Jump to content

Stargazers Lounge Uses Cookies

Like most websites, SGL uses cookies in order to deliver a secure, personalised service, to provide social media functions and to analyse our traffic. Continued use of SGL indicates your acceptance of our cookie policy.


Search the Community

Showing results for tags 'collimation'.

More search options

  • Search By Tags

    Type tags separated by commas.
  • Search By Author

Content Type


  • Welcome
    • Welcome
  • Beginners
    • Getting Started General Help and Advice
    • Getting Started Equipment Help and Advice
    • Getting Started With Observing
    • Getting Started With Imaging
  • Community
    • Official SGL Announcements and Events
    • SGL Challenges and Competitions
    • SGL Star Parties
    • Star Parties & Astro Events
    • Celestial Events Heads Up
    • The Astro Lounge
  • Retailers
    • Sponsor Announcements and Offers
    • FLO Clearance Offers
    • Supplier Reviews
  • Astro Classifieds
    • For Sale / Swap
    • Wanted
  • Equipment
    • Discussions - Scopes / Whole setups
    • Discussions - Binoculars
    • Discussions - Mounts
    • Discussions - Eyepieces
    • Discussions - Cameras
    • Discussions - Software
    • DIY Astronomer
    • DIY Observatories
    • Member Equipment Reviews
  • Observing
  • Video Astronomy
  • Imaging
  • Science
  • WADAS's WADAS Discussion Forum
  • Beaufort Club's Topics
  • Swindon Stargazers Club's Topics
  • East Midlands Stargazers''s Topics
  • Central Scotland Astro's Topics
  • SGL Cumbrian Skies's Topics
  • Herts, Beds and Bucks Group's Topics
  • SGL East Anglian Group's Topics
  • South Leicester Observers's Topics
  • South Wales Group's Topics
  • SGL Surrey Observers's Topics
  • South Yorkshire Stargazers's Topics
  • Yorkshire Astronomers's Topics
  • Devon and Cornwall's Topics
  • West Midlands's Topics
  • Essex Cloud Dodgers's Topics
  • Essex Cloud Dodgers's New equipment
  • NLO and Planetarium's Topics
  • Astronomical Society of Edinburgh's Discussion
  • Leicester Astronomical Society's Topics
  • Dorset Stargazers's Topics
  • Hairy Stars Club (Comets)'s Tutorials and Guides
  • Hairy Stars Club (Comets)'s General Discussion
  • Hairy Stars Club (Comets)'s Observing Campaigns
  • Hairy Stars Club (Comets)'s Analysis results
  • Hairy Stars Club (Comets)'s Useful Links


  • Astro TV
  • Celestial Events
  • SGL Calendar
  • Astro Society Events
  • Star Parties
  • WADAS's Events
  • Beaufort Club's Events
  • Astronomical Society of Edinburgh's Events
  • Leicester Astronomical Society's Events
  • Dorset Stargazers's Events


There are no results to display.

There are no results to display.

Find results in...

Find results that contain...

Date Created

  • Start


Last Updated

  • Start


Filter by number of...


  • Start





Website URL







Found 53 results

  1. Hello everyone, As a farely new member and astronomer, I've decided to seek help for collimation. The task seems pretty daunting at first but I think I got the basics down. Unfortunately I cannot find any answers for the questions I have, so here it is: Is it 'normal' to see the focuser's end? As you can see in the attached picture (poor quality, let me know if I should do another) we can see a rectangle at the left, the focuser. I don't think I should be seeing this and I don't know what causes the problem since the secondary 'seems' to be aligned and the doughnut is dead center. I'm using a XT10 and the focuser is all the way in. Thanks for your precious time, Antoine
  2. Hello Everyone, I have a GSO 6" f/4 Astrograph, and there's always been this issue with elongated stars on one edge. I've checked collimation and it is perfect, but for the elongation on one corner. Could someone please throw some light on what's happening
  3. I have just got a second hand Astromaster 130EQ. I want to say that i have collimated scopes before without the use of a laser but in this case i have 2 questions as this is so far out i cant see what i am looking at half the time. So hopefully you can help, thank you. Info about the first problem: The secondary mirror fixing screw that hold the mirror and the collimation allen key bolts were so loose the secondary mirror had rolled facing the bottom of the OTE. In every other case the holding screw never needed touching and all i had to do were make small adjustments with an allen key, no screwdriver was needed. So this case is a whole different scale then any other collimation i have ever needed to do. You probably all know that i need to get the center of the eyepiece in line with the center of the mirror before can move on with this step. Question 1 What is the best way to do this, shall i just eye it for now? (i have seen people measuring to the center of the eyepiece and then do the same with mirror but then i still dont know if the mirror is facing me directly.) Info about the second problem Every other time i have collimated a scope the mirror and scope were very low quality and just used for practice basically. The old scopes were used to see if i wanted to go further into this hobby which i definitely do. Any how the old scopes had a flat mirror and i could find the center by placing the mirror on paper and tracing a circle template. The thing is this mirror is concaved so any template iswill have to be pushed into the vurve (i think). Question 2 So how can i center the mirror without placing it face down on a piece of paper which cant be a good thing? Thank you. I hope i have not gone on to much, thank you for your patience in reading a long winded post.
  4. Hello! I bought a GSO 2 inch Coma Corrector for my 8inch Newtonian. I'm still having terrible coma on one of the corners which is actually worse than without the coma. The rest of the corners look fine with proper guiding. Here are some details and what I've done to try and solve the issue: 1- Spacing is 75 mm just as recommended. 2- Used a Cheshire, laser collimator, and a webcam to check collimation. 3- Squared the focuser so that it's orthogonal to the optical axis. 4- Tried another DSLR Note that once I collimate and double check that I'm collimated with all the tools, I always try to do a star test and collimation appears off (the dark spot isn't in the middle). Last time I tried to collimate the primary using a star but it's really tough to fine tune since due to the focuser's sag, I can't be sure that the star is in the middle of the fov. My take on the problem is that when I'm using the DSLR with the coma corrector, the weight is moving the focuser away from the center of the optical axis but I'm not sure this if this is the case. I've tried everything and I'm out of ideas. Below is a test image I took for Lagoon Nebula. Notice the coma on the left top side mostly, while the right side usually appear to have no coma (not the case in the attached image though for some reason, but usually the right side is fine). One more thing I've noticed, the stars on the left corner appear to be out of focus while the rest of the image appears well in focus (used a Bahtinov mask with APT bahitnov focus tool) There's also another image I took for a distant light to check collimation (since clouds covered the sky as soon as I decided to do a star test). It appears to be fine and I was able to center it better but didn't capture the image. Please let me know if you have any idea what's causing this. My number one suspect is the focuser's sag preventing me from doing accurate collimation although everything appears to be normal while collimating. I'm giving this another 2 weeks of my time, if it doesn't work I might quit astrophotography till I'm able to afford an APO. One more thing that needs to be added, when using the GSO CC I had to move the primary mirror up the scope by around 2 cm to be able to achieve focus. Clear Skies!
  5. I have encountered a unique problem last night while trying to image using my GSO RC6. The scope is well collimated using a long Cheshire as well as a Howie Glatter single beam laser for verification. CCD inspector also gives me good results when checking with an artificial star. However, when I check using a collimation cap the innermost shadow looks offcentered as well as when I pointed the scope on a real star yesterday (Alp Libra) as well as Spica, it showed a crescent shaped star. This I found to be really weird. Anyone have any idea whats happening here? I live in Bangalore, India, so there's virtually no cool down time required. The temperature gradient between outside and inside is very little if any.
  6. Hi All, I purchased a GSO 6" f/4 Newtonian "Astrograph" late last year and eventually found that stars on one corner were egg shaped while taking images. I narrowed it down to improper centering of secondary mirror from the factory and resulting tilt. Long story short, after numerous iterations, I used the Advanced Newtonian collimation technique by Astro Shed guy and ended up with the below pic of the optics. Does it look ok or do I need to do more? I will be checking with a Howie this weekend too.
  7. Hi. As a response to ebeygin in the whole-scopes section, here's how I insert shims in refractor cells. I stick 6 strips of adhesive tape at 60° from each other. If that's not enough, I add a layer of narrower strips. I forgot to photograph the job I did in the cells, so I'm showing it with a cap. If the layers become too thick I remove those barely visible strips this way: I lift the corner of a strip with the tip of a thin blade, and remove it with tweezers. Its edge remained visible because this strip is narrower than the previous one. 3 strips at 120° don't hold the lens as well, the large empty space between them still allows the lens to play. Plus, 3 strips have to be thicker, to the point the lens drags against them when you want to insert or remove it. 4 strips at 90° don't work too well either. Because of tolerances/inequalities in the lenses edges and (plastic) cell, 6 strips hold better with less pressure. All this is known by frustration experimentation, so trust it. In other shim jobs, I've noticed that 5x72° works well, but only with small circumferences. Worries: - a friend asked if the glue could seep onto the lenses; no, the "glue" on transparent adhesive tape is a solid, like gum, not a liquid, and it doesn't melt at daytime temperatures. I've kept rolls of tranparent tape in a drawer for years, the glue never seeped out. However, don't use electric tape because its glue does flow out with time (also something I know through frustration experience), and it's too thick for accurate centering, anyway. - too much shimming? The inside focus pattern will seem ok, but outside focus the pattern will be an hexagon with rounded edges, the clue that the 6 strips pinch the lens; another thing I learned through shameful blunder experience. Tips: - making the strips narrower has the same effect as removing one or two broad strips, because the friction area is reduced, the lens will enter the cell more smoothly, with less binding. - blacken the lens edges before you shim the cell, because the layer of ink is thick enough to cause binding (another piece of wisdom got from aggravation experience) - the two 80mm scopes I worked on required two layers, and then the removal of one or two strips. It makes the contour a little uneven but you don't care because the lenses have to be centered relative to each other, not relative to the cell. - the first strips have to be about 25mm-30mm long, the next about 10mm shorter Personally I shim only the rear lens, and add centering screws at the front, but locking the rear lens with shims, and tapping the front makes the process less random. Don't forget the alignment marks on the lens edges. Yeaaahh! I finally found how to write between pics!!!
  8. For Sale: Hotech Advanced CT Laser Collimator for 2" Focuser The HoTech Advanced CT Laser Collimator (patented) is a breakthrough in Cassegrain Telescope collimation! Collimate Your Cassegrain Telescope: Without using a star Indoor or outdoor - day or night Focus stays at final view setting Within focal distance from your telescope One-man operation Portable and simple to setup and use Works on CT, SCT, SN Mak, & RC Collimator is in excellent condition having been used on both my SCT scopes. Includes all original parts. Now sold.
  9. Whilst carrying out a star test I have noticed with a friends C8 that one side of focus appears to be collimated and the other side of focus its off, is this a common problem? Is his best option to collimate as an average so its slightly off either side?
  10. Hello all Im just started in imaging and I have to say I'm pleased with the first result BUT on closer inspection I see I have slightly oblong stars. So people know what I've got and done here it is http://www.astrobin.com/full/271950/0/?nc=user I have a baader coma corrector that I'm using set to 55mm from canon sensor and I have tried short exposures and I notice that it's still there in short exposures. Could it be collimation? It's the only thing I didn't do that evening. I would appreciate your input! Thanks Gerry
  11. Hi all, New Skywatcher skyliner 200P, straight out of the box. I thought I would have a go at checking the collimation for the first time. This is a photo taken through the hole in a diy collimation cap. Everything looks ok to me, what do the experts think? The spider vanes look to be crossing smack in the center of the donut on the mirror. Ignore the sparkly thing, it's not a star cluster, 'tis nought but a lamshade :-) Does everything look aligned? Neil.
  12. Hello all! today i had a very brief moment outside with my 150 Mak before the clouds rolled in, between the time i put it out under clear skies and the two hours i gave it to equalize the clouds had rolled in but with some breaks here and there. so during a short break in clouds i picked the brightest star and quickly checked collimation with my 14mm eyepiece, my question is if i should bother to adjust collimation because while im getting a beautifully symmetrical disc with sharp rings on one end of focus, on the other end im getting a disc thats not so symmetrical with a bit of doppler effect going on where concentric rings are compressed a bit more on one end, dealt with this before on my big dob but not sure to what degree it will affect performance in my mak. I remember some saying here that Mak's don't ever need collimation and hold collimation short of a hammer blow to the tube, should bother opening the pandora's box that collimating can be in worst cases? (star was dead centre in FOV of course) Thanks everyone!!
  13. Hi Can anyone help with a collimation problem. I have a 200pds Skywatcher and I am trying to collimate the scope but I am having problems centering the secondary under the focusser. The secondary looks to be circular and positioned correctly to the optical axis but I do not understand how to align it in the axis 90 degrees to this - see photo The mirror is central to the tube on the spider, so the only thing I can think of is that the focusser is not pointing directly at the centre of the tube, so the focusser mounting itself needs adjusting - Is this correct or am I missing something. I have taken a few photos and an example is attached ISO 800 30 seconds. Any help would be greatly appreciated. Pete
  14. Hey guysIm really struggling with an issue. Recently purchased an Orion ST80. At 20x to 44x using stock 20mm/9mm eyepieces stars look pretty good. But if I test it at 175x using 2.3mm eyepiece and point to bright star I get the pattern like in the images below.Will unscrewing the ring and tapping on the side of the tube resettle the lenses? Or is this an alignment/collimation issue that isnt fixed easily? Defocused, the center circle isn't too off the centre..but focused in, it looks like a cone. Really annoying. If I send this back, no guarantees that the next one will be any better. Or is this typical for type of scopeThanks in advance!
  15. I knew from the start, that my Mak (which is new) was a bit out of collimation, I also knew that alhough they hold collimation very well, they can be a pain to collimate. With this in mind I scoured the net for articles and videos before attempting it rather than ending up having a major wobbler when messing it up lol. The key was to understand the push/pull system by which the spider is moved, and very small turns of the screws while adjusting them in sequence with each other. I am happy to say that after 30 minutes, and thanks to Arcturus and a high power eyepiece, I have come as close to perfect as I will get and I am more than happy with that. I took a cell phone shot, I wish it was as sharp and defined as the rings were visually but regardless, it was rewarding. Both inside and outside focus was the same which is great, after snuggling up the locking screws, I won’t be messing with them anymore unless I drop it.
  16. I just got my Glatter (RIP Howie) tublug/laser and holy cow does this thing work! and it makes primary collimation so easy espc for my truss dob. In comparison to the Catseye cheshire it is very close, if not the same. My Catseye triangles seem made for the tublug. I think I'll change the triangles to hotspots down the road though as I heard us collimation fanatics can get a bit more accurate with them. ATM I run all red triangles. Of course I could always pull out the AC
  17. I recently posted about my first successful collimation experience (an SCT). I'm sure we all have our stories, of those moments when we perceived optical clarity. Come on everyone tell us of those collimation 'eureka' moments and your experience of your first observing session immediately following. Paul.
  18. My 10" DOB (f4.7) gave me stunning views of the Orion nebula on a night last week of good seeing. Today I decided to check the collimation The Hotech Lazer collimator showed it to be a fraction off so a little tweak was given.....then I popped the collimation cap on and it looked a bit off.....which is right? Star test when I get to see some on Saturday. Wonder what a big frac would cost.....only joking. Clear skies
  19. Hi all! I bought a set of Bob's Knobs for my Celestron NexStar C8 based upon many recommendations I had read. They have shown up, and the threads on the Bob's Knobs seem to be wider than the threads on the original collimation screws. They don't really want to screw into the scope easily, and I certainly don't want to force anything. Does anybody have experience with this? Should these work for my telescope? The set I bought had the following description: Bob's Knobs Celestron 8" SCT f/10 Collimation Knobs fit Celestron 8" (20cm) f/10 post-1980 SCT with factory silver or Allen Phillips collimation screws, with or without Fastar secondary with silver collimation screws (NexStar 8, Ultima 2000, C8 black, or gray, etc). Please note that this includes post-2000 orange tube but does not fit pre-1980 orange tube or majority of scopes with black Phillips factory collimation screws. Has anybody else had trouble with these? Thanks for any help!
  20. I'm scared I have attained the debilitating Collimation Syndrome ( HClV-1a : Human Collimation Virus strain 1a. - mild/severe). Was out with Calpernia yesterday (ehm..my scope's second name..) and I decided to correct her eyesight..again.. (She's now 11 month's old...her first name is Sky, her surname Watcher, 10" of joy..) I followed my baby's collimation guide (I mean Astrobaby..sorry..) And to my surprise the collicap worked (which I have never tried before) very well... I could see all the six mirror clips on my primary mirror..but it seemed like the clips were not evenly spaced with reference to the side of the secondary mirror's edge. As explained in AstroBaby's guide.. "The photograph to the left shows what the actual view should be like at this stage of the process. Note the three mirror clips are all visible and are all equally close to the edge of the secondary mirror and the secondary is showing round and centred to the focuser tube ( the dark area at the edges of the picture)." (Astrobaby, 19..) source: http://www.astro-baby.com/astro_baby_telescope_help_and_advice.htm. Collimation Guide for Newtonian Reflector Telescopes. I checked with my Cheshire...it showed that (according to the Cheshire) the secondary didn't appear quite cylindrical in the tube. So now I recollimated the whole thing...using my trusted Cheshire...and everything is bang on.. When I insert the colli cap thereafter I can see all the clips, almost all the same size, but still with a slight miscorrection of spacing around the secondary's edge.. Maybe I'm just getting old, and my eyes are tired..
  21. Hi all I have recently acquired a Newtonian reflector 150/750 and I am having a few issues with it. First of all I have read numerous pages on collimation but I don't know what is wrong with this scope. First off I align the secondary with the focuser by eye and using a collimation cap make sure that I can see the 3 primary retaining clips. Then using a Cheshire eyepiece I align everything up as it should be. When I place a good collimated laser in the eyepiece the laser is way off centre on the primary and in actual use stars and planets wont focus and the flare is awful. If I then use the laser to collimate then objects look better but still not great and in this position the secondary holder is leaning away from the focuser and not aligned with the tube. The Cheshire then shows the centre of the primary way off alignment from the circular secondary mirror. Any ideas? Should a laser and a Cheshire agree that a scope is aligned? I will try to load some images tomorrow but its difficult to get what I can see on camera.
  22. I was wonder is someone with the same set-up as me can tell me if this effect is normal for a Celestron 9.25 SCT. I have not had the telescope long so I am still getting used to setting up. I check the collimation before starting each session and have noticed that 2 dark lines are apparent when I have centred the star within its Airy disc. They are like the hands of a clock and quite well defined. Any thought as to what is causing this. I was wondering if the Bob's Knobs are too tight and are causing distortion of the secondary but I cannot find any examples on the internet of this effect to back this idea up. I can't find any reference anywhere to this. Any ideas of what is causing this and how to cure it would be very much appreciated.
  23. I did struggle few years with a colimmation issue in my truss 12" Dob. The collimation would vary unacceptably depending on the angle the dob was. I normally collimate at the begin of each session at 45°. However, at zenith or at low south objects were badly affected by changes in collimation. Temperate was my first suspect but even on night when the temperature didn't swing the collimation was changing. All screws were tightened. This has reduced the changes, but still I had to collimate during the sessions. But I found the reason... heavy 100° eyepieces were bending my Dob's truss. So I have decided to use only my ortho eyepieces with my Dob. Since, the collimation is spot on all night, which only enhances the experience with my orthos. I must say that my dob and my orthos are going to be together forever. Love is in the air.
  24. Hello, A lot of people use the ST80 as their guide scope, or a wide field grab-and-go. I recently purchased one, and after doing star tests at extremely high magnifications, trying to determine, if I'm super picky, or my scope has a flaw in it. With 20mm/9mm (20 - 44x), the bright stars look pretty good, although I wouldn't say they are 100% pinpoint (maybe that's just chromatic abbr). With 2.3mm (176x), bright stars initially had a comet diffraction pattern like this: I corrected that by unscrewing the lens cap, and tapping on the sides of the tube while slowly tightening the cap back. This fixed the comet issue, but now, the stars look like this: If I tighten the cap a bit, I get the comet pattern back. How does this compare with your scopes? I can't get a pin point star at high mag. Am I really picky, since this is a chromatic $100 scope (although people praise it for its high quality) Should this type of scope display perfect pin point stars when using high mag eyepieces? I really don't want to waste time sending this back, if it ends up me being picky, and I get back the same or worse optics. Thanks!
  25. Please help! I have a NEWTONIAN 150 / 750 SKYWATCHER I am seeing crosshairs and a dot even after LASER COLLIMATION! When i look down the focuser empty I can see that secondary is potentially not PERFECTLY aligned, with a slight "moon crecsent" bottom right but upon mounting the laser all spots and targets line up perfectly! I am at my wits end... PLEASE HELP!! What am I doing wrong?
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.