Collimation Issue?

[The-MathMog]

Hey guys. I acquired my first telescope a bit over a month ago, as I've been wanted to own one for a long time now. I've always had a passion for astronomy. So I bought a Celestron Nexstar 130 Slt, which for me seems like a great start, without spending a ton of money. Observing has been great so far at least (a bit of trouble with aligning it, but that is more out of inexperience it seems so far).
I quickly found out that I wanted to try taking some simple photos through it, and got an adapter for an DSLR, which I've been testing out a few nights (still knowing that my mount isn't the most suitable for longer exposures).
After some planetary shots, that seemed decent, I tried aiming it at both the Andromeda galaxy and the Pleiades, and the stars have this weird shape, which doesn't seem to be caused by tracking issues (the image being a 20 second exposure.
It might be a stupid question, but is this an issue with the collimation of the telescope, or is there something else lying behind this effect? It was also quite cold that night, around -4 C, which caused a bit of ice to form on it, hence making me not sure. The attached image shows what I'm talking about, and don't mind the poorly framed Andromeda

Google didn't give me the answers I was looking for, so hopefully you fine people can help a new aspiring "astronomer".

**EDIT** Oh, and it should be in focus too, as I used my homemade bahtinov mask.. But again here the keyword is "Should"

[brantuk]

That looks like the final stage of fine focus on stars in my binoculars. If I was guessing I'd say a dual speed focuser might help to achieve sharp stars - single speed ones are sometimes hard to "lock on" to pin sharp stars. Once the stars are sharp then you'll know you have the best possible focus on M31. I'm sure other folks will offer more ideas. Hth

[The-MathMog]

12 minutes ago, brantuk said:

That looks like the final stage of fine focus on stars in my binoculars. If I was guessing I'd say a dual speed focuser might help to achieve sharp stars - single speed ones are sometimes hard to "lock on" to pin sharp stars. Once the stars are sharp then you'll know you have the best possible focus on M31. I'm sure other folks will offer more ideas. Hth

Well if it indeed is only the focus, then I am glad
I do have noticed that you need to be veeery light on the touch with this focuser, which has been troublesome so far, also the reason why I even made that bahtinov mask. I'll be testing it a bit more tonight then, as the skies seem to be clear again. Those dual speed focusers does really look like a great accessory, but I think I will wait a bit, as they are a bit pricey compared to what I might get out of it at this point ! Thanks for the insight!

For good measure, I will try pointing it at the northstar, and try out a "no-tool" collimation check I just looked up.

[brantuk]

Not saying I'm right - it's just a guess really - but that's what it looks like to me. You could try getting a bit more control on the focuser by wrapping a bunch of wide rubber bands around the focuser knob to enlarge the diameter a bit. The more the merrier. Or try the "Marmite Lid" mod - I'll try find a link to it for you.

Here you go:

 

[barkis]

Do you wear spectacles, if so, you must focus with them on, do not remove them to focus for Imaging, It's OK if you observe 
without them, Your Eyes will accept the focus you get, but a camera lens or sensor won't.
If you wear Bi Focal specs, focus using the distance portion of the lens.
Those Comet like tails on the stars in your Image, look like it is badly focused, and out of collimation too.
 

If you don't use spectacles, you can Ignore much of what I've said above .

[The-MathMog]

22 minutes ago, brantuk said:

Not saying I'm right - it's just a guess really - but that's what it looks like to me. You could try getting a bit more control on the focuser by wrapping a bunch of wide rubber bands around the focuser knob to enlarge the diameter a bit. The more the merrier. Or try the "Marmite Lid" mod - I'll try find a link to it for you.

I'll try either the band or kinda the Marmite one. Only issue there, is that there is not very much space, because of where the focuser is on the scope, and the grooves on it, as very small and tightly packed together, so getting it to grip properly might be interesting. But I'll give it a go! Thanks!

 

13 minutes ago, barkis said:

Do you wear spectacles, if so, you must focus with them on, do not remove them to focus for Imaging, It's OK if you observe 
without them, Your Eyes will accept the focus you get, but a camera lens or sensor won't.
If you wear Bi Focal specs, focus using the distance portion of the lens.
Those Comet like tails on the stars in your Image, look like it is badly focused, and out of collimation too.
 

If you don't use spectacles, you can Ignore much of what I've said above .

Nope, I do not wear spectacles haha

One problem I came across, was that with the oculars and camera I was using, the stars were too dim to see in the live-display on the camera, so I had to take a longer exposure picture between each adjustment of the focus, and then examine the picture. Maybe I didn't do that properly enough when using the bahtinov!
But thanks a lot, both focus and collimation shall be properly checked tonight (or at least somewhat improved)!

[Moonshane]

It looks like poor focus is exacerbating the inherent coma within the scope?

[Peter Drew]

I agree with Moonshane. Apart from being slightly out of focus the stars are exhibiting radial coma which in itself isn't a collimation issue. Was this a direct image through the telescope or was any form of corrector in use?  

[The-MathMog]

33 minutes ago, Peter Drew said:

I agree with Moonshane. Apart from being slightly out of focus the stars are exhibiting radial coma which in itself isn't a collimation issue. Was this a direct image through the telescope or was any form of corrector in use?  

For these I am using a camera adapter that takes eyepieces, so I am viewing it through a 25 mm ocular that came with the scope.

One of these:

https://www.amazon.co.uk/gp/product/B01E6QDL18/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1

[brantuk]

Eyepiece projection photography is always dodgy in my experience - especially with the supplied eyepieces that are usually budget eyepieces - not so good. Did you give any thought to perhaps trying prime focus imaging? I reckon you'd have a lot more success.

[barkis]

I agree the with  above post,  Afocal photography has It's uses,  but not for stars.   Lunar and Planetary work  an benefit from it. 

[Peter Drew]

2 hours ago, The-MathMog said:

For these I am using a camera adapter that takes eyepieces, so I am viewing it through a 25 mm ocular that came with the scope.

One of these:

https://www.amazon.co.uk/gp/product/B01E6QDL18/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1

Thanks for the reply. I would think that it is the eyepiece that is letting the image down. Is the distance from the eyepiece to the camera adjustable? if so, there may be an optimal position to improve the star images.

[The-MathMog]

19 hours ago, brantuk said:

Eyepiece projection photography is always dodgy in my experience - especially with the supplied eyepieces that are usually budget eyepieces - not so good. Did you give any thought to perhaps trying prime focus imaging? I reckon you'd have a lot more success.

Ahh alright, very good to know guys.. I just expected that method to work all around, since I did also get decent results from taking pictures of the moon, venus, jupiter etc..!
I have played a bit with the thought of running it prime. A problem there is, that the 1.25 inch adapter/focuser is not a low profile one, so from what I've heard, the camera is going to have a hard time getting close enough to the secondary mirror to get in focus, without either moving the primary mirror, or removing some pretty necessary parts.

 

17 hours ago, Peter Drew said:

Thanks for the reply. I would think that it is the eyepiece that is letting the image down. Is the distance from the eyepiece to the camera adjustable? if so, there may be an optimal position to improve the star images.

Yeah, the position of the eyepiece is adjustable, so I might try to give that a go too, to see if I can find a "sweet-spot". It would be lovely if I could get some decent photos with the setup, as I quite like the zoom of it
 
I am looking to buy a medium tier ocular set too soon, with some Plössl eye pieces, barlow lens, a moon and a planetary color filter. Maybe some combination with any of that can be of use with the dslr.

I did try taking some pictures last night too. I adjusted the collimation a bit, and I used your advice and made a homemade "jamlid" focuser  It sure works wonders for those small focus adjustments. It was a bit more improvised, using duct-tape and superglue, because of those small grooves. 

 

[spillage]

if you focus knobs are held in place with a screw you can undo the screw and then use a 6" piece of wood drill a hole through one end for the the new longer screw to hold it in place. Or you can use a wooden clothes peg instead. This will allow you to remove it completely or just undo it slightly to adjust the rotation. Although it may be that you focus knobs are glued in place.

[John]

36 minutes ago, The-MathMog said:

Ahh alright, very good to know guys.. I just expected that method to work all around, since I did also get decent results from taking pictures of the moon, venus, jupiter etc..!

I guess these targets would have been more or less at the centre of the field of view ?

It's away from the centre, off the optical axis where aberrations tend to become noticable.