14yr old with 6inch SE beats 60 year old with 8 inch SE!! 60 year old NOT happy! :-)

[johnturley]

17 hours ago, Mark2022 said:

So what do you use now? I was thinking how I might build one but I don't have the tools and skills but I'd give it a try. It doesn't look that bulky.

I'll give you a laugh: I was even looking at how big you can buy "Lazy Susans" because I've just built (built isn't  the word really - it's just laying one brick on top of another) a "Todmorden" pier in a flip top roof  'shed' I built and I thought "Wouldn't it be fun to have an observing chair on top of a Lazy Susan so, when you slewed to a different object,  you don't have to move your bum an inch!"

I actually have a Nadira folding chair now which I purchased from Rother Valley Optics, its not ideal but it does fold up small.

I also have some steps on wheels, on which I place my laptop when doing astro-photography, I just couldn't wheel them around the shed with the original bulky observing chair in place.

John 

[IDM]

As another person trying to learn/improve my planetary imaging I have been following this thread with interest. I totally accept the comments made about the need for good seeing in order to get decent images (no argument). I also understand the high frame rate to try and see through the best seeing. So in my case I use an SellaLyra 8 inch classical cassegrain with a Zwo ASI224 so I use reduce my region of interest round a planet and can get frame rates up to about 180FPS.

I also understand the need for good focus, and now use a DIY electronic focuser which helps. Thought I do find the focus on my scope seems soft in that small changes in focus don't seem to alter what appears on the screen. Though I suppose the issue might be the seeing making it difficult to totally nail the focus.

What I think would be helpful for the experts are hints on tips on other elements needed to get the best from a scope camera system. How much should I worry about the histogram?

I also notic ethe comments around attaching the end of a barlow direct to the camera to get 1.X magnification. My Celestron barlow doesn't come apart like that. Can someone suggest a half decent suitable barlow that can be used? 

I also would love any helps or links to good guides on processing. I have watched so many You Tube videos which often say different things. some say use linked wavelets others say don't! It's very difficult to know what to do to improve and then I see some of the stunning images that others put out and I am left scratching my head as to what to do. Any help gratefully received.

I think I noticed earlier in the thread that Mark was wondering if he needed a larger/better scope. This is something I also wonder about so am currently thinking of going to either 9 1/4 or 11 inch SCT, but I am concerned that I will still have the same problems as with the current setup. So as I said any comments or links to the best up to date information on squeezing the most out of my planetary imaging would be really gratefully received by me and indeed Mark might then be able to take on his 14 year old adversary 🙂.

Thanks

Ian 

[CraigT82]

41 minutes ago, IDM said:

As another person trying to learn/improve my planetary imaging I have been following this thread with interest. I totally accept the comments made about the need for good seeing in order to get decent images (no argument). I also understand the high frame rate to try and see through the best seeing. So in my case I use an SellaLyra 8 inch classical cassegrain with a Zwo ASI224 so I use reduce my region of interest round a planet and can get frame rates up to about 180FPS.

I also understand the need for good focus, and now use a DIY electronic focuser which helps. Thought I do find the focus on my scope seems soft in that small changes in focus don't seem to alter what appears on the screen. Though I suppose the issue might be the seeing making it difficult to totally nail the focus.

What I think would be helpful for the experts are hints on tips on other elements needed to get the best from a scope camera system. How much should I worry about the histogram?

I also notic ethe comments around attaching the end of a barlow direct to the camera to get 1.X magnification. My Celestron barlow doesn't come apart like that. Can someone suggest a half decent suitable barlow that can be used? 

I also would love any helps or links to good guides on processing. I have watched so many You Tube videos which often say different things. some say use linked wavelets others say don't! It's very difficult to know what to do to improve and then I see some of the stunning images that others put out and I am left scratching my head as to what to do. Any help gratefully received.

I think I noticed earlier in the thread that Mark was wondering if he needed a larger/better scope. This is something I also wonder about so am currently thinking of going to either 9 1/4 or 11 inch SCT, but I am concerned that I will still have the same problems as with the current setup. So as I said any comments or links to the best up to date information on squeezing the most out of my planetary imaging would be really gratefully received by me and indeed Mark might then be able to take on his 14 year old adversary 🙂.

Thanks

Ian 

Something to check on is your collimation.  With any cassegrain system with a fast parabolic primary the collimation is going to be sensitive -even a small amount of miss-collimation could ruin high resolution images.

The best way to collimate is to capture an video of a star through your complete imaging train (Barlow, filters, ADC etc...),  and stack/sharpen it (same way as any planetary image). What you want to inspect is the first diffraction ring and how complete it is (see image below).

If the ring is complete and even all around the collimation is good.

If the ring is bunched up to one side then collimation is off.  Use the collimation screws to move the star in the opposite direction to the bunching, and shoot a new video to check. Repeat until the ring is even and complete.

Best to do this on a star that is close in the sky to your imaging target.

[IDM]

On 03/10/2023 at 16:23, CraigT82 said:

The best way to collimate is to capture an video of a star through your complete imaging train (Barlow, filters, ADC etc...),  and stack/sharpen it (same way as any planetary image). What you want to inspect is the first diffraction ring and how complete it is (see image below).

Thanks for that I would never think of checking collimation in such a manner but will try it (if the clouds ever lift!!!).

[geoflewis]

On 01/10/2023 at 20:22, Mark2022 said:

I  refuse to "buy" that until I see the reality of it. I don't dispute it does have an effect but I don't "buy into" that much of an effect. I will be more than happy when I am proven wrong in my thinking. 

Hi Mark,

I don't know if the following comparison will help convince you, but here goes.

It is from a slide that I include in a presentation that I gave to Fanham Astro Society a few years ago, when I lived in Surrey and more recently to Orpington Astro Society when I was requested to speak there by @carastro

The heading that I gave this slide was 'Seeing is everything', which of course it is not, but it is a huge contributory factor to obtaining or failing to obtain high resolution images.

As you can see these 3 images, which are the result of derotation in WinJupos cover just over 2 hours elapsed time. When I started the session Jupiter's red spot was heading off the limb and whilst the seeing wasn't good by any standards, it deteriorated over the next couple of hours, to the point that the images being captured were just mush. I didn't add the elevation for each image, but my recollection is that Jupiter was gaining altitude during this session, so if anything conditions for capture should have improved (I've checked ephemerides and my recollection is correct with Jupiter at 43° elevation for the first image and had risen to 56° by the time of the last image). Nothing else changed, same scope, camera, barlow and ADC - it was just the seeing that deteriorated and there is nothing you can do about it (other than relocate). NB I know that there's less data in the 3rd image, but 7 mins is long enough for HR images, it was just that I finally gave up trying due to the poor seeing.

The other very important factor as @CraigT82 stated is good collimation, which absolutely is something that you can fix, but not when the seeing is bad as you can't get a stable enough star image to accurately assess the image.

Good luck.

 

Edited October 6, 2023 by geoflewis

[Bugdozer]

Sorry, probably an idiot question here, but I am still getting to grips with imaging methods. 

When you say you took your image with a 2x Barlow (and the kid used a 3x Barlow), do you mean the setup was basically just putting the Barlow into the scope like you normally would, and then attaching the camera instead of an eyepiece? So like prime focus photography, but with a Barlow in between the scope and camera? 

[geoflewis]

3 hours ago, Bugdozer said:

Sorry, probably an idiot question here, but I am still getting to grips with imaging methods. 

When you say you took your image with a 2x Barlow (and the kid used a 3x Barlow), do you mean the setup was basically just putting the Barlow into the scope like you normally would, and then attaching the camera instead of an eyepiece? So like prime focus photography, but with a Barlow in between the scope and camera? 

Yes, the barlow is used to increase the effective focal length of the scope, by placing it betwen the scope and camera.

[Bugdozer]

9 hours ago, geoflewis said:

Yes, the barlow is used to increase the effective focal length of the scope, by placing it betwen the scope and camera.

And would this technique work if one was to use a DSLR in place of the camera you used?

[geoflewis]

23 minutes ago, Bugdozer said:

And would this technique work if one was to use a DSLR in place of the camera you used?

Yes, but please note that a DSLR camera is not a very good option for planetary imaging. I have used one with moderate succes, but you need to shoot video (or download steam of individual frames for stacking). DSLR video is often compressed movie format which can lose a lot of detail.

Which DSLR camera do you have?

Edited October 10, 2023 by geoflewis

[Bugdozer]

3 minutes ago, geoflewis said:

Yes, but please note that a DSLR camera is not a very good option for planetary imaging. I have used one with moderate succes, but you need to shoot video (or download steam of individual frames for stacking). DSLR video is often compressed movie format which can lose a lot of detail.

Which DSLR camera do you have?

I have a Nikon D90. The oldest DSLR that can do video there is! So not the ideal tool for planetary photography. However, I am working on the basis of "this is the equipment I have, what can I get out of it?" rather than "this is the photo I want to take, what equipment should I buy?" So yes I know it's not optimal, at the moment I have used an eyepiece projection adapter to image Jupiter with reasonable success via video stacking, and I was wondering how using a Barlow instead might compare. Probably the best thing to do is just to try it.

[geoflewis]

1 minute ago, Bugdozer said:

I have a Nikon D90. The oldest DSLR that can do video there is! So not the ideal tool for planetary photography. However, I am working on the basis of "this is the equipment I have, what can I get out of it?" rather than "this is the photo I want to take, what equipment should I buy?" So yes I know it's not optimal, at the moment I have used an eyepiece projection adapter to image Jupiter with reasonable success via video stacking, and I was wondering how using a Barlow instead might compare. Probably the best thing to do is just to try it.

This image of Jupiter was captured with my Nikon D90 and a x3 Barlow.

[Bugdozer]

6 minutes ago, geoflewis said:

This image of Jupiter was captured with my Nikon D90 and a x3 Barlow.

That's impressive! Better than I have managed so far. I shall give it a go!

[geoflewis]

6 minutes ago, Bugdozer said:

That's impressive! Better than I have managed so far. I shall give it a go!

I've sent you a PM with additional info

[Chaz2b]

I’ve just been looking at comparisons of the two scopes, what was noted that the 8” is under mounted! Meaning the 8” is slightly too heavy for the mount provided. Are you using the Celestron mount that came with the scope? Do you have a better eq mount?

The other noted result was that when it came to planetery viewing the 6” was very much close to the 8”, the reviewer stating how good the optics in the 6” is therefore when it came to imaging they are very close on planetary objects with the 8” winning out on dso’s as you would expect with the extra light grasp.

This would suggest, to me anyway, that had you bought the 6” you would have had similar results to your 8” in your location.

chaz

[bosun21]

I don’t understand how collimating with the imaging train in place is correct. If you collimate the SCT perfectly without the train attached then attach it and have to adjust the collimation again you are surely knocking the scope out of its actual collimation point. My thinking says you should ensure that your train is not inducing any tilt and if it is rectify that instead of compensating for it by moving the scope out of its good collimation. Making the train all screw on fittings would be advisable.

[CraigT82]

4 hours ago, bosun21 said:

I don’t understand how collimating with the imaging train in place is correct. If you collimate the SCT perfectly without the train attached then attach it and have to adjust the collimation again you are surely knocking the scope out of its actual collimation point. My thinking says you should ensure that your train is not inducing any tilt and if it is rectify that instead of compensating for it by moving the scope out of its good collimation. Making the train all screw on fittings would be advisable.

Think about collimation simply as the act of making sure the centre of your primary mirror's optical axis is landing on the centre of your camera chip.

The centre of the primary mirrors optical axis is where the image is sharpest and coma free (i.e. the "sweet spot" or "on axis").  The faster the mirror the smaller this coma free zone is. SCTs have very fast primary mirrors and so are sensitive to collimation despite the long overall focal length,

On an SCT all you can do is twiddle the secondary mirror screws, which in effect steer the direction that the primary mirror is pointing - think of the optical axis of the primary mirror as a long thin stick protruding from the centre of the mirror - So you want to make this stick point right to the centre of your camera sensor.

If you collimate the scope with juts an eyepiece in the back, great the view through that eyepiece will be 'on axis' and sharp.  However if you then remove the eyepiece and add a heavy imaging train the camera sensor will most likely not be intercepting the 'stick' right in the middle of the sensor, if at all, and that's because of droop or sag from the weight of the imaging train (not to mention large focus changes - moving the mirror). So effectively you now need to recollimate the scope so that the stick is again pointing right to the middle of the camera sensor.

If you didn't re-collimate and you go ahead and start imaging, the camera sensor will be capturing images which are off axis or out of the sweet spot, and will be affected by coma which will reduce the sharpness of the resulting image. This can be seen in planetary images if you crank up the levels - you can see a faint kind of halo effect which is the captured light being smeared to one side by the coma (red arrows). In this example, which is only a slight miscollimation, the user would need to use the collimation screws to move the image to the upper left on the chip (green arrow), to bring it back into the sweet spot where there is no coma.

 

 

 

 

Edited October 10, 2023 by CraigT82

[bosun21]

2 hours ago, CraigT82 said:

you can see a faint kind of halo effect which is the captured light being smeared to one side by the coma (

Isn’t that atmospheric dispersion as there should be no coma in the centre of the field? I’m just starting out with planetary imaging and still trying to get a grasp of it all.

[CraigT82]

11 minutes ago, bosun21 said:

Isn’t that atmospheric dispersion as there should be no coma in the centre of the field? I’m just starting out with planetary imaging and still trying to get a grasp of it all.

No, atmospheric dispersion is obvious in any image usually, It’s also directionally consistent with blue shifted upwards towards the zenith, and red shifted downwards towards the horizon.

This image above wasn’t exactly in the centre of the field so coma is smudging the light to one side, as indicated by the spilling light to the 4 o’clock direction