I assume tilt to refer to focuser sag oor the camera chip not being square to the optics for any reason.
I assumed collimation means aligning the doublet lens so they are aligned with each other. Perhaps the doublet moves as a whole and not as individual lenses with each other. In which case collimate away to sort out tilt.
Perhaps get that definition clarified before you proceed.
Something for you to check prior to doing a star test, some of the older model Taks were susceptible to vibration causing the collimating screws on the lens cell to loosen and the lens cell to move slightly and flop.
Can you check and eliminate that, unscrew the Dew Shield and see if the black lens cell will move against the push/pull screws by using your hands (without touching the objective of course).
I could not remember the chap in Melbourne's name on the phone last night,but his name is Rodger Davis-formerly of Binocular and telescope repairs,his shop became Bintel in Melbourne,Rodger is still there-I've talked to him a few times and had a repair done by him.He is the chap to have a talk with David.Worth a phone call.
Something for you to check prior to doing a star test, some of the older model Taks were susceptible to vibration causing the collimating screws on the lens cell to loosen and the lens cell to move slightly and flop.
Can you check and eliminate that, unscrew the Dew Shield and see if the black lens cell will move against the push/pull screws by using your hands (without touching the objective of course).
One less thing to be concerned about...
Cheers
John - the whole lens cell is hard against the tube at the top, but there is about a 0.5mm gap at the bottom - is that normal?
John - the whole lens cell is hard against the tube at the top, but there is about a 0.5mm gap at the bottom - is that normal?
Chris - thanks for the name.
DT
Just wanted to check that it is not loose, that is not normal, I had an FS-102 arrive with 4 of the six collimating screws having fallen out.
The gap can vary, normally it would not be hard up against the mounting ring, if it hard up against the ring there is little or no room for adjustment.
The screw setup is a push/pull arrangement, the short screw is threaded through the lip on the lens cell and pushes against the front ring, the longer screw is again threaded through the lip on the lens cell but is threaded into the front ring and pulls the lens cell.
When collimating, you DO NOT take the lens cell apart, you use the push/pull screws to adjust the squareness of the lens and center your diffraction rings.
Before you do any of this though, I would still strongly suggest doing a proper star test to make sure it is out of collimation. I have done an FS-102, FS-128 and a Sky 90 successfully but you do need to take your time.
Hi David, I was making some enquires re collimating a Tak scope that I didn't end up going ahead with and Claude Voarino from AEC inSA the Tak dealer recommended:
Astro Optical Supplies - their phone number is: 02 9436 4360, Just ask for Neil.
Have you looked at it through a cheshire at all? If it looks good through that, then the collmination will be pretty close. You can even do it in the lounge room, if you have a decent torch to replicate the sun.
The collmination would have to be really bad to get those streaky stars and they wouldn't be in just one corner. Here's an image of mine and the curvature map from it's subs. It has droop from using a 2" coupling but the stars in the image aren't as bad as the map suggests they should be.
Robin - you might be on the money. I've only noticed the elongation when shooting without the reducer/flattener. Might be better to let sleeping dogs lie!!
I'll post on Tak uncensored and report back, as well as trying a star test in due course.
Dave, if you do a pinpoint on the subs, it will tell you the orientation of the camera.
In my example the camera was at 275degrees +/- bugger all
Oh, and you may be able to get a handle on what's going on by firing up the light box, shooting flats and running them through ccd inspectors flat file analyser. It will show tilt on a flat. All stuff to try in daylight or when it's raining
I've been out over the weekend. I did a start test as requested - which yielded beautifully concentric circles through several different eyepieces and a 3x barlow.
I've started using a Robofocus with this scope. When I leave the focus lock undone, as suggested in the Robofocus manual, I can "wiggle" the focus tube - this goes away when the focus lock is screwed up. A gentle tighten of the lock removes 99% of the wiggle, and doesn't seem to affect the Robofocus - though eventually something must wear...
I ran some images through CCD inspector which were taken at different angles. The distorsion is in different areas of the frame, so at least I'm happy that the CCD sensor isn't the problem. The tilt varied a little as well through the night.
My next plan is to try the instructions that JohnG sent through about adjusting the focuser.
I did some reading about collimation on Tak Uncensored, but the usual advice from Art was to send it in for cleaning and collimation. Haven't had a chance to post there as they took ages to approve my membership.
Thanks again for your advice and I'll report back further progress,
I managed to do some imaging again on Saturday night. I found that if I just tightened the focuser locking knob, the wiggle in the draw tube was gone. So was the mis-alignment evident on CCD inspector. I'll have to do some more investigating, but I think this may be the problem...
This is an oldish post that I have come across. As a Tak owner, if you have not resolved your problem, I may be able to help as I have overcome the same challenge.
Can I please revive this thread? I have either tilt or miscollimation though it is with a FSQ85. I cannot feel any play in either the focuser or the CAA. I have done some tests pointing the scope to the zenith. In one particular position the stars are good enough in all 4 corners, but I cannot reproduce it in the other position. Clearly the scope is capable of producing good result but I just don't know how to make it perform consistently. Any advice appreciated.
If when pointed at zenith it is good but not when pointed elsewhere, that sounds like tilt. Under this instance it would only be miscollimation if the lens was moving within its cell, this would be very obvious! My bet is on tilt
