avx Overloading an AVX with a 9.25SCT + guiding set up?

[Adaaam75]

Hi guys and girls,

So I've decided on a 9.25" SCT for my upgrade as initially I want to continue visual observations whilst dabbling in imaging with my DSLR. Then I will look to increase my set up. The question I have is would the AVX be capable of dealing with a imaging set up, whether it be a guidescope or off axis guider? Assume I will be using a monochrome CCD camera with filter wheel when I say imaging setup and not my DSLR.

OR should I down size the scope to an 8" as upscaling mount beyond the AVX isnt really an option unless i look at the EQ6. Your thoughts please.

[ollypenrice]

Personally I think you may be underestimating the difficulties of DS imaging with a long focal length SCT. This has precious little to do with weight - which is not the problem, contrary to what you might read - but with the realities of very high resolution imaging where accuracy of autoguiding is the real bugbear.

To be brutally honest an SCT and a DSLR are about as bad a mismatch as you are likely to get. You are in a world of pixels which are far too small and which cannot be binned 2X2 because of the Bayer matrix.

Does it have to be an SCT?

Olly

[Chris]

Hi Adam, you say upgrade, what scope and mount do you have currently?

I don't do much in the way of deep sky image at the moment due to family commitments, but when I did I generally used either short focal length ED refractors, or fast imaging Newtonians, so we are talking about focal lengths around 400-800mm.

The shorter the focal length the easier it is to accurately track an object you're trying to image. An anology would be it's easy to hold out your arm and keep your finger still, but try holding out a pool que at arms length and keeping the end of the que still!! This is how increasing focal length works with tracking the night sky. 

Now I did move to using an AVX mount and a C8 Edge HD for imaging in my then observatory, and that scope has a native focal length of 2000mm f10. I brought this down using a 0.7 reducer to around 1400mm f/7. I used an old Canon 350D which has really chunky pixels in order that I wasn't oversampling, I think I was imaging at around 1 arcsecond per pixel, and typical seeing conditions in the UK are probably more like 2 arcseconds per pixel so I would have still been over sampling other than very good nights of seeing. 

So basically from what I've said above you can see that I had a little bit of imaging experience under my belt, and I'd thought about matching a camera to the scope. Even so this really didn't prepare me for how hard it was, and I don't think I ever got anything decent image wise to show for my efforts with that combination.

in a nutshell, my C8 Edge was a wonderful scope, gave me some of the best visual views of planets and globular clusters I've had out of a scope I've owned,  really nice compact light bucket of a scope.....great for high frame rate planetary imaging.....but for deep sky imaging there are much easier options out there, especially for folks starting out in DSO imaging. 

The C9.25 would be even harder because that has an even longer focal length!

The other thing about long focal length deep sky imaging is that objects get framed very tightly on your imaging chip, even an APC sized sensor, so it can be tricky finding the objects to image on the chip in the first place even with goto!

If you have deep sky imaging in mind, I would seriously consider either an ED or Apo refractor, or a fast f/5 Newtonian before going the SCT route. Not just my opinion but my experience

[Adaaam75]

Chris/Olly,

Your concerns and sound advice to genuinely care about another member of this site is a testament to the users and guys who run SL. I may have been slightly brief with my description of what I intend to do because I didn't want to rabble on only to not receive any replies. Quite simply, I am a visual observer who has taken a couple of shots of the moon and want my next scope to be the biggest apature I can afford (I can hear your sighs!) because I won't be buying another large scope again due to the cost of them. I should go back slightly, I currently have a SW 130p on an EQ2 mount. She has served me well and I've followed the correct advice (I think!) by learning the night sky before getting a "Guided" tour without having to think about where everything is. If I was not currently constructing my observatory (pier last dependant on scope!) and was purely only ever going to be a visual observer then I'd be getting a large struss Dob.

However with my desire to also take images my train of thought was to get my visual scope set up, enjoy the sights and my new toy for a while (a couple of years even) and also dabble with attempts at imaging the moon/Jupiter/Saturn to get a feel for the set up and the beginnings of processing shots. I have done this already on my SW 130p and my moon montages are pleasing but without any kind of tracking I am restricted.

So as I already have a decent DSLR I thought the moon etc would be a good itch to scratch whilst I considered my next "wish list" of imaging gear. I take the cue stick analogy and your efforts to get a decent image with the EdgeHD on board and I do get how difficult DSO are to capture. I will never expect to be a DSO champion but my overall plan for DSO after purely researching on this site is to eventually invest in something similar if not the actual SW 80ED refractor as I am now aware of the huge advantages of this over a SCT. Considering my future expense and knowing I'd not be able to purchase an 80ED and all the imaging equipment at the same time I thought I could start with the 9.25" AVX for my main interest and then look at the imaging set up to continue with the solar system still very aware of the difficulties of DSO before then considering the 80ED. 

As I'm sure most astronomers can appreciate, if I had the money I'd go and buy the perfect visual set up AND the perfect imaging set up but I'm not a lottery winner nor in a job that would ever allow this so it's a slow transition for me. So whilst I'm aware the weight on the mount is only one of many issues, to me it is relevant for where I am at the moment as I'm looking at the scope and mount. I know the 80ED and imaging set up would be fine on the AVX but I'm more concerned with the 9.25". If I'm only imaging solar system objects (moon, Jupiter etc) with my DSLR would the AVX still have an issue with just guiding or would I still need the imaging set up? I've read mounts can still produce good results with short guide times (5 mins) for targets such as planets etc.

So plan, 9.25" AVX for visual

Play with my DSLR

Look at DSO imaging set up with CCD etc and then push the boat out and become a 3 scope family with an 80ED by which time my 3 year old son will (hopefully) be well and truly addicted too!

[Adaaam75]

On 06/20/2016 at 22:30, Chris Lock said:

Hi Adam, you say upgrade, what scope and mount do you have currently?

I don't do much in the way of deep sky image at the moment due to family commitments, but when I did I generally used either short focal length ED refractors, or fast imaging Newtonians, so we are talking about focal lengths around 400-800mm.

The shorter the focal length the easier it is to accurately track an object you're trying to image. An anology would be it's easy to hold out your arm and keep your finger still, but try holding out a pool que at arms length and keeping the end of the que still!! This is how increasing focal length works with tracking the night sky. 

Now I did move to using an AVX mount and a C8 Edge HD for imaging in my then observatory, and that scope has a native focal length of 2000mm f10. I brought this down using a 0.7 reducer to around 1400mm f/7. I used an old Canon 350D which has really chunky pixels in order that I wasn't oversampling, I think I was imaging at around 1 arcsecond per pixel, and typical seeing conditions in the UK are probably more like 2 arcseconds per pixel so I would have still been over sampling other than very good nights of seeing. 

So basically from what I've said above you can see that I had a little bit of imaging experience under my belt, and I'd thought about matching a camera to the scope. Even so this really didn't prepare me for how hard it was, and I don't think I ever got anything decent image wise to show for my efforts with that combination.

in a nutshell, my C8 Edge was a wonderful scope, gave me some of the best visual views of planets and globular clusters I've had out of a scope I've owned,  really nice compact light bucket of a scope.....great for high frame rate planetary imaging.....but for deep sky imaging there are much easier options out there, especially for folks starting out in DSO imaging. 

The C9.25 would be even harder because that has an even longer focal length!

The other thing about long focal length deep sky imaging is that objects get framed very tightly on your imaging chip, even an APC sized sensor, so it can be tricky finding the objects to image on the chip in the first place even with goto!

If you have deep sky imaging in mind, I would seriously consider either an ED or Apo refractor, or a fast f/5 Newtonian before going the SCT route. Not just my opinion but my experience

Chris could you give me your thoughts on my last post please ?

[uhb1966]

Hello Dear Adaam,

i am also a noob but i dont think that you really have to differentiate between visual and AP. You can have setups that are good for both. I do believe, however , that the focal length should match your preferred targets, ie longer focal length for planets, shorter fl for deep sky...

[Adaaam75]

1 hour ago, uhb1966 said:

Hello Dear Adaam,

i am also a noob but i dont think that you really have to differentiate between visual and AP. You can have setups that are good for both. I do believe, however , that the focal length should match your preferred targets, ie longer focal length for planets, shorter fl for deep sky...

Hi!,

I appreciate that, however the difference I was referring to was the added physical weight of the extra imaging equipment on The AVX mount. Visually I'd only have the scope on the mount but imaging brings lots more additions and I am looking for advice on the AVX dealing with the 9.25" SCT plus the imaging set up of a CCD camera......

Any thoughts?

[uhb1966]

The max weight limit for the avx is 14kg, and you usually should use only 50% for imaging. We need the weight of the SCT, of the ccd, and i have my doubts about deep space imaging with the SCT...

Chris summed it up nicely above : "... I generally used either short focal length ED refractors, or fast imaging Newtonians, so we are talking about focal lengths around 400-800mm."

That is the generally accepted wisdom, and i do believe you should not deviate far from that.

A nice 8'' inaging newton weights about 10kg, which is also great for visual, but will be stretching the AVX. With a fast 4'' precision refractor, you should be way below the weight limit (3-5kg), but i am not sure about its visual performance.

A very nice refractor could be the  "TS Photoline 80mm f/6 Triplet Super-Apo with FPL53 triplet" (only 3.2kg!) , and a nice imagingnewton could be "Skywatcher QUATTRO-8S " -10kg without finder scope - search for it in SGL's search function for reviews...

All in all, if you'd like to stick to your avx, I'm afraid you will have to go for a smaller, fast refractor like the one mentioned above... with only 3kg for the OTA, you'll have ample load for all the rest of your gear.

 

[Adaaam75]

On 06/26/2016 at 08:46, uhb1966 said:

The max weight limit for the avx is 14kg, and you usually should use only 50% for imaging. We need the weight of the SCT, of the ccd, and i have my doubts about deep space imaging with the SCT...

Chris summed it up nicely above : "... I generally used either short focal length ED refractors, or fast imaging Newtonians, so we are talking about focal lengths around 400-800mm."

That is the generally accepted wisdom, and i do believe you should not deviate far from that.

A nice 8'' inaging newton weights about 10kg, which is also great for visual, but will be stretching the AVX. With a fast 4'' precision refractor, you should be way below the weight limit (3-5kg), but i am not sure about its visual performance.

A very nice refractor could be the  "TS Photoline 80mm f/6 Triplet Super-Apo with FPL53 triplet" (only 3.2kg!) , and a nice imagingnewton could be "Skywatcher QUATTRO-8S " -10kg without finder scope - search for it in SGL's search function for reviews...

All in all, if you'd like to stick to your avx, I'm afraid you will have to go for a smaller, fast refractor like the one mentioned above... with only 3kg for the OTA, you'll have ample load for all the rest of your gear.

 

Yeah I have been educated in DSO with SCT's since looking into the subject. My main aim is to get the scope and mount and enjoy visual observations. I will then go for the solar system imaging set up before taking the plunge on the 80ED for DSO. Re the solar system imaging on my SCT 9.25, would the AVX cope with a DSLR set up or should I look at the EQ6 which has a higher maximum payload of 50 lbs and would therefore be better suited? Is one better than the other?

[PeterCPC]

I use my C9.25 on an AVX for planetary imaging - normally with a planetary camera but I have used my Canon as well. No problems. My album contains some planetary images  and my avatar is from that.

Peter

[uhb1966]

I do own the EQ6, but i was considering the AVX as well. I guess the avx is lighter and therefore easier to carry into and out the garden, carries less weight and is more affordable - the EQ6 carries more weight, but is also much heavier and pricy-er. I guess that apart from that, the differences shouldnt be too great. If you really want the SCT, why dont you get it and try the setup ? If it works as in PeterCPC's case,cool, if it doesnt, you sell the avx and get the eq6. The good thing about planetary is you only use very short exposures... wait, even better: maybe somebody that doesnt live too far away uses a similar setup? Maybe you could try it out? That would definitely be the best case!

[Adaaam75]

On 06/30/2016 at 18:58, uhb1966 said:

I do own the EQ6, but i was considering the AVX as well. I guess the avx is lighter and therefore easier to carry into and out the garden, carries less weight and is more affordable - the EQ6 carries more weight, but is also much heavier and pricy-er. I guess that apart from that, the differences shouldnt be too great. If you really want the SCT, why dont you get it and try the setup ? If it works as in PeterCPC's case,cool, if it doesnt, you sell the avx and get the eq6. The good thing about planetary is you only use very short exposures... wait, even better: maybe somebody that doesnt live too far away uses a similar setup? Maybe you could try it out? That would definitely be the best case!

 

[Adaaam75]

My setup is going in my observatory and onto a fixed pier for a permanent set up so weight and portability isn't an issue. I'm thinking my 9.25 SCT with Canon DSLR for planetary solar system imaging and when I'm ready to shell out, I'll get a decent refractor. The SW 80ED seems a very popular choice on here, unless you guys are members of the Sky Watcher sales team!

[Adaaam75]

On 06/30/2016 at 14:31, PeterCPC said:

I use my C9.25 on an AVX for planetary imaging - normally with a planetary camera but I have used my Canon as well. No problems. My album contains some planetary images  and my avatar is from that.

Peter

Peter I am new here, how do I view your album to see what is achievable with a DSLR and 9.25" SCT on an AVX?

 

[des anderson]

Lots of sound advice from everyone.I have a AVX and 9.25sct and its housed in an observatory,BUT,I would`nt` go down the DSO imaging route,far to many problems.Planets and the Moon its a great bit of kit and gives very pleasing results.Des

[Adaaam75]

14 hours ago, des anderson said:

Lots of sound advice from everyone.I have a AVX and 9.25sct and its housed in an observatory,BUT,I would`nt` go down the DSO imaging route,far to many problems.Planets and the Moon its a great bit of kit and gives very pleasing results.Des

Des that sounds exactly the same as what i am looking at acheiving, I am going to build my observatory in the next couple of months and am in the design process from converting a 3.5 x 2.5m shed. I am favouring the 9.25" SCT on the AVX on a pier. Any hints/tips?

[PeterCPC]

16 hours ago, Adaaam75 said:

Peter I am new here, how do I view your album to see what is achievable with a DSLR and 9.25" SCT on an AVX?

 

If you click on my avatar and then on album you can see my planetary pics using the AVX and 9.25 with a planetary camera. This is an image using my Canon with the same set up.

Peter

[Nuka]

Hi Adam,

I have had the C9.25 on the older Advanced GT mount (owned for about 4 years) and was very happy for both visual and occasional AP with my Canon DSLR. I also now own the AVX mount so i'm very confident you will have no issues with the weight of the C9.25 OTA. I started without the focal reducer and so was imaging at the full F10 and i still got some decent results of the Orion Nebula, Jupiter and Saturn. Tracking was pretty good for shortish exposures but using the F6.3 focal reducer helps massively! Visually it's a lovely scope and wow Jupiter was very sharp and detailed on good nights with the right eyepiece.

Obviously this setup is not ideal for long exposure AP but you can certainly get a taste for it and i'm sure you will enjoy the experience along the way.

Nuka

[alacant]

Hi. I don't know anything about the mount you mention but even unguided, the 9.25 with a dslr seems like a great choice. My f5 toy can't get anywhere near as close as that. Guided, it should be great for all those galaxies that are unthinkable for the big-nebula-ed80 guys. HTH.

[ollypenrice]

37 minutes ago, alacant said:

Hi. I don't know anything about the mount you mention but even unguided, the 9.25 with a dslr seems like a great choice. My f5 toy can't get anywhere near as close as that. Guided, it should be great for all those galaxies that are unthinkable for the big-nebula-ed80 guys. HTH.

Before we get too excited about 'getting close' we need to think about pixel scale and resolution. If we put an 1100D, for the sake of argument, in the back of a C9.25, we are trying to image at 0.45 arcseconds per pixel. Well best of luck, but using a premium mount at a premium site I wouldn't even consider this. It is not attainable. If we put an ED80 in front of the same camera we get a resolution of 2.14 "PP and that is attainable. What is really maximally attainable lies betxeen the two. The fact that you get a 'close up' image in a long FL on a DSLR means nothing whatever. What matters is, does it contain any more detail than a shorter FL image? If it doesn't, then you just upsample and crop the galaxy in your shorter FL image and get the same result.

For DS imaging putting a DSLR in the back of a C9.25 is, frankly, a waste of field of view. You won't get any more detail than you'd get at a shorter focal length with a wider field of view so why do it? That's without getting into how much light lands on each pixel.

Olly

[Tiny Small]

55 minutes ago, ollypenrice said:

Before we get too excited about 'getting close' we need to think about pixel scale and resolution. If we put an 1100D, for the sake of argument, in the back of a C9.25, we are trying to image at 0.45 arcseconds per pixel. Well best of luck, but using a premium mount at a premium site I wouldn't even consider this. It is not attainable. If we put an ED80 in front of the same camera we get a resolution of 2.14 "PP and that is attainable. What is really maximally attainable lies betxeen the two. The fact that you get a 'close up' image in a long FL on a DSLR means nothing whatever. What matters is, does it contain any more detail than a shorter FL image? If it doesn't, then you just upsample and crop the galaxy in your shorter FL image and get the same result.

For DS imaging putting a DSLR in the back of a C9.25 is, frankly, a waste of field of view. You won't get any more detail than you'd get at a shorter focal length with a wider field of view so why do it? That's without getting into how much light lands on each pixel.

Olly

Just to further iterate this:

I'm imaging with a 130PDS with 0.9x CC and a camera with 2.4um pixels. I'm imaging at 0.87"/pixel and this falls just past the dawes limit for my scope (0.89") and is well under average seeing conditions in this country. This is all mounted on an NEQ6. In truth this is perhaps a little past the maximum and if I could get my scope down to around 500mm, my life would be a lot easier. Looking at the images at this resolution, you can see areas where it just can't collect and seperate the detail that you would expect for the scale. It's not a massive amount of detail that I'm missing, but it is noticable on some objects that have very fine detail and it's annoying enough that I'm thinking of swapping to a shorter focal length frac so I can image in the region of 1"/p to 1.4"/p. That's still a tight requirement though. Thankfully, my guiding is pretty good and is aided by ridiculously overmounting the scope. My whole setup weighs about 6kg which is massively below 50% of the recommended imaging weight for my mount.

The point of this is that even though I'm within hundredths of an arc second of the Dawes limit for my scope, I'm losing noticable detail. So image scale is a really important thing to consider. Don't just pay it lip service.

[Chris]

On 6/23/2016 at 09:39, Adaaam75 said:

Chris could you give me your thoughts on my last post please ?

Really sorry for not replying @Adaaam75, I've only just come across your thread several months later. I hope you got on all right deciding what do buy and building the obsy?  

[alacant]

11 hours ago, ollypenrice said:

a DSLR in the back of a C9.25 is, frankly, a waste

Struck me as a great image. An nice big m57 without having to spend hours jumping through hoops. I don't think it's a waste. Certainly not of time; an hour of unguided snaps, 20 minutes to process maybe? It's a hobby and the guy did an experiment. Which worked well. What's wasteful with that?! 

[ollypenrice]

1 hour ago, alacant said:

Struck me as a great image. An nice big m57 without having to spend hours jumping through hoops. I don't think it's a waste. Certainly not of time; an hour of unguided snaps, 20 minutes to process maybe? It's a hobby and the guy did an experiment. Which worked well. What's wasteful with that?! 

I specified 'a waste of Field of view'' so if you edit that bit out of my post you remove my whole point, which is that one can acheive the same real image resolution at a shorter focal length. I most certainly did not say or imply that it was a waste of time or a waste of anything else, just FOV. This was in response to your point that a C9.25 seems like a great choice for a DSLR. I believe the opposite, that is the wrong choice for a DSLR, because the pixels are too small, cannot be binned up to a reasonable pixel scale and will not be able to work to its theorietical resolution because neither guiding nor seeing will be likely to support it. Ergo, a scope with a shorter FL, giving maybe 1.0 to 1.2 arcsecs per pixel, will give the same real resolution across a wider FOV in less time.

You can use most cameras in most telescopes. The thing is to come to some kind of understanding of which combinations of camera and scope are likely to be the most productive. 

Olly

[Adaaam75]

On 10/25/2016 at 17:45, Nuka said:

Hi Adam,

I have had the C9.25 on the older Advanced GT mount (owned for about 4 years) and was very happy for both visual and occasional AP with my Canon DSLR. I also now own the AVX mount so i'm very confident you will have no issues with the weight of the C9.25 OTA. I started without the focal reducer and so was imaging at the full F10 and i still got some decent results of the Orion Nebula, Jupiter and Saturn. Tracking was pretty good for shortish exposures but using the F6.3 focal reducer helps massively! Visually it's a lovely scope and wow Jupiter was very sharp and detailed on good nights with the right eyepiece.

Obviously this setup is not ideal for long exposure AP but you can certainly get a taste for it and i'm sure you will enjoy the experience along the way.

Nuka

Nuka,

Members first hand advice from personal experiences is invaluable and you have given me every confidence in the AVX with the 9.25 SCT. I will be looking at a focal reducer soon after too to reduce imaging times. Thanks for your advice mate.