One good corner when not using a reducer - How come?

[ollypenrice]

I am sure that Sara is not rotating her images for display, she is showing them exactly as they came off the camera both before and after rotation.

My take on this is as follows:-

Focused, 'clean of aberration light' is falling in one place only - the bottom left hand corner of the sensor when it is in its original position. The focused, 'clean of aberration light' falls in the same place behind Sara's telescope irrespective of the angle of the camera or indeed whether the camera is even there or not. Thus rotating the camera to any angle results in this 'good' light continuing to fall in the bottom left of the frame. If the camera is rotated 180 degrees then when Sara downloads her image, the software doesn't know the camera was rotated so the 'good' light now appears to us when the image is displayed to be in the top right of the frame.

Yes! that's what I think too. If the good corner moves on the captured image when the camera is rotated then the good corner is not following the camera. Exactly as you said a while back. It will be the focuser, sure as eggs.

Olly

[ollypenrice]

It seems that it is either a slop problem or collimation

I would check for slop when placing the camera at the focuser and if it exists i would buy a hotech sca adaptor (actually i have bought one in order to make sure there is no slop when placing my camera/oag at my focuser)

Also i would check the collimation of the optics and especially the tilt of the secondary mirror, a good tool for checking its collimation is the concenter MkII collimator Spheretec

A good idea as mentioned as above is to check that the focuser's collimation

Sara has a refractor.

Olly

[Merlin66]

OK guys, let's assume the above is correct; that as the camera is rotated it passes through the "focused image point" - this infers by result that the camera attachment is sitting at an angle to the focal plane of the objective....so, either the focuser is sitting "off" to the optical axis or the objective is mis-collimated to the focuser...

Yes/ No

[Earl]

OK guys, let's assume the above is correct; that as the camera is rotated it passes through the "focused image point" - this infers by result that the camera attachment is sitting at an angle to the focal plane of the objective....so, either the focuser is sitting "off" to the optical axis or the objective is mis-collimated to the focuser...

Yes/ No

Or the t-thread adapter and gubbins connecting it to the scope is not true.

[barkis]

Then perhaps the modded camera's sensor lost an alignment shim on reassembly, and it's the sensor that is misaligned .

Ron.

[steppenwolf]

OK guys, let's assume the above is correct; that as the camera is rotated it passes through the "focused image point" - this infers by result that the camera attachment is sitting at an angle to the focal plane of the objective....so, either the focuser is sitting "off" to the optical axis or the objective is mis-collimated to the focuser...

Yes/ No

I agree.

Then perhaps the modded camera's sensor lost an alignment shim on reassembly, and it's the sensor that is misaligned .

If that were the case, the 'good' light would remain in the same corner of the sensor which it isn't.

[swag72]

OK, so now I am back from my gammon, egg and chips, let me answer a couple of questions.

1) I am not rotating the images, they are presented exactly as I have them out of the camera.

2) Regarding orthogonality of the camera I am using the following. T ring (Only goes in one way, must be orthogonal), Extension tube ( screws into the t ring and then the focuser, but I an so **** about this issues that I am absolutely certain that you would all be happy with them being square!)

So, we have come down to two things - misaligned focuser OR optics. So, the focuer is probably the easier thing to deal with first.

I have a couple of things I can do when next out (cloudy today!!) - put on the old focuser that was removed as I had focuser sag - See if that makes any difference. Or, I can adjust the moonlite (another thread will be started for this!!) and see how that goes.

The other thing I have had to deal with in this sad focuser debarcle is the flange. I've had to try to get that square as well as it wasn't.

So, where do you suggest I start now?!

[Earl]

Can you use it on another scope?

This could as least resolve if its collimation of the focuser without the need to tinker?

[swag72]

I have an Equinox 66, but I don't think it will take this focuser size. To be honest, the Equinox is new and unused, so don't want to fiddle with that lovely little scope yet. Can out the old focuser on the 120ED though if that would help?

[Earl]

Might be worth a try.

[Steve]

Have you checked your focuser's alignment? It is easily done with a laser and some paper or acetate over the objective with a clearly marked centre. Put the laser in the focuser then switch it on, the spot should exit the objective at it's centre. I am guessing it doesn't. Loosen the focuser's three fixing screws then manouver it til the spot is on the centre, then tighten. Easy

Find a laser and some paper or acetate. You will soon have the solution.

Remember, you are looking to seat the focuser square onto the telescope. There are only three screws involved, the ones that fix the focuser to the telescope tube.

[kookoo_gr]

can you tell what is the process with the paper you say? i'm curious about it

@olly oops i didn't notice it was a refractor

[Merlin66]

You put a paper cover over the objective, with a central mark; a collimated laser in the focuser should hit the mark.

[Steve]

can you tell what is the process with the paper you say? i'm curious about it

Skywatcher Evostar telescopes use simple rolled steel tubes and the focuser is attached via three slightly oversized screw hole so it is not unusual to need to loosen the screws slightly then push/pull the focuser into optimum alignment.

If you make what is essentially a paper or acetate lens cap you will be able to see the laser spot as it exits the telescope objective. If you have the centre clearly marked on the 'cap' it will be easy to see whether the focuser is on or off axis. It needs only basic Blue Peter skills

HTH

[swag72]

Hi Steve, So a cheapo laser from the bay will do it? If so, I get what you are saying about the paper for getting it central, but Don't I need a way to ensure that the laser is in directly in the middle of the focuser? Not sure how I could do that?

Another question regarding the moonlite - What am I adjusting? Just the screws into the flange? or is there some adjustment within the focuser itself? Another question is regarding the flange, which I've also had to butcher - Will that ever come into the equation?

[Steve]

Hi Steve, So a cheapo laser from the bay will do it?

Only if you are prepared to align that first, cheap laser collimators are rarely accurate out of the box. Can you not borrow a good one?

If so, I get what you are saying about the paper for getting it central, but Don't I need a way to ensure that the laser is in directly in the middle of the focuser? Not sure how I could do that?

Just fit it into the focuser and lock it the same way you would your camera or eyepiece (without a diagonal).

Another question regarding the moonlite - What am I adjusting? Just the screws into the flange? or is there some adjustment within the focuser itself?

You would have attached the Moonlite via the same three screw holes that held the original focuser. Loosen the three screws just enough to enable you to adjust how the focuser sits. If you watch the laser spot on the paper you will clearly see the effect your adjustments are having on alignment. It is a long tube so ask a friend to tell you when the spot is central. Do not adjust the Moonlite focuser's mechanism, loosen only the screws that hold it to the OTA.

Another question is regarding the flange, which I've also had to butcher - Will that ever come into the equation?

Butcher? That doesn't sound good.... !

If you have adjusted the Moonlite using the four small set screws then this is going to take longer than I thought?

I need to log off now as I have family staying over but I'll look in again Monday.

HTH

[swag72]

Only if you are prepared to align that first, cheap laser collimators are rarely accurate out of the box. Can you not borrow a good one?

Unfortunately, don't know of anyone in Spain, so will have to buy one and get it shipped over.

You would have attached the Moonlite via the same three screw holes that held the original focuser. Loosen the three screws just enough to enable you to adjust how the focuser sits. If you watch the laser spot on the paper you will clearly see the effect your adjustments are having on alignment. It is a long tube so ask a friend to tell you when the spot is central. Do not adjust the Moonlite focuser's mechanism, loosen only the screws that hold it to the OTA.

Yes, this is where I've done all of my alignment so far, I've not adjusted or touched any of the moonlite's mechanism.

Butcher? That doesn't sound good.... !

If you have adjusted the Moonlite using the four small set screws then this is going to take longer than I thought?

Butcher ...... (!!) Part of my potential issue (I thought) was that the flange holes were not allowing a totally square seat on the OTA, so with a small file a couple of the flange screw holes have been made a little longer so that when the flange screws into the OTA it doesn't push up and away from the OTA which was happening. At the moment I have the flange and moonlite seated squarely on the OTA, whereas before there was an uneven gap around the join

[Steve]

Unfortunately, don't know of anyone in Spain, so will have to buy one and get it shipped over.

You can borrow mine, I'll send it Monday when back at work

I've not adjusted or touched any of the moonlite's mechanism.

Excellent

HTH

[swag72]

You can borrow mine, I'll send it Monday when back at work

That is such a great offer -Thank you - PM'd

[ollypenrice]

You seem to be judging the orthogonality of the focuser by the way it looks against the end of the metal OTA. This assumes that the metal end of the OTA was cut off perfectly square in China! Plus some other assumptions. These will not be good assumptions!

Steve's laser idea is top, as is his offer. Quite a setup at FLO, it must be said.

Olly

[Steve]

Quite a setup at FLO, it must be said.

Thank-you Olly but I think it is SGL's community that has shined brightest. Sara posted her question only yesterday. Within 24 hours she has seven members, including yourself, posting considered responses that has resulted in a solution. At least we hope it has...

[swag72]

Thanks to all, you've been fantastic as Steve has said. I have really appreciated your help to try to sort the problem.

As if by magic a collimator came up in the classifieds, so I have made a purchase. I won't get it until mid November, so you can all breath easy, knowing that another 'HELP' thread will probably come at that stage or, if there are any believers out there, pray for me that the problem will be sorted and there will be a massive 'THANK YOU' thread instead!!

So, until November, on this issue, I bid you adieu!!

[Sp@ce_d]

Hope you don't mind me jumping in on your thread Sara..

I've been having a problem with one corner & this thread prompted me to check my focuser alignment. So I got a laser from FLO as recommended by Steve...

It seemed mine was out by about 4mm. Unfortunately the clouds rolled in tonight just after my guiding calibrated so not been able to test it yet..

One thing I'm still trying to work out is the position of the dot in the Hotech faceplate. As there are no instructions for a refractor I'm not sure if this is relevant or not. Certainly it's centred now at the objective.

[Merlin66]

Hmmm, that's interesting.

I usually use a Cheshire to view the reflections from the various objective elements and collimate the lens to the tube to bring them concentric. You seem to be getting a strong enough reflection (probably from the rear element) to show on the laser screen. I would have thought if the lens was square to the optical axis and the focuser square to the lens that this reflection would have been central and not off set.....makes me think the lens needs collimating....is there any movement of the reflected dot if you rotate the laser in the focuser????

[Sp@ce_d]

Hmmm, that's interesting.

I usually use a Cheshire to view the reflections from the various objective elements and collimate the lens to the tube to bring them concentric. You seem to be getting a strong enough reflection (probably from the rear element) to show on the laser screen. I would have thought if the lens was square to the optical axis and the focuser square to the lens that this reflection would have been central and not off set.....makes me think the lens needs collimating....is there any movement of the reflected dot if you rotate the laser in the focuser????

Ahh.. good call. Ok went and tried that. You're right, it wasn't moving equally around the laser faceplace lines. So I unscrewed the lens and cleaned the threads, checked seating and reassembled. Now it looks much better and the dot moves around the innermost circle on the laser faceplate

Just need some clear sky to test..