Aaaaahgghhh - thanks anyway Peter - it's going to hard to get tthat past SWMBO though
Don't worry Andy... around 1200mm FL with 10"-12" aperture, on a modest and importantly affordable mount, coupled with a lower cost small pixel but sensitive camera, may well cause the more financially secure to feel tired...but the proof is out there and easy to find, that shows such a combo does pretty damn well on small faint extended objects, especially if it is also fast ...just look at Ray's (Shiraz) images
Holy Dooley - If you ever wanted any proof that sub length is irrelevant and its total exposure time that counts, this is it. And its still only 33 mins total.
Forget the cheap and nasty Aldi gear, get a $3/4 Million 0.8m scope and put it in a $1/2 Million observatory up in the Andes and pay $50K a year to have it there yaaay ...or hey, THIS is a steal at $1/2 Million
Hope that was useful advice Andy, good luck with your decision
Mike
Last edited by strongmanmike; 13-09-2017 at 09:31 PM.
Forget the cheap and nasty Aldi gear, get a $3/4 Million 0.8m scope and put it in a $1/2 Million observatory up in the Andes and pay $50K a year to have it there yaaay ...or hey, THIS is a steal at $1/2 Million
Hope that was useful advice Andy, good luck with your decision
Mike
Even if one purchased such instrument and installed it on the top of the highest mountain, somewhere there will always be a better scope with better skies...: http://www.spaceflightinsider.com/wp...ht-Insider.png
Hi Greg - my take on that piece of advice was that since Andy already owns the camera (v. expensive) and mount (also expensive) he should use the Barlow (cheap) to see if (1) his mount is up to guiding at long focal length, and (2) what the image scale and local seeing delivers at around 1.2m focal length before buying a new imaging ota (v. expensive) that may require another mount (v expensive) or camera.
I don't think anyone was suggesting it as an alternative final solution!
Cheers
Andrew.
Ah yes it would be a good test. I have done some APO galaxy imaging using a Tak 1.6Q extender on a TEC180. I imaged the Sombrero. It looked reasonably good but the subs were not very bright at all. In my case the mount held up well (Tak NJP mount) but that mount was maxed out by the refractor so results could be variable.
Even if one purchased such instrument and installed it on the top of the highest mountain, somewhere there will always be a better scope with better skies...: http://www.spaceflightinsider.com/wp...ht-Insider.png
Wow that's a great scene that Suavi huh?...can't wait till it launches
Sorry Andy....no more OT, now get yourself that $Miilion scope
Even if one purchased such instrument and installed it on the top of the highest mountain, somewhere there will always be a better scope with better skies...: http://www.spaceflightinsider.com/wp...ht-Insider.png
Re original OP....
I used a 320mm f5 (1560mm fl) - Canopus 320 for many years in the 80's to visually check many, many of Greg Thompson's initial draft "Supernovae search charts" down to 15.5 mag. Generally a 12.5mm UO Ortho eyepiece....
Would be interesting to see how this would perform with today's CCD's.
Re original OP....
I used a 320mm f5 (1560mm fl) - Canopus 320 for many years in the 80's to visually check many, many of Greg Thompson's initial draft "Supernovae search charts" down to 15.5 mag. Generally a 12.5mm UO Ortho eyepiece....
Would be interesting to see how this would perform with today's CCD's.
Assuming the optics are well corrected, quite well I'd expect. Imagers such as Shriaz certainly have pushed into the outliers of what is possible at that FL.
A big budget is hardly germane to the discussion as Rolf (across the pond) has proven time and again.
The fact remains, galaxies typically have small angular sizes and are faint.
Many of us don't have the luxury of time or clear weather to gather the data hence using a big scope simply makes sense.
Seriously though, I have just ventured along this path of large aperture, fast f ratio with small pixels. What prompted me along this path was the results Mike gets with his system. I found typically I was doing three times the amount of imaging time and a lot of the time not getting quite the same results. That was in dark, still skies with an AO.
However, this type of imaging is not without its own problems. Fast Newtonians require coma correctors and those can be very sensitive to tilt. Not to mention any other flexure that can occur in a fast Newtonian. Narrowing down the problems can be time consuming if you can't afford an expensive scope which already has most of these issues resolved. The system has to hold collimation well and there has to be no movement in the focuser. Even expensive focusers can have slight slop. It can be a bit of a mine field with cheaper gear but it can work if you persist.
Overall, I think the image scale debate has been settled and I am a late convert to the concept. Fast imaging speed with good guiding is the way to go.
Seems that I'll need at least f5.6 or less, and 1000mm at absolute minimum, with an ota being whatever the max load my EQ6 will hold, with the QSI WSG8 in place.
That reduces some of the options, affordability being the last one - can't see me spending more than $2k on this, and that will mean parting with my WO FLT 110 first.
Not sure about metal bodied Newts either, as the temperature/focus thing would do my head in,
So that means either a carbon fibre ota or maybe Glen's idea of a Mak Newt which also eliminates the need for coma correctors as Paul mentioned.
Hey Andy, just out of interest, this is what a fast well tuned and collimated 10" F5 Newt, mounted on an EQ8, in good sky conditions with a small pixel, sensitive camera and in competent processing hands, can deliver
Hey Andy, just out of interest, this is what a fast well tuned and collimated 10" F5 Newt, mounted on an EQ8, in good sky conditions with a small pixel, sensitive camera and in competent processing hands, can deliver
Beautiful - I've always been a fan of Ray's work - his gear delivers good bang for the buck too!
Thanks for posting Mike
Ya not wrong! That was not up in tbe Atacama either. Did you check out the full res why would you feel you need 2500mm + FL when 1200mm can produce this? .... with the right camera, you just dont.
I am not totally convinced of these arguments. I have both types of scopes - the AP Honders 305 F3.8 1159mm focal length scope and a Planewave CDK
17inch 432mm aperture scope at 2936mm focal length.
The Honders is better at widefield. It can do galaxies well with small pixels (Sony 694 sensor) but I get a better result from the CDK. I have seen Peter Wards images with similar setups show the same results.
It may be more the aperture rather than the focal length but there is a point where large aperture is hard to physically handle without being in a more compact form like an RC or CDK etc. A 17 inch Newt would be very hard to handle and wind prone as well.
Perhaps its the old adage "aperture rules" at work more than the focal length but the 2 concepts are really intertwined.
Small pixel cameras come with their own baggage as well. Small wells, Sony
CCDs are more prone to fixed pattern noise too.
I am not totally convinced of these arguments. I have both types of scopes - the AP Honders 305 F3.8 1159mm focal length scope and a Planewave CDK
17inch 432mm aperture scope at 2936mm focal length.
The Honders is better at widefield. It can do galaxies well with small pixels (Sony 694 sensor) but I get a better result from the CDK. I have seen Peter Wards images with similar setups show the same results.
It may be more the aperture rather than the focal length but there is a point where large aperture is hard to physically handle without being in a more compact form like an RC or CDK etc. A 17 inch Newt would be very hard to handle and wind prone as well.
Perhaps its the old adage "aperture rules" at work more than the focal length but the 2 concepts are really intertwined.
Small pixel cameras come with their own baggage as well. Small wells, Sony
CCDs are more prone to fixed pattern noise too.
Greg.
Let's look at this way. The RC12 with a 9 micron pixel sensor gives me an image scale of 0.76" per pixel. The Newt 12 with 5.4 micron pixels gives me an image scale of 0.92" per pixel. The Newt 12 image is smaller for any given target but so far it appears the resolution looks very similar to me. Both scopes are physically a similar size, in fact GSO used the same truss system for both scopes except they put a secondary cage on the top of the RC truss. So up to 12" I'd say the argument is null and void. Over that size then you have a point. I am not a fan of tubes in general and long tubes do get caught by the wind, so there lever arm and gravity to contend with. And; the point has been well made here, not many people can really afford a 30-50K OTA. If you have the money that is all well and good. I personally cannot afford an F8 CDK or RC over $10,000 so I needed to find a faster solution to the problem. I put a fast Newt on a great mount and I think once I have it firing it will produce similar results to both Ray and Mike. They both have the newer sensors but the results should be similar in resolution.
The long and short of it is, if you want to spend that sort of money on a scope, then go for your life. If you are happy with that sort of imaging speed, so be it. If you want faster you need to consider other options. Andy, I think if you look along the 10" newt path that should serve you well here. As Rob pointed out he has a 10 Newt and he gets good results. He has to do a bit of work to sort it out but now the results are coming forth.
...just look at Ray's (Shiraz) images 
.... with the right camera, you just dont.
