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Old 31-12-2016, 03:21 PM
diegocolonnello's Avatar
diegocolonnello (Diego)
Breathing Stars

diegocolonnello is offline
 
Join Date: Sep 2016
Location: melbourne, australia
Posts: 307
Collimating a triplet Refractor

I have got an explore scientific ED80 refractor, this thing is a beauty, triplet apo that promises good views and photos.......... but....

I found this second hand on a really good condition........... after testing it, i noticed weird looking stars:

https://3.bp.blogspot.com/-Lotg5LMLe...00/apotest.jpg

I don't know anything about refractors but this doesn't look right for an APO...

so i decided to take it apart and find what is going on....
Checked that everything was in place and that the focuser is properly alligned to the Lens cell...... so, what happens?

I found a manual from Explore Scientific where they instruct the user on how to collimate their telescope, it happens that the second and third objectives have radial centering screws..... easy, use a high power eyepiece and look for the shape of the airy discs and done, adjust and ready to go....

it doesn't work that way, looking at the airy discs its hard, it moves and its too small, i can't tell if the center is ok or off.......

Tried to look for info on google and NADA........ people collimates Newts and checks focuser alingment on refractors but nothing on triplet lens centering.......

I came up with the idea of installing my ZWO 034MC camera to the scope and use an artificial star ..... after trying to get an image centered on my scope, it worked......... and saw this on SharpCap...

https://1.bp.blogspot.com/-Pn-SKVujG...228_235648.jpg

Clearly i can see the discs are not centered and maybe this is the cause of my problem....... RADIAL CENTERING

Started to try and adjust the screws and at last i found out i could see what i was doing, but it was too late to continue....

Maybe i am bananas trying to collimate a triplet, but i am getting close...

Episode 2...

Again, lets try.....

Installed the little beauty on my eq5 mount, started the mount and installed the artificial star across the house, all the way to the kitchen, after 10 minutes i had the star on my FOV and started tweaking the image for gain, contrast and exposures to get the best i could....

After trying and moving the objectives i learned what moves where and the effect it has on the image,,,,,,,

got it all the way to this...

https://2.bp.blogspot.com/-r6n7EhnIZ...231_010001.jpg

Looks better live on my screen, i think it has to be really close to be good..... thing is every time you move the second lens, it moves the star across the FOV, then you have to center it again using the mount keypad and keep going................ untill it looks fine...

This is what pinched optics looks like...

https://1.bp.blogspot.com/-DPV2kFJ3i...231_013137.jpg

those 3 hills on the circle are the result of over tight setting screws....

This is a part of SHARPCAP that i consider interesting, it lets you separate LIVE the color channels....

https://2.bp.blogspot.com/-pxc0TLnQs...231_011710.jpg

This lets you set up an offset on each channel and that way you know if one or two channels are in need of more adjustment......

I hope this helps someone, i will be posting my resulting images from this scope.............. WEATHER..... PLEASE, LET ME PLAY WITH IT>>>>

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