Trouble imaging on an unguided NEQ6 mount

[Hughesy94]

Hi guys,

Im relatively new to the AP scene, and i was having trouble the other night whilst trying to image Jupiter. I was getting trails of the planet and moons, even on very short exposures (1/500) using an astromodded Canon 100d. Ive imaged Jupiter before and not had this problem, so in the end i gave up and tried to look at my polar alignment to see if thats the issue, i havent had a chance to image since so il have to come back to it and see if that helps, but even before i wasnt really getting anything over a minute unguided without star trails when imaging M51, is this normal or should i be expecting more? I was under the assumption that with a motorised mount like the eq6 i could expect to get a good few minutes before i lose it?  

the kit im using is as follows;

Canon 100d astromodded

Skywatcher 150PDS

Old model NEQ6 GOTO mount 

 

Which brings me to my next question, i want to get an autoguider, but im relatively new/skint so i dont want to spend a huge amount on one, just something to increase my tracking so i can get longer exposures and eventually i will upgrade. Ive read countless threads/reviews and it seems everyone has a different opinion, but the two that have stood out thus far are the Orion Magnificent mini package and the ZWO ASI120 either MC or MM, unsure on the benefits or draw backs of having colour if im going to shoot with a DSLR anyway. Are these fairly good for a beginner using the kit i already have, or would anybody recommend a different guider/path? Sorry for the essay!

[carastro]

You should have a SW finderscope on the 150PDS (I hope), you can convert that with an adapter in the back to hold a guide camera.  I would check which cameras are suitable for this i.e. there is an adapter made for the finderscope that will fit the camera, FLO will probably know.  

I only have experience with the QHY5 range of guide cameras and these definitely fit the finderscope.  The adapter I recall was around £25 plus the cost of the camera, which is around £180 new, but you might be able to pick up second hand.

Mono is the most sensitive and will see many more stars than the colour camera, this means there will almost always be a guide star in the FOV which is quite large with the finderguider anyway.  This is the system i use and it works well.

Carole 

[VilleM]

1/500 and trails? If your polarscope was pointing even close to north I would suspect that mount wasnt tracking or shutter caused telescope to shake slightly.

-V

[ronin]

You must have something wrong on the setup or data. With the mount polar aligned I would have expected 30 second exposures and if you take care I would have said 60 seconds. Thinking you may have to reduce those as the scope is a 150 and the focal length is relatively long at 650mm, even so 30-40 seconds should be within its capabilities.

How accurate is the polar alignment? Not the goto alignment as that is something different, don't get those mixed up.

[geordie85]

Was your scope properly collimated? 

If I was you I'd get a colour guide cam as they are great for planetary imaging aswell

[Hughesy94]

shutter making the camera shake was my first thought as it looks more like a shake that a trail, but then longer exposure on the whirlpool galaxy was fine, just obviously the limitations of not being able to track for long periods. i can manage just about 1 minute unguided imaging M51 before i get noticeable star trails, but i would have expected longer than that? When i get home il post a photo of Jupiter that suffered from the trail, just incase it helps anyone with a diagnosis! 

In terms of scope collimation its pretty much new, ive only used it a few times and its left properly covered and protected when im not so shouldnt the collimation still be fine? 

It seems that the colour cameras are good for being a slight all rounder in terms of planetary imaging but then lack the ability to pick out stars as well when doing DSO, and if im going to be using a DSLR for my actual imaging anyway im starting to lean towards the mono variant!

[Hughesy94]

Also the polar alignment is a new concept to me, i followed a video tutorial religiously and thought i had it nailed, but when i looked at it again the other night it didnt seem so good so ive tried to redo it and when its next clear il try and image again. 

When im aligning my GOTO, it is 100% of the time always off, i have to adjust manually to the star and then set it and move on, but then when i want to 'GOTO' an object after ive done a 2/3 star alignment its still off and i have to fiddle to center the object anyway, does this sound like a common issue if my PA was out?

[LightBucket]

Don't forget now to put daylight saving as "on" when setting up, or it will be out....

[Hughesy94]

yeah that was my first mistake when i used it (i have no experience with the motorised mounts so just learning as i go along), was hoping that would have sorted it but then when i retried it...alas it was still out! :'(

[LightBucket]

Even if the mount was not tracking at all, at 1/500th second exposure you would not get  trailing, the exposure is too short for it to show, sounds like something is wrong with the camera or the way it is set up, and not the mount, but you still need to sort out the alignment, sounds like two issues to me....

[Hughesy94]

This photo had an exposure time of 1/5s, but still shouldn't have so much movement. Im starting to think your'e right Ronin that it is some mechanical interference. 

IMG_0302.CR2

[knobby]

How are you firing the shutter ?

[Hughesy94]

I use a wireless remote, i have my DSLR attached to the prime focus using a T ring and the whole set up is on a brick pier, so it should be pretty sturdy! 

[geordie85]

4 hours ago, Hughesy94 said:

 

In terms of scope collimation its pretty much new, ive only used it a few times and its left properly covered and protected when im not so shouldnt the collimation still be fine? 

Have you ever collimated it or even checked the collimation? Just because it's a new scope doesn't mean the collimation will be correct. Even slightly sharp movements can put it out which is very likely to happen when it's in the delivery truck.

[LightBucket]

That's not a collimation issue, the mount is slipping, or tracking out somehow....it looks like an alignment issue but I would expect to see that on a mount that was not very well polar aligned on maybe a five to ten second exposure, (with your scope) not on a 1/5th second one....very strange

[tooth_dr]

I can't see the image as I'm on my phone but would it be the mirror shake, affecting the bright objects like Jupiter?

[Hughesy94]

Im using a wireless remote to trigger my DSLR and the whole set up is on a brick pier so it should be very stable! i havent had this issue before when ive imaged, and i managed to take exposures that night of M51 without the same trouble (just about managed a minute with minimal trail). Its very puzzling and i have no idea where to go with it? :/ I think im going to have to find another clear night when im not busy and retry now ive tweaked the Polar alignment. 

[The-MathMog]

That right there could look like shaking caused by the DSLR flipping the mirror into place. That will show vibrations in even very short exposures. Try to look in the settings for something like "Exposure Delay Mode" or something similar, which makes the exposure start a second after the mirror has made its movement, making the vibrations settle before taking the picture.

On another note, you would have to make the exposure even shorter to get out the details on Jupiter too, as it is very bright

[tooth_dr]

6 hours ago, Hughesy94 said:

Im using a wireless remote to trigger my DSLR and the whole set up is on a brick pier so it should be very stable! i havent had this issue before when ive imaged, and i managed to take exposures that night of M51 without the same trouble (just about managed a minute with minimal trail). Its very puzzling and i have no idea where to go with it? :/ I think im going to have to find another clear night when im not busy and retry now ive tweaked the Polar alignment. 

It's caused by the mirror inside the camera, causing it to shake slightly. It wouldn't affect m51 as there is nothing bright enough on the screen to be recorded instantly unlike Jupiter and her moons. Is there a mirror lock up mode?

[CraigT82]

Yup I'd agree that is mirror shake, it's stronger on the 1/500 exposures as the mirror is going up then back down again almost instantly causing a bigger shake than it does when there is a few seconds between going up then back down.

 

[LightBucket]

Hmmmm, if it was mirror shake, the drift would be random, and not perfectly in one direction.....in my opinion

[tooth_dr]

10 minutes ago, LightBucket said:

Hmmmm, if it was mirror shake, the drift would be random, and not perfectly in one direction.....in my opinion

 

Can anyone post the image as a JPEG as I cant see it!?  I would infer that as the mirror always moves the same way, you would not expect a random appearance to the marks.

[happy-kat]

Often for planets video clips are used to create an image. Seeing turbulence etc is so unpredictable that a single exposure doesn't capture the best image.

[IanL]

31 minutes ago, LightBucket said:

Hmmmm, if it was mirror shake, the drift would be random, and not perfectly in one direction.....in my opinion

In my experience, not opinion, mirror shake is usually in the 'up/down' direction with respect to the camera body as that's the direction the mirror flips and causes the camera/focus tube to bounce. You will see this on short exposures of bright targets more than you would on (say) M51 because it is much fainter and the bounce settles after a few seconds before any significant signal has accumulated.

If shooting single frames, you need to use the mirror lockup function (if available) to flip it out of the way, pause for the vibration to settle and then open the shutter.  This is much easier to accomplish with a laptop and some control software like APT or BackYardEOS (BYE).

[LightBucket]

Sorry but I just don't see the mirror in a DSLR camera shaking the scope and mount enough to cause that, as long as the set up is rigid, it would have to move the whole lot a fraction, and I don't see it, but like I say it's just my opinion. 

 I have never used mirror lock yet and never had an issue, but I don't use it for planets, so maybe I wouldn't see it anyway.