12" f/3 Newtonian - any reviews?

[alpal]

I found an interesting Newtonian -
TS 12" f/3 ONTC Newtonian 1/6 Lambda - Carbon Tube - tailor made.

http://www.teleskop-express.de/shop/product_info.php/info/p4976_TS-12--f-3-ONTC-Newtonian-1-6-Lambda---Carbon-Tube---tailor-made.html

It only weighs 17Kgs & is not as long as my 14Kg 8" f/6 Newt. with it's heavy tube rings
so I reckon I would get away with using it on my modified NEQ6 pro mount.

F3 sounds really interesting.
It will collect 9 times more light per square unit than my 8" f6 Newt.
That would get me 9 x faster results.

I am wondering about diffraction spikes.
I bet Alnitak would go right across the frame of the horse head nebula?
Maybe it would need a curved spider?

I also wonder about focusing at f3?
Maybe it just wouldn't work without an electric focuser?

Can anyone find any pictures taken with one or any review?
Does anyone know anything about this scope?

Note:
there is also a 10" version:
http://www.teleskop-express.de/shop/product_info.php/language/en/info/p5798_TS-10--f-3-ONTC-Newtonian-1-6-Lambda---Carbon-tube---tailor-made.html

cheers
Allan

[glend]

Allan I reckon that the coma would drive most imagers crazy at F/3 regardless of the benefits, and collimation would also be a constant headache. As to the weight, there are much lighter alternatives if you have some ATM skills - my 10" f/5 imaging newt OTA only weighs 12.6kg, uses carbon fibre struts. There are a fair number of exotic designs emerging in the market but you have to consider the night to night use and management of the setup. The quest for ultra low F numbers is nuts in my opinion, and not worth the alledged benefits in exposure time savings. For imagers who are setup to guide their mounts the potential of shorter subs is not that great an attraction to justify the probems you would buy into at F/3.

[alpal]

Hi Glen,
thanks for your reply.
I don't agree that it is nuts to consider f/3.
That scope is a carbon fiber tube which should give high stability
for collimation - it's not a cheap scope.
The bad weather & lack of time means only fast instruments
can collect enough data in the short time windows opened.

I wrote to TS & they have no pictures taken with this f/3 scope.
I have written again as I don't want to be a guinea pig.

One problem is my RCC1 coma corrector which is designed for f/4 to f/7.
Even the ASA 2" Coma Corrector Quattro 1.175x they recommend
says it works only from from f/4 to f/6.
My KAF8300 chip has a diagonal of only 22.5 mm - not too large.
I think the RCC1 would still work -
see mine here:
https://www.flickr.com/photos/24719437@N03/8029429824/in/photostream


I'd love to see some result pics.

cheers
Allan

[alpal]

I had to guess a few figures but I still processed the design with
Newt for windows 3.1 by Dave Keller.
The results are in the attached pic.
It looks like the 2" focuser they supply is too narrow.
Any ideas?

Also - just out of interest:
Contrast factor = CF = 5.25 - 5.1x - 34.1x²+ 51.1x³

where x is the obstruction ratio = 3.94/12 = 0.328 = 32.8%

therefore:
Contrast factor = 1.71.
Unobstructed = 5.25.



cheers
Allan

[OzEclipse]

Check out the Newton Corrector on Philipp Keller's site
http://www.astrooptik.com/

I believe this corrector or something very similar is used for the Boren Simon Powernewt scopes.

http://www.teleskop-service.de/astrofotos-teleskope-von-ts/200mm-powernewton/astrofotos.htm

Joe

[alpal]

Thanks Joe,
none of those correctors are recommended for f3.
I think they would all give eggy stars at the corners.

cheers
Allan

[clive milne]

If I had a microline camera I would go for a Rowe Ackerman astrograph instead.

[rmuhlack]

how about the Televue Paracorr? Looks like it works down to f3
http://www.televue.com/engine/TV3b_page.asp?id=61&Tab=_phot#.VJUkcDAMCw

[strongmanmike]

Mirror Optics are same as for my scope and ASA's N series in fact (except mine are 1/10 Lambda ;)) :thumbsup:

Good luck taming it properly though, probably need to be a handy tinkerer :)

Mike

[alpal]

Maybe but I forgot one thing till now:
My QHY9 camera requires 70 mm of back focus when used with a TS9 OAG.
An OAG is essential with my NEQ6 pro modified mount.

My project with my 8" Newt. was only saved by the extra long back focus RCC1.
It has 91.5 mm of back focus.
see here:
https://www.flickr.com/photos/24719437@N03/8029429824/in/photostream

All the ASA correctors & the Televue Paracorr have too little back focus.
It worked out well for me with the RCC1 as it also screwed into
a Varilock spacer which allowed me infinite adjustment of the spacing.

The QHY9 camera has a long nose piece which makes it waste back focus to the camera chip.

It means that none of the ASA Newts. or these other Newts will be suitable for me.
They need 3" focusers with expensive correctors that don't have enough back focus.

Does anyone have some ideas?


cheers
Allan

[alpal]

Yes Mike - I have a feeling that only microns of movement would put the collimation out at f3.

[gregbradley]

You'd be better off getting an Orion Optics UK AG scope like Mike's. Is there much of a price difference by the time you add in a proper corrector, 1/10th wave mirror, extra rings for the focuser?

You can make adapters to get rid of the nose piece on your camera.

Greg.

[alpal]

Hi Greg,
would such an adaptor still include the optical window?
I wouldn't want to run the camera without that.

My mount is not good enough to hold an OTA like Mike's.
This is starting to get too expensive -
new mounts, new correctors etc.


cheers
Allan

[alpal]

Hi Greg,
I'd probably be better off with something like this which would work
with all the equipment I have now:

http://www.teleskop-express.de/shop/product_info.php/language/en/info/p5034_TS-10--F4-UNC-Newtonian-Telescope---optimized-focus-position---Carbon-tube.html



TS UNC 10" f/4 Newtonian telescope with German made carbon tube and 2" ACUN focuser
... Aperture 250mm - Focal length 1000mm - with optimized focus position for maximum illumination
... 94% reflection high quality diffraction limited optic - each telescope is tested on our optical bench
... only ca. 11kg weight with cradle rings!


I could always upgrade the mirrors & other parts at a later date for more performance.
At least it's light too!


cheers
Allan

[alpal]

I just checked out the TS UNC 10" f/4 Newtonian.
using Dave Keller's Newt for windows 3.1.

(Luckily I have a Win XP laptop to use the program because it won't run on a modern 64 bit operating system.)

I found that even that needs a larger focuser than a 2'"
There was 75% vignetting of the rays at the front aperture & the focuser.
I also notice that other 10" f4 systems use a 3" or larger focuser.

My 2" RCC1 coma corrector goes deep inside the focuser so even that would cause vignetting.
I need to use that RCC1 so that I can use my QHY9 + filter wheel + OAG = 70mm of back focus.

What is going on?

cheers
Allan

[Peter.M]

Dont worry so much about the 75% rays, what you want to do is get the 100% rays covering your chip. Also you need to set your focuser camera travel to the backfocus of the camera outside of the focuser. Here is a 12 inch f3 design from newt for the web (which means you dont need to use the software you can just run the webpage version) using 55mm camera backfocus you will need a 3 inch focuser and a 120mm secondary.

Why not look at reducing a more modest scope with the ASA reducer corrector?

Here is the website btw
http://stellafane.org/tm/newt-web/newt-web.html

[alpal]

Peter,
Hi Peter,
thanks for all the work you did there.
It proves the 12" f/3 can't work with a 2" focuser as I thought -
& neither can the 10" f/4.

Notice TS sells Newts. with the bigger focusers:
http://www.teleskop-express.de/shop/product_info.php/language/en/info/p5647_TS-10--f-4-ONTC-Newton-Teleskop---Carbon-Tubus---Ma-anfertigung.html

It doesn't matter what option I choose I am still
unable to use my QHY9 camera because of the back focus problem.
No 1:1 corrector has 70mm of back focus.

I don't think I can upgrade.

By the way I checked my 8" f/6 Newt. om Dave Keller's program
& it comes up as a perfect system.

cheers
Allan

[alpal]

This is very strange:
http://www.optcorp.com/qhy-9-mono-with-kaf-8300-and-5-x-36mm-filter-wheel-qhy9.html

If you look at the QHY9 camera there is no nose piece in the optical train.
They say that it has a back focus of 35mm.

Then they show a picture of the camera with a nose piece.

My back focus with my QHY9 is about 70mm with
the nose piece, filter wheel & OAG.
This means that I can't use it with the available 3" coma correctors.

Can anyone explain this?

( PS - I wrote to OPT to ask them )

cheers
Allan

[rustigsmed]

hi allan,

not sure if this will help you out? did you have a moonlite focuser?

http://www.teleskop-express.de/shop/product_info.php/info/p5903_TS-Optics-2-5--Wynne-Newton-coma-corrector-0-95x-without-changing-the-fous-point.html


cheers,

rusty

[alpal]

Thanks Rusty,
once again 66.6mm of back focus.

The nose piece on the QHY9 is too long to allow for that.
I need 70mm.

cheers
Allan

I have written to a guy called Bern who may have shorter nose pieces available.

see this thread:
http://stargazerslounge.com/topic/127055-strange-streaking-stars-on-outer-edge-of-my-pictures/page-2

QUOTE:
I just got off the phone to Bern at Modern Astronomy and he has a batch of short nose pieces which were made especially for this scenario, i.e:

QHY9 / Protective glass chamber / QHY filter wheel / Nosepiece / Skywatcher reducer.


Maybe he can help?

cheers
Allan

[Peter.M]

I used a qhy9 with an oag and a mpcc. I got precise parts to make a adaptor from the filter wheel to the camera with a length of about 1mm. With this you get 16mm from chip to fw 21m fw 11mm tsoag9 then I needed a 5 mm adaptor from the fw to the oag and I was at around 55mm.

I still think the .73 reducer corrector would be a better option for a super fast newt because it does not impact the secondary size

[alpal]

Hi Peter,
you must have removed the nose piece to do that?

cheers
Allan

[Peter.M]

If you mean the optical window that usually goes between the filter wheel and the camera , yes I don't use that

[alpal]

OK - that explains it.

I didn't want to go down that path so that the inside of my camera is not exposed to humidity.

cheers
Allan

[gregbradley]

Diffraction limited is 1/4 wave. Orion Optics (who make the mirrors for this scope anyway) offer a 1/10th wave mirror. I think that would be important. F4 is probably a little more forgiving and less "fiddle factor" and bug chasing involved. This is supposed to be a relaxing hobby!

Greg.

[alpal]

Thanks Greg,
What about the QHY9 mono cameras?

I wonder if they can be re-engineered to give a shorter back focus?
Someone may be selling shorter nose pieces -
I have yet to find out.

Maybe a few mm could be taken off the front of the camera
by reducing the housing in some way -
& another few on the thickness of the filter wheel?

QHY should have done this anyway.
Unless I can solve the back focus problem I can forget upgrading to any other Newt.

I don't want to remove the nose piece.
As you can see from the picture below I have used the QHY9's proper
desiccant barrel which attaches to the side of the camera
to remove any moisture from inside the camera.
They can't tell you at QHY to do that &
also tell you that you can run it without the nose piece.
The desiccant wouldn't work.

Don't get me wrong -
the QHY9m camera is great -
it's just not designed for Newts. where you need to use a larger than 2" focuser.

For 2" focusers:
The 2" RCC1 solves that problem by giving it 91.5mm of back focus to play with.


cheers
Allan

[rustigsmed]

Hi allan,

which OAG and filterwheel are you using? it may be easier getting a thinner version of either of these to achieve the correct CC spacing?

Rusty

[graham.hobart]

Watching this thread with interest as next year will be assembling what I think will be FLI microline/ SX FW and OAG/ MPCC coma corrector all on f4 Newt.
I hope!!!
Graham

[alpal]

Hi Rusty,
My image train is here:

https://www.flickr.com/photos/24719437@N03/8029429824/

It's a TS9 OAG - 0nly 9mm of back focus.
The filter wheel is the QHY9 standard 5 filter design.

cheers
Allan

[alpal]

Hi Graham,
That's good,
Hopefully the FLI camera will have less back focus problems?
Will it work with a 3" focuser/coma corrector?

cheers
Allan

[rustigsmed]

hi Al,

obviously you can't get thinner than the TSOAG9, I can't find the width of the standard CFW?
as you only need about 3mm maybe the new ultra thin CFW2 may work? http://www.optcorp.com/qhy-medium-ultraslim-7-position-36mm-filter-wheel-qhycfw2-mus.html (17mm).

Rusty

[gregbradley]

Its thin at 17mm but it looks like the adapters that go on each side may attach to the outside of it (the holes for screws?).

So that will lose the thinness advantage (it may add 10mm or more?). The FLI filter wheel has a recessed area for the adapters and the CFW 4/5 is 20mm thick.

Greg.

[gregbradley]

The FLI Microline 8300 has 16mm of back focus (the chip is 16mm inside the camera in other words). The SX Mini USB filter wheel is about 53mm from one side of the adapter to the sensor surface of a FLI Microline with a 50mm male threaded adapter (I am not sure if that is the SCT adapter they refer to on their website).

So if the scope has 90mm backfocus it should have room for the MPCC within that.

The SX Mini USB filter wheel seems well built plus a built in OAG would be really handy.

My usual setup is an Astrodon MMOAG which is very solid and a reliable unit but it takes about 35-40mm of backfocus. The FLI CFW 4/5 takes up 20mm or a tad less.

Greg.

[alpal]

Hi Rusty,
I just made a rough measurement with my measuring tape &
my 5 filter , filter wheel is 18.5mm across - the main section.
That is not allowing for any coupling distance.
It is difficult to compare without an engineering drawing of both units.

cheers
Allan

[alpal]

Hi Greg,
as I said they should supply an engineering drawing of both units.
I can't find a drawing that compares them.

cheers
Allan

[alpal]

HI Greg,
The FLI Microline 8300 looks like a better design.

cheers
Allan

[alpal]

I got an email back from TS.
They reckon you do what Peter has done & run the QHY9 without
the nose piece because the filter wheel & coma corrector are left in place & protect the camera from dust -
I don't know whether it's air tight from moisture.

cheers
Allan

[alpal]

Update:

I have written to Theo at Gamma about the QHY9m use with a 3" focuser & coma corrector.

I await his reply.

cheers
Allan

[multiweb]

The QHY9 mono is a pretty small sensor so you don't need a huge corrected imaging circle. You'll be alright IMHO.

[alpal]

Thanks,
The design of both the 12" f/3 & the 10" f/4 seemed to call for a larger focuser -
a 3" type otherwise there was 75% vignetting at the focuser.
Maybe I'd get away with it using only a KAF8300 chip with a 22mm diagonal?


Anyway Theo replied & it's ok to remove the nose piece & connect
the QHY9m camera directly to the filter wheel.
Then I gain another 15mm at least giving me 70mm - 15mm = 55mm of back focus.

This corrector:
http://www.teleskop-express.de/shop/...orr--Feld.html (http://www.teleskop-express.de/shop/product_info.php/language/en/info/p5091_ASA-3--Wynne-Newton-Koma-Korrektor-0-95x---50mm-korr--Feld.html)

A 3" type from ASA - top quality - allows 58mm of back focus
so I would have 3mm up my sleeve to place spacers.

Removing the nose piece only causes more power to be used to cool the camera
as it must cool a greater quantity of air.
On hot days I might not be able to reach the -30°C I have been using - maybe only -15°C .


cheers
Allan

[gregbradley]

Attaching reducers/correctors on any CCD cam would go directly on the filter wheel with an adapter of the correct width to match the distance required by reducers (flatteners seem more flexible).

Not sure what you mean by removing the nosepiece reduces cooling power. The air in the enclosed CCD chamber is the only air being cooled.

Greg.

[alpal]

Hi Greg,
Removing the nose piece allows the air inside the filter wheel to heat the CCD chamber.




For anyone who wants to help?


Getting back to this Newt:
http://www.teleskop-express.de/shop/...fertigung.html (http://www.teleskop-express.de/shop/product_info.php/language/en/info/p5647_TS-10--f-4-ONTC-Newton-Teleskop---Carbon-Tubus---Ma-anfertigung.html)

I am trying to see if it would actually work with my QHY9 camera & a 2” focuser?
The QHY9 has only a 22 mm diagonal – quite a small frame.
That would save me a lot of money as I have all the 2” accessories: OAG, coma corrector etc

I used this program on the web:
http://stellafane.org/tm/newt-web/newt-web.html

Please see the attached picture – see that there are many problems..
I don’t have all the right dimensions to plug into the calculator so I had to guess some e.g
tube inside diameter
tube thickness.

I need the right dimensions to use the 2” focuser?
I have asked TS.



Starlight 2" Feather Touch with dual speed ... no price change

http://www.teleskop-express.de/shop/...ges/5383_0.jpg (http://www.teleskop-express.de/shop/images/product_images/thumbnail_images/5383_0.jpg)

That focuser made in the USA is one of the best and most stable focusers for Newtonian telescopes in 2" with a very low profile. We recommend that masterpiece of engineering for the use with heavier cameras and accessories. The overall height of the focuser including the basis is only 45 mm which results in perfect illumination of standard camera sensors.
Maybe I can get away with the 2" focuser?

cheers
Allan

[alpal]

I have discovered something about the 10" f/4 Newt. design:

There is a Russian guy on the Cloudy Nights forum who wins many competition called Oleg Bryzgalov.
He is using a Tevevue Paracorr-2 coma corrector with 55mm of back focus on a 10” f/4 Newt.
It shows that a 2” focuser can be used for a KAF8300 sensor..
He has a 79 mm secondary mirror. ( 3.1” )
see here:
http://www.cloudynights.com/topic/48...t-submissions/ (http://www.cloudynights.com/topic/483779-december-14-cn-imagingsketching-contest-submissions/)

https://www.flickr.com/photos/olegbr/15987950961/

The RCC1 that I want to use is not quite as good but may still work.
At least it has a longer back focus.

It would not be as good as an ASA Newt. with a 3" focuser.

Now - back to the 12" f/4 -
still studying that.

cheers
Allan

[rustigsmed]

hi al,

are you looking at 12" f3 or f4?
if you were looking at f4 cf have you seen this?

http://www.teleskop-express.de/shop/product_info.php/language/en/info/p6362_GSO-12--f-4-Newton-Teleskop-mit-Carbon-Tubus---made-in-Germany.html

cheers

[alpal]

Yes - the 12" f/4 is too heavy for my mount - for imaging.
A 10" f/4 is lighter than what I have now.

I think my plan would be to get a sandwich mirror for a 10" f/4 then have
the ultimate modern assembly.
It would be ahead of anything else for sale.

cheers
Allan

[glend]

If your looking at a 10" f4 why all the research on the 12" f3? Is that topic now closed?

[alpal]

No - the original idea was to get a review on the 12" f/3.

It later seems that a 10" f/4 would be a safer bet.

What is your opinion?

cheers
Allan

[glend]

Well given all the issues raised and discussed re the12" yes I believe the 10" f/4 is more mainstream and easier to setup - thus the 'safe' bet.

[alpal]

Hi Glend,
This thread is now finished.
The 12" f/3 was too much of a gamble.

I have ordered the cheaper Carbon fiber 10" f/4 Newt. with the electric focuser option.
see here:
http://www.teleskop-express.de/shop/product_info.php/language/en/info/p5034_TS-10--F4-UNC-Newtonian-Telescope---optimized-focus-position---Carbon-tube.html

I believe it only has GSO mirrors but they are checked.
I intend to upgrade the mirror to a 10" f/4 sandwich or honeycomb mirror from Hubble optics
but that will take up to 6 months delivery.

That way I get a carbon fiber Newt. with low weight & low coefficient of expansion
& up to 10 x faster cool down to ensure the boundary layer of air is at the same temp as the mirror.
The 10" f/4 is 3 Kg lighter than my 8" f/6 Newt so very nice on my modded EQ6 mount.

If I find there is too much vignetting of the flats then I may change to a 3" focuser & the ASA coma corrector:

http://www.teleskop-express.de/shop/product_info.php/language/en/info/p5091_ASA-3--Wynne-Newton-Koma-Korrektor-0-95x---50mm-korr--Feld.html


This will be a nice upgrade from an 8" f/6 Newt.
I have calculated - considering the size of the secondary mirrors that I will
have system where the 10" f/4 will collect 3.35 times the light per unit area in the same time.
That means 3 minute sub frames now in 54 seconds with only a slightly shorter focal length : 1200mm to 1016mm.



cheers
Allan & thanks to everyone for all your help.

[Rac]

If you want a good 10" f4 mirror then look at a Royce conical. No mirror cell and super stable. I use one with a Televue Paracorr 2.

[alpal]

I want to try a sandwich mirror which is not available from Royce -
see here:
http://www.iceinspace.com.au/forum/showthread.php?t=129366

cheers
Allan