Upgrading my setup

[Andreas]

Hey!

I've been using my telescope for about one year and a half now, and I've got very interested in deep sky-photography, which lately have made me thinking of what I could upgrade to get even better results, (except learning to handle the telescope better.)

However, I'm still a newbie, and not really sure about what's worth upgrading at the moment, and what's not.

The scope itself is what I've been thinking most about upgrading, so lets talk about that first.

At the moment I'm using a Sky watcher 250pds, which I've been thinking about to replace with a refractor, but still, I'm not really sure about how much difference it will make in contrast and sharpness etc of the image.

And I might be wrong, but of what I've noticed, many deep sky photographers tend to use refractors, so I guess that the refractors have some kind of advantage when it comes to deep-sky photography?

I've also heard, (which also may be wrong), that refractors generally produce shaper images and don't need coma correctors to remove the coma effect that I suffer from with my scope.

And I mean, there must be some reason for buying a refractor for 2 000£ instead of a reflector for 500£?

So now to the question: What's the difference in quality between my 250pds, and lets say an ED refractor for 1 000£ 'ish, as well as the difference between the ED refractor for 1 000£ and an ED APO for 2 000£?

Is it worth upgrading from my scope to an ED refractor, and what difference would it make, or would it be better to get a better camera instead?

And if its worth, what aperture and focal length should I have?

As I asked about if it's a better choice to upgrade my camera instead of the scope, lets talk about that now.

I use a unmodified Canon EOS 550D DSLR camera at the moment, but what kind of astrocamera would be equivalent to mine, and what difference would it make to the final image?

The astrocameras are as well very expensive even tough their resolution seems low, and I'm not really sure what makes them expensive and what I pay for?

I've also been looking at those filters, like H-alfa and H-beta etc, which looks very interesting indeed, but still, I'm too inexperienced to decide if its worth the money or not, and what difference it would make.

I do also wonder if those filters, as well as the filter wheels works good with my colour DSLR camera, or if I need an astrocamera for this?

I know it's a lot of questions, but you really don't have to answer everything!

All kind of answers are appreciated!

// Andreas

[Steep]

re refractors and coma, I think all scopes are potentially liable to have that problem, with a refractor meant for AP the difference in price comes from better quality glass and coatings. Just as with camera lenses, quality costs.

[Andreas]

re refractors and coma, I think all scopes are potentially liable to have that problem, with a refractor meant for AP the difference in price comes from better quality glass and coatings. Just as with camera lenses, quality costs.

Hi!

Yeah, I understand that quality glass and coatings pump up the costs, but how much difference does it make? Where is the price range where you get out most of the money you spend?

[lensman57]

Hey!

I've been using my telescope for about one year and a half now, and I've got very interested in deep sky-photography, which lately have made me thinking of what I could upgrade to get even better results, (except learning to handle the telescope better.)

However, I'm still a newbie, and not really sure about what's worth upgrading at the moment, and what's not.

The scope itself is what I've been thinking most about upgrading, so lets talk about that first.

At the moment I'm using a Sky watcher 250pds, which I've been thinking about to replace with a refractor, but still, I'm not really sure about how much difference it will make in contrast and sharpness etc of the image.

And I might be wrong, but of what I've noticed, many deep sky photographers tend to use refractors, so I guess that the refractors have some kind of advantage when it comes to deep-sky photography?

I've also heard, (which also may be wrong), that refractors generally produce shaper images and don't need coma correctors to remove the coma effect that I suffer from with my scope.

And I mean, there must be some reason for buying a refractor for 2 000£ instead of a reflector for 500£?

So now to the question: What's the difference in quality between my 250pds, and lets say an ED refractor for 1 000£ 'ish, as well as the difference between the ED refractor for 1 000£ and an ED APO for 2 000£?

Is it worth upgrading from my scope to an ED refractor, and what difference would it make, or would it be better to get a better camera instead?

And if its worth, what aperture and focal length should I have?

As I asked about if it's a better choice to upgrade my camera instead of the scope, lets talk about that now.

I use a unmodified Canon EOS 550D DSLR camera at the moment, but what kind of astrocamera would be equivalent to mine, and what difference would it make to the final image?

The astrocameras are as well very expensive even tough their resolution seems low, and I'm not really sure what makes them expensive and what I pay for?

I've also been looking at those filters, like H-alfa and H-beta etc, which looks very interesting indeed, but still, I'm too inexperienced to decide if its worth the money or not, and what difference it would make.

I do also wonder if those filters, as well as the filter wheels works good with my colour DSLR camera, or if I need an astrocamera for this?

I know it's a lot of questions, but you really don't have to answer everything!

All kind of answers are appreciated!

// Andreas

Hi.

As far as CA is concerned all lenses ,including some highend Apos, exhibit some degree of aberration , the more exotic the glass and the design the less of the CA but as everything else in life particularly photographic, the costs go up exponentially for marginal gains in quality. If you intend to just publish your Astro or DS images on the web, 72 dpi, or just make very small prints and give as present to your friends and family then some degree of CA is acceptable. If, however you are a serious astro photographer and exibit these images or use them for research then I am sorry to say that you are asking the wrong questions here. I urge you to read some of the artcles here under "Astro imaging on a budget" to see the difference in cost and effort between the casual and serious imaging, you will be surprised at how much you can achieve on a reasonable , but still not insignificant, budget. I hope you didn't mind me putting my two pence of advice in.

Regards,

A.G

[Andreas]

Hi.

As far as CA is concerned all lenses ,including some highend Apos, exhibit some degree of aberration , the more exotic the glass and the design the less of the CA but as everything else in life particularly photographic, the costs go up exponentially for marginal gains in quality. If you intend to just publish your Astro or DS images on the web, 72 dpi, or just make very small prints and give as present to your friends and family then some degree of CA is acceptable. If, however you are a serious astro photographer and exibit these images or use them for research then I am sorry to say that you are asking the wrong questions here. I urge you to read some of the artcles here under "Astro imaging on a budget" to see the difference in cost and effort between the casual and serious imaging, you will be surprised at how much you can achieve on a reasonable , but still not insignificant, budget. I hope you didn't mind me putting my two pence of advice in.

Regards,

A.G

Hey!

Yeah, I'm aware of that the costs increases for marginal gains at some point, but of what I've experienced, there's often a limit.

As long as you're above that limit, you're gain pretty much for the money that you've been paying.

However, if you exceed this limit, you pay for smaller and smaller gains, as you mentioned earlier.

And that's what I'm trying to find out right now - the limit of price-worthy.

Ofcourse you do always pay for smaller and smaller gains from the really beginning, but I mean, there's often a point where you get what you pay for, if you know what I mean.

// Andreas

[perfrej]

Image quality wise there isn't that much of a difference. I'd say the refractor is so much easier to handle, though, and the lack of spider vanes and the resulting diffraction spikes is a good thing. For most reasonably priced refractors you will need a field flattener, which coud be looked upon as being the coma corrector for refractors. A 1000-pound refractor with a good flttener will perform very well.

There is also a nice touch of depth in refractor images. I don't know why but they do have a better 3D feel to them. My advice for you is to do one of two things:

1. Keep the PDS until you can afford a really good refractor (a really good refractor is often spelled "Takahashi" and doesn't need a flattener)

2. Buy an 80mm with a good flattener right now

The PDS will keep you in the galaxy league, while an FSQ85 or FSQ106 (or any other refractor) will give you access to the wonderful world of nebulae (and make guiding and tracking easier due to the shorter focal length).

Love my 106

/per

[Andreas]

Image quality wise there isn't that much of a difference. I'd say the refractor is so much easier to handle, though, and the lack of spider vanes and the resulting diffraction spikes is a good thing. For most reasonably priced refractors you will need a field flattener, which coud be looked upon as being the coma corrector for refractors. A 1000-pound refractor with a good flttener will perform very well.

There is also a nice touch of depth in refractor images. I don't know why but they do have a better 3D feel to them. My advice for you is to do one of two things:

1. Keep the PDS until you can afford a really good refractor (a really good refractor is often spelled "Takahashi" and doesn't need a flattener)

2. Buy an 80mm with a good flattener right now

The PDS will keep you in the galaxy league, while an FSQ85 or FSQ106 (or any other refractor) will give you access to the wonderful world of nebulae (and make guiding and tracking easier due to the shorter focal length).

Love my 106

/per

Hey!

I don't think that I have to budget for a Takahashi right now, but I've been looking at some cheaper ones, particularly this one http://www.astrosweden.se/110mm-astro-ed/18640-0.

However, I'm not sure about which aperture or focallenght is the best, or if it's even worth a buy when I already own the PDS?

Maybe I should just buy some narrowband filters and a comacorrector for my PDS and wait with the refractor? Would that be a good investment, for my setup?

I mean, does those narrowband filters work well with a colour DSLR? And if i buy a coma corrector, would I be able to use it later if i buy a refractor?

I'm so confused! What do you think?

// Andreas

[perfrej]

A coma corrector and some filters right if it wasn't for the fact that you don't have monochrome camera. You do not need a Tak to get good images as is evident in the imaging sections of most astronomy forums.

Now, a good starting refractor that is easy to image with should probably around 80mm apreture and as low f-number as possible. f/7 is a bit on the weak side, though. The PDS, with its longer focal length, is a bit more difficult to image with as you would soon find out. I started with a 250P and it was a nightmare in terms of starting experience.

I cannot vouch for the quality of this item, but the specs look like a real good starter refractor for nebulae and larger galaxies. Anyone have any experience with this refractor? http://www.teleskop-service.se/sv/teleskop/refraktorer-apokromater-ed-triplets/ts-optics-80-triplet-fpl53-refraktor.html

/per

[Andreas]

A coma corrector and some filters right if it wasn't for the fact that you don't have monochrome camera. You do not need a Tak to get good images as is evident in the imaging sections of most astronomy forums.

Now, a good starting refractor that is easy to image with should probably around 80mm apreture and as low f-number as possible. f/7 is a bit on the weak side, though. The PDS, with its longer focal length, is a bit more difficult to image with as you would soon find out. I started with a 250P and it was a nightmare in terms of starting experience.

I cannot vouch for the quality of this item, but the specs look like a real good starter refractor for nebulae and larger galaxies. Anyone have any experience with this refractor? http://www.teleskop-...-refraktor.html

/per

Why does not colour cameras work with narrowband filters?

[perfrej]

A coulor camera already has filters on each pixel. Counting from left top and on in the first row, the pixels are usually R,G,G,B,R,G,G,B... and then shifted two steps on the next line. This is called a Bayer Matrix and after the image is exposed, the camera software will use neighboring pixels' values in order to get the other colours. Thus, each pixel will be reported with an R, G and B value that is really not the truth but rather an assumption. The net effect is lower resolution.

Now, add an Ha filter in front of that and you see that the G and B pixels will get absolutely no light at all. Only the red pixels get light, so the sensitivity of the camera becomes 1/4th of the base sensitivity.

Any narrow-band work you want to do needs to be with a monochrome camera so that all pixels are used. Obviously, the monochrome cameras have the same sensor as the colour ones but lack the Bayer Matrix filters in front of the pixels.

You will, of course, find decent images of Ha shot with DSLRs and the likes, but it is very different to doing it monochrome, that's for sure. I'd say you do not want to go there

/per

[Andreas]

A coulor camera already has filters on each pixel. Counting from left top and on in the first row, the pixels are usually R,G,G,B,R,G,G,B... and then shifted two steps on the next line. This is called a Bayer Matrix and after the image is exposed, the camera software will use neighboring pixels' values in order to get the other colours. Thus, each pixel will be reported with an R, G and B value that is really not the truth but rather an assumption. The net effect is lower resolution.

Now, add an Ha filter in front of that and you see that the G and B pixels will get absolutely no light at all. Only the red pixels get light, so the sensitivity of the camera becomes 1/4th of the base sensitivity.

Any narrow-band work you want to do needs to be with a monochrome camera so that all pixels are used. Obviously, the monochrome cameras have the same sensor as the colour ones but lack the Bayer Matrix filters in front of the pixels.

You will, of course, find decent images of Ha shot with DSLRs and the likes, but it is very different to doing it monochrome, that's for sure. I'd say you do not want to go there

/per

Thanks a lot for the good explanation Per!

I've been looking at this one http://www.firstlightoptics.com/atik-cameras/atik-383l-plus.html, what do you think about it?

The size of the sensor looked decent when I checked it's compability with my telescope with a FOV calculator, but I'm still not sure if its the right one for my scope.

And if I later would decide to buy a refractor, lets say an 80 ED, would the sensor size on the 383L be too large then?

I've also been looking at filter wheels, and I wonder if those are really necessary? I've heard that you need to refocus after a change anyway, and that you often only use one filter/night, and they're pretty expensive.

Also, I'm not sure if I can get focus if i have a filter wheel between the camera and the focuser? Because with my 550D, I have to get really close to the focuser to get focus.

What do you think?

// Andreas

[perfrej]

No problemos!

The Atik cameras have a good reputation and many here on SGL use them. One of the heavier guys in this game, Olly Penrice, praises them highly and I do trust his advice even though I do not always follow it Other 8300-based cameras would likely provide slightly better cooling, but hey, you're in the Värmland woodlands anyway where the summer is totally off season due to lack of darkness and the winters are nice and cold, so that's not an issue.

Filter wheels are not that expensive. I have a Starlight-Xpress USB-connected wheel that works very well and it is not that expensive. Filling the wheel with L, R, G, B, Ha, O3, and S2 filter for a camera with a decent size sensor, like the 8300, is going to kick you badly in the behind, though!

Focusing... You will, as this hobby grabs you and your wallet in a firm combined grip, find that getting perfect focus is not a task that a human is fit for (some will disagree). Only a good - and free - advanced software package like FocusMax is going to get you home there. I haven't focused manually for two years...

Your distance to the camera "film plane" may be a bit of a problem, but if you have it reasonably well under control with a DSLR you can get focus with a CCD if you choose the right camera and filter wheel. A standard Canon camera has a distance of 55mm from the flange of the T-adapter to the film plane. 383L+ has 17mm. Add to that 29mm for the filter wheel and a mm for the filter glass and you get 47, which means you are safe with that combination.

/per