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Old 14-12-2010, 03:21 PM
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allan gould
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New scope advice needed

OK, I have finally retired and Im sure I need a new imaging scope. At present I'm using a 10" SCT with an f6.3 focal reducer. After messing around with the spacing I can cover the qsi593wsg chip without vignetting but the qhy8 chip shows significant vignetting.
The scope I want has to ride on a losmandy g11 and should be for a limit of approx 10K. Still haven't told SWMBO but it could be a surprise for her!!!!
I'm open to all suggestions except in the refractor area as I have a 5" apo that nicely covers both chiles without vignetting. I'm mainly interested in DSOs and nebulae (the 5" covers the latter).
Thanks for you time.
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Old 14-12-2010, 04:48 PM
Alchemy (Clive)
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What sort of FL do you think you would like, that might narrow it down a bit.
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Old 14-12-2010, 06:01 PM
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multiweb (Marc)
ze frogginator

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Quote:
Originally Posted by allan gould View Post
OK, I have finally retired and Im sure I need a new imaging scope. At present I'm using a 10" SCT with an f6.3 focal reducer. After messing around with the spacing I can cover the qsi593wsg chip without vignetting but the qhy8 chip shows significant vignetting.
The scope I want has to ride on a losmandy g11 and should be for a limit of approx 10K. Still haven't told SWMBO but it could be a surprise for her!!!!
I'm open to all suggestions except in the refractor area as I have a 5" apo that nicely covers both chiles without vignetting. I'm mainly interested in DSOs and nebulae (the 5" covers the latter).
Thanks for you time.
Looks like you're covered for the night. Get yourself a nice solar scope?.
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Old 14-12-2010, 07:09 PM
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h0ughy (David)
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Alan,
slightly bigger but will ride on the g11 - what about a new c11 HD and get a hyperstar - then that leaves you some change to get a qhy10? then you can image at F10, F6.3, and f2
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Old 15-12-2010, 06:56 PM
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I think the best way to approach which scope you should get is to work backwards from the type of images you want to produce.

As Clive mentioned - what focal length do you want to shoot at? What type of images do you prefer?

An all round best compromise focal length seems to be about 1300mm in my opinion. Mike's AP152 with its flattener shoots at that and so does my TEC180.
For example this image was taken with a FLI ML8300 (same chip as the 583) and the TEC180 at 1260mm. This image is cropped but you can see the image scale you will achieve with that focal length. It suits a LOT of objects. Wodaskis CCD calculator (free) is very good at showing what image scale you will get with different scopes and camera combos. Try downloading that and seeing which focal length/F ratio you find pleasing with an 8300 chip.


The next thing I think is important is F ratio and that of course implies aperture.

If you have decided around 1300mm focal length then the lowest F ratio you can get is best or in other words the largest aperture you can get is the best. F10 is pretty rough to image at and the images with a 583 camera will be super zoomed in. The images will require lots and lots of exposure time as you are capturing such a small segment of the sky. F5 to me is an ideal F ratio and if I can't get that then as close to it as I can. I have had several scopes around F5 and they have been very good for imaging.

Next consideration that limits the above is how much weight can my mount handle accurately?

There was a carbon fibre tubed, feathertouch focuser, installed fans for cooling Vixen 260 on Astromart recently for $4000 or less. That seemed a bargain. I think it even came with a reducer. It is light, well made, consistently gets good reviews and your G11 would handle it well.

It is the formula that seems to work for imaging - 2 mirrors and a corrector or an APO and a high quality reducer or flattener.

A 10 inch Newt with a Wynne corrector and around F5 would be one choice.

One approach is to see what equipment people are using that you like the images of. And then narrow that down to what will a G11 handle. I imagine a 10 inch lightweight Newt may be the limit for accurate guiding.

Greg.
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Old 15-12-2010, 07:44 PM
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Screwdriverone (Chris)
I have detailed files....

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I noticed a North Group ED127 on Ice Trade, will this do?

Good price too.

Cheers

Chris
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Old 15-12-2010, 08:06 PM
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Thanks for all the imput but for now Ive spent the dollars on automating my observatory. The guys at Sirius observatories were excellent, helpful and took my money without hesitation.
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Old 16-12-2010, 10:45 AM
TrevorW
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10" GSO Carbon Fibre RC

and still have change
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  #9  
Old 16-12-2010, 02:52 PM
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allan gould
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Quote:
Originally Posted by TrevorW View Post
10" GSO Carbon Fibre RC

and still have change
I heard you the first time.

That had crossed my mind but I'm not as brave as Houghy. Will have to think deeply and practises the art of belly crawling a little more intensely.
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