Solar imaging confirmation

[Rustang]

While I'm still not in a position to use my main imaging rig for DSO's and that will probably be the case for a while yet, I've started looking more into Solar imaging as something else to do for now. I've spent a couple of days reading up on the web to try and find the best (affordable) way to create a simple set up for now at the focal length I feel is acceptable of approx 1000mm to fit the whole sun in frame. I've come to the conclusion that even though its still at some cost, the cheapest and probably best way to do this is to go for a small ED refractor, something like the SW 72ED scope and at 430mm FL use a x2.5 barlow lens (I'm looking at using the Celestron Luminos 2inch x2.5 barlow) which with my Canon 6D would give me an fl of 1075mm if I'm correct? I've got a couple of mounts I could use, HEQ5 Pro, Star adventurer and a couple of static mounts. I will be starting out with Badder solar film for now while I find my feet with it all. 

This is to get me started but I would like this set up to also be a little future proof so that later down the line I can add a CDD or CMOS dedicated camera and possibly something like a Lunt Herschel wedge to do Ha solar imaging? I know those wedges are dedicated to refractors hence my thinking of a refractor to start with would be best. 

Anything I'm missing for safety, extra equipment I've missed or something that would be a better fit etc, please let me know  

 

Edited March 23, 2022 by Rustang

[vlaiv]

Solar imaging is like other planetary imaging - best way to get good images is to use lucky imaging approach.

If you already have DSO imaging rig - you probably have guide camera. That is what you should use. Any guide camera capable of fast raw output will be better choice than DSLR.

Herschel wedge serves the same purpose as Baader solar film - solar white light, not solar Ha. But unlike solar film, it can only be used with refractors.

Solar Ha is much more expensive.

Anyway, back to solar white light imaging. Capturing full disk images, if that is what you want to do - will depend on combination of focal length and sensor size. Another important thing is - you need aperture for resolution. 72mm scope will have very little aperture.

At sampling matched to resolving power of the telescope - max solar image that you will be able to make in white light with say Baader Solar Continuum filter - is Sun image of 2400px diameter (0.77"/px). Depending on pixel size of your camera - you will have to use some sort of barlow.

For the same amount of money as 72ED - you can have 100 or more mm of aperture and get more detailed image of the sun.

Here are some examples - 4" F/10 achromat with Baader Solar Continuum filter will be very good solar instrument. If you have 2.9um camera - you don't will not need barlow as optimum at 540nm (Baader solar continuum) for 2.9um pixel size is ~F/10.75. You can also use 4" F/11 achromat - a bit more expensive but optically a bit better (won't make much difference in image quality but images will be a bit easier to process).

Mak127 will be good match for 3.75um pixel size.

[Rustang]

Cheers Vlaiv, so yes I do have a guide came, a ZWO 120MC, not the best.  I was looking to use my Canon 6D full frame camera to start with though at 6.55um.  As always your advice and info is much apricated but some goes a little past my understanding sometimes, I can be a little dumb, dumb at understanding it, not your fault  

So I would be wasting my time with a small refactor then. I dont fully grasp the focal length, pixel size and aperture combo for the best resolution, you might have to break it down a little for me. I just mostly get that anything from approx 1000-2500mm fl will fit the whole sun in frame, obviously 2500mm much better and only very vaguley the camera pixel resolution compatibility side of things. Because of this, When you say a 4inch refractor, what fl would I need to look at?!

I'm guessing then that if i did get a scope and use my Canon, I would then have to change scopes again if using a camera such as my guide camera later down the line?

Edited March 23, 2022 by Rustang

[Elp]

Here's two I've done full frame with two different setups, they're not brilliant but I'm still progressing and am yet to use my mono camera:

You need to decide whether you want to do white light or hydrogen alpha first. The spectacular images you see of fine surface detail, flare and prominences requires hydrogen alpha equipment, white light you can do quite readily and cheaply. For either option make sure you follow all safety protocols.

[vlaiv]

2 minutes ago, Rustang said:

So I would be wasting my time with a small refactor then

Well - no

You can still do nice solar images with small refractor as well - just don't expect very high resolution images.

What does that mean? Like I said - exploiting full resolving power of the telescope will make your full solar disk be 2400px in diameter (that is with 72mm scope).

Larger telescope will simply let you make more detailed / larger image. It really depends on how detailed you want to go.

Here are few comparisons to help put things into perspective.

With Solar Ha telescopes - people often image with smaller apertures. 35, 40, 50 or 60mm are very common apertures as dedicated solar Ha scopes past 60mm become very expensive rapidly. Given that Ha wavelength is longer than most visible light - that also reduces level of detail. Full solar disk of 50mm scope for example is less than 1000px in diameter.

On the other hand, Moon is same apparent size as the Sun in the sky, so it is pretty much the same target as far as imaging goes (if we consider size and level of detail). Most people will find 1000px moon image to be very small and most appreciate zoom in on individual features.

Here is an example of full lunar disk image (right clicky / open in new tab thingy and zoom in to 100% for full detail):

This was produced with 100mm Maksutov - and even reduced in size because seeing was not allowing for full resolution image.

It all depends on how detailed you want to go and if you are going to use scope for something else as well.

72ed is nice little travel scope and small imaging scope and fun wide field scope. If you plan in using it in any/all of those roles next to solar imaging - then I say, get that one.

You don't need ED scope for white light solar imaging. With Baader Solar Continuum filter - you can use simple achromatic refractor. Filter will remove any chromatic aberration and make views very sharp. I highly recommend that filter for solar white light imaging with any scope. In that sense - simple 80mm longer achromat will give better imaging result, so if budget is tight and any other intended purpose can be served with 80mm scope (just use at least F/7 one - don't use ST80).

Mak100 is another cheap option that will serve solar imaging role - and you won't need barlow.

Here are some formulae to help you decide:

Optimum F/ratio of setup for lucky imaging: F/ratio = pixel_size * 2 / wavelength

For example, for ASI120 with 3.75um pixel size and Baader Solar Continuum filter which is 540nm filter -  formula goes like this

F/ratio = 3.75um * 2 / 0.54um = 13.888 = ~F/14

(we convert 540nm to 0.54um because we need same length units)

Sensor height in mm for particular focal length

Sensor height >= 2 * tan(18 / 60) * focal_length

(here I put that FOV is 36 arc minutes to have some space around the solar disk - as Sun's diameter is 30 arc minutes)

At 1000mm - needed sensor height would be ~10.5mm to capture the whole disk.

 

 

[Rustang]

3 minutes ago, Elp said:

Here's two I've done full frame with two different setups, they're not brilliant but I'm still progressing and am yet to use my mono camera:

You need to decide whether you want to do white light or hydrogen alpha first. The spectacular images you see of fine surface detail, flare and prominences requires hydrogen alpha equipment, white light you can do quite readily and cheaply. For either option make sure you follow all safety protocols.

lovely images and I would be more than happy with some like those to start with and most certainly (because of cost) just white light for now. Was the second image Ha or white light as it states a HAlpha - Coronad PST was used?

[Rustang]

30 minutes ago, vlaiv said:

Well - no

You can still do nice solar images with small refractor as well - just don't expect very high resolution images.

What does that mean? Like I said - exploiting full resolving power of the telescope will make your full solar disk be 2400px in diameter (that is with 72mm scope).

Larger telescope will simply let you make more detailed / larger image. It really depends on how detailed you want to go.

Here are few comparisons to help put things into perspective.

With Solar Ha telescopes - people often image with smaller apertures. 35, 40, 50 or 60mm are very common apertures as dedicated solar Ha scopes past 60mm become very expensive rapidly. Given that Ha wavelength is longer than most visible light - that also reduces level of detail. Full solar disk of 50mm scope for example is less than 1000px in diameter.

On the other hand, Moon is same apparent size as the Sun in the sky, so it is pretty much the same target as far as imaging goes (if we consider size and level of detail). Most people will find 1000px moon image to be very small and most appreciate zoom in on individual features.

Here is an example of full lunar disk image (right clicky / open in new tab thingy and zoom in to 100% for full detail):

This was produced with 100mm Maksutov - and even reduced in size because seeing was not allowing for full resolution image.

It all depends on how detailed you want to go and if you are going to use scope for something else as well.

72ed is nice little travel scope and small imaging scope and fun wide field scope. If you plan in using it in any/all of those roles next to solar imaging - then I say, get that one.

You don't need ED scope for white light solar imaging. With Baader Solar Continuum filter - you can use simple achromatic refractor. Filter will remove any chromatic aberration and make views very sharp. I highly recommend that filter for solar white light imaging with any scope. In that sense - simple 80mm longer achromat will give better imaging result, so if budget is tight and any other intended purpose can be served with 80mm scope (just use at least F/7 one - don't use ST80).

Mak100 is another cheap option that will serve solar imaging role - and you won't need barlow.

Here are some formulae to help you decide:

Optimum F/ratio of setup for lucky imaging: F/ratio = pixel_size * 2 / wavelength

For example, for ASI120 with 3.75um pixel size and Baader Solar Continuum filter which is 540nm filter -  formula goes like this

F/ratio = 3.75um * 2 / 0.54um = 13.888 = ~F/14

(we convert 540nm to 0.54um because we need same length units)

Sensor height in mm for particular focal length

Sensor height >= 2 * tan(18 / 60) * focal_length

(here I put that FOV is 36 arc minutes to have some space around the solar disk - as Sun's diameter is 30 arc minutes)

At 1000mm - needed sensor height would be ~10.5mm to capture the whole disk.

 

 

I'm doing my best to understand Vlaiv, I promise, still a bit to mathematical for me though, again not your fault!  

So what ever the set up ends up being, it will be just for Solar imaging and possibly It would be, I guess good to consider it for imaging the moon which is also something of interest for me. I'm thinking the right camera would suit both and then the right scope but if I was to buy a simply achromatic scope for solar, what about chromatic aberration with moon imaging? I guess I could just concentrate on the solar stuff for now.

I should have made it more clear that its the Baader solar 'film' that I'm looking to use, not a filter! Baader AstroSolar Safety Film ND 5.0 | First Light Optics

My expectations would be for a nice resolution image, clear enough to see the little details like the sun spots in reasonably good quality, would the first white light image above posted by Elp be a realistic hope for starting out? 

Edited March 23, 2022 by Rustang

[Elp]

The Coronado PST is a hydrogen alpha telescope for solar observation only, it was never designed for imaging but that hasn't stopped people like us trying and getting results. I would say the first white light image would be fairly realistic if you're used to lunar imaging for example, you do have to take note of what @vlaiv has said though, the camera does have to match what the scope is capable of. Smaller pixels will mean a more zoomed in view in basic terms, it's fortuitous I have fairly short focal length scopes which counteract this effect and allow full disk imaging. If I were to use my 290mm I'd have to make a mosaic with either setup.

Edited March 23, 2022 by Elp

[vlaiv]

2 minutes ago, Rustang said:

I'm doing my best to understand Vlaiv, I promise!  So what ever the set up ends up being, it will be for Solar imaging and possibly It would be, I guess good to consider it for imaging the moon which is also something of interest for me. I'm thinking the right camera would suit both and then the right scope but if I was to buy a simply achromatic scope, what about chromatic aberration with moon imaging? I guess I could just concentrate on the solar stuff for now.

I recommend using Baader Solar Continuum filter for both imaging moon and sun.

This filter is used in combination with other filters - like Baader AstroSolar Safety Film - or Herschel wedge.

It this item:

https://www.firstlightoptics.com/solar-filters/baader-solar-continuum-filter.html

It must be used with regular solar filter for the telescope - not by itself.

What does it do? It makes things sharper and adds contrast. It does this in couple of ways:

1. It isolates wavelength of light in white light solar that has good contrast of interesting white light features. This is how regular filters for planets work.

2. It reduces effects of seeing as different wavelengths of light bend differently in atmosphere (think prism and color separation) and this creates additional blur. With isolation of one wavelength (and its neighboring wavelengths) this effect is reduced - sharper image with more contrast is produced. This is feature of narrowband filters

3. It operates in center of the spectrum. Refractors have sharpest image / highest Strehl ratio in the center of the spectrum because they are optimized for visual use. In this part of the spectrum our eyes are most sensitive and it pays to be the sharpest in this part of the spectrum. This is particularly true for achromatic refractors as narrowband nature of the filters remove chromatic aberration and any spherochromatism is also removed.

For this reason - I recommend having this filter for white light solar work anyway, but if you have this filter - you can use it for both solar and lunar work (some people use IR filters for lunar work or narrowband filters like nighttime Ha or OIII filters for the same reason) and when using this filter - you can use achromatic scopes as well without fear of chromatic aberration.

Only drawback is that it will produce monochromatic images, but neither Solar white light or lunar produce much color anyway (there has been trend of boosted saturation "color/mineral" moon shots lately - but in reality moon is mostly grey and without any color).

13 minutes ago, Rustang said:

I should have made it more clear that its the Baader solar 'film' that I'm looking to use, not a filter! Baader AstroSolar Safety Film ND 5.0 | First Light Optics

You probably want to use ND3.8 version of that filter as it is better suited for photography. ND5 version is for visual.

https://www.firstlightoptics.com/solar-filters/astrosolar-photo-film-od-38.html

Just be careful! ND5 is suited both for visual and photographic work, while ND 3.8 is only suited for photographic work. ND3.8 is a bit better for photos as it allows shorter exposures by letting more light in - but that makes it unsafe for visual work.

If you plan on using it both visually and photographically - use ND5 version like you planned.

16 minutes ago, Rustang said:

My expectations would be for a nice resolution image, clear enough to see the little details like the sun spots in reasonably good quality, would the first white light image above as be a realistic hope for starting out? 

I don't see why not.

This is my first ever solar white light image (and although I have right gear, I haven't really imaged anything since):

This was taken with camera that is equivalent to ASI120 (QHY5IILc) on 130mm newtonian with Baader solar film (ND5 version as we were observing solar eclipse at that time).

This one was taken by my friend with a mobile phone at the eyepiece while observing eclipse:

This was my attempt of capturing whole lunar limb - it is mosaic because sensor was too small - but Moon moved a bit between panels so it looks elongated a bit. My processing is also rudimentary so panel seams can be seen:

[Rustang]

6 minutes ago, vlaiv said:

I recommend using Baader Solar Continuum filter for both imaging moon and sun.

This filter is used in combination with other filters - like Baader AstroSolar Safety Film - or Herschel wedge.

It this item:

https://www.firstlightoptics.com/solar-filters/baader-solar-continuum-filter.html

It must be used with regular solar filter for the telescope - not by itself.

What does it do? It makes things sharper and adds contrast. It does this in couple of ways:

1. It isolates wavelength of light in white light solar that has good contrast of interesting white light features. This is how regular filters for planets work.

2. It reduces effects of seeing as different wavelengths of light bend differently in atmosphere (think prism and color separation) and this creates additional blur. With isolation of one wavelength (and its neighboring wavelengths) this effect is reduced - sharper image with more contrast is produced. This is feature of narrowband filters

3. It operates in center of the spectrum. Refractors have sharpest image / highest Strehl ratio in the center of the spectrum because they are optimized for visual use. In this part of the spectrum our eyes are most sensitive and it pays to be the sharpest in this part of the spectrum. This is particularly true for achromatic refractors as narrowband nature of the filters remove chromatic aberration and any spherochromatism is also removed.

For this reason - I recommend having this filter for white light solar work anyway, but if you have this filter - you can use it for both solar and lunar work (some people use IR filters for lunar work or narrowband filters like nighttime Ha or OIII filters for the same reason) and when using this filter - you can use achromatic scopes as well without fear of chromatic aberration.

Only drawback is that it will produce monochromatic images, but neither Solar white light or lunar produce much color anyway (there has been trend of boosted saturation "color/mineral" moon shots lately - but in reality moon is mostly grey and without any color).

You probably want to use ND3.8 version of that filter as it is better suited for photography. ND5 version is for visual.

https://www.firstlightoptics.com/solar-filters/astrosolar-photo-film-od-38.html

Just be careful! ND5 is suited both for visual and photographic work, while ND 3.8 is only suited for photographic work. ND3.8 is a bit better for photos as it allows shorter exposures by letting more light in - but that makes it unsafe for visual work.

If you plan on using it both visually and photographically - use ND5 version like you planned.

I don't see why not.

This is my first ever solar white light image (and although I have right gear, I haven't really imaged anything since):

This was taken with camera that is equivalent to ASI120 (QHY5IILc) on 130mm newtonian with Baader solar film (ND5 version as we were observing solar eclipse at that time).

This one was taken by my friend with a mobile phone at the eyepiece while observing eclipse:

This was my attempt of capturing whole lunar limb - it is mosaic because sensor was too small - but Moon moved a bit between panels so it looks elongated a bit. My processing is also rudimentary so panel seams can be seen:

I have the ND5 on the way so will start with that, the 3.8 is out of stock with FLO but will look else where and get some on order. So just to really break down the whole "resolution" into really simple terms, better resolution is a camera sensor pixel size and scope that brings you in close therefore having better resolution?, like a picture of say a  landscape, when you zoom in to the tree in the distance on a hill, the more you zoom the lower the resolution? obviously camera/equipment quality makes some small difference I guess.

[vlaiv]

2 minutes ago, Rustang said:

I have the ND5 on the way so will start with that, the 3.8 is out of stock with FLO but will look else where and get some on order. So just to really break down the whole "resolution" into really simple terms, better resolution is a camera sensor pixel size and scope that brings you in close therefore having better resolution?, like a picture of say a  landscape, when you zoom in to the tree in the distance on a hill, the more you zoom the lower the resolution? obviously camera/equipment quality makes some small difference I guess.

Don't confuse zoom with resolution.

Long focal length and small pixels will give you more zoom. In daytime photography when you are not near the limits of resolution - this simply means that you'll be able to see a tree at a distance on a hill.

With astrophotography where we are operating on the limits of what telescope can resolve - limited by either seeing (long exposure) or telescope aperture (planetary / lucky imaging) - resolution means sharpness / detail

In my view - it is important to match "zoom" with resolution - or level of detail. For example:

these two images show same lunar region. Although they are zoomed in roughly the same - first image has more resolution. Much more detail can be seen and detail is sharper. In fact - first image has proper matching of zoom and resolution. All that can be seen on that zoom level is actually seen in the image.

Second image is simply blurry.

By the way - these two images were shot with same aperture 100mm - but first image was shot using lucky imaging technique using planetary camera and processed carefully. Second image was taken with ST102 and DSLR - it is single frame.

I think main difference is recording and processing technique. Lucky imaging was invented and is used for a reason. It simply allows for optics potential to be exploited almost to the limit if properly used.

[Rustang]

4 minutes ago, vlaiv said:

Don't confuse zoom with resolution.

Long focal length and small pixels will give you more zoom. In daytime photography when you are not near the limits of resolution - this simply means that you'll be able to see a tree at a distance on a hill.

With astrophotography where we are operating on the limits of what telescope can resolve - limited by either seeing (long exposure) or telescope aperture (planetary / lucky imaging) - resolution means sharpness / detail

In my view - it is important to match "zoom" with resolution - or level of detail. For example:

these two images show same lunar region. Although they are zoomed in roughly the same - first image has more resolution. Much more detail can be seen and detail is sharper. In fact - first image has proper matching of zoom and resolution. All that can be seen on that zoom level is actually seen in the image.

Second image is simply blurry.

By the way - these two images were shot with same aperture 100mm - but first image was shot using lucky imaging technique using planetary camera and processed carefully. Second image was taken with ST102 and DSLR - it is single frame.

I think main difference is recording and processing technique. Lucky imaging was invented and is used for a reason. It simply allows for optics potential to be exploited almost to the limit if properly used.

Ok cool, I think I'm getting there, so i'm understanding now what we call the "zoom" part, with the help of astronomy tools I can see with a certain scope and camera what field of view "zoomed in" level I would like to image at, so as said fitting the whole sun in nicely.

So then as to really break down and to understand the resolution side of things, if I can take the maths away for a second - matching a camera to a scope what are the simple factors after we now know the filed of view we like with said camera and focal length what are the main driving resolution factors-  firstly the aperture of the scope helps yes? so with the same camera, same focal length a 100mm aperture would be better than a 72mm aperture for resolution? 

[vlaiv]

14 minutes ago, Rustang said:

So then as to really break down and to understand the resolution side of things, if I can take the maths away for a second - matching a camera to a scope what are the simple factors after we now know the filed of view we like with said camera and focal length what are the main driving resolution factors-  firstly the aperture of the scope helps yes? so with the same camera, same focal length a 100mm aperture would be better than a 72mm aperture for resolution? 

Larger the aperture - more detail you will possibly capture.

For a given FOV - size of pixel determines how much detail you will potentially record.

With planetary imaging - F/ratio, or ratio of aperture and focal length is related to pixel size - limit of what can be captured. This is summed up in simple formula:

F/ratio = pixel_size * 2 / wavelength.

If you don't want to bother with wavelength (and for lunar and white light it is ok to just plunk in 500nm in there) it simplifies to F/ratio = pixel_size * 4

There are couple of variables to consider - and they are not independent variables - they depend one on another.

Aperture dictates level of detail, but focal length dictates zoom. Pixels dictate how much of fine detail in that zoom will be captured and sensor size is equal to number of pixels times pixel size and also dictates size of FOV.

There is one thing that you can do - and one you should not do.

You can choose to capture smaller resolution image but you should avoid capturing beyond what telescope can resolve.

What do I mean by this?

Say that you calculate F/14 to be optimum F/ratio for your pixel size - but you find that when using this F/ratio - there is too much zoom and you won't fit whole solar disk on your sensor. It is ok to use faster F/ratio - say F/7 as you it won't hurt your imaging and result - you will capture full disk with level of detail that your camera can provide.

In different scenario - say you have DSLR and you find that good focal length to fit nicely whole solar disk is 1800mm - but you have 90mm of aperture. That translates into F/20 - but your limit is F/14. In this case - you should not use F/20, but instead limit yourself to F/14 and then simply crop image to produce nice FOV.

If you use F/20 - it will hurt your image as there will be more noise then it needs to be (system is slower then it needs to be) and more noise prevents you from sharpening properly.

Hope this all makes sense.

 

[Rustang]

57 minutes ago, vlaiv said:

Larger the aperture - more detail you will possibly capture.

For a given FOV - size of pixel determines how much detail you will potentially record.

With planetary imaging - F/ratio, or ratio of aperture and focal length is related to pixel size - limit of what can be captured. This is summed up in simple formula:

F/ratio = pixel_size * 2 / wavelength.

If you don't want to bother with wavelength (and for lunar and white light it is ok to just plunk in 500nm in there) it simplifies to F/ratio = pixel_size * 4

There are couple of variables to consider - and they are not independent variables - they depend one on another.

Aperture dictates level of detail, but focal length dictates zoom. Pixels dictate how much of fine detail in that zoom will be captured and sensor size is equal to number of pixels times pixel size and also dictates size of FOV.

There is one thing that you can do - and one you should not do.

You can choose to capture smaller resolution image but you should avoid capturing beyond what telescope can resolve.

What do I mean by this?

Say that you calculate F/14 to be optimum F/ratio for your pixel size - but you find that when using this F/ratio - there is too much zoom and you won't fit whole solar disk on your sensor. It is ok to use faster F/ratio - say F/7 as you it won't hurt your imaging and result - you will capture full disk with level of detail that your camera can provide.

In different scenario - say you have DSLR and you find that good focal length to fit nicely whole solar disk is 1800mm - but you have 90mm of aperture. That translates into F/20 - but your limit is F/14. In this case - you should not use F/20, but instead limit yourself to F/14 and then simply crop image to produce nice FOV.

If you use F/20 - it will hurt your image as there will be more noise then it needs to be (system is slower then it needs to be) and more noise prevents you from sharpening properly.

Hope this all makes sense.

 

Thanks Vlaiv, much appreciated there's enough there for me to get my head around but yes I think I'm getting it, thanks for your patients with me

Edited March 23, 2022 by Rustang

[Stu]

It looks like you have got loads of good info from Vlad already, but I’ll just add a few comments of my own. Note that I’m a visual observer so I won’t comment on the specific imaging questions.

In terms of getting started, the solar film is the cheapest way to go. Moving to a Wedge in my experience gives you a definite increase in contrast and detail visually which should be mirrored when imaging. The Lunt 1.25” wedges are really good value and give great performance.

I demonstrated the benefits of aperture to myself just today, by starting off observing with a 76mm scope and moving to a 100mm. The 100mm clearly showed more detail in the active regions and made the granulation pop into view much more clearly. Going too big can run into problems with seeing conditions, but somewhere around 100mm to 120mm is ideal. 100mm is perfect for me as it’s much easier to mount and use.

From a scope perspective, I use apo refractors, but the key thing is to use one which is well corrected in spherical abberation. Fast achro fracs like the StarTravel f5 scopes do tend to show more SA and this kills the fine detail. So, as Vlad has said, a longer focal length 100mm achro scope say f10 or 11 would be a good option. Your 72mm will definitely work, and should be well corrected but the aperture will definitely limit what you can resolve.

I agree on the Continuum filter, I use one permanently installed in my wedge and it does help.

These are a few single frame smartphone shots through my 76mm just as examples.

[Rustang]

4 hours ago, Stu said:

It looks like you have got loads of good info from Vlad already, but I’ll just add a few comments of my own. Note that I’m a visual observer so I won’t comment on the specific imaging questions.

In terms of getting started, the solar film is the cheapest way to go. Moving to a Wedge in my experience gives you a definite increase in contrast and detail visually which should be mirrored when imaging. The Lunt 1.25” wedges are really good value and give great performance.

I demonstrated the benefits of aperture to myself just today, by starting off observing with a 76mm scope and moving to a 100mm. The 100mm clearly showed more detail in the active regions and made the granulation pop into view much more clearly. Going too big can run into problems with seeing conditions, but somewhere around 100mm to 120mm is ideal. 100mm is perfect for me as it’s much easier to mount and use.

From a scope perspective, I use apo refractors, but the key thing is to use one which is well corrected in spherical abberation. Fast achro fracs like the StarTravel f5 scopes do tend to show more SA and this kills the fine detail. So, as Vlad has said, a longer focal length 100mm achro scope say f10 or 11 would be a good option. Your 72mm will definitely work, and should be well corrected but the aperture will definitely limit what you can resolve.

I agree on the Continuum filter, I use one permanently installed in my wedge and it does help.

These are a few single frame smartphone shots through my 76mm just as examples.

Thanks, those images are great. I've got some more thinking to do but nearly there with what I might start out with 👍

[Rustang]

Look what I did, my first ever image of the sun!

While not the best time of the day to photograph the sun, my focus extension tube didnt turn up until this afternoon and I just couldn't wait to give it ago. Thanks everyone for all your help getting set up and thanks to Steve (saganite) for the lovely scope👍

 

Edited March 26, 2022 by Rustang

[wookie1965]

I have used my Tal 100rs with a filter I made and got some great pictures I have a lunt Herschel wedge now just a 1.25" but it does the job. 

 

Edited March 26, 2022 by wookie1965

[rnobleeddy]

Interesting thread. I have a 1.25" lunt wedge and a 1.25" continuum filter but no longer have a refractor with an aperture <=100mm so I was probably going to buy something for this summer (gotta get the astro fix somehow!).

I'd settled on a 72mm apo as this would also fill a gap in my current focal range, but looks like a cheap Startravel 102 would be worth considering too.

 

 

[Rustang]

1 hour ago, rnobleeddy said:

Interesting thread. I have a 1.25" lunt wedge and a 1.25" continuum filter but no longer have a refractor with an aperture <=100mm so I was probably going to buy something for this summer (gotta get the astro fix somehow!).

I'd settled on a 72mm apo as this would also fill a gap in my current focal range, but looks like a cheap Startravel 102 would be worth considering too.

 

 

Although you don't necessarily need a scope with all the bells and whistles for Solar, I was told the Startravels still aren't really the best so maybe keep an eye out for something a little better second hand. 

Edited March 27, 2022 by Rustang

[Stu]

1 hour ago, rnobleeddy said:

Interesting thread. I have a 1.25" lunt wedge and a 1.25" continuum filter but no longer have a refractor with an aperture <=100mm so I was probably going to buy something for this summer (gotta get the astro fix somehow!).

I'd settled on a 72mm apo as this would also fill a gap in my current focal range, but looks like a cheap Startravel 102 would be worth considering too.

 

 

The Lunt 1.25” can be used in larger scopes, what do you have? It’s true that the fast achros are not the best for solar as they can often show quite a bit of spherical abberation. A well figured longer focal length achro like a 102 f11 would likely give better results, so long as you have a suitable mount.

[rnobleeddy]

8 minutes ago, Stu said:

The Lunt 1.25” can be used in larger scopes, what do you have? It’s true that the fast achros are not the best for solar as they can often show quite a bit of spherical abberation. A well figured longer focal length achro like a 102 f11 would likely give better results, so long as you have a suitable mount.

I'm down to just a 115mm Altair wave triplet at the moment. The lunt wedge has a pretty clear warning about only being able to dissipate the heat up to a 100mm scope for the 1.25" version. Does anyone have experience otherwise?

[Stu]

1 hour ago, rnobleeddy said:

I'm down to just a 115mm Altair wave triplet at the moment. The lunt wedge has a pretty clear warning about only being able to dissipate the heat up to a 100mm scope for the 1.25" version. Does anyone have experience otherwise?

Yes, plenty. There are various threads on here about it. I’ve used a 1.25” Lunt wedge in a 120ED with no problems. In the U.K. climate I can’t see any issues, the spot on the back doesn’t get that hot. If you were at high altitude in a very hot climate it might be worth more consideration. I’ve heard of people using them in 150mm scopes without problem. Ultimately you have to make your own decision of course. I use a Baader CoolWedge now just for info.

[rnobleeddy]

2 minutes ago, Stu said:

Yes, plenty. There are various threads on here about it. I’ve used a 1.25” Lunt wedge in a 120ED with no problems. In the U.K. climate I can’t see any issues, the spot on the back doesn’t get that hot. If you were at high altitude in a very hot climate it might be worth more consideration. I’ve heard of people using them in 150mm scopes without problem. Ultimately you have to make your own decision of course. I use a Baader CoolWedge now just for info.

Thanks - I hadn't really thought to google that, but the idea had crossed my mind.