Newton f5 - photo needed

[GiorgioF]

Hello to all.

Could someone help me?
I'm collimating a newton f5 (GSO 150/750) with reego collimator. I'm not exactly clear on the pattern I should see through the small hole in the collimator
Can someone upload a picture, for my better understanding?
Frankly, I'm getting different result with Cheshire and reego....
Many thanks!

[alan potts]

I have moved this as I feel you will get a better response in the scopes section, I left a link as well.

Alan

[Carbon Brush]

Good morning. I have never used this model of laser collimator. Though I have used others.
However, I find myself asking, why use a laser?
First of all for a simple newt, a Cheshire will give good results.
What are the views like after using the Cheshire?
Second. Often laser collimators, when supplied, require collimating.
Do you know that the laser is collimated?

HTH, David.

[Clarkey]

2 hours ago, Carbon Brush said:

I have never used this model of laser collimator

It's not actually a laser, but an LED collimator.

TS 2" Led RC Collimator | First Light Optics

I have just got one for my RC8 (when I am brave enough to collimate it!) I have not used it to collimate my newtonian, but I think the idea for the primary is to get it centred with the centre of the reego - using the red light. If you move the reego out, you should be able to line it up the secondary by keeping the spacing around the outside of the mirror equal all the way round.

To be honest a Cheshire is just as easy - which is what use.

[GiorgioF]

On 19/06/2021 at 09:58, alan potts said:

I have moved this as I feel you will get a better response in the scopes section, I left a link as well.

Alan

Thank you Alan 

Yes, my bad to post in the wrong (not correct) section.

On 19/06/2021 at 13:15, Clarkey said:

It's not actually a laser, but an LED collimator.

TS 2" Led RC Collimator | First Light Optics

I have just got one for my RC8 (when I am brave enough to collimate it!) I have not used it to collimate my newtonian, but I think the idea for the primary is to get it centred with the centre of the reego - using the red light. If you move the reego out, you should be able to line it up the secondary by keeping the spacing around the outside of the mirror equal all the way round.

To be honest a Cheshire is just as easy - which is what use.

Thank you Clarkey for the support.

The reason of willing to use the reego is the capability to check collimation even in the dark without problem.

When I bought it, instructed by vendor I made all concentric (drawtube, secondary and primary) with the view of all the reego clear.

If I check with Cheshire, the image look like an aim target: everything is concentric but this is not in compliance with the literature: being f5, a little offset have to show the reflection of the secondary a little out of centre.

 

Reverse, if I do the collimation with Cheshire and follow all the rules, I can get a good result compared with all images you can see around on the web (photo though the pinhole of Cheshire).

If li check now with reego, I'm unable to see all the reflection of collimator but some part is like cancel(say on the right a kind of black quarter of moon and on the left missing the reego reflection).

 

[Pixies]

Are you able to take a photo of the view? A smartphone camera is usually small enough to get a reasonable picture through the small Cheshire eye-hole.

[GiorgioF]

Here a couple of pictures, on the fly.

For both, primary mirror in low side.

Not the best focus maybe but can assure the cross of Cheshire is spot in the middle of the primary donut sticker and the secondary is perfect in the middle of the drawtube.

The three clips of the PM are visible.

What I can't understand is the reego with the black band in th PM direction 

[Clarkey]

Looking at the image above, it would appear that the secondary mirror needs to be moved up or down the tube (not sure which from the picture) until it is centred in the focuser. It maybe over time that the collimation adjustments have move the mirror slightly in the tube.

[GiorgioF]

To center the secondary I've used a webcam with a 1,25" noose and the small software mire de collimation (french, Sorry for my maybe wrong spelling) over sharpcap liv image. I maybe have done a not perfect photo with mobile phone....

[Clarkey]

I have just checked my Explorer 200p and it looks similar to your photo above. Looking at the secondary mirror on mine I can see it need to be rotated slightly and moved down the tube by loosening the central screw a turn or two then tightening the 3 collimation bolts. Looking at yours I think you just need to loosen or tighten the central screw (and the 3 collimation screws as required) to move the mirror a mm or two up or down in the direction of the arrow. Once the whole mirror position is adjusted relative to the focuser you can re-collimate.

[GiorgioF]

Did you check the 200p with the reego?

I've rechecked my SM but it is right in the center under the drawtube of the focuser.

[bottletopburly]

Most accurate way to check secondary is block off primary and check with a concentre , I was a bit of a doubter using a concentre but after getting used to it it’s very easy to see if secondary is tilted or off centre, in my case my focuser could do with moving towards the primary literally 1 mm  but I’m leaving it as is for now that’s on a 200pds.

Edited June 21, 2021 by bottletopburly

[Clarkey]

6 hours ago, GiorgioF said:

Did you check the 200p with the reego?

Yes. If the primary and secondary mirrors are aligned (as they are from you photo), the only way the reego can be off centre is if the secondary mirror needs to move slightly up or down the tube - or possibly it needs twisting in the holder. From the picture it is impossible to tell the direction of deviation.

[Clarkey]

6 hours ago, GiorgioF said:

Did you check the 200p with the reego?

Yes. If the primary and secondary mirrors are aligned (as they are from you photo), the only way the reego can be off centre is if the secondary mirror needs to move slightly up or down the tube - or possibly it needs twisting in the holder. From the picture it is impossible to tell the direction of deviation.

I have just checked mine and the easiest way to determine which way the mirror is out is to look through the Reego and withdraw it from the drawtube whilst still looking. Then move the Reego slightly and you should be able to get it accurately aligned with the primary, secondary and centralised. The direction you need to move the Reego is the direction the mirror needs returning from. (If the Reego needs to move towards the primary to get aligned and centred, the secondary needs to move the other way). I hope this makes sense. I tried it with mine at it worked perfrectly.

[Clarkey]

OK. I have gone back to my cheshire and laser and this seemed miles out (even though the Reego said everything was spot on). So...

I left the primary and secondary where they were and adjusted the focuser tilt to line up without moving the mirrors. Going back to the Reego after this was marginally out so I recollimated the secondary. With the focuser tilt sorted everything now lines up perfectly - Reego, cheshire and laser. So the culprit for the disagreement between the different methods was the focuser tilt. This is one of the Reego benefits - it will collimate regardless of focuser tilt which is why I got one for my RC8.

So my advice would be get the Reego as close a possible (including moving the secondary as described above). Once this is done you can alter your focuser tilt to get it right.

By the way. Thanks for the post. Without it I would probably not have bothered with the Reego on the Newtonian. Now I have, it highlighted the focuser issue and the scope is now collimated better than it has even been before.👍

[GiorgioF]

I should thank you for the chat.

Tonight I will check the orthogonality of the focuser as last chance and let you know.

 

[Clarkey]

On 22/06/2021 at 10:37, GiorgioF said:

Tonight I will check the orthogonality of the focuser as last chance and let you know.

I was just wondering how you got on? Any progress?