Startest / Secondary offset help

[Rush]

Dear stargazers,

did a star test with an 8 " Quattro / F4 which reveals a peculiar shaped Dfocused star. Is this normal cos of the secondary.m offset  or am i pushing the 2ndry too much towards the primary ?

I washed the secondary and added a milk bottle washer to see if it makes any difference. It was looking much worse, so i put it all back n the original state.

This is how it looks like now.  Sweet astrobaby tipps was a huge help, still i m unable to decide where to start.  Need ur help, thank you all n advance,

CS

Rush

 

[astrosathya]

You "Washed" the secondary? Why would you do that? 

I too have an f4 telescope and I would recommend you get proper collimation tools for this one.

You need:

a) Cheshire Eyepiece of the long variety

b) A Lser collimator (if its a cheap one you need to collimate it 1st), preferably a Howie Glatter or

c) If you have the money, get a Catseye Triplepack XLKP collimation set.

Read a lot about collimation. Its really important to know the techniques.

[Rush]

6 hours ago, astrosathya said:

You "Washed" the secondary? Why would you do that? 

I too have an f4 telescope and I would recommend you get proper collimation tools for this one.

You need:

a) Cheshire Eyepiece of the long variety

b) A Lser collimator (if its a cheap one you need to collimate it 1st), preferably a Howie Glatter or

c) If you have the money, get a Catseye Triplepack XLKP collimation set.

Read a lot about collimation. Its really important to know the techniques.

 

 

Thanx much 4 the advice,

Unfortunatley this aint  helping me?. Need something more specific.  its collimated  but the positioning  of the secondary probably s incorrect , dont know. Laser spots and collimation cap view doesnt show anything unusall.

CS

Rush

[Rush]

6 hours ago, astrosathya said:

You "Washed" the secondary? Why would you do that?  Yes, was foggy  with dust particles sticking from the dew menace. Primary nedd too warm bath sooner ot later.

I too have an f4 telescope and I would recommend you get proper collimation tools for this one.  Well, i have collimation tools in my astro Arsenal, i can handle collimating.

You need:

a) Cheshire Eyepiece of the long variety

b) A Lser collimator (if its a cheap one you need to collimate it 1st), preferably a Howie Glatter or

c) If you have the money, get a Catseye Triplepack XLKP collimation set.

Read a lot about collimation. Its really important to know the techniques. Im trying and learning these days each time  i come into contact with an astro Gadget. couldnt find this symptom in Google wisdom pages. ?

 

[Rush]

Thank u all great guys who came forward to help me sort out this problem on the parallel thread titled Need Collimating.  You are all wonderful and this makes SGL a freindly astronomy forum. 

Cheers 

Cs

Rush

[alacant]

On 28/03/2019 at 12:39, Rush said:

i have collimation tools in my astro Arsenal

Hi. OK, that's good. You collimate a f4 just as you would any other Newtonian.

We don't know where your star images are in the FOV, whether they were taken with a coma corrector or what the optical train looks like via a Cheshire sight tube, preferably with cross hairs. If you can post those details along with a single frame of a star field in focus we should be able to help a lot more.

Cheers and good luck.

[Geoff Barnes]

I would think the oval appearance of the secondary indicates it needs slightly turning until you have a perfect circle in the eyepiece. You may then have to adjust the outer screws a bit but basically should be right.

[Rush]

On 30/03/2019 at 21:20, alacant said:

Hi. OK, that's good. You collimate a f4 just as you would any other Newtonian.

We don't know where your star images are in the FOV, whether they were taken with a coma corrector or what the optical train looks like via a Cheshire sight tube, preferably with cross hairs. If you can post those details along with a single frame of a star field in focus we should be able to help a lot more.

Cheers and good luck.

Hi,

thanx 4 ur help, much appreciated.

Sorry 4 the late reply, was away 4 weekend. Well, I started from the scratch again, made  secondary circular, and primary fully from beginning. Since i never used a Cheshire ST. I had to order by TS.

must be on the way. Meanwhile i did all that i could with a Colli cap and Barlowed laser.

looks like this, view through the D.tube.

Primary doughnut centered with Barlowed laser beam

Img. train with a SW F4 aplanatic C.corrector and IDAS LP filter. Attached is a Lum stkd test image. is this getting somewhere decent? ?, thanx much,  CS  Rush.

[alacant]

8 hours ago, Rush said:

is this getting somewhere decent?

Hi Yeah, of course it is. You went out and took an image rather than read about collimation theory!

8 hours ago, Rush said:

D.tube.

?

According to myriad Internet articles, the secondary should be centre field. Yours is displaced way down the tube toward the primary but hey, you produced a perfectly good image despite the f4 horror stories.

It will be interesting to see the view through your sight tube when it arrives. Meanwhile, keep going with the imaging.

Cheers and clear skies:)

 

[Rush]

On 03/04/2019 at 08:16, alacant said:

Hi Yeah, of course it is. You went out and took an image rather than read about collimation theory!

?

According to myriad Internet articles, the secondary should be centre field. Yours is displaced way down the tube toward the primary but hey, you produced a perfectly good image despite the f4 horror stories.

It will be interesting to see the view through your sight tube when it arrives. Meanwhile, keep going with the imaging.

Cheers and clear skies:)

 

 

Hi,

? D. tube = Draw tube,of eypiece holder.

You are right .the real test is under the night sky.?

Well , finally the hour of truth has come. i.e the Cheshire CT from TS with CONCENTER tool test. Everything i left untouched from previous tweaking (laser show)

And here s the View through Cheshire CT. Is this OK ?  True the secondary is quiet out of center, cos of the offset may be ?. this s kind of weird b cos that offset makes me want to tweak again , no matter its postioned right or not?.

Through Concenter tool, Wonder if i ever will get those  rings aligned with primary to secondary and vice versa cos of the offset ?

 

An an image after the previous laser tweak. The halo around the bright star is gleaming . Primary edges need tuning ? paint it rough black ? Next adventure ? Thanx much CS,

Rush

2 hrs L and 1 hr RGB with the prvious laser tweak test. Bright star core light streaks around. Sorry if its dirty crude processed , red gradient kill next time after serious extrem imaging:)

 

[alacant]

On 28/03/2019 at 12:39, Rush said:

 

Hi. No. The secondary is not positioned correctly so you're losing light. You don't indicate the orientation (in which direction is the primary) of your photos so were still guessing but I'd say that the secondary needs either moving away from or toward the primary. Simply look through the drawtube with your eye roughly centred. Move the secondary into the centre of the circle you see. 

Take a photo with nothing in the drawtube with your camera pointing at the secondary.

Nearly there.

[Rush]

2 hours ago, alacant said:

Hi. No. The secondary is not positioned correctly so you're losing light. You don't indicate the orientation (in which direction is the primary) of your photos so were still guessing but I'd say that the secondary needs either moving away from or toward the primary. Simply look through the drawtube with your eye roughly centred. Move the secondary into the centre of the circle you see. 

Take a photo with nothing in the drawtube with your camera pointing at the secondary.

Nearly there.

Yes, primary is to the left and the dark corner is bottom of secondary (right) towards the opening of scope.

 

Nearly there.

Huh, great soothing words, muchas gracias.  Im on the spiral ladder to the stars:)

 

[alacant]

8 hours ago, Rush said:

muchas gracias

De nada:)

Yeah, it's clear now what you need to do.

According to the orientation of the image you posted, the secondary needs moving upwards to make it concentric with the larger circle -corresponding to the bottom of the drawtube- which you see. It then needs twisting anti-clockwise -as viewed from the open end of the tube- so as to reflect the primary evenly. Do that and post back. Try to snap the whole of the secondary this time. ATM the Cheshire sight tube isn't going to help you as you'0re too far off collimation.

HTH.

**But hey, it's a 30 second job from where you have it. Would it be possible to get someone to call around and do it for you the first time? Once you've seen it done, it is very easy but almost impossible to describe!

[Rush]

 

17 hours ago, alacant said:

 

HTH.

**But hey, it's a 30 second job from where you have it. Would it be possible to get someone to call around and do it for you the first time? Once you've seen it done, it is very easy but almost impossible to describe!

tried to keep it under 29 seconds ? .

After twist & turn , secondoryl looks like this.

Bvor twist and turn

You r very much right, im almost there. if the first image looks fine ,  ready  to continue with  the primary .  cheers.

 

[alacant]

6 hours ago, Rush said:

under 29 seconds

That's the spirit!

 Well done. That's it. You're there; slight clockwise secondary rotation and that's it.

If you're imaging, you may want to stick in the Cheshire sight tube -if it has cross-hairs even easier- and get the primary donut centered in the field of view.

You have 20 seconds, starting..... NOW.

**tip: replace the three secondary adjusting hex-allen grub screws with longer m4 bolts; Using a nut tightened up against the head it makes secondary tewaking easier.

[Rush]

Hi,

Thanx a million 4 the help and tips.

Couldnt continue during the weekend.

20 seconds gone with the wind.?, can I repeat  with a delay ??

Do have a Cheshire now with X hairs.

Hex_ Allen replaced with Bobs -Knobs.

tmw i will start the final tweaking again .

How does it really look like fully tweaked through a Cheshire. ? Something like this,

Horrible Image , Sorry