#21  
Old 03-05-2021, 02:25 PM
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strongmanmike (Michael)
Woohoo it's clear

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You don't need big long focal lengths to get decent detail in your galaxy and PN (or any other object) images, just match the focal length with an appropriate size pixel, buy the largest aperture you can afford, then be lucky enough to have some reasonable seeing, easy

To add to the other good examples already posted too ilustrate what's possible (I second looking at Lee Borsbooms images!), the following extreme close up crops, were all done at the native prime focus, 1120mm FL of a fast 12inch F3.8 Newt, with a small pixel camera, providing 0.84"/pix image scale (no lucky imaging used, just straight 5-15min exposures, stacked), from just outside Canberra, so reasonable seeing conditions generally.

As you can see, plenty of detail can be discerned

NGC 6872

Shapely 1

The Southern Crab

NGC 1566

Good luck with your (confusing ) quest

Mike
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  #22  
Old 04-05-2021, 01:19 PM
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alpal
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Quote:
Originally Posted by strongmanmike View Post
You don't need big long focal lengths to get decent detail in your galaxy and PN (or any other object) images, just match the focal length with an appropriate size pixel, buy the largest aperture you can afford, then be lucky enough to have some reasonable seeing, easy

To add to the other good examples already posted too ilustrate what's possible (I second looking at Lee Borsbooms images!), the following extreme close up crops, were all done at the native prime focus, 1120mm FL of a fast 12inch F3.8 Newt, with a small pixel camera, providing 0.84"/pix image scale (no lucky imaging used, just straight 5-15min exposures, stacked), from just outside Canberra, so reasonable seeing conditions generally.

As you can see, plenty of detail can be discerned

NGC 6872

Shapely 1

The Southern Crab

NGC 1566

Good luck with your (confusing ) quest

Mike



Hi Mike,
your pics bear testimony to the fact that you don't need
long focal length to take great pictures.
Of course you correctly mention lucky imaging as being an exception -
we only need to see Anthony Wesley's images with Barlow lenses added to see that.
http://www.acquerra.com.au/astro/


cheers
Allan
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  #23  
Old 04-05-2021, 03:51 PM
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strongmanmike (Michael)
Woohoo it's clear

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Quote:
Originally Posted by alpal View Post
Hi Mike,
your pics bear testimony to the fact that you don't need
long focal length to take great pictures.
Of course you correctly mention lucky imaging as being an exception -
we only need to see Anthony Wesley's images with Barlow lenses added to see that.
http://www.acquerra.com.au/astro/


cheers
Allan
Aaah yes, if only there were more deep sky objects as bright as planets

Mike
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  #24  
Old 04-05-2021, 04:16 PM
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alpal
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Aaah yes, if only there were more deep sky objects as bright as planets

Mike



Well - there is the Homunculus Nebula.
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  #25  
Old 05-05-2021, 08:14 PM
kosborn (Kevin)
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I don't think I'll have the patience that Discoduck has though (50hrs), and I'm not game like Kosborne to go a 10" mirror on an eq6r pro, at least not yet while im still playing nice with the mount.
I'm very late to the conversation but thought I'd add my recent experience.

I started with an Esprit 100ED about 3 years ago and wanted to add more focal length. I thought carefully about adding an 8" RC but in the end decided to go for a high end Newtonian. I was nervous about the size and weight of the Newt (and it really does look top heavy in the attached pic) but it actually works well on the EQ6-R as long as there isn't too much breeze. I was equally nervous about the collimation and the big f number of an RC. A Newtonian is infinitely easier to collimate than a Ritchey-Chretien!

I dither every sub and lose a lot of time waiting for the scope to settle, but I live in a Bortle 4-5 suburb of Canberra and don't have to throw away too many subs. The Newt is a 254mm f/5 carbon fibre tube from Sidereal Trading and I've added OAG to reduce weight as much as possible. It weighs in at 17kg with imaging train which is a lot for an EQ6-R but it all seems to work. With a Baader MPC Mk III coma corrector it gives me a great flat field edge to edge and the focal length of 1270mm together with an ASI1600mm and ASI2600MC (and with the Esprit with or without a Starizona 0.65 reducer) gives me a great range of focal length and framing options.

The bottom line is don't underestimate what you can get with a good quality Newtonian!
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Last edited by kosborn; 05-05-2021 at 09:37 PM.
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  #26  
Old 05-05-2021, 09:18 PM
Startrek (Martin)
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Originally Posted by kosborn View Post
I'm very late to the conversation but thought I'd add my recent experience.

I started with an Esprit 100ED about 3 years ago and wanted to add more focal length. I thought carefully about adding an 8" RC but in the end decided to go for a high end Newtonian. I was nervous about the size and weight of the Newt (and it really does look top heavy in the attached pic) but it actually works well on the EQ6-R as long as there isn't too much breeze. I was equally nervous about the collimation and the big f number of an RC. A Newtonian is infinitely easier to collimate than a Ritchey-Chretien!

I dither every sub and lose a lot of time waiting for the scope to settle, but I live in a Bortle 4-5 suburb of Canberra and don't have to throw away too many subs. The Newt is a carbon fibre tube from Sidereal Trading and I've added OAG to reduce weight as much as possible. It weighs in at 17kg with imaging train which is a lot for an EQ6-R but it all seems to work. With a Baader MPC Mk III coma corrector it gives me a great flat field edge to edge and the focal length of 1270mm together with an ASI1600mm and ASI2600MC (and with the Esprit with or without a Starizona 0.65 reducer) gives me a great range of focal length and framing options.

The bottom line is don't underestimate what you can get with a good quality Newtonian!
Couldn’t agree more , except I use basic entry level newts and have done so since I started this hobby just over 4 years ago
6” f6 Bintel newt on an EQ6-R mount in Sydney for AP
8” f5 Bintel newt on an EQ6-R mount in my NexDome on the South Coast NSW for AP
12” f5 Skywatcher Goto dob for visual on the South Coast NSW
My next scope for AP at some stage in the future will definitely be a 10”f5 newt
Never really looked at refractors when I first got into the hobby. As a novice , I thought they were just too expensive compared to newts , so I just stuck with newts and have done ever since.
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  #27  
Old 08-05-2021, 09:02 AM
Emuhead
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Originally Posted by kosborn View Post
I'm very late to the conversation but thought I'd add my recent experience.

I started with an Esprit 100ED about 3 years ago and wanted to add more focal length. I thought carefully about adding an 8" RC but in the end decided to go for a high end Newtonian. I was nervous about the size and weight of the Newt (and it really does look top heavy in the attached pic) but it actually works well on the EQ6-R as long as there isn't too much breeze. I was equally nervous about the collimation and the big f number of an RC. A Newtonian is infinitely easier to collimate than a Ritchey-Chretien!

I dither every sub and lose a lot of time waiting for the scope to settle, but I live in a Bortle 4-5 suburb of Canberra and don't have to throw away too many subs. The Newt is a 254mm f/5 carbon fibre tube from Sidereal Trading and I've added OAG to reduce weight as much as possible. It weighs in at 17kg with imaging train which is a lot for an EQ6-R but it all seems to work. With a Baader MPC Mk III coma corrector it gives me a great flat field edge to edge and the focal length of 1270mm together with an ASI1600mm and ASI2600MC (and with the Esprit with or without a Starizona 0.65 reducer) gives me a great range of focal length and framing options.

The bottom line is don't underestimate what you can get with a good quality Newtonian!

I bought the 8" Quattro f4 800mm and haven't taken it off. Absolutely love the thing and its speed, and i have a 550mm refractor that I've not yet used because i like the longer focal length, and I cant fault the newt. Grown to really like diffraction spikes too.

So a 10" mirror on an eq6r (f4 or f5) is not too heavy after all, I'm hearing more & more from people who have done it successfully. Just might consider that.. 1000mm f4 or 1200mm f5 is the question, guess this thread has shown it makes no difference to detail/resolution as long as the pixel scale still falls in the sweet spot, it'll be the exact same image if cropped to match, so may go the f4 route for the speed & to keep the windsail size down.

Last edited by Emuhead; 08-05-2021 at 09:17 AM.
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  #28  
Old 08-05-2021, 03:51 PM
kosborn (Kevin)
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Originally Posted by Emuhead View Post
So a 10" mirror on an eq6r (f4 or f5) is not too heavy after all, I'm hearing more & more from people who have done it successfully. Just might consider that.. 1000mm f4 or 1200mm f5 is the question, guess this thread has shown it makes no difference to detail/resolution as long as the pixel scale still falls in the sweet spot, it'll be the exact same image if cropped to match, so may go the f4 route for the speed & to keep the windsail size down.



I've done everything I can to save weight on the Newtonian including carbon fibre tube and OAG. Wind is still the killer though. If you go f/4 keep in mind what you'll use as a coma corrector. I think Andy had a Sidereal 1000mm f/4 with a Paracorr which actually has a 15% Barlow effect. I think that means he was actually imaging at 1150mm and f/4.6, not much different to my 1270mm and f/5. I use a Baader MPCC III which can be used at f/5 and above and leaves the focal length and f ratio unaltered. I don't know if there are coma corrector options for Newtonians faster than f/5 that leave the focal length unchanged... I think in general an f/5 Newtonian is cheaper than an equivalent f/4 (and the Baader is cheaper than the Paracorr). Obviously a 1000mm Newt has less length than a 1270mm Newt when it comes to windsail but I don't know how much difference that extra 270mm actually makes in real life.


Kevin

Last edited by kosborn; 08-05-2021 at 05:01 PM.
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