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Equipment Discussions >> Reflectors

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sami2012
journeyman


Reged: 03/10/12

What do you recommend 8 inch or 10 inch Newtonian
      #6087341 - 09/18/13 04:57 AM

Hi all,,,,


I am looking to buy a Newtonian for Astrophotography but I between the 8 inch or 10 inch, What do you recommend ???, about the Newtonian fast a F/4 OR F/5 .
regards
sam


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orlyandico
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Reged: 08/10/09

Loc: Singapore
Re: What do you recommend 8 inch or 10 inch Newtonian new [Re: sami2012]
      #6087343 - 09/18/13 05:11 AM

f/4 is better than f/5, both of them would want a coma corrector.

the 8" is always going to be better than the 10" unless you have a capable mount ( = AP900 or comparable).

i have a Mach1 and I got an 8" for it. I don't like over-stressing the mount.


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sami2012
journeyman


Reged: 03/10/12

Re: What do you recommend 8 inch or 10 inch Newtonian new [Re: orlyandico]
      #6087349 - 09/18/13 05:42 AM

i have the neq6 pro mount ,and about Collimation this f/5 hale the time of f/4

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orlyandico
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Reged: 08/10/09

Loc: Singapore
Re: What do you recommend 8 inch or 10 inch Newtonian new [Re: sami2012]
      #6087359 - 09/18/13 06:11 AM

well of course collimation of the f/4 will be harder. but it's almost 1 stop faster for photography (1.56X so a 10-minute sub on the f/4 would be equivalent to a 16-minute sub on the f/5). Both will need a coma corrector for astrophotography.

personally, for an NEQ6 i would stay with the 8". some people put 10" or even 12" on the NEQ6 but i guess they like losing their hair...


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csrlice12
Postmaster
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Reged: 05/22/12

Loc: Denver, CO
Re: What do you recommend 8 inch or 10 inch Newtonian new [Re: orlyandico]
      #6087600 - 09/18/13 09:44 AM

Unless you already have AP experience, I'd not do this...an 8-10" newt, even on an adequate mount is a terribly huge and unweildy beast. You'll not only need a $$$$$mount, but tube rings as well, probably a ladder. AP with this type equipments calls for an observatory.....this is a very, very, expensive road you're getting ready to travel....If you're just starting out, look into the AP forums. You'll still need a good mount, but using a small APO/refractor will still provide you with beautiful images.....and it won't be cheap either, but at least it will be easier to use. You can do some limited (15-45sec) exposures with a smallish APO on a motorized CG5 (or equiv), which is probably going to be as cheap as you can go......and don't forget the camera, adapters, computer, software, and TIME, AP requires Lots and Lots and Lots of time, most of it at the computer......

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orlyandico
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Reged: 08/10/09

Loc: Singapore
Re: What do you recommend 8 inch or 10 inch Newtonian new [Re: csrlice12]
      #6087626 - 09/18/13 09:59 AM

The reason I went for the 8" is because it's f/4 compared to my current f/6.7 APO triplet.

And I also got a Keller reducer which brings it down to f/2.9 - there is no APO out there that can do f/2.9 (the fastest are the Borg 125SD with super reducer, and Tak FSQ-106 with reducer, both for $$$$$ lots of money $$$$$)


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csrlice12
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Reged: 05/22/12

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Re: What do you recommend 8 inch or 10 inch Newtonian new [Re: orlyandico]
      #6087646 - 09/18/13 10:06 AM

Yea, but you've been at this awhile....Be truthful now, would you really recommend a 10" newt for AP to a person with no astronomy or photography experience?????? Now, if I already had some experience and was looking to "upgrade"....

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orlyandico
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Re: What do you recommend 8 inch or 10 inch Newtonian new [Re: csrlice12]
      #6087654 - 09/18/13 10:12 AM

Err, no. That's why I recommended the 8" - the OP says he has an NEQ6 - that's an Atlas for the rest of us.

The 8" is about 22lb and is about 30" long, making it roughly the same footprint as an Orion 100ED. I'm pretty sure an Atlas could carry it competently.

Now the 10" is a totally different story...


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mpgxsvcd
Carpal Tunnel


Reged: 12/21/11

Loc: Raleigh, North Carolina
Re: What do you recommend 8 inch or 10 inch Newtonian new [Re: orlyandico]
      #6087778 - 09/18/13 11:16 AM

I definitely would say that a 10” Newt is probably too much for a lower end mount. However, an 8 inch is a perfectly acceptable solution even for the budget mounts like the CG-5. You just have to spend a few extra minutes getting the balance right and make sure your camera and guide scope are as light as possible.

Collimation is easy. It really isn’t as hard as everyone makes it sound.

The Carbon Fiber Newts are also a lot lighter so that can make a big difference. There is an 8 inch Carbon Fiber Newt under $900 right now.


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SeattleScott
Pooh-Bah


Reged: 10/14/11

Re: What do you recommend 8 inch or 10 inch Newtonian new [Re: mpgxsvcd]
      #6089278 - 09/19/13 12:43 AM

I know a couple guys who started out with AP instead of visual, and they went with an F4 Newt. They soon upgraded to an Atlas mount for it and had considerable success. Yes, they now have a 4" Apo on a Mach1 mount, but the Newt was a satisfying enough experience to launch them down the expensive path of AP.

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orlyandico
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Loc: Singapore
Re: What do you recommend 8 inch or 10 inch Newtonian new [Re: SeattleScott]
      #6089310 - 09/19/13 01:51 AM

This I don't get. I already have the Mach1 and 90mm APO... And I'm going in the other direction. ^_^

There's someone in the local club with an AP 130 that he used for many years. But these days he's using a Tak Epsilon...


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sami2012
journeyman


Reged: 03/10/12

Re: What do you recommend 8 inch or 10 inch Newtonian new [Re: SeattleScott]
      #6089415 - 09/19/13 06:30 AM

what do you think about Ritchey-Chretien or Newtonian?????

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mpgxsvcd
Carpal Tunnel


Reged: 12/21/11

Loc: Raleigh, North Carolina
Re: What do you recommend 8 inch or 10 inch Newtonian new [Re: sami2012]
      #6089733 - 09/19/13 11:05 AM

I think the RCs are very nice scopes. However, they are about double what the equivalent Newtonian costs. If my budget allowed it I would have an RC. Since it doesn’t I have a Newt and I am not too upset about that.

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orlyandico
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Re: What do you recommend 8 inch or 10 inch Newtonian new [Re: mpgxsvcd]
      #6089757 - 09/19/13 11:18 AM

The RC's are f/8 to f/9. So long focal length and slow focal ratio requiring a better mount and longer exposure times. For this reason a newtonian in my opinion is a more friendly option.

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Zad
super member


Reged: 01/05/08

Re: What do you recommend 8 inch or 10 inch Newtonian new [Re: orlyandico]
      #6090081 - 09/19/13 02:32 PM

I run the Orion version of the AT8IN on an Orion Atlas EQ-G mount, and have no issues with the mount handling the scope, a DSLR with Coma Corrector, and a 50mm finder with the SSAG for autogiding. The oversized secondary fully illuminates the APS-C sized chip in my Canon 450D. A 10" may be pushing things a bit, but I have never tried to image with that big a payload. Imaging at f/4 makes for short subs, which I love. I get more data per imaging session. The Orion version of this scope has a plate that reinforces the focuser, and you can collimate the focuser. I get nice round stars from edge to edge.

As far as collimating the scope goes, it isn't any harder than any other Newt to collimate, just slightly more important. I think this issue gets a little overblown. I think this comes more into play for visual work. For visual, if you are using an f/5 newt, you don't have to be exactly spot-on, but at f/4 it becomes more important. But anytime I image, I want to be spot-on regardless if I am f/5 or f/4, so there was really no change for me going from f/5 to f/4 as far as collimation goes.


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B. Cook
professor emeritus
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Reged: 10/18/10

Loc: No. California
Re: What do you recommend 8 inch or 10 inch Newtonian new [Re: Zad]
      #6090117 - 09/19/13 02:55 PM

I have the Orion Atlas mount. I had a 10in newt on it. It was fine till any breeze at all came up and then forget it. You could not stop the vibration from the wind. Its gone!!

Bill


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Zad
super member


Reged: 01/05/08

Re: What do you recommend 8 inch or 10 inch Newtonian new [Re: Zad]
      #6090123 - 09/19/13 02:58 PM

The question regarding RC vs. Newt is a seperate issue. Assuming the OP would be looking at an 8" scope either way, you are talking about 1600mm f.l. @ f/8 for the RC vs. 800mm f.l. @ f/4 as one possible example.

1. The RC would require subs that are 4 times longer to get the same level of exposure than the Newt.

2. The image scale would be different for the two scopes with the RC being better suited for smaller targets. I think galaxies and planetary nebula, whereas the Newt can handle larger objects.

3. Matching the focal length to the pixel size comes into play here as well. The RC matches better with cameras with bigger pixels, and the Newt mathces better with smaller. I usually want about 1-2 arc.sec./pixel.

4. The newt is a little trickier to balance the scope with due to the focuser sticking out of the side of the tube rather than the back. I turn the scope in the rings so the focuser is pointing down towards the mount to help with balance.

5. The Newt definately needs a coma corrector for nice round stars in the corners of the image. I use the MPCC with great results. The RC benifits from a field flattener from what I understand, but I have no experience in this area. The Newt has a nice flat field already, so no field flattener is necessary.

6. The RC would require more accurate tracking due to the longer focal length and longer exposures.

So, it really comes down to what kind of targets the OP is interested in, what kind of camera (and pixel size) will the OP use, and how much effort does the OP want to put into accurate tracking (will the OP be autoguiding, manual guiding, unguided).

Either scope would work very well, just a matter of preference.


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gdd
scholastic sledgehammer


Reged: 11/23/05

Loc: N Seattle suburb, WA
Re: What do you recommend 8 inch or 10 inch Newtonian new [Re: Zad]
      #6090190 - 09/19/13 03:46 PM

You can use a reducer on the RC to get you down to f/5.6, the CCDT67 is a popular choice.

Or you can use a barlow on the Newt to get you up to F/8 for galaxies, though I have not heard of people doing so.


Gale


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Kendahl
member


Reged: 02/02/13

Re: What do you recommend 8 inch or 10 inch Newtonian new [Re: gdd]
      #6090554 - 09/19/13 07:39 PM

Have you considered the Vixen R200SS? It's an 8 inch f/4 Newtonian. Because it is made of aluminum, the bare tube weighs only 11.7 pounds. That means you can get away with a mount suitable for a 4 inch refractor.

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orlyandico
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Reged: 08/10/09

Loc: Singapore
Re: What do you recommend 8 inch or 10 inch Newtonian new [Re: Kendahl]
      #6090717 - 09/19/13 10:05 PM

Gale,

Now that I'm waiting for my AT8IN, I am slightly concerned about losing long focal length for those pesky little PNs.

While I wish a barlow would work, since I have a 2" lying around, I suspect it doesn't. Otherwise ASA wouldn't be selling this super-pricey 1.8X barlow corrector -

http://www.optcorp.com/asa-2inch-1-8x-barlow-corrector-2korrb.html

(I already have the 0.73X reducer, which I thought was pretty expensive, but the barlow corrector costs nearly double!)

I guess the bottom line is you really have to keep a separate OTA around for those tiny planetaries.

As for the R200SS - yes it's a nice f/4 newtonian, but it is rather expensive ($1500+) compared to the Orion, Astro-Tech, etc. versions.


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gdd
scholastic sledgehammer


Reged: 11/23/05

Loc: N Seattle suburb, WA
Re: What do you recommend 8 inch or 10 inch Newtonian new [Re: orlyandico]
      #6090975 - 09/20/13 01:23 AM

I did find a case where a person used a cheaper barlow with a at8in and was satisfied with results for m51. Maybe not quite as good as the ASA, but worth trying since you already have one.

Gale


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Zad
super member


Reged: 01/05/08

Re: What do you recommend 8 inch or 10 inch Newtonian new [Re: gdd]
      #6091825 - 09/20/13 01:35 PM

I have been wanting to try out a 1.5x 2" barlow that I have on my Orion 8" f/3.9 Newt, but I haven't gotten around to it. My main concern is CA, since it was not designed for AP, and it was relatively inexpensive.

But I have been wanting to pick up a 2" 2x Televue Powermate because I think that would work well, but funds are tight right now. Has anyone tried one of these on a newt for imaging?


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orlyandico
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Loc: Singapore
Re: What do you recommend 8 inch or 10 inch Newtonian new [Re: Zad]
      #6091918 - 09/20/13 02:31 PM

not sure if CA is an issue. The usual refractor flatteners are just achromatic doublets.

The CA becomes much less of an issue closer to the focal plane.


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csrlice12
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Re: What do you recommend 8 inch or 10 inch Newtonian new [Re: orlyandico]
      #6091947 - 09/20/13 02:53 PM

It's a newt, newt's shouldn't have CA....that's a refractor abberation....newts have coma instead......

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Zad
super member


Reged: 01/05/08

Re: What do you recommend 8 inch or 10 inch Newtonian new [Re: csrlice12]
      #6091980 - 09/20/13 03:23 PM

Barlows can produce CA. In fact some barlows are advertiezed as "ED" or "Apochromatic". Astro Tech has a " 2X achromatic Barlow" AND a "2X apochromatic ED Barlow" on their site right now.

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Zad
super member


Reged: 01/05/08

Re: What do you recommend 8 inch or 10 inch Newtonian new [Re: Zad]
      #6091989 - 09/20/13 03:25 PM

Flateners usually decrease the scopes focal length or are neutral, but barlows increase the focal length (by a factor of 2x or more most often). So CA is more prevelent in a barlow.

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bandazar
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Reged: 10/19/05

Re: What do you recommend 8 inch or 10 inch Newtonian new [Re: Zad]
      #6092224 - 09/20/13 05:56 PM

If I was really into deep sky, my personal favorite apertures would be 5" and 14". I wouldn't necessarily compare 2 adjoining apertures if I had the chance to go to a star party and see what a telescope of a specific aperture can do for me.
14" because I really enjoy m13, and it is probably the largest "easily" transportable scope. And 5" as the quick look scope (I'd actually stick with a cass in this range though, or maybe a good wide field refactor).


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Kendahl
member


Reged: 02/02/13

Re: What do you recommend 8 inch or 10 inch Newtonian new [Re: orlyandico]
      #6097768 - 09/24/13 01:07 AM

Quote:

Otherwise ASA wouldn't be selling this super-pricey 1.8X barlow corrector



$1,500. Ouch! That makes the Feather Touch with the integrated Paracorr a bargain at $860.


Quote:

As for the R200SS, ......it is rather expensive ($1500+) compared to the Orion, Astro-Tech, etc. versions.



Several months ago, I questioned the price difference between the Vixen and the others. A guy familiar with both replied that the Vixen was significantly better.


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orlyandico
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Re: What do you recommend 8 inch or 10 inch Newtonian new [Re: Kendahl]
      #6098075 - 09/24/13 09:40 AM

Kendahl, the $1,500 barlow corrector is a tele-extender.

ASA also makes a reducer/coma corrector for about $1,000 - I think it's harder to make a good extender than a reducer.


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andysea
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Reged: 09/03/10

Loc: Seattle, WA
Re: What do you recommend 8 inch or 10 inch Newtonian new [Re: orlyandico]
      #6099650 - 09/25/13 12:54 AM

Fast scopes are obviously the best for AP. However people seem to forget how difficult it is to get perfect focus on an f/4 system. The CFZ in the blue wavelength at F/4 is 37microns.
I think it would be pretty hard to nail perfect focus by focusing manually. I found a focus mask only useful to get in the ballpark.


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Zad
super member


Reged: 01/05/08

Re: What do you recommend 8 inch or 10 inch Newtonian new [Re: andysea]
      #6102134 - 09/26/13 11:15 AM

I use a focus mask on my 8" f/4 with LiveView on my DSLR, and have never had any trouble reaching foucus. Takes all of 30 seconds.

Here is a sample:

www.astrophotogallery.org/showfull.php?photo=10324

Edited by Zad (09/26/13 11:19 AM)


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andysea
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Reged: 09/03/10

Loc: Seattle, WA
Re: What do you recommend 8 inch or 10 inch Newtonian new [Re: Zad]
      #6102422 - 09/26/13 01:58 PM

Interesting. I haven't had much luck with the focus mask. I use it to get close enough but then I let the Sequence Generator Pro take over and dial in on perfect focus for the entire frame. I refocus every 1c of temp shift.
I feel that the focus mask leaves too much guesswork to the user. This is probably not a huge issue with slower systems. F/4 is however pretty fast.
That's just my experience tho.

Andy


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Zad
super member


Reged: 01/05/08

Re: What do you recommend 8 inch or 10 inch Newtonian new [Re: andysea]
      #6102512 - 09/26/13 03:00 PM

Using the Live View feature of my Canon 450D has increased the accuracy of my focus a great deal (not to mention the process is a great deal faster). So, I don't really have any issues finding a great focus, but f/4 is more sensitive to temperature changes then a slower scope in theory. So far, I haven't really run into too much temperature change issues so far as far as focus goes.

My issue is where I live (mid-atlantic) there are not very many good nights for imaging. So, I have chosen to go with one shot color camera, and a fast scope (to get as much data as I can on the rare good nights). For most targets so far, I have only needed about 3min. subs max. So in about 1 hour and 15 minutes, I can get 25 subs. The temperature usually doen't change that much for me in that time period, so I just take my darks and move on. I really need to do an experiment to see how much each degree of temperature change effects my focus. So far, I really haven't noticed much. But with f/4 I don't have to take subs for very long. Once I start imaging dimmer objects, I may run into this issue more. But I will cross that bridge when I get to it.


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nighthound
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Re: What do you recommend 8 inch or 10 inch Newtonian new [Re: Zad]
      #6102616 - 09/26/13 04:19 PM

I use the Vixen R200SS, it's very light and a good match for my Losmandy G-11. I added a low profile Moonlite focuser to the Vixen, makes fine focus no problem. I would recommend a high quality collimation kit. I use the Cat's Eye Infinity XL system, very accurate. Once you get the hang of them you can make minor tweaks quickly, even in the dark.

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andysea
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Reged: 09/03/10

Loc: Seattle, WA
Re: What do you recommend 8 inch or 10 inch Newtonian new [Re: nighthound]
      #6104297 - 09/27/13 01:52 PM

Steve
I've been thinking about taking a plunge back to the dark side of reflectors for a while and the VIxen R200SS looks like a great candidate.
Do you think that the stock focuser with a robofocus would be adequate for AP? Does it have a threaded draw tube? I want all threaded connections.
Thanks
Andy


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nighthound
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Re: What do you recommend 8 inch or 10 inch Newtonian new [Re: andysea]
      #6109497 - 09/30/13 03:45 PM

Andy, to be honest I removed the stock focuser so many years(5-6) ago I forgot the build type. I do remember it being high profile and that was a problem for acquiring focus with a DSLR. It also felt a bit crude in movement for my taste. The Moonlite fixed that and with the dual focus adjustment, fine focus is very easy. Sorry I can't give you a more definitive answer on your robofocus matchup, if you already have it there's no harm in trying it to see how it works out provided the stock focuser's higher profile isn't an issue. There may be a more refined stock focuser on the new R200SS, not sure.

Here's what mine looks like:
http://i3.photobucket.com/albums/y67/Nighthd/Astrophotography/Astro%20Equipme...
http://i3.photobucket.com/albums/y67/Nighthd/Astrophotography/Astro%20Equipme...


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andysea
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Loc: Seattle, WA
Re: What do you recommend 8 inch or 10 inch Newtonian new [Re: nighthound]
      #6110065 - 09/30/13 09:24 PM

Thank you so much Steve! The photos really help.That is a beautiful telescope.
One more question. What is the drawtube length of the focuser?
Thanks
Andy


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nighthound
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Re: What do you recommend 8 inch or 10 inch Newtonian new [Re: andysea]
      #6110173 - 09/30/13 10:19 PM

You're welcome Andy. I have the 2 inch travel with the three screw, brass compression ring and 1.25 inch eyepiece adapter. The 2 inch travel tube has a physical length of about 3 3/8 inches total. The area at the top where the three compression screws is 3/8 of that. Mine has the Dual Rate Tri-knob adjustment with Shaft Lock. Shaft lock is great to prevent focus shift from camera weight. See link below to read more (scroll down):

http://www.focuser.com/cgi-bin/dman.cgi?page=productdetail&plugin=dstore....

Steve


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andysea
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Loc: Seattle, WA
Re: What do you recommend 8 inch or 10 inch Newtonian new [Re: nighthound]
      #6110252 - 09/30/13 10:54 PM

Awesome thanks again Steve. I am familiar with the moonlite focusers. I used to own a 10"RC with the moonlite on it and it had the shaft lock, it was definitely rock solid.

Andy


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orlyandico
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Reged: 08/10/09

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Re: What do you recommend 8 inch or 10 inch Newtonian new [Re: andysea]
      #6110377 - 09/30/13 11:53 PM

I just had the AT8IN out a couple times with the ASA reducer. Collimation is a pig. The AT8 definitely needs reinforcement of the tube under the focuser.

So far I'm using the stock focuser and manually focusing. I'm only getting 4" stars. My pixel scale is 2.68". But then I have to image through haze and clouds.

As an aside, the 8" is the most I want to manhandle. It takes 2 x 9 lb and 1 x 6 lb counterweights to balance on the Mach1.


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andysea
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Re: What do you recommend 8 inch or 10 inch Newtonian new [Re: orlyandico]
      #6110463 - 10/01/13 01:12 AM

I think the Vixen r200ss is lighter than the At8in. Another option would be the Officina Stellare 200mm RH but the price point is way higher.

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orlyandico
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Re: What do you recommend 8 inch or 10 inch Newtonian new [Re: andysea]
      #6110543 - 10/01/13 03:18 AM

Yup the RH seems to be the Ferrari in this range... Too rich for my blood.

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Zad
super member


Reged: 01/05/08

Re: What do you recommend 8 inch or 10 inch Newtonian new [Re: orlyandico]
      #6111145 - 10/01/13 12:36 PM

Quote:

I just had the AT8IN out a couple times with the ASA reducer. Collimation is a pig. The AT8 definitely needs reinforcement of the tube under the focuser.

So far I'm using the stock focuser and manually focusing. I'm only getting 4" stars. My pixel scale is 2.68". But then I have to image through haze and clouds.

As an aside, the 8" is the most I want to manhandle. It takes 2 x 9 lb and 1 x 6 lb counterweights to balance on the Mach1.




Orion updated their version of this scope (it is now listed as an f/3.9, and the older version was listed as f/4) to include a steel reinforcement plate under the focuser. I got mine right after the update (thankfully), and I haven't had any issues with the focuser sagging. I use a 450D and an MPCC. I am not sure how much more the focuser can handle because I haven't tried. Perhaps others can chime inn...


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mpgxsvcd
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Re: What do you recommend 8 inch or 10 inch Newtonian new [Re: orlyandico]
      #6111164 - 10/01/13 12:54 PM

Quote:

well of course collimation of the f/4 will be harder. but it's almost 1 stop faster for photography (1.56X so a 10-minute sub on the f/4 would be equivalent to a 16-minute sub on the f/5). Both will need a coma corrector for astrophotography.




The procedure for collimating an F5.0 scope is identical to that of an F4.0 scope. So why would one be any harder?


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mpgxsvcd
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Re: What do you recommend 8 inch or 10 inch Newtonian new [Re: csrlice12]
      #6111195 - 10/01/13 01:10 PM

Quote:

Yea, but you've been at this awhile....Be truthful now, would you really recommend a 10" newt for AP to a person with no astronomy or photography experience?????? Now, if I already had some experience and was looking to "upgrade"....




Absolutely I would recommend a Newt on a CG-5 even as a beginner scope as long as the person can lift the Newt up onto the mount. For most Newts that is 15-30 pounds. The weight may be an issue for some. However, a decent refractor or SCT still weighs more than some people want to lift. If you can pick up 30 pounds to chest level I would say that there is no reason not to get a Newt.

I started with an 8 inch Newt on my CG-5 and it couldn't be simpler with the cameras that I have.


The Fast Newts just make aligning and centering so much easier with the right cameras. That is the biggest frustration for most beginners. The collimation concerns are simply a myth. It is easy to do with a laser collimator. It takes about 1.5 minutes with some Bob's Knobs.

I think too many people have become afraid of Newts too actually find out if they work or not. Each type of scope has its benefits and drawbacks. However, if you want to do anything but widefield, you don't want to spend a lot of money, and you want good fast results you are going to end up with a Newt.

Pretty much every beginner is looking for exactly that.


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Zad
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Re: What do you recommend 8 inch or 10 inch Newtonian new [Re: mpgxsvcd]
      #6111235 - 10/01/13 01:37 PM

Quote:

Absolutely I would recommend a Newt on a CG-5 even as a beginner scope as long as the person can lift the Newt up onto the mount. For most Newts that is 15-30 pounds. The weight may be an issue for some. However, a decent refractor or SCT still weighs more than some people want to lift. If you can pick up 30 pounds to chest level I would say that there is no reason not to get a Newt.

I started with an 8 inch Newt on my CG-5 and it couldn't be simpler with the cameras that I have.


The Fast Newts just make aligning and centering so much easier with the right cameras. That is the biggest frustration for most beginners. The collimation concerns are simply a myth. It is easy to do with a laser collimator. It takes about 1.5 minutes with some Bob's Knobs.

I think too many people have become afraid of Newts too actually find out if they work or not. Each type of scope has its benefits and drawbacks. However, if you want to do anything but widefield, you don't want to spend a lot of money, and you want good fast results you are going to end up with a Newt.

Pretty much every beginner is looking for exactly that.




I agree that there seems to be a lot of misconception about a fast Newt for imaging in regards to collimation. I think they got this reputation from the visual world. If you are not spot-on with a slow Newt, it's not a big deal as far as visual goes, but as you get faster, you want to be spot-on. But if you are imaging, you are going to want spot-on no matter what. So for me, it makes no difference at all. In fact, it is easier for me to collimate my 8" f/3.9 than my 10" f/4.9 because of the shorter focal length. I use a cheshire with a built in sight tube. The 10" f/4.9 has a 1200mm focal length, so the mark on the mirror appears very tiny, and I have to stop looking through the collimator to adjust the primary becuase I can't reach while looking. But on my 8" f/3.9, the spot appears bigger in the collimator, and I can reach all adjustment knobs while looking through the collimator simultaneously. Never takes more than a minute or two to achieve pretty darn perfect collimation. I am thinking of upgrading to a more fancy schmancy laser, but if it aint broke....


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orlyandico
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Re: What do you recommend 8 inch or 10 inch Newtonian new [Re: Zad]
      #6111408 - 10/01/13 03:07 PM

Well..........

I've been playing with the AT8IN for the past few nights. And tonight after looking at my streaked stars I decided to mount the AT90EDT again.

Man it's much easier to use. The focuser is great, you can live without a Feathertouch with the AT90's stock focuser. The stars are round and small. No irregular shapes from mis-collimation. No changing star shapes from different scope positions (I think my focuser still sags in spite of the reinforcing plate I put in).

I almost considered giving up on the AT8IN.. but that f/3.0 is too tempting. It's like a GM truck. It catches light very fast, but is rough around the edges.

I hope the stars will get round when I get my laser collimator. Or I'll lose all my hair.


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andysea
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Re: What do you recommend 8 inch or 10 inch Newtonian new [Re: orlyandico]
      #6111567 - 10/01/13 04:54 PM

I wonder if the carbon fiber tube version would work better.

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orlyandico
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Re: What do you recommend 8 inch or 10 inch Newtonian new [Re: andysea]
      #6111818 - 10/01/13 07:31 PM

I have no idea... there are a lot of things that can stand improvement on the AT8IN.. the tube that flexes is one.. a better focuser.. better mirror support. Well it is a $500 tube. Even the AT90EDT from the same company (which is almost 3 stops slower) costs nearly 3 times more.

A friend characterizes the AT8IN as having "lots of potential." I guess when looked at that way...


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Zad
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Reged: 01/05/08

Re: What do you recommend 8 inch or 10 inch Newtonian new [Re: orlyandico]
      #6112650 - 10/02/13 09:05 AM

I was hoping that AT would update this scope after Orion updated their version to address these shortcomings. I think a few tweeks from the factory is all it needs. The Orion version has the reinforcement plate, and a collimitable focuser. Plus it's a little lighter as well (less tube in front of the focuser, which may help reinforce the focuser as well).

Have you tried sliding the tube rings closer to the focuser (and sliding the plate in the saddle the opposite way to maintain balance)? That may help reinforce the tube near the focuser. I am also wondering if you can tighten the friction in the focuser. Perhaps the focuser drawtube itself is flexing.


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orlyandico
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Re: What do you recommend 8 inch or 10 inch Newtonian new [Re: Zad]
      #6113439 - 10/02/13 04:01 PM

Yup I've got the tube ring right next to the focuser.. didn't know the Orion version had a collimatable focuser. That's a good feature. My friend convinced me the AT was a better choice with the longer tube and baffles.

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Zad
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Re: What do you recommend 8 inch or 10 inch Newtonian new [Re: orlyandico]
      #6113466 - 10/02/13 04:17 PM

I suspect that when they designed these scopes, they didn't consider how extending the tube past the focuser would effect the focusers strenght. The fact that the Orion version has a shorter extention and a reinforcement plate would probably explain why I am not getting the same issue you are.

I am very lucky that I got the one I did. I was ready to buy, and then had to postpone for a bit. In that time, Orion came out with their updated version. In fact, the update was the reason I purchased the Orion over the AT.

But at least you have a very nice refractor to image with while you get the other issues sorted out. I hope it works out for you, because I have enjoyed using my reflector a great deal, and I am pleased with the results. I would love to get a premium refractor one day for imaging, but the budget is tight these days. I am just going to enjoy what I have.


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andysea
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Re: What do you recommend 8 inch or 10 inch Newtonian new [Re: Zad]
      #6113539 - 10/02/13 04:45 PM

That's great info you guys, thanks!
I thought that the AT8in was better because the tube acted more like a dewshield but now i can see that the possible drawbacks.


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