Wait for Starlight MicroFocuser or Feathertouch Focuser - 1.5'' Drawtube w/Internal Brake System

Hey guys I am getting ready to upgrade my focuser on my Celestron Nexstar 9.25 GPS. The Starlight microfocuser I had wanted is not available for my scope yet since my 9.25 SCT was the latest addition to the Nexstar line. I have heard good things about them from friends with the Nexstar 8 and 11 though. Since the focuser is unavailable yet (although i hear it will be in a matter of months) I started looking at the Feathertouch Focuser - 1.5'' Drawtube w/Internal Brake System. It has gotten pretty rave reviews, but it is $300 without the adapter I will also need for my scope. I am also aware that I might experience some slippage due to the weight I put on it. I hear the internal brake system which I would get would alleviate that. You can see my current load on the back of my scope in the attached picture(also imagine a Canon Digital Rebel at the end, I had to take the picture with something you know, hehe). My questions are three fold. First which do you think I should get? Wait for the microfocuser or get the crayford style. Second if I go with the crayford style what draw tube length do you recommend for my application? (astrophotography with the rebel) They have 1.5", 2.0", and 2.5". And lastly is their a competing crayford style focuser that is cheaper and may be of comparable value? THANK YOU!!!

I have posted links for both products below.
http://www.starizona.com/teleacc/show.cfm?StockNo=FTF15IB&Show=1
http://www.starizona.com/teleacc/show.cfm?StockNo=FTFSCTC11&Show=1

Attached Image:

David,
The MicroFocuser relies on the existing moving mirror focuser inherent in the scope and thus does not remove the problem of image shift during focusing, though you may notice it much less when fine focusing. The external Crayford focuser just moves the eyepiece, so the optics remain stable while focusing. Image shift can be a real pain when trying to put an astronomical object onto a small camera chip and keep it there. This is the big advantage of using an external focuser (ie. one that moves the eyepiece/camera rather than the mirror).

You could also possibly modify the scope a bit so that you could lock down the primary mirror once you've achieved rough focus and just use the Crayford to fine tune; many owners of Meade SCTs do this; Meade ota's (at least the older ones) have a hole in the rear cell through which a stabilizing bolt can be inserted to fix the primary mirror in place). This bypasses the problem of primary mirror flop during long exposures.

There are a number of lower cost SCT Crayford focusers available including units from JMI, Apogee, William Optics and others. There is also the Clement Focuser, which takes a very different design approach, but these are in the same price range as the Feathertouch focusers.

Best of luck!
Tim Cross

I have the Starlight mini on my NS8GPS and I love it. I also have the Feathertouch on my Dobs and they can't be beat.
However I tried a JMI NGF 2" (http://www.binoculars.com/products/Jims_Mobile_JMI_Next_Generation_2_Inch_Focuser_for_Cassegrain_Telescopes_30940.html)
on my NS8GPS and the worst thing is the clearance between the fork and the tube. The diagonal will hit the fork before zenith is reached. At least it did on the NS8GPS. Also, the regular focuser still gets used as the JMI did not have enough travel for all my EPs. So a gross focus is done with the regular and a finer focus is done in the JMI. I sold the JMI because I thought this was a hassle. But the Crayford does eliminate mirror shift which is good for photography.
If you have the clearance and do not wish to use it at zenith then I guess the Feathertouch would be fine.
What is the difference bewteen the NS9.25GPS and the NS8GPS that requires a different focuser? You would think they would be the same. :S
Floyd

So it seems the crayford is what I will do, but how long of a draw tube will I need. I do have an extension I use on my off axis guider so I can connect my camera and not hit the guiding eyepiece so I do have a longer than usual length, but I also do allot of visual astronomy. Is there any reason I would need longer than the typical 1.5" of drawtube travel? It isn't that much more so I don't mind do it right if I need it, but I don't know much about this particular subject.

David,

I use a Celestron C14 and the Feathertouch Focuser. I also did a write up of it in the articles section if you want more information.

Paul Atkinson

Now I am a little more confused than I was before I hadn't much thought about clearance issues because as you can see from my original photo my scope is on a wedge. When photographing zenith I thought I would have plenty of clearance. Am I wrong in that respect? Also I had considered the weight issues but I was hoping my weight system I bought would be able to counteract the imbalance created by the extra equipment. I have the system from Starizona. http://www.starizona.com/teleacc/show.cfm?StockNo=CWGPS925-CS&Show=1 I am not quite sure I know what to do now, I was heavily leaning towards the crawford style because I figured the less I moved the mirror the less vibration I would have allowing me to get more shots off. Is there anyone out there using the Nexstar 8, 9.25, or 11 inch that is fork mounted and has done the crawford style focuser? And from what the other gentleman said, is remounting my OTA a possibility? (i'd rather not mess with that)