Jump to content

Stargazers Lounge Uses Cookies

Like most websites, SGL uses cookies in order to deliver a secure, personalised service, to provide social media functions and to analyse our traffic. Continued use of SGL indicates your acceptance of our cookie policy.

stargazine_ep3_banner.thumb.jpg.5533fb830ae914798f4dbbdd2c8a5853.jpg

Yoddha

Meade ACF 10" f/8 vs RC 10"

Recommended Posts

Posted (edited)

Hello,

I want to make an upgrade in the next half year or so and for some time am reading opinions in the net, however can't get clear direction and will be very thankful to hear your opinions :)

Here is the background. I'm pure imager (once or twice per year am making short visual walkthrough for friends that has no experience at all). The setup which am building is permanent located in a small obsy - a 2.2m Uniwesal dome (don't mess with them unless you like big troubles). The mount is CEM60 and my primary camera is QHY22 with set of Astrodon filters - 3nm narrowband and LRGB. For many years am a refractor guy 😜 In a parallel world where money are not a factor would like something like 180mm of that kind and bigger dome, but I am here and now... It is not possible to house/afford something bigger than 150mm which is not significant step over the 130mm I have... So am looking for alternatives :)

There are two options that tear me apart and still can't find stable direction:

1. GSO clone RC 10" f/8 truss tube, detached focuser, with reducer that will make it ~ f/5.4
2. Meade ACF 10 f/8, possibly additional focuser, with reducer that will make it ~f/5.4

Both will be used with OAG. The collimation should not be a big issue - it is permeant setup and in worst case will require tuning once-twice per year... Am I right?

My research started and continues with real images hunt in Astrobin (in addition to reading everything that can find in the forums). There are some spectacular images taken with both scopes! 

My considerations so far are: 
The RC pros with truss version - the cooling will be faster because the open design and fans, the temperature shift should be smaller. The cons are bit bigger stars, spikes.
The ACF pros are the smaller obstruction, bit smaller stars and no spikes. The cons are slower cooling, bigger temperature shift, mirror flips ??? May need additional focuser, bit bigger price.

In long term I want to use the scope for astrophotography for smaller targets. In very long term if one day I find myself tired of astrophotography 😲  am thinking for supernovas search or variable stars photometry...

As I started will be very thankful to hear your opinions for those two models, for the links that I have missed, as well as the points and considerations I don't see or know    🙏🙇‍♂️🙇‍♂️🙇‍♂️

P.S. I have excluded the RASA models because are not compatible with the filters I have and because they require manual filter change. Fast Newtonians are excluded because are also too fast for Astrodon and because it is hard to put Corrector + OAG + Filter wheel.

Edited by Yoddha

Share this post


Link to post
Share on other sites
Posted (edited)

I was looking at these scopes myself TBH as an upgrade in the not too distant future , but in the 12/14 range .. so I suppose any comments would be applicable. 
 

I have read some interesting comments on Cloudy Nights .. regarding similar  scopes .. https://www.cloudynights.com/topic/595503-gso-vs-tso-for-ritchey-chretien-telescopes/

one thing that I have had experience with is a CT8 Newtonian.( open mirror ) .  I noticed the primary mirror became dirty quite quickly and from what I have read it doesn’t make that much difference, but as an imager I want the best possible image being projected from that mirror , so I ended up removing and cleaning the mirror a couple of times , which then meant collimating the scope , which isn’t a bad thing I suppose , but a bit more difficult on a Ritchey Chretien . So I have read ! . and much easier to clean the front glass on a Smit . 
 

will be interesting to read what others think ..  🤔

 

 

Edited by Brian28

Share this post


Link to post
Share on other sites
Posted (edited)

Purely on the collimating front, I have a Meade 10" LX200R that has only been collimated once in all the years I've had it an even then didn't really need doing and only took minutes, there have been tales of woe from members here and elsewhere of spending hours trying to collimate their RCs,  but I have no personal experience of this.

I have the Meade electronic microfocuser which has always worked perfectly with heavy cameras and filter wheels although as usual other folk have had problems with them.

Dave

Edited by Davey-T

Share this post


Link to post
Share on other sites

I would go for all mirror design. In fact I have 8" RC and I'm happy with it.

Collimation is not such a big issue (at least it was not for me). I collimated my scope in about 10-15 minutes. It was made easy by use of CMOS camera - my imaging camera is CMOS and has fast download times, in fact you can have live image on computer from it (high fps, fast download). This and software that has focusing aid - star FWHM measurement was all it took for quick collimation.

I'm not sure why you say that RC has larger stars. There will be spikes, but I don't think it will produce larger stars.

Share this post


Link to post
Share on other sites
1 hour ago, vlaiv said:

I would go for all mirror design. In fact I have 8" RC and I'm happy with it.

Collimation is not such a big issue (at least it was not for me). I collimated my scope in about 10-15 minutes. It was made easy by use of CMOS camera - my imaging camera is CMOS and has fast download times, in fact you can have live image on computer from it (high fps, fast download). This and software that has focusing aid - star FWHM measurement was all it took for quick collimation.

I'm not sure why you say that RC has larger stars. There will be spikes, but I don't think it will produce larger stars.

Hi Vlaiv , how do you find the cleanliness of the mirror on the RC ? 

Share this post


Link to post
Share on other sites
6 minutes ago, Brian28 said:

Hi Vlaiv , how do you find the cleanliness of the mirror on the RC ? 

Mine is regular tube, not truss tube, being 8" version, and I pretty much don't pay attention to mirrors at all (give them occasional look but about the same as with my newtonian - once in couple of months). Have both scopes for a few years now and it never occurred to me that I should clean my mirrors.

Don't worry about mirrors being dirty. That dust is so out of focus that only difference it can make is a bit of dimming at the focal point.

It is usually less than 0.1% of 0.1% or something like that - in fact, in order for light loss to be 1% you need something like black stain 1cm x 3cm somewhere on the mirror for 8" scope, and even that can be compensated with couple more minutes of imaging - so for imaging purposes, you just don't need to worry about dust/dirt (unless of course it is severe). In fact, even for visual, you really should not worry about dirt on mirror (again, unless severe).

Here is point where I would consider cleaning my mirrors:

image.png.62cf3da3779e5c3e4094793cf25be5d7.png

Btw, cleaning mirrors - not very complicated and while you have to be careful of how you handle mirrors - it is half an hour job at max (I cleaned mirrors on my previous newtonian - although they were nowhere near dirty as above image - but at the time I also wanted my mirrors to be "always clear" :D )

 

  • Like 1
  • Haha 1

Share this post


Link to post
Share on other sites

The Meade might prove to be far easier to set up. Some people get the GSOs into good working trim but some struggle for ever and a day. It's worth noting that, a few years ago, several suppliers were working on re-engineered scopes using GSO optics but these have, it seems, gone rather quiet of late. Maybe it wasn't as simple as it seems to get these instruments working well. There's also the Celestron Edge series to consider.

Personally I've concluded that I can work close to the limits of the seeing with a FL of a metre from a 140mm refractor. The 14 inch I used to use could out-resolve it very slightly on a good night, maybe, but refractor simplicity is such a bonus. Since pixels are getting ever smaller I wonder if I'll ever really want more focal length than I now have. Some examples of 0.9"PP from a 140 F7:

spacer.png

spacer.png

Olly

  • Thanks 1

Share this post


Link to post
Share on other sites

The discussion is getting very interesting! :)

The RC8 are very good scopes and all images with them are very good. However the 8" are too close to 130mm APO. What bothers me is that the images quality between RC8 and RC10 in majority is in favor of RC8 which makes me think that maybe 10" are too hard to be made with higher quality at this price tag??? 

Olly, your images shows exactly why I'm a refractor fan :) I see that you have 10" ACF in the signature. Did you try to image with it or it is only for visual use?

  • Like 1

Share this post


Link to post
Share on other sites

I'd say refractor > reflector any day, but the higher focal length makes smaller targets possible for my mount. 

I see you have a CEM60 - I have one too, AND I own a 10" ACF. One advice: consider the C11 Edge!! I upgraded from the Meade and never looked back. The Meade is now used for visual only so I don't have to change the back all too often. 

The 10" ACF is possible on the CEM, but the C11 is lighter. 

Share this post


Link to post
Share on other sites

Hi Wiu-Wiu,

The Meade is on focus because it has f/8 version which can be speeded to under f/6... Is C11 outperforms 10" ACF significantly or the advantage is based on the aperture and weight?

Share this post


Link to post
Share on other sites
Posted (edited)

I'd say they are optically quite similar. I haven't gotten the chance yet to compare pictures of the same object. 

 

ACF: (crop)

ngc891-330min-acf-oag-2.jpg

 

C11:

m82-2019dec30-40x60-ddl-c11edge.jpg

 

Both on the CEM60.

 

I think the weight issue is the real factor in this equasion. The Edge is just flying, while the ACF 'hangs' on the mount. 

 

 

 

Edited by Wiu-Wiu

Share this post


Link to post
Share on other sites

The price tag of C11 EdgeHD+Corrector is our of my desired budget... CEM60 will have to work harder 😄

  • Haha 1

Share this post


Link to post
Share on other sites

you mean reducer? Yeah, that one costs an arm and a leg. I don't have it, the CEM handles it well at 2800mm ;) 

Share this post


Link to post
Share on other sites

Yes, I mean reducer :) Definitely I want to make the scope near to f/5 in order to gather more light faster :)

Share this post


Link to post
Share on other sites
2 hours ago, ollypenrice said:

Since pixels are getting ever smaller I wonder if I'll ever really want more focal length than I now have.

Fact of life is that focal length and aperture are tied together in a "mysterious relationship" often called F/ratio - some say even that it is a mythical thing :D.

In any case - larger focal length - larger the aperture and hence light gathering of telescope. You don't necessarily have to go with higher sampling rate as well - as long as you have big enough sensor and you can bin - there is real benefit of using large scope.

I would rather image with 12" at 0.9"pp than 5.5" at 0.9"pp. In fact my dream setup is in fact 20" in form of 4x10" :D

 

Share this post


Link to post
Share on other sites

Then there is also the Edge HD9.25 for which Celestron now also produce a reducer at a quite reasonable price.

  • Like 1

Share this post


Link to post
Share on other sites
17 minutes ago, vlaiv said:

 

I would rather image with 12" at 0.9"pp than 5.5" at 0.9"pp. In fact my dream setup is in fact 20" in form of 4x10" :D

 

So would I if all things were equal and reflectors 'just worked' like refractors... But, and this is a big 'but.....'

😄lly

  • Like 1

Share this post


Link to post
Share on other sites

Olly, I see that you have 10" ACF in the signature. Did you try to image with it or it is only for visual use?

Share this post


Link to post
Share on other sites
On 07/01/2020 at 16:03, Yoddha said:

Yes, I mean reducer :) Definitely I want to make the scope near to f/5 in order to gather more light faster :)

You won't gather more light with a reducer. You'll just put the same number of object photons onto fewer pixels and widen the field of view. If that's what you want to do then fine, but you won't gather more light.

Olly

Share this post


Link to post
Share on other sites

Absolutely agree! It can be described better what speeding a scope does 👍👌

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

  • Recently Browsing   0 members

    No registered users viewing this page.

×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.