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When I was starting out, I thought collimation was this really super-complex thing. Then when one of our astronomy club members showed me physically with their scope how to do it, I was surprised at just how simple it was! So I made a video as a basic guide for laser collimating a reflector, in this case a 16'' GSO Dobsonian with a Kendrick laser collimator. Obviously there's a lot involved in collimating and this video is not attempting to cover all those facets. It's intended as a quick explanation of the principle. I found that seeing the basics explained in simple terms without complication was key for me to then use that as a base to learn more. For beginners, there's a fine line between giving enough info to do the process correctly versus information overload. Once you get the basics down, it becomes clear over time the different areas that affect the outcome such as mirror springs, focuser slop, mirror quality, laser misalignment... the list goes on, they all certainly need to be understood but only by getting started and doing can you really learn.

I Bought this GSO Dobsonian 8" as my first telescope, and for my sanity i decided to include a collimation eyepiece (not thr laser one) with the the telescope. For my surprise ( even because a lot of people that i saw on the internet said that "this types of telescope are always collimated after the assemble until arrive at your home") the primary mirror was a little of enter, the secondary i really didn't touched, the primary it looks way better now, at least for me. Anyway, i would really appreciate if you guys could just give me your opinion about it and if it's not good, tell me what can i improve.

Hi, I have just recieved the last item which was on back order for a couple of months from USA. I already had the Infinity Eyepiece but was waiting for the BlackCat. Everything was ordered from FLO and i was very happy with their service. Instead of writing an essay, i made a video of how I use the tools and how they look, but in short - Theese tools are FAR superior to the Howie glatter, even with the Tublug. /Daniel

I'm aiming for the best possible field illumination for my Explore Scientific PN208 f/3.9 imaging newtonian. The scope is 5 years old now and while doing maintenance I wanted to do something about the design flaws as well. With the current secondary holder design it's impossible to center the mirror beneath the focuser. My question is: is this really an issue when the entire primary is visible? I read about optimal field illumination when the secondary is centered, but this isn't achievable with this telescope. I attached an image showing the (very bad aligned and already degrading) secondary at the moment. This is as far down as I can go, I would need to replace the holder screws with longer threads to go further but I don't know if it would make any difference for field illumination? Thanks in advance, Michael

Hi, Just thought I'd share this in case you haven't seen it already. A recent (September 2020) article added to the Celestron 'Knowledge Base' on collimating SCTs. I don't claim to have seen all articles on collimation, but this is defs one of the best that I have seen. https://www.celestron.com/blogs/knowledgebase/sct-edgehd-collimation-guide Siouxsie

Hi folks, I've been seeing tear drop shape stars with the EdgeHd 8 and ZWO ASI294MC Pro camera, so I verified the collimation. I'm using a celestron x0.7 reducer. Does collimation needs to be checked with an eyepiece or with the camera and with or without reducer? I'm asking since I verified my collimation yesterday and couldn't see the concentric rings with the complete imaging train (ASI294MC, OAG, and x0.7 reducer). It was only showing the inner shadow and outer circle. I than replaced the AS294MC with my guide cam (ASI120) which has a much smaller sensor and could see many rings. While, to my view, it seems to be collimated, it's strange that I can't see the rings with the main imaging cam. Any thoughts? Here's how I left the collimation after some adjustments with the guide cam. Kind regards, Jairo

Hi All, I'm brand new to this hobby. I recently purchased a 2nd hand Celestron NexStar 130 SLT. My problem was when attempting to collimate the scope, the 3 small recessed Allan screws on the secondary mirror just wouldn't budge. The alan key would connect with the screw but as I turned it, the spider vanes would flex under the pressure and then the the allan key would pop out of the screw. Now after overdoing it I'm afraid I may have stripped the heads of these small screws as the Allan wrench just gives a tiny bit of resistance. If I have threaded these screws; is there anything I can do, or have I essentially busted my new telescope P.S I've also tried loosening the central Phillips screw but that is also extremely tight... Even trying a electric screwdriver on a low setting. I've just read that celestron advise that you should not touch this at all anyway..

This is an update on the build of the 12.5" cassegrain which amounts to a 2nd light on the built OTA after a slew of changes. Here's what it looks like : Here's a foucaultgram of mirror of the primary I managed to capture . If anyone saw the Pathe news clip released recently of the astronomer putting the mirror on the back of their Newtonian in 1950s, that was the maker of this mirror set! I have re-assembled this telescope having made significant changes to the entire ota. During the summer I have: re-bored the holes in the skeleton frames to ensure alignment of the frame tubes by stacking the frames and re-drilling together. Re-made the mirror support plate with the mirror clips rotated by 30 degrees so they don't interfere with the hexagonal-layout of the truss tube structure In re-making the mirror support plate i have also paid particular attention to keeping the central bored hole concentric with the edges. I have remade the mirror mount skeleton frame. This carries the focuser and the mirror mount plate and they were not sufficiently concentric on the first attempt. The focuser plate now takes 60mm Vixen threaded attachments and specifically the Borg low profile helical focuser. I have finished all the aluminium tube clamps and fitted them to the skeleton frames. They are necessary now as the frames are now loose on the tubes. Re-assembly: I re-assembled the scope frame and mirrors and did first trials in the garage: I used the laser to align the focuser on its independent mount to the centre of the secondary holder. I fitted the secondary mirror, ensuring that the focus point for near objects was a good few inches outside the focuser, having learnt from the first assembly. I collimated using a cheshire eyepiece to ensure that the secondary reflections were concentric before adjusting the primary to re-centre. Basic adjustments completed, I mounted the scope on the observatory mount and re-collimated using the 2" auto-collimator which I find quite sensitive at indicating good secondary concentricity. The reflections of the vanes for the secondary were aligned in one axis but not the other - odd. I did a first view on Vega. It was high at the zenith and bright in the dusk sky. The out of focus rings at 40mm were asymmetric so I adjusted the primary to even them up. It required a lot more adjustment than expected to do. I changed to the 25mm Meade 4000 plossl eyepiece ( mag: 3200/25= x128 ) and nipped up the star image to be concentric either side of focus again using the primary collimation bolts. I find that I can either have the star image condense into the centre of the rings as you approach from either side of focus or you can have good concentric out of focus rings but the star centre moves that tiny but important bit off to the edge of the shrinking ring just as you come to fine focus, but not both. (This I think means something is not quite aligned but I can't see what). I moved to Deneb, for mount alignment purposes. Smack in the middle and no real change in the image due to movement of the OTA. I moved to the central star (Gamma?) and then to beta to view the double. The double was wide open with lovely bright yellow and blue colour but the image was soft. A bit squashed spider even. The legs of the spider wafted as I watched and no amount of focusing would get crystal round stars. I then moved to the double double Eps Lyra. There it was, again, E1 and E2 wide open with clearly discernable doubles but the close doubles were not clean; they were fuzzy, even using the 9mm eyepiece (3200/9 ~ x345) Finally, making use of what dark sky was left in the face of the rising full moon I moved over to M57, M27, M29 which were all relatively large and bright and then closed up, leaving the scope pointed at 10 deg alt and 90 deg az just to catch the dust.. Situation: The focuser works fine. Visual focus needs to be moved to the full extended length of the focuser to enable mounting a DSLR at focus when drawn fully in. So the secondary needs to come towards the primary by about 20/sqrt(M-1). The primary baffle is too long. I need to determine the required length compared to actual. Currently it's 37 cm from the front of the mirror. I cannot see all the secondary from the inside edges of the focuser, or even a little light around the edges. Holding of collimation between slews looks good but the initial collimation change i had to make might be due to the swing from horizontal to vertical - I shall have to look into that and mount the mirror with the tube vertical. Underlying collimation looks flawed. I need to resolve why the vanes aren't symmetric in the reflections ( maybe they aren't mounted symmetrically - is this really something to worry about ?) and also why a auto-collimator collimation had to be adjusted so far on a star. Finally, why does the star collimation do that trick of disppearing into the edge of the rings as I come to fine focus and how do I go about tracking down the cause ? Will that solve my soft and squidgy stars issues ? I should note that the background stars are tight and round more or less to the edge of the field in the 25mm eyepiece and its the brighter stars that are soft and troubling me. Having seen a foucaultgram of the primary which to me looked fine even for such a fast primary (f/2.7), I wonder if its roughness I am seeing in the mirrors. I have no way of testing the secondary other than by making a matching nulling mirror. TBH I can't see that happening. I shall try to collect some video evidence next time, now I have a first view. I shall also try to use the gauge on the helical focuser to judge the symmetry of the out of focus rings on either side of focus for the purpose of spherical aberration measurement and validating that the secondary is at the designed separation. Its about the only means I have for doing this test. Any thoughts and hints on progress gratefully received. Mike