Keyboard Shortcuts
Likes
Search
Re: How many turns of the focus knob?
|
Gary Jarrette
¿ªÔÆÌåÓýHi Keith ? I know of the secondary focuser you are referring to but have not used one. Jeff is a great guy and his products are top notch. ? On my 14¡± Celestron Edge I was using the Starlight Instruments ¡°Shorty¡± Focuser with .800 travel. Behind that Jeff¡¯s Optec Pyxis LE Rotator. Attached to that the QSI 683wsg camera with built in filter wheel and Off Axis Guider (OAG). This fit nicely into the 5.750 inch back focus with the proper spacer from Starlight Instruments. ? It, of course, goes on the 11¡±Celestron as well. ? Recently I purchased a Gemini Rotator/Focuser combo, affectionately called the RoFo by me, and it too fits into the back focus of the afore mentioned scopes just fine with a QSI 683 hooked up to it. I can tell you that this Gemini is a fine piece of gear. It is the cat¡¯s meow. The focuser has .11 micron steps. It is just phenomenal. ? Although I have not used the secondary mirror focuser I do know Jeff¡¯s products are engineered well. ? If you purchase the secondary focuser I would be interested in hearing how it works for you. ? Take care. ? Gary ? Carpe Noctem ? From: C14_EdgeHD@... [mailto:C14_EdgeHD@...]
Sent: Friday, July 15, 2016 7:05 AM To: C14_EdgeHD@... Subject: Re: [C14_EdgeHD] How many turns of the focus knob? ? ? Gary, First let me thank you for your interest and feedback on this issue. Very helpful. So thank you very much. ? I actually had?another possible solution waiting in the wings. A very interesting one here. ? I stumbled across this solution because of a different problem. I couldn't fit a rotator, focuser,?OAG, filter wheel, and camera in the allotted 146mm of back focus.?Optec's offering moves the focuser to the front of the?scope, taking advantage of Celestron's Hyperstar capability.?The?FastFocus(er) places the secondary at?Celestron's factory point, at the focuser?midpoint of travel. So, I could have moved the secondary inward the less than the?0.03" I was lacking,?with?plenty more?to spare. Not only that, but they have enough movement in their system (0.36") to be able to move between?f7 & f10 (~8 turns of the focus knob, ~0.24") without ever unlocking the primary. I had some concerns that they only use a 1/4 20 threaded rod?to move?their focus, but discussing this with Jeff, their product development chief, I learned they use a high precision 1/4 20 rod, and that they tested everything up to 80 tpi (too fine) and there was no advantage going?higher than 20tpi.?I also like that they use 6 screws to collimate/stabilize the 2ndary. I find Celestron's mounting sags a little. Hopefully this will be better...? ? You're right Gary, its hard to diagnose over the internet, but I was 8mm of backfocus away from the recommended distance. That's a lot. The very close to the end of fwd mirror?travel of the f7 configuration has been confirmed by a couple of scopes I've had now, and several other users?I've corresponded with. At f7, they report?varying between?1/2 to 1-1/2 turns left. ? Regards, ? Keith ? From: "Gary Jarrette garyjarrette@... [C14_EdgeHD]" <C14_EdgeHD@...> ? ? "Don't look a gift horse I? the mouth". If it works good go with it. It still however sounds close to the end which puzzles me I still am not sure about your back focus spacing though but without hands on it is tough to diagnose problems via the Internet. You, I take it, are using the stock focuser on the mirror. I have a Micro Focuser so perhaps there might be some difference and to be honest I just don't know. In any event you can image so for now you can play. Take care Gary Carpe Noctem Sent from my space ship via my LG V10 Phone ? On Jul 14, 2016 6:59 PM, "'keithnk@...' keithnk@... [C14_EdgeHD]" <C14_EdgeHD@...> wrote:
? |