How to use a cheshire collimating eyepiece

[legoalan]

Can anyone teach me how to use a collimating eyepiece please? What I've done is slotted the whole collimator into the eyepiece tube and through a tiny hole I can see a crosshair. Do I just aim the crosshair at the middle of the mirror or something?

Thanks

[legoalan]

Also what is the hole on the side for? Am I suppose to look into it?

[jgs001]

Point the objective at a bright wall, put the cheshire into the eyepiece tube. Align the hole in the top so that a light shines down into the large hole and look into the small hole. The only instructions I have for it are for collimating my RC, but they give an idea... the details for your scope may be different...

http://www.astronomics.com/main/documents/astro%20tech/astro-tech%20at6rc%20collimation%20sheet.pdf

[Bizibilder]

Probably the most comprehensive and easy to follow collimation instructions can be found here:

Astro Babys Guide to Collimation

by Astro Baby.

[Si W]

Did you get a manual with your scope ?, most of them come with instructions specific to that scope and how to collimate it.

[legoalan]

Thanks for the guide biz

I read the manual and it doesnt contain anything to do with collimation but I think I know which screws are the ones to adjust the mirror

[jgs001]

be very slow and careful in the adjustments... I spend ages chasing the collimation in a circle around and around the central axis of the scope and collimator till I got, just how small the needed adjustments were... at one point I thought I was never going to get it...

[Bizibilder]

Collimating is like riding a bike - total confusion followed by an amazing sense of achievement!! First time may take a while - after that its a five (maybe ten) minute job.

[tms48]

Astro Babys guide is what I used but dependant on the length of your cheshire when fully inserted you may not be able to see all of the secondary mirror to centre it. This was my problem and when I withdrew the cheshire enought to see the complete secondary mirror it was moving around slightly in the holder. I wrapped it in plumbers tape to get a good neat fit no problem from then on.

[AstroB]

I collimated my telescope for the first time yesterday, and I found it quite easy thanks to this video

Hope it can help you too, I always find it easier to watch someone do it before I do it myself.

[Stardaze]

Holy thread revival again! But I've just broken my collimating virginity. Wasn't too bad, once you get your head around it. I guess the proof of the pudding will be tonight.... watch this space!

It's a good job I'm practising on my little starter scope, before the 'upgrade' turns up (next week with a slice of Lady Luck) 

[John]

The scope can be a bit out of collimation and still show decent images. It's when you start trying to observe things towards the edge of the scopes capabilities that having really accurate collimation matters more. Splitting tight double stars, trying to see finer lunar and planetary details, that sort of thing.

 

[Stardaze]

13 minutes ago, John said:

The scope can be a bit out of collimation and still show decent images. It's when you start trying to observe things towards the edge of the scopes capabilities that having really accurate collimation matters more. Splitting tight double stars, trying to see finer lunar and planetary details, that sort of thing.

 

I tried a star test last night quickly - I haven't been looking for problems until my Cheshire was delivered, and last time I looked it didn't look too bad - but there were light clouds around and it pretty much looked like the typical atmospheric depiction I've seen. It looked way out when I tested it all earlier. Managed to snaffle an old film canister and made that up to use for the secondary mirror, which was a bit better for that than the Cheshire. 

[Stardaze]

On 24/04/2020 at 16:28, John said:

The scope can be a bit out of collimation and still show decent images. It's when you start trying to observe things towards the edge of the scopes capabilities that having really accurate collimation matters more. Splitting tight double stars, trying to see finer lunar and planetary details, that sort of thing.

 

What's your preferred tool of choice for collimating John? Wondering whether a laser is better Han a Cheshire for the secondary?

[John]

1 hour ago, Stardaze said:

What's your preferred tool of choice for collimating John? Wondering whether a laser is better Han a Cheshire for the secondary?

I use a simple cheshire eyepiece. I have had a few laser collimators and still have one. Having got so used to the cheshire view now that is by far my most often used tool. My secondary rarely needs adjustment and the primary just the occasional tweak so it's not a challenging scope to maintain.

 

[Stardaze]

2 minutes ago, John said:

I use a simple cheshire eyepiece. I have had a few laser collimators and still have one. Having got so used to the cheshire view now that is by far my most often used tool. My secondary rarely needs adjustment and the primary just the occasional tweak so it's not a challenging scope to maintain.

 

Does the secondary drift a bit over time then? Just the general alignment of the clips? 

[JOC]

Follow the Astrobaby guide linked to above literally to the letter and you will achieve collimation - no-one was more scared of undoing those screws than me, but it's sort of as you do it you suddenly gain an understanding of what you are achieving and why and it then it all seems much less a 'black art' and much more do-able.

[LightTouch]

Hi, 

I've just received my cheshire (short one), I have a silly question pls.... when I look through the tiny whole.. (just the tool itself - no telescope) those 2 cross wires, they don't look centred .. hope the tool itself is fine.. I've attached an image is this normal? I don't want to use a tool that is not "calibrated" I'm such a noob

Thanks!

 

Edited April 29, 2020 by LightTouch

[Trikeflyer]

Probably best to measure them to check. You are right, they don’t look centred but it’s tricky to judge with camera angles etc. Either use a ruler or draw a circle on some card, that’s the same diameter as the end of the tube where the wires are mounted and with the centre marked on the card, check if it lines up with where the wires cross.

Steve 

[LightTouch]

thanks, from the back it looks ok, from the front it might be the angle I look through, I'm going to measure them on the paper like you suggested

[jonathan]

Just a quick question...  Would you collimate with a Cheshire outside on a cloudy day?  I don't have many bright walls inside the house and there isn't enough distance for an artificial star (we have small, dimly lit rooms... old house thing).

Also, does scope vibration matter?  I could plonk my 8" SCT on my CG-4, it's overweight but if the mount isn't tracking then it shouldn't matter.

[Pixies]

6 minutes ago, jonathan said:

Just a quick question...  Would you collimate with a Cheshire outside on a cloudy day?  I don't have many bright walls inside the house and there isn't enough distance for an artificial star (we have small, dimly lit rooms... old house thing).

Also, does scope vibration matter?  I could plonk my 8" SCT on my CG-4, it's overweight but if the mount isn't tracking then it shouldn't matter.

Outside in clouds is great (daylight obvs  )

If the mount can hold it still, it'll be fine. You could even place the scope on a pillow on a table.

[wookie1965]

You can do it in the dark just shine a red torch at the shiny part on the Cheshire very easy. 

[Pixies]

5 minutes ago, wookie1965 said:

You can do it in the dark just shine a red torch at the shiny part on the Cheshire very easy. 

I was going to say about using a cheshire as a sight-tube to align the secondary under the focuser. But Jonathan is talking about an SCT. I'm confused now!

Don't get me started on the FLO 'premium' cheshire. I'll be doing a review later. There is an issue with the red torch approach!

[wookie1965]

8 minutes ago, Pixies said:

I was going to say about using a cheshire as a sight-tube to align the secondary under the focuser. But Jonathan is talking about an SCT. I'm confused now!

Don't get me started on the FLO 'premium' cheshire. I'll be doing a review later. There is an issue with the red torch approach!

I had a Cheshire sight tube not the "premium" and not from FLO worked really well on my 8" reflector after I had flocked it. I gave it to the bloke I sold the scope to.