Bottletopburly Posted June 12, 2021 Share Posted June 12, 2021 So tweaking the 200pds which seems to be taking ages due to cloud cover , last outing still not happy with stars with the baader cc , which I think may be a case of pinched primary, so yesterday I removed the aperture mask and primary clips and stuck primary to holder with a few blobs of sealent , reset collimation now using the concentre is shows the secondary slightly off may equate to 1-2mm so the focuser needs to move towards primary is this going to matter for imaging ? or is it worth tweaking focuser , I’ve ordered a black shower cap to cut out any light leak on primary end of ota , and I have cc spacing at 58.1mm which is within the tolerance of 57.5 +\- 1mm so hopefully tonight I can check it out , starting to do my head in ,so fingers crossed 🤞. Link to comment Share on other sites More sharing options...
+Graham Posted June 12, 2021 Share Posted June 12, 2021 David Be careful with the secondary. Not a lot of people know this but the secondary is supposed to be off set. I did have the calculation around here somewhere but you can find it on the amateur telescope making sites. Link to comment Share on other sites More sharing options...
Bottletopburly Posted June 12, 2021 Author Share Posted June 12, 2021 8 minutes ago, Graham said: David Be careful with the secondary. Not a lot of people know this but the secondary is supposed to be off set. I did have the calculation around here somewhere but you can find it on the amateur telescope making sites. Apparently the concentre eyepiece allows for this graham which basically is an eyepiece with circle etchings on Perspex , you look at the secondary and how it aligns to the circle etching , reading on the concentre apparently it’s the most accurate device to collimate a secondary with , it’s took me a while to get used to but once you block the primary off it all makes sense and is easier to use and understand. Link to comment Share on other sites More sharing options...
+Graham Posted June 12, 2021 Share Posted June 12, 2021 (edited) Not familiar with this tool David. Looking at it in a totally engineering prospective. The one thing that concerns me is if the circles on the ep are offset to allow for the secondary mirror offset how do you know when the ep is correctly rotated to the central axis. If the ep is not correctly fitted the offset could be anywhere up to 180 degrees out. My second point of concern is the secondary mirror offset changes with the size of the scope so how can a single tool allow for this. Edited June 12, 2021 by Graham Link to comment Share on other sites More sharing options...
Bottletopburly Posted June 12, 2021 Author Share Posted June 12, 2021 7 minutes ago, Graham said: Not familiar with this tool David. Looking at it in a totally engineering prospective. The one thing that concerns me is if the circles on the ep are offset to allow for the secondary mirror offset how do you know when the ep is correctly rotated to the central axis. If the ep is not correctly fitted the offset could be anywhere up to 180 degrees out. My second point of concern is the secondary mirror offset changes with the size of the scope so how can a single tool allow for this. https://www.teleskop-express.de/shop/product_info.php/language/en/info/p5506_TS-Optics-Concenter-2--Collimation-Eyepiece-for-Newtonian-Telescopes.html if you’d like a look graham by all means I can get it to you , Link to comment Share on other sites More sharing options...
+Graham Posted June 12, 2021 Share Posted June 12, 2021 (edited) Thankfully I don't use Newts If I do have to collimate one I use a Howie Glatter. You might like to read this as it explains a lot and dispels many myths on this subject. www.deepskywatch.com/Articles/replace-offset-collimate-secondary.html Edited June 12, 2021 by Graham Link to comment Share on other sites More sharing options...
Bottletopburly Posted June 12, 2021 Author Share Posted June 12, 2021 11 minutes ago, Graham said: Thankfully I don't use Newts If I do have to collimate one I use a Howie Glatter. You might like to read this as it explains a lot and dispels many myths on this subject. www.deepskywatch.com/Articles/replace-offset-collimate-secondary.html I read that earlier funnily enough 👍 I think all’s looking good re collimation from my 52 year old eyes 👀 crossed referencing with Cheshire and colli cap , laser (turning it in the holder to allow for it being out slightly) all seem to point in the same direction, Neighbors must think what in earths he doing 😆. Link to comment Share on other sites More sharing options...
+Graham Posted June 12, 2021 Share Posted June 12, 2021 Sounds good. Rather you than me Dave collimating scopes can get to be obsessive to say the least. Link to comment Share on other sites More sharing options...
+Bino-viewer Posted June 12, 2021 Share Posted June 12, 2021 I'm detecting a severe case of OCD.... (Obsessive Collimation Disorder) 😉 +RonC and Bottletopburly 2 Link to comment Share on other sites More sharing options...
Bottletopburly Posted June 12, 2021 Author Share Posted June 12, 2021 14 minutes ago, Bino-viewer said: I'm detecting a severe case of OCD.... (Obsessive Collimation Disorder) 😉 You may be right rob 😂 Link to comment Share on other sites More sharing options...
Bottletopburly Posted June 13, 2021 Author Share Posted June 13, 2021 Had a session last night, looking better though guiding was poor though sharpcap said Pa was good though may be down to picking m16 low down atmosphere, will try again with a higher target 🎯 eggy stars looked like pa error 1.30 rms rather than coma , we shall see . Link to comment Share on other sites More sharing options...
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