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CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.
Gary Wolanski's Fine Focus Adapter
Gary Wolanski's Fine Focus Adapter
Tom Trusock (email@example.com)
Last April, I was intrigued by the comments of friends who have fine focus or dual speed focusers on their scopes, and I began to wonder, what (if anything) I was missing by not having this capability on my refractors (Tv-102 and Pronto). There are several options for replacing a focuser out there, and there are some wonderful units made by the folks at Burgess and JMI. I didn't really want to lay out that much money for something I wasn't sure I really needed, and I have always been pretty happy with the stock TeleVue focuser so I looked around for a different (cheaper) solution.
Gary Wolanski provided it in the shape of his Fine Focus Adapter (FFA).
Available for $90 US, ($135 Can) and an additional $15 US shipping. As of this writing, these are only available from Gary, and the only type of payment that he accepts is Postal Money Orders (if you are from outside Canada, he requires a US International Money Order).
For those of you who don't know what this is it is a 2" to 1/25" adapter with a helical fine focus capability. It is quite well made. The only improvement that I could initially suggest for it was the addition of a compression ring. I did think of another feature that I would appreciate. It would be nice if it were threaded for filters. Additionally, the black trim paint is not quite as solid as I would have hoped - somehow, and I am not sure how, I managed to chip or s****e it. (I found this curious simply because I always baby my astro stuff.) All of these are minor items though, and do not detract from it's main purpose - To add fine focusing capability. There is a tension adjustment on the FFA, but I felt that Gary's preset tension was just about perfect.
It is very simple to use. Once you have gotten a rough focus using your standard focuser, you can simply twist the adapter (or the eyepiece) to do the fine focusing. It did it's job VERY well, and if you are looking to add fine focusing capability to your scope, this is an excellent, and relatively low cost product.
As to it's design, the alternative way to accomplish fine focusing is through replacing your focuser as previously mentioned with a Burgess or JMI adapter. WIth the other designs, typically one knob is used for regular focus and the other is used for fine focus. Personally, I prefer the FFA approach. Mainly because I am so right handed, the only thing my left hand is used for is balance. This way I can use my right hand for both standard and fine focus. This of course is a personal preference, and many may prefer the simplicity of having fine focus ability built into the scope. The other advantage to the Wolanski adapter is that it is easily transferable between scopes.
The simple question is "Do I really need it?" The answer unfortunately is not as simple.
I have had the adapter for some time now (several months), and have used it many times.
Here are my initial notes from the first sessions with the Pronto and the TV-102.
Notes from the First Evening - The TV-102
With the TV102 (@ f8.6) the scope has a definite "snap" into focus. Also remember that a longer fl scope has a greater depth of field, and "exact" positioning of the focuser is not as critical. To be honest I was not sure that I needed this product going into it. I have never had much difficulty focusing, however spurred on by some friends who have this capability, again, I did want to see what (if anything) I was missing.
The target was the moon. Seeing was probably around a 5 (on a scale from 1-10). There were multiple instances of "hard" seeing where the view jumps around through the scope but remains fairly sharp, in addition seeing went in and out for most of the night - sharp one minute, blurry the next. Because seeing was NOT the best, I limited my self to a maximum magnification of 220x. I used 3 main eyepieces, a 13mm nager, 7mm nager and 4mm radian. There was no benefit whatsoever to the FFA with the 13mm. There really wasn't much with the 7mm (125x) either, although it was a nice way to check focus, but each time I did, I found I was already at exact focus using the standard focuser. With the 4mm there was some benefit at times.
Often due to the nature of the seeing though, I found I was messing with focus when I really shouldn't have been. In this respect, the adapter "almost" did as much harm as good. I suspect that this may be something I will get used to as I use the adapter more. (I did in fact, get somewhat used to this.) When the seeing stabilized, I will admit it was nice to have, simply to check focus. Most of the time though, I had already reached excellent focus using the standard focuser. There were occasions (at 220x) in which I was able to tweak focus to provide a better view.
Notes From the Second Evening - The Pronto
Even though it looked to be an unnecessary accessory in my f8.6 TV-102, I thought I would have better results in my f6.8 Pronto. As many of you know the Pronto while being a fine little scope, is in no way Apochromatic. I guessed that fine focus would be more difficult to obtain in the Pronto because of it's faster focal ratio, and I had hoped that the FFA would help me to reduce the levels of color by helping me to bring the scope to a better focus.
Before this I had never really spent much time above 165x with the Pronto. Seeing, access to other scopes more suited for high power work and sanity prevented me from pushing much higher. When I had my Ranger, I did occasionally have it up to over 200x and was impressed by how well this little scope could take the power. I figured most of my testing would be done with the 4mm Radian (120x) or the 7mm Nagler in concert with the 2.4x Ultima barlow (165x). It was a fantastic night. Seeing was 9 (out of ten), and transparency an 8 (out of ten). This was one of those rare nights where the scope just kept up with whatever powers you threw at it. I actually wound up using stupidly high powers (4mm radian with 2.4x barlow - 288x, over 100x per inch!) with the pronto this evening, and I was amazed at how well it performed. Please note - any powers above 100x are typically "empty magnification" - meaning they usually don't show you anything more than you could see at say around 60x per inch. They certainly can be FUN when the seeing supports it though!
With the 13mm nagler there was no benefit to the FFA. With the 7mm nagler and the 4mm radian, the gain was slight, but it did allow me to occasionally "tweak" focus to obtain a *slightly* better image. With the 7mm nagler barlowed, it was a nice accessory to have. With the 4mm radian barlowed, it was a must. (How often and on what targets will one get the chance to use a 70mm scope at 300x?)
I did pay careful attention to color - when focusing the Pronto, it could be focused in such a way that little to no false color was shown, however, there was little point in doing so because it threw the image out of focus. At best focus there was some green on one side of bright objects and some magenta on the other. While there was *perhaps* a tiny bit less magenta when the scope was in best focus (using the FFA), there really was not much difference (if any) to my eyes.
As an aside, I see how some can say there is little to no color in certain refractors (like the Pronto or Ranger) while others moan about how much color it has. Before I got my APO, the slight amount of color I could see through the Pronto did not bother me at all, in fact would have classed it as having very little color (even though I have been using mirror designs for years). After using an APO for a few months now the difference is much more obvious.
Additional Observations - Summarized
Having used it in both the 102 and the Pronto for several months now, I feel I can add the following:
Perhaps in part because of the excellent focusers found on Televue scopes, it was of little help in reducing false color.
The longer I used it at high powers in the 102, the more I liked it. It works very well with the Nagler Zoom - in fact, I can not imagine looking at luna without the zoom and the FFA at this point. If you are a planet fanatic, it really is a great accessory. At 294x, (3mm) the FFA is almost a must. The ability to check and tweak focus quickly is extremely nice to have. Since the Nagler zoom and the FFA are helical, you do need to "hold" the FFA while zooming in. This is not that big of a deal, but it is a two handed operation, and it would be much nicer if the FFA simply had a focus lock.
It's wasn't all that useful in my F10 C8D SCT. The long focal length, and the focus ability of the standard focuser make it some what superfluous, in my opinion. Still if you are a planet or lunar nut it may be worth your while.
Do I need it? Who is the real target audience?
Well, it's not a simple question. A lot depends on your observing style and targets. If you are a "lunatic" (or similar), and keep a lanthanum 2.5, radian 3 or other high powered eyepiece (s) in your tool kit for those rare nights where you can use them to the best of their ability, then yes, you probably want this accessory in your tool kit. It did make things much nicer as far as checking focus is concerned.
With an f8.6 APO - A qualified No. Is it nice to have? Yes. The no is qualified simply because it depends on your observing habits. Personally now that I have used it for a couple of months, I can't imagine doing without it for lunar and planetary work.
With the f6.8 Pronto - No - beyond that while not strictly necessary, it does help finding exact focus. Did it help to reduce the amount of false color in the Pronto? - I'd have to say not much, if at all.
Is it a nice accessory to have in your toolkit? Yes. Most assuredly.
Keep in mind that I am evaluating this for VISUAL use only.
I would have to say that the ones who would benefit *most* from this accessory would be owners of very fast scopes (probably around f6 and below) with greater benefits showing up the faster the scope gets. The NP101 and fast Dobs immediately spring to mind. Individuals whose focuser does not provide the fine focus ability they desire.
Even though I cannot confirm this with the Pronto, friends with other types of fine focus adapters report that they seem to help reduce levels of false color in somewhat larger achromats. So perhaps this would be more noticeable with a larger scope. Perhaps this would also be beneficial to individuals with medium size well constructed achromats.
Owners of the chromachor should check this product out, as it allows you to adjust your spacing between the chromachor and the eyepiece on the fly.
If you spend a lot of time at very high power, this would definitely be an asset worth it's modest cost.
If you are a gadget person who likes neat toys. <- (Me)
If you fall into one of the above groups, you would probably be very happy to have this accessory in your kit.
Who does not need this?
Owners of scopes with medium focal lengths who tend to use powers below 200x on average. The TV-102 for example, receives very little benefit to fine focus capability.
Owners of scopes with long focal lengths probably have little use for this product, unless they spend a fair amount of time at very high powers.
Even if you don't need this - is it nice to have? Yup. I am going to keep it (partly because it's just so neat), but also for those occasions where I am working at very high powers.
Tom, an amateur astronomer from Michigan's Thumb, admits that he has always
had problems resisting interesting gadgets. He further claims this is why his
desk quite cluttered with interesting (and not so interesting) bits.