star-test pics for reflector's..

[asimov]

http://www.willbell.com/tm/IMAGES/StarTest1.jpg

<BIG>:thumbsup: </BIG>

[RAJAH235]

That last one's sort of what mine looks like.... :D L.

[vindictive666]

cool pics


all i need now is a very very very simple way of getting my scope to match the last row of pics :) :) (ive saved the page for reference :) )

when i look at the double (rigel kentaurus) i see the middle top picture ? on both stars, the same on the single pointer star :)

:ashamed:

[RAJAH235]

What instrument? The refractor or the bino's???? :D
The DOB should give a pinpoint star with your 4 thin spider spikes. L.
1.

[vindictive666]

sorry i forgot to add it was seeing thru my dob :)

[slice of heaven]

Have you checked for pinched mirrors Vin?

[vindictive666]

yes i ripped them out a while back the secondary as well, no problems :) apart from the foam at the back of the secondary that wa putting a bit of pressure on the secondary but fixed that by trimming it. :)

[slice of heaven]

I've never had the problem so I cant offer a solution for that one, hopefully someone knows a fix for it. As Laurie posted you should have pinpoint stars and the brighter ones will show the diffraction spikes.

[ving]

time to test my optics again :)
thnx for the pix! :D

[elusiver]

thanks asimov.. just a quick question though.. maybe a dumb question.. is it better to use a high power or low power eyepiece when star testing? or doesn't it matter?

thanks
el :)

[ving]

high... I use my 9mm

[elusiver]

cool ving.. ohh yeah.. i can print this page out on my colour laser :) :D :D score!


el :)

[asimov]

Well, first proceedure I use is yep, a 9mm on a bright star, de-focus out, adjust primary. de-focus in, collimate further (collimation seems slightly different each side of focus for some reason..If it looks perfect outside of focus, then when I de-focus in, it usually looks slighty out..I then get it looking perfect on in-focus.) then move on to a star not as bright, preferably at the zenith or close to it. bung in 5 mm EP. collimate primary out side focus...then inside focus...then at perfect focus, using the airy disc to fine tune the collimation IE: concentric rings around airy disk...fine tune until airy disk is dead centre of concentric rings around it. All this to be done after thermal equalibrium is achieved naturally. But seeing the temp usually keeps dropping at night, you have to keep tweaking the collimation usually.

[slice of heaven]

I'd like to add to that John

Check the ep you use by rotating it in the focuser to ensure theres no problem with the ep. Use a good ep.
If your using a barlow same thing, check its of good quality.
Crank up the mag as much as you can, for good alignment you need the central rings well defined. I'd use more than a 9mm.
I use around a mag 3 star for 2 reasons, theres enough of them and the brighter stars dont give as much contrast between rings.
Nights of seeing where you can pick obvious faults with optics are common enough.
Nights of seeing that are good enough to allow very fine tuning arent that common, so I avoid having the scope bumped/knocked and treat it with care. Also make sure the mirror supports/holders are capable of holding collimation well.

Startesting is a good tool for picking faults with optics including collimation.
As the name implies ,its a 'test' to check how your optics perform and how your collimation techniques stand up.

[asimov]

Good 'add to' Slice!.....Tring to add a thumbs up smilie here, but it's not working??

[slice of heaven]

Heres a link to a program where you can enter your scopes stats and then alter the image to show how different problems affect the image.
I've played with it but never had a use for it.

http://aberrator.astronomy.net/index.html

[asimov]

Now that's interesting Slice! TY for that.