Advice wanted please after a frustrating night imaging!

[Astronut1982]

Hey all, after a bit of advice if you don't mind.

I got out last night & finally had a chance to try out all my new gear. I am impressed with it all as I did see the improvment that it could make if everything is set correctly but I didn't get any usable subs due what I am assuming is a collimating issue.

I tried to collimate last night with my new hotech laser collimator exactly as a couple of guys from my observing group had shown me the last night we were all out together. I got the red dot in the centre of the doughnut on the primary & then using the adjusting bolts on the back of the scope (after slackening off the locking bolts) I moved the laser so it was going back through the hole on the collimator itself. I then tightened the locking bolts up, checking the laser again to make sure I hadn't moved it whilst tightening but it was perfect. After that I went to start imaging but as I was adjusting the focus with my bahtinov mask I couldn't get a perfect circle as shown in the pic included.

This got me pretty frustrated & annoyed as I'm positive I did everything right, so if anyone has idea as to what the issue is then please feel free to pass on any advice, i'd really appreciate it.

Cheers in advance,

Jeff

P.S. As I was typing this, a thought occured to me that it could have something to do with my spider vanes as I see that it is only 1 quarter of the image that is affected & that is the only thing I can think of split into 4. Could that possibly be the reason?

[steppenwolf]

It would be really useful to see a similar image of an out of focus star but without the Bahtinov mask on the front of the scope.

[Tinker1947]

I would think your focusing is well out , try to focus on a star then place the mask over the scope and you should see 6 points of light, not the mask its self....

[steppenwolf]

Just to be clear, is your original image intended to show an out of focus star (this is how do a star test) although we wouldn't do it with a Bahtinov mask in place or is this an image of what you believe to be an in focus star? If this is intended to show an in focus star then as already stated, it is well out of focus.

[brantuk]

This is not the view you would see with a properly focussed bhatinov mask - what you would see is more like a squashed star with six diffraction spikes like the one at the top right of this article:

http://www.zodiaclig...ahtinovMask.htm

The photo in your post above looks like the secondary isn't squared up to the focuser tube. It should appear perfectly circular in the focus tube when set right. Then you collimate the primary using the hotech after that. Hope that helps

[Scott]

i also thought the secondary was out as brantuk has said but being a noob i didn't want to say something that might have been wrong and cause confusion. i've read and used brantuks advice many times since joining this forum and its always helpful.

Scott

[brantuk]

Thanks for the kind words Scott - I'm glad my comments have been helpful to you

[Astronut1982]

It is supposed to be out of focus & I just forgot to take the mask off when i took the pic, it was late, I was frustrated & I just had a brain fart!

What I was trying to highlight was that the star isn't a perfect circle which is what I had expected to see. I aligned the scope the way I was shown so I'm positive I've done that right but it still doesn't look right at all. I have a bash at making sure the secondary is squared up to the focuser tube.

Cheers

Jeff

[boabsta]

I think I would redo or at least check collimation fisrt dude. Pic looks a wee bit flat on one quarter.

I would maybe start by checking the secondary position incase it has rotated.

[Astronut1982]

Well I followed all the astronomy shed videos & I think I have it sussed. If the skies are tonight I'll do a star test on it & will find out for sure.

Jeff

[Scott]

Well I followed all the astronomy shed videos & I think I have it sussed. If the skies are tonight I'll do a star test on it & will find out for sure.

Jeff

glad to hear youve got it sussed. its so frustrating when things don't go to plan but also very rewarding when the problems are sorted

scott