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Showing results for tags 'primary mirror'.
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So, I have gone and got myself a Skywatcher Star Discovery 150p, which has so far proved to be a very good little scope and I've had some very good results. I have now got the bug for imaging and have gone out and got myself a second hand Nikon D5100 and verious other equipment needed to do this, only to now find I can't get Prime Focus!!!!!!!! So the only way I can image is using a barlow x2 which obviously changes the F ratio from F5.5 to F11 slowing everything x2 this isn't to bad for planetary imaging but for DSO images not so good!!! After searching through lots of videos on to do this all I can find is...... I can either butcher the standard rack and pinion focuser that's fitted on it by cutting it down and rethreading it or by moving the primary up by 20-25mm, which seems a shame to do a brand new scope still under warranty! The only other option I have come up with is changing the focuser to a Skywatcher Low Profile Dual Speed Focuser For Newtonian Reflectors. Could anyone out there shed any light on this before I spend another £130 on the new focuser. Thanks
Have you ever thought about why your Newton telescope has the dimension it has, primary and secondary mirror, focuser, f/number and so on? I stumbled in to this tool Newt-Web that Kenneth H. Slater has developed further from Dale Keller's code. It's an online design tool page for Newton telescope. It's a very intuitive page where you can put in some figures about a Newton telescope that you want to built and get back information about it's performance. It give a ray trace and important data back. From that you get understanding when a Newton telescope design is good or not. I have done some test and written it down on my homepage so you can see the different steps and my comments: http://astrofriend.eu/astronomy/projects/project-design-newton-telescope/project-design-newton-telescope.html I already know some of the physics and math, but never got to know so much in short time what happens when you change a parameter and what happens inside the telescope. Beware, I'm still in the learning process and not all what I have written is fully correct. I recommend you to take a look at Newt-Web page even if you never will built a telescope, you get knowledge and understanding that could be very valuable when you shall buy a Newton telescope. /Lars
I was having a little inspection of my dob primary mirror the other day and came across something I'm looking for advice about. While shining a light at it and looking at a certain angle, I could see lots of little specs on the mirror. At first I thought it may be dust even though I always keep the tube cap on. So I very gently pumped some air against it using a modified and clean bicycle pump but nothing cleared. After that, all I can describe them as are either imperfections on the mirror, very tiny scratches or stubbornly settled dust. What makes it particularly strange is when looking directly down at the mirror or at different angles they do not appear. So I'm just wondering if anyone here knows what these marks are, and if they are completely normal or something to be worried about. I couldn't get very good pictures but I have attached the best one highlighting the marks (even though they're not really identical...)