Diagnosis Please!!!

[Tim]

At least you can relax about the camera mod and go collect some Ha data

[richyrich_one]

Thanks again for the help.

 

[Gerry Casa Christiana]

To me it looks like collimation is a little out. Also try a star test to make sure the collimation is bang on. I flocked my scope recently and dismantled everything and it took me ages to get it right but it's better now than before. At least it's not your camera!

[richyrich_one]

On 27/12/2016 at 09:55, Gerry Casa Christiana said:

To me it looks like collimation is a little out. Also try a star test to make sure the collimation is bang on. I flocked my scope recently and dismantled everything and it took me ages to get it right but it's better now than before. At least it's not your camera!

I too dismantled everything to flock the scope and it's never been the same since. This is my master flat analysed in PI from the night, the camera was rotated 90 deg from the M45 shot but something is definitely out. This was after another complete rehash of the collimation and everything looked good with the cheshire.

 

[Gerry Casa Christiana]

Can you send me a picture of the inside with the collimating cap in the eyepiece. Just use your phone. I might see what's wrong if anything. 

Also the main clips that hold the mirror how tight did you do them? You should put a business card underneath then tighten down so you can pull the card out. I made that mistake too! 

[newbie alert]

Looking at the pic and the star spikes your using a newtonian...and they suffer from coma issues unless youre using a corrector..is your collomation right...all things to look at before you put the camera on the chopping block...have you another camera you can use or borrow to see if it has the same effect

[richyrich_one]

6 hours ago, Gerry Casa Christiana said:

Can you send me a picture of the inside with the collimating cap in the eyepiece. Just use your phone. I might see what's wrong if anything. 

Also the main clips that hold the mirror how tight did you do them? You should put a business card underneath then tighten down so you can pull the card out. I made that mistake too! 

Thanks for the business card tip, not heard that before and I'll definitely give that a go.

I'm not able to get out to the obs at the moment but I took this through the cheshire just before I went out that night. It looks good to me hopefully you can see something I can't. Actually it does look slightly out in the photo but it looks spot on in reality.

Cheers

 

[Gerry Casa Christiana]

13 hours ago, richyrich_one said:

Thanks for the business card tip, not heard that before and I'll definitely give that a go.

I'm not able to get out to the obs at the moment but I took this through the cheshire just before I went out that night. It looks good to me hopefully you can see something I can't. Actually it does look slightly out in the photo but it looks spot on in reality.

Cheers

 

 

No that looks pretty good to me. Do the mirror CAREFULLY loosen them up. You don't want the mirror rattling around but you don't want those clips pulling the mirror otherwise it can make strange star shapes. Looking at your flat it could be just one clip that us pulling too much. They call it pinching of the optics. With mine I could still actually move the mirror in the cell afterwards with a little effort. Just enough to hold it. 

By the way later invest in a Baader laser collimator. I got one for Christmas and even after all my fiddling before it was still out! If you want it perfect and you use your scope it's something you'll really appreciate. 

 

 

 

To me it looks like collimation is a little out. Also try a star test to make sure the collimation is bang on. I flocked my scope recently and dismantled everything and it took me ages to get it right but it's better now than before. At least it's not your camera!

[richyrich_one]

27 minutes ago, Gerry Casa Christiana said:

By the way later invest in a Baader laser collimator. I got one for Christmas and even after all my fiddling before it was still out! If you want it perfect and you use your scope it's something you'll really appreciate. 

I already have one of those but it's no longer collimated so it's kind of useless. Be careful with yours, there's no way of recollimating it.

If I get another laser it won't be one of those.

I still can't get my head around a half inch thick piece of glass being distorted by a mirror clip but i guess it does.

[Gerry Casa Christiana]

1 hour ago, richyrich_one said:

I already have one of those but it's no longer collimated so it's kind of useless. Be careful with yours, there's no way of recollimating it.

If I get another laser it won't be one of those.

I still can't get my head around a half inch thick piece of glass being distorted by a mirror clip but i guess it does.

Trust me it does! Also you want to sort it out because if it is left too long the slight warping can become permanent.

Yes it does seem improbable but true at least for when I tightened those clips down on mine! 

http://www.backyardastronomy.com/Backyard_Astronomy/Downloads_files/Appendix A-Testing.pdf

 

 

[Steve Ward]

1 hour ago, richyrich_one said:

I already have one of those but it's no longer collimated so it's kind of useless. Be careful with yours, there's no way of recollimating it.

The collimation screws are under the rubber grip ... 

[richyrich_one]

1 hour ago, Steve Ward said:

The collimation screws are under the rubber grip ... 

Thanks. Yes I found the screws but mine wouldn't budge. I would have to try and drill them out. I might give it a go one day.

[richyrich_one]

1 hour ago, Gerry Casa Christiana said:

Trust me it does! Also you want to sort it out because if it is left too long the slight warping can become permanent.

Yes it does seem improbable but true at least for when I tightened those clips down on mine! 

http://www.backyardastronomy.com/Backyard_Astronomy/Downloads_files/Appendix A-Testing.pdf

 

 

eek!

[Steve Ward]

Just Loctited in place , 10 seconds with a soldering iron on the head will melt the Loctite , loosen the grip and free up the screws.

[richyrich_one]

7 minutes ago, Steve Ward said:

Just Loctited in place , 10 seconds with a soldering iron on the head will melt the Loctite , loosen the grip and free up the screws.

I'll try that first, cheers!

[Davey-T]

3 hours ago, richyrich_one said:

I still can't get my head around a half inch thick piece of glass being distorted by a mirror clip but i guess it does.

 

Mirrors don't work as you would think, there was a good explanation in S@N magazine a while ago (may have been AN) apparently the light hits the mirror like a pebble dropping in a puddle it ripples to the edge of the mirror and back so even very small pressure on the edge distorts the image.

At least I think that's what it said from memory 

Dave

[alacant]

Hi. Here's a flat from my camera where the sensor isn't square. It looks very similar to yours. I found out by taking a snap with nothing attached to the camera. Having tried collimaton a million times -yours looks fine- without success, I finally solved the issue. Worth a try? HTH.

[richyrich_one]

3 hours ago, alacant said:

Hi. Here's a flat from my camera where the sensor isn't square. It looks very similar to yours. I found out by taking a snap with nothing attached to the camera. Having tried collimaton a million times -yours looks fine- without success, I finally solved the issue. Worth a try? HTH.

 

I'm eager to know how you solved it...

 

[alacant]

2 minutes ago, richyrich_one said:

I'm eager to know how you solved it...

Get the sensor straightened! For me, that involved sending it back from whence it came. Don't forget to point to a copy of the flat. HTH and have a great 2017.

[richyrich_one]

3 minutes ago, alacant said:

Get the sensor straightened! For me, that involved sending it back from whence it came. Don't forget to point to a copy of the flat. HTH and have a great 2017.

Well I hope that's not the problem having just been modified.

[alacant]

3 minutes ago, richyrich_one said:

I hope that's not the problem

The best way to confirm is to take a flat -on Av with nothing attached to the camera- pointed at an evenly lit white wall. HTH.

[richyrich_one]

2 minutes ago, alacant said:

The best way to confirm is to take a flat -on Av with nothing attached to the camera- pointed at an evenly lit white wall. HTH.

I'll give it a go, thanks.

[richyrich_one]

Alacant

It's starting to look like my sensor is tilted and I'm pretty gutted I have to say.

I hope you don't mind but I'm going to start a new topic just for a sanity check that my method for testing for tilt is sound. I really want to be absolutely sure before I start pointing any fingers.

Thanks very much for the suggestion that this could be the problem, you have saved me a huge amount of time trying to figure it out.

[richyrich_one]

15 hours ago, alacant said:

Get the sensor straightened! For me, that involved sending it back from whence it came. Don't forget to point to a copy of the flat. HTH and have a great 2017.

What do your flats look like now it's been fixed?