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Help needed! What is this artefact on my image?


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Hi, I just set up my astrophotography mount for the first time and im having an issue. There are these weird artefacts coming up on the images, and a 30 second exposure isnt bringing out any details at all. Is this because of a streetlamp or are my settings wrong? Its a heq5 PRO and Canon 600d.

I've attached images of my APT settings and the image artefacts.

 

settings.JPG

Single__0001_ISO6400_30s__13C.CR2 Single__0003_ISO800_20s__20C.CR2

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Looks to me like your focus is way off & the scope is out of collimation? Here's the first image stretched... Cheers Ivor

The first image looks like very out of focus stars.  Not sure why the circle is flattened at the top, have you got a wind shield on that might be flopping over the light path? Carole  

Hi Your first two images are out of focus and with the telescope out of collimation. The last image shows only hot pixels. Maybe start by collimating the telescope; the secondary mirror is n

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The first image looks like very out of focus stars.  Not sure why the circle is flattened at the top, have you got a wind shield on that might be flopping over the light path?

Carole  

Edited by carastro
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16 minutes ago, carastro said:

The first image looks like very out of focus stars.  Not sure why the circle is flattened at the top, have you got a wind shield on that might be flopping over the light path?

Carole  

No wind shield. I thought the artefacts looked a bit like the mirror in the scope, Am I wrong?

I should note, im also using a coma corrector. How do my settings look in APT?

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10 minutes ago, Aramcheck said:

Looks to me like your focus is way off & the scope is out of collimation?

Here's the first image stretched...

Cheers
Ivor

Single__0001_ISO6400_30s__13C_RGB_VNG.jpg

Thanks a mill. I got rid of that weird thing by adjusting the focuser, but now Im just not seeing any details at all.

Im in a bortle 5 zone. This is a 30 second exposure at the rosette nebula. Any idea why im not seeing anything really?

Single__0016_ISO800_25s__33C.CR2

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An the live view of APT im not really seeing anything either, just the odd star so its quite hard to know if im even in the right spot. I did polar alignment and all and slewed to the nebula and it did slew to that general direction - I jsut dont know how precise. Once I had an image, I was going to use the platesolver to do the alignment for me but it cant work with an image like that. Im at a loss as to why its doing this.

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35 minutes ago, AlanP_ said:

why im not seeing anything

Hi

Your first two images are out of focus and with the telescope out of collimation. The last image shows only hot pixels.

Maybe start by collimating the telescope; the secondary mirror is not centred either in the tube nor in the focuser. (It is however normal to see distortion of out of focus stars when using a coma corrector.) Afterwards, make sure that you are focused on a bright star in live view. Then you should see some stars in a 30s exposure. Stick to ISO800.

Cheers and HTH

Edited by alacant
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Agree with Aramcheck - out of focus and well out of collimation.

What target were you aiming at? If its any sort of nebula it's unlikely you'll see much if anything at all in a live view - especially if the focus is only just slightly off. And the odd stars you're seeing might just be hot pixels. First sort out the ocllimation, then the focus.

Neil

Edited by ngwillym
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20 minutes ago, alacant said:

Hi

Your first two images are out of focus and with the telescope out of collimation. The last image shows only hot pixels.

Maybe start by collimating the telescope; the secondary mirror is not centred either in the tube nor in the focuser. (It is however normal to see distortion of out of focus stars when using a coma corrector.) Afterwards, make sure that you are focused on a bright star in live view. Then you should see some stars in a 30s exposure. Stick to ISO800.

Cheers and HTH

 

18 minutes ago, ngwillym said:

Agree with Aramcheck - out of focus and well out of collimation.

What target were you aiming at? If its any sort of nebula it's unlikely you'll see much if anything at all in a live view - especially if the focus is only just slightly off. And the odd stars you're seeing might just be hot pixels. First sort out the ocllimation, then the focus.

Neil

Cheers guys, I think you may be right. I just wasnt seeing any stars at all int he live view. No matter where I pointed it it looked the same to me. I've just packed t all up for the night and i'll get to collimating it tomorrow. I have a laser collimator, i've just never used it. Hopefully this will fix my problems though!

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1 minute ago, Owmuchonomy said:

What scope is it?  Addition of a coma corrector may have reduced your in focus range considerably.

This is the scope here:https://www.teleskop-express.de/shop/product_info.php/info/p12285_TS-PHOTON-6--F5-Advanced-Newtonian-Telescope-with-metal-tube.html

Yeah it could be that along with it needing to be collimated. Im too nooby to pinpoint it :) 

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1 minute ago, AlanP_ said:

This is the scope here:https://www.teleskop-express.de/shop/product_info.php/info/p12285_TS-PHOTON-6--F5-Advanced-Newtonian-Telescope-with-metal-tube.html

Yeah it could be that along with it needing to be collimated. Im too nooby to pinpoint it :) 

Looking at the spec, I doubt it.  It's an optimised imaging scope so one less thing to worry about.  Get it collimated and then practice focusing on a bright star and imaging that before trying something more challenging.

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15 minutes ago, Owmuchonomy said:

Looking at the spec, I doubt it.  It's an optimised imaging scope so one less thing to worry about.  Get it collimated and then practice focusing on a bright star and imaging that before trying something more challenging.

So this is an exploded view of my setup. First I have the extension tube going into the focuser of my telescope, then the baader coma corrector, then the T2 ring which connects to my camera. The coma corrector says it requires 55mm of spacing to be focused (I think). Is this enough or too much? I dont know how precise it needs to be or where it needs to come from. The second image is it all connected to the telescope. Is this wrong the way I have it? its a brand new telescope so would it be strange for me having to collimate it?

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Ok, wow.

I just collimated it and it was WAY OUT. I have no idea how it was that far out considering this is my first use of it. It's meant to be bright now until 2AM. I may have to get set back up again...

It would be great if someone could fill me in on the coma corrector situation however to clarify if its ok.

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17 minutes ago, AlanP_ said:

the extension tube

This is why you can't reach focus. 

Remove the extension tube and place the coma corrector directly into the focuser.

 

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2 minutes ago, alacant said:

This is why you can't reach focus. 

Remove the extension tube and place the coma corrector directly into the focuser.

 

No wonder! Between that and the terrible collimation it would make sense that I couldn't see anything. 

I may head back out so and get setup!

 

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30 minutes ago, AlanP_ said:

I dont know how precise it needs to be or where it needs to come from

It needs to be 58mm from the shoulder of the m48 thread.

Baader supply an adapter m48-m42 with the corrector which will get you close. See the diagram.

 

Edited by alacant
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10 minutes ago, alacant said:

It needs to be 58mm from the shoulder of the m48 thread.

Baader supply an adapter m48-m42 with the corrector which will get you close. See the diagram.

 

So is what I have now ok?

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Update: Brougt it back outside and set up, but still the same problem. Nothing really visible through the live view and a couple of the exposures had that artefact. I just collimated it too with a laser collimator and had a the red dot centered along with the red dot aligned in the collimator. No idea why this is happening..

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With live view you need only a few seconds exposure to capture enough stars to focus with. If you are very far out of focus then you'll struggle.

My DSLR requires almost full inward travel to find focus. Just 2 or 3mm off hitting the inward limit. That's without the MPCC, can't remember where it lands with the MPCC. Maybe try with and without the MPCC. That is just to fine tune image quality but in some cases can be useful as extra spacing. 

You could pop an eyepiece in and center a brightish star then swap to the camera. Start with the focuser fully wound in and a 2 or 3 second exposure in LV. Wind out the focus very slowly between frames, just a fraction of a turn each time. Using the histogram stretch for this is essential in my experience. Hopefully you'll see the star slowly come to focus as you proceed.  It can take some time to get the feel of focusing, particularly when swapping different elements in/out of the image train.

For the initial focusing exercise I would't worry too much about out of focus star shapes - that is a whole new adventure! :)

 

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9 hours ago, AlanP_ said:

just the camera, t2 ring, coma corrector

Looking good.

Firstly, make sure that the dioptre adjuster on the camera viewfinder allows you to focus the camera using a conventional lens.

Now starting from that -fully inward- position and aimed at something like a tv antenna or distant building, slowly wind out the focuser whilst looking through the camera viewfinder. Stop when you can see an image and tighten the locking screw on the focuser.

Now again looking through the viewfinder, find Capella, Rigel or Sirius. Next... 

... WITHOUT moving the telescope, set APT live view with an exposure at 30s and look for the star. The actual infinity focus position is slightly toward the main tube (inwards) from the position you set terrestrially.

To help nail the focus, you may want to get one of these.

You're nearly there now:)

Edited by alacant
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Had a look at the collimation this morning and it was already out of collimation from when I did it last night. Can it move that easily from taking it off the mount and moving it around? I have it setup now on the mount and im not going to take it off until the next night. I also found a chimney around a mile away and set up the camera with APT connected to the scope. I found the perfect spot for focus and locked it in, so im not going to move that around either. 

Hopeully that was my problem. With the comacorrector, if I move the focus the tiniest amount, it is completely out of focus - so it needs to be extremely precise and I seem to have that down no. 

Fingers crossed thats that sorted now and I can try once more.

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3 hours ago, AlanP_ said:

Can it move that easily from taking it off the mount and moving it around?

Yes. You need to replace the primary mirror springs, fit a proper dovetail plate and tie the top of the rings with a stiff rail. GSO are renowned for bendy cells and tubes;)

Details, here.

Edited by alacant
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9 minutes ago, alacant said:

Yes. You need to replace the primary mirror springs. GSO are renowned for fitting inadequate springs.

Details, here.

Is that a difficult thing to do? I dont want to mess with it too much. 

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