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ollypenrice

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Posts posted by ollypenrice

    After market focuser for refractors

    in Discussions - Scopes / Whole setups

    Posted · Edited by ollypenrice
    Typo

    10 hours ago, Bukko said:

    And I know you are not anti - Crayford design, as, basically, your favourite mount is just a big version of the same principle !!

    Gordon.

    :icon_mrgreen:

    Steve Richards got me with the same observation a few years ago! :icon_salut:

    At the risk of responding too solemnly to a good joke, the essence of the Mesu is the extremely fastidious manner in which the friction drive is engineered. Above all the choice of materiel for the driving and driven surfaces is critical. The Mesu does not use smooth anodized aluminium on either. You could  suggest to Lucas Mesu that he try it but I'd be inclined to stand well back as you do so!

    This is why Baader have invested so much time in finding the right material for the driven part of the drawtube and why Moonlite should, in my view, do the same. Their product could easily be modified accordingly. Other aspects of their focuser are excellent but there are more than enough posts in this thread to confirm that it can lack the grip needed for heavy-camera imaging and even, it seems, for supporting heavy eyepieces. I think mine would support heavy EPs but, so far, we've only tried it with a camera in a motorized focus application where it failed due to slippage.

    Olly

    After market focuser for refractors

    in Discussions - Scopes / Whole setups

    Posted

    1 minute ago, GavStar said:

    Olly

    I have wondered how the locking screw on my feathertouch focuser work. Is it really as simple as a screw with a nylon tip or does starlight use a different approach?

    Gavin

    I don't know but it looks like a soft tipped pressure screw on mine (pressing down from the opposite side to the R and P mechanism.) I tend to give it a slight tweak after each focus iteration before looking at the FWHM since it always affects the value if I focus first and then tighten.

    Crayfords seem to have an assortment of ways of making the lock screw press on something - and not always the same thing.

    Olly

    • Like 1

    After market focuser for refractors

    in Discussions - Scopes / Whole setups

    Posted · Edited by ollypenrice

    To take the conversation in a different direction, I often wonder why focus locks are designed as they usually are - which is to use a screw pressing on the draw tube. To avoid their damaging the drawtube they usually have nylon tips which are, of course, not very effective at holding the drawtube in place. They also push the drawtube from one side which is not good for the friction in a Crayford design or the mesh in an R and P. Nor is it good for the drawtube bearings since it enourages play over time.

    An alternative method would be to have a flat strip of low-expansion material attached to the rear of the drawtube and passing through a small clamp at the rear of the main tube. Either the entire focuser including clamp could rotate (the 'Captain's wheel' design) or a rotator could be added at the rear of the draw tube. No pressure would be applied to the draw tube and the strip-and-clamp would be doing what they were designed to do, which is be clamped. The conventional system has a drawtube being asked to do the opposite of what it was designed to do, which is move freely. A scribble:

    5964d2b043e88_focuslock.thumb.jpg.2caea1b5eb639b7045222c8b3c67f514.jpg

     

    So what we're trying to do here is uncouple the holding still of the drawtube from the quite different problem of driving it smoothly while retaining sufficient tension for it not to slip until fixed.

    Olly

    PS I suspect, but don't know, that such a clamp would have less effect on fine focus than the present methods. As all imagers know, locking the draw tube does affect critical focus.

    PPS Oops, no good for remote operation! :crybaby2:

     

    • Like 3

    After market focuser for refractors

    in Discussions - Scopes / Whole setups

    Posted · Edited by ollypenrice
    BTW

    9 hours ago, FLO said:

    It is okay for someone to own and like one :smile: 

    Steve

    Putting words in my mouth by implication? I wouldn't dream of denying anyone the right to own and like them. I own one and would  like it for visual use. I'd like it even more with a strip of grippier material for the spindle to drive and I wouldn't be in the least surprised to see this introduced. Note that Baader are now on their second generation of 'grippy strips' which suggests that there are engineers out there (and Baader are certainly engineers) who see it as a key issue.

    BTW, as I said at the outset I think that the Moonlite design has it over the competition in terms of the effectively self-orientating drawtube/spindle. Many of the solutions to this problem are vastly over-complicated and difficult to adjust.

    Olly

    • Like 2

    After market focuser for refractors

    in Discussions - Scopes / Whole setups

    Posted

    5 hours ago, FLO said:

    I didn't realise you were still running your anti-Crayford campaign :smile: 

    We offer all the brands discussed in this thread so are as neutral and objective as any retailer can be. I do understand why, Olly, in your circumstances a Starlight Instruments FeatherTouch R&P focuser is the right choice. It is beautifully engineered and bomb-proof but it's price (around £600) puts it out of reach for most astronomers. Fortunately, for most applications, it isn't necessary. 

    I like the Crayford design because it can be made to a high standard at an affordable price (it isn't possible to make a good R&P focuser at the prices most Crayfords sell at). And, when done properly, a Crayford is a delight to use and is more than enough focuser for most astronomers. Even Starlight Instruments acknowledge this - their more affordable focusers (around £400) are Crayfords. 

    HTH, 

    Steve 

    I thought I was being rather balanced here! I have made a clear distinction between good and bad Crayford practice, 'bad' being driving a smooth anodized drawtube directly with a steel roller. It just is bad, in my book. I think my Moonlite is poor for this very reason. (Poor for imaging. It would make a nice visual focuser on a Dob. Very smooth.)

    Olly

    After market focuser for refractors

    in Discussions - Scopes / Whole setups

    Posted

    On 07/07/2017 at 22:51, AlistairW said:

    I have a question. If you attach an electronic focuser such as a Lakeside to the Moonlite, shouldn't the Lakeside hold it (the focuser) in position, by the nature of the motor drive. Would this not then eliviate the slippage ? - (if you use Bhatinov only and manual focus - this obviously still would have the potential to slip I guess?)

    Sadly not. The electronic focuser holds the focus knob reliably but the Crayfoprd design relies on friction between the focuser shaft and the draw tube to hold the payload. That is why Baader insist on the nature of the driven surfaces in their naming. There's the Steeltrack which has an unpolished steel driven strip and the diamant which has a grippier industrial diamond driven strip.

    Having the steel shaft drive a slippery anodized aluminium drawtube is just not good practice. Sure, they often work - but they sometimes don't. Why not just get it right first time? If an imager's robo focus works by counting motor steps it needs to know that a step is a step and not a slip.

    Olly

     

    • Like 1

    Meade LX200 14 inch GPS

    in Member Equipment Reviews

    Posted

    12 hours ago, michael8554 said:

    Regarding the noise when slewing, it's recommended for Classic and GPS LX200's to set the max slew rate in the menus to a lower figure - less noisy, and reduces wear on the gearing.

    GoTo's to planets are inaccurate because their ephemeris is so much more complex than for "stationary" stars- never use a planet as an alignment object.

    To hit DSO's smack on every time, use the Synch function after centreing on a nearby known star, then GoTo the DSO.

    Michael

    Good idea on slew speeds. I'll do that. I don't have to worry about the noise but wear on the gears is best avoided. Thanks.

    We found no need to re-synch during our first night out but, yes, it's an option. To everyone's surprise the GoTo was bang on all over the sky. Given a simple two star alignment we found this remarkable. I guess the mount's measurement of its own tilt plays a large part in its success. Pity we can't do GEM polar alignment this way!

    Olly

    Meade LX200 14 inch GPS

    in Member Equipment Reviews

    Posted

    2 hours ago, steppenwolf said:

    OK, I appreciate that it was perhaps a little over the top but somehow or other, I ended up hand-delivering the extension cable to Olly at Les Granges – after all, I did need to know that it had worked correctly ...........

    This was my first visit to Les Granges and I have to say that Janie and I really enjoyed ourselves and I can confirm Olly and Monique’s legendary reputation for hospitality. Our room was tidy, comfortable, stacked with interesting books (although perhaps a little heavy on cycling tomes!) and our bedroom window overlooked the most magnificent views over the staggeringly beautiful mountain countryside in which Olly’s rustic home resides.

    A guided tour of this astronomy oasis proved why Les Granges is so popular with astronomers as there is a wide range of instruments available for visitors ranging from a 20” Dobsonian to Olly’s weapon of choice – his dual Takahashi FSQ 106 equipped wide-field photon-grabber mounted on the Mesu 200 mount that first brought this device to my notice some years ago. Of course, Olly’s version of the mount is powered by steam rather than the ultra sophisticated electronics that my own Mesu mount uses but then – and this is the point - Olly sits up all night with his guests showing them the night sky and how to use the equipment to its best, whereas these days, I just go to bed and let the computer do all the work!

    On the subject of the night sky, despite an unhelpful Lunar phase, the skies above Les Granges were without doubt wonderful and the ribbon of the Milky Way, so clearly visible overhead, was testimony to the lack of light pollution and the crispness of the atmosphere – we are talking ‘Alpine’ here!

    And, now that Olly has the correct lead for the Meade 14” SCT (yes, it did work - phew!), you can even use this recently acquired instrument and focus it minutely for observing, although quite why you would want to observe when you could be imaging on that dual Tak rig is quite beyond me .........

    Of course, you don’t have to use Olly’s gear, you can bring your own equipment and mount it on one of the two conveniently placed concrete plinths set aside for just this purpose.

    Is there anything I didn’t like? YES there was one thing – Olly should be more generous with his skies, I want those skies here in the UK and I want them NOW ........

    Of course, it isn't all about astronomy - even Les Granges has to accept daytime hours - and the surrounding countryside is breath-taking with cycling, climbing, parascending and simply driving around soaking up the views of wild rivers, high mountains and deep gorges to be enjoyed as well. Our visit to the Gorges de la Méouge will remain with us forever.

    I am really looking forward to my next ‘excuse’ to visit. Errrrr, ummmm, are there any other technical issues I can help you with, Olly?

     

    Awe, you're most kind Steve. I was expecting it to be a great pleasure to meet you and Jane and, of course, it was. In spades. My robotic client was also delighted that you could fix his autofocus. I guess I had the wrong steam pressure going...

    I'll post a bit more on the Meade 14 inch once its brass plaque arrives (naming it for Alan and currently in the post). Your cable will need honorable photographic mention as well. And there will also be, thanks to Jane, the floral connection between the Chanconbury Observatory and Les Granges.... I just need to find a competent daytime photographer for all this.

    Sincere thanks for giving us a great couple of days.

    Olly and Monique.

    • Like 4

    After market focuser for refractors

    in Discussions - Scopes / Whole setups

    Posted

    How frank should I be? Very? Then the Moonlite is a joke, albeit a pretty joke. It has one nice design feature, which is that there is no need to align the drive shaft to the drawtube. It is the interaction between the two which defines the rotational angle of the drawtube. This is good. What is dismal is that the roller drives the smooth anodized surface of the drawtube. This is fine on a Dob, where the focuser is always horizontal and carries no weight. It may also be OK on Cats and refractors for visual when it only has to resist the pull of an eyepiece. But hang a camera on it and it is soooo likely to slip. Sorry, it doesn't make the grade.

    We did heavy camera CCD imaging with a Baader Steeltrack without difficulty here for two years but one of our robotic Baader Steeltracks cracked a ballbearing.

    Feathertouch rack and pinion? That would be my choice. I have all three so have no axe to grind.

    Olly

    • Like 3

    Meade LX200 microfocuser cable collision.

    in Discussions - Scopes / Whole setups

    Posted

    1 hour ago, r3i said:

    We discussed this in your other thread on your LX200 and as I said there, if you googled for images of the focuser it becomes clear that the jack on yours is definitely not the original.

    It doesn't surprise me that the jack may have been changed.  I used to have an LX90 and added the 1209 focuser (the one you have) as an accessory, but before that I had the 1206 motor focuser which wrapped around normal focusing knob.  The jack on the 1206 became faulty and I had to cut it off and replace it. 
     

    You may well be right. It's a shame that the alternative socket on the fork tine doesn't work. That would have been a good solution but Steve Richards is coming to my rescue, bless him.

    Olly

    • Like 1

    Meade LX200 14 inch GPS

    in Member Equipment Reviews

    Posted · Edited by ollypenrice

     

    42 minutes ago, steppenwolf said:

    Olly, I could make you up a small extension cable with a lower profile right angle plug and an in-line socket. What diameter is the plug shaft? I suspect that it is 3.5mm?

    It is three contacts, sorry.  It's 3.5mm in diameter and 14mm deep. If you could it would be fantastic, Steve, but only if you've time.

    Olly

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