Collimation and Star-hopping

[sophiecentaur]

On the topic of finding stuff, I have had some problems. My binoculars seems to work well with star hopping even just waving around until the wanted object comes into view. I have then found a problem using the finder scope (90 degree right way up) or my camera to locate the object. I have just acquired a green laser pointer and that actually seems to do the business reliably. I have used it fixed on a tripod and adjusted it to point at what I can see in the binoculars and them it's easy to find the green beam (and hence the wanted object) in the finder scope. 

I know there can be problems with passing aircraft but it only takes a minute to do the procedure and the risk is very small as I am looking at the sky when it's on. What are the views of other members? It seems a very reliable method.

[Moonshane]

Reasonably okay if used safely on your own but won't make many friends at star parties!

[popeye85]

great read! thanks for that. Have you got any additional tips for anyone ( by anyone I mean me) that doesn't have a finder scope but uses a telrad alone? I know most people use both but cant afford to (be caught..) spending any more on the scope for a good while yet.

[John]

1 hour ago, popeye85 said:

great read! thanks for that. Have you got any additional tips for anyone ( by anyone I mean me) that doesn't have a finder scope but uses a telrad alone? I know most people use both but cant afford to (be caught..) spending any more on the scope for a good while yet.

I used to use just a Telrad / Red dot finder.

With a Telrad it's very useful to have a star chart and to make an acetate overlay with the 4, 2 and .5 degree circles of the Telrad marked on it. You can then overlay that onto the star field where your target lies and get a good idea of reasonably bright stars that you can position within the Telrad rings and note where your target object will be in relation to them.

 

[Chadnich13]

On Tuesday, October 22, 2013 at 05:24, Moonshane said:

I don't profess to be either an expert or an expert speaker but was asked to do a couple of talks at the Peak Star Party recently.

I have attached below my written handout notes for each session in the hope they will help the odd person with how to find objects in the sky and also how to ensure you get the best views when you do find them. These notes are based on my own experience and also information gleaned from many sources since I started observing; thanks to anyone who recognises their work or comments.

If one person finds them useful then I'll be delighted and it's been worth the minor effort uploading them. They have been put into a couple of other threads but I felt they were somewhat hidden and might be more easily located here.

Cheers

Shane

Locating Objects in the Night Sky.pdf

Collimation of Newtonian Telescopes-1.pdf

 

This post has been promoted to an article

 

Just wanted to say thank you very much! Downloaded both pdfs and looking forward to getting the star atlas for future sessions. 

[JOC]

I got given a laser collimator for Crimbo and have read the guide in the OP as the instructions with the collimating device seemed a bit frightening.  The instructions in the OP are well written and understandable, but I still don't like the sound of shift screws around and potentially remove mirrors etc. that every set of instructions seems to come with.  Things like checking the distance on the vanes I can probably cope with, but anything that refers to doing any job with mirrors etc. fills me with dread that I could never get them back into place again.

[Moonshane]

If you can adjust it wrong you (or a friend) can adjust It right. Just don't drop anything

[JOC]

Hi Moonshane, I'm sure that would be the case, but I don't have any friends and certainly haven't an inkling of anyone with telescope knowledge.  In terms of not dropping anything (in partic. that secondary mirror) is there anything on a telescope with are likely to be very shallowly screw threaded?

[Moonshane]

The main danger Is the central bolt but this might not even need adjustment.  The other is dropping your Allen key but work other than vertical and you'll be fine

[Chefgage]

I have a skyliner 200p telescope. Just got myself a chesire to collimate. Could all you knowledgable people have a look at my before and after pictures to see if you think it is now collimated.

 

 

[Moonshane]

Looks pretty good to me. It won't make any difference you'd see but the secondary looks like it needs rotating so the black offset points down toward the primary.

See the pic below.

Your focuser would be at the bottom

[Chefgage]

Hi thanks for that. Could you explain what you mean by 'the black offset points towards the primary'

[Chefgage]

I think i know what you mean now. Are you refering to the dark ring that surrounds the smaller white circle with a dot in it. From my picture the black lone part that sticks out appears to point slightly down. Does this point to the right i.e. pointing towards the primary

[Moonshane]

Spot on ! 

[Chefgage]

The next thing is figuring out how to do that. You said it will not effect the viewing so is it really necessary? 

I will still have a go though (i like learning :))

I have one central screw which i understand alters the distance of the secondary mirror to the primary thus enabling you to center the secondary in the focuser.

I then have three allen screws to alternthe tilt of the secondary mirror.

So what do I have to rotate the mirror?

[Moonshane]

You'd need to back off the three little bolts a little and then rotate. Then collimate the secondary again with those same screws after checking the secondary in round and centred again. In other words, redo the collimation. You honestly wont notice any difference but in my experience it's worth doing as once set you probably won't ever change it again in all likelihood

 

[JOC]

Chefgage I have the equivalent of your 200P and have just tentatively completed my first collimation.  I was advised to google and follow Astro baby's collimation guide - if you Google just that you will find the PDF.  In places it's slightly misaligned text wise, but in this finish and having gone through all your problems this (and a Cheshire collimator) is what I succeeded with.  Before I followed it I watched several videos of people collimating their telescope with both lasers and cheshires.  Although they use a laser this first one will give you the confidence to move the mirrors

 There are fewer videos out there that use a Cheshire, but Astro baby's guide detailed it well for me - including how to use sheets of paper (I used old coloured envelopes) stuffed in various places to make things easier.  I had both a laser and a Cheshire - I had previously failed with the laser, but I got the Cheshire and found that when I started to follow Astro baby's guide it all started to make sense.  The three black notches on the dark grey circle in the diagram above are the three holders for the primary mirror.  I found with my basic Cheshire that they are only just (and I mean only just) visble in the Cheshire view when they aligned - if you see one more than the others its not quite right, but you will see what I mean if you follow the guide.  The other advantage in finding it is that she is describing a 200P in the guide.  It did take me about 1.5 hours and it is fairly frustrating when things move as you tighten them, but once I got the hang of it (and I was dead scared when my secondary went all floppy!) the guide made everything plain sailing and it all made sense when I realised what I was looking at I cannot recommend following it to the letter highly enough.  The key is keeping the secondary as a perfect circle as you work on from that point, but you will see that as you follow the instructions and I did go back and check that point a couple of times.  My finished collimation looked identical to her pictures of what she called a perfectly collimation telescope, even down the slightly offset she describes for our type of telescope.  FWIW I was chuffed beyond belief with what the guide let me accomplish and I used a Cheshire to do this.  NB.  I used and continue to use my laser for a quick day to day check, but the Cheshire would be just as quick 

Edited April 3, 2017 by JOC

[Chefgage]

^ I used a combination of the guide posted in this thread, astro babys guide and another guide    I found.  Its a straight forward process i can see, its just knowing what screws do what.

I will have another go at some point, but like what has been said will  I notice any difference.

[JOC]

10 minutes ago, Chefgage said:

will  I notice any difference

I'm still waiting for clear skies and a repaired telescope (my mount has to go back for adjustment) to find that out myself LOL!

[Chefgage]

Well I certainly think collimating my skyliner 200p has made a big difference. I went out last night, seeing conditions weren't that great as the moon was out and not many stars were visible. I could even nearly read my star charts by moon light!

Decided to try and have a good look at Jupiter as last time I looked at Jupiter was before the collimating. This time I could see a lot more detail but it was still a bit 'hazy' - anyone else see it as a bit hazy? But what I did see that amazed me was Io transiting Jupiter.  Saw a black dot about half way across the planet, a quick look at an app on my phone confirmed what I was seeing, so very happy with last nights viewing.

[Arcturus D]

Excellent collimation is needed for objects like the planets in order to increase contrast. For most DSOs you can get away with a rough collimation.

[25585]

For people using star charts alongside refractors, cats & casses,  unless the chart layout is specific to a certain type of view (for example Sarna is for Newtonians, showing south on top ), I consider correct image diagonals a great boon, albeit necessity for beginners at least.

Terrestial adapters such as the Vixen one https://global.vixen.co.jp/en/product/3847_09/ can also give correct images.

 

 

Edited June 29, 2018 by 25585

[Lowen22]

Thanks, this is exactly what I needed.

Edited September 4, 2018 by Lowen22

[popeye85]

Video guide to help anyone struggling with star hopping.

 

 

[RouxM]

Thanks Shane 👍