John Noble:
Piers,
Firstly I'm jealous of your Bortle 3 skies I live in Detroit now under Bortle 7 skies but grew up in Northumberland and remember with fondness the Bortle 3 skies out by my parents house!
I suspect many of us have been on this journey before and there are no right or wrong answers. What I've found is that with the small pixel 2600 cameras once the focal length gets above 600 or so mm other factors control the details one can capture: seeing, mount capabilities etc. So for example I have a WO FLT132 which is f7 native or I can reduce it down with my 0.72 reducer. For me at least the reduced version loses nothing on detail and is faster therefore I always use that set up as I get more light per exposure which ultimately helps my SN.
Also as far as binning goes, as far as I am aware, it works with CCD's but not so well with CMOS, others I'm sure have the math so whether I'm at 1400 mm fl, 0r 660 mm I always bin 1x1. Some have issues with file size and binning makes sense for them but that's not an issue I've ever had.
Bottom line use whichever scope you prefer, or that fits the desired field, but don't expect much change in details once your up over a pixel scale of 1.2 to 1.4. Do remember though that f5 will gather twice the light than f7 in a given time - which really matters in light polluted skies but may be less important to you. That's the reasoning I keep in my head every time I'm tempted to buy yet another scope usually a 10" f4 Newt!!!
Hope that helps
John
I've often been tempted by Northumberland because of the slightly better weather and the beaches....oh the beaches! Detroit - blimey, that's a contrast!
So in a simplistic interpretation of your guide, if I assume my sky stability and camera are fixed, the ideal scope would be the fastest scope with a focal length of around 600mm. I know speed isn't so important with my dark sky, but it is when you consider the scarcity of clear nights.
Or I could move.
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Piers Palmer:
John Noble:
Piers,
Firstly I'm jealous of your Bortle 3 skies I live in Detroit now under Bortle 7 skies but grew up in Northumberland and remember with fondness the Bortle 3 skies out by my parents house!
I suspect many of us have been on this journey before and there are no right or wrong answers. What I've found is that with the small pixel 2600 cameras once the focal length gets above 600 or so mm other factors control the details one can capture: seeing, mount capabilities etc. So for example I have a WO FLT132 which is f7 native or I can reduce it down with my 0.72 reducer. For me at least the reduced version loses nothing on detail and is faster therefore I always use that set up as I get more light per exposure which ultimately helps my SN.
Also as far as binning goes, as far as I am aware, it works with CCD's but not so well with CMOS, others I'm sure have the math so whether I'm at 1400 mm fl, 0r 660 mm I always bin 1x1. Some have issues with file size and binning makes sense for them but that's not an issue I've ever had.
Bottom line use whichever scope you prefer, or that fits the desired field, but don't expect much change in details once your up over a pixel scale of 1.2 to 1.4. Do remember though that f5 will gather twice the light than f7 in a given time - which really matters in light polluted skies but may be less important to you. That's the reasoning I keep in my head every time I'm tempted to buy yet another scope usually a 10" f4 Newt!!!
Hope that helps
John
I've often been tempted by Northumberland because of the slightly better weather and the beaches....oh the beaches! Detroit - blimey, that's a contrast!
So in a simplistic interpretation of your guide, if I assume my sky stability and camera are fixed, the ideal scope would be the fastest scope with a focal length of around 600mm. I know speed isn't so important with my dark sky, but it is when you consider the scarcity of clear nights.
Or I could move.
Fast means nothing, per se. What is important is field coverage and image scale. This said, with the dearth of clear skies we suffer in the UK (even here in the east) sacrifices shall be made so a fast large aperture is the way to go.
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Yes but!!!
I guess for a mere mortal with sparse clear skies and no permanent observatory it’s a solid yes. Clearly others with better locations and observatories do amazing things with larger apertures. I just haven’t seen the benefit of imaging below 1” per pixel. I sold my Edge HD 8 last year and now just use my FLT132 for galaxies 660 mm from the back yard and 910 mm if I’m at a dark sky site like yours. Everything is easier in my opinion!
John
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andrea tasselli:
Fast means nothing, per se. What is important is field coverage and image scale. This said, with the dearth of clear skies we suffer in the UK (even here in the east) sacrifices shall be made so a fast large aperture is the way to go.
I've read and read on the "benefits" of fast scopes and everything I read makes sense, whether that being that they're a godsend or that they're unnecessary. From what I've seen with my SD81, f7.7 is fine to use as an imaging scope.
By the way, I didn't realise you lived in the UK....I assumed you were in Italy. Sorry!
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John Noble:
Yes but!!!
I guess for a mere mortal with sparse clear skies and no permanent observatory it’s a solid yes. Clearly others with better locations and observatories do amazing things with larger apertures. I just haven’t seen the benefit of imaging below 1” per pixel. I sold my Edge HD 8 last year and now just use my FLT132 for galaxies 660 mm from the back yard and 910 mm if I’m at a dark sky site like yours. Everything is easier in my opinion!
John
Sometimes I look at Nambia and wonder if I could live there. I'd probably treat myself to a permanent set-up if I lived somewhere like that.
I would love to be happy with one scope so perhaps my SD81 is ideal. It's 625mm at its native f/7.7 and 495mm with the reducer. There's a 103mm and a 115mm equivalent too which I could use my flattener/reducer on, but perhaps I don't need to push the focal length and the increase in aperture might not be that beneficial for AP either. I 'm pretty good at persuading myself to buy something new though.
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Piers Palmer:
Sometimes I look at Nambia and wonder if I could live there. I'd probably treat myself to a permanent set-up if I lived somewhere like that.
I would love to be happy with one scope so perhaps my SD81 is ideal. It's 625mm at its native f/7.7 and 495mm with the reducer. There's a 103mm and a 115mm equivalent too which I could use my flattener/reducer on, but perhaps I don't need to push the focal length and the increase in aperture might not be that beneficial for AP either. I 'm pretty good at persuading myself to buy something new though.
I sure could live a La Palma and image from there. This said, there is no substitute to aperture. Even in Namibia (which isn't all it is cracked up to be, mind you).
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andrea tasselli:
I sure could live a La Palma and image from there. This said, there is no substitute to aperture. Even in Namibia (which isn't all it is cracked up to be, mind you).
Ah yes, La Palma, the seat of the Spanish side of the family!
There's no substitute for aperture....up to a point where the image scale can't be supported by the seei...it's a complicated game this!
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Piers Palmer:
Ah yes, La Palma, the seat of the Spanish side of the family!
There's no substitute for aperture....up to a point where the image scale can't be supported by the seei...it's a complicated game this!
Not really, otherwise there wouldn't be 8/10 meters scopes out there (and 30 meters planned) when the seeing is rarely better than 1" and the Fried parameter is 20 cm at best. There's always the benefit once deconvolution comes into play. But, apart from that, it is a matter of having the right image scale for you seeing. I have a 30 cm and get by with a 0.8"/px and always have better readings than 6 cm sitting besides. Both are fast f/4 scopes.
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True; I was meaning with the constraints I have, and given the camera I use something like a 12" f/4 (assuming I could mount it) might not be worth the effort....for now anyway!
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Hi everybody,
just came about that thread and I thought I could give my five cents, because I‘m using the same setup like Piers - the R200SS with the Extender PH at f/5.6. I‘m living in south western Germany about 50km east of Stuttgart and my sky is Bortle 4-5.
Here is an image I was taking of M81/M82 about two years ago. The camera was an uncooled Canon 760Da with similar pixel size. Processing is far from being perfect, but I could reprocess the data or provide the master light here for comparison.
I‘m also having data obtained with my Tak Sky90 at f/4.5 with a Canon 6Da here.
Piers, it seems we‘re having very similar setups.
CS
Ulli
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Piers, it seems we‘re having very similar setups.
We do (you're the reason I went for the extender!) but that's where the similarity ends...you're better than me! I definitely need to try and increase my integration time, but the weather here isn't entirely helpful in that respect.
Both look fantastic to me, they're very different shots and the R200SS clearly pulls out more detail. Interesting!
How old is your R200SS?
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Piers Palmer:
How old is your R200SS?
Actually, I don‘t know. I own it at least third hand. It has the old focuser with the foam inside and, in fact the scope was cheaper than the ExtenderPH and the CorrectorPH  |
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2.15
7.56
3.31
0.90
