Help with my setup viewing and photography

[noideasteve]

So i started out with an Nexstar 6SE for viewing and DSO photography, I then sold and helped fund my current setup which is a Advanced VX mount with an HD 8" SCT and guide system. I then wasn't happy with the FOV i was getting but the stars looked amazingly better so i bought the HD Focal Reducer .7x, I'm still not happy with the FOV I'm getting in my photographs. For example if i were to photograph Orion using the focal reducer i have to turn my camera 180 degrees and then i'm only just fitting in the running man nebula but cropping Orions nebula. I would like to be able to fit the two nebulas in one photograph is my aim. I use an DSLR camera with an APS-C sized sensor. 

This is the headache I'm having..... I enjoy the viewing of Planets with the photography of deep space objects hence why i upgraded to the HD with it's optics, now I'm thinking of selling this OTA and changing to a Refractor. I still want to get nice views of planets with the odd now and again image but mostly concentrate on DSO's. The way i see things is if i wanted a wider field of view i could hyperstar the HD 8" but the lens alone will cost me about $1000 and i would also want to upgrade the focuser on the SCT to a feather touch which again is going to add another $300 to the scope (Yes the HD will be sold to outlay the cost of the refractor if im to do it).

I was thinking of going for the Explore Scientific 127mm ED Essential Refractor as my new weapon of choice as it already has a better focuser and is a slightly quicker scope than the native F/10 HD 8" SCT. 

1. How would the refrator compare to my viewing sessions of planets compared to the current HD 8" (All my viewing is done with a 40mm eyepiece and a barlow i have)?

2. What would be the fastest the refractor scope can get down to using focal reducers being it's native F/7.5?

3. Would the images look better (colour and detail) through a refractor than the HD with my DSLR?

4. Would i get a larger field of view in my images using a full frame DSLR camera compared to the APS-C size sensor?

5. Out of the refractors i was also looking at the Skywatcher 120 ED, Out of the two refractors what would be a better choice if i go down that path?

Any advie and help would be great... Thanks in advance.

[ronin]

You have a fairly simple problem that many do:- you have a very nice visual scope and want to use it for astrophotography and it doesn't do it. Putting a DSLR on a visual scope does not by default make it an AP rig.

An AP scope in it's simplest description is a short fast scope, you have a long slow scope.

If money allows keep the SCT and get something like an apo refractor - ED's are doublets so will/can show CA, and use that on the mount for the AP aspect and the SCT for visual.

The one aspect that the SCT will be fine for is planetary imaging, but I think there is one planet to image at this time. so it might get boring after the first 20 images of Jupiter.

Sorry but that is really the situation, you cannot do much more then put a reducer in the SCT and even then it is still a slow scope. You are not going to make the f/10 into an f/5 or even f/6. I would half suspect that a reducer will effect the optical performance of the image also.

The 120ED is still a big long scope - forget BIG, big is for visual not for AP. The 120ED would i think give you some CA and an amount of SA thrown in. Something like an 80mm apo would stuff a 120ED for imaging. My GT-81 will do a far better job then an 120 ED. One good imaging scope around is the WO Star 71. It is not big, it is not long, it is good. You are thinking visual when you want imaging.

[red dwalf]

lots of questions and there and i`m sure i can`t answer all of them fully but your 8" sct edge is a long focal length scope, brilliant for planetary imaging or visual use but unless your going to use a hyperstar there not that good at wide field dso imaging due to the long focal length even with a reducer on,

that's where a good refractor comes in which helps solve a few problems over a sct.

firstly your guiding with the refractor will be easier to get good subs with less trailing.

secondly there's no need for collimation, something that is critical in a sct scope.

next is a bigger field of view as most 80mm reflectors are around 500mm or less in length which is a quarter of the 8" sct.

what i would suggest is a william optics gt 81 or a star 71 or a eqiunox 80, all depends on budget but something which has a short focal length, is well colour corrected and is below f5 would be great.

keep the sct for planetary imaging of visual use as you`ll have every corner covered as this scope is completely the other end of the scale to the fast 80 mm refractors.

one thing that is not needed for good dso imaging is light grasp.

a dlsr or a ccd camera will work perfectly with a refractor, using the dlsr will give you a lot bigger field of view compared to the 8" sct. 

[noideasteve]

Thanks for the input there guys, I think I may just invest in the William Optics 71mm APO It's really not that hard hitting on the budget. Besides the size difference is there much difference between the 71mm and 81mm in the William Optics range in regards to the image quality?

[red dwalf]

i use a gt81 and it`s very nice, but using it with a reducer is a bit of a pain as setting it up with a ccd camera the spacing has to be spot on which is alittle trial and error, no problem using a canon dlsr as a spacer is supplied so it`s just a case of screwing together, the 71 i`ve not used but looks well suited for astro imaging, the reducer / flattener is built in so you don`t get the problems and the camera and focuser all screw together which i prefer.

if you get into narrowband imaging you don`t really need a well corrected scope and your doing one colour at a time so you would focus the channels individually so there`s no real reason a cheaper good quality doublet won`t do the business like the equinox 80.

there`s alot to consider.

i should say that the star 71 is not really a visual scope, just astro photography.   

[noideasteve]

After having a good look at the cost of the 71mm William Optics it's well within my reach and seems like the perfect purchase for my dslr setup. I will then just piggy back the scope to my 8" SCT and use my SCT as the visual / planetary imaging scope and the 71mm William Optics as my wide field DSO imaging only scope. Finally the headaches have subsided and i believe i will will have a setup i'm happy with. 
Oh it just so happens I found out today after talking scopes and telescopic lenses with my dad that he has something hidden away. It's a 11 Element telephoto lens consisting of ED glass, I think he was saying it's an 80mm x 200mm f/2.8. So I'll be borrowing that tomorrow and seeing what kind of images i come up with. Curse him from hiding that lens from me! Well no harm in playing around with a big heavy lens anyway

[Droogie 2001]

Hi,

I am in exactly the same position as you were in Noideasteve.

I have a Celeston 8 SE and whilst I have had limited success with DSO's the FOV is poor as you described with M42. I can just about managed a few of the stars in the Pleiades.

So I am in the market for a short FL refractor and after reading a favourable review in this months Sky at Night magazine I have taken a lot of interest in the WO Star 71.

Have you had chance to image with the WO 71 yet? If so can you give any advice? I have the AVX mount and a Nikon DSLR.
The one area I am unsure on is the M48 T Ring. I have a Nikon T ring but not sure if it will fit the WO tube?

I will also need to purchase the diagonal as well as I have no Live View. I assume this will allow me to align the scope as I currently do with my SCT?

Thanks