Peterson Engineering EZ Focus
| Article number: | EZF |
| Availability: | In stock |
| Delivery time: | In Stock |
This precision bearing kit virtually eliminates focuser backlash in all Meade SCTs 7" or larger. This kit is intended for use with all Meade 7" through 12" and all 16" Schmidt-Cassegrain and Maksutov-Cassegrain telescopes - including the LX200GPS, the LX200 Classic, the LX90, the LX50 and the LX10. It will remove most of the backlash in Meade's focusing system and consistently provides a light precise feel to the focuser knob.
Note that the kit does not fit Meade's 14" LX200R and LX200GPS. The 14" is a major redesign of the GPS line, and it incorporates the EZ Focus thrust bearing design. Nor does the EZ Focus fit the Meade LX600 or LX850 SCTs as they use a different focus mechanism.
The EZ Focus™ Kit is used to modify the Meade focus system - it does not replace it. By substituting precision thrust bearings for the existing nylon washers, this kit greatly reduces the need for separate costly, bulky backplate mounted focusers and motorized focus controls. (Or in some cases, the need to waste time in switching over to using Meade's Microfocuser.)
The procedure is simple, and the instruction sheet contains highly detailed step by step photo illustrated instructions. Installation does not require going into the optical tube assembly. You simply unscrew the focuser from the scope backplate to work on it. The only tool you need supply is a simple pair of pliers.
This extremely effective approach to improving focuser action was developed by Michael Hart. Mr. Hart's basic design is posted in the MAPUG archives. The EZ Focus™ Kit significantly improves on the basic design and modification procedure. In addition to the very detailed instructions and step by step photographs that anyone can follow, the kit contains a collection of difficult to obtain items - 2 precision miniature thrust bearings, a custom stamped stainless steel thrust washer, an Allen wrench, a mirror cell retaining bolt, and a packet of special synthetic grease.
The EZ Focus Kit, and how it affects Focus Backlash, Mirror Shift
and Mirror Flop
Focus backlash is defined as the excess play in the focus mechanism. The EZ Focus Kit will eliminate most of your focus backlash.
Let's say you are focusing your scope at high magnification, and it's almost in focus. You need to go through focus at least once and defocus a bit on the other side to really know where the best focus position is. So on purpose, or by accident, you go past the position of best focus. Now you have to turn the knob just a little bit in the opposite direction to get back to the best focus position. You don't have far to go, so you slowly turn the knob. And turn the knob. And nothing happens. THIS IS WHAT WE DEFINE AS FOCUSER BACKLASH. You turn some more, maybe a bit faster now because you want something to happen. And then BAM! The mirror starts to move and before you realize it you're through focus again, and back where you started. THIS IS WHAT'S BAD ABOUT FOCUSER BACKLASH.
There are 3 primary causes of focuser backlash. Typically 90% of your backlash is associated with play in the focuser mechanism itself. And this is the problem that the EZ Focus Kit addresses.
Typically, another 8% of the focuser backlash is due to mirror shift. Your SCT’s primary mirror assembly rides up and down the scope baffle tube to achieve focus. The focus mechanism is attached to a point way out on one edge of the mirror assembly. If the mirror assembly doesn't fit tightly around the outside of the baffle tube, the mirror will "wiggle" a bit from side to side if you push and pull on one edge (which is what the focuser does). THIS WIGGLING IS WHAT WE CALL MIRROR SHIFT. You will be turning the focuser knob while the mirror is shifting, but since the center of the mirror isn't moving until the mirror has completely shifted, you will be experiencing focuser backlash during this period of time.
The EZ Focus kit does not address this secondary backlash source directly.
SCT manufacturers provide a heavy grease on the outside of the baffle tube to reduce the amount of mirror "wiggle" or "shift" that occurs when focusing. This heavy grease squeezes into the gap between the inside of the mirror assembly and the outside of the baffle tube. To some extent, this grease prevents the mirror from shifting.
A lack of grease on the baffle tube is sometimes a source of major mirror shift. If this is your problem, redistributing the grease on the baffle tube and working the grease into the gap between the mirror assembly and the baffle tube will significantly reduce your mirror shift. However, if the gap is extreme or if there isn't enough grease, this "fix" will not work.
The EZ Focus Kit instructions do provide a simple and effective procedure for redistributing baffle tube grease. And the grease provided in the kit is the same grease used on the baffle tube. Removing the corrector plate and regreasing the baffle tube is beyond the scope of the kit procedures, but at least you've got the grease to do the job.
The third source of focus backlash if the fit of the focuser mechanism onto the pin that extends out from the mirror sled. Typically this is very minimal - responsible for 2% or less of the initial focuser backlash.
Now let's talk about mirror flop, mirror shift, and what amount of image shift is acceptable.
Someone in Yahoo's LX200GPS user group differentiated between mirror shift and mirror flop. It's a fine distinction but an important one for us SCT users. Let's formally define this as follows: Mirror shift is mirror "wiggle" from side to side caused by focuser movement. Mirror flop is the same movement, only caused by gravitational effects on the mirror as the scope orientation changes. Both cause image shift, or a movement of the image from the center of the field of view out toward the edge. In the Meade LX200GPS, using the mirror lock prevents mirror flop.
Due to the basic design of the Meade and Celestron SCTs where focus is achieved by moving the primary mirror,, there will always be some image shift during manual focusing. The question is, how much image shift is acceptable? I've heard of extreme cases where images moved completely out of the field of view in a 26mm Plossel eyepiece, or where it took more than 4 complete turns of the focus knob before the mirror finished shifting and started to focus. I'd certainly consider those scopes to be defective.
My personal experience has been barely noticeable image shift with a 26mm eyepiece, and no more than 1/10 of the field of view in a 9mm eyepiece. Yet I've used an 8" LX200 where the image shifted 1/2 way out of the FOV in a 26mm Eyepiece.
Personally, I rarely use the motorized focus for visual use, as the EZ Focus kit permits scopes to snap into focus with even the highest magnifications. If I had significant image shift, I'd be forced into using it. As to how much mirror shift is acceptable.... I can only suggest that you get what you accept.
Pete Peterson
CUSTOMER COMMENTS:
From North Carolina: IT WORKS! IT WORKS! IT WORKS! Yea !!!!! Finally something that works like it says it does !!
From Isle of Skye, Scotland: What a difference! I can even now tell by the feel of the focuser alone whether the mirror is moving up or down.
From Massachusetts: This is the first time I have ever written any company about any product they've made that worked well.
For the first time in the 5 years that I have owned my 8" f/10 LX-200 I feel I finally have the ability to extract the most from the telescope's optical potential. I am strictly a visual observer. Observing at sea level near the coast is always a challenge, but it seemed I never could get a good focus at higher magnifications, no matter how much I fiddled with the collimation, which I thought was the reason why the focus was so poor. I was pretty much resigned to having 100x as the telescope's highest useful magnification.
I installed EZ-Focus last Saturday and used it that night. The difference was dramatic. I was able to achieve excellent focus up to 200x, splitting double stars near 1" of separation consistently. Globular clusters were in focus at 200x, not just a smear of light at that magnification.
From Florida: Your product has improved my telescope's performance beyond the point that I thought it was capable of. Congratulations. Thanks for a great product. Your EZ Focus Kit is excellent and only took 10 minutes to install. All the backlash is gone in my 12" LX200. I may not need that Crayford upgrade after all!
From Arizona: ... let me congratulate you for the improvement in the focuser on my Meade 10" SCT! Jimminy Christmas what an improvement and it "feels right" now!!
From Michigan: I had to let you know how I feel about the EZ Focus Kit. This relatively inexpensive purchase saved me the cost of a Crayford focuser. It is amazing how well it works. It eliminated 75% of the image shift in my 8" LX200 and gave the focuser a VERY smooth and positive feel. It took longer to read the directions than to install it.
From Virginia: I can't believe how much your kit improved the focus movement, backlash and even image shift on my new 10" LX200. This was the best $30 bucks I have spent in a long time.
From Colorado: The kit arrived in yesterday's mail, and I leisurely installed it in the afternoon. Installation was easy - I was able to disengage the focuser on my 8" SCT without trouble, and disassemble it by hand. I was so pleased when I focused the telescope and found that I could move the focuser from inside to outside of focus, and back to the best focus position so easily. I can hardly wait to try the telescope with my CCD camera on a star field. I'll be that my days of soft star images are over at last. Thanks.
From Georgia: I received the kit today and installed it in a little time. Although it was cloudy tonight, I HAD to test this enhancement promptly, so out to the back porch I went. I zoomed in on a streetlamp and tested the focuser, noting that cylinder rotation is much smoother. Intra and extra focal images do not suffer backlash anything close to what I was experiencing with "stock" components. My electric focuser even sounds like it is laboring less! This is a common sense, very simple, highly-useful, non time-consuming modification that every LX200 owner must perform. I encourage it highly. Thanks!
From Melbourne, Australia: G'day from Downunder, I received the focus kit yesterday and with trembling hands I replaced the three washers and added the grease. Hmm, it certainly was easier than expected! Tried my LX90 on a bright moonlit night last night and wow, the focusing was silky smooth and far easier to get any object in focus! Boy, 3 washers and grease and I've got a more accurate focusing system and a lot of backlash gone! So thanks Peterson Engineering Corporation and to Michael Hart for his original design.
From Florida: Congratulations on having great instructions included with your EZ Focus kit. I studied them here at the office, went home at noon and installed both the Mounting Assistant Classic and the focus kit. My scope is an 8" LX200 Classic and I was able to remove the focuser from the OTA. Meade certainly does use a lot of grease on the focuser. Everything fit perfectly, in fact after I had attached the focuser to the OTA, it was so smooth and effortless that I thought I had not attached the focuser to the 1/8" pin so I took it back off, and yes it was attached. I'll put it to the test tonight if this high cirrus stuff goes away. Again, great products and great instructions. My friend will be calling to order one for his LX200GPS even though he has not yet received it.
From Massachusetts: Your EZ Focus worked like a dream on my second-hand LX200 Classic. NO image shift now, smooth and easy focusing with no backlash. Thanks!
From Massachusetts: ...I absolutely love the way it feels and works as compared to the original that was on my 10" LX200 Classic. Thanks for such a great & low cost product.
Posted on Yahoo LX200GPS user group: Just my $.02 about Peterson's EZ Focus: I was not at all thrilled with the focusing action of my LX200 Classic. There was WAY too much mirror shift, lots of backlash, and with each change in direction, a big "dead-space" where the focus wouldn't change at all, then would change dramatically all of a sudden. So I ordered an EZ Focus, and a JMI manual Crayford-style focuser ($169). They both arrived on the same day. Bottom line is the EZ Focus improved things so much that I returned the JMI focuser. The backlash is gone, mirror shift is only a few arc-seconds; in short it works the way it always should have. Thanks for an excellent product.
Email rec'd: Last week I installed the EZ Focus kit on my LX 200 GPS 10". I also installed the EZ Clutch kit. Of course as soon as I did so It rained for a week. :-( But it did clear this week and I took my scope out for a shake down cruise. I put my scope on the tripod (using the Mounting Assistant!) and went through the alignment procedure. I did not use the electric micro focuser the rest of the night. This is big. Prior to installing the EZ Focus kit the coarse focuser was exactly that. Very coarse. So bad it was essentially unusable with major backlash and mirror shift. So to spend an entire observing session without once using the micro focuser is phenomenal. Thank you very much. .............. PS The EZ Clutch works pretty good to. And I as so happy with these products I just ordered an EyeOpener as well. I wish you made more stuff!
From Arizona: Sirs, I received the Focus Kit today for my new Meade 12" LX200R. It took me all of 25 minutes to install the new kit. The instructions were very accurate and easy to follow. I set my scope out in my drive after the moon came up. To be honest, I really didn't have any great expectations. I put in a high power eyepiece (12mm) and My God!!! what a Difference your product made. It was unbelievably clear, smooth as silk. I'm sure you've every story about this Focus Kit but I just wanted to pass on my MOST SINCERE THANK YOU.
From the UK "Finally got around to installing the EZ Focus Kit and used it in anger for the first time. It really is a huge improvement. I can now almost spin the focus knob as everything moves so much more freely, and most importantly, the focus action is now direct and without lag. Meade deserve a kick in the tweeds for making such a hash of it in the first place - especially given that the purchase price of the 12" LX90 was not insignificant to me! The EZ Focus Kit (minus postage) cost me a shade over £15. I really don't understand Meade scrimping over that sort of money, I would have gladly paid the extra for good focus control - which let's face it, is an absolutely essential telescope function! Enough preaching to the converted, cheers Pete, if only all my Astronomy purchases were so cheap and made such a difference!"
From New York: After lots of hesitation, I finally installed the EZ Focus kit, which I had purchased from you months ago, on my LX200 10" Classic. I had been apprehensive about breaking the scope in some way but yesterday I went for it. And to my surprise, it was MUCH easier to do following your instructions than I had anticipated; and better still, it really makes a HUGE difference in ease of focus, getting the images to snap into focus. Many thanks for a great product!