RASA 11 v2 lens group loose and attached fast to my PP adapter

[Fegato]

Oh well, I suppose it was always going to happen. I know it's happened to others. Just took my image train off the RASA for a bit of attention, and when screwing back on, the lens group started to move with it at the final tightening. The two now move together and I can't separate easily. Celestron say "don't overtighten".  Easier said than done - you have to tighten enough that it's not loose, don't you, and I always try not to overdo it.

I'm a bit tired, and no time right now, so leaving it until tomorrow now. I'll take the image train off the PP adapter and see if I can get that off. God knows what I do after that. From what I have read so far, you have to take the corrector plate off to get it back tight again. I don't really fancy that. I think I'm within my 2 year warranty, so I guess that's the route to take...

Anyone else had to go through this?

 

 

[tomato]

A while back I had the lens assembly come loose on my RASA8 when trying to unscrew the collar on the camera adapter plate. After due deliberation I decided to leave the corrector plate in place and instead I removed the mirror cell from the other end of the tube.  This was just a case of unscrewing the four retaining screws and making sure the cell went back on in the same orientation.

Once the mirror cell was off it was a simple case of putting my hand up the tube and holding the baffle to enable the adapter ring to unscrew. Then it was a case of tightening the lens assembly collar back up, still holding the baffle with my arm up the tube. One good thing about reflector F2 scopes, your arm is long enough!

Once the mirror cell was back on, initial collimation was done with an Ocal collimation camera, then attaching an ASI120 to the RASA to allow adjustments on an out of focus star.

This was the first  image captured after the remedial work was done.

 

Edited March 12, 2023 by tomato
typo corrected

[gorann]

It happened to one of my RASA8 about a year ago. I realized I needed four hands to solve the problem so I got my wife to help me to tighten a rubber band from a rubber strap wrench (like this one https://www.maxclawtools.com/rubber-strap-wrench-sw-530.html) around the lens group ring and hold it fast so I could loosen the camera adapter ring and camera. I then tightened the ring on the lens group hard (so it would not happen again). A star test told me that nothing bad had happened so no collimation needed. I have since then added a tiny amount of grease to the camera adapter ring so it will not jam.

[Fegato]

Thanks Göran, yes I was thinking rubber of some sort was the answer to holding the ring while getting the adapter off.  Surprised you managed to tighten the lens group back too, I thought once it was turning the whole thing turned and you couldn't get it tight again. I'll give it a go!

[gorann]

2 minutes ago, Fegato said:

Thanks Göran, yes I was thinking rubber of some sort was the answer to holding the ring while getting the adapter off.  Surprised you managed to tighten the lens group back too, I thought once it was turning the whole thing turned and you couldn't get it tight again. I'll give it a go!

I could have been lucky but it is worth a try.

[JOC]

FWIW I have had enormous amounts of success at loosening things with the following:

Rubber bands wound around the offending objects to provide grip

A pair of good fitting rubber gloves can provide some added traction - or just grip the object through a glove stretched over it

Don't underestimate the power of a adding a damp cotton tea towel to the equation

A rubber jam jar opener is a wonderful tool that doesn't mark things

A metal jam jar opener is useful and incredibly successful, but will mark things if you aren't careful - though you can sometimes cover stuff with an old cloth or tea towel first to protect things a bit

If things can take it and/or don't mind getting wet the appliance of science does often work - get the bits to different temperatures - the classic run the lid of the jam far under the hot tap approach, or a careful flick around with a hobby heat gun or hair drier works esp. well for things made of different materials as they expand at different rates

If it's a ground glass stopper in a conical flask a ring of water around the top and tap the outside of the stuck joint with another glass stopper is surprisingly effective

Pressing one stuck end of the stuck object combo against the rubber sole of a held still shoe or slipper sole and twisting the offending stuck bit also helps

Once free, and only if the situation allows a smidgen of Vaseline on the threads before reassembling can stop it happening again.

[tomato]

36 minutes ago, Fegato said:

Thanks Göran, yes I was thinking rubber of some sort was the answer to holding the ring while getting the adapter off.  Surprised you managed to tighten the lens group back too, I thought once it was turning the whole thing turned and you couldn't get it tight again. I'll give it a go!

Agreed, I can see how gripping the collar will allow you to unscrew the adapter plate, but how can you tighten the lens assembly collar if you can’t grip the other end of the lens holder?

[Fegato]

Well, I had a little go this morning, and the PP adapter and image train just screwed off OK.  Lens group seems pretty solid. But it's definitely nearly 90 degrees out of kilter with where it started, as the camera doesn't go back to its normal orientation. So I really want it back where it started....   rubber tool on order, I guess I'll try and move it back with that. Really I should probably to go back to Celestron as it's in warranty, even if that means weeks without it...

[Fegato]

Funny how sometimes you don't analyse properly what's happening when something goes wrong. It crossed my mind in the early hours of the morning while half asleep in bed that my lens group was turning quite slowly with some fair resistance, and I wondered if perhaps the whole corrector had been turning. Checked in the morning, and all the screws at the front were loose. I'd put on a Celestron dew heater last year, and obviously hadn't tightened them enough and they'd worked loose. I've got the whole thing back into the original orientation, and had a quick trial in a clear spell last night and everything seems OK now. Lucky, I guess!...

[gorann]

6 hours ago, Fegato said:

Funny how sometimes you don't analyse properly what's happening when something goes wrong. It crossed my mind in the early hours of the morning while half asleep in bed that my lens group was turning quite slowly with some fair resistance, and I wondered if perhaps the whole corrector had been turning. Checked in the morning, and all the screws at the front were loose. I'd put on a Celestron dew heater last year, and obviously hadn't tightened them enough and they'd worked loose. I've got the whole thing back into the original orientation, and had a quick trial in a clear spell last night and everything seems OK now. Lucky, I guess!...

That was a new one I had not heard of. Great that you could fix it!

[gorann]

PS. Do you need a dew heater? Those of us using RASA8 get enough heat from the camera inside the dew shield to keep dew or frost away (works for me even at -18°C)

[Fegato]

Yeah not sure. Gets very dewy here, and my 8 Edge HD will dew up in no time, so I just got in the habit of putting them on everything. With the big Celestron aluminium dew shield and the camera, you may well be right, but obviously the 11 is a fair bit bigger, and as it all works, I'm loath to change anything. I'm on mains power, so no big deal I guess.

[ollypenrice]

1 hour ago, Fegato said:

Yeah not sure. Gets very dewy here, and my 8 Edge HD will dew up in no time, so I just got in the habit of putting them on everything. With the big Celestron aluminium dew shield and the camera, you may well be right, but obviously the 11 is a fair bit bigger, and as it all works, I'm loath to change anything. I'm on mains power, so no big deal I guess.

On days when everything in our 4-scope observatory is wringing wet there is never any moisture of any kind on our RASA8 corrector. That's with a short, home made dewsheild which extends just to the back of the camera.

Olly