38 replies to this topic

[Altair03]

I have a Celestron Astromaster 130eq, and i feel my scope needs to be collimated because at one point Jupiter looks crescent suddenly.

And then i collimated it following various guide on the internet, i still haven't been able to get a nice picture like before, i can't focus on Saturn while before that i can capture it normally with decent details. I can only take the photo of the moon because somehow it doesn't bothered by the misalignment. I attach the photo of my mirror looked down the focusee tube in this topi, pls desperately need help

[Altair03]

Here is the photo of my mirrors taken from the focusee tube. Is there any mistake? Thank you very much for any input...

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Edited by Altair03, 30 September 2023 - 09:19 AM.

[kgb]

It does appear that your collimation is off, but it is hard to say definitively because your camera would need to be positioned in the exact center and would need to be perfectly perpendicular to the focal plain. Do you own a cheshire and have you reviewed the collimation threads that are pinned in the reflector forum?

[Vic Menard]

Here is the photo of my mirrors taken from the focusee tube. Is there any mistake? Thank you very much for any input...

First, "Welcome to Cloudy Nights!"

 

As kgb has already noted, It's hard to say anything definitively about your collimation unless your image is taken through a collimation tool. If you don't have a collimating tool, the inexpensive Rigel Aline is ideal for this application  https://www.rigelsys.com/telecoll.html

 

I can't see the primary mirror center marker/donut on your primary mirror in the image you provided, so I've annotated three circles with cross hairs: 

the bottom edge of the focuser (outermost light blue circle),

the reflected edge of the primary mirror (red circle), and

the reflected edge of the underside of the focuser (yellow circle).

 

You need to adjust the secondary mirror to center the reflection of the primary mirror (red circle) relative to the focuser (light blue circle). After you have reflection of the primary mirror centered, you can then adjust the primary mirror tilt to center the reflection of the underside of the focuser (yellow circle) in the primary mirror. These two axial alignments deliver image performance. 

 

Getting the secondary mirror (green circle) centered relative to the bottom edge of the focuser and the reflected edge of the primary mirror is a bit more complicated--so we'll save that for later. Right now, you need to focus on the axial alignments. (Note that, when the light blue, green, red and yellow circles are concentric, the reflection of the secondary mirror (violet circle) will NOT be concentric, but will appear offset toward the primary mirror end of the tube assembly.

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[Altair03]

It does appear that your collimation is off, but it is hard to say definitively because your camera would need to be positioned in the exact center and would need to be perfectly perpendicular to the focal plain. Do you own a cheshire and have you reviewed the collimation threads that are pinned in the reflector forum?

I only have a homemade collimation cap made from the telescope dustcap, it's a bit hard to find a good astronomy store in my country, and the price can be quite high eventhough it's not the best product.

[Altair03]

First, "Welcome to Cloudy Nights!"

 

As kgb has already noted, It's hard to say anything definitively about your collimation unless your image is taken through a collimation tool. If you don't have a collimating tool, the inexpensive Rigel Aline is ideal for this application  https://www.rigelsys.com/telecoll.html

 

I can't see the primary mirror center marker/donut on your primary mirror in the image you provided, so I've annotated three circles with cross hairs: 

the bottom edge of the focuser (outermost light blue circle),

the reflected edge of the primary mirror (red circle), and

the reflected edge of the underside of the focuser (yellow circle).

 

You need to adjust the secondary mirror to center the reflection of the primary mirror (red circle) relative to the focuser (light blue circle). After you have reflection of the primary mirror centered, you can then adjust the primary mirror tilt to center the reflection of the underside of the focuser (yellow circle) in the primary mirror. These two axial alignments deliver image performance. 

 

Getting the secondary mirror (green circle) centered relative to the bottom edge of the focuser and the reflected edge of the primary mirror is a bit more complicated--so we'll save that for later. Right now, you need to focus on the axial alignments. (Note that, when the light blue, green, red and yellow circles are concentric, the reflection of the secondary mirror (violet circle) will NOT be concentric, but will appear offset toward the primary mirror end of the tube assembly.

Okay, i'll try your suggestion tomorrow morning. Thank you so much for the input

 

And yes, my scope doesnt have the donut mark, i just use an approximate measurement when i did the centering before.

 

I'll give you an update of the progress, thank you very much all

[Vic Menard]

This is what your circles should look like:

 

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[Vic Menard]

I only have a homemade collimation cap made from the telescope dustcap, it's a bit hard to find a good astronomy store in my country, and the price can be quite high eventhough it's not the best product.

Have you tried here?

 

https://www.firstlig...mation-cap.html

[Altair03]

Thank you so much for the input guys, i'll definitely try it first for now and i'll be posting about the update and progress. This is my first reflector, before i only use a refractor telescope so i still have so muxh to learn about this collimation.

 

I've read some thread on this forum about collimation, but there are different approaches and it's so hard to find which one suitable for me. Besides i learn better from watching others, that's why i prefer youtube, but youtube apparently has fewer good collimation tips unfortunately

[Altair03]

This is what your circles should look like:

 

Have you tried here?

 

https://www.firstlig...mation-cap.html

I've browsed the website before, but i don't want to risk buying directly from overseas unless they open their store at the marketplace in my country. There are too many red tapes to taken care of, and the end-price and tax can be higher than the actual price

[kgb]

You can make your own Cheshire.

If you have access to a 3D printer you can obtain instructions and files here: https://stargazerslo...shire-eyepiece/

If not, you can try these DIY instructions:
http://www.graphiteg...i?a=diycheshire

[mrlovt]

Thank you so much for the input guys, i'll definitely try it first for now and i'll be posting about the update and progress. This is my first reflector, before i only use a refractor telescope so i still have so muxh to learn about this collimation.

 

I've read some thread on this forum about collimation, but there are different approaches and it's so hard to find which one suitable for me. Besides i learn better from watching others, that's why i prefer youtube, but youtube apparently has fewer good collimation tips unfortunately

This one might be helpful:  https://www.youtube....?v=KkX_MHpqozE   He covers collimating a newtonian pretty well. 

[Altair03]

This is what your circles should look like:

Hello Vic, i'm so sorry to bother you again, but i've redone the collimation according to your diagram, using this homemade collimation cap. I attached the result taken through the cap. In my opinion i've aligned the mirrors correctly. What do you think?

 

I can't test it on anything because it's raining today

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[Altair03]

This one might be helpful:  https://www.youtube....?v=KkX_MHpqozE   He covers collimating a newtonian pretty well. 

Thank you, i've watched the video and it helped a lot

[SkyDays]

Hello Altair03!  I thought I would add something as a beginner myself .......  Collimation can be very time consuming, confusing, and frustrating your first couple of tries at it.  Don't let it discourage you from the hobby or your telescope .... your experience so far is very normal!  Once you figure everything out and have it collimated, you will feel like a CHAMPION!  Hang in there until then, it is worth the effort and part of the learning in the hobby. -Steve

[Starman1]

A collimation cap tutorial is attached.

Also, you won't be able to collimate properly without a small donut on the primary mirror.

 

Attached Files

•  Aline Instructions.docx   29.79KB   16 downloads

[Vic Menard]

Hello Vic, i'm so sorry to bother you again, but i've redone the collimation according to your diagram, using this homemade collimation cap. I attached the result taken through the cap. In my opinion i've aligned the mirrors correctly. What do you think?

I can't see the bottom edge of the focuser, so I can't tell if you've sorted out the secondary mirror tilt. Your primary mirror is spherical, so it's important to try to align the three circles I noted in post #4.

[Altair03]

Hello Altair03!  I thought I would add something as a beginner myself .......  Collimation can be very time consuming, confusing, and frustrating your first couple of tries at it.  Don't let it discourage you from the hobby or your telescope .... your experience so far is very normal!  Once you figure everything out and have it collimated, you will feel like a CHAMPION!  Hang in there until then, it is worth the effort and part of the learning in the hobby. -Steve

Thank you Steve, i won't give up on this ofc

[Altair03]

A collimation cap tutorial is attached.

Also, you won't be able to collimate properly without a small donut on the primary mirror

I'm not brave enough to open the primary mirror's compartment, but maybe i'll try. For now i'm searching for the suitable material for the donut.

[Altair03]

I can't see the bottom edge of the focuser, so I can't tell if you've sorted out the secondary mirror tilt. Your primary mirror is spherical, so it's important to try to align the three circles I noted in post #4.

Do you mean that circle?

 

Actually i'm a bit confused, bcs i saw that circle then i remember your diagram, but when i tried moving the secondary upward, the primary reflection becomes an eclipse, not a full circle anymore. That's why i thought that circle is just a reflection from the light and my phone camera, and the focuser's end has already aligned with the secondary.

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[Starman1]

I'm not brave enough to open the primary mirror's compartment, but maybe i'll try. For now i'm searching for the suitable material for the donut.

Use a white or yellow paper punched hole reinforcement ring, like this:

https://www.amazon.c...la-817558866932

Your dark pupil through the collimation cap will appear as a black dot in the center of the hole.

Edited by Starman1, 01 October 2023 - 02:27 PM.

[Vic Menard]

1.) Do you mean that circle?

2.) Actually i'm a bit confused, bcs i saw that circle then i remember your diagram, but when i tried moving the secondary upward, the primary reflection becomes an eclipse, not a full circle anymore.

3.) That's why i thought that circle is just a reflection from the light and my phone camera, and the focuser's end has already aligned with the secondary.

1.) I've attached your annotated image.

2.) The secondary mirror needs to move upward (tilt) and then rotated to recenter the reflection of the primary mirror. 

3.) The outermost blue circle is the bottom edge of the focuser drawtube. You can see the secondary mirror (green circle with green lines) cut off at the edge.

 

A primary mirror center marker/donut will help, as will a decent collimating tool (or tools) depending on what you can find. Is there an astronomy club in your area?

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[Vic Menard]

You'll know your secondary mirror tilt is correct (or close) when the dark crescent (red arrow) disappears.

 

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[Altair03]

1.) I've attached your annotated image.

2.) The secondary mirror needs to move upward (tilt) and then rotated to recenter the reflection of the primary mirror. 

3.) The outermost blue circle is the bottom edge of the focuser drawtube. You can see the secondary mirror (green circle with green lines) cut off at the edge.

 

A primary mirror center marker/donut will help, as will a decent collimating tool (or tools) depending on what you can find. Is there an astronomy club in your area?

Ah i see, so rotating is not moving the reflection upward, but recentering it. I'll try it again when i have free time :')

 

Btw there's no astronomy club in my area, astronomy is not a popular hobby here

[Altair03]

Use a white or yellow paper punched hole reinforcement ring, like this:

https://www.amazon.c...la-817558866932

Your dark pupil through the collimation cap will appear as a black dot in the center of the hole.

Okay, i'll try look for one here thank you