg 8.8mm with success.Hope that helps.

Actually I'm getting a range of 17.5 major marks on the focuser! 2 more than you say, and the small screw is exposed as you describe. The focuser also operates very smoothly, no drag or stiffness. The only problem I have is that my favourite eyepiece - the Pentax zoom - only just reaches focus at the extreme - and I'm sure that a few more mms would sharpen it up more. Thanks anyway - good to learn a bit more about the experience of other Lunt 50 owners.

[Lowjiber]

I'm glad, but jealous, that you're getting 17.5 major tick marks.

Another thing that may help in the future... If you ever buy a ZWO ASI120 camera for it, you won't be able to get adequate focus.  I won't bore you now, but send me a PM and I'll tell you how.

Clear Skies

[Owmuchonomy]

Ok - done more experimenting.

1. Can't get focus at all with Delos 17.3mm, Baader Hyperion 10mm and plossls under 12mm .

2. Can just get focus ( at one extreme of focuser ) with Pentax zoom.

3. Then can just get focus with the Panoptic - but that's at the other extreme of the focuser.

4, Then (joyously) the 12/15/20mm Meade plossls reach focus somewhere in the middle.

So my experience so far is that the cheapest EPs are much the easiest to use with this telescope - unless there's something wrong with the focuser?

I'm also coming to the conclusion that the pressure tuner may not be performing to its potential - have to tighten it as hard as possible before I get defined features, but even then not getting the results that some are describing on this site. Wondering whether it's a lack of grease on the piston/thread system - it doesn't seem to have any discernible grease, though it screws relatively smoothly.

Hmm........

Interesting thread.  My Lunt 50 600B suffers badly from poor in-focus (not back focus).  It works great with my 8 and 10mm Baader Hyperion and 15, 25 and 40mm Celestron plossls.  it does not work with a Baader Hyperion zoom neither does it function with any of my 2" EPs using the Lunt 2" adaptor.  Fortunately FLO gave me a full refund on the adaptor.  What do you and Lowjiber mean by tick marks?  Mine does not possess such luxuries.  Lowjiber is correct and the helical focusser is a real weak spot with this scope.

[Davey-T]

Time to bin the focuser and get a Moonlight 

Dave

[Owmuchonomy]

Time to bin the focuser and get a Moonlight 

Dave

oooh, do share!

[Highburymark]

Interesting thread.  My Lunt 50 600B suffers badly from poor in-focus (not back focus).  It works great with my 8 and 10mm Baader Hyperion and 15, 25 and 40mm Celestron plossls.  it does not work with a Baader Hyperion zoom neither does it function with any of my 2" EPs using the Lunt 2" adaptor.  Fortunately FLO gave me a full refund on the adaptor.  What do you and Lowjiber mean by tick marks?  Mine does not possess such luxuries.  Lowjiber is correct and the helical focusser is a real weak spot with this scope.

Chris,

Some LS50s (I think mainly the earlier batches, of which yours may be one) came with focusers that had no markings. The newer examples have a scale going from 0-14 - that's what we meant by tick marks. Interesting that you get your fixed length Hyperions to focus - I cant.. If you want some advice on using the Hyperion zoom with the LS50, there is a thread on cloudy nights about how to fix it. The annoying thing for me is that most focus issues with the Lunt helical can be sorted by pulling the diagonal out from the focuser by a cm or so. (the Lunt manual for the LS 60 actually advises this) - or by adding an adapter between them, but what I need is the opposite - less distance - to focus my zoom. I'm wondering if I can get a shallower eyepiece holder to replace the stock one, as this might give me a better solution.....or I might just follow Dave's advice.....

[jabeoo1]

Hi Highburymark, 

I found that some eyepieces did not focus when the diagonal tube was fully inserted & flush to the focuser.  In some cases the tube needed an extra 2 or 3mm back focus so I took out the diagonal, added the T-thread adaptor to the focuser which gave that extra 2 or 3mm back spacing and allowed the diagonal back in flush and square to the T adaptor.  This was the alternative to having the diagonal tube visible whilst deliberately not fully inserted to create that extra back focus, to me the T adaptor was a more study option.

I use 25mm, 20mm, 15mm, 11mm & 8mm EP's in mine.  I found Delos EP's did not work visually anywhere near as well as a straight forward plossl, and the sweet spot seemed more diluted on the larger glass surface.

I find the sweet spot on mine just below dead middle.  Personally I love the view with the 25mm & 20mm as the smaller scale gives high contrast fuller disc views & they remain more stable in most seeing conditions.  The 15mm is remarkable and remains the best for me overall when balancing full disc features, contrast, magnification with average seeing.  The 11mm can eek out those extra features within features in a diluted kind of way during normal conditions, when exceptional seeing allows and all is calm there are rare glimpses that can etch a grin from ear to ear.   However I do not find the UK weather allows this quality viewing very much hence the 8mm does not spend much time in the scope.

The pressure tuner on mine comes into its own with some visible thread to spare.  Has the pressure tuner got enough of what looks like thick vaseline lubricant on it?  

The rubber bung if too dry might not be performing optimally causing you to need the extra turns to the top of the thread.  By the way check what the substance actually is first before smothering the tuner with anything !!!!!!!!

As for the focuser ...well yeah it is okay, its adequate & does the job quite well, but its not luxuary or fine tuned.  I have spoken to Ron @ Moonlite about this.  He has said he can make a nice dual speed focuser for the Lunt 50, (I think I was the 3rd person to enquire).  As far as I know no one has gone ahead yet & to do it he needs the stock focuser sent to him so he can design the Moonlite one.  If no one has gone ahead and sent theirs to be measured up soon, I am going to send mine over to get it sorted.  I assume once the plans are on their database anyone will be able to order one without going through the same process of posting their focuser to the USA. 

I have just emailed Ron again.  I will post anything relevant.  

[Highburymark]

Thanks for posting jabeoo - really interesting and useful comments. Totally agree with you about the excellent performance of the mid-range plossls (presume the 15mm you refer to is a Plossl?). I may end up using them exclusively with this scope if I can't find a way to focus the Pentax fully. Or maybe replace it with the Lunt zoom.

I also agree with you about the sweet spot. Although I haven't had extended sessions with the scope yet, the best prom detail for me has been pretty much dead centre.

As far as the tuner's concerned, there is almost no visible grease on it, or the o-rings, so I'm definitely going to get the correct stuff and re-apply it.

Interesting what you say about moonlite. Am sure there will be others - me included - who might help swell the order book for a replacement focuser. One issue for me would be weight. I'm trying to construct a lightweight mounting option for solar viewing - but ultimately getting a telescope that's working to its full potential is the most important thing.

One other thing I'd say is that despite these early issues with the telescope, I absolutely love it, and do not regret the purchase at all. Just want to make sure that full potential is achieved.

Thanks again for the reply.

[jabeoo1]

Totally agree with you about the excellent performance of the mid-range plossls (presume the 15mm you refer to is a Plossl?). 

Yes the 15mm is a plossl (TV). 

Interesting what you say about moonlite. Am sure there will be others - me included - who might help swell the order book for a replacement focuser. 

I am currently trying to see if I can get the ball rolling with it.  Another thread has FLO chipping in saying its cheaper to go via them to get focusers added to their bulk order.  So I am going to try and tempt them to send a few in one go  

As far as the tuner's concerned, there is almost no visible grease on it, or the o-rings, so I'm definitely going to get the correct stuff and re-apply it.

I will try and post an image of mine to give you an idea of the kind of coating they need.  Its quite thin & extensive, it also overlaps onto the threads too. In the meanwhile do ask Lunt what this gunk is !  I am sure more will need applying with age and use. 

[Pete Presland]

Interesting discussion makes me a little nervous about getting a lunt 50 to be honest

[Highburymark]

I will try and post an image of mine to give you an idea of the kind of coating they need.  Its quite thin & extensive, it also overlaps onto the threads too. In the meanwhile do ask Lunt what this gunk is !  I am sure more will need applying with age and use.

Thanks - that would be really useful. I've tracked down the gunk brand so hope that's going to make a difference.

[Owmuchonomy]

My situation is different. I have insufficient in-focus. Pulling the diagonal out just makes it worse. I need a couple of mm shaving off the setup. My LS50 is only a few months old from FLO. Maybe that's why my Baaders work save for the zoom.

[Pete Presland]

Are there any issues with focus regarding the imaging source cameras as well?

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