Collimation question 10" DOB

[JayErin]

Hi,

New to it all so thanks in advance.

I just purchased a 10" collapsable dobsonian and I am having an issue seeing the night sky through it. No issue at all it during the day but when I align with a star at night its all blurry and all I see is the spider and a bright image of the star. I have tried adjusting the view but all it seems to do it sharpen the image of the spider and mirror clips. As I mentioned it has no issue with daylight visuals to adjust.

I did take it to the dealer and he double checked it and made a minor adjustment on it during daylight and focused on an image across the road. Same reslult as I had.

Any suggestions? Its crippling me not being able to see anything but an upside down bird in a tree.

J

[Mr Q]

Seeing the spider against the star image sounds like the focus is not adjusted to its sharpest point. Try turning the focuser knob from all the way in to all the way out with a star in the eyepiece. Somewhere within the range of adjustment, the star should focus to a bright pinpoint of light.

Looking at an object across the street will be too close for the scope to focus on, since the scope is designed to focus on things very far away, as stars are.

[JayErin]

I have tried going that route but alas nothing. I am using a 10mm plossl with it I should mention. I dont get any kind of a pinpointed image. I checked the collimation (cheshire) again and everything appears ok. Still all I get is a bright image with nothing but a reflection of the spider. When I adjust it all that is happening is a sharpened image of the spider and less grain/haze in the star object.

I sense a grey hair coming on. Thanks.

J

[DOBBY]

Rack the focuser all the way in...slowly turn it to all the way out...then very slowly while still looking through it..take the eyepiece out ..if you get to focus...you need a small focus extention tube

[Starlight 1]

Do your 10"dob have a 2" extension tube ,If so remove this part and you be ok.

[JayErin]

It does have a 2" ext tube. I will remove it and see if they makes a diff tnight. Just curious..why would that make a diff? Cheers guys and let you know how I make out.

[Starlight 1]

Thay put the 2" ext tube in so when you are useing a 2" eyepiece and some 1.5 eyepiece it save you move the focal length of the telescope.

[Doughzer]

It means the eyepiece is further away than it needs to be.

If you have a 2" extension with a 2 to 1.25" on top, eyepiece is miles away from correct focusing.

I made the mistake myself too ! lol

[Paulb3098]

J, there was a similar post on at 150p, with a picture or two. Might be worth having a quick look ?

http://stargazerslounge.com/beginners-help-advice/181379-spiders-cross-hairs-clouds.html

Good luck Paul

[QldLiz]

I also have a 10" collapsible Dob. and had a similiar problem last year. Wasnt focusing properly, although the collimation was OK, and the problem was that I hadnt fully extended the tubes of the scope - it was only about 10 mm out, but after making sure it was fully extended, all was OK.

[Moonshane]

collimation would never make your scope be out of focus. if extremely bad you might get no image (e.g. if the seconday is pointing the wrong way) but this is not the case for you as you see OK in daylight.

sounds like the replies have it sorted for you - hope it works out.

[JayErin]

I think removing the 2" may do it. Makes sense but I find it odd the telescope guru never made mention. Hoping thats what it is as Ive spent about 6hrs collimating it. Its gutting me knowing whats waiting to be seen. Thanks for your input guys and I will share my result.

-J

[JayErin]

The extra bit was indeed the issue. Bah.. anyway, wicked view of jupiter right now and its moons. Amazing. Also had a quick look at the moon before it ducked away and had a good look at some craters. Gobsmacked really. Never saw this stuff as a kid but I suppose I will appreciate it more now. Cheers fellas. Back to bevies and stars.

-J

J