Which collimation is right. Apertura ad12 collimation question

[Nissanrob88]

I'm not exactly new to telescopes, I bought my first scope almost 3 years ago. I have a apertura ad12 dobsonian. Collimation wasn't hard to figure out when I first got it, after not using the scope for a year I forgot a lot of what I learned.  Included 2 photos one is off set one is not. With f5 scopes they say off set but others say no.  I did star test both way and there the same . As for the views I get everything seems slightly off and not as clear as when I first got it. I'm not sure if I'm doing something wrong of even if I'm collimating properly. Curious what you guys think. Side note my Cheshire tube and cap don't always line up. Sometimes they do and even then the views seem weird. Main issue everything blurry above 150 to 200x.  That could just be bad seeing or thermal issues..... This year sems bad for seeing even stars directly above have a slight twinkle to them. I'm front new Jersey if that matters.

I love this scope and it's amazing. Even with extremely bad light pollution I have seen Andromeda  and its satellite galaxy. The ring nebula was cool along with a few others. There is another 2 galaxies I seen and 4 more nebula along with ngc but cannot remember names. I know some are going to say so what's the big deal you can see that with a smaller scope. The big deal is light pollution. I have 4 led street lights around My house . Also a small used car dealership that has 25 bright led lights on all the time. There is also a shopping center 8 blocks away and industrial area 1/2 mile away and another mall 2 Miles away. I have glow all around me . The sky above me always has a faint glow. Still my favorite was finding out Saturn has bands like Jupiter. That was really cool to see. 

[Carbon Brush]

Hello and welcome to SGL.

I don't know this particular scope. But if the price tag I saw online is reliable, I'm expecting Skywatcher dob type of build quality.

From your description of the awful light pollution, it is probably worth putting effort into improving off axis light from interfering with your viewing.

Flocking the tube is a good first move. Are there any bright parts around the focus tube - a common build error cost saving.
Is the mirror cell open, allowing stray light?
Edge blackening glass?
Good quality eyepieces will help with contrast.

I think the above measures wil help , then clear up whether you really do have collimation issues.

HTH, David.

[Nissanrob88]

I included a image of scope. Its a lott bigger then I thought and was a little excessive for a first scope. After awhile I realized it's worth every penny and a good choice.I lve always had a interest in the stars so I decided to make it a late Christmas gift to my self. It does cost over a grand but we'll worth it, the Quality is good as well haven't had a single issue with or complaint. Even the Eyepieces aren't half bad especially the 30mm inch. .I have light coming in from few directions, it sometimes hits the focuser and back if secondary mirror. Usually it's the far side of tube that gets most of the light.

[Giles_B]

I have a year less experience with telescopes than you, and there are limits to what can be seen in a picture taken down the focuser barrel, but the collimation looks okay to me - in the second picture all three mirror clips aren't visible, but I think this is due to the angle the photo is taken at. I'd expect the image of to be offset in an f5 scope. Hopefully wiser heads will also weigh in here.

When you say "everything" gets blurry at 150-200x do you mean planets? or stars and DSOs as well? - I have a 10" Dob under city skies and about 11m above sea level - and 200x is the limit on planetary magnification on average - exceptionally I'll get a clear image up to 400x, but that is unusual.

My personal experience, after a lot of fussing about my own collimation, is that the seeing usually the limiting factor, not poor collimation.

[Spile]

If the focus tube is at ten o’clock then your secondary looks good to me. See step 2 of https://astro.catshill.com/collimation-guide/. A piece of coloured paper behind the focuser (see the guide) will help. For the secondary alignment use your Cheshire eyepiece and sight tube combination tool. Once that is sorted use the cap to check your primary.

Edited November 15, 2022 by Spile

[Nissanrob88]

I figured out my springs for adjusting the primary and locking are worn out. For a year I didn't use scope and left them under tension the whole time.  Any movement will cause it to come out of collimation. Even when the scope is just sitting it loses collimation after 10 min. I should of payed more attention and loosened everything when I knew I wasn't go to use for awhile. I already replaced them with upgrade ones from a kit I got awhile back. Tonight I'll take it out and see what happens. This explains why everything is blurry and why I thought my collimation was off or I did something wrong. I also ordered flocking to help with light in tube and a external baffle for the light coming from sides.

[skybadger]

Leaving springs under tension doesn't cause them to change over time, otherwise your car suspension would collapse .

Have they corroded significantly or been over-tightened ? I have several telescopes with very old springs whic have held their collimation for years, so I don't understand why the springs are at fault.